Interaction between postoperative shivering and hyperalgesia caused by high-dose remifentanil.

BACKGROUND: High-dose remifentanil-based anesthesia is associated with opioid-induced hyperalgesia (OIH) and postanesthetic shivering (PAS). These effects can be prevented by N-methyl-d-aspartate (NMDA) receptor antagonists. This study aimed to investigate correlations between OIH and PAS caused by high-dose remifentanil and the effects of low-dose ketamine on OIH and PAS. METHODS: Seventy-five patients scheduled for single-port laparoscopic gynecologic surgery were randomly allocated into three groups, each of which received intraoperative remifentanil: group L at 0.1 µg/kg/min; group H at 0.3 µg/kg/min; and group HK at 0.3 µg/kg/min plus 0.25 mg/kg ketamine just before incision, followed by a continuous infusion of 5 µg/kg/min ketamine until skin closure. RESULTS: PAS, postoperative tactile pain threshold, and the extent of hyperalgesia in group H were significantly different (P < 0.05) than in the other two groups. PAS was significantly correlated with OIH, including mechanically evoked pain such as postoperative tactile pain threshold (r = -0.529, P = 0.01) (r = -0.458, P = 0.021) and the extent of hyperalgesia (r = 0.537, P = 0.002) (r = 0.384, P = 0.031), respectively, in group H and group HK. Notably, both groups were treated with high-dose remifentanil. Tympanic membrane temperature, time to first postoperative analgesic requirement, postoperative pain scores, analgesic consumption, and cumulative patient-controlled analgesia volume containing morphine were comparable in all three groups. CONCLUSIONS: OIH, including the enhanced perception of pain, and PAS were both associated with high-dose remifentanil, were significantly correlated and were attenuated by a low dose of ketamine. This suggests that a common mechanism in part mediated through activation of the central glutamatergic system (e.g., NMDA receptors), underlies the two effects caused by high doses of remifentanil.

Effects of ramosetron and dexamethasone on postoperative nausea, vomiting, pain, and shivering in female patients undergoing thyroid surgery.

PURPOSE: Some antiemetics are effective in the treatment of postoperative pain and shivering, as well as for postoperative nausea and vomiting (PONV). The aim of this study was to investigate the effects of ramosetron and dexamethasone on PONV, pain, and shivering and to determine the correlations between nausea, pain, and shivering. METHODS: For this study, 123 patients scheduled for thyroid surgery were randomly allocated to one of three groups: the control group (group C, n = 41), dexamethasone group (group D, n = 41), or the ramosetron group (group R, n = 41). The patients were treated intravenously with 2 mL of 0.9 % NaCl, 2 mL of 5 mg/mL dexamethasone, or 2 mL of 0.15 mg/mL ramosetron immediately after anesthesia. RESULTS: The overall incidence and severity of postoperative nausea and the level of antiemetic consumption were significantly lower in group R compared with group D, and these parameters were significantly lower in groups R and D than in group C. There were significant differences in the incidence and severity of shivering, severity of pain, and analgesic consumption between group C and group R or D, but the incidence of shivering, pain severity, and analgesic consumption did not differ between groups R and D. The severity of shivering was significantly lower in group R than in group D. The correlation coefficients for shivering and pain, shivering and nausea, and pain and nausea were 0.210 (P = 0.010), 0.106 (P = 0.198), and 0.190 (P = 0.035), respectively, in group C. CONCLUSIONS: Two antiemetic drugs, ramosetron and dexamethasone, significantly reduced the incidence and severity of postoperative nausea and the need for administration of rescue antiemetic drugs. Furthermore, both drugs effectively decreased the severity of pain and shivering. Ramosetron was superior to dexamethasone for reducing nausea, antiemetic consumption, and the severity of nausea, but not for reducing the incidence of shivering. Further studies are required to elucidate the correlations between postoperative nausea, pain, and shivering, as a statistically significant but weak correlation was shown in the present study.

The effects of magnesium sulfate infiltration on perioperative opioid consumption and opioid-induced hyperalgesia in patients undergoing robot-assisted laparoscopic prostatectomy with remifentanil-based anesthesia.

BACKGROUND: Opioids not only exert an antinociceptive effect, but also modulate central N-methyl-D-aspartate (NMDA) receptors, resulting in hyperalgesia and acute opioid tolerance. This study was aimed to investigate the effect of the NMDA receptor antagonist, magnesium in preventing remifentanil-induced hyperalgesia. METHODS: For this study, 75 patients scheduled for robot-assisted laparoscopic prostatectomy were randomly allocated into three groups of patients whose incision sites were infiltrated: Group M, with 25% magnesium sulfate 80 mg/kg; Group S, with the same volume of saline under remifentanil-based anesthesia, and Group D, with the same volume of saline under desflurane based anesthesia. All three groups were infiltrated into incision sites after pneumoperitoneum. Intraoperative evaluation included mean remifentanil dose, and postoperative evaluation included pain severity at time intervals of 30 min, 6, 12, 24 and 36 hours, time to first postoperative analgesic requirement, and analgesic dosage required during 24 hours. RESULTS: Mean remifentanil doses during the intraoperative periods in group M were significantly lower than those in group S (P < 0.001). The time to first postoperative analgesic requirement in postoperative period in groups M and D was significantly longer than that in group S (P < 0.001). Visual analog scale scores for pain in groups M and D were significantly lower than those in group S for 12 hours after operation. CONCLUSIONS: A relatively high dose and continuous infusion of remifentanil were associated with opioid induced hyperalgesia. Wound infiltration with magnesium sulfate decreased opioid consumption and reduces opioid induced hyperalgesia.