Sickle Cell Disease (SCD) Treatment & Management

The National Institutes of Health advises that optimal care for patients with sickle cell disease (SCD), including preventive care, is best achieved through treatment in clinics that specialize in the care of SCD. All patients with SCD should have a principal health care provider, who should either be a hematologist or be in frequent consultation with one. ^[53]

For sickle cell crisis, when the severity of the episode is assessable, self-treatment at home with bed rest, oral analgesia, and hydration is possible. Individuals with SCD often present to the emergency department (ED) after self-treatment fails.

Do not underestimate the patient's pain. United States and United Kingdom guidelines emphasize the need for prompt initiation of analgesia (eg, within 30 minutes of triage)  and rapid initiation of parenteral opioids for patients in severe pain. ^{[45, 49]} Early achievement of maximum analgesia has been shown to shorten hospital stays in pediatric patients with pain from SCD. ^[54]

If patients with SCD crisis are being transported by emergency medical services (EMS), they should receive supplemental oxygen and intravenous hydration en route to the hospital. Some areas have specialized facilities that offer emergency care of acute pain associated with SCD; many EDs have a standardized treatment plan in place. National Heart, Lung, and Blood Institute guidelines recommend using an individualized pain management plan (written by the patient’s SCD provider) or an SCD-specific plan whenever possible. ^[49]

Pain management should include four stages: assessment, treatment, reassessment, and adjustment. While considering the severity of pain and the patient's past response, follow consistent protocols to relieve the patient's pain.

The goals of treatment are symptom control and management of disease complications. Treatment strategies include the following seven goals:

• Management of vaso-occlusive crisis
• Management of chronic pain syndromes
• Management of chronic hemolytic anemia
• Prevention and treatment of infections
• Management of the complications and the various organ damage syndromes associated with the disease
• Prevention of stroke
• Detection and treatment of pulmonary hypertension

An expert panel has released evidence-based guidelines for the treatment of SCD, including a strong recommendation that hydroxyurea and long-term, periodic blood transfusions should be used more often to treat patients. Other recommendations include the following ^[55] :

• Use of daily oral prophylactic penicillin up to age 5
• Annual transcranial Doppler examinations between the ages of 2 and 16 years in patients with sickle cell anemia
• Long-term transfusion therapy to prevent stroke in children with abnormal transcranial Doppler velocity (≥200 cm/s)
• In patients with sickle cell anemia, preoperative transfusion therapy should be used to increase hemoglobin levels to 10 g/dL
• Rapid initiation of opioids for the treatment of severe pain associated with a vasoocclusive crisis
• Use of analgesics and physical therapy for the treatment of avascular necrosis

In 2017, the US Food & Drug Administration (FDA) approved L-glutamine oral powder (Endari) for patients age 5 years and older to reduce severe complications of SCD. ^[56]  L-glutamine increases the proportion of the reduced form of nicotinamide adenine dinucleotides in sickle cell erythrocytes; this probably reduces oxidative stress, which contributes to the pathophysiology of SCD. ^[57]

Approval of L-glutamine was based on data from a randomized, placebo-controlled trial in which, over the course of 48 weeks, patients receiving L-glutamine had fewer hospital visits for pain crises that resulted in treatment with parenteral narcotics or ketorolac (median three vs four), fewer hospitalizations for sickle cell pain (median two vs three), and fewer days in hospital (median 6.5 vs 11). In addition, fewer patients taking L-glutamine had episodes of acute chest syndrome (8.6% vs 23.1%). ^[56]

Crizanlizumab, a P-selectin inhibitor, was approved by the FDA in 2019 to reduce the frequency of vaso-occlusive crisis (VOC) in adults with SCD. Binding P-selectin on the surface of activated endothelium and platelet cells blocks interactions between endothelial cells, platelets, red blood cells (RBCs), and leukocytes. Approval was based on the SUSTAIN clinical trial, in which crizanlizumab reduced the median annual rate of VOCs leading to health care visits by 45.3% compared with placebo (1.63 vs 2.98, P=0.010) in patients with or without hydroxyurea treatment. ^{[58, 59]}

Voxelotor was also approved by the FDA in 2019. It is indicated for treatment of SCD in adults and adolescents aged 12 years or older. Voxelotor is a hemoglobin S (HbS) polymerization inhibitor that binds to HbS with a 1:1 stoichiometry and exhibits preferential partitioning to RBCs. By increasing the affinity of Hb for oxygen, voxelotor demonstrates dose-dependent inhibition of HbS polymerization. Results showed 51% patients on the higher dose of voxelotor achieved a hemoglobin response compared with 6% with placebo. ^[60]

Allogeneic hematopoietic stem cell transplantation (HSCT) can cure SCD, but it has many risks, so the risk-to-benefit ratio must be assessed carefully. In addition, while HSCT from an HLA-matched sibling donor has a high success rate, especially in young recipients, only a minority of those with SCD have an HLA-matched sibling who does not have SCD, or a fully matched unrelated donor in the national pool. ^[61] Expansion of the donor pool to include partial-matched unrelated donors, half-matched (ie, haploidentical) donors, and partial-matched cord blood has ameliorated this shortage, however, and use of reduced-intensity or nonmyeloablative conditioning regimens in these cases has reduced the increased risk of graft-versus-host disease and graft failure otherwise seen with non–fully matched donors. ^{[61, 62]}

In December 2023, the FDA approved the first 2 gene-editing therapies for severe sickle cell disease in patients aged 12 years and older. One therapy, exagamglogene autotemcel (Casgevy), is the first to use the gene-editing tool CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats). The other, lovotibeglogene autotemcel (Lyfgenia), uses a different gene-editing tool called a lentiviral vector. 

Hydroxyurea has an established role as a safe and effective treatment for SCD. ^[63] Hydroxyurea increases total and fetal hemoglobin in children with SCD. ^[64] The increase in fetal hemoglobin retards gelation and sickling of RBCs. Hydroxyurea also reduces levels of circulating leukocytes, which decreases the adherence of neutrophils to the vascular endothelium (see image below.) In turn, these effects reduce the incidence of pain episodes ^[64] and acute chest syndrome episodes. ^[53]

Effects of therapy with hydroxyurea.

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In 2008, a National Institutes of Health Consensus Development Conference concluded that “strong evidence supports the efficacy of hydroxyurea in adults to decrease severe painful episodes, hospitalizations, number of blood transfusions, and the acute chest syndrome. Although the evidence for efficacy of hydroxyurea treatment for children is not as strong, the emerging data are encouraging.” ^[53]

In a meta-analysis of the literature through 2007, Strouse et al studied the efficacy, effectiveness, and toxicity of hydroxyurea in children with SCD and found that fetal hemoglobin levels increased from 5-10% to 15-20%; hemoglobin concentration increased modestly (approximately 1 g/L) but significantly; hospitalizations decreased by 56-87%; and the frequency of pain crisis decreased. ^[65]

A phase III multicenter international clinical trial in 38 children with SCD found that hydroxyurea treatment can lower elevated cerebral blood flow velocities, which have been linked to stroke risk. After a mean of 10.1 months, transcranial Doppler (TCD) ultrasound showed that mean velocity had decreased 15.5 cm/sec in patients receiving hydroxyurea but had increased 10.2 cm/sec in those receiving observation only (P=0.02). Post hoc analysis according to treatment received showed that after 15 months, conversion from conditional to abnormal cerebral blood flow velocities occurred in 50% of patients in the observation group but none of those in the hydroxyurea group. ^[66]  

In December 2017, the FDA approved Siklos (hydroxyurea) to reduce the frequency of painful crises and the need for blood transfusions in children 2 years of age and older and adolescents with sickle cell anemia who have recurrent moderate to severe painful crises. Siklos is the first hydroxyurea formulation to be FDA-approved for pediatric SCD. The approval was based on data from the ESCORT (European Sickle Cell Disease Cohort), an open-label single-arm trial that enrolled 405 pediatric patients with sickle cell disease from 2-18 years of age (274 children, ages 2-11 y; 108 adolescents, ages 12-16 y). The median change in fetal hemoglobin levels was 0.5 g/dL in 63 patients at 6 months and 0.7 g/dL in 83 patients at12 months after initiation of  treatment. After 12 months of treatment, the drug exhibited an ability to increase fetal hemoglobin in all patients, and decrease the percentage of patients who experienced at least on vaso-occlusive episode, one episode of acute chest syndrome, one hospitalization due to SCD, or one blood transfusion. ^[67]

Hydroxyurea is usually prescribed by a hematologist, using rigorous selection criteria. Indications for hydroxyurea include the following:

• Frequent painful episodes (six or more per year) ^[53]
• History of acute chest syndrome
• History of other severe vaso-occlusive events
• Severe symptomatic anemia
• Severe unremitting chronic pain that cannot be controlled with conservative measures
• History of stroke or a high risk for stroke

Patients receiving hydroxyurea require frequent blood testing and monitoring, with special attention to development of leukopenia and/or thrombocytopenia. A good continuous doctor-patient relationship and rapport must exist to ensure that potential toxicity is identified at its onset.

Hydroxyurea is a potentially leukemogenic and carcinogenic agent. Children studied by a cooperative group remained on hydroxyurea for more than a year with only minor adverse effects, but potential complications from long-term use are not yet known.

For patients who fail to respond to hydroxyurea, repeated transfusions for a limited period may be an option. Management of constant pain is extremely difficult, and expert advice should be obtained.

Blood transfusions are not needed for the usual anemia or episodes of pain associated with SCD. Urgent replacement of blood is often required for sudden, severe anemia due to acute splenic sequestration, parvovirus B19 infection, or hyperhemolytic crises. Transfusions are helpful in acute chest syndrome, perioperatively, and during pregnancy. Acute red cell exchange transfusion is indicated in the following situations:

• Acute infarctive stroke
• Severe acute chest syndrome
• Multiorgan failure syndromes
• Right upper quadrant syndrome
• Priapism that does not resolve after adequate hydration and analgesia

Regular blood transfusions are used for primary and secondary stroke prevention in children with SCD. See Stroke Prevention, below. In addition, Hilliard et al reported that in pediatric patients with frequent pain episodes despite being prescribed hydroxyurea, 1 year of red blood cell transfusion therapy significantly reduced the number of total emergency department visits for pain (6 vs 2.5 pain visits/year, P = 0.005), mean hospitalizations for pain (3.4 vs 0.9 pain admissions/year), and mean hospital days per year for pain crisis (23.5 vs 4.5, P = 0.0001). ^[68]

Transfusion-related complications include alloimmunization, infection, and iron overload. Treatment of iron overload is becoming easier with the new oral chelators.

Alloimmunization is a common problem that arises from the differences in certain minor red cell antigens found in the predominantly black patient population and the mostly white blood donors. Matching for C, E, Kell, JKB (Kidd), and Fya (Duffy) antigens can significantly reduce alloimmunization.

Transfusion and surgery

Intraoperative and postoperative complications may result from hypoxia, dehydration, or hypothermia that occurs during or after a surgical procedure. More complex procedures or longer duration of anesthesia times are more likely to lead to acute chest syndrome or other complications. Providing preoperative transfusion may decrease the risk.

Although one study demonstrated no overall difference in the complication rate among subjects who received either preoperative exchange or simple transfusion, it provided little guidance for what type of transfusion would be best in individual situations.

In general, raising the hemoglobin concentration to between 10 g/dL and 12 g/dL provides the patient with approximately 20-30% hemoglobin A. The presence of this fraction of normal hemoglobin may provide some protection from complications. Many anesthesiologists require a hemoglobin concentration of more than 10 g/dL prior to the procedure. ^[69]

When the patient’ baseline hemoglobin level is above 10 g/dL, the approach is less certain. If the complexity of the surgical procedure or the duration and risk of anesthesia is considerable, exchange transfusion or erythrocytapheresis can reduce the hemoglobin S concentration to 30%, while keeping the total hemoglobin level below 12 g/dL.

In patients undergoing retinal surgery, the HbS concentration or combined concentration of HbS and HbC needs to be reduced to less than 30% (increase the hemoglobin A concentration to 70%).

Individualize all other situations based on the complexity of the procedure and underlying medical condition.

Treatment of iron overload

With continued transfusion, iron overload inevitably develops and can result in heart and liver failure, and multiple other complications. Serum ferritin is an inaccurate means of estimating the iron burden; liver iron evaluation, or perhaps MRI, is a more accurate means of determining tissue iron concentration and the response to chelation.

Three agents are available for iron chelation: deferoxamine, deferasirox, and deferiprone.

Deferoxamine is an efficient iron chelator. It is administered as a prolonged infusion intravenously or subcutaneously for 5-7 days a week. Although effective, there are significant challenges associated with its use that can result in non-compliance. ^[70]

Deferiprone and deferasirox, oral iron chelators, are effective for iron overload treatment and have differences (eg, different pharmacokinetics and adverse effect profiles). Deferasirox has a capacity similar to  deferoxamine in chelating iron, but it is administered orally. Renal toxicity might be a limiting factor in its use, but it is generally safe. Deferiprone does not seem to be as effective as the other 2 agents and is considered a second-line therapy. Unlike deferasirox and deferoxamine, it selectively removes cardiac iron; is most effective when used in combination with deferoxamine or deferasirox. 

A novel new iron chelator is being developed but is still in the clinical testing phase. ^[71]

Erythrocytapheresis

Erythrocytapheresis is an automated red cell exchange procedure that removes blood that contains HbS from the patient while simultaneously replacing that same volume with packed red cells free of HbS. ^[72] Transfusion usually consists of sickle-negative, leuco-reduced, and phenotypically matched blood for red cell antigens C, E, K, Fy, and Jkb.

The procedure is performed on a blood cell processor (pheresis machine) with a continuous-flow system that maintains an isovolemic condition. RBCs are removed and simultaneously replaced, with normal saline followed by transfused packed RBCs along with the patient's plasma. The net RBC mass/kg is calculated for each procedure based on the measured hematocrit of the transfused and removed blood and the total RBC volume transfused.

Erythrocytapheresis thus has the advantage of controlling iron accumulation in patients with SCD who undergo long-term transfusion, as well as the ability to achieve adequate Hb and HbS concentrations without exceeding the normal concentration. This precision is achieved because, before the start of the transfusion, the computer in the pheresis machine calculates the expected amount of packed RBCs required to obtain a specific posttransfusion hemoglobin level, using various physiologic parameters (eg, height, weight, Hb level). Further, erythrocytapheresis requires less time than simple transfusion of similar blood volumes.

Although erythrocytapheresis is more expensive than simple transfusion, the additional costs associated with simple transfusions (ie, those of chelation and organ damage due to iron overload) make erythrocytapheresis more cost-effective than simple transfusion programs. Central venous access devices can safely be used for long-term erythrocytapheresis in patients with SCD, with a low rate of complications.

Ocular treatment is directed toward preventing vision loss from vitreous hemorrhage, retinal detachment, and epiretinal membranes. Medical ocular management may include topical medications; however, avoid carbonic anhydrase inhibitors, because they may cause further sickling and worsen the outflow obstruction. If the intraocular pressure remains elevated after a judicious trial of medical therapy, surgical intervention with an anterior chamber lavage is indicated.

The goal of treatment is to eliminate existing neovascularization and, thus, to eliminate the sequelae of proliferative sickle retinopathy (PSR). Modalities to treat proliferative sickle retinopathy include diathermy, cryotherapy, xenon arc photocoagulation, and argon laser photocoagulation.

Diathermy is used infrequently because of the high incidence of complications accompanying this procedure. Cryotherapy, both single freeze-thaw and triple freeze-thaw, has been used to treat PSR. Triple freeze-thaw has a high complication rate. Single freeze-thaw is used to treat peripheral vitreous hemorrhage in the presence of vitreous hemorrhage. Xenon arc and argon laser photocoagulation have been used to treat either the peripheral neovascularization or the feeder vessels to the neovascularization.

Photocoagulation applied through various techniques (eg, feeder vessel, focal scatter, peripheral circumferential scatter) is effective for treating proliferative sickle retinopathy and reducing the risk of vision loss. Because of potential complications from photocoagulation and the tendency for regression, patients older than 40 years probably do not require treatment. Complications of photocoagulation include choroidal neovascularization, retinal breaks, and peripheral choroidal ischemia.

Surgical treatment

Surgical procedures may be performed to treat retinal detachments, nonclearing vitreous hemorrhage, and epiretinal membranes. Based on a 71% incidence of anterior segment ischemia in patients with PSR who are undergoing scleral buckling surgery, prophylactic preoperative exchange transfusions or erythropheresis is recommended. Risks associated with exchange transfusions and improvement in vitreoretinal surgical techniques warrant a careful reevaluation of prophylactic exchange transfusions.

Perioperative measures to reduce the incidence of anterior segment ischemia include the following:

• Nonsympathomimetic local anesthesia
• Minimization of topical sympathomimetics
• Supplemental oxygen for 48 hours after surgery
• Avoiding wide encircling scleral buckling elements, expansile concentrations of intraocular gases, and carbonic anhydrase inhibitors
• Closely monitoring and treating elevated intraocular pressure

Anterior segment ischemia after surgery is an emergency. Although the prognosis is notoriously poor, make all attempts to oxygenate the anterior segment. Options include hyperbaric oxygen therapy, continuous supplemental oxygen therapy, and transcorneal oxygen with goggles. ^[73]

Elevated intraocular pressure

Blood in the anterior chamber in patients with sickle cell disease is a medical emergency. A sickle screen is warranted for every black patient who has an unexplained hyphema. ^{[74, 75]} The environment of the anterior chamber promotes sickle hemoglobin polymerization, which can result in elevated intraocular pressure due to blockage of the trabecular meshwork.

Because patients with sickle cell disease are particularly prone to central retinal artery occlusion and optic atrophy, even with mildly elevated intraocular pressures, closely monitor the intraocular pressure. Do not allow it to exceed 25 mm Hg for longer than 24 hours.

Vaso-occlusive crisis is treated with vigorous intravenous hydration and analgesics. Intravenous fluids should be of sufficient quantity to correct dehydration and to replace continuing loss, both insensible and due to fever. Normal saline and 5% dextrose in saline may be used. Treatment must be in an inpatient setting.

A retrospective chart review from a tertiary center identified characteristics associated with admission and longer length of stay in patients who presented to the ED in vaso-occlusive crisis. ^[76] Predictors of admission included the following:

• Higher pain score at triage
• Older age
• Increased systolic blood pressure

Factors associated with longer length of hospital stay included the following:

• Higher pain score at triage
• Older age
• Increased polymorphonuclear count
• Homozygous SCD type

The authors conclude that these characteristics will help healthcare providers predict and plan admission and management of children with SCD.

The randomized BABY HUG study has demonstrated that hydroxyurea (hydroxycarbamide) significantly reduces the incidence of vaso-occlusive crisis and dactylitis in very young children. ^[77] The primary toxicity observed was neutropenia. Further study is needed to evaluate long-term treatment effects on growth and development as well as renal, lung, and CNS function. A randomized, placebo-controlled trial in adults did not demonstrate a significant improvement in the time to resolution of vaso-occlusive crisis. ^[78]

Crizanlizumab, a P-selectin inhibitor, was approved by the FDA in November 2019 to reduce frequency of vaso-occlusive crisis (VOC) in adults with sickle cell disease. Binding P-selectin on the surface of activated endothelium and platelet cells blocks interactions between endothelial cells, platelets, red blood cells, and leukocytes. Approval was based on the SUSTAIN clinical trial which showed crizanlizumab reduced the median annual rate of VOCs leading to health care visits by 45.3% compared with placebo (1.63 vs 2.98, P=0.010) in patients with or without hydroxyurea. ^{[58, 59]}  

Pain control is best achieved with opioids. Morphine is the drug of choice.

The United Kingdom's National Institute for Health and Care Excellence (NICE) guidelines on sickle cell acute painful episodes (published in in 2012 and confirmed in 2014) include the following recommendations ^[45] :

• Tailor the analgesic drug, dose, and administration route to the severity of the pain, the age of the patient, and any other pain medications the patient is concurrently taking for the current episode
• Offer a bolus of a strong opioid (eg, morphine) to all patients with severe pain and all patients with moderate pain who have already taken an analgesic
• Consider a weak opioid (eg, acetaminophen and codeine) for patients with moderate pain who have not yet had any analgesia
• Offer all patients regular acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs) by a suitable administration route, in addition to an opioid, unless contraindicated
• Do not give meperidine for pain relief
• Chronic opiod use may cause adverse reactions (eg, constipation, dizziness, and itching), offer laxatives, antiemetics and antipruritics as needed

In the United States, 2014 recommendations from an expert panel convened by the National Heart, Lung, and Blood Institute for treatment of pain in patients experiencing a vaso-occlusive crisis included the following ^[49] :

• Initiate analgesic therapy within 30 minutes of triage, or 60 minutes of registration
• Whenever possible, use an individualized prescribing and monitoring protocol (written by the patient’s SCD provider) or an SCD-specific protocol
• In patients with mild to moderate pain, continue treatment with NSAIDs in those who report relief with these agents, unless contraindicated
•  In patients with severe pain, rapidly initiate treatment with parenteral opioids
• Calculate the opioid dose on the basis of the patient’s current short-acting opioid dose being taken at home
• Administer opioids subcutaneously if intravenous access is not obtainable
• Reassess pain every 15-30 minutes until the patient reports that pain is under control; readminister opioids if necessary for continued severe pain
• Reassess for pain relief and monitor for adverse effects after each dose
• Maintain the opioid dose or consider escalation by 25% until pain is controlled
• Administer opioids by around-the-clock patient-controlled analgesia (PCA) or frequently scheduled doses rather than on an as-requested (prn) basis
• In patients receiving PCA, continue long-acting oral opioids unless these agents need to be withheld to prevent oversedation
• At discharge, titrate off the parenteral opioids before conversion to oral opioids, and adjust the home dose of long- and short-acting opioids to prevent opioid withdrawal
• Do not use meperidine unless it is the only effective opioid for that patient
• Use oral NSAIDs as an adjuvant analgesic, unless contraindicated
• Prescribe oral antihistamines for patients who require these agents for itching from opioids; give repeat doses every 4-6 hours, if needed, rather than with each dose of opioid

Morphine dosing has to be individualized. The drug should be given intravenously, hourly at first. Once the effective dose is established, it should be administered every 3 hours. After 24-48 hours, as pain is controlled, equivalent doses of sustained-release oral morphine should be given.

When marked improvement occurs, the patient may be discharged home on sustained-release oral morphine, and the dose is reduced gradually over several days. Morphine elixir can be used to control breakthrough pain.

British Committee for Standards in Haematology (BCSH) 2015 guidelines for treatment of acute chest syndrome (ACS) recommend use of the following measures ^[79] :

• Prompt and adequate pain relief
• Incentive spirometry – In patients with chest or rib pain, to prevent ACS; should be considered in all patients with ACS
• Antibiotics, with cover for atypical organisms, even if blood cultures and sputum cultures are negative
• Anti-viral agents– If there is a clinical suspicion of H1N1 infection
• Early simple transfusion should be considered early in patients with hypoxia; however, exchange transfusion is necessary in patients with severe clinical features or evidence of progression despite initial simple transfusion
• Transfused blood should be sickle-negative and fully matched for Rh (C, D, and E type) and Kell antigens; a history of previous red cell antibodies should be sought and appropriate antigen-negative blood given
• Bronchodilators should be provided in patients with symptoms suggesting a history of asthma or evidence of acute bronchospasm

Simple transfusion administered early may halt progressive respiratory deterioration, preventing complications such as increasing tachypnea and need for supplemental oxygen. If necessary, an exchange transfusion is performed by removing 1 unit of blood and transfusing 1 unit. The aim is to reduce the concentration of HbS to less than 30%. This can be achieved by repeating the exchange transfusion or by using a continuous-flow pheresis.

Adults, in general, need a higher rate of transfusions and longer hospitalization than children.

Empiric antibiotics should be initiated and given intravenously, after obtaining samples for appropriate cultures. The antibiotics chosen should be active against Streptococcus pneumoniae, Mycoplasma pneumoniae, and Chlamydia; for the latter two, a macrolide may be appropriate. Antibiotic changes are based on response to therapy and results of cultures and sensitivities.

Analgesics are required. Agents that do not suppress respiration, including acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs), can be used. Narcotic agents may be used judiciously for more severe pain. Other supportive measures include careful hydration. Volume overload must be avoided, as it may contribute to pulmonary infiltrates and exacerbate hypoxia.

Elevated levels of serum phospholipase A2 levels have been found to be associated with ACS and might predict its occurrence. In pilot studies, transfusion of patients who had pain, fever, and increased serum phospholipase A2 levels have apparently thwarted development of ACS. ^[80]

For episodes of severe hypoxia, rapid progression, diffuse pulmonary involvement, and failure to improve, erythrocytapheresis is indicated. Intensive care is indicated for patients in severe hypoxia or respiratory distress, as respiratory decompensation can rapidly require mechanical ventilation.Treatment should also include oxygen therapy with close monitoring for hypoxemia with continuous pulse oximetry or frequent assessment of blood gases.

Administer oxygen if saturation is less than 94%. If that level cannot be maintained at a fraction of inspired oxygen (FiO₂) of 0.4, provide simple transfusion (avoid raising hematocrit to more than 36%). If no improvement is seen, reduce the HbS level to 30% with erythrocytapheresis or exchange transfusion. The process can rapidly progress to respiratory failure. Ventilatory assistance may be required.

The role of corticosteroids in nonasthmatic patients with ACS remains a topic of clinical research. Both significant benefits and serious adverse effects have been reported with their use. ^[81]

Some patients have repeated severe episodes of ACS. Regular transfusion reduces the recurrence and hydroxyurea reduces the rate of acute chest syndrome by about half.

Chronic pain is managed with long-acting oral morphine preparations, acetaminophen, and NSAIDs. NSAIDs are particularly effective in reducing bone pain.

Many patients may require breakthrough oral opiates as well. The weak opiates (eg,codeine and hydrocodone) are commonly used first. Sustained-release long-acting oral morphine is reserved for more severe cases. Hydromorphone may also be used but is considerably more expensive than morphine. Meperidine is not recommended for pain treatment because of CNS toxicity related to its metabolite, normeperidone.

The addition of tricyclic antidepressants may reduce the dose and need for opiates by interfering with pain perception. In addition, many patients with chronic pain are depressed, and lifting the depression has a salutary effect on the pain as it elevates the pain threshold.

Hydroxyurea may decrease the frequency and severity of pain episodes. ^[64] The safety of long-term hydroxyurea use in children remains uncertain, however (see Hydroxyurea Therapy, above).

Nonpharmacological approaches to pain management may have a substantial impact. These include physical therapy, heat and cold application, acupuncture and acupressure, hypnosis, and transcutaneous electric nerve stimulation (TENS). Support groups are also useful.

Inform parents and children that recurring pain is expected. Assist them in developing an approach that allows continued normal activities even with pain. Instruct parents and family members to provide sympathy but to do so with encouragement and support, so as to help the child accept the pain, rather than to submit to it.

Parents and family members are encouraged to provide local measures and over-the-counter drugs for mild pain. Physicians suggest keeping on hand a small supply of a mild narcotic analgesic for pain that does not respond to lesser measures.

Pain that does not respond to the above measures almost always requires hospitalization. In such cases, treat with morphine or other major narcotic analgesics in doses sufficient to provide a reasonable degree of relief. Continuous infused morphine is most effective. Attempting to resolve pain by providing 1-2 doses of parenteral narcotics in the emergency department is inadvisable, since moderately severe sickle cell pain is expected to persist for several days.

Choose a dosage to provide reasonable pain relief with precautions to avoid oversedation and respiratory depression. A starting dose of morphine (0.05-0.01 mg/kg/h) is suggested following a bolus dose to provide a reasonable degree of pain relief. Adjust according to patient response. Patient-controlled analgesia with self-administered bolus morphine and low-dose continuous intravenous infusion is effective and well accepted by patients.

Fentanyl and nalbuphine have also been used as continuous IV infusion. Ketorolac can be given along with opioid analgesics and typically reduces the opioid dose required to achieve the desired effect.

Opioid dependence may occur. It can result if a patient uses narcotics for euphoriant or stimulant effects rather than analgesia. Narcotic addiction in people with SCD is no more common than in the general population and may be minimized with a carefully designed analgesic regimen and maintenance of proper pain control.

When drug addiction with substance abuse is present, however, difficult management problems ensue. These require a team approach involving counselors, substance abuse specialists, hematologists, and pain management experts.

Chronic opioid therapy

Patients with SCD who have emerging and/or recently developed chronic pain that is refractory to multiple other treatment modalities may benefit from regularly scheduled administration of opioids; this strategy is termed chronic opioid therapy (COT). According to the American Society of Hematology, COT should be considered after risk stratification using a validated tool, based on the following ^[82] :

• How well the patient’s SCD is managed
• Comprehensive assessment of behavioral risks (eg, risk factors for opioid misuse)
• Implications of opioid tolerance on the management of acute pain episodes
• Other known adverse effects of opioids

As the benefit of COT in SCD is largely unknown and the harms have been established via indirect evidence, ASH advises that shared decision-making is essential before initiating a trial of COT. The decision-making process should include discussion of failure criteria for the trial, along with development of a plan for opioid cessation and alternative treatments to try in the case of failure.

ASH remarks regarding COT include the following:

• The profile of each opioid drug under consideration for use in a given patient should be reviewed, as individual opioid drugs have different specific toxicity profiles and interactions with end-organ injury.
• Prescribe the lowest effective opioid dose.
• Patients on COT should avoid the use of benzodiazepines, sedating medications, and alcohol.
• Providers should be aware that patients may inadvertently end up on COT if episodic pain is frequent enough that patients are receiving frequent opioid treatment of recurrent pain. Therefore, providers should make efforts to reduce or eliminate scheduled opioid doses between acute episodic pain events, which may reduce the likelihood of unintentional COT.
• Acute pain events may still be treated with opioid analgesia if this serves the overall pain treatment plan, but this should be done in conjunction with the primary outpatient management team. Furthermore, nonopioid medications and integrative therapies should also be offered; strategies for these can be developed through collaboration with a pain specialist.
• Patients on COT require careful monitoring with regard to functional status and risk assessment for the development of aberrant opioid use and medical, social, behavioral, or psychological complications, as a precursor to opioid dose reduction or weaning.
• Weaning and/or withdrawal from COTpotentially poses higher risk in patients with SCD (ie, it may trigger vasoocclusive events or other medical complications) and should be done carefully.
• The risk of adverse events related to COT rises as the total dose increases. Therefore, patients on high doses of opioids need close monitoring for complications and adverse effects.

Adverse events that have been noted in other non-SCD patient populations are dose dependent and include increased risk of the following:

• Poor surgical outcomes
• Motor vehicle collisions
• Myocardial infarction
• Bone fracture
• Mortality
• Hormonal alterations, which can lead to sexual dysfunction, with doses of >120 mg morphine milligram equivalents (MME)
• Overdose – Risk of overdose is ninefold higher with doses >100 mg MME, compared with doses < 20 mg MME in general non-SCD pain populations

.

Anemia is usually well tolerated. Because of the high RBC turnover, folate stores are often depleted. Althogh no scientific evidence shows that patients develop folate deficiency, folic acid (1 mg/d) is commonly prescribed for adults to prevent development of megaloblastic anemia due to increased folate requirements caused by hemolysis. Folic acid supplementation may raise the Hb level and support a healthy reticulocyte response.

Usual doses for folic acid therapy are age based, as follows:

• Younger than 6 months: 0.1 mg/day
• Ages 6 months to 1 year: 0.25 mg/day
• Ages 1-2 years: 0.5 mg/day
• Older than 2 years: 1 mg/day

Women who are menstruating should be checked for coexisting iron deficiency and, if it is found, given iron supplements. An adequate overall diet is essential.

Voxelotor, which was approved by the FDA in November 2019, is the first drug approved by the FDA for sickle cell disease based solely on data showing an increase in hemoglobin. It is indicated for treatment of sickle cell disease in adults and adolescents aged 12 years or older. Voxelotor is a hemoglobin S (HbS) polymerization inhibitor that binds to HbS with a 1:1 stoichiometry and exhibits preferential partitioning to RBCs. By increasing the affinity of Hb for oxygen, voxelotor demonstrates dose-dependent inhibition of HbS polymerization. 

Approval of voxelotor was based on results from a clinical trial that enrolled 274 patients with sickle cell disease and treated them with either 1500 mg or 900 mg PO once daily of voxelotor or placebo. Results showed 51% patients on the higher dose of voxelotor achieved a hemoglobin response, defined as an increase in hemoglobin of at least 1 g/dL after 24 weeks. Just over 6% of the placebo patients had the same hemoglobin response. At week 24, the 1500-mg voxelotor group had significantly greater reductions from baseline in the indirect bilirubin level and percentage of reticulocytes than the placebo group. ^[60]

Blood transfusion is indicated only in specific situations. These include acute chest syndrome, stroke, abnormal findings on transcranial Doppler in children (for stroke prevention), pregnancy, and general anesthesia. The aim is to decrease the concentration of HbS to 30% or less. Transfusion may also be required during aplastic crisis.

For anemic crisis with splenic sequestration, give early red cell transfusions because the process can rapidly progress to shock. Do not allow hemoglobin (Hb) levels to rise to more than 10 g/dL, since the spleen may disgorge trapped cells, which can create a relative polycythemia and increased blood viscosity.

Children who experience a single sequestration event frequently have recurrences. Surgical splenectomy or a short-term transfusion regimen has been suggested for this complication.

Transfusion is required in an aplastic crisis if the anemia is symptomatic (eg, dyspnea, signs of hypovolemia). Because aplastic crises are self-limited, transfusion may be avoided if the child is stable and can be adequately observed. If hospitalization is required, use precautions to prevent transmission of parvoviral infection to patients who are immunosuppressed or caretakers who are pregnant.

Neonatal screening, penicillin prophylaxis, appropriate immunizations (particularly against Streptococcus pneumoniae), and parental teaching have remarkably minimized infection-related morbidity and mortality. Prevention of infection also improves chances of survival in SCD. In the adult patient, all infections must be treated promptly with broad-spectrum antibiotics. Once a causative organism is identified, therapy is tailored according to its antibiotic sensitivity.

Antibiotics are indicated when an infection is suspected, when body temperature is higher than 38° C, or when a patient has localized bone tenderness. The 2003 BCSH guidelines also recommend the use of broad-spectrum antibiotics in the patient who is systemically ill or has chest involvement. ^[45] Fever in children is strongly suggestive of infection. Signs of infection have proved to be more accurate in children than in adults.

Recommended parenteral antibiotics include cephalosporins (eg, ceftriaxone, cefuroxime) and macrolides for acute chest syndrome. If the patient is discharged home, oral antibiotics (eg, amoxicillin-clavulanic acid, clarithromycin, cefixime) are useful in selected cases. If the patient has localized bone tenderness, the antibiotic selected should provide coverage for Salmonella typhimurium and Staphylococcus aureus.

Penicillin prophylaxis significantly reduces the incidence of infection with encapsulated organisms—in particular, S pneumoniae —and may decrease the mortality rate. Begin at age 2 months with 125 mg bid of penicillin V or G; at 3 years, increase the dose to 250 mg bid. Prophylaxis should continue until age 5 years or the early teens. Recent trials have shown that the susceptibility for septicemia with encapsulated organisms persists well into adulthood, and the benefit of continuing penicillin prophylaxis is now the subject of clinical research. If the patient is allergic to penicillin, erythromycin may be substituted.

As with all long-term medication regimens, maintaining compliance can be difficult. Therefore, remind parents of the importance of prophylaxis at each visit.

Protein-conjugated pneumococcal vaccines (PCVs) that effectively protect children against invasive infections are now extensively used. The 7-serotype PCV (PCV7) in combination with penicillin prophylaxis and PPV23 booster vaccination offers the best hope for improved prevention against S pneumoniae infection. The vaccine is given at age 2 years, with a booster dose at age 5 years.

In one study, more than two thirds of S pneumoniae isolates stereotyped were PCV7 serotypes and included most penicillin-nonsusceptible strains. Most nonvaccine-serotype isolates were penicillin-sensitive.

In addition to receiving pneumococcal vaccination, pediatric patients with SCD should follow the immunization schedule currently recommended by the American Academy of Pediatrics, including meningococcal vaccination. Meningococcal prophylaxis is administered as a single quadrivalent vaccine when the child is older than 2 years.

Treatment of acute cholecystitis in patients with sickle cell disease does not differ from that for the general population. Patients receive antibiotics and general supportive care and may consider elective cholecystectomy several weeks after the acute episode subsides. Elective laparoscopic cholecystectomy in a well-prepared patient has become the standard approach for symptomatic disease. If patients present with right upper quadrant abdominal pain, evaluate the gallbladder with ultrasonography. Provide appropriate medical and supportive care for cholecystitis if stones are visualized, if gallbladder walls are thickening, or upon signs of ductal inflammation.

Elective cholecystectomy has been used for asymptomatic patients with cholelithiasis, to avoid the possible future need for an emergent procedure. This approach remains controversial.

A retrospective review of 191 cholecystectomies in pediatric sickle cell patients with cholelithiasis (51 elective, 110 symptomatic, and 30 emergent) found postoperative hospitalization time was longer with emergent cholecystectomy than with elective or symptomatic cholecystectomy. Goodwin et al concluded that although overall outcomes for symptomatic and elective patients are favorable, prospective studies are needed to identify clinical indicators that predict the need for emergent cholecystectomy. ^[83]

At the onset of priapism, patients should be advised to drink extra fluids, use oral analgesics, and attempt to urinate. A nightly dose of pseudoephedrine (30 mg orally) may prevent priapism in some cases.

For episodes that last more than 2 hours, patients should go to the emergency department to receive intravenous hydration and parenteral analgesia. According to one protocol, if detumescence does not occur within 1 hour after arrival in the emergency department, penile aspiration followed by irrigation of the corpora with a 1:1,000,000 solution of epinephrine in saline is initiated. ^[84] (The procedure should be performed within 4-6 h of priapism onset.)

The concomitant use of automated red cell exchange transfusions to reduce the HbS level to less than 30% may also be considered, especially if early intervention with irrigation fails. Should the condition recur despite aspiration and local instillation of vasoactive drugs, consider shunting. In this procedure, known as the Winter procedure, a shunt is created between the glans penis and the distal corpora cavernosa; this allows blood from the distended corpora cavernosa to drain into the uninvolved corpus spongiosa. A larger shunt may be created if this is not successful.

Complications of priapism and treatment include bleeding from the holes placed in the penis as part of the aspiration or shunting procedures, infections, skin necrosis, damage or strictures of the urethra, fistulas, and impotence. If impotence persists for 12 months, the patient may wish to consider implantation of a semirigid penile prosthesis.

New approaches to prevent recurrent priapism include use of phosphodiesterase type 5 inhibitors (eg, sildenafil, tadalafil). In a pilot study and a small randomized, controlled trial (n = 13), long-term treatment with these agents alleviated recurrent priapism in some patients with SCD. ^{[85, 86]} However, a systematic review of sidenafil, stilbestrol, etilefrine, or ephedrine to reduce the frequency of stuttering priapism in boys and men with SCD identified only three trials with 102 participants, and concluded that there is a lack of evidence for the benefits or risks of these drugs in this setting. ^[87]

Leg ulcers are treated with debridement and antibiotics. Zinc oxide occlusive dressing (Unna boot) and leg elevation are employed. Transfusion may accelerate healing. Skin grafting may be necessary in recalcitrant cases. Leg ulcers may result from venous stasis and chronic hypoxia and may become infected. Management is the same as with other stasis ulcers.

Adults with SCD should be evaluated for known stroke risk factors and managed according to the 2014 AHA/ASA primary stroke prevention guidelines. ^[44]

The AHA and ASA also provided guidelines for the prevention of stroke in patients with stroke or transient ischemic attack. These secondary stroke prevention guidelines include recommendations for controlling risk factors and the use of antiplatelet agents. Other therapies to consider in preventing recurrent cerebral ischemic attacks in adults with SCD include regular blood transfusions (to reduce HbS to < 30%-50% total hemoglobin), hydroxyurea, or bypass surgery for advanced occlusive disease. ^[88]

Transfusion therapy, aimed at keeping the proportion of HbS below 30%, is now considered standard care for primary and secondary stroke prevention in children with SCD. The Stroke Prevention Trial in Sickle Cell Anemia (STOP) showed that regular blood transfusions produced a marked (90%) reduction in first stroke in asymptomatic high-risk children who had 2 abnormal transcranial Doppler (TCD) studies with velocities of 200 cm/s or greater. ^[89] According to the 2014 AHA/ASA primary stroke prevention guidelines, this form of therapy has been proven effective for reducing stroke risk in those children at increased risk for stroke. ^[44]

During the transfusion period, most of the TCD studies reverted to or toward normal. Once the transfusion program was stopped, however, there was an unacceptably high rate of TCD reversion to high risk, as well as to actual strokes. ^[51]

Unless long-term transfusion therapy is provided, 70-90% of children who experience a single stroke have subsequent events. DeBaun et al reported that in children with SCD, regular blood transfusions significantly reduced the rate of cerebral infarct recurrence. ^[90]

As patients grow into adulthood, the transfusion frequency may be decreased, but whether it can be discontinued remains unclear. Many believe that lifelong transfusion therapy is necessary to completely eliminate recurrences in patients with SCD. The AHA/ASA primary stroke prevention guidelines endorse (pending further study) the continued use of transfusion, even in those with TCD velocities that return to normal. ^[44] Iron overload from repeated transfusions requires chelation therapy after 2-3 years.

Erythrocytapheresis is now increasingly used as an alternative to simple transfusion. This procedure allows rapid reduction of HbS concentrations to less than 30% without significantly increasing total hemoglobin concentration post transfusion (see Transfusion, above).

According to the AHA/ASA primary prevention guidelines, hydoxyurea or bone marrow transplantation might be an option for children at high risk for stroke in whom RBC transfusion is contraindicated. ^[91] For children with a human leukocyte antigen (HLA)–matched sibling, a consortium has demonstrated that the risk of recurrent stroke can be greatly reduced with allogeneic bone marrow transplantation. This offers an alternative to long-term transfusion and iron chelation. ^[92]

The Stroke With Transfusions Changing to Hydroxyurea (SWiTCH) trial documented no strokes in patients with SCD (n=66) who received monthly transfusions plus daily deferasirox iron chelation but seven strokes in patients (n=67) treated with hydroxyurea plus overlap transfusions during dose escalation to maximum tolerated dose, followed by monthly phlebotomy. Although the stroke percentage with hydroxyurea/phlebotomy was within the noninferiority stroke margin, the National Heart, Lung, and Blood Institute closed SWiTCH after interim analysis revealed equivalent liver iron content in the two groups, indicating futility for the composite primary end point. The SWiTCH investigators concluded that “transfusions and chelation remain a better way to manage children with SCA, stroke, and iron overload”. ^[93]

In the TCD With Transfusions Changing to Hydroxyurea (TWiTCH) trial, hydroxycarbamide treatment was found to be noninferior to transfusion therapy for maintaining TCD velocities and helping to prevent primary stroke. TWiTCH was conducted in high-risk children with sickle cell anemia and TCD velocities ≥200 cm/s who had received at least 1 year of transfusions and had no severe vasculopathy identified on magnetic resonance angiography. ^[94]

In TWiTCH, no strokes were identified in patients treated with either transfusions (n=61) hydroxycarbamide (n=60), but three transient ischemic attacks occurred in each group.  TCD velocities were 143 cm/s in children who received transfusions and 138 cm/s in those who received hydroxycarbamide. ^[94]

Pulmonary hypertension, defined as a tricuspid regurgitant jet velocity (TRJV) greater than 2.5 m/s on echocardiography, is an emergent complication seen in 32% of adult patients with SCD and is associated with a high mortality rate. Pulmonary hypertension is a complication of chronic intravascular hemolysis. Additional factors contributing to pulmonary hypertension include older age, renal insufficiency, cardiovascular disease, cholestatic hepatopathy, systolic hypertension, high hemolytic markers, iron overload, and a history of priapism.

Even modestly increased pulmonary artery pressures are associated with severe reduction in exercise capacity, as assessed by both the 6-minute walk and cardiopulmonary exercise testing, and herald a poor prognosis. Both pulmonary hypertension and cardiac sequelae, such as diastolic dysfunction, have been associated with accelerated mortality in the sickle cell disease population.

For symptomatic patients, hydroxyurea and chronic transfusion have been used. Enothelin-1 receptor antagonists (eg, bosentan) and phosphodiesterase inhibitors (eg, sildenafil) have been used, but their role is limited by other complications. Cor pulmonale may ensue, and the management is that of patients with right-sided heart failure and chronic obstructive pulmonary disease.

See Nephrologic Manifestations of Sickle Cell Disease for more information on this topic.

Avascular necrosis of the femoral and humeral heads is treated by not bearing weight at the site. The patient may need to make career and lifestyle adjustments. Occupational retraining and physical therapy may be needed. In many cases, surgical intervention with hip replacement or other orthopedic procedures are needed. Avascular osteonecrosis may result from chronic hypoxia in weight-bearing joints, commonly the femoral head. Joint replacement is often necessary.

SCD can promote psychological problems, such as depression, anxiety, and chronic pain behavior. Counseling is crucial. Ensure an appropriate physician-patient relationship. Anxiolytics and amitriptyline may be used.

In December 2023 the FDA approved the first 2 gene-editing therapies for severe SCD) in patients aged 12 years and older. One therapy, exagamglogene autotemcel (Casgevy), is the first to use the gene-editing tool CRISPR. The other, lovotibeglogene autotemcel (Lyfgenia), uses a different gene-editing tool called a lentiviral vector. 

Exagamglogene autotemcel

Exagamglogene autotemcel is a non-viral cell therapy designed to reactivate fetal hemoglobin via ex vivo CRISPR-Cas9 gene-editing of autologous CD34+ hematopoietic stem and progenitor cells (HSPCs). It specifically acts at the erythroid-specific enhancer region of the BCL11A gene. ^[95]  

In the ongoing phase III CLIMB SCD-121 trial, 42 patients with severe SCD had received exagamglogene autotemcel as of February 2023. Of the patients evaluable for primary endpoint, 19 of 20 (95%) had experienced no vaso-occlusive crisis (VOC) for at least 12 consecutive months (P < 0.0001) and 20/20 (100%) had not been hospitalized for VOCs for at least 12 consecutive months (P < 0.0001); 29/30 (96.7%) had been free of VOCs for at least 9 consecutive months (P < 0.0001). ^[95]  

Lovotibeglogene autotemcel

Lovotibeglogene autotemcel is manufactured by modifying autologous stem cells, using lentiviral vectors to add normal globin genes, gene editing to correct the sickle cell disease mutation, and genetic silencing to enhance production of fetal hemoglobin. ^{[96, 97]} A pilot study by Esrick et al reported reduction or elimination of clinical manifestations of SCD in six patients who received autologous CD34+ cells transduced with a lentiviral vector that downregulates a gene responsible for repressing fetal hemoglobin production in adult red blood cells. ^[98]  

Approval was supported by the phase I/II HGB-206 and phase III HGB-210 studies. These showed that a one-time treatment resulted in sustained production of HbAT87Q (an anti-sickling hemoglobin) and nearly complete resolution of vaso-occlusive events (VOEs) and severe VOEs up to 18 months post treatment. ^{[99, 100, 101]}

Allogeneic hematopoietic stem cell transplantation (HSCT) can cure SCD. Most transplants are performed in younger patients, and results are better in that population: an international survey of human leukocyte antigen (HLA)–identical sibling HSCT found that median age at transplantation was 9 years, and the 5-year overall survival rate was 95% for children under age 16 and 81% for those age 16 and older; the 5-year graft-vs-host disease (GVHD)–free survival rate in those age groups was 86% and 77%, respectively. ^[61]

To date, HSCT has been considered indicated in SCD patients younger than 16 years with HbSS or HbS–β-0 thalassemia who have severe disease, as evidenced by one or more of the following ^[102] :

• Stroke (or central nervous system event lasting longer than 24 hours)
• Recurrent acute chest syndrome
• Recurrent severe crisis pain (>2 episodes/y for several years)
• Recurrent priapism
• Impaired neuropsychological function with evidence of cerebral infarction on imaging studies
• Sickle cell nephropathy (glomerular filtration rate 30–50% of predicted normal)
• Stage I or II sickle lung disease
• Bilateral proliferative retinopathy and major visual impairment in at least one eye
• Osteonecrosis of multiple joints
• Red cell alloimmunization with more than 2 antibodies during long-term transfusion therapy

HSCT for SCD has historically been limited to patients with an HLA-identical sibling donor. However, only 18% of patients with SCD have an HLA-matched sibling who does not have SCD. This has spurred the exploration of other donor options. Only 16% to 18% of African Americans have a full HLA-matched unrelated donor option in the national donor pool, but partial-matched unrelated donors, half-matched (ie, haploidentical) donors, and partial-matched cord blood have all been used. ^{[103, 62]}

Unrelated donor transplants are associated with a higher rate of GVHD than HLA-matched sibling donor transplants, but use of reduced-intensity or nonmyeloablative conditioning regimens in these cases has reduced the risk of GVHD and graft failure otherwise seen with non–fully matched donors. ^{[61, 62]} A reduced-intensity conditioning regimen was also used in a successful pilot study of HSCT in adolescents and young adults (age 17-36 years). ^[104]

A general well-balanced diet is required. No restrictions are necessary.

Although activity is unrestricted, patients may not be able to tolerate vigorous exercise or exertion. Patients with avascular necrosis of the femur may not be able to tolerate weightbearing and may be restricted to bed rest. Patients with chronic leg ulcers may need to restrict activity that involves raising the legs.

Encourage children to participate in physical activities. Because of anemia, they have less stamina than their hematologically healthy playmates. Advise supervising adults of this limitation, particularly teachers and coaches who may require children to run designated distances. Arrange for children to have ready access to liquids and a place to rest and cool off.

Investigational treatments include nitric oxide inhalation, topical granulocyte-macrophage colony-stimulating factor (GM-CSF), butyrate, and arginine, as follows:

• Nitric oxide inhalation has been investigated in the treatment of pulmonary hypertension.
• Topical GM-CSF has been reported to hasten the healing of leg ulcers.
• Butyrate was studied to decrease vaso-occlusive crisis.
• Arginine has been proposed to use as a precursor of nitric oxide production.

Consultation with a hematologist may be necessary. Each of the protean manifestations of SCD may require assistance from an expert in the involved area. Consultations with pain management experts, social workers, psychiatrists and physical therapists, substance abuse counselors, and vocational rehabilitation workers may be required. Consultation with infectious disease specialists is recommended during febrile illness.

If avascular necrosis of the hip is suspected in a patient with hip pain and difficulty in walking, consult an orthopedist for possible hip joint replacement. Orthopedic consultation is also appropriate if osteomyelitis is suspected. Interventional radiologists may play a role in obtaining a sample to identify the infecting organism in osteomyelitis. Imaging guidance may also allow the drainage of subperiosteal and soft tissue abscesses with the patient under light sedation, thereby avoiding surgery and general anesthesia.

If retinopathy or hyphema is suspected and visual symptoms are present, consultation with an ophthalmologist is warranted. In cases of priapism that does not resolve after 6 hours of hydration and analgesia, consult a urologist for corpus cavernosum aspiration or shunting.

A retina specialist should follow patients to monitor for retinal disease. Uncontrolled secondary glaucoma may require consultation with a glaucoma specialist.

Long-term follow-up is required for patients with SCD. This is a lifelong disorder. The frequency of outpatient visits depends on the patient's clinical status. For patients with minimal symptoms, a visit with blood work every 3-4 months is reasonable. Others may need much more frequent observation.

Educate all patients to recognize signs of infection, increasing anemia, and organ failure. Treat all infections, even trivial ones, very promptly and vigorously. Institute pain medication at the earliest symptoms of a vaso-occlusive crisis. Patients on a chronic transfusion program must adhere to iron chelation therapy. Social services, occupational therapy, and counseling are essential elements in the long-term management of patients with SCD.

Follow-up care depends on involvement with proliferative sickle retinopathy (PSR); once stabilized, visits every 3-6 months may be adequate. When intraocular pressures are stabilized, the patient can be monitored every 6 months

Fluid intake and output should be closely monitored in kidney transplant recipients. In comparison with the general population, these patients have an increased propensity toward intravascular volume depletion, especially secondary to volume losses (through, for example, diarrhea, vomiting, and insensible losses), thereby increasing the risk of an acute sickle cell crisis in patients with SCD.

Patients who have undergone a splenectomy as part of their SCD treatment regimen have an increased risk of infection with encapsulated organisms, such as Streptococcus pneumoniae. ^[105] Pneumococcal and influenza vaccination is safe in patients with functioning kidney transplants. ^{[106, 107, 108]} However, the use of live vaccines is contraindicated due to the immunosuppressive therapy that these patients require.

For infants with SCD, provide a suggested schedule for well-child visits to ensure that immunizations and other aspects of routine pediatric care are followed. For children aged 1-3 years with hemoglobin (Hb)SS and HbS–β-0 thalassemia, , consider visits every 3 months, to be certain that parents have sufficient penicillin for prophylaxis and to encourage compliance.