No hyperalgesia following opioid withdrawal after the oripavine derivative etorphine compared to remifentanil and sufentanil:

Determination of acute tolerance and hyperalgesia to remifentanil constant rate infusion in dogs undergoing sevoflurane anaesthesia

OBJECTIVE

To determine if acute opioid tolerance (AOT) or opioid-induced hyperalgesia (OIH) could develop and limit the remifentanil-induced reduction in the sevoflurane minimum alveolar concentration (MAC). The response to mechanical nociceptive threshold (MNT) was evaluated and related to OIH.

STUDY DESIGN

A crossover, randomized, experimental animal study.

ANIMALS

A total of nine Beagle dogs.

METHODS

The dogs were anaesthetized with sevoflurane in 50% oxygen. Baseline sevoflurane MAC was measured (MACb1). Remifentanil (0.3 μg kg^-1 minute^-1) or 0.9% saline constant rate infusion (CRI) was administered intravenously (IV). Sevoflurane MAC was determined 20 minutes after CRI was initiated (MACpostdrug1), 30 minutes after MACpostdrug1 determination (MACpostdrug2) and after 1 week (MACb2). The MNT was determined at baseline (before anaesthesia), 3 and 7 days after anaesthesia. An increase of MACpostdrug2 ≥0.25% compared to MACpostdrug1 was considered evidence of AOT. A decrease in MNT at 3 and 7 days or an increase in MACb2 or both with respect to MACb1 were considered evidence of OIH.

RESULTS

Remifentanil CRI reduced sevoflurane MACpostdrug1 by 43.7% with respect to MACb1. MACpostdrug2 was no different from MACpostdrug1 with the saline (p = 0.62) or remifentanil (p = 0.78) treatments. No significant differences were observed in the saline (p = 0.99) or remifentanil (p = 0.99) treatments between MACb1 and MACb2, or for MNT values between baseline, 3 and 7 days.

CONCLUSION AND CLINICAL RELEVANCE

In dogs, under the study conditions, remifentanil efficacy in reducing sevoflurane MAC did not diminish in the short term, suggesting remifentanil did not induce AOT. Hyperalgesia was not detected 3 or 7 days after the administration of remifentanil. Contrary to data from humans and rodents, development of AOT or OIH in dogs is not supported by the findings of this study.

Asleep-awake-asleep technique in children during strabismus surgery under sufentanil balanced anesthesia

BACKGROUND

Both over- and undercorrection can occur in up to 10-15% of strabismus surgeries. Use of adjustable suture technique and an intraoperative awake test may decrease the incidence of over- or undercorrection. In this study, we investigated the ability to provide optimal conditions for intraoperative awake strabismus suture adjustment in children by means of target-controlled infusions (TCI) of propofol and remifentanil propofol compared with propofol and sufentanil.

METHODS

Forty-six ASA I-II patients undergoing strabismus surgery with intraoperative awakening were randomly assigned to anesthesia by TCI of propofol + sufentanil group (group SF) or propofol + remifentanil spontaneous breathing. Propofol was discontinued, and concentrations of the opioid TCIs were reduced to enable awake assessment of the mobility and position of the eye. Changes in intraocular pressure, respiratory function, hemodynamics, awakening time, and awaking quality were compared between the two groups. The degrees of sedation and analgesia were evaluated through the assessment of alertness and sedation scores (OAA/S) and visual analog scale scores (VAS).

RESULTS

There was no significant difference in intraocular pressure at three sampling points between two groups (P > 0.05). The heart rate (HR) and mean arterial blood pressure (MAP) in group SF were significantly lower than group RF during laryngeal mask insertion (P < 0.05) as well as during the wake-up test (P < 0.05). Spontaneous breathing was maintained in all patients, and there was no significant difference in RR and Sp02 at T1-T11 between the groups (P > 0.05). There was no significant difference in the target effect-site concentration of propofol at T1-T10 between the groups (P > 0.05). The wake-up times in group SF were significantly longer than in group RF (P < 0.05). In contrast, the quality of wake-up test and the degree of consciousness after the patients were awakened were significantly better (19 good and 4 satisfactory vs 15 good, 2 satisfactory, and 6 poor) in SF group than RF group. The VAS was significantly lower at T6-T9 in SF group than in RF group (P < 0.05). The incidence of untoward events during and after surgery, such as respiratory depression and apnea, oculocardiac reflex, coughing, groan and nausea, and vomiting was not significantly different between the groups (P > 0.05).

CONCLUSION

Propofol combined with sufentanil or remifentanil can be suitable for planned intraoperative awakening for an adjustable suture technique in pediatric patients during strabismus surgery. Remifentanil has quicker wake-up time; however, sufentanil demonstrated an advantage in terms of better analgesia, more stable hemodynamics, and improved qualify of awakening.