|Year : 2019 | Volume
| Issue : 2 | Page : 77-80
Effects of 0.5% heavy bupivacaine at room versus body temperature on shivering and analgesia after spinal anesthesia in patients undergoing cesarean section
Khoula Mohammed Saif Al-Mandhari1, Amal Ali Mubarak Al-Shukaili1, Basman Younis2, Shobha Lad2, Rashid M Khan2, Naresh Kaul2
1 Oman Medical Specialty Board, Muscat, Sultanate of Oman
2 Department of Anesthesia, Pain and ICU, Khoula Hospital, Muscat, Sultanate of Oman
|Date of Submission||01-Jun-2019|
|Date of Decision||14-Jun-2019|
|Date of Acceptance||16-Jun-2019|
|Date of Web Publication||7-Aug-2019|
Dr. Naresh Kaul
Department of Anesthesia, Pain and ICU, Khoula Hospital, Muscat
Sultanate of Oman
Source of Support: None, Conflict of Interest: None
Background: Shivering is an undesirable, unpleasant experience after spinal anesthesia. Injecting cold bupivacaine has been incriminated as a contributory factor. Aims and Objective: In this prospective study we evaluated the efficacy of warming the heavy bupivacaine to body temperature for prevention of shivering and if it influences analgesic quality of spinal anesthesia. Materials and Methods: In this double blind, randomized controlled study, 100 patients aged 20-35 years of American Society of Anesthesiologist physical status I and II undergoing elective or emergency Caesarean sections were included and allocated to either Room temperature group (RT Group, n= 50), or Body temperature group (BT group, n = 50). A standard spinal anesthetic of 2ml of 0.5 % heavy bupivacaine plus 20 microgram of fentanyl was administered using 25G pencil point spinal needle in the sitting position. Besides the incidence and intensity of shivering and effect on intraoperative analgesia, effect on hemodynamics, nausea, vomiting, blood loss, pruritis and Apgar scores were recorded. Data was analyzed using SPSS (The Statistical Package for Social Sciences) version 22.0 software (International Business Machines Corporation, Armonk, New York, USA). P < 0.05 was considered significant. Results: The patients were comparable in terms of demographic variables. Shivering was present in 31 (62%) and 7 (14%) patients respectively in RT and BT Groups, which was statistically significant (P = 0.0001). Intensity of shivering ≥3 was observed in 15 (30%) patients of RT group and 5 (10%) patient in BT group. We did not note any difference in the analgesic status intraoperatively nor any difference in the duration of analgesia. Surprisingly, the incidence of pruritis was significantly reduced in the BT group as compared to RT group (P = 0.037). Conclusions: Warming the heavy bupivacaine to body temperature is effective in preventing shivering and reducing pruritis secondary to spinal anesthesia without affecting analgesia.
Keywords: Cesarean section, shivering, spinal
|How to cite this article:|
Al-Mandhari KM, Al-Shukaili AA, Younis B, Lad S, Khan RM, Kaul N. Effects of 0.5% heavy bupivacaine at room versus body temperature on shivering and analgesia after spinal anesthesia in patients undergoing cesarean section. Indian J Pain 2019;33:77-80
|How to cite this URL:|
Al-Mandhari KM, Al-Shukaili AA, Younis B, Lad S, Khan RM, Kaul N. Effects of 0.5% heavy bupivacaine at room versus body temperature on shivering and analgesia after spinal anesthesia in patients undergoing cesarean section. Indian J Pain [serial online] 2019 [cited 2019 Aug 17];33:77-80. Available from: http://www.indianjpain.org/text.asp?2019/33/2/77/264080
| Introduction|| |
Shivering is a common unwanted effect associated with central neuroaxial block with a median incidence of 33%. Reduced body temperature (BT), release of endogenous pyrogens, and direct effect of local anesthetic temperature on the thermosensitive neurons in the spinal cord have been proposed as some of the causative factors responsible for postspinal anesthesia shivering. Exact etiology is still not proven, with no definitive treatment for shivering.
Najafianaraki et al. have shown that the temperature of the injected local anesthetic could be contributory to postspinal shivering. They demonstrated that bupivacaine administered at room temperature (RT) was associated with significantly lower incidence of shivering as compared to that administered at 4°C.
In this prospective, randomized, double-blind study, we evaluated the effect of warm (BT 37°C) versus cold (RT 22°C–23°C) 0.5% heavy bupivacaine injected intrathecally, on postspinal anesthesia shivering and duration of analgesia in patients undergoing cesarean section.
| Materials and Methods|| |
This double-blind study was initiated after obtaining approval from the Ethical Issues Committee. Sample size of 100 was arrived to achieve a statistical power of 80%–95% confidence interval according to Fleiss et al. with correction continuity method. All patients belonged to the American Society of Anesthesiologist I and II category between the age range of 20 and 35 years, and all underwent elective/emergency lower segment cesarean section (LSCS). Patients were randomly divided into two groups as per closed envelop technique:
- BTGroup (n = 50): received 2 ml of 0.5% heavy bupivacaine + 20 mcg fentanyl intrathecally at 37.5°C
- RT Group (n = 50): received 2 ml of 0.5% heavy bupivacaine + 20 mcg fentanyl intrathecally at 22°C –23°C.
Warming of medications was done immediately before the procedure using tissue kit warmer machine (Fbrinotherm Baxter AG, Vienna). This machine is generally used for warming fibrin glue to 37.5°C during neurosurgery. We employed this machine for warming bupivacaine/fentanyl in the BT group.
All patients received uniform premedication in the form of single-dose ranitidine (50 mg) and metoclopramide (10 mg) 30–45 min prior to cesarean section. The theater temperature was kept constant between 22 and 23°C. After instituting routine monitoring, preloading was done with 500 ml of warmed Ringer's lactate fluid. Subarachnoid block was performed at L3-4/L4-5 space in the sitting position, using a 25G pencil-point spinal needle, with a midline approach by a well-experienced anesthesiologist. Heavy 0.5% bupivacaine (2 ml) plus 20 μg fentanyl was administered after obtaining clear CSF.
The calculated dose of bupivacaine and fentanyl for BT group was withdrawn from warmed ampoule immediately after getting the cerebrospinal fluid (CSF) from the spinal needle and an empty syringe that had been kept in the baby incubator at 37°C. This was done to reduce the lag time changes and effect of ambient temperature on our warmed solution. On the contrary, for RT group, the syringe along with bupivacaine and fentanyl were kept at RT (22°C –23°C).
Patient temperature was monitored by a probe over the tympanic membrane as an indicator of core BT.
As per the study protocol, if at any intraoperative stage patient complained of pain, either 50% nitrous oxide in oxygen via face mask or ketamine 0.5 mg/kg intravenously was to be administered. If this failed to satisfy the patient, general anesthesia would be administered.
Parameters recorded during the study included: sensory block level by needle prick, blood pressure, heart rate, core temperature, and shivering with intensity (Grade 1–4), [Table 1]. Duration of analgesia ( first analgesic requirement postoperatively) and any need for intraoperative supplemental analgesic were also recorded. Other than sensory block level and duration of analgesia, all other parameters were recorded every 5 min for the first 20 min, then every 10 min up to 30 min, and finally, every 15 min up to 60 min. Shivering was evaluated according to the shivering scale more specific to neuraxial anesthesia developed by Crossley and Mahajan. Some other side effects that were recorded included nausea/vomiting, Apgar score, and blood loss.
The maximal intensity of shivering and incidence of nausea, vomiting, and pruritus were compared using Chi-square test. P < 0.05 was considered as statistically significant.
| Results|| |
The demographic data of the patients were nearly identical in the two groups [Table 2].
There were no differences between the two groups, in the amount of blood loss, heart rate, blood pressure, and Apgar score.
Out of 50 patients in each group, shivering was observed in 7 (14%) and 31 (62%) patients in the BT and RT group, respectively [Table 3]. Intensity of shivering ≥3 was observed in 15 (30%) patients of RT group and 5 (10%) patient in BT group [Diagram 1]. Core temperature was 1° less in RT group as compared to BT group.
|Table 3: Incidence of shivering, pruritus, nausea, and vomiting in the two groups|
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As seen in [Table 4], none of the 100 patients needed any analgesic supplement intraoperatively. The duration of analgesia was nearly identical in both the groups (P = 0.45). The median sensory block level was one dermatome less in the BT group as compared to the RT group.
|Table 4: Dermatomal level of sensory block, duration of analgesia, and need for analgesic supplementation|
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Incidence of pruritus was significantly higher in the RT group as compared to BT group with P < 0.05. The incidence of nausea and vomiting was also higher in the RT group, though this difference was statistically insignificant.
| Discussion|| |
Administering intrathecal heavy bupivacaine 0.5% at RT 22°C–23°C have been associated with a significant reduction in the incidence and intensity of postspinal shivering when compared with that given at 4°C. In contrast, we investigated the effects of administration of local anesthetic at BT versus RT when injected into the subarachnoid space in patients who underwent LSCS. We noted a significantly reduced incidence of shivering in patients injected with bupivacaine and fentanyl at BT as compared to patients injected with similar drugs and volume at RT without altering the analgesic potency of the injected drugs.
The thermoregulatory control system of human beings coordinates the defense mechanism against wide environmental temperature changes in order to maintain our BT within narrow limits, thus optimizing the conditions for ideal metabolic functions.
Intraoperative hypothermia is associated with deleterious outcomes. Shivering is one way, in which our body tries to overcome the decrease in the temperature, but the metabolic and hemodynamic effects of shivering that include the increase in cardiac work, oxygen consumption, and carbon dioxide production might be critical in decompensated patients. Shivering also may interfere with surgical environment and accuracy of monitoring system due to involuntary body movements.
Postanesthesia shivering is very uncomfortable for the patient and might affect their satisfaction and decision for regional blocks when they come for subsequent surgeries in the future, especially for repeated LSCS.
Some possible mechanisms that have been postulated for spinal anesthesia-related lowering of BT include: first, spinal anesthesia impairs significantly the thermoregulatory system by blocking the tonic vasoconstriction that is essential for temperature regulation. Second, the central neural blockade causes redistribution of core heat from the trunk (below the block level) to peripheral tissues. These two effects might predispose the patient to hypothermia and the resultant shivering.
The spinal cord thermosensitivity has been studied throughin vivo experiments by local changes of temperature of the spinal cord, which produce heat gain and loss mechanisms such as shivering and vasomotions. On the other hand,in vitro experiments in animals have confirmed the presence of “intrinsically thermosensitive neurons” within the spinal cord.,
The effect of temperature on baricity of local anesthetic solutions was studied using the Oxford glass spine model that was developed by the Nuffield Department of Anesthetics in Oxford. There was an obvious difference in distribution of local anesthetic when there was a difference in the temperatures between the CSF and injectate. When bupivacaine was warmed to 37°C, the spread of injectate was slower, as it became close to BT and did not extend as far cephalad when compared with bupivacaine at RT.
Most spinal anesthetic solutions are administered at RT (20°C–24°C). The local anesthetic solutions administered at RT equilibrate with BT within 2 min, until thermal equilibration is achieved, the solution will be slightly hyperbaric, in which the position of the patient will affect the distribution and the level of the block. This is consistent with clinical data that showed that warming bupivacaine prior to injection has an effect on the sensory level achieved and the variability of the block.
In the present study, warming the local anesthetic agent to BT could have resulted in slower and limited cephalic movement of bupivacaine compared with bupivacaine at RT. This could explain the smaller dermatomal sensory block with resultant less vasodilatation and subsequent heat loss leading to lesser heat loss and shivering. However, this difference in sensory block level of one dermatome is of little clinical significance.
An interesting finding of our study was the observation that itching was significantly less in BT group as compared to RT group. This finding requires further investigations with a larger sample size to be authoritatively conclusive. We could not find any explanation for this finding and it needs further research.
Finally, we recommend using a Baxter machine for warming the medications. However, this machine may not be available in all theaters and hence we would suggest clinicians to use baby incubator kept at 37°C as an alternative warming method since this is usually available in obstetric theaters at the time of LSCS.
| Conclusion|| |
Warming hyperbaric bupivacaine to BT can reduce the incidence and intensity of shivering in women undergoing cesarean delivery under spinal anesthesia as compared to that administered at RT without influencing the quality of analgesia.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]