Clinical considerations in the use of forced-air warming blankets during orthognathic surgery to avoid postanesthetic shivering

BACKGROUND: During head and neck surgery including orthognathic surgery, mild intraoperative hypothermia occurs frequently. Hypothermia is associated with postanesthetic shivering, which may increase the risk of other postoperative complications. To improve intraoperative thermoregulation, devices such as forced-air warming blankets can be applied. This study aimed to evaluate the effect of supplemental forced-air warming blankets in preventing postanesthetic shivering. METHODS: This retrospective study included 113 patients who underwent orthognathic surgery between March and September 2015. According to the active warming method utilized during surgery, patients were divided into two groups: Group W (n = 55), circulating-water mattress; and Group F (n = 58), circulating-water mattress and forced-air warming blanket. Surgical notes and anesthesia and recovery room records were evaluated. RESULTS: Initial axillary temperatures did not significantly differ between groups (Group W = 35.9 ± 0.7℃, Group F = 35.8 ± 0.6℃). However, at the end of surgery, the temperatures in Group W were significantly lower than those in Group F (35.2 ± 0.5℃ and 36.2 ± 0.5℃, respectively, P = 0.04). The average body temperatures in Groups W and F were, respectively, 35.9 ± 0.5℃ and 36.2 ± 0.5℃ (P = 0.0001). In Group W, 24 patients (43.6%) experienced postanesthetic shivering, while in Group F, only 12 (20.7%) patients required treatment for postanesthetic shivering (P = 0.009, odds ratio = 0.333, 95% confidence interval: 0.147-0.772). CONCLUSIONS: Additional use of forced-air warming blankets in orthognathic surgery was superior in maintaining normothermia and reduced the incidence of postanesthetic shivering.

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

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 microg/kg/min; group H at 0.3 microg/kg/min; and group HK at 0.3 microg/kg/min plus 0.25 mg/kg ketamine just before incision, followed by a continuous infusion of 5 microg/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.

Different dose and effects of dexmedetomidine in preventing shivering after general anesthesia for laparoscopic surgery / 实用医学杂志

Objective The aim of this study was to investigate different dosages and effects of dexmedetomidine for prevention of postanesthetic shivering. Methods One-hundred twenty patients scheduled for laparoscopic surgery were randomly allocated in four groups: before the operation, slowly injected 0.9% normal saline (group S, dexmedetomidine 0.5 μg/kg (group D0.5), dexmedetomidine 0.75 μg/kg (group D0.75), dexmedetomidine 1.0 μg/kg(group D1.0). HR and rectal temperature[C2] were continually monitered during and after operation, time to extubation was measured. Grades of shivering were recorded. Pain evaluation was assessed by a visual analogue scale, sedation was evaluated by Modified Observer′s Assessment of Alertness/Sedation scale. Results The patients in group S showed a significantly higher HR and postoperative incidence of shivering than those in group D0.75 and group D1.0, (P < 0.05). but the extubation time in groupd D0.75 and group D1.0 were longer than patients in group S (P<0.05). Conclusion Slowly injected dexmedetomidine 0.75 μg/kg or 1.0 μg/kg can prevent postanesthetic shivering in laparoscopic surgery effectively.

Effects of Clonidine on Postanesthetic Shivering When Administered Late Intraoperatively / 대한마취과학회지

BACKGROUND: Postoperative administration of clonidine is an effective treatment for shivering. However, the ability of this drug to stop postanesthetic shivering when administered intraoperatively remains controversial. Furthermore, the efficacy of clonidine during isoflurane and propofol/fentanyl anesthesia remains unknown. We therefore evaluated the incidence of postanesthetic shivering in patients given clonidine during isoflurane/N2O or propofol/fentanyl/N2O anesthesia. METHODS: Sixty patients scheduled for hysterectomy were divided into 4 groups (each group n = 15):(Group 1:isoflurane/clonidine; group 2:isoflurane/saline; group 3:propofol,fentanyl/clonidine; group 4:propofol,fentanyl/saline). The patients of groups 1 and 2 were anesthetized with N2O/O2/isoflurane and in group 3 and 4 with a continuous infusion of propofol (5 10 mg/kg), fentanyl (0.5 microgram/kg) and N2O. Five minutes before tracheal extubation, patients in each group were randomly assigned to receive saline or 2.5 microgram/kg clonidine intravenously. Postanesthetic shivering was evaluated by a blind investigator. We checked mean arterial pressure, pulse, rectal temperature at baseline, immediately after extubation, and subsequently at 5 min intervals for 60 min. RESULTS: Postoperative shivering was observed in 33% of the patients given isoflurane without clonidine and in 13% of the patients given propofol without clonidine (p < 0.05). No patient given clonidine shivered. The incidence of postanesthetic shivering was less after propofol anesthesia than after isofurane/ N2O anesthesia. Clonidine administration 5 minutes before tracheal extubation improved hemodynamic changes without respiratory depression. CONCLUSIONS: A late intraoperative bolus adminstration of 2.5 microgram/kg clonidine prevents postoperative shivering in patients given either type of anesthesia.

A Comparison of Effectiveness Correlated with Different Doses of Doxapram in the Treatment of Post-Anesthetic Shivering / 대한마취과학회지

BACKGROUND: Although post-anesthetic shivering may be a temporary phenomenon, it leads to detrimental effects such as increased oxygen consumption, hypoxemia, and difficulty in monitoring. Doxapram is a relatively new treatment for post-anesthetic shivering, but there have been few reports about its minimum effective dose. The purpose of this study was to find the minimum dose of doxapram which would show an antishivering effect. METHODS: Sixty patients who had developed post-anesthetic shivering were divided into six groups of ten patients each. The groups were divided into a control group, which received normal saline, and the doxapram groups, which received five different doses of doxapram (0.15, 0.2, 0.5, 1.0, 1.5 mg/kg). The antishivering effect (2, 5, 10, 15 minutes after treatment), blood pressure, heart rate and temperature were compared among the groups. RESULTS: There was a significant difference in antishivering effect between the group which received normal saline and the groups which received doxapram; however, there was no significant difference within the groups which received doxapram. CONCLUSIONS: We conclude that the dose of doxapram required to achieve an antishivering effect is much less than that currently in use.