|Year : 2020 | Volume
| Issue : 3 | Page : 260-266
Forced air-warming blanket versus pethidine for the prevention of shivering during and after caesarean section
Mohamed H Agamia, Ahmed R Morsy, Mervat M Abd Al-Maksod, Rehab A Abd El Aziz
Department of Anaesthesia and Surgical Intensive Care Unit, Faculty of Medicine, Alexandria University, Egypt
|Date of Submission||08-Nov-2016|
|Date of Acceptance||17-Dec-2017|
|Date of Web Publication||29-Sep-2020|
Master of Anaesthesia, MBBch Mohamed H Agamia
Department of Anaesthesia and Surgical Intensive Care, Faculty of Medicine, Alexandria University, Al
Azarita square, 21131
Source of Support: None, Conflict of Interest: None
Background Spinal anaesthesia significantly impairs thermoregulation by inhibiting vasomotor and shivering responses and by redistributing heat from the core of body to peripheral tissues. Core hypothermia may be associated with a number of adverse outcomes in pregnant women, including shivering, wound infection, coagulopathy, increased blood loss and transfusion requirements. Several pharmacological and mechanical methods have been used in an attempt to maintain normothermia and prevent intra-anaesthetic and postanaesthetic shivering. Therefore, the aim of the present study was to compare the efficacy of prophylactic use of forced air-warming blanket with pethidine for the prevention of shivering during and after spinal anaesthesia in elective caesarean section.
Patients and methods The present study included 96 pregnant women with ASA I and II, admitted to Al Shatby Maternity Hospital. Patients were randomly assigned into three equal groups of 32 patients each. Group I patients were covered with forced air-warming blanket over the upper limbs and chest, group II patients received a single bolus of 0.5 mg/kg pethidine intravenously and group III patients did not receive anything, and they were regarded as control.
Results Heart rate and mean arterial blood pressure decreased significantly in all the three studied groups after spinal anaesthesia. The decrease in the mean arterial blood pressure required ephedrine boluses, which ranged between 0 and 4 boluses, with no significance between the three studied groups. The core body temperature decreased significantly 15 min after spinal anaesthesia and thereafter in all patients of the three studied groups. However, the decrease in core temperature was significantly more in groups II and III. The shivering score increased significantly 10 min after spinal anaesthesia and thereafter intraoperatively. The shivering scores were significantly lower in groups I and II when compared with group III. There was a negative correlation between core body temperature and shivering scores in all the three studied groups. The mean core body temperature for shivering patients was significantly less in group II patients compared with groups I and III patients. The three groups were matched as regard to APGAR score at 1 and 5 min. No significant changes were observed as regard to hypotension, nausea, vomiting and feeling cold extremities.
Conclusion Forced air-warming blanket decreased the shivering incidence by preserving core body temperature, whereas pethidine can prevent and treat shivering.
Keywords: core body temperature, shivering, spinal anaesthesia
|How to cite this article:|
Agamia MH, Morsy AR, Abd Al-Maksod MM, Abd El Aziz RA. Forced air-warming blanket versus pethidine for the prevention of shivering during and after caesarean section. Res Opin Anesth Intensive Care 2020;7:260-6
|How to cite this URL:|
Agamia MH, Morsy AR, Abd Al-Maksod MM, Abd El Aziz RA. Forced air-warming blanket versus pethidine for the prevention of shivering during and after caesarean section. Res Opin Anesth Intensive Care [serial online] 2020 [cited 2020 Oct 23];7:260-6. Available from: http://www.roaic.eg.net/text.asp?2020/7/3/260/296621
| Introduction|| |
Spinal anaesthesia significantly impairs thermoregulation by inhibiting vasomotor and shivering responses and by redistributing heat from the core of the body to peripheral tissues . Hypothermia is usually defined as a body temperature less than 36°C that occurs commonly during surgery. Core hypothermia may be associated with a number of adverse outcomes in pregnant women, including shivering, wound infection, coagulopathy, increase in blood loss and transfusion requirements, decrease in metabolism, and prolonged recovery. Perioperative shivering can occur in up to 55% of patients undergoing caesarean delivery under regional anaesthesia .
Several pharmacological and mechanical methods have been used in an attempt to maintain normothermia in the operating room and to prevent postanaesthetic shivering. Pharmacological method includes usage of drugs such as pethidine, ketamine, tramadol, doxapram and dexmedetomidine ,. Mechanical methods include circulating-water, forced-air, and resistive-heating techniques .
Therefore, the aim of the present study was to compare the efficacy of prophylactic use of forced air-warming blanket with intravenous pethidine for the prevention of shivering during and after spinal analgesia in elective caesarean section.
| Patients and methods|| |
The present study included 96 pregnant women who were admitted to Al Shatby Maternity Hospital and were undergoing elective caesarean section under spinal anaesthesia. All patients were of ASA physical status I and II and their ages ranged between 20 and 35 years.
Patients were randomly assigned into three equal groups (32 patients each) using closed envelops technique according to the drug or instrument used.
Group I: patients in this group were covered with a forced air-warming blanket covering the upper limbs and the chest.
Group II: patients in this group received a single bolus dose of pethidine 0.5 mg/kg intravenously.
Group III: patients in this group did not receive anything, and were considered as control.
Patients with hypothyroidism or hyperthyroidism, BMI more than 35, psychological disorders, an initial body temperature more than 38°C or less than 36°C, patients receiving vasodilators or medications that likely to alter thermoregulation, pregnancy-induced hypertension and patients with any surgical complication were excluded from the study.
After obtaining approval from the local ethical committee, informed written consents were taken from all the patients included in the study. All patients were assessed thoroughly by detailed medical and surgical history, full clinical examination, and all routine laboratory investigations.
At the operating room, patients were connected to Dräger Infinity Vista Monitor (Dräger, Germany), which includes pulse oximetry, ECG and noninvasive arterial blood pressure. No premedication was given. All patients received 500 ml preheated (∼37°C) normal saline as a preload.
Intraoperative intravenous fluids were preheated to 37°C in a water bath and then were infused using a blood-warmer device. Heavy bupivacaine was warmed to room temperature (22–26°C) before injection.
After infiltrating the skin and subcutaneous tissue with 3 ml of 2% lidocaine under complete aseptic condition, subarachnoid block was achieved using 2.5 ml heavy bupivacaine 0.5% at L3–L4 or L4–L5 lumbar interspace using 25-G Quinke spinal needle, BD, USA. Just after intrathecal injection and positioning, group I patients were covered by the warming blanket (3M Bair Hugger 500, Bair Hugger, USA) at the highest fan speed with the temperature of 43°C; whereas patients in group II received 0.5 mg/kg intravenous pethidine. Urinary catheter was inserted and urine output was measured. Supplementary oxygen (5 l/min) was delivered by a facemask during the operation. Core body temperature was measured using Braun ThermoScan 5 Ear Thermometer, Braun, Germany. The presence of shivering was observed and graded after spinal anaesthesia, according to the following scale: 0=no shivering, 1=piloerection or peripheral vasoconstriction but no visible shivering, 2=muscular activity in only one muscle group, 3=muscular activity in more than one muscle group but not generalized, 4=shivering involving the whole body. If shivering reached a score of 3 or 4 for any patients of the three groups, a therapeutic dose of 0.5 mg/kg intravenous pethidine was administered.
Heart rate was monitored continuously, and 0.4 mg atropine sulphate was administered if heart rate was less than 55 beats/min. Arterial blood pressure was monitored every 2 min and if systolic blood pressure was 30% less than the baseline, 10 mg aliquots of ephedrine was given. APGAR score of the baby was measured at 1 and 5 min.
Statistical analysis 
Data were fed into a computer and analysed using IBM SPSS software package version 20.0 . Qualitative data were described as number and percentage. Quantitative data were described as range (minimum and maximum), mean, SD and median. Significance of the obtained results was determined at the 5% level.
| Results|| |
In all the three groups the heart rate decreased significantly 5 min after spinal anaesthesia and thereafter when compared with the baseline measurements ([Figure 1]). With regard to heart rate values the three groups showed no significant changes. The mean arterial blood pressure decreased significantly in all groups after spinal anaesthesia and thereafter when compared with the basal values ([Figure 2]). Patients needed 0–4 ephedrine boluses with no significant differences between the three studied groups with regard to the number of ephedrine boluses ([Figure 3]). The core body temperature decreased significantly 15 min after spinal anaesthesia and thereafter in all patients of the three studied groups ([Figure 4]). However, the decrease in core body temperature was significantly more in groups II and III when compared with group I during the whole intraoperative period and 30 min postoperatively. The shivering score increased significantly 10 min after spinal anaesthesia and thereafter intraoperatively and 30 min postoperatively in all the three studied groups ([Figure 5]). The shivering score still increased significantly 60 min postoperatively in group III. The shivering scores were significantly less in group I when compared with group III at 20, 25, 30 and 45 min, intraoperatively, as well as 30 min posteroperatively with P values of 0.047, 0.001, less than 0.001, 0.001 and 0.002 respectively. Also, the shivering scores were still significantly less 30 min postoperatively, with P value of 0.002. The shivering scores were significantly less in group II 25 and 30 min intraoperatively and 30 min postoperatively when compared with group III (P values were 0.018, 0.001 and 0.018, respectively). There was a negative correlation between core body temperature and shivering score of 3 or more, with r values of −0.299, −0.405 and −0.524, respectively, for all the three groups, and P values of less than 0.001 for all ([Figure 6]). The mean core temperatures during whole period of study for shivering patients in the three studied groups were 35.95±0.06, 35.08±0.42 and 35.50±0.32°C, respectively. The mean core temperature for shivering patients in group I was significantly higher than that in groups II and III, with P values of less than 0.001 and 0.015. Also, the mean core temperature for shivering patients was significantly higher in group III when compared with group II, with P value of 0.001 ([Figure 7]). The mean APGAR scores at 1 min was 9.97±0.18 for all the three groups. The mean APGAR scores at 5 min was 10±0.0 for all the three groups. No significant changes were observed between the three groups (P=1.0) ([Figure 8]).
|Figure 1 Comparison between the three studied groups according to heart rate (beats/min).|
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|Figure 2 Comparison between the three studied groups according to mean arterial blood pressure (mmHg).|
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|Figure 3 Comparison between the three studied groups according to number of ephedrine boluses used.|
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|Figure 4 Comparison between the three studied groups according to core body temperature (°C).|
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|Figure 5 Comparison between the three studied groups according to shivering score.|
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|Figure 6 Correlations between core body temperature with shivering score during the whole period of study.|
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|Figure 7 Relation between core temperature and shivering score (≥3) during the whole period of study.|
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|Figure 8 Comparison between the three studied groups according to APGAR scores.|
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| Discussion|| |
In the present study, the mean heart rates and mean arterial blood pressures decreased significantly in all the three studied groups. The results obtained can be explained by the fact that spinal anaesthesia causes sympathetic blockade, which causes vasodilation of blood vessels of the lower half of the body leading to diminished venous return and cardiac output leading to hypotension. This decreased venous return activates the Bainbridge reflex, which leads to a decrease in heart rate . The hypotension during caesarean section is also exaggerated by the presence of gravid uterus leading to the well-known aortocaval compression syndrome . In addition, in normal pregnancy there is increased synthesis of endogenous vasodilators such as prostaglandins and nitric oxide, which creates a vasodilated state that increases the dependence on sympathetic vasoconstriction for the control of vascular tone. This explains the sudden and excessive hypotension after sympathetic blockade produced by subarachnoid blockade (SAB) in obstetric patients . The results of the present study coincide with the results of Singh et al.  and Kim et al. . There were no significant differences between the three groups as regard to ephedrine boluses. In agreement with the current results, Homas et al.  used a bolus of phenylephrine (100 mcg) or ephedrine (5 mg) for maintenance of arterial pressure during spinal anaesthesia for caesarean section. They found that the required ephedrine boluses to maintain the mean arterial blood pressure were four increments compared with phenylephrine, which were six. In addition, Wang et al.  compared three different positions and found no significant difference in the ephedrine boluses (6 mg), which was 1, 3 and 5, respectively, in the three groups. In the present study, the core body temperature decreased significantly in all the three studied groups. There are four principal reasons for hypothermia under spinal anaesthesia. First, spinal anaesthesia leads to an internal redistribution of heat from the core to the peripheral compartments. Second, with the loss of thermoregulatory vasoconstriction below the level of the spinal block, there is increased heat loss from body surfaces. Third, there is altered thermoregulation under spinal anaesthesia characterized by a 0.58°C decrease in vasoconstriction and shivering thresholds. Last, during either general or regional anaesthesia, a patient’s natural behavioural and autonomic responses to cold are unavailable or impaired, and each of general and neuroaxial anaesthesia produces high risk for inadvertent perioperative hypothermia . The core temperature was significantly higher in group I when compared with the other two groups. The significant difference was still present 30 min postoperatively. Changes in the core body temperature are mainly due to subarachnoid block, as found by keeping all other factors constant. These factors include room temperature, which was kept almost constant in all the three groups, with a mean temperature of 22°C with no significant difference. Also, parenteral fluid warming is not routinely used for caesarean section (medium surgery); however, benefits have been reported from fluid warming in the perioperative in routine obstetric practice . In agreement with the results of the present study, Hynson and Sessler  compared intraoperative warming therapies along with three warming devices. Although the results showed that the forced air-warming system was more useful in maintaining normothermia compared with circulating-water mattress and humidifier with a heated-wire breathing circuit, mild hypothermia occurred. In addition, Khan et al.  showed that there is no effect of two different doses of intrathecal pethidine (12.5 and 25 mg) on core body temperature compared with bupivacaine alone. However, the two doses of intrathecal pethidine were effective in preventing shivering. Frank et al. , who assessed the predictors of hypothermia during spinal anaesthesia, found that temperature monitoring and maintenance are essential to prevent hypothermia. The effect of spinal anaesthesia on homoeostasis of body temperature has been studied extensively. It is interesting to note that the ambient operating room temperature was not a predictor of hypothermia.
Shivering scores were significantly less in groups I and II when compared with group III. This could be explained by the fact that group I did not reach the shivering threshold, which is 35.5±0.5°C , because of the warming effect of the warming mattress, whereas group II received a prophylactic bolus of pethidine, which decreased the threshold of shivering. Pethidine has a role in reducing the shivering threshold owing to its effect on κ-opioid receptor and on α2 and β adrenoreceptor subtypes . In agreement with the results of the present study, Sessler  reported that postoperative shivering should be treated by warming of the patient, most effectively through forced air systems. In the present study, there was a negative correlation between the core body temperature and shivering score during the intraoperative period and the whole period of the study in the three studied groups. The mean temperature for shivering patients was significantly higher in patients in group I compared with groups II and III and in group III when compared with group II. There was a decrease in core body temperature with decrease in the shivering incidence for patients in group II. Díaz and Becker  found that pethidine depresses overall sympathetic outflow, which further inhibits any attempt of thermoregulation. The depressant effect on the hypothalamus results in an elevated threshold for heat response, along with a diminished threshold for cold response such as vasoconstriction and shivering. Therefore, pethidine widens the normal interthreshold range from ∼0.2°C to as much as 4°C, and patients fails adjust to cold environments and heat loss resulting from vasodilation. In agreement with the results of the present study, Alfonsi  found that the primary cause of postanaesthetic shivering is perioperative hypothermia, which sets in because of anaesthetic-induced inhibition of thermoregulation. However, shivering associated with cutaneous vasodilatation (nonthermoregulatory shivering) also occurs, one of the origins of which is postoperative pain. Also, Luggya et al.  stated that postanaesthetic shivering had a prevalence of 8.15% commonly occurred at 20 min. Hypotension and hypothermia were associated factors. They performed their study on a majority (90.74%) of emergency caesarean section patients under spinal anaesthesia. Also, Pradip et al.  recorded that shivering occurred in ∼40% of unwarmed patients who were recovering from general anaesthesia and in about 50% of patients with a core temperature of 35.5°C and in 90% of patients with a core temperature of 34.5°C. In contrast to the results of the present study, Panzer et al.  found that not all shivering-like tremor is thermoregulatory. According to their data it is possible to detect low-intensity shivering-like muscular activity during labour, and shivering-like tremor in the peripartum period is multifactorial. This may be because of the fact their group of patients were undergoing normal vaginal deliveries.
As regard to APGAR score, there were no significant differences between the three groups. A study by Hong and Lee , which agreed with the results of the present study, compared four groups. The first group served as a control, two groups received morphine in a dose of 0.1 and 0.2 mg intrathecally, and the fourth group received pethidine in dose of 10 mg intrathecally. They used these medications as antishivering agents in caesarean section using combined spinal epidural anaesthesia. Their results showed no significant differences between the four assessed groups as regard to the APGAR score.
| Conclusion|| |
Decrease in core body temperature is a serious underestimated problem during caesarean section under spinal anaesthesia. There is an effective way of prevention of shivering by decreasing the heat loss using forced air-warming blanket and decreasing the shivering threshold using intravenous pethidine (0.5 mg/kg), but with no significant difference between both methods. Moreover, the marked drop of mean arterial blood pressure was a common observation. Therefore, both the methods can be used in all patients undergoing caesarean section under spinal anaesthesia; and prophylactic use of pethidine has no deleterious effect on delivered baby.
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Conflicts of interest
There are no conflicts of interest.
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