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

Novel ultrashort-acting benzodiazepine remimazolam lowers shivering threshold in rabbits

Shivering after surgery or during therapeutic hypothermia can lead to serious complications, such as myocardial infarction and respiratory failure. Although several anesthetics and opioids are shown to have anti-shivering effects, their sedative and respiratory side effects dampen the usefulness of these drugs for the prevention of shivering. In the present study, we explored the potential of a novel ultrashort-acting benzodiazepine, remimazolam, in the prevention of shivering using a rabbit model of hypothermia. Adult male Japanese white rabbits were anesthetized with isoflurane. The rabbits received saline (control), remimazolam (either 0.1 or 1 mg/kg/h), or remimazolam + flumazenil, a selective γ-aminobutyric acid (GABA) type A receptor antagonist (n = 6 each). Thirty minutes after discontinuation of the drugs, cooling was initiated by perfusing 10°C water via a plastic tube positioned in the colon until the animal shivered. Core body temperature and hemodynamic and physiological parameters were recorded. Remimazolam at 1 mg/kg/h significantly lowered the core temperature change during shivering (−2.50 ± 0.20°C vs. control: −1.00 ± 0.12°C, p = 0.0009). The effect of 1 mg/kg/h remimazolam on the core temperature change was abolished by flumazenil administration (−0.94 ± 0.16°C vs. control: −1.00 ± 0.12°C, p = 0.996). Most of the hemodynamic and physiological parameters did not differ significantly among groups during cooling. Remimazolam at a clinically relevant dose successfully suppressed shivering in rabbits via the GABA pathway even after its anesthetic effects likely disappeared. Remimazolam may have the potential to prevent shivering in patients undergoing surgery or therapeutic hypothermia.

A Comparative Evaluation of Nalbuphine and Tramadol for the Control of Post-Spinal Anaesthesia Shivering

Objectives

In this study, our primary aim was to compare the efficacy of and haemodynamic changes related to nalbuphine and tramadol when used for the control of post-spinal anaesthesia shivering, as per Wrench shivering grades. The secondary aim was to study the complications and adverse effects associated with the drugs.

Methodology

A total of 60 patients with the American Society of Anesthesiologists (ASA) physical status class I/II who were scheduled to undergo elective surgeries under spinal anaesthesia were divided into two groups of 30 each. Group N received intravenous nalbuphine 0.05 mg/kg and Group T received intravenous tramadol 1 mg/kg, two minutes after the patients started shivering after undergoing spinal anaesthesia. The anaesthesia technique was standardised for all the patients in the study. The shivering grade was measured using the Wrench shivering grade and the level of sedation was studied using the Ramsay Sedation Scale. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were recorded. All the parameters were measured at the baseline and at one, two, five, 10, 15, and 30 minutes after administering the drug.

Results

Immediately after giving the drug, the time taken to control shivering was significantly lower in Group T: 3.633 minutes. However both the drugs controlled shivering effectively. There were no significant haemodynamic changes in both groups, probably due to the lower dosage of drugs used in our study. A different set of side effects were seen in each group. In Group N, out of 30 patients, five (16.67%) patients were sedated, four (13.33%) had hypotension, and two (6.67%) had bradycardia, whereas In Group T, out of 30 patients, five (16.67%) patients had nausea, four (13.33%) had nausea and vomiting, and two (16.67%) had dizziness following the administration of the drug. Respiratory depression or itching was not seen in any patients in either group.

Conclusion

Based on our findings, both Intravenous nalbuphine 0.05 mg/kg and intravenous tramadol 1 mg/kg are effective in treating patients with post-spinal anaesthesia shivering; however, the time taken to control shivering is lower with tramadol than nalbuphine. Both the drugs resulted in minimal haemodynamic changes and adverse effects.

Randomized Double-Blinded Comparative Study of Intravenous Nalbuphine and Tramadol for the Treatment of Postspinal Anesthesia Shivering

Context:

Shivering is one of the most commonly recognized complications of the central neuraxial blockade. For optimal perioperative care, control of postspinal anesthesia shivering is essential.

Aims:

The present study designed to compare the clinical efficacy, hemodynamic parameters, and side effects of nalbuphine and tramadol for control of postspinal anesthesia shivering.

Settings and Design:

This was a prospective, randomized, double-blind study.

Materials and Methods:

This study was conducted on 90 American Society of Anesthesiologists Physical Status I and II patients of either gender, aged between 18 and 60 years, who subsequently developed shivering grade 3 or 4, scheduled for different surgical procedures under spinal anesthesia. The patients were randomized into two groups of 45 patients each to receive either nalbuphine 0.06 mg.kg⁻¹ (Group N) or tramadol 1 mg.kg⁻¹ (Group T). Grade of shivering, onset of shivering, time interval for cessation of shivering, response rate at 5 and 30 min, rescue dose, hemodynamic parameters, and side effects were observed at scheduled intervals.

Statistical Analysis Used:

Independent t-test and Chi-square/Fisher's exact test were used to analyze the data.

Results:

The time taken for cessation of shivering was significantly less with nalbuphine in comparison with tramadol (P < 0.05). It was observed that the response time at 5 and 30 min and rescue dose requirement for control of shivering were not much difference (P > 0.05).

Conclusions:

Both nalbuphine and tramadol are effective; however, the time taken for cessation of shivering is significantly less with nalbuphine when compared to tramadol. Furthermore, tramadol causes significantly more nausea and vomiting; however, nalbuphine causes significantly more sedation.

Nefopam for the prevention of perioperative shivering: a meta-analysis of randomized controlled trials

BACKGROUND

Shivering is a frequent complication following surgery and anaesthesia. A large variety of studies have been reported that nefopam may be efficacious for the prevention and treatment of perioperative shivering. Regrettably, there is still no conclusion of the efficacy and safety of nefopam for the prevention of perioperative shivering. The aim of this analysis is to evaluate the efficacy of nefopam for the prevention of perioperative shivering in patients undergoing different types of anaesthesia compared with placebo group and other active interventions.

METHODS

PubMed, EMBASE, Cochrane Central Register of Control Trials were systematically searched for potentially relevant trials. Trial quality and extracted data were evaluated by two authors independently. Dichotomous data on the absence of shivering was extracted and analysed by using relative risk (RR) with 95% confidence interval (CI). Continuous outcome was abstracted and analysed by using weighted mean difference (WMD) with 95% confidence interval (CI). Outcome data was analysed by using random effect model or fixed effect model in accordance with heterogeneity.

RESULTS

Compared with placebo, prophylactic administration of nefopam significantly reduced the risk of perioperative shivering not only in the patients under general anaesthesia but also neuraxial anaesthesia (RR 0.08; 95% CI 0.05-0.13). As compared with clonidine, nefopam was more efficacious in the prevention of perioperative shivering (RR 0.34; 95% CI 0.17-0.70). Nefopam has no influence on the extubation time (WMD 0.92; 95% CI -0.15-1.99).

CONCLUSION

Our analysis has demonstrated that nefopam is associated with the decrease of risk of perioperative shivering following anaesthesia without influencing the extubation time.

Efficacy of dexmedetomidine on postoperative shivering: a meta-analysis of clinical trials

PURPOSE

Shivering is a frequent complication in the postoperative period. The aim of the current meta-analysis was to assess the efficacy of dexmedetomidine on postoperative shivering.

METHODS

Two researchers independently searched PubMed, EMBASE and the Cochrane Central Register of Controlled Trials for controlled clinical trials. The meta-analysis was performed by Review Manager.

RESULTS

Thirty-nine trials with 2,478 patients were included in this meta-analysis. Dexmedetomidine reduced postoperative shivering compared with placebo (risk ratio [RR] = 0.26; 95% confidence interval [CI]: 0.20 to 0.34), with a minimum effective dose of 0.5 µg·kg(-1) (RR = 0.36; 95% CI: 0.21 to 0.60). The anti-shivering effect can be achieved both intravenously and epidurally when administered within two hours prior to the end of surgery. The efficacy of dexmedetomidine was similar to widely used anti-shivering agents, such as fentanyl, meperidine, tramadol, clonidine and so on; however, dexmedetomidine may increase the incidence of sedation, hypotension, bradycardia and dry mouth.

CONCLUSIONS

The present meta-analysis indicates that dexmedetomidine shows superiority over placebo, but not over other anti-shivering agents. Therefore, considering its high price and potential adverse events, dexmedetomidine may not be appropriate solely for the purpose of the prevention of postoperative shivering.

Comparison of the efficacy of a forced-air warming system and circulating-water mattress on core temperature and post-anesthesia shivering in elderly patients undergoing total knee arthroplasty under spinal anesthesia

Background

In the present study, we compared changes in body temperature and the occurrence of shivering in elderly patients undergoing total knee arthroplasty under spinal anesthesia during warming with either a forced-air warming system or a circulating-water mattress.

Methods

Forty-six patients were randomly assigned to either the forced-air warming system (N = 23) or circulating-water mattress (N = 23) group. Core temperature was recorded using measurements at the tympanic membrane and rectum. In addition, the incidence and intensity of post-anesthesia shivering and verbal analogue score for thermal comfort were simultaneously assessed.

Results

Core temperature outcomes did not differ between the groups. The incidence (13.0 vs 43.5%, P < 0.05) and intensity (20/2/1/0/0 vs 13/5/3/2/0, P < 0.05) of post-anesthesia shivering was significantly lower in the forced-air system group than in the circulating-water mattress group.

Conclusions

The circulating-water mattress was as effective as the forced-air warming system for maintaining body temperature. However, the forced-air warming system was superior to the circulating-water mattress in reducing the incidence of post-anesthesia shivering.

Comparison of meperidine and nefopam for prevention of shivering during spinal anesthesia

BACKGROUND

Shivering is a frequent event during spinal anesthesia and meperidine is a well-known effective drug for prevention and treatment of shivering. Nefopam is a non-opiate analgesic and also known to have an anti-shivering effect. We compared nefopam with meperidine for efficacy of prevention of shivering during spinal anesthesia.

METHODS

Sixty five patients, American Society of Anesthesiologists physical status I or II, aged 20-65 years, scheduled for elective orthopedic surgery under spinal anesthesia were investigated. Patients were randomly divided into two groups, meperidine (Group M, n = 33) and nefopam (Group N, n = 32) groups. Group M and N received meperidine 0.4 mg/kg or nefopam 0.15 mg/kg, respectively, in 100 ml of isotonic saline intravenously. All drugs were infused for 15 minutes by a blinded investigator before spinal anesthesia. Blood pressures, heart rates, body temperatures and side effects were checked before and at 15, 30, and 60 minutes after spinal anesthesia.

RESULTS

The incidences and scores of shivering were similar between the two groups. The mean arterial pressures in Group N were maintained higher than in Group M at 15, 30, and 60 minutes after spinal anesthesia. The injection pain was checked in Group N only and its incidence was 15.6%.

CONCLUSIONS

We conclude that nefopam can be a good substitute for meperidine for prevention of shivering during spinal anesthesia with more stable hemodynamics, if injection pain is effectively controlled.

A comparison between sevoflurane and desflurane anesthesia in patients undergoing craniotomy for supratentorial intracranial surgery

BACKGROUND

Desflurane in neurosurgery may be beneficial because it facilitates postoperative early neurologic evaluation. However, its use has been debated because of its capacity to promote cerebral vasodilatation. Sevoflurane has been extensively used in neurosurgical patients. In this prospective clinical trial, we compared early postoperative recovery and cognitive function in patients undergoing craniotomy for supratentorial expanding lesions and receiving sevoflurane or desflurane anesthesia.

METHODS

One hundred twenty patients, ASA physical status I-III (66 men), Glascow Coma Scale 15, undergoing craniotomy for supratentorial expanding lesions were enrolled in the study. Patients were randomly allocated to two anesthetic regimens. In Group S (60 patients, 52 +/- 16 yr), anesthesia was maintained using sevoflurane with end-tidal of 1.5%-2% and was age adjusted to obtain approximately 1.2 minimum alveolar anesthetic concentration. In Group D (60 patients, 60 +/- 14 yr), anesthesia was maintained using desflurane with end-tidal of 6%-7% and was age adjusted to obtain approximately 1.2 minimum alveolar concentration. Emergence time was measured as the time from drug discontinuation to the time at which patients opened their eyes; tracheal extubation time was measured as the time from anesthetic discontinuation and tracheal extubation. Recovery time was measured as the time elapsing from discontinuation of anesthetic and the time when patients were able to recall their name and date of birth. Cognitive behavior was evaluated with the Short Orientation Memory Concentration Test. In the postanesthesia care unit, a blinded observer monitored the patients for 3 h; the incidence of hemodynamic events, pain, nausea, and shivering requiring rescue medication was recorded.

RESULTS

The mean emergence time (12.2 +/- 4.9 min in Group S vs 10.8 +/- 7.2 min in Group D; P = ns) was similar in the two groups, whereas the mean extubation time and recovery time were longer in Group S (15.2 +/- 3.0 min in Group S vs 11.3 +/- 3.9 min in Group D and 18.2 +/- 2.3 min in Group S vs 12.4 +/- 7.7 min in Group D, respectively; P < 0.001). The Short Orientation Memory Concentration Test score differed between the two groups only at the earliest assessment (15 min after extubation). No difference between the two groups was found in pain, shivering, nausea, vomiting, and incidence of postoperative hemodynamic events.

CONCLUSION

Patients who received desflurane had a shorter extubation and recovery time but similar intraoperative and postoperative incidence of complications compared with those who received sevoflurane.

Thermoregulatory management for mild therapeutic hypothermia

In recent years the use of mild therapeutic hypothermia as a means of neuroprotection has become an important concept for treatment after cerebral ischemic hypoxic injury. Mild therapeutic hypothermia has been shown to improve outcome after out-of-hospital cardiac arrest, and many studies suggest a beneficial effect of mild therapeutic hypothermia on patient outcome after traumatic brain injury, cerebrovascular damage and neonatal asphyxia. This review article explores the numerous possibilities and methods for the induction of mild therapeutic hypothermia, reviews thermoregulatory management during maintenance and discusses associated risks and complications.

Perioperative complications of hypothermia

Perioperative hypothermia is a common and serious complication of anesthesia and surgery and is associated with many adverse perioperative outcomes. It prolongs the duration of action of inhaled and intravenous anesthetics as well as the duration of action of neuromuscular drugs. Mild core hypothermia increases thermal discomfort, and is associated with delayed post anaesthetic recovery. Mild hypothermia significantly increases perioperative blood loss and augments allogeneic transfusion requirement. Only 1.9 degrees C core hypothermia triples the incidence of surgical wound infection following colon resection and increases the duration of hospitalization by 20%. Hypothermia adversely affects antibody- and cell-mediated immune defences, as well as the oxygen availability in the peripheral wound tissues. Furthermore mild hypothermia triples the incidence of postoperative adverse myocardial events. Thus, even mild hypothermia contributes significantly to patient care costs and needs to be avoided.

Effect of active warming on shivering during spinal anesthesia

BACKGROUND

Hypothermia is considered one of the reasons for intraoperative shivering. The purpose of this study is to assess whether active warming can prevent hypothermia and shivering in young adults under spinal anesthesia.

METHODS

Fifty male patients scheduled for an elective operation on lower extremity under spinal anesthesia were randomly assigned into the warming group (n = 25) and the control group (n = 25). The active warming was performed using a forced air-warming device, a warmed blanket and warmed fluid. Axillary and tympanic temperatures, shivering degree, thermal discomfort, and anesthetic level were checked every 10 minutes after intrathecal injection of local anesthetics.

RESULTS

Patients' characteristics and anesthetic levels were comparable between the groups. Axillary and tympanic temperatures were maintained higher in the warming group than the control group 10 minutes and 20 minutes after intrathecal injection respectively. The lowest temperature in operating room was higher in the warming group (36.3 +/- 0.5degrees C) compared with the control group (35.7 +/- 0.5degrees C) (P < 0.05). Incidences of intraoperative shivering and thermal discomfort were lower in the warming group.

CONCLUSIONS

We conclude that intraoperative active warming can prevent hypothermia and shivering during spinal anesthesia.

The effect of irrigation fluid temperature on core body temperature in arthroscopic shoulder surgery

INTRODUCTION

The purpose of this study was to investigate the relationship between irrigation fluid temperature and core body temperature in patients undergoing arthroscopic shoulder surgery.

MATERIALS AND METHODS

Twenty-four consecutive patients undergoing arthroscopic subacromial decompression were allocated to receive irrigation fluid at either room temperature (22 degrees C) or warmed to 36 degrees C. There were no statistically significant differences between the two groups in any of the preoperative parameters. Core temperature was monitored throughout surgery. The maximum drop in core temperature for each patient was calculated.

RESULTS

The mean maximum drop in the room temperature group was 1.67 degrees C (95% CI 1.33-1.97) and 0.33 degrees C (95% CI 0.17-0.49) in the warmed fluid group (P < 0.001). Further to this the drop in core temperature in the room temperature group was maintained throughout surgery whereas normothermia resumed by 30 min in the warmed fluid group.

CONCLUSION

We thus conclude that core temperature may be influenced by irrigation fluid temperature and recommend that fluid be warmed to 36 degrees C.

Early postoperative complications after intracranial surgery: comparison between total intravenous and balanced anesthesia

This prospective study was performed to compare the incidence of complications occurring after neurosurgical procedures in patients anesthetized with either sevoflurane-fentanyl or propofol-remifentanil anesthesia. We enrolled 162 American Society of Anesthesiologists (ASA) I to III patients (82 females and 80 males, Glasgow 15) undergoing elective neurosurgical procedures. Anesthesia was conducted using either propofol-remifentanil (T group; n=80 patients) or sevoflurane-fentanyl (S group; n=82 patients). All patients were monitored in the postanesthesia care unit for 6 hours after extubation. We analyzed and compared in both groups the incidence of high severity complications such as respiratory events (PaO2 <90 mm Hg; PaCO2 >45 mm Hg) and neurologic events (seizures, new motor or sensory deficit, unexpected delay of awakening) and the incidence of low severity complications such as hypertension (mean arterial pressure increase above 30% of baseline), hypotension (mean arterial pressure decrease below 30% of baseline), pain, shivering, nausea, and vomiting. A total of 162 complications occurred in 92 patients (57%) with 50 patients (31%) having had 1, 26 patients (16%) having had 2, and 16 patients (10%) having had 3 or more events. The most frequent complication was respiratory impairment (28%) which was frequently reported only in the first postoperative hour. Out of the total number of complicating events, 77 (48 %) were found in group S, and 85 (52%) in group T (P=ns). Severe complications were rarely reported and evenly distributed in the 2 anesthetic groups. Similarly, no difference could be demonstrated in the composite incidence of less serious complications between the 2 anesthetic regimens tested in this study. This study confirms that the recovery period after neurosurgical procedures remains a time of great potential danger to patients given the high incidence of postoperative complicating events independently from the anesthetic strategy.

Progress in shivering control

Hypothermia is a potent neuroprotectant and induced hypothermia holds great promise as a therapy for acute neuronal injury. Thermoregulatory responses, most notably shivering, present major obstacles to therapeutic temperature management. A review of thermoregulatory physiology and strategies aimed at controlling physiologic responses to hypothermia is presented.

Nefopam is more potent than carbamazepine for neuroprotection against veratridine in vitro and has anticonvulsant properties against both electrical and chemical stimulation

Nefopam (NEF) is a known analgesic that has recently been shown to be effective in controlling both neuropathic pain and convulsions in rodents. In this study we compared nefopam to carbamazepine (CBZ), a reference antiepileptic drug (AED), for their ability to protect cerebellar neuronal cultures from neurodegeneration induced by veratridine (VTD). Furthermore, we tested nefopam for protection against both, maximal electroshock-induced seizures (MES), and isoniazid-induced seizures in mice. Both NEF and CBZ were effective in preventing both signs of excitotoxicity and neurodegeneration following exposure of cultures to 5 microM veratridine for 30 min and 24 h, respectively. Concentrations providing full neuroprotection were 500 microM CBZ and 50 microM NEF, while the concentration providing 50% neuroprotection was 200 microM for CBZ and 20 microM for NEF. Neither NEF nor CBZ reduced excitotoxicity following direct exposure of cultures to glutamate, but CBZ failed to reduce increases in intracellular calcium following stimulation of L-type voltage sensitive calcium channels. In vivo, NEF (20 mg/kg i.p.) significantly reduced MES and fully prevented MES-induced terminal clonus (TC). In comparison, NEF was significantly more effective than CBZ in preventing MES, although both drugs were equally effective against MES-induced TC. Furthermore, nefopam provided protection against isoniazid-induced seizures at doses similar to those protecting against MES.

No difference in emergence time and early cognitive function between sevoflurane-fentanyl and propofol-remifentanil in patients undergoing craniotomy for supratentorial intracranial surgery

Balanced anesthesia with sevoflurane-fentanyl has been widely accepted as anesthetic management for neurosurgery. Propofol-remifentanil regimen has been successfully used in various surgical settings, but a comprehensive comparison of sevoflurane-fentanyl and propofol-remifentanil anesthesia in patients undergoing craniotomy for supratentorial intracranial surgery has not yet been done. The aim of this prospective, randomized, open-label clinical trial was to compare clinical properties of sevoflurane-fentanyl with propofol-remifentanil anesthesia in patients undergoing supratentorial intracranial surgery. The primary endpoint was to compare early postoperative recovery and cognitive functions within the two groups; we also evaluated hemodynamic events, vomiting, shivering, and pain. One hundred twenty patients (64 males; age 15-75 years) were randomized to either total intravenous anesthesia (group T) or sevoflurane anesthesia (group S). Emergence and extubation times and cognitive function (Short Orientation Memory Concentration Test [SOMCT]) were compared in the two groups. Brain swelling, incidence of hypotensive and hypertensive episodes, postoperative vomiting, shivering, and pain were also analyzed. The mean emergence time (12.2 +/- 4.9 minutes for group S versus 12.3 +/- 6.1 minutes for group T; P = 0.92) and extubation time (18.2 +/- 2.3 minutes for group S versus 18.3 +/- 2.1 minutes for group T; P = 0.80) were similar in the two groups. Average SOMCT scores, both 15 minutes after extubation (25.6 +/- 4.9 in group S versus 23.9 +/- 7.5 in group T; P = 0.14) and 45 minutes after extubation (27.3 +/- 2.2 in group S versus 26.0 +/- 5.1 in group T; P = 0.07) were also comparable. Brain swelling was present in seven and five patients in groups S and T, respectively (P = 0.76). Hypotension was present in 12% (group S) and 28% (group T) of patients (P = 0.02). Hypertension was present in 17% of patients in group S and 40% of patients in group T (P = 0.0046). Shivering was present in 18% and 25% of patients in groups T and S (P = 0.37). Our study demonstrates that there is no patient benefit of using total intravenous anesthesia with an ultra-short-acting opioid over the conventional balanced volatile technique in terms of recovery and cognitive functions.

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.

Shivering in acutely ill vulnerable populations

The hazards of thermoregulatory shivering in the critically ill are often overlooked by caregivers. Shivering may accompany heat loss from bathing, dressing, transport, and many therapeutic activities. Febrile shivering is common during chills of fever, blood product transfusions, administration of antigenic drugs, and chemotherapy. Many patients are at risk for shivering and its negative consequences that increase oxygen expenditure and cardiorespiratory effort. Learning how underlying thermoregulatory mechanisms are involved in shivering clarifies how temperature gradients and environmental stimuli induce the shivering response. Knowledge of the anatomical progression of shivering equips the nurse to recognize or prevent this energy-consuming response. This article discusses measures to prevent shivering as well as evidence-based interventions to manage shivering during fever, aggressive cooling, and postoperative recovery. Detailed information is presented on assessment and documentation of the extent and severity of shivering.

Single-Dose Parenteral Pharmacological Interventions for the Prevention of Postoperative Shivering: A Quantitative Systematic Review of Randomized Controlled Trials

Shivering is a frequent complication in the postoperative period. The relative efficacy of pharmacological interventions to prevent this phenomenon is not well understood. We performed a systematic search for full reports of randomized comparisons of prophylactic, parenteral, single-dose antishivering interventions with inactive control (placebo or no treatment). Variable doses were converted to fixed doses. Dichotomous data on the absence of shivering were analyzed by using relative benefit (RB) and number needed to treat (NNT) with 95% confidence intervals (CI). Data from 27 trials (1348 adults received an antishivering intervention; 931 were controls) were analyzed. The average incidence of shivering in controls was extremely frequent (52%). Clonidine 65-300 microg (1078 patients), meperidine 12.5-35 mg (250 patients), tramadol 35-220 mg (250 patients), and nefopam 6.5-11 mg (204 patients) were tested in at least 3 trials each. All were more effective than control. For clonidine, meperidine, and nefopam, there was some weak evidence of dose responsiveness. For small-dose clonidine (65-110 microg), the RB compared with control was 1.32 (95% CI, 1.16-1.51); for medium-dose clonidine (140-150 microg), the RB was 1.83 (95% CI, 1.47-2.27); and for large-dose clonidine (220-300 microg), the RB was 1.52 (95% CI, 1.30-1.78). For all clonidine regimens combined, the RB was 1.58 (95% CI, 1.43-1.74), with an NNT of 3.7. For all meperidine regimens combined, the RB was 1.67 (95% CI, 1.37-2.03), with an NNT of 3. For all tramadol regimens combined, the RB was 1.93 (95% CI, 1.56-2.39), with an NNT of 2.2. For all nefopam regimens combined, the RB was 2.62 (95% CI, 2.02-3.40), with an NNT of 1.7. Methylphenidate, midazolam, dolasetron, ondansetron, physostigmine, urapidil, and flumazenil were tested in no more than 3 trials each, with a limited number of patients.

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, a nonsedative benzoxazocine analgesic, selectively reduces the shivering threshold in unanesthetized subjects

BACKGROUND

The analgesic nefopam does not compromise ventilation, is minimally sedating, and is effective as a treatment for postoperative shivering. The authors evaluated the effects of nefopam on the major thermoregulatory responses in humans: sweating, vasoconstriction, and shivering.

METHODS

Nine volunteers were studied on three randomly assigned days: (1) control (saline), (2) nefopam at a target plasma concentration of 35 ng/ml (low dose), and (3) nefopam at a target concentration of 70 ng/ml (high dose, approximately 20 mg total). Each day, skin and core temperatures were increased to provoke sweating and then reduced to elicit peripheral vasoconstriction and shivering. The authors determined the thresholds (triggering core temperature at a designated skin temperature of 34 degrees C) by mathematically compensating for changes in skin temperature using the established linear cutaneous contributions to control of each response.

RESULTS

Nefopam did not significantly modify the slopes for sweating (0.0 +/- 4.9 degrees C. microg-1. ml; r2 = 0.73 +/- 0.32) or vasoconstriction (-3.6 +/- 5.0 degrees C. microg-1. ml; r2 = -0.47 +/- 0.41). In contrast, nefopam significantly reduced the slope of shivering (-16.8 +/- 9.3 degrees C. microg-1. ml; r2 = 0.92 +/- 0.06). Therefore, high-dose nefopam reduced the shivering threshold by 0.9 +/- 0.4 degrees C (P < 0.001) without any discernible effect on the sweating or vasoconstriction thresholds.

CONCLUSIONS

Most drugs with thermoregulatory actions-including anesthetics, sedatives, and opioids-synchronously reduce the vasoconstriction and shivering thresholds. However, nefopam reduced only the shivering threshold. This pattern has not previously been reported for a centrally acting drug. That pharmacologic modulations of vasoconstriction and shivering can be separated is of clinical and physiologic interest.

Postoperative shivering in children: a review on pharmacologic prevention and treatment

Postoperative shivering consists of muscular tremor and rigidity. It is often associated with body heat loss, although hypothermia alone does not fully explain the occurrence of shivering. Shivering is self-limiting, never becomes chronic, and is rarely associated with major morbidity. However, it affects the comfort of the patients, and may sometimes lead to more serious complications. The efficacy of a great variety of pharmacologic interventions to prevent shivering and to treat established symptoms has been tested in randomized controlled trials. These can be gathered systematically; recommendations on prevention and treatment can then be based on the strongest evidence. Unfortunately all these trials have been performed in adults. Thus, recommendations for the control of postoperative shivering in children have to be extrapolated from adult data. In adults, a systematic review strongly suggests that simple measurements are efficacious for both prevention and treatment. For prevention, extrapolation of these adult data indicates that three children have to receive intravenous clonidine 1.5 micro g/kg during anesthesia for one not to shiver, when they would have done so had they not received clonidine. For this degree of efficacy, the expected incidence of shivering (baseline risk) has to be high (approximately 50%). For treatment, extrapolation from adult data indicates that less than two children need to receive intravenous meperidine (pethidine) 0.35 mg/kg, or clonidine 1.5 micro g/kg for one to stop shivering five minutes after drug administration, when they would not have done so had they not received one of these drugs. Since the treatment of established shivering is efficacious, simple, inexpensive, and relatively safe, and since prevention is only efficacious if the baseline risk is very high, we recommend the 'wait and see' strategy.

The effects of urapidil on thermoregulatory thresholds in volunteers

In a previous study we have shown that the antihypertensive drug, urapidil, stops postanesthetic shivering. One possible mechanism in the inhibition of postanesthetic shivering by urapidil may be alterations in thermoregulatory thresholds. We therefore studied the effects of urapidil on vasoconstriction and shivering thresholds during cold-induced shivering in volunteers. Seven healthy male volunteers were cooled by an infusion of saline at 4 degrees C on two study days separated by 48 h. Thermoregulatory vasoconstriction was estimated using forearm minus fingertip skin-temperature gradients, and values exceeding 0 degrees C were considered to represent significant vasoconstriction. The rectal core temperatures at the beginning of shivering and at vasoconstriction were considered the thermoregulatory thresholds. Before cooling, either 25 mg of urapidil or placebo was administered randomly and blindly to each volunteer. When shivering occurred continuously for 10 min, another 25 mg of urapidil was administered IV to completely stop shivering. Urapidil led to a decrease in core temperature at vasoconstriction and shivering threshold by 0.4 degrees C plus/minus 0.2 degrees C (P < 0.001) and 0.5 degrees C plus/minus 0.3 degrees C (P < 0.01), respectively. Oxygen consumption increased during shivering by 70% plus/minus 30% (P < 0.01) in comparison with baseline and decreased levels after shivering stopped, despite the continued low core temperature. Our investigation shows that urapidil stops postanesthetic shivering by decreasing important thermoregulatory thresholds. This means that shivering, not hypothermia, is treated, and hypothermia will need more attention in the postanesthesia care unit.

IMPLICATIONS

In this study we show that the antihypertensive drug urapidil stops cold-induced shivering and decreases normal thermoregulatory responses, i.e., the thresholds for vasoconstriction and shivering, in awake volunteers.

Postanaesthetic shivering: epidemiology, pathophysiology, and approaches to prevention and management

Along with nausea and vomiting, postanaesthetic shivering is one of the leading causes of discomfort for patients recovering from general anaesthesia. The distinguishing factor during electromyogram recordings between patients with postanaesthetic shivering and shivering in fully awake patients is the existence of clonus similar to that recorded in patients with spinal cord transection. Clonus coexists with the classic waxing and waning signals associated with cutaneous vasoconstriction (thermoregulatory shivering). The primary cause of postanaesthetic shivering is peroperative hypothermia, which sets in because of anaesthetic-induced inhibition of thermoregulation. However, shivering associated with cutaneous vasodilatation (non-thermoregulatory shivering) also occurs, one of the origins of which is postoperative pain. Apart from causing discomfort and aggravation of pain, postanaesthetic shivering increases metabolic demand proportionally to the solicited muscle mass and the cardiac capacity of the patient. No link has been demonstrated between the occurrence of shivering and an increase in cardiac morbidity, but it is preferable to avoid postanaesthetic shivering because it is oxygen draining. Prevention mainly entails preventing peroperative hypothermia by actively rewarming the patient. Postoperative skin surface rewarming is a rapid way of obtaining the threshold shivering temperature while raising the skin temperature and improving the comfort of the patient. However, it is less efficient than certain drugs such as meperidine, clonidine or tramadol, which act by reducing the shivering threshold temperature.

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.

Novel effect of nefopam preventing cGMP increase, oxygen radical formation and neuronal death induced by veratridine

Nefopam hydrochloride is a potent analgesic compound that possesses a profile distinct from that of opiods or anti-inflammatory drugs. Previous evidence suggested a central action of nefopam but the detailed mechanisms remain unclear. Here we have used cultured cerebellar neurons to test the hypothesis that nefopam may modulate voltage sensitive sodium channel (VSSC) activity. Nefopam (100 microM) effectively prevented NMDA receptor-mediated early appearance (30 min) of toxicity signs induced by the VSSC activator veratridine. Delayed neurotoxicity by veratridine occurring independently from NMDA receptor activation, was also prevented by nefopam. In contrast, excitotoxicity following direct exposure of neurons to glutamate was not affected. Neuroprotection by nefopam was dose-dependent. 50% protection was obtained at 57 microM while full neuroprotection was achieved at 75 microM nefopam. Veratridine-induced sodium influx was completely abolished in nefopam-treated neurons. Intracellular cGMP and oxygen radical formation following VSSC stimulation by veratridine were also effectively prevented by nefopam. Our data are consistent with an inhibitory action of nefopam on VSSC and suggest that nefopam may modulate the release of endogenous glutamate following activation of these channels. This novel action of nefopam may be of great interest for the treatment of neurodegenerative disorders involving excessive glutamate release and neurotransmission.

Urapidil does not prevent postanesthetic shivering: a dose-ranging study

PURPOSE

To investigate the effect of 0.2 mg x kg(-1), 0.3 mg x kg(-1) and 0.4 mg x kg(-1) urapidil on the incidence and severity of postanesthetic shivering.

METHODS

One hundred and fifty patients (ASA I-III) scheduled for elective abdominal, urologic or orthopedic surgery under standardized general anesthesia were randomly allocated to one of five groups (each group n=30) using a double-blind protocol: group A received 0.2 mg x kg(-1) urapidil, group B: 0.3 mg x kg(-1) urapidil, group C: 0.4 mg x kg(-1) urapidil, group D: 3 microg x kg(-1) clonidine (positive control group), and group E: saline 0.9% as placebo (negative control group). Postanesthetic shivering was scored using a five-point scale.

RESULTS

Twelve patients of group A, 11 of group B, nine of group C, three of group D and 14 of group E showed signs of postanesthetic shivering. Postanesthetic shivering was significantly decreased in the clonidine group compared to the three urapidil groups and the placebo group. Significantly less patients treated with clonidine needed anti-shivering therapy. There were no significant differences between the urapidil and placebo groups. Therapeutic interventions for hemodynamic effects were not required in any group. Time to extubation, but not time to discharge, was prolonged in the clonidine group.

CONCLUSION

Urapidil showed no beneficial effect on shivering in any of the doses evaluated, whereas prophylactic administration of clonidine was effective in preventing postanesthetic shivering.

Effects of shivering prevention on haemodynamic and metabolic demands in hypothermic postoperative neurosurgical patients

We evaluated the haemodynamic and metabolic effects of prevention of shivering after prophylactic nefopam administration in neurosurgical patients undergoing craniotomy and mild systemic hypothermia (33-35 degrees C). Forty patients were enrolled in a randomised, double-blind study. Before extubation, patients received intravenously either nefopam 0.12 mg.kg-1 or an equal volume of saline 0.9%. Left ventricular systolic work index, oxygen consumption index and systemic lactate concentration were recorded before, immediately after and every 20 min for 2 h after extubation. Shivering appeared in two patients treated with nefopam and in all control patients (p < 0.001). Both left ventricular systolic work index and oxygen consumption index were similar in the two groups before extubation, increased after extubation, and further increased in control patients showing a statistical difference compared to patients treated with nefopam. Our results suggest that nefopam is effective in preventing postoperative shivering in patients undergoing neurosurgery and mild hypothermia and attenuates the haemodynamic effects of shivering during rewarming.

Tramadol for postoperative shivering: a double-blind comparison with pethidine

In most operating and recovery rooms, shivering is controlled by the use of humidifiers, warming blankets, and inhalation of humidified heated oxygen. However, pharmacological control is an effective alternate treatment modality. This randomized, double-blind trial, conducted in 30 ASA Grade 1 or 2 patients, was designed to explore the efficacy of tramadol and pethidine in the treatment of post-anaesthetic shivering. Tramadol is an inhibitor of the re-uptake of serotonin (5-hydroxytryptamine) and norepinephrine in the spinal cord. This facilitates 5-hydroxytryptamine release, which influences thermoregulatory control. We compared the efficacy of tramadol with that of pethidine, presently a widely used drug for the control of shivering. Patients received either tramadol 1 mg/kg or pethidine 0.5 mg/kg intravenously and the grade of shivering, pulse rate, blood pressure and respiratory rate were observed every 10 minutes after injection for one hour Shivering was significantly more likely to have ceased in the tramadol group (12 of 15 versus 4 of 15 cases, P<0.05) at 10 minutes after drug administration and this control was better sustained. No patients receiving tramadol had a recurrence of shivering. It is concluded that intravenous tramadol 1 mg/kg is more effective for the treatment of postoperative shivering than pethidine 0.5 mg/kg.

Postoperative shivering: aetiology and treatment

Most postanaesthetic shivering-like tremor is normal thermoregulatory shivering in response to core hypothermia. Therefore, shivering will be prevented by maintaining intraoperative normothermia. Other thermoregulatory-related shivering is caused by the release of cytokines by the surgical procedure. Non-thermoregulatory shivering, occurring in normothermic patients, is caused by other aetiologies such as postoperative pain. It is thus likely that adequate treatment of postoperative pain will ameliorate non-thermoregulatory tremor. In addition, the administration of antipyretic drugs reduces shivering in patients after cardiopulmonary bypass surgery.

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.

A comparison among nalbuphine, meperidine, and placebo for treating postanesthetic shivering

Postanesthetic shivering (PS) is distressing for patients and may induce a variety of complications. In this prospective, double-blinded, randomized study, we evaluated the value of nalbuphine, compared with meperidine and saline, for treating PS. Ninety adult patients were included in the study. Group 1 (n = 30) received i.v. nalbuphine 0.08 mg/kg, Group 2 (n = 30) received i.v. meperidine 0.4 mg/kg, and Group 3 (n = 30) received i.v. saline. Treatment that stopped shivering was considered to have been successful. The results demonstrated that, 5 min after treatment, both nalbuphine and meperidine provided a rapid and potent anti-shivering effect on PS, with high response rates of 80% and 83%, compared with those of saline (0%) (P < 0.01). Thirty minutes after injection, the response rates of nalbuphine and meperidine were 90% and 93%, respectively, compared with 17% in the saline group (P < 0.01). The differences between nalbuphine and meperidine were not significant. We conclude that nalbuphine may be an alternative to meperidine for treating PS.

IMPLICATIONS

We evaluated nalbuphine versus meperidine and saline for treating postanesthetic shivering. Our results demonstrate that both nalbuphine and meperidine provide a similar rapid and potent anti-shivering effect. Nalbuphine may be an alternative to meperidine for treating postanesthetic shivering.

Late intraoperative clonidine administration prevents postanesthetic shivering after total intravenous or volatile anesthesia

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 relative efficacy of clonidine during isoflurane and propofol anesthesia remains unknown. We therefore evaluated the incidence of postanesthetic shivering in patients given clonidine during nitrous oxide/isoflurane or propofol anesthesia. Because clonidine is an analgesic, we also evaluated postoperative pain and analgesic requirements. We studied 60 patients undergoing elective ear or nose surgery. General anesthesia was induced with 2.0 mg/kg propofol, 1.5 micrograms/kg fentanyl, and 0.1 mg/kg vecuronium. General anesthesia was maintained with isoflurane and 70% nitrous oxide in one group of patients; in the other, a continuous infusion of propofol (8 mg.kg-1.h-1) was administered (without nitrous oxide). Five minutes before tracheal extubation, patients in each group were randomly assigned to receive saline, placebo, or 3 micrograms/kg clonidine intravenously. Postanesthetic shivering was evaluated by a blind investigator. Postoperative pain was assessed using a visual analog scale. Postoperative shivering was observed in 53% of the patients given isoflurane without clonidine and in 13% of the patients given propofol without clonidine. No patient given clonidine shivered. Clonidine administration significantly reduced postoperative pain. The incidence of postanesthetic shivering was significantly less after propofol anesthesia than after isoflurane/nitrous oxide anesthesia. However, a late intraoperative bolus administration of 3 micrograms/kg clonidine prevents postoperative shivering in patients given either type of anesthesia.