It seems sensible to offer all patients this double prophylaxis as well as giving advice on what to do in the event of fevers, rigors, or other acute illness. During infection or other stress such as generalised illness, miscarriage etc the haemoglobin can rapidly fall to a dangerous level due to entrapment of red cells in the spleen or liver. The patient, normally rather protected against the symptoms of anaemia, develops acute lassitude and dyspnoea. The spleen or liver usually increases in size. The event can mimic pulmonary embolism or pneumonia with dyspnoea and respiratory distress associated with progressive hypoxaemia.
Shadows also occur on the chest x-ray.
Sickling can spread throughout all zones of the lungs and cause respiratory failure. Any patient with chest pain, dyspnoea or other forms of respiratory distress should be admitted to hospital urgently. Exchange transfusion may be required, as may assisted ventilation. This crisis mimics an intra-abdominal emergency such as appendicitis with pain in a girdle around the abdomen, sometimes accompanied by intensified jaundice and diffuse tenderness. Of course, the sickle cell patient is not immune to appendicitis or conventional intra-abdominal events.