Arterial Hypoxemia Syndrome in Sickle Cell Disease.

Acute chest syndrome (ACS) is the most common cause of death during hospitalization of adults with sickle cell disease (SCD). ACS includes symptoms referable to the chest and a new infiltrate on chest X-ray. Adults over age 20 years have more symptoms of the disease and are at increased risk of early death compared to children. ACS may be the presenting diagnosis for a patient with SCD, but equally as often, develops while the patient has a painful vascular occlusive crisis. Notably, 35% of SCD patients have a normal lung exam upon presentation to the hospital. Previous research studies indicate that nearly three-fourths of SCD patients who die present during painful crises in an extremity, and about 50% conclusively by autopsy died of massive fat embolism syndrome (FES). Unfortunately, definitive diagnostic tests with rapid turn-around for FES and other acute vascular occlusive lung events do not exist. Earlier identification of the danger that this event may be evolving can be life saving. Clinicians who adhere to the strict definition of ACS may prematurely dismiss the likelihood of a subsequent fatal event. This alarming rate of adverse events may represent a “pre-chest syndrome” prodromal phase of ACS. Arterial hypoxemia syndrome (AHS) or pre-chest syndrome is defined as any sign or symptom referable to the chest, an oxygen saturation (Sp02) of <94% by direct pulse oximeter or a Pa02 <80% by arterial blood gas on room air plus a clear chest X-ray with or without fever. AHS may be a warning sign of an ultimately fatal event if earlier interventions are not done in a timely manner. A secondary data analysis was performed utilizing 500 health records of SCD patients from 1960 to 2004. Prior to 2003, we averaged 2 to 3 ICU admissions per month for ACS with about 20% requiring mechanical ventilation. This study sought to gain insight on 45 years of experience in the treatment of SCD, particularly “pre-chest syndrome.” The primary aims of the study were to devise treatment protocols to reduce ICU admissions and the need for mechanical ventilation in SCD patients presenting with AHS. Retrospective analysis suggests that earlier blood exchanges for patients with SCD may substantially reduce ICU admissions and the need for mechanical ventilation in patients presenting with AHS, compared with patients receiving standard supportive care. Examination of computerized hospital records of 437 sickle cell hospital admissions from January 2003 to March 2005 revealed 3 ICU and 2 step-down unit admissions. During this time period, there were 101 chest syndrome occurrences, of which 2 died. Both patients required mechanical ventilation and underwent red cell apheresis to reduce hemoglobin S to <30%. One patient was admitted due to major trauma from a motor vehicle accident. Death was due to multi-organ failure. The medical condition of the second patient improved. This patient was discharged home in stable condition but died, unexpectedly, 48 hours at home of a massive pulmonary embolus. A protocol has been developed to prospectively evaluate our aims.