RESTLESSNESS AND SHIVERING AFTER NALOXONE REVERSAL OF FENTANYL-SUPPLEMENTED ANESTHESIA

To study the significance of normalization of ventilatory or thermal homeostasis during naloxone reversal, 95 patients were given naloxone after thiopental‐N2O‐O2‐relaxant anaesthesia supplemented with fentanyl (6 μg/kg/h). If naloxone 0.16 mg was given to combat postoperative apnoea during hypercapnia (end tidal carbon dioxide concentration (ETco2) 8%), minute ventilation and respiratory rate were significantly higher during the first minutes as compared to the normo‐capnic patients. Shivering occurred in 44% in the hypercapnic group, as compared to about 30% if naloxone was given during normocapnia (ETco2 5%). Postoperative pain and restlessness were significantly increased in the hypercapnic group. During normocapnia, untoward reactions were less frequent (40%) if naloxone was given in smaller increments (0.08+0.08 mg) rather than in one dose (0.16 mg) (72%). This was mainly due to nausea (8% compared to 32%). The incidence and severity of shivering showed a positive correlation to the duration of anaesthesia (r = 0.42) and to the total amount of fentanyl (r = 0.32), but not to the actual postoperative oesophageal temperature (r=—0.13). The results indicate that though untoward reactions after naloxone reversal are aggravated by naloxone‐induced normalization of deranged homeostatic mechanisms, their aetiology probably should be sought in an acute abstinence syndrome. © 1979 Acta Anaesthesiologica Scandinavica Fonden