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PubMedDate not supplied

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.

Adult↗
PubMed1998

[Prophylactic nefopam administration for post-anesthetic shivering].

PURPOSE: Shivering is a frequent postanaesthetic complication. Its definite reason is unknown. Patients with cardiovascular or pulmonary diseases are endangered by postanaesthetic shivering. The aim of this study was to assess the efficacy of nefopam in prophylaxis of shivering. Additionally we investigated the influence of nefopam on haemodynamic parameters and on the time until extubation. METHODS: 30 patients (ASA I-II) were randomly allocated in a double-blind fashion to one of two groups to receive directly after the end of isoflurane application either nefopam (0.15 mg/kg) or placebo (0.9% saline). The period of anaesthesia had to be longer than 60 minutes. All patients received a premedication with lorazepam (0.02 mg/kg) 30-45 minutes prior to surgery. Induction of anaesthesia was standardised: fentanyl (3 micrograms/kg), thiopentone (5 mg/kg), atracurium (0.4 mg/kg). Intraoperatively a mixture of isoflurane, nitrous oxide (60%) and oxygen was used to maintain anaesthesia. The following parameters were evaluated: Age, sex, duration of operation and anaesthesia and the time between the end of application of volatiles and extubation. Heart rate (HR), mean arterial blood pressure (MAP), rectal temperature and O2-saturation were measured at predefined data points. Postoperatively the consumption of analgesic was documented. The severity of shivering was classified in five grades. RESULTS: In the control-group nine patients shivered (60%), whereas in the nefopam group only one patient (6.6%) shivered (p < 0.05). In comparison to the placebo group we observed in the nefopam group a significantly decreased HR 30 and 60 minutes postoperatively (p < or = 0.007 and p < or = 0.002). We did not observe prolonged awakening in the nefopam-treated patients. MAP and O2-saturation showed similar reactions in both groups. CONCLUSION: The data indicate that prophylactic administration of nefopam can suppress postanaesthetic shivering. Prolonged awakening was not observed.

Analgesics, Non-Narcotic↗
PubMed1995

[Treatment of postoperative shivering with nalbuphine].

OBJECTIVE: Postoperative shivering is common and has potentially adverse side effects in high-risk patients. Meperidine, which binds to both mu- and kappa-opioid receptors, is reported to be more effective in treating shivering than morphine or fentanyl. Recent data indicate that much of meperidine's special antishivering effect may be mediated by its kappa-opioid receptor activity. Nalbuphine, an opioid agonist/antagonist also has a potent affinity for kappa-receptors. The aim of this study was to evaluate the antishivering effect of nalbuphine in comparison to meperidine. METHODS: 100 ASA physical status I-II patients shivering after elective surgery were included in the study. General anaesthesia was performed with thiopentone, low-dose fentanyl and enflurane in N2O/O2. After arrival in the recovery room patients shivering within 5 min received either meperidine 25 mg or nalbupine 10 mg in a double-blind, randomised manner. The duration and severity of shivering, heart rate, respiratory rate, blood pressure, end-tidal CO2 concentration, O2-saturation and awareness were documented until 20 min after injection. Patients in need of a second injection were excluded from the study. RESULTS: Demographic variables, duration of operation and temperature decreases were not significantly different between treatment groups. The suppression of shivering was achieved within 4.0 +/- 3.5 or 4.6 +/- 4.1 min following the injection of meperidine or nalbuphine, respectively (p = NS). Vital signs and postoperative vigilance showed no significant differences. No adverse side effects were observed. DISCUSSION: The data indicated that nalbuphine suppressed postoperative shivering as effectively and timely as meperidine in equianalgesic doses. The observation is consistent with the hypothesis that stimulation of kappa-opioid receptors is a likely explanation for much of meperidine's antishivering action.

Adult↗
PubMed2006

Ondansetron does not reduce the shivering threshold in healthy volunteers.

BACKGROUND: Ondansetron, a serotonin-3 receptor antagonist, reduces postoperative shivering. Drugs that reduce shivering usually impair central thermoregulatory control, and may thus be useful for preventing shivering during induction of therapeutic hypothermia. We determined, therefore, whether ondansetron reduces the major autonomic thermoregulatory response thresholds (triggering core temperatures) in humans. METHODS: Control (placebo) and ondansetron infusions at the target plasma concentration of 250 ng ml(-1) were studied in healthy volunteers on two different days. Each day, skin and core temperatures were increased to provoke sweating; then reduced to elicit peripheral vasoconstriction and shivering. We determined the core-temperature sweating, vasoconstriction and shivering thresholds after compensating for changes in mean-skin temperature. Data were analysed using t-tests and presented as means (sds); P<0.05 was taken as significant. RESULTS: Ondensetron plasma concentrations were 278 (57), 234 (55) and 243 (58) ng ml(-1) at the sweating, vasoconstriction and shivering thresholds, respectively; these corresponded to approximately 50 mg of ondansetron which is approximately 10 times the dose used for postoperative nausea and vomiting. Ondansetron did not change the sweating (control 37.4 (0.4) degrees C, ondansetron 37.6 (0.3) degrees C, P=0.16), vasoconstriction (37.0 (0.5) degrees C vs 37.1 (0.3) degrees C; P=0.70), or shivering threshold (36.3 (0.5) degrees C vs 36.3 (0.6) degrees C; P=0.76). No sedation was observed on either study day. CONCLUSIONS: /b>. Ondansetron appears to have little potential for facilitating induction of therapeutic hypothermia.

Adult↗
PubMed2001

Buspirone and meperidine synergistically reduce the shivering threshold.

UNLABELLED: Mild hypothermia (i.e., 34 degrees C) may prove therapeutic for patients with stroke, but it usually provokes shivering. We tested the hypothesis that the combination of buspirone (a serotonin 1A partial agonist) and meperidine synergistically reduces the shivering threshold (triggering tympanic membrane temperature) to at least 34 degrees C while producing little sedation or respiratory depression. Eight volunteers each participated on four randomly-assigned days: 1) large-dose oral buspirone (60 mg); 2) large-dose IV meperidine (target plasma concentration of 0.8 microg/mL); 3) the combination of buspirone (30 mg) and meperidine (0.4 microg/mL); and 4) a control day without drugs. Core hypothermia was induced by infusion of lactated Ringer's solution at 4 degrees C. The control shivering threshold was 35.7 degrees C +/- 0.2 degrees C. The threshold was 35.0 degrees C +/- 0.8 degrees C during large-dose buspirone and 33.4 degrees C +/- 0.3 degrees C during large-dose meperidine. The threshold during the combination of the two drugs was 33.4 degrees C +/- 0.7 degrees C. There was minimal sedation on the buspirone and combination days and mild sedation on the large-dose meperidine day. End-tidal PCO2 increased approximately 10 mm Hg with meperidine alone. Buspirone alone slightly reduced the shivering threshold. The combination of small-dose buspirone and small-dose meperidine acted synergistically to reduce the shivering threshold while causing little sedation or respiratory toxicity. IMPLICATIONS: Mild hypothermia may be an effective treatment for acute stroke, but it usually triggers shivering, which could be harmful. Our results indicate that the combination of small-dose buspirone and small-dose meperidine acts synergistically to reduce the shivering threshold while causing little sedation or respiratory toxicity. This combination may facilitate the induction of therapeutic hypothermia in stroke victims.

Adult↗
PubMed2002

Dolasetron for preventing postanesthetic shivering.

UNLABELLED: 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.

Abdomen↗
PubMed1985

Postanesthetic shivering in primates: inhibition by peripheral heating and by taurine.

There has been little research on the cause(s) of postanesthetic shivering (PAS) and on specific interventions. Therefore, the authors investigated PAS in eight unoperated squirrel monkeys anesthetized with halothane-nitrous oxide mixture. Shivering developed in all monkeys in which body temperature was allowed to decrease (mean +/- SEM, 2.8 +/- 0.6 degrees C) during anesthesia. Shivering occurred in 25% of animals in which body temperature was actively maintained at preanesthetic levels during anesthesia. No shivering occurred in animals warmed both during and after anesthesia. Application of radiant heat to the skin stopped PAS immediately, even though deep body temperature remained low; shivering resumed within seconds after this heating was discontinued. Intracerebroventricular (0.1-2 mg) and intravenous (100 mg/kg) administration of the putative inhibitory neurotransmitter taurine also stopped the shivering in preliminary experiments, but central injection of alpha-melanocyte stimulating hormone (100-300 micrograms), an endogenous antipyretic, did not. The results implicate reduced body temperature and activation of central heat production pathways as major factors in PAS and suggest that halothane-nitrous oxide anesthesia per se, elevation of the thermal set-point, and surgical procedures are not essential to the shivering phenomenon. The results suggest for future study two methods to control PAS: application of radiant heat or administration of taurine.

Anesthesia, General↗
PubMed1996

Reduction in the shivering threshold is proportional to spinal block height.

BACKGROUND: Hypothermia is nearly as common, and may be as severe, during spinal and epidural anesthesia as during general anesthesia. The authors have proposed that thermoregulatory failure results when regional anesthesia increases apparent leg skin temperature to a level far exceeding actual leg skin temperature. Extensive dermatomal blocks will alter thermal input to the hypothalamus from a greater skin-surface area more than less extensive ones and thus might be expected to impair central thermoregulatory control more. Accordingly, they tested the hypothesis that reduction in the shivering threshold is directly related to the number of dermatomes blocked during spinal anesthesia. METHODS: Eleven men, aged 62 +/- 6 yr (mean +/- SD), undergoing urologic surgery were studied. Ice-cold lactated Ringer's solution was administered intravenously before spinal blockade and the shivering threshold (triggering core temperature) was established. Spinal anesthesia then was induced using a randomly assigned dose of 0.5% bupivacaine (2-4 ml). Again, sufficient cold lactated Ringer's solution was given to induce shivering. Tympanic membrane, ambient and skin temperatures were measured, and extent of block was defined by loss of temperature discrimination. Presence of shivering was evaluated by a blinded observer. Mean upper-body skin and ambient temperatures, cooling rates and intravenous fluid volumes at the two thresholds were compared using paired, two-tailed t tests (P < 0.05). Linear regression defined the relationship between reduction in shivering threshold and the number of dermatomes blocked. RESULTS: There were no significant differences between mean upper-body skin and ambient temperatures, cooling rates or intravenous fluid volumes at the control and spinal shivering thresholds. Spinal anesthesia reduced the shivering threshold in direct relation to the number of dermatomes blocked: delta threshold = 0.74 - 0.06 (dermatomes blocked); r2 = 0.58, P < 0.006. CONCLUSIONS: Extensive spinal blockade impairs central thermoregulatory control more than less extensive blockade. Clinicians can thus anticipate more core hypothermia during extensive than during restricted spinal blockade.

Aged↗
PubMed1995

The effects of pethidine, fentanyl and lignocaine on postanaesthetic shivering.

Pethidine is reported to be more effective than equi-analgesic doses of other opioids as an inhibitor of postanaesthetic shivering. The aim of this study was to verify whether this action resulted from a local anaesthetic effect of pethidine or from inadequate fentanyl dosage in previous studies. We studied 52 ASA 1 or 2 patients. They were randomly allocated, in a double-blind fashion, to one of four groups to receive either pethidine (0.85 mg.kg-1) or fentanyl (1.7 micrograms.kg-1) or lignocaine (1 mg.kg-1) or 0.9% saline. All the patients were shivering and had a core temperature below 36 degrees C during recovery from non-septic abdominal or orthopaedic surgery. After 15 min, all the patients given saline were still shivering, as were 92% in the lignocaine group. In contrast, only 23% of the patients who were given fentanyl still shivered (p < 0.01 versus saline) and 8% in the pethidine group (p < 0.001 versus saline). The mean (SD) core temperature in the pethidine group was slightly lower than that in the fentanyl group (35.1 (0.6) and 35.9 (0.5)) when the patients stopped shivering. Furthermore, shivering restarted in 6/10 patients in the fentanyl group after 15 min compared with 1/12 in the pethidine group. Our results show that fentanyl (1.7 micrograms.kg-1) can inhibit postanaesthetic shivering but this effect is less pronounced and of shorter duration than with pethidine (0.85 mg.kg-1).

Adult↗
PubMed1997

Tramadol in the treatment of postanesthetic shivering.

BACKGROUND: As an inhibitor of the reuptake of serotonin and norepinephrine in the spinal cord, the mechanism of action of tramadol resembles that of nefopam, which has been used in the treatment of postanesthetic shivering. METHODS: In a randomized, placebo-controlled, double-blind study, we assessed the effects of tramadol (0.5 mg.kg-1, 1 mg.kg-1 and 2 mg.kg-1 i.v.) or normal saline on shivering after a standardized general anesthesia in 40 adult patients, ASA physical status I or II (group 1), and in 64 adult patients regardless of the foregoing general anesthesia and ASA physical status (group 2). RESULTS: Tramadol 1 mg.kg-1 or more abolished shivering completely 5 min after treatment in all patients of groups 1 and 2. In group 1, the three dosages of tramadol were not statistically different in lowering the severity and prevalence of postanesthetic shivering. Tramadol 0.5 mg.kg-1 was significantly slower than tramadol 1 or 2 mg.kg-1 in tempering the severity as well as lowering the prevalence of postanesthetic shivering in group 2. CONCLUSION: Tramadol's distinct features in the treatment of shivering reside in its high safety profile and weak sedative properties, particularly in patients with poor cardiorespiratory reserve, in outpatients and on recurrence of shivering.

Adult↗
PubMed2005

Postoperative shivering in children and causative factors.

BACKGROUND: The aim of this study is to investigate the incidence of shivering in children and to reveal the causative factors as well as any possible clinical implications. METHODS: This study was conducted on 1507 children who underwent surgery under general anesthesia. The patients were admitted to the postanesthesia care unit after the operation and their body temperatures measured from the tympanic membrane. The type of operation, operative time, method of anesthesia induction, age, and number of cases in which caudal block had been used were recorded. RESULTS: Of the 1507 children, 53 (3.5%) experienced shivering. The use of intravenous induction agents, age older than 6 years, and prolonged duration of surgery were associated with shivering. The type of the operation and gender had no effect. The frequency of shivering was lower in children who underwent caudal block with a statistical significance (P < 0.05). CONCLUSIONS: The overall incidence of shivering in children is low (3.5%). Use of intravenous induction agents, age older than 6 years, and prolonged duration of surgery were associated with shivering; prophylaxis is not necessary in children, treatment is given only when shivering occurs.

Anesthesia, General↗
PubMed1983

Inhibition of shivering during restraint hypothermia.

Restraint hypothermia has often been described, but its cause has never been clarified. We hypothesized that it might be due to a suppression of shivering thermogenesis. Thus, we restrained conscious rats in an ambient temperature of 2 degrees C while measuring rectal (Tre) and tail skin temperatures, metabolic rate (MR), and shivering activity. When rats were cold exposed but not restrained, Tre fell 1.4 +/- 0.2 degrees C (SE) during the 1st h. When these same rats were restrained, Tre fell at a rate of 6.5 +/- 0.2 degrees C/h. MR averaged 15.7 +/- 1.4 W/kg for the unrestrained rats, but it averaged only 9.0 +/- 1.1 W/kg for the restrained rats. The restrained rats showed no signs of shivering. The animals were then subjected to a restraint adaptation regimen and then reexposed to cold. Restraint now produced a fall in Tre of only 2.6 +/- 0.7 degrees C/h. The animals shivered and generated an MR of 15.8 +/- 0.9 W/kg. Naive rats became hypothermic because restraint suppressed shivering activity. However, adapted rats continued to shiver and remained normothermic. We suggest that a stressful or threatening situation, such as restraint for a naive rat, inhibits shivering and leads to hypothermia in a cold environment. This would not occur in adapted rats because restraint is no longer stressful.

Adaptation, Psychological↗
PubMed2005

Inhibition of shivering in hypothermic seals during diving.

The mammalian response to hypothermia is increased metabolic heat production, usually by way of muscular activity, such as shivering. Seals, however, have been reported to respond to diving with hypothermia, which in other mammals under other circumstances would have elicited vigorous shivering. In the diving situation, shivering could be counterproductive, because it obviously would increase oxygen consumption and therefore reduce diving capacity. We have measured the electromyographic (EMG) activity of three different muscles and the rectal and brain temperature of hooded seals (Cystophora cristata) while they were exposed to low ambient temperatures in a climatic chamber and while they performed a series of experimental dives in cold water. In air, the seals had a normal mammalian shivering response to cold. Muscles were recruited in a sequential manner until body temperature stopped dropping. Shivering was initiated when rectal temperature fell below 35.3 +/- 0.6 degrees C (n = 6). In the hypothermic diving seal, however, the EMG activity in all of the muscles that had been shivering vigorously before submergence was much reduced, or stopped altogether, whereas it increased again upon emergence but was again reduced if diving was repeated. We conclude that shivering is inhibited during diving to allow a decrease in body temperature whereby oxygen consumption is decreased and diving capacity is extended.

Air↗
PubMed1991

Shivering onset, metabolic response, and convective heat transfer during cold air exposure.

The onset and intensity of shivering of various muscles during cold air exposure are quantified and related to increases in metabolic rate and convective heat loss. Thirteen male subjects resting in a supine position and wearing only shorts were exposed to 10 degrees C air (42% relative humidity and less than 0.4 m/s airflow) for 2 h. Measurements included surface electromyogram recordings at six muscle sites representing the trunk and limb regions of one side of the body, temperatures and heat fluxes at the same contralateral sites, and metabolic rate. The subjects were grouped according to lean (LEAN, n = 6) and average body fat (NORM, n = 7) content. While the rectal temperatures fluctuated slightly but not significantly during exposure, the skin temperature decreased greatly, more at the limb sites than at the trunk sites. Muscles of the trunk region began to shiver sooner and at a higher intensity than those of the limbs. The intensity of shivering and its increase over time of exposure were consistent with the increase in the convective heat transfer coefficient calculated from skin temperatures and heat fluxes. Both the onset of shivering and the magnitude of the increase in metabolic rate due to shivering were higher for the LEAN group than for the NORM group. A regression analysis indicates that, for a given decrease in mean skin temperature, the increase in metabolic rate due to shivering is attenuated by the square root of percent body fat. Thus the LEAN group shivered at higher intensity, resulting in higher increases in metabolic heat production and convective heat loss during cold air exposure than did the NORM group.

Adipose Tissue↗
PubMed2003

Dexmedetomidine and meperidine additively reduce the shivering threshold in humans.

BACKGROUND AND PURPOSE: Hypothermia might prove to be therapeutically beneficial in stroke victims; however, even mild hypothermia provokes vigorous shivering. Meperidine and dexmedetomidine each linearly reduce the shivering threshold (triggering core temperature) with minimal sedation. We tested the hypothesis that meperidine and dexmedetomidine synergistically reduce the shivering threshold without producing substantial sedation or respiratory depression. METHODS: We studied 10 healthy male volunteers (18 to 40 years) on 4 days: (1) control (no drug); (2) meperidine (target plasma level 0.3 microg/mL); (3) dexmedetomidine (target plasma level 0.4 ng/mL); and (4) meperidine plus dexmedetomidine (target plasma levels of 0.3 microg/mL and 0.4 ng/mL, respectively). Lactated Ringer's solution (approximately 4 degrees C) was infused through a central venous catheter to decrease tympanic membrane temperature by approximately 2.5 degrees C/h; mean skin temperature was maintained at 31 degrees C. An increase in oxygen consumption >25% of baseline identified the shivering threshold. Sedation was evaluated by using the Observer's Assessment of Sedation/Alertness scale. Two-way repeated-measures ANOVA was used to identify interactions between drugs. Data are presented as mean+/-SD; P<0.05 was statistically significant. RESULTS: The shivering thresholds on the study days were as follows: control, 36.7+/-0.3 degrees C; dexmedetomidine, 36.0+/-0.5 degrees C (P<0.001 from control); meperidine, 35.5+/-0.6 degrees C (P<0.001); and meperidine plus dexmedetomidine, 34.7+/-0.6 degrees C (P<0.001). Although meperidine and dexmedetomidine each reduced the shivering threshold, their interaction was not synergistic but additive (P=0.19). There was trivial sedation with either drug alone or in combination. Respiratory rate and end-tidal Pco2 were well preserved on all days. CONCLUSIONS: Dexmedetomidine and meperidine additively reduce the shivering threshold; in the small doses tested, the combination produced only mild sedation and no respiratory toxicity.

Adolescent↗
PubMed2001

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.

Adult↗
PubMed2003

Doxapram produces a dose-dependent reduction in the shivering threshold in rabbits.

Dopamine is a thermoregulatory neurotransmitter that provokes hypothermia when injected in or near the hypothalamus. Doxapram stimulates release of dopamine from carotid bodies, but is known to have central effects that are probably, at least in part, similarly mediated. We thus tested the hypothesis that doxapram produces a substantial, dose-dependent reduction in the shivering threshold in rabbits. Twenty-four rabbits, anesthetized with isoflurane, were randomly assigned to 1) saline (control), 2) 0.25 mg x kg(-1) x h(-1) doxapram, or 3) 0.50 mg x kg(-1) x h(-1) doxapram. These doses are within the recommended range for humans. Body temperature was reduced at a rate of 2 degrees to 3 degrees C/h by perfusing water at 10 degrees C through a U-shaped thermode positioned in the colon. Core temperatures were recorded from the distal esophagus. A blinded observer evaluated shivering. Core temperature at the onset of shivering defined the threshold. Data were analyzed with a one-way analysis of variance; P < 0.05 was considered statistically significant. Hemodynamic and respiratory responses were comparable in the groups. The control rabbits shivered at 36.3 degrees +/- 0.3 degrees C, those given 0.25 mg x kg(-1) x h(-1) doxapram shivered at 34.8 degrees +/- 0.5 degrees C, and those given 0.50 mg x kg(-1) x h(-1) shivered at 33.7 degrees +/- 0.6 degrees C. All the shivering thresholds significantly (P < 0.001) differed from one another. The magnitude of this inhibition, if similar in humans, would be clinically important.

Anesthesia, Inhalation↗
PubMed2004

Intrathecal meperidine decreases shivering during cesarean delivery under spinal anesthesia.

UNLABELLED: Shivering associated with spinal anesthesia is uncomfortable and may interfere with monitoring. We performed this prospective, double-blinded, and randomized study to determine whether intrathecal meperidine (0.2 mg/kg) decreases the incidence and intensity of shivering after spinal anesthesia for cesarean delivery. Forty parturients scheduled for nonemergent cesarean delivery were enrolled in two groups. Spinal anesthesia consisted of hyperbaric bupivacaine (0.75%; 10.5 mg), morphine 0.15 mg, and, in the experimental group, meperidine (0.2 mg/kg) or, in the control group, normal saline. Data collection, including sensory block level, blood pressure, core temperature, and shivering intensity, was performed every minute for 10 min, every 3 min for 33 min, and then every 5 min until the sensory level receded to L4. Time to highest sensory level, maximum number of blocked segments, sensory and motor blockade regression, and systolic blood pressure showed no difference between groups. The incidence of shivering was less (P < 0.02) in the meperidine group, as was its intensity (P < 0.003). Intrathecal meperidine (0.2 mg/kg) is effective in reducing the incidence and intensity of shivering associated with spinal anesthesia for cesarean delivery. IMPLICATIONS: Previous studies have suggested that IV meperidine is helpful for treating intraoperative shivering. This study was undertaken to evaluate spinal meperidine and found that it decreases the incidence and intensity of shivering associated with spinal anesthesia for cesarean delivery.

Adult↗