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

Development and internal validation of an algorithm to predict intraoperative risk of inadvertent hypothermia based on preoperative data

Intraoperative hypothermia increases perioperative morbidity and identifying patients at risk preoperatively is challenging. The aim of this study was to develop and internally validate prediction models for intraoperative hypothermia occurring despite active warming and to implement the algorithm in an online risk estimation tool. The final dataset included 36,371 surgery cases between September 2013 and May 2019 at the Vienna General Hospital. The primary outcome was minimum temperature measured during surgery. Preoperative data, initial vital signs measured before induction of anesthesia, and known comorbidities recorded in the preanesthetic clinic (PAC) were available, and the final predictors were selected by forward selection and backward elimination. Three models with different levels of information were developed and their predictive performance for minimum temperature below 36 °C and 35.5 °C was assessed using discrimination and calibration. Moderate hypothermia (below 35.5 °C) was observed in 18.2% of cases. The algorithm to predict inadvertent intraoperative hypothermia performed well with concordance statistics of 0.71 (36 °C) and 0.70 (35.5 °C) for the model including data from the preanesthetic clinic. All models were well-calibrated for 36 °C and 35.5 °C. Finally, a web-based implementation of the algorithm was programmed to facilitate the calculation of the probabilistic prediction of a patient's core temperature to fall below 35.5 °C during surgery. The results indicate that inadvertent intraoperative hypothermia still occurs frequently despite active warming. Additional thermoregulatory measures may be needed to increase the rate of perioperative normothermia. The developed prediction models can support clinical decision-makers in identifying the patients at risk for intraoperative hypothermia and help optimize allocation of additional thermoregulatory interventions.

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.

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.

Compartmental pharmacokinetics of nefopam during mild hypothermia

BACKGROUND

Nefopam is a non-opioid, non-steroidal, centrally acting analgesic which has an opioid-sparing effect. It also reduces the threshold (triggering core temperature) for shivering without causing sedation or respiratory depression. The drug is therefore useful as both an analgesic and to facilitate induction of therapeutic hypothermia. However, compartmental pharmacokinetics during hypothermia are lacking for nefopam.

METHODS

We conducted a prospective, randomized, blinded study in eight volunteers. On two different occasions, one of two nefopam concentrations was administered and more than 30 arterial blood samples were gathered during 12 h. Plasma concentrations were determined using gas chromatography/mass spectrometry to investigate the pharmacokinetics of nefopam with non-linear mixed-effect modelling.

RESULTS

A two-compartment mammillary model with moderate inter-individual variability and inter-occasional variability independent of covariates was found to best describe the data [mean (SE): V(1)=24.13 (2.8) litre; V(2)=183.34 (13.5) litre; Cl(el)=0.54 (0.07) litre min(-1); Cl(dist)=2.84 (0.42) litre min(-1)].

CONCLUSIONS

The compartmental data set describing a two-compartment model was determined and could be implemented to drive automated pumps. Thus, work load could be distributed to a pump establishing and maintaining any desired plasma concentration deemed necessary for a treatment with therapeutical hypothermia.

The Efficacy of Epidural Ketamine on Shivering during Transurethral Resection of the Prostate under Epidural Anesthesia

PURPOSE

Ketamine may decrease core-to-peripheral redistribution of heat through direct central sympathetic stimulation and inhibition of norepinephrine uptake into postganglionic sympathetic nerve endings. The purpose of this study was to evaluate the efficacy of epidural ketamine in preventing shivering during transurethral resection of the prostate (TURP) under epidural anesthesia.

MATERIALS AND METHODS

Ninety-three male patients scheduled for TURP under epidural anesthesia were enrolled in this study. Patients were randomized into one of three groups. Group 1 consisted of 31 patients who received epidural 0.75% ropivacaine, group 2 consisted of 32 patients who received epidural ketamine (0.2 mg/kg) in addition to 0.75% ropivacaine, and group 3 consisted of 30 patients who received epidural ketamine (0.4 mg/kg) in addition to 0.75% ropivacaine. Shivering and side effects such as hypotension, bradycardia, nausea, and hallucination were recorded during the anesthesia and for 2 hours while in the postanesthetic recovery room.

RESULTS

Shivering was statistically more frequent in group 1 than in the other groups. The incidence of sedation was significantly higher in group 3 than in the other groups. The incidences of side effects such as hypotension, bradycardia, and nausea were significantly higher in group 1 than in the other groups.

CONCLUSIONS

In this study, epidural ketamine 0.2 mg/kg and 0.4 mg/kg was shown to have a lower incidence of shivering and other side effects except sedation. In patients who undergo TURP under epidural anesthesia, the prophylactic use of low-dose epidural ketamine would be helpful in preventing any adverse effects, including shivering.

The effects of nefopam on the gain and maximum intensity of shivering in healthy volunteers

BACKGROUND

Mild hypothermia has been shown to improve neurologic outcome after cardiac arrest. Nefopam, a centrally acting, nonsedative analgesic, decreases the threshold of shivering, but not vasoconstriction, and thus might be a suitable drug for induction of therapeutic hypothermia. However, not only the threshold but also the gain and maximum intensity of shivering define the thermoregulatory properties of a drug and thus are clinically important. Therefore, we evaluated the gain and maximum intensity of shivering at 2 different doses of nefopam and placebo.

METHODS

Seven healthy volunteers were randomly assigned to 3 study days: (1) control (saline), (2) small-dose nefopam (50 ng/mL), and (3) large-dose nefopam (100 ng/mL). On all study days volunteers were cooled using central venous infusion of cold IV fluid while mean skin temperature was maintained at 31 degrees C. Core temperature was recorded at the tympanic membrane. Threshold, gain, and maximum intensity of shivering were evaluated using oxygen consumption.

RESULTS

Both 50 and 100 ng/mL nefopam significantly reduced the shivering threshold as well as the gain of shivering: shivering threshold: 35.6 degrees C + or - 0.2 degrees C (control); 35.2 degrees C + or - 0.3 degrees C (small dose); 34.9 degrees C + or - 0.5 degrees C (large dose), P = 0.004; gain of shivering: 597 + or - 235 mL x min(-1) x degrees C(-1) (control); 438 + or - 178 mL x min(-1) x degrees C(-1) (small dose); 301 + or - 134 mL x min(-1) x degrees C(-1) (large dose), P = 0.028. Maximum intensity of shivering did not differ among the 3 treatments.

CONCLUSIONS

Nefopam significantly reduced the gain of shivering. This reduction, in combination with a reduced shivering threshold, will allow clinicians to cool patients even further when therapeutic hypothermia is indicated.

Effect of shivering on brain tissue oxygenation during induced normothermia in patients with severe brain injury

BACKGROUND

We analyzed the impact of shivering on brain tissue oxygenation (PbtO(2)) during induced normothermia in patients with severe brain injury.

METHODS

We studied patients with severe brain injury who developed shivering during induced normothermia. Induced normothermia was applied to treat refractory fever (body temperature [BT] > or =38.3 degrees C, refractory to conventional treatment) using a surface cooling device with computerized adjustment of patient BT target to 37 +/- 0.5 degrees C. PbtO(2), intracranial pressure, mean arterial pressure, cerebral perfusion pressure, and BT were monitored continuously. Circulating water temperature of the device system was measured to assess the intensity of cooling.

RESULTS

Fifteen patients (10 with severe traumatic brain injury, 5 with aneurysmal subarachnoid hemorrhage) were treated with induced normothermia for an average of 5 +/- 2 days. Shivering caused a significant decrease in PbtO(2) levels both in SAH and TBI patients. Compared to baseline, shivering was associated with an overall reduction of PbtO(2) from 34.1 +/- 7.3 to 24.4 +/- 5.5 mmHg (P < 0.001). A significant correlation was found between the magnitude of shivering-associated decrease of PbtO(2) (DeltaPbtO(2)) and circulating water temperature (R = 0.82, P < 0.001).

CONCLUSION

In patients with severe brain injury treated with induced normothermia, shivering was associated with a significant decrease of PbtO(2), which correlated with the intensity of cooling. Monitoring of therapeutic cooling with computerized thermoregulatory systems may help prevent shivering and optimize the management of induced normothermia. The clinical significance of shivering-induced decrease in brain tissue oxygenation remains to be determined.

Early postoperative cognitive recovery and gas exchange patterns after balanced anesthesia with sevoflurane or desflurane in overweight and obese patients undergoing craniotomy: a prospective randomized trial

Overweight and obese patients are at especially high risk for delayed awakening after general surgery. Whether this risk also applies to cerebral neurosurgical procedures remains unclear. This study evaluated early postoperative cognitive recovery and gas exchange patterns, after balanced anesthesia with sevoflurane or desflurane, in overweight and obese patients undergoing craniotomy for supratentorial expanding lesions. Fifty-six patients were consecutively enrolled, and randomly assigned to 1 of 2 study groups to receive balanced anesthesia with sevoflurane or desflurane. Cognitive function was evaluated with the Short Orientation Memory Concentration Test and the Rancho Los Amigos Scale and gas exchange patterns (pH, PaO2, and PaCO2) were recorded in all patients at 5 time-points: preoperatively and postoperatively, after patients reached an Aldrete score >or=9, at 15, 30, 45, and 60 minutes. Preoperative cognitive status was similar in the 2 treatment groups. Early postoperative cognitive recovery was more delayed and Short Orientation Memory Concentration Test scores at 15 and 30 minutes postanesthesia were lower in patients receiving sevoflurane-based anesthesia than in those receiving desflurane-based anesthesia (21.5+/-3.5 vs. 14.9+/-3.5) (P<0.005) and (26.9+/-0.7 vs. 21.5+/-1.4) (P<0.005), and the postoperative Rancho Los Amigos Scalegrade 8 showed a similar trend (25/28 patients 89% vs. 8/28 patients 28% (P<0.005) and 28/28 patients (100% vs. 13/28 patients 46%) (P<0.005). Similarly, gas-exchange analysis showed higher PaCO2 at 15 and 30 minutes and lower pH up to 45 minutes postextubation in patients receiving sevoflurane-based anesthesia. In overweight and obese patients undergoing craniotomy desflurane-based anesthesia allows earlier postoperative cognitive recovery and reversal to normocapnia and normal pH.

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.

Esmolol blunts postoperative hemodynamic changes after propofol-remifentanil total intravenous fast-track neuroanesthesia for intracranial surgery

STUDY OBJECTIVE

To investigate whether esmolol is effective in attenuating postoperative hemodynamic changes related to sympathetic overdrive.

DESIGN

Clinical study.

SETTING

Operating room of a university hospital.

PATIENTS

60 ASA physical status I, II, and III patients, age 18 to 65 years, scheduled for elective craniotomy for supratentorial neurosurgery.

INTERVENTIONS

Patients were given total intravenous anesthesia (TIVA) during emergence from anesthesia and up to 60 minutes after extubation. Those patients who had hypertension (defined as an increase in systolic blood pressure >20% from baseline values) and tachycardia (defined as an increase >20% in heart rate from baseline) received a loading dose of 500 microg/kg esmolol in one minute, followed by an infusion titrated stepwise (50, 100, 200, and 300 microg/kg per min) every two minutes.

MEASUREMENTS

The mean dose and duration of esmolol therapy were measured.

MAIN RESULTS

Of 60 patients, 49 (82%) who received propofol-remifentanil TIVA developed significant tachycardia and hypertension soon after extubation. Treatment with esmolol (500 microg/kg in bolus maintained at a mean rate of 200 +/- 50 microg/kg per min) effectively controlled hypertension and tachycardia in 45 of 49 patients (92%; P < 0.05) within a mean 4.30 +/- 2.20 minutes. After extubation, mean esmolol infusion time was 29 +/- 8 minutes.

CONCLUSION

In patients undergoing elective neurosurgery with propofol-remifentanil TIVA, a relatively small esmolol dose and short infusion time effectively blunts early postoperative arterial hypertension and tachycardia.

Dexmedetomidine and postoperative shivering in patients undergoing elective abdominal hysterectomy

BACKGROUND

Post-anaesthetic shivering is one of the most common complications, occurring in 5-65% of patients recovering from general anaesthesia and 33% of patients receiving epidural anaesthesia. Our objective was to investigate the efficacy of intraoperative dexmedetomidine infusion on postoperative shivering.

METHODS

Ninety female patients, ASA I-II, 35-60 yr old, scheduled for elective total abdominal hysterectomy with or without bilateral salpingo-oophorectomy were randomized into two groups. After endotracheal intubation one group received normal saline infusion and the other received dexmedetomidine as a loading dose of 1 microg kg(-1) for 10 min followed by a maintenance infusion of 0.4 microg kg(-1) h(-1). In the recovery room, pain was assessed using a 100 mm visual analogue scale and those patients who had a pain score of more than 40 mm were administered 1 mg kg(-1) intramuscular diclofenac sodium. Patients with shivering grades more than 2 were administered 25 mg intravenous meperidine. Patients were protected with passive insulation covers.

RESULTS

Post-anaesthetic shivering was observed in 21 patients in the saline group and in seven patients in the dexmedetomidine group (P = 0.001). Shivering occurred more often in the saline group. The Ramsay Sedation Scores were higher in the dexmedetomidine group during the first postoperative hour. Pain scores were higher in the saline group for 30 min after the operation. The need for intraoperative atropine was higher in the dexmedetomidine group. Intraoperative fentanyl use was higher in the saline group. Perioperative tympanic temperatures were not different between the groups whereas postoperative measurements were lower in the dexmedetomidine group (P < 0.05).

CONCLUSION

Intraoperative dexmedetomidine infusion may be effective in the prevention of post-anaesthetic shivering.

Awakening management after neurosurgery for intracranial tumours

PURPOSE OF REVIEW

Major complications after intracranial surgery occur in 13-27% of patients. These complications may have multiple causes, but a body of arguments suggests that the haemodynamic and metabolic changes of anaesthesia recovery may be responsible for intracranial complications. The aim of this review is to explain the rationale of this hypothesis and analyse the recent studies relevant to neuroanaesthesia recovery.

RECENT FINDINGS

Rapid recovery and extubation after intracranial tumour surgery is desirable in order to make an early diagnosis of intracranial complications. Since light pharmacological sedation may worsen a neurological deficit, short-acting anaesthetics are preferable intraoperatively. Extubation in the operating room, however, may be associated with agitation, increased oxygen consumption, catecholamine secretion, hypercapnia and systemic hypertension. This may exacerbate cerebral hyperaemia observed even during an uneventful recovery, leading to cerebral oedema or haemorrhage.

SUMMARY

Pain, hypothermia, hypercapnia, hypoxia, hypoosmolality, hypertension, and anaemia should be avoided during emergence. Early emergence is associated with minimal haemodynamic and metabolic changes. If there is any doubt as to whether the patient should be extubated in the operating room, a gradual emergence in the intensive care unit makes it possible to decide whether or not extubation can be performed safely.

Early postoperative cognitive recovery after remifentanil–propofol or sufentanil–propofol anaesthesia for supratentorial craniotomy: a randomized trial

BACKGROUND AND OBJECTIVE

This study was designed to evaluate early postoperative cognitive recovery after total intravenous anaesthesia with remifentanil-propofol or sufentanil-propofol in patients undergoing craniotomy for supratentorial expanding lesions.

METHODS

Sixty patients were consecutively enrolled, and randomly assigned to one of two study groups: remifentanil-propofol or sufentanil-propofol anaesthesia. To evaluate cognitive function the Short Orientation Memory Concentration Test (SOMCT) and Rancho Los Amigos Scale (RLAS) were administered to all patients in a double-blind procedure before surgery at 15, 45 min and 3 h after extubation.

RESULTS

Mean extubation time was similar in the two groups (13 +/- 5 min vs. 19 +/- 6 min). A significantly larger number of patients in the remifentanil-propofol group than in the sufentanil-propofol group required antihypertensive medication postoperatively to maintain mean arterial pressure within 20% of baseline (18/30 vs. 4/29; P = 0.0004). Intergroup analysis showed no differences in baseline SOMCT scores (28 +/- 1 vs. 28 +/- 1) whereas mean SOMCT scores at 15, 45 min and 3 h after extubation were significantly higher in the remifentanil-propofol group (30 patients) than in the sufentanil-propofol group (29 patients) (22 +/- 3 vs. 16 +/- 3; P < 0.0001 and 27 +/- 1 vs. 22 +/- 3; P < 0.0001; 28 +/- 1 vs. 26 +/- 2; P = 0.0126).

CONCLUSIONS

In conclusion, propofol-remifentanil and propofol-sufentanil are both suitable for fast-track neuroanaesthesia and provide similar intraoperative haemodynamics, awakening and extubation times. Despite a higher risk of treatable postoperative hypertension propofol-remifentanil allows earlier cognitive recovery.

[Pain management in subarachnoid haemorrhage: a survey of French analgesic practices]

OBJECTIVE

Pain management in patients having a subarachnoid haemorrhage was assessed in French intensive care unit of neurosurgical centres.

STUDY DESIGN

Nationwide survey.

METHODS

A standardized postal questionnaire was sent to senior doctor of every neurosurgical centres in France inquiring pain scores assessment, analgesics used and their routes of administration, centre's opinion about efficacy of pain management.

RESULTS

Of the 34 centres, 24 returned completed questionnaires. Fifty four per cent of the centres evaluated pain intensity with a non valid pain score. In the case of patients in the comatose, pain was not evaluated in fifty four per cent of the centres. Paracetamol and morphine were the most currently used analgesics drugs. Morphine was administered subcutaneously by 75% of the centres. Six centres used also PCA. Thirty-seven percent of the centres were reluctant to use opioids and 75% to use NSAIDS.

CONCLUSION

The majority of the centres considered pain management in patient suffering from subarachnoid haemorrhage (SAH) was not optimal and stressed the need to establish a well validated pain rating scale dedicated to SAH patients.

Hypothermia in a surgical intensive care unit

BACKGROUND

Inadvertent hypothermia is not uncommon in the immediate postoperative period and it is associated with impairment and abnormalities in various organs and systems that can lead to adverse outcomes. The aim of this study was to estimate the prevalence, the predictive factors and outcome of core hypothermia on admission to a surgical ICU.

METHODS

All consecutive 185 adult patients who underwent scheduled or emergency noncardiac surgery admitted to a surgical ICU between April and July 2004 were admitted to the study. Tympanic membrane core temperature (Tc) was measured before surgery, on arrival at ICU and every two hours until 6 hours after admission. The following variables were also recorded: age, sex, body weight and height, ASA physical status, type of surgery, magnitude of surgical procedure, anesthesia technique, amount of intravenous fluids administered during anesthesia, use of temperature monitoring and warming techniques, duration of the anesthesia, ICU length of stay, hospital length of stay and SAPS II score. Patients were classified as either hypothermic (Tc < or = 35 degrees C) or normothermic (Tc> 35 degrees C). Univariate analysis and multiple regression binary logistic with an odds ratio (OR) and its 95% Confidence Interval (95%CI) were used to compare the two groups of patients and assess the relationship between each clinical predictor and hypothermia. Outcome measured as ICU length of stay and mortality was also assessed.

RESULTS

Prevalence of hypothermia on ICU admission was 57.8%. In univariate analysis temperature monitoring, use of warming techniques and higher previous body temperature were significant protective factors against core hypothermia. In this analysis independent predictors of hypothermia on admission to ICU were: magnitude of surgery, use of general anesthesia or combined epidural and general anesthesia, total intravenous crystalloids administrated and total packed erythrocytes administrated, anesthesia longer than 3 hours and SAPS II scores. In multiple logistic regression analysis significant predictors of hypothermia on admission to the ICU were magnitude of surgery (OR 3.9, 95% CI, 1.4-10.6, p = 0.008 for major surgery; OR 3.6, 95% CI, 1.5-9.0, p = 0.005 for medium surgery), intravenous administration of crystalloids (in litres) (OR 1.4, 95% CI, 1.1-1.7, p = 0.012) and SAPS score (OR 1.0, 95% CI 1.0-1.7, p = 0.014); higher previous temperature in ward was a significant protective factor (OR 0.3, 95% CI 0.1-0.7, p = 0.003). Hypothermia was neither a risk factor for hospital mortality nor a predictive factor for staying longer in ICU.

CONCLUSION

The prevalence of patient hypothermia on ICU arrival was high. Hypothermia at time of admission to the ICU was not an independent factor for mortality or for staying longer in ICU.

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.

Older people and hypothermia: the role of the anaesthetic nurse

Older clients are at increased risk during surgical intervention because of age-related system changes and comorbid conditions. However, recent advances in surgical and anaesthetic techniques, together with modern monitoring technology and the proliferation of ambulatory surgery, have reduced mortality in older patients undergoing surgery. Nevertheless, inadvertent hypothermia in older clients remains problematic. Therefore, an understanding of specific diseases prevalent in old age, coupled with a comprehensive knowledge of the physiological impact of ageing in all body systems, underpins the role of the anaesthetic nurse.

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.

Consequences of inadvertent perioperative hypothermia

Perioperative hypothermia triples the incidence of adverse myocardial outcomes in high-risk patients. Mild hypothermia significantly increases blood loss and augments allogeneic transfusion requirement, but the molecular pathophysiology of this effect remains to be elucidated. 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. Mild perioperative hypothermia changes the kinetics and action of various anaesthetic and paralysing agents, increases thermal discomfort, and is associated with delayed post-anaesthetic recovery. Finally, mild core hypothermia influences pulse oximetry monitoring and various electrophysiological indices of the nervous system, with questionable clinical significance, as yet.

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.