ASTHMA REQUIRING MECHANICAL VENTILATION - A LOW MORBIDITY APPROACH

Study objective: There is considerable uncertainty about the clinical features, respiratory physiology, and optimal management of patients w ith asthma requiring mechanical ventilation. Furthermore, the ventilat ory and pharmacologic management of asthma requiring mechanical ventil ation remain controversial. We hypothesized (1) that there are clinica lly identifiable and pathophysiologically different subgroups presenti ng with asthma requiring ventilation; (2) that lower dose steroid ther apy (< 400 mg/d intravenous hydrocortisone) is adequate; (3) that perm issive hypercapnia is safe; (4) that prolonged paralysis is generally unnecessary; and (5) that clinical outcome would be favorable in patie nts treated with this approach. Design: Review of medical records and intensive care charts and statistical analysis of findings. Setting: I CU of tertiary institution. Patients: Thirty-five consecutive cases of life-threatening asthma requiring mechanic ventilation. Results: Thre e clinical subgroups of ventilation-requiring asthmatics could be iden tified. Those presenting with steady deterioration (10), those with un stable asthma followed by a sudden ''dip'' (16), and those with a sudd en unexpected dip (9). Patients in the first group had a significantly lower PaCO2 (p<0.01) at presentation, but required ventilation for lo nger periods. Those in the second group had a significantly higher PaC O2 (p < 0.01) and required ventilation for a shorter period. Those in the third group had an intermediate PaCO2 level before intubation and the shortest period (p < 0.01) of mechanical ventilation. Five patient s experienced their sudden dip after ingesting aspirin. Ten cases rece ived ''high'' dose hydrocortisone therapy (mean: 980 mg/24 h), and 25 received lower dose hydrocortisone (mean: 341 mg/24 h). No differences in illness severity at presentation or outome could be detected betwe en these two groups. Mean duration of ventilatory support was 36 h and mean duration of the ICU stay 52.1 h. Muscle relaxation was used in 1 2 patients for a mean period of 11.1 h. One patient was brain dead on arrival. All others survived. Conclusions: Life threatening asthma is an endpoint for several different clinical patterns of disease. No maj or clinical advantage could be found in our group of patients when hig h-dose steroids were used. Longterm use of muscle relaxants and prolon ged mechanic ventilation are rarely needed in the management of patien ts with life-threatening asthma and excellent results can be achieved with a relatively simple management strategy.