Sickle cell acute complications: Case

This boy has acute chest syndrome, the leading cause of death in sickle cell disease, emerging on the second day of a pain-crisis admission. The new right lower lobe infiltrate, the fever, the breathlessness, the cough, and the hypoxia together meet the definition, and the saturation of 89 percent on room air with the tachypnoea and the falling haemoglobin mark this as a moderate-to-severe episode that needs oxygen, antibiotics, and preparation for transfusion at once. The emergence after admission is typical, because the rib pain caused splinting and atelectasis that seeded the lung. [4]

Interpretation of the findings

The key findings are the new infiltrate, the hypoxia, the tachypnoea, and the falling haemoglobin, and together they define the acute chest syndrome and gauge its severity. The saturation of 89 percent on room air is below the target of 92 percent and confirms significant hypoxia, and the respiratory rate of 44 is raised for a four-year-old. The fall in the haemoglobin from a baseline of 75 g per litre to 62 g per litre reflects the haemolysis and the sequestration in the inflamed lung, and it signals that a transfusion is likely. [4]

The underlying pain crisis remains, and the combination of the chest and the limb pain explains why the boy splinted his chest and developed the atelectasis that precipitated the acute chest. There is no sign yet of a stroke or a sequestration, but the boy is at risk of both, and the assessment searches for the focal deficit and the enlarging spleen. The interpretation is that the boy has moved from a manageable pain crisis to a potentially fatal complication, and the response must match the change. [1]

Management: the resuscitation

The immediate management is oxygen, antibiotics, analgesia, and the preparation for transfusion. The boy is given oxygen to bring the saturation to or above 92 percent, and the intensive care team is informed early because the deterioration can be rapid. The blood cultures are taken and a third-generation cephalosporin such as cefotaxime is combined with a macrolide such as azithromycin, covering the bacteria and the atypicals. The analgesia for the underlying pain is continued with intravenous morphine at 0.1 mg per kg, because the relief of the rib pain lets the boy breathe deeply, and the fluids are kept at maintenance rather than as boluses, because the over-hydration would worsen the lung. [1]

The supportive care is not forgotten. The incentive spirometry is prescribed every two hours while awake to open the atelectatic lung, and the bronchodilator is given if there is wheeze. The boy is monitored continuously for the saturation, the respiratory rate, and the work of breathing, and the team is ready to escalate to the intensive care and the respiratory support if the hypoxia worsens. [4]

The transfusion decision

The transfusion is the central decision, and the severity and the haemoglobin trend guide the method. The boy has a moderate-to-severe episode with a falling haemoglobin and a significant oxygen requirement, and the question is whether a simple transfusion will suffice or whether an exchange transfusion is needed. The simple transfusion raises the haemoglobin cautiously and is used when the haemoglobin has fallen below the baseline and the oxygen requirement is moderate, and it is never pushed above about 100 g per litre to avoid the hyperviscosity. [7]

For this boy, with the saturation at 89 percent and the haemoglobin falling, the simple transfusion is the reasonable first step, and the response is watched closely. If the hypoxia worsens, the infiltrate spreads to a second lobe, or the haemoglobin continues to fall despite the transfusion, the boy is escalated to the exchange transfusion, which brings the haemoglobin S under 30 percent and removes the sickled blood. The exchange transfusion is the modality that reverses the severe acute chest, and the team that recognises the deterioration and escalates is the team that prevents the death. The extended red cell phenotype is confirmed before the transfusion to reduce the alloimmunisation that complicates the future care. [7][4]

Prevention and the long-term plan

After the acute event resolves, the plan turns to the prevention, because the boy who has had one acute chest syndrome is at risk of another. The hydroxyurea is the cornerstone, started at 20 mg per kg per day and escalated to the maximum tolerated dose, and the Multicenter Study of Hydroxyurea showed that it reduced the frequency of the pain crises and the acute chest syndrome. The boy's regimen is reviewed and optimised, and the adherence is supported. [5]

The boy who has recurrent acute chest syndrome despite the optimised hydroxyurea is a candidate for a chronic transfusion programme, which keeps the haemoglobin S under 30 percent and is given every three to four weeks, with the iron-overload monitoring and the deferasirox chelation that the transfusion brings. The family is given a written emergency plan, taught to recognise the early respiratory symptoms, and reminded that with this package the boy has the best chance of a childhood free of the severe acute chest and the death it once caused. [1][4]