A randomized, blind comparison of remifentanil and alfentanil during anesthesia for outpatient surgery.

UNLABELLED: We compared remifentanil, an esterase-metabolized opioid, with alfentanil as part of balanced anesthesia with at least 0.8% isoflurane during outpatient surgery in a randomized, double-blind trial. One hundred two patients received remifentanil, and 99 patients received alfentanil. Patients who received remifentanil experienced significantly fewer stress responses to surgical stimuli (52.9% and 65.7%, P < 0.05); significantly fewer remifentanil patients responded to skin closure (11% and 22%, P < 0.05) than patients who received alfentanil. Significantly more patients in the alfentanil group required extra analgesia compared with the remifentanil group (P < 0.05). Time to respond to verbal command was shorter for alfentanil than remifentanil (median 7 min vs 9 min), and times to spontaneous respiration (median 5 min vs 8 min), adequate respiratory rate (median 6 min vs 9 min), and tracheal extubation (median 6 min vs 9 min) were significantly shorter for alfentanil in comparison with remifentanil (P < 0.05). Remifentanil patients, however, showed significantly better recovery of psychomotor and psychometric function between 30 and 90 min after surgery (P < 0.05). The incidences of hypotension intraoperatively and shivering postoperatively were significantly higher with remifentanil. No unexpected or serious adverse events were recorded with remifentanil; however, one patient who received alfentanil experienced severe recurrent respiratory depression after surgery. The metabolic profile of remifentanil allowed better intraoperative analgesia without compromising recovery. IMPLICATIONS: The pharmacological profile of remifentanil, a new opioid for use in anesthesia, suggests that rapid recovery will occur after its use. This study of 200 outpatients shows that the differences suggested from kinetic studies are not always borne out in clinical practice, although later recovery variables did, in fact, favor remifentanil.

The effect of different end-tidal volatile agent and carbon dioxide concentrations upon the incidence of postoperative shivering.

Sixty patients (47 female) undergoing surgical excision of three or more wisdom teeth were randomly allocated into three groups with differing end-tidal carbon dioxide and volatile agent concentrations during maintenance of anaesthesia. The anaesthetic techniques employed were identical in all other respects. All patients were observed for 10 min after arrival in the recovery area to assess the presence and severity of shivering, axillary temperature and oxygen saturation. There were no significant differences in axillary temperatures between groups or between shivering and non-shivering patients, although there was a significant difference (p = 0.001) in duration of anaesthesia between shivering and non-shivering patients. There was no significant difference between groups with respect to the incidence of shivering (p = 0.96).

A comparison of thiopentone and propofol with respect to the incidence of postoperative shivering.

One hundred patients (69 female) undergoing surgical excision of three or more wisdom teeth were randomly allocated to receive either thiopentone or propofol for induction of anaesthesia. Other than the induction agent, the anaesthetic regimen was standardised for all cases. All patients were observed for 15 min after entry into the recovery area to assess the presence and intensity of shivering. Twenty-five patients in the thiopentone group (n = 50) and 11 patients in the propofol group shivered postoperatively (p < 0.005). There was no statistically significant difference in axillary temperature between shivering and non-shivering patients. The use of propofol as an induction agent is associated with a lower incidence of postoperative shivering than thiopentone.

Inspired oxygen concentration during general anaesthesia for caesarean section.

The effects on maternal oxygen saturation, foetal wellbeing and umbilical blood gases were compared when parturients received either 30 or 50% oxygen prior to delivery by Caesarean section under general anaesthesia. Maternal arterial oxygen saturation was significantly increased in the group receiving 50% oxygen. There was no difference between the two groups in terms of Apgar score minus colour, time to sustained respiration or umbilical cord blood gas estimations. The use of 30% inspired oxygen during uncomplicated Caesarean section is advocated.

Placental transfer of alfentanil at caesarean section.

Twenty-one women about to undergo elective Caesarean section were given intravenous alfentanil 10 micrograms kg-1 1 min prior to induction of anaesthesia in order to obtund the pressor response to laryngoscopy and endotracheal intubation. Compared with a control group of 16 patients, alfentanil significantly reduced the pressor response to endotracheal intubation (P less than 0.01), without any detectable adverse effect upon the neonate. At delivery, mean maternal alfentanil plasma concentration was 23.5 ng ml-1 (SD 7.5, range 9.8-41.2 ng ml-1) and the mean maternal venous plasma alpha 1-acid glycoprotein (alpha 1-AGP) was 576 mg l-1 (SD 208, range 230-1200 mg l-1). Mean neonatal umbilical venous alfentanil plasma concentration was 7.5 ng ml-1 (SD 1.8, range 3.6-10.6 ng ml-1), while the mean umbilical venous alpha 1-AGP concentration was 189 mg l-1 (SD 76, range 80-410 mg l-1). At delivery, the calculated unbound maternal and foetal plasma alfentanil concentrations were similar.

A multicentre trial in spontaneously breathing patients. A comparison of recovery following alfentanil or enflurane.

Recovery from anesthesia and the effect of premedication, induction agent and the individual anesthetist on the measure of recovery was assessed in 707 patients scheduled to undergo short surgical procedures. Patients were randomly allocated to receive either alfentanil or enflurane as a supplement to an induction agent, nitrous oxide/oxygen anesthetic technique with or without premedication. Patients who received alfentanil had a faster immediate recovery than those who received enflurane (p less than 0.001). Total anesthetic time was shorter in the alfentanil group (p = 0.02). For 36 of 37 anesthetists recovery was faster in the alfentanil group compared to the enflurane group. Choice of premedication and induction agent had a significant effect on recovery, thiopentone or lorazepam prolonged recovery time in each group. Although the alfentanil group had a higher incidence of apnoea, movement and vomiting (p less than 0.001), the enflurane group had a higher incidence of coughing (p less than 0.001) and shivering (p = 0.004). Overall the anesthetists assessed the alfentanil technique as excellent or good in more patients than the enflurane technique.

Maternal and neonatal responses to alfentanil administered before induction of general anaesthesia for caesarean section.

The cardiovascular response to tracheal intubation was compared in two groups of patients undergoing elective Caesarean section. Both groups received a standard technique of general anaesthesia. One of the groups received alfentanil 10 micrograms kg-1 1 min before induction of anaesthesia, the other acted as a control group. In the alfentanil group there was a significant modification of the cardiovascular response to intubation as compared with the control group (P less than 0.01). No adverse effect on the neonate was seen. However, a significant increase in the incidence of postoperative nausea occurred in mothers in the alfentanil group (P less than 0.05).

Recovery after anaesthesia with alfentanil or halothane.

Seventy-three patients were studied during and after anaesthesia with either alfentanil or halothane for surgical procedures of short duration. The procedures were minor gynaecological or minor urological procedures, involving males and females between the ages of 21 and 86 years. After pre-medication with lorazepam, anaesthesia was induced with methohexitone and continued with nitrous oxide and oxygen, supplemented with halothane (34 patients) or alfentanil (39 patients). Anaesthesia was generally smooth and uncomplicated except that at induction 22 of the patients receiving alfentanil became apnoeic for longer than 30 seconds. Spontaneous respiration resumed without the need for naloxone in any patients. After surgery, recovery of consciousness was significantly more rapid after alfentanil than after halothane (5.6 minutes versus 10.1 minutes). This study demonstrates that alfentanil can be a suitable alternative to conventional general anaesthesia for short cases and may have a useful place when rapid recovery and turnover of cases is important.