Hypoxia in a Patient With Sickle Cell Disease

Case Study

A rapid response event was initiated by the bedside nurse for a patient with shortness of breath, hypoxia, and altered mental status. On prompt arrival of the rapid response team, it was noted that the patient was a 25-year-old female with a known history of sickle cell disease who was admitted to the hospital earlier in the evening for the evaluation of back pain, bilateral lower extremity pain, and chest pain. The patient’s oxygen saturation was 95% on room air at the time of admission. A chest X-ray at the time was negative for any pulmonary infiltrates. The patient had been started on hypotonic fluids and had been receiving hydromorphone through a patient-controlled analgesia pump for the vaso-occlusive crisis. She had received roughly 700 cc of fluids by the time condition was called.

Vital Signs

Temperature: 99.6 °F, axillaryBlood Pressure: 145/110 mmHg Pulse: 136 beats per min (bpm) – sinus tachycardia on telemetry Respiratory Rate: 38 breaths per min Pulse Oximetry: 82% on 6 L/min (LPM) O ₂through a nasal canula

Focused Physical Examination

A quick exam showed a young lady propped up in bed. She looked lethargic and in obvious respiratory distress. Appropriate personal protective equipment was established, and the patient was examined. She was able to follow simple commands appropriately. A pulmonary exam was significant for tachypnea. However, no wheezing or crackles were heard. Air movement was appropriate. Her cardiac and abdominal exam was benign.

Interventions

The patient was immediately started on a non-rebreather face mask at 15 LPM O ₂ , which improved the oxygen saturation to 91%. A stat arterial blood gas (ABG) was obtained, which showed pH 7.25, paO ₂ 56 mmHg, pCO ₂ 32 mmHg, O ₂ sat 89%, lactate 7.2 mmol/L, hemoglobin 6.3 g/dL. Stat chest X-ray was ordered, which showed a new infiltrate in the right lower lobe ( Fig. 28.1 ). Stat blood cultures were obtained, and one dose of piperacillin/tazobactam was started. Then, 2 mg IV morphine was administered for dyspnea. The patient was given etomidate and succinylcholine and intubated at the bedside. The patient was sent for a stat computed tomography (CT) angiogram of the chest to rule out pulmonary embolism and was transferred to the intensive care unit for possible exchange transfusion.

Final diagnosis

Acute respiratory failure from acute chest syndrome as a complication of sickle cell disease.

Acute Chest Syndrome

Sickle cell disease is a hemoglobinopathy that occurs in roughly one out of every 365 Black or African American births, per Centers for Disease Control and Prevention (CDC) data. It is caused by a point mutation in the beta-globin allele of the hemoglobin gene that leads to the production of the mutated protein (hemoglobin S). Hemoglobin S is less soluble than normal human hemoglobin (hemoglobin A), leading to its precipitation with the red blood cells (RBCs) in areas of the body with low oxygen tension. This leads to distortion of the shape of the RBC, called “sickling,” causing occlusion of the small capillaries, leading to intravascular hemolysis ( Fig. 28.2 ). Sickle cell disease is also associated with splenic sequestration and extravascular hemolysis, which are beyond the scope of this chapter. Vasco-occlusion and subsequent end-organ ischemia are responsible for the significant number of acute complications seen with sickle cell anemia, which include pain crises, stroke, myocardial infarction, acute chest syndrome, venous thromboembolism, renal infarction, dactylitis, and priapism. This chapter will focus on acute chest syndrome, which is most common in the homozygous (SS) disease and carries worse outcomes in adults than children. See Table 28.1 for common causes and triggers of acute chest syndrome.