RESPIRATORY EFFECTS OF MIDAZOLAM IN PATIE NTS WITH OBSTRUCTIVE SLEEP-APNEA SYNDROME

The administration of benzodiazepines at sleeping doses can be followe d by an increased rate of upper airways obstruction episodes, especial ly in patients with an obstructive sleep apnea syndrome (OSAS). Howeve r, the effects of benzodiazepines at premedication doses have not yet been assessed. Therefore, fourteen patients were studied after adminis tration of midazolam 0.08 mg . kg-1 i.m. : seven with an OSAS diagnose d previously (baseline recording) (= OSAS group) and seven without ris k factors for OSAS (= Control group). The recordings were undertaken i n the sleep laboratory. The airflows were assessed by nasal and oral t hermistors and chest and abdominal movements by strain gauges. The ele ctromyogram of the chin muscles was recorded, the electroencephalogram and the electrooculogram electrodes were placed as described by RECHT SCHAFFEN and KALES. The arterial saturation in oxygen (Spo2) was monit ored 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 d rop in Spo2 of 4 % or more. The respiratory event (apnea or hypopnea) was qualified as obstructive if the thoraco-abdominal movements persis ted. The rate and the duration of respiratory events per sleep hour (m ean +/- SEM) in OSAS group after midazolam (respectively 29.6 +/- 10 a nd 11.2 +/- 3.5 min) were not different from those of the baseline rec ording (respectively 38.4 +/- 11.6 and 12 +/- 3.5 min) and were signif icantly 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 sleep ing time spent with a Spo2 < 90 % was 1.5 +/- 1.4 % during the baselin e recording and 4.7 +/- 1.9 % after midazolam (difference n.s.). Howev er, 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 t he monitoring of Spo2 is essential after premedication with benzodiaze pines in such patients.