Incidence of postoperative shivering comparing remifentanil with other opioids: a meta-analysis.

STUDY OBJECTIVE: To determine whether the administration of remifentanil increases the incidence of postoperative shivering in comparison with the administration of alfentanil, fentanyl, or sufentanil. DESIGN: Meta-analysis. SETTING: Operating room and postanesthesia care unit. MEASUREMENTS: We performed a computerized search of articles on PubMed, MEDLINE, and Scopus. Meta-analysis was performed using Review Manager and the DerSimonian and Laird random-effects model. The pooled effect estimates for binary variables were calculated as relative risk (RR) values with 95% confidence intervals (CIs). MAIN RESULTS: Eighteen randomized controlled trials met our inclusion criteria. Remifentanil was associated with a significantly increased incidence of postoperative shivering compared with other opioids (RR=2.17; CI, 1.76-2.68; P<.00001; I(2)=0.00%). A subgroup analysis of remifentanil compared with alfentanil, fentanyl, or sufentanil showed that only sufentanil had a similar rate of postoperative shivering incidence (RR=2.13; CI, 0.67-6.74; P=.20; I(2)=0.00%). Remifentanil administration was associated with a significant increase in the incidence of postoperative shivering compared with the administration of other opioids when both propofol (RR=2.44; CI, 1.52-3.92; P=.0002; I(2)=0.00%) and inhalation anesthesia drugs (RR=2.45; CI, 1.46-4.11; P=.0007; I(2)=0.00%) were used for anesthesia maintenance. In addition, the administration of remifentanil at both low (RR=2.06; CI, 1.63-2.60; P<.00001; I(2)=0.00%) and high dosages (RR=2.77; CI, 1.67-4.57; P<.0001; I(2)=0.00%) was associated with a significant increase in the incidence of postoperative shivering compared with the administration of other opioids. CONCLUSIONS: Our meta-analysis showed that remifentanil was associated with an increased incidence of postoperative shivering compared with alfentanil or fentanyl, but no significant difference was seen when compared with sufentanil.

Tissue blood flow reductions induced by remifentanil in rabbits and the effect of naloxone and phentolamine on these changes.

OBJECTIVES: The purpose of this study was to investigate the effects of naloxone and phentolamine on the blood flow changes in rabbit oral tissue induced by remifentanil during sevoflurane anesthesia. MATERIALS AND METHODS: Male Japan White rabbits were anesthetized with sevoflurane under mechanical ventilation. Remifentanil was continuously infused at a rate of 0.4 µg/kg/min. Naloxone 0.01 mg/kg or phentolamine 0.01 mg/kg was administered during remifentanil infusion. Observed variables were systolic and diastolic blood pressures, mean arterial pressure, heart rate, common carotid artery blood flow, tongue mucosal blood flow, mandibular bone marrow blood flow, masseter muscle blood flow, and upper and lower alveolar tissue blood flows. The common carotid artery blood flow was monitored continuously using an ultrasonic blood flowmeter. Tongue mucosal blood flow was monitored continuously using a laser Doppler blood flowmeter. Mandibular bone marrow blood flow, masseter muscle blood flow, and upper and lower alveolar tissue blood flows were measured using a hydrogen clearance tissue blood flowmeter. One-way analysis of variance for repeated measurements followed by the Student-Newman-Keuls test was used. RESULTS: Remifentanil produced decreases in the heart rate, systolic blood pressure, and common carotid artery blood flow by about 15% and mandibular bone marrow blood flow, masseter muscle blood flow, and upper and lower alveolar tissue blood flows by about 30%. In the naloxone group, all variables recovered after naloxone administration. In contrast, in the phentolamine group, tissue blood flow recovered, whereas heart rate, systolic blood pressure, and common carotid artery blood flow did not recover after phentolamine administration. CONCLUSIONS: Remifentanil deceased oral tissue blood flow and systemic hemodynamic variables. Naloxone and phentolamine produced a recovery of oral tissue blood flow with and without systemic hemodynamic recovery, respectively.