Pharmacological treatment of postoperative shivering: a quantitative systematic review of randomized controlled trials.

Shivering is a frequent complication in the postoperative period. The relative efficacy of interventions that are used for the treatment of postoperative shivering is not well understood. We performed a systematic search (MEDLINE, EMBASE, Cochrane Library, hand searching, all languages, to August, 2000) for full reports of randomized comparisons of any pharmacological antishivering intervention (active) with placebo (control) in the postoperative period. Dichotomous data on absence of further shivering after treatment and adverse effects were extracted from original reports. Relative risk (RR) and number-needed-to-treat (NNT) were calculated with 95% confidence interval (CI) using a fixed effect model. Data from 20 trials (944 adults received an active intervention, 413 were controls) were analyzed. Antishivering efficacy depended on the active regimen and the length of follow-up. Efficacy with meperidine 25 mg, clonidine 150 microg, ketanserin 10 mg, and doxapram 100 mg was reported in at least three trials; all were significantly more effective than control. After 1 min, the NNT of meperidine 25 mg for no further shivering compared with placebo was 2.7 (RR, 6.8; 95% CI, 2.5-18.5). After 5 min, the NNT of meperidine 25 mg was 1.3 (RR, 9.6; 95% CI, 5.7-16), the NNT of clonidine 150 microg was 1.3 (RR, 6.8; 95% CI, 3.3-14.2), the NNT of doxapram 100 mg was 1.7 (RR 4.0; 95% CI, 2.4-6.5), and the NNT of ketanserin 10 mg was 2.3 (RR 3.1; 95% CI, 1.9-5.1). After 10 min, the NNT of meperidine 25 mg was 1.5 (RR 4.0; 95% CI, 2.5-6.2). After 15 min, the NNT of ketanserin 10 mg was 3.3 (RR 1.5; 95% CI, 1.2-1.9). Long-term outcome data were lacking. There were not enough data for alfentanil, fentanyl, morphine, nalbuphine, lidocaine, magnesium, metamizol, methylphenidate, nefopam, pentazocine, and tramadol to draw meaningful conclusions. Reporting of adverse drug reactions was sparse. Fewer than two shivering patients need to be treated with meperidine 25 mg, clonidine 150 microg, or doxapram 100 mg for one to stop shivering within 5 min who would have continued to shiver had they all received a placebo. IMPLICATIONS: Less than two shivering patients need to be treated with meperidine 25 mg, clonidine 150 microg, or doxapram 100 mg for one to stop shivering within 5 min who would have continued to shiver had they all received a placebo.     

Control of post anaesthetic shivering with nefopam hydrochloride in mildly hypothermic patients after neurosurgery

Postoperative shivering may be prevented by maintaining normothermia intraoperatively or it may be treated using specific drugs. The aim of this study was to compare the efficacy of nefopam hydrochloride (nefopam) to that of clonidine and meperidine in patients undergoing elective neurosurgical procedures. Three groups of patients were included in the study. Patients in group A (60) received i.v., at random, 20 mg of nefopam, 50 mg of meperidine or 150 μg of clonidine in the immediate postoperative period. The incidence of shivering and the time at which shivering ceased were noted, along with central temperature and main haemodynamic changes. Group B (20) received i.v., at random, either 10 mg of nefopam or saline before awakening from anaesthesia. The effects of nefopam on central temperature, oxygen consumption (Vo₂), carbon dioxide production (VcO₂), basal metabolic rate (BMR) and energy expenditure (EE) were investigated. Group C (10) received i.v. 20 mg of nefopam during surgery: cerebrospinal fluid pressure (CSFP), cerebral perfusion pressure (CPP) and electroencephalogram (EEG) were monitored. In group A nefopam stopped shivering in 95% of patients when compared to meperidine and clonidine, which were effective in 32% and 40% of patients respectively. In group B, only 10% of patients receiving nefopam had postoperative shivering, Vo2, VcO2 and EE were significantly lower in patients treated with nefopam than those in the control group. No changes in CSFP, CPP or EEG were observed in group C. In conclusion, nefopam seems to be more effective than clonidine or meperidine in quickly suppressing shivering, without producing significant adverse reactions.     

A comparison of tramadol, amitriptyline, and meperidine for postepidural anesthetic shivering in parturients.

Tramadol is effective for treating shivering during epidural anesthesia in parturients. In addition to its low affinity to opioid receptors, tramadol exerts a modulatory effect on central monoaminergic pathways. In this respect, there are parallels between the mechanisms of the action of tramadol and antidepressants such as amitriptyline. Meperidine is often recommended for the treatment of postanesthetic shivering. This prospective, double-blinded, and randomized clinical study was performed to compare the antishivering effects and accompanying side effects among tramadol, meperidine, and amitriptyline for the treatment of postepidural anesthetic shivering. Forty-five parturients who shivered during cesarean delivery under epidural anesthesia and requested antishivering treatment were randomly allocated to one of three groups for IV treatment: Group T (n = 15) received tramadol 0.5 mg/kg, Group M (n = 15) received meperidine 0.5 mg/kg, and Group A (n = 15) received amitriptyline 15 or 20 mg. The response rate (shivering ceased after treatment in 15 min) was 87% and 93% for Groups T and M, respectively, compared with 13% in Group A (P < 0.01). The time that elapsed from treatment to the time shivering ceased was 5.1 +/- 3.6 min (mean +/- SD) for Group T and 4.2 +/- 2.3 min for Group M. There was a significantly more frequent incidence (33%) of somnolence in Group M when compared with Groups T (7%) and A (0%) (P < 0.01). However, no significant differences were shown for pruritus, nausea, vomiting, or Apgar scores of newborns. We concluded that both tramadol and meperidine show a significantly faster response rate in the treatment of postepidural anesthetic shivering when compared with amitriptyline in the dosage used; tramadol had a decreased incidence of somnolence when compared with meperidine. IMPLICATIONS: This study was performed to compare the antishivering and side effects among tramadol, amitriptyline, and meperidine for the treatment of postepidural anesthetic shivering in parturients. Both tramadol and meperidine show a significantly faster response rate in the treatment of shivering when compared with amitriptyline. Tramadol had a less frequent incidence of somnolence than meperidine.     

A comparison of urapidil, clonidine, meperidine and placebo in preventing postanesthetic shivering

This placebo-controlled study was performed to evaluate the efficacy of urapidil compared with clonidine and meperidine in preventing postanesthetic shivering, which is common after anesthesia administration and may be very distressing. We studied 120 patients undergoing elective abdominal or orthopedic surgery under standardized general anesthesia. After surgery, patients were randomly assigned to one of four groups (each group n = 30) using a double-blinded protocol: Group A received 0.2 mg/kg urapidil; Group B, 3 microg/kg clonidine; Group C, 0.4 mg/kg meperidine; and Group D, saline 0.9% as placebo. Postanesthetic shivering was scored by using a five-point scale. Clonidine and meperidine significantly reduced the incidence and the severity of shivering in comparison with placebo, whereas there were no significant differences between the urapidil and placebo groups. Both clonidine and meperidine caused a significantly prolonged emergence time (13.4 +/- 5.8 and 13. 3 +/- 5.0 min, respectively) compared with placebo (10.4 +/- 5.3 min) and urapidil (11.4 +/- 2.9 min). We confirmed that both clonidine and meperidine are effective in preventing postanesthetic shivering, whereas urapidil, in our setting and dosage, was not effective. Patients who received clonidine or meperidine had a prolonged emergence time. In the dosage used, urapidil seems to be unable to prevent postanesthetic shivering. IMPLICATIONS: Shivering (irregular muscle activity) is common after surgery and anesthesia. This study compared urapidil (an antihypertensive drug) as a prophylaxis with two established antishivering drugs (meperidine and clonidine) and placebo. In the dosage used, we were unable to show a significant benefit of urapidil.     

Nefopam and tramadol for the prevention of shivering during neuraxial anesthesia

BACKGROUND AND OBJECTIVES: In patients undergoing neuraxial anesthesia, heat loss and core-to-peripheral redistribution of body heat causes the core temperature to decrease. The shivering threshold is therefore reached soon, and more shivering is required to prevent further hypothermia. Because shivering has deleterious metabolic and cardiovascular effects, it should ideally be prevented by pharmacologic or other means. We evaluated the usefulness of intravenous (IV) nefopam and tramadol in preventing and reducing the severity of shivering in patients undergoing neuraxial anesthesia for orthopedic surgery. METHODS: Ninety patients, scheduled for neuraxial anesthesia (epidural or subarachnoid) for lower limb orthopedic surgery, were prospectively enrolled. Patients were randomly assigned to 1 of 3 groups. Immediately before neuraxial anesthesia, 30 patients received 0.15 mg/kg(-1) IV nefopam in 10 mL saline, 30 patients received 0.5 mg/kg(-1) IV tramadol in 10 mL saline, and a control group of 30 patients received 10 mL IV saline. Neuraxial anesthesia was induced at the L3-L4 or L4-L5 interspaces with 1 mg/kg(-1) mepivacaine for epidural anesthesia and 0.2 mg/kg(-1) for subarachnoid anesthesia. An investigator blinded to the antishivering drug injected recorded the frequency and degree of shivering. RESULTS: The overall frequency and the intensity of shivering was significantly lower in patients treated with nefopam than in those treated with tramadol or placebo (P <.05 and P <.01) and in patients treated with tramadol than in those treated with placebo (P <.05). CONCLUSIONS: As a pharmacologic means of preventing shivering in patients undergoing neuraxial anesthesia, nefopam may hold the greatest promise.     

A comparison of nefopam and clonidine for the prevention of postanaesthetic shivering: a comparative, double-blind and placebo-controlled dose-ranging study

Postanaesthetic shivering is a frequent complication following general anaesthesia. The aim of this study was to compare the effectiveness of three doses of nefopam with clonidine and placebo in the prevention of postanaesthetic shivering. We studied 371 patients undergoing abdominal or orthopaedic surgery. Patients were allocated to one of five groups: Group A (n = 73) received 0.2 mg x kg(-1) nefopam, Group B (n = 75) 0.1 mg x kg(-1) nefopam, Group C (n = 76) 0.05 mg x kg(-1) nefopam, Group D (n = 73) 1.5 microg x kg(-1) clonidine, and Group E (n = 74) saline 0.9% as placebo. We found a significant reduction in the incidence of shivering in Group A compared to Group C and clonidine as well as to the placebo group. All active treatments reduced the incidence and the severity of shivering compared to placebo. At 5 min postoperatively clonidine-treated patients showed a significant decrease in MAP and a significantly lower Aldrete score compared to all other groups. No haemodynamic or sedative adverse events were observed in the nefopam-treated patients. The results of our study indicate that nefopam (0.2 mg x kg(-1)) is superior to clonidine (1.5 microg x kg(-1)) in the prophylaxis of postanaesthetic shivering and not accompanied by sedative or haemodynamic side-effects.     

Nefopam for the prevention of postoperative pain: quantitative systematic review

Nefopam, a centrally acting analgesic, has been used in the surgical setting in many countries since the mid-1970s. However, clinical trials provide contflicting results for its analgesic potency. We performed a systematic search (multiple databases, bibliographies, any language, to January 2008) for randomized, placebo-controlled trials of nefopam for the prevention of postoperative pain. Data were combined using classic methods of meta-analyses and were expressed as weighted mean difference (WMD), relative risk (RR), and number needed to treat/harm (NNT/H) with 95% confidence interval (CI). Nine trials (847 adult patients, 359 received nefopam) were included. Nefopam (cumulative doses, 20-160 mg) was given orally or i.v., as single or multiple doses, or as a continuous infusion. Compared with placebo, cumulative 24 h morphine consumption was decreased with nefopam: WMD -13 mg (95% CI -17.9 to -8.15). Pain intensity at 24 h was also decreased: on a 100 mm visual analogue scale, WMD -11.5 mm (95% CI -15.1 to -7.85). The incidence of tachycardia was increased with nefopam (RR 3.12, 95% CI 1.11-8.79; NNH 7), as was the incidence of sweating (RR 4.92, 95% CI 2.0-12.1; NNH 13). There is limited evidence from the published literature that nefopam may be a useful non-opioid analgesic in surgical patients. The analgesic potency seems to be similar to non-steroidal anti-inflammatory drugs. However, dose responsiveness and adverse effect profile remain unclear, and the role of nefopam as part of multimodal analgesia needs to be established. Data in children are lacking.     

Neither nalbuphine nor atropine possess special antishivering activity

The special antishivering action of meperidine may be mediated by its kappa or anticholinergic actions. We therefore tested the hypotheses that nalbuphine or atropine decreases the shivering threshold more than the vasoconstriction threshold. Eight volunteers were each evaluated on four separate study days: 1) control (no drug), 2) small-dose nalbuphine (0.2 microg/mL), 3) large-dose nalbuphine (0.4 microg/mL), and 4) atropine (1-mg bolus and 0.5 mg/h). Body temperature was increased until the patient sweated and then decreased until the patient shivered. Nalbuphine produced concentration-dependent decreases (mean +/- SD) in the sweating (-2.5 +/- 1.7 degrees C. microg(-1). mL; r(2) = 0.75 +/- 0.25), vasoconstriction (-2.6 +/- 1.7 degrees C. microg(-1). mL; r(2) = 0.75 +/- 0.25), and shivering (-2.8 +/- 1.7 degrees C. microg(-1). mL; r(2) = 0.79 +/- 0.23) thresholds. Atropine significantly increased the thresholds for sweating (1.0 degrees C +/- 0.4 degrees C), vasoconstriction (0.9 degrees C +/- 0.3 degrees C), and shivering (0.7 degrees C +/- 0.3 degrees C). Nalbuphine reduced the vasoconstriction and shivering thresholds comparably. This differs markedly from meperidine, which impairs shivering twice as much as vasoconstriction. Atropine increased all thresholds and would thus be expected to facilitate shivering. Our results thus fail to support the theory that activation of kappa-opioid or central anticholinergic receptors contribute to meperidine's special antishivering action.     

Nefopam or clonidine in the pharmacologic prevention of shivering in patients undergoing conscious sedation for interventional neuroradiology

The aim of this randomised, double-blind study was to investigate the usefulness of intravenous nefopam, clonidine or placebo in preventing shivering in patients undergoing conscious sedation for interventional neuroradiological procedures. A total of 101 patients were prospectively enrolled and assigned to one of three groups to receive nefopam, clonidine or placebo. The overall incidence of intra-operative shivering was significantly lower in patients treated with nefopam than in those treated with clonidine or placebo (2/32 (6%) vs. 11/38 (29%), p < 0.02; 2/32 (6%) vs. 24/31 (77%), p < 0.0001, respectively). The number of patients who required ephedrine infusions to maintain a mean arterial pressure of 100 mm Hg was higher in the clonidine group than in the nefopam and placebo groups (18/38 (47%) vs. 5/32 (17%), p < 0.05; 18/38 (47%) vs. 6/31 (19%), p < 0.05, respectively). We found that both nefopam and clonidine significantly lowered the rate and severity of shivering during interventional neuroradiological procedures. Fewer patients in the nefopam group than in the other two groups required vasoactive drugs.     

Nefopam and clonidine in the prevention of postanaesthetic shivering

Postanaesthetic shivering affects up to 70% of patients after general anaesthesia, and may be very distressing. Various drugs have been used to treat or prevent postanaesthetic shivering, but the ideal one has not yet been found. Sixty patients undergoing elective abdominal or orthopaedic surgery under general anaesthesia were included in a randomised, double-blind study. Patients received clonidine (3 microgram.kg-1), nefopam (0.15 mg.kg-1) or saline 0.9% as a placebo at the end of surgery, prior to extubation. Nefopam and clonidine significantly reduced the incidence and severity of shivering in comparison with the placebo. The recovery time, between the end of anaesthesia and extubation, was significantly longer in the clonidine-treated patients [13.6 (5.2) min] than in either the nefopam [9.6 (2.8) min] or the placebo [10.0 (5.4) min] groups. Mean arterial blood pressure and heart rate were significantly lower in the clonidine group compared with both other groups. Our results suggest that nefopam and clonidine are effective in the prevention of postanaesthetic shivering. However, following clonidine administration the recovery time was prolonged and hypotension was significantly greater than after nefopam.     

Pharmacologic myocardial protection in patients undergoing noncardiac surgery: a quantitative systematic review

A number of drugs have been tested in clinical trials to decrease cardiac complications in patients undergoing noncardiac surgery. To compare the results of these studies, we conducted a quantitative systematic review. Medline, Embase, and Cochrane databases were searched for randomized trials that assessed myocardial ischemia, myocardial infarction, 30-day cardiac mortality, and adverse effects. Data were combined using a fixed-effect model and expressed as Peto odds ratios (OR) with 95% confidence interval (CI) and as numbers-needed-to-treat/harm (NNT/H). Twenty-one trials involving 3646 patients were included: 11 trials using beta-blockers (6 drugs; 866 patients), 6 clonidine or mivazerol (614 patients), 3 diltiazem or verapamil (121 patients), and 1 nitroglycerin (45 patients). All trials had an inactive control; there were no direct comparisons. beta-blockers decreased ischemic episodes during surgery (7.6% versus 20.2% with placebo; OR 0.32 [95% CI, 0.17-0.58]; NNT 8) and after surgery (15.2% versus 27.9% with control; OR 0.46 [95% CI, 0.26-0.81]; NNT 8). alpha(2)-agonists decreased ischemia during surgery only (19.4% versus 32.8%; OR 0.47 [95% CI, 0.33-0.68]; NNT 7). beta-blockers reduced the risk of myocardial infarction (0.9% versus 5.2%; OR 0.19 [95% CI, 0.08-0.48]; NNT 23) but only when 2 trials with high-risk patients were included. The effect of alpha(2)-agonists on myocardial infarction was not significant (6.1% versus 7.3%; OR 0.85 [95% CI, 0.62-1.14]). beta-blockers significantly decreased the risk of cardiac death from 3.9% to 0.8% (OR 0.25 [95% CI, 0.09-0.73], NNT 32). alpha(2)-agonists significantly decreased the risk of cardiac death from 2.3% to 1.1% (OR 0.50 [95% CI, 0.28-0.91], NNT 83). For calcium channel blockers and nitroglycerin, evidence of any benefit was lacking. The most common adverse effect was bradycardia, which occurred in 24.5% of patients receiving a beta adrenergic blocker versus 9.1% of controls (OR 3.76 [95% CI, 2.45-5.77], NNH 6).     

Dolasetron for preventing postanesthetic shivering.

We designed this study to assess the efficacy of dolasetron compared with clonidine and placebo in prophylaxis of postanesthetic shivering. We included 90 patients undergoing elective abdominal or urologic surgery. The patients were randomly assigned to one three groups (each group n = 30) using a double-blinded study protocol: Group A received 12.5 mg dolasetron, Group B 3 microg/kg clonidine, and Group C saline 0.9% as placebo. The medication was given after the induction of anesthesia. Postanesthetic shivering was judged by using a five-point scale. In the Clonidine group, 86.6% showed no shivering, whereas in the Dolasetron and Placebo groups, only 63.3% and 66.6%, respectively, were symptom free. Only clonidine, but not dolasetron, significantly reduced the incidence and the severity of shivering. We conclude that clonidine is effective in preventing shivering when given before surgery, whereas dolasetron, at the dose used, is not effective. IMPLICATIONS: Shivering, an irregular muscular fasciculation lasting longer than 15 s, is a common complication secondary to general anesthesia. We compared dolasetron with clonidine (an established antishivering drug) in the prevention of postanesthetic shivering. Dolasetron 12.5 mg was not effective.     

A comparison between meperidine, clonidine and urapidil in the treatment of postanesthetic shivering

Postanesthetic shivering can be treated with many types of drugs. We compared the effects of meperidine, clonidine, and urapidil on postanesthetic shivering. Sixty patients shivering during recovery from general anesthesia were treated in a randomized, double-blinded fashion with 25 mg meperidine IV, 0.15 mg clonidine IV, or 25 mg urapidil IV in three separate groups of 20 patients each. If shivering did not stop within 5 min, the treatment was repeated once; clonidine was replaced with saline for the second dose. Rectal temperature, arterial blood pressure, heart rate, SaO(2) and vigilance were monitored. Clonidine stopped shivering in all 20 patients. A single dose of meperidine stopped the shivering in 18 of 20 patients, with the other 2 patients needing a second dose. Urapidil was less effective: the first dose stopped the shivering in only six patients; the second dose was effective in another six; the drug was ineffective in 8 of 20 patients. Meperidine and clonidine were both nearly 100% effective in treating postanesthetic shivering without negative side effects. By comparison, urapidil was only effective in 60% of patients treated (P <0.01). Implications: Patients shivering during recovery from general anesthesia were treated in a randomized double-blinded fashion with meperidine, clonidine, or urapidil. Meperidine and clonidine were both very effective, whereas urapidil was only effective in 60% of patients treated.     

Dimenhydrinate for prophylaxis of postoperative nausea and vomiting: a meta-analysis of randomized controlled trials

BACKGROUND: Diphenhydramine and its theoclate salt dimenhydrinate are traditional antiemetics still in use. However, so far the quantitative effect of dimenhydrinate in the prophylaxis of postoperative nausea and vomiting (PONV) has not been evaluated systematically. METHODS: Results from randomized controlled trials investigating the efficacy of dimenhydrinate vs. a control to prevent PONV were included in a meta-analysis. Studies were systematically searched through MEDLINE, EMBASE, the Cochrane-Library, manually screening of reference lists of matching review articles and current issues of locally available peer-reviewed anesthesia journals, up to June 2001. The numbers of patients with complete absence of PONV within 6 h and within 48 h after surgery were extracted as the main end point. Pooled relative benefits (RB) and numbers-needed-to-treat (NNT) with their corresponding 95% confidence intervals (CI) were calculated using a random effects model. This quantitative systematic review was performed following the recommendations of the QUORUM statement. In all, 18 trials with 3045 patients were included in the analysis: 1658 patients received a placebo (control) and 1387 patients received dimenhydrinate. RESULTS: The RB to stay completely free of PONV was 1.2 (95% CI: 1.1-1.4) for the early period (NNT = 8; 95% CI: 5-25) and 1.5 (1.3-1.8) for the overall investigated period (NNT = 5; 95% CI: 3-9). CONCLUSION: Dimenhydrinate is a traditional and inexpensive antiemetic with an efficacy that might be considered as clinically relevant. Although in use for a long time, the dose-response, precise estimation of side-effects, optimal time of administration and the benefit of repetitive doses still remain unclear.     

Meperidine and Alfentanil Do Not Reduce the Gain or Maximum Intensity of Shivering

Background: Thermoregulatory shivering can be characterized by its threshold (triggering core temperature), gain (incremental intensity increase with further core temperature deviation), and maximum intensity. Meperidine (a combined micro- and kappa-agonist) treats shivering better than equianalgesic doses of pure micro-opioid agonists. Meperidine's special antishivering action is mediated, at least in part, by a disproportionate decrease in the shivering threshold. That is, meperidine decreases the shivering threshold twice as much as the vasoconstriction threshold, whereas alfentanil (a pure micro-agonist) decreases the vasoconstriction and shivering thresholds comparably. However, reductions in the gain or maximum shivering intensity might also contribute to the clinical efficacy of meperidine. Accordingly, we tested the hypothesis that meperidine reduces the gain and maximum intensity of shivering much more than alfentanil does.

Methods: Ten volunteers were each studied on three separate days: (1) control (no drug); (2) a target total plasma meperidine concentration of 1.2 micro gram/ml; and (3) a target plasma alfentanil concentration of 0.2 micro gram/ml. Skin temperatures were maintained near 31 [degree sign] Celsius, and core temperatures were decreased by central-venous infusion of cold lactated Ringer's solution until maximum shivering intensity was observed. Shivering was evaluated using oxygen consumption and electromyography. A sustained increase in oxygen consumption identified the shivering threshold. The gain of shivering was calculated as the slope of the oxygen consumption versus core temperature regression, and as the slope of electromyographic intensity versus core temperature regression.

Results: Meperidine and alfentanil administration significantly decreased the shivering thresholds. However, neither meperidine nor alfentanil reduced the gain of shivering, as determined by either oxygen consumption or electromyography. Opioid administration also failed to significantly decrease the maximum intensity of shivering.     

Physostigmine Prevents Postanesthetic Shivering As Does Meperidine or Clonidine

Background: Postanesthetic shivering develops in as many as one half of patients recovering from isoflurane anesthesia. Cholinergic stimulation of the hypothalamic-pituitary-adrenal axis and adrenal medulla by physostigmine enhances secretion of arginine vasopressin, epinephrine, and norepinephrine. Because the hypothalamus is the dominant thermoregulatory controller in mammals, and these neurotransmitters may be involved in body temperature control, physostigmine administration may influence the incidence of shivering. Accordingly, the authors tested the hypothesis that physostigmine administration inhibits postanesthetic shivering. Its efficacy was compared with that of saline (negative control) and meperidine and clonidine (positive controls).

Methods: Sixty patients having surgery of the ear or nose were tested. General anesthesia was induced with 2 mg/kg propofol, 0.1 mg/kg vecuronium, and 1.5 micro gram/kg fentanyl and maintained with isoflurane (1.5 +/- 0.4%) in 70% nitrous oxide. At the end of surgery, the patients were randomly assigned to receive an intravenous bolus of 0.04 mg/kg physostigmine, isotonic saline, 0.5 mg/kg meperidine, or 1.5 micro gram/kg clonidine. Heart rate, mean arterial blood pressure, oxygen saturation, visual analog pain score, temperature, and postanesthetic shivering were measured during recovery.

Results: Postanesthetic shivering occurred in 6 of 15 (40%) patients given saline. In contrast, postanesthetic shivering was significantly reduced in physostigmine-treated patients (1 of 15, or 7%) and was absent in patients given clonidine or meperidine.     

Dexmedetomidine and meperidine prevent postanaesthetic shivering

BACKGROUND AND OBJECTIVE: This placebo-controlled study was performed to evaluate the efficacy of dexmedetomidine compared with meperidine and placebo in preventing postanaesthetic shivering. METHODS: We studied 120 patients (ASA I-II) scheduled for elective abdominal or orthopaedic surgery of about 1-3 h duration. Forty patients in each group randomly received 1 microg kg(-1) of dexmedetomidine, 0.5 mg kg(-1) of meperidine or saline 0.9% as placebo, intravenously (i.v.). Mean arterial pressure, heart rate, oxygen saturation and central body temperature were measured. Extubation, awakening and orientation times, shivering, pain, recovery and sedation scores were recorded. RESULTS: Postanaesthetic shivering was seen in 22 patients in the placebo group, four patients in the meperidine group and six patients in the dexmedetomidine group. Sedation scores were significantly higher in the dexmedetomidine group compared with meperidine and placebo groups. Both dexmedetomidine and meperidine caused a significantly prolonged extubation and awakening time compared with placebo. Also, dexmedetomidine caused a significantly prolonged orientation time compared with other two groups. CONCLUSION: Intraoperative intravenously administration of dexmedetomidine 1 microg kg(-1) reduces postanaesthetic shivering as does meperidine 0.5 mg kg(-1) in patients after major surgery.     

Tramadol for prevention of postanaesthetic shivering: a randomised double-blind comparison with pethidine

The present study was conducted with the aims of comparing intravenous tramadol 1, 2 and 3 mg.kg⁻¹ with pethidine 0.5 mg.kg⁻¹ for prophylaxis of postanaesthetic shivering and to find a dose of tramadol that could provide the dual advantage of antishivering and analgesic effect in the postoperative period. The study included 165 patients, randomly allocated to five groups of 33 each. Tramadol in doses of 1, 2 and 3 mg.kg⁻¹, pethidine 0.5 mg.kg⁻¹ or normal saline were administered at the time of wound closure. All three doses of tramadol were effective and comparable to pethidine in preventing postanaesthetic shivering. Tramadol 2 mg.kg⁻¹ had the best combination of antishivering and analgesic efficacy without excessive sedation and thus appeared to be a good choice to be administered at the time of wound closure to provide antishivering effect and analgesia without significant side effects in the postoperative period.     

Intrathecal clonidine does not reduce post-spinal shivering

BACKGROUND: After general or epidural anesthesia, clonidine is known to be effective in suppressing established shivering. The aim of this study was to assess the preventive effect of intrathecal clonidine on post-spinal shivering compared with intravenous (i.v.) clonidine. METHODS: One hundred and fifty patients scheduled for orthopedic surgery were randomly allocated into three groups to receive either 1 microg/kg clonidine i.v. (IV group) or the same volume of isotonic saline (control and IT groups) at 5 min before spinal anesthesia. Spinal anesthesia was performed with 12-15 mg hyperbaric bupivacaine 0.5% plus either 1 ml of saline (control and IV groups) or 150 microg clonidine (IT group). Shivering was evaluated for a period of 90 min and graded as none, mild, moderate, and severe. RESULTS: Twenty patients (40%) in the control group and 17 patients (34%) in the IT group showed shivering compared with four (8%) in the IV group. Patients with moderate-to-severe shivering were only seen in the control and IT group, and the maximal intensity of shivering was not different between the two groups. Patients in the IV group were significantly more sedated than the other groups. CONCLUSIONS: The intrathecal administration of clonidine 150 microg fails to prevent post-spinal shivering; by contrast, we have confirmed that i.v. clonidine 1 microg/kg is an effective method to prevent shivering in patients undergoing spinal anesthesia for orthopedic surgery.     

Postanaesthetic shivering. Epidemiology,pathophysiology and approaches to prevention and management

Postanaesthetic shivering is one of the leading causes of discomfort for patients recovering from general anesthesia. During EMG records, the distinguishing factor from shivering in fully awake patients is the existence of clonus similar to that recorded in patients with spinal cord transection. They coexist with the classic waxing and waning signals associated with cutaneous vasoconstriction (thermoregulatory shivering). The causes responsible for their appearance primarily include hypothermia, which sets in due to thermoregulation inhibition by anesthetics. However, we also note the existence of shivering associated with cutaneous vasodilatation (non-thermoregulatory shivering) one of the origins of which is postoperative pain. Apart from the discomfort and aggravated pain, postanaesthetic shivering raises metabolic demand proportionally to the solicited muscle mass and the patient's cardiac capacities. No link has been demonstrated between their occurrence and an increase in cardiac morbidity but it is preferable to avoid postanaesthetic shivering since it is oxygen draining. Prevention mainly entails preventing hypothermia by actively rewarming the patient. Postoperative skin surface rewarming is a way of obtaining the threshold shivering temperature while raising the skin temperature and improving the patient's comfort. However, it is less efficient than certain drugs such as meperidine, nefopam or tramadol, which act by reducing the shivering threshold temperature.