RESPIRATORY EFFECTS OF MIDAZOLAM IN PATIENTS WITH OBSTRUCTIVE SLEEP-APNEA SYNDROME

The administration of benzodiazepines at sleeping doses can be followed by an increased rate of upper airways obstruction episodes, especially in patients with an obstructive sleep apnea syndrome (OSAS). However, the effects of benzodiazepines at premedication doses have not yet been assessed. Therefore, fourteen patients were studied after administration of midazolam 0.08 mg . kg-1 i.m. : seven with an OSAS diagnosed previously (baseline recording) (= OSAS group) and seven without risk factors for OSAS (= Control group). The recordings were undertaken in the sleep laboratory. The airflows were assessed by nasal and oral thermistors and chest and abdominal movements by strain gauges. The electromyogram of the chin muscles was recorded, the electroencephalogram and the electrooculogram electrodes were placed as described by RECHTSCHAFFEN and KALES. The arterial saturation in oxygen (Spo2) was monitored by pulse oximetry. All the signals were digitized and fed into a computer. The apnea was defined as a cessation of airflows for a least 10 s. The hypopnea was defined as a 10 s decrease in airflow with a drop in Spo2 of 4 % or more. The respiratory event (apnea or hypopnea) was qualified as obstructive if the thoraco-abdominal movements persisted. The rate and the duration of respiratory events per sleep hour (mean +/- SEM) in OSAS group after midazolam (respectively 29.6 +/- 10 and 11.2 +/- 3.5 min) were not different from those of the baseline recording (respectively 38.4 +/- 11.6 and 12 +/- 3.5 min) and were significantly higher than in the control group (respectively 3.8 +/- 2 and 1.8 +/- 1.3 min ; p < 0.05). In the OSAS group, the percentage of sleeping time spent with a Spo2 < 90 % was 1.5 +/- 1.4 % during the baseline recording and 4.7 +/- 1.9 % after midazolam (difference n.s.). However, a dramatic increase was observed in two patients. It is concluded that after midazolam 0.08 mg . kg-1 i.m., the obstruction of the upper airways is similar to that occurring during the spontaneous sleep in patients with mild OSAS. Nevertheless, individual data indicate that the monitoring of Spo2 is essential after premedication with benzodiazepines in such patients.