Comparison of Butorphanol and Fentanyl for the Relief of Postoperative Shivering Associated with Spinal Anesthesia.

AIM: The aim of this study was to compare fentanyl and butorphanol for the relief of postoperative shivering in spinal anesthesia.
MATERIALS AND METHODS: A total of 100 American Society of Anesthesiologists physical status Class I and II patients aged 19-60 years belonging to both sexes who were posted for elective surgical procedures under spinal anesthesia were divided into two groups (fentanyl and butorphanol) and monitored intraoperatively for the occurrence of shivering and time taken to control shivering after administration of fentanyl and butorphanol drugs.
RESULTS: Relief of shivering is rapid and more effective with fentanyl than butorphanol. There is a significant increase in pulse rate, mean arterial pressure, respiratory rate (RR), and decreased in oxygen saturation at the onset of shivering and also a decrease in core body temperature. Sedation, nausea, vomiting, and recurrence of shivering are more with butorphanol with fentanyl.
CONCLUSION: On the basis of the study, it is concluded that fentanyl is more effective and takes less time to control perioperative shivering as compared to butorphanol.

INTRODUCTION

Hypothermia (body temperature <36°C) occurs postoperatively in 26–90% of all patients who underwent elective surgery.[1]

Perioperative shivering is a common experience for the patients undergoing regional anesthesia. The incidence is estimated to be around 60%. The risk is high in geriatric patients (age >60 years), patients with poor nutritional status and with preexisting diseases such as diabetes mellitus that impairs thermoregulation.

The impairment of autonomic thermoregulatory control while the patient is under anesthesia, cold environment of the theater, and cold intravenous fluids may contribute to fall in body temperature and hence shivering.

It is not only unpleasant to the patient but also physiologically results in increased oxygen consumption by up to 300%, an increase in intraocular pressure and other sympathetic over activity.

In humans, core temperature is normally maintained within narrow limits of 36.5–37.5°C[2] even in the presence of severe environmental variations, by a combination of physiological and behavioral responses.

The autonomic nervous system maintains normothermia in homeothermic mammals as even minor deviations from normal core body temperature cellular, and tissue damage will occur.[234]

If hypothermia could not be properly anticipated and treated many complications such as impaired wound healing, increased bleeding from the surgical site, and morbid cardiac events[567891011121314151617] may occur.

Many workers have tried to overcome this ill effect using various pharmacological agents. Several drugs such as pethidine, doxapram, clonidine, ketamine, tramadol, physostigmine have been studied for the treatment of shivering. Of this pethidine is extensively evaluated and is the drug of choice for the treatment of shivering in postanesthetic period.

Fentanyl due to its sedative action on brain decreases shivering while butorphanol exerts its effect through κ and µ receptor agonistic modulation.

This study was designed to evaluate the efficacy of fentanyl and butorphanol for control of shivering.

MATERIALS AND METHODS

A prospective randomized study was conducted over 18 months period (2014–2016) to compare the effect of fentanyl and butorphanol in controlling postoperative shivering associated with spinal anesthesia.

After obtaining the consent of the hospital ethics committee, informed and written consent of patients was obtained.

A total of 100 American Society of Anesthesiologists physical status Class I and II patients aged 19–60 years belonging to both sexes who were posted for elective surgical procedures under spinal anesthesia were taken up for the study.

Exclusion criteria – patients with comorbid conditions, high-grade fever, pregnancy, and patients who developed hypotension and bradycardia after giving spinal anesthesia were excluded from the study.

Group A included fifty patients who received fentanyl 1.7 µg/kg at the onset of shivering. Group B included fifty patients who received butorphanol 20 µg/kg at the onset of shivering.

All the study drugs were prepared in identical syringes and in the equal volume (1 ml). All the patients were preloaded with 20 ml/kg of lukewarm crystalloid administered after obtaining intravenous access.

The temperature in the operation theater was maintained at 27°C.

In the operation theater, monitors (nasopharyngeal temperature probe, pulse oximeter, electrocardiogram, and noninvasive blood pressure) were attached and baseline temperature, pulse rate (PR), RR, mean arterial pressure (MAP), and oxygen saturation (SPO2) were recorded.

All the patients were given spinal anesthesia and were monitored intraoperatively for the occurrence of shivering. Core body temperature at the time of shivering was measured.

Once the shivering was observed either fentanyl or butorphanol was administered to control shivering as per group allocation. The patients were closely observed for the control of shivering. The time taken to control shivering was recorded.

All the patients were observed for nay relapse of shivering which was treated with the repeat dose of either fentanyl 1.7 µg/kg in Group A or with butorphanol 20 µg/kg in Group B.

Shivering and sedation were assessed according to gradation shown below. Sedation was assessed after 10 min of treatment.

Grades of shivering

Grade 0. No shivering:

Piloerection but no visible shivering

Muscular activity in only one muscle group

Muscular activity in more than one muscle group but not generalized

Shivering involving whole body.

Grades of sedation

Grade 0 - Alert:

Arouse to voice

Arouse with gentle tactile stimulation

Arouse with vigorous tactile stimulation

No awareness.

OBSERVATION AND RESULTS

Demographic profiles and vital parameters were expressed as mean ± standard deviation mean results were compared using ANOVA test. Changes in core temperature were compared between A and B groups using ANOVA test. A t-test was used for qualitative assessment of sedation and side effects. P < 0.05 was considered statistically significant [Table 1]. The mean age in fentanyl group was 39.74 and butorphanol was 37.2 years. The distribution of age, sex in the two groups was almost similar.

Table 1

Demographic profile

There was a significant change of core body temperature at the time of shivering in both groups [P < 0.05, Table 2].

Table 2

Core body temperature changes

Shivering was controlled in 96% (48) of patients in Group – A within 2 min and in 40% (20) of patients in Group B within 2 min of administration of the drug. It was also observed that in 60% (30) of the Group – B patients it was relieved in 2–5 min (P < 0.05). Thus, there is statistically significant difference in controlling shivering between the two groups [Table 3].

Table 3

Time taken to stop shivering

The PR in fentanyl group increased at the onset of shivering to 102.3 ± 13 from the basal PR of 86.8 ± 9.7. The PR gradually decreased at 15 min to 95.0 ± 11.3. The PR in butorphanol group increased at the onset of shivering to 101.2 ± 16.6 from the basal PR of 85.0 ± 8.5. The PR gradually decreased at 15 min to 94.1 ± 8.4.

The MAP in fentanyl group increased at the onset of shivering to 9.6 ± 9.1 from the basal MAP of 90.7 ± 11.5. The MAP gradually decreased at 15 min to 90.7 ± 7.7. The MAP in butorphanol group increased at the onset of shivering to 101.1 ± 9.3 from the basal MAP of 90.7 ± 11.8. The MAP gradually decreased at 15 min to 90.3 ± 9.2.

The RR in fentanyl group increased at the onset of shivering to 18.1 ± 3.5 from the basal RR of 15.0 ± 2.5. The RR decreased at 15 min to 14.7 ± 2.7. The RR in the butorphanol group increased at the onset of shivering to 17.0 ± 3.6 from the basal RR of 14.2 ± 2.5. The RR decreased at 15 min to 14.0 ± 2.4.

The SPO2 in the fentanyl group decreased significantly at the onset of shivering to 97.2 ± 1.2 from the basal SPO2 of 98.7 ± 0.8, and it remained low at 15 min of 97.6 ± 1.3 compared to basal SPO2. The SPO2 in the butorphanol group decreased significantly from the basal SPO2 of 99.0 ± 0.8–96.9 ± 1.4 at the onset of shivering. The SPO2 decreased at 15 min to 96.7 ± 1.5 [Table 4].

Table 4

Change of vital parameters before and after treatment of shivering (mean±SD)

*Shivering reappeared in more patients treated with B (14%) compared to F (6%) [P < 0.05, Table 5].

Table 5

Reappearance of shivering

Four patients (8%) in group A had sedation Grade I while 46 patients (92%) in Group A has Grade II sedation. Two patients (4%) in A-B have Grade II sedation while Grade III sedation was there in 48 patients (96%) of Group B patients (P < 0.05). Thus, patients in Group B had statistically significant sedation than patients of Group A [Table 6].

Table 6

Sedation score

Five patients of Group A and five patients of Group B had nauseas while vomiting was observed in two patients of Group A and seven patients of Group B.

DISCUSSION

Body temperature is controlled by a negative feedback system in the hypothalamus which integrates information from the whole body. Approximately, 80% of this thermal input is derived from core body temperature. The hypothalamus coordinates increase in heat production as well as increase or decrease in heat loss as needed to maintain normothermia.

Hypothermia during spinal anesthesia is the most common perioperative thermal disturbance.[18] Perioperative hypothermia is due to anesthetic impaired thermoregulation and exposure to a cold operating theater environment. After an initial rapid fall in core temperature, there occurs a slow and linear reduction in temperature. Finally, core temperature stabilizes and virtually remains unchanged.

On emergency from anesthesia, normal thresholds are restored. Hence, hypothermic patients may shiver which causes considerable metabolic changes.

Shivering during a regional anesthetic may be averted by maintaining high ambient temperature[19] warming skin surface with radiant heat[20] or using drugs.

Many drugs such as pethidine, other opioids (fentanyl, sufentanil, alfentanil, buprenorphine), doxapram, methylphenidate, clonidine, and ketanserin are known to be effective in suppressing shivering.[2122]

In our study, we found that 96% of patients stopped shivering within 2 min, and 4% of patients stopped within 2–5 min after treatment with fentanyl and 40% of patients stopped shivering within 2 min, and 60% stopped shivering within 2–5 min after treatment with butorphanol.

In our study, three patients, who received fentanyl, have reappearance of shivering within 30 min of treatment. The relapse was treated with the same dose of Fentanyl. Seven patients who received butorphanol for the control of shivering had relapse within 20–45 min and required an additional same dosage of the drug.

There were significant variations between basal core body temperature and the core body temperature at the onset of shivering in both the groups.

In fentanyl group, 46 patients had Grade II sedation and in butorphanol group 48 patients had Grade III sedation and required supplemental oxygen therapy. This showed that sedation is more with butorphanol than with fentanyl. In our study, we observed that postoperative nausea which can be more disturbing to the patient is less with fentanyl group.

CONCLUSION

On the basis of this study, it is concluded that fentanyl in more effective and takes less time to control perioperative shivering as compared to butorphanol which also causes more sedation and nausea and vomiting as compared to fentanyl.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.