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Canadian Journal of Anesthesia 48:854-858 (2001)
© Canadian Anesthesiologists' Society, 2001
General Anesthesia

IM droperidol as premedication attenuates intraoperative hypothermia

[L'administration im d'une prémédication de dropéridol atténue l'hypothermie peropératoire]

Kousaku Toyota, Md*, Shinichi Sakura, Md*, Yoji Saito, Md*, Akemi Shido, Md* and Takashi Matsukawa, Md{dagger}

* From the Department of Anesthesiology, Shimane Medical University, Izumo City, and the
{dagger} Department of Anesthesiology,Yamanashi Medical University, Yamanashi, Japan.

Address correspondence to: Dr. Shinichi Sakura, Associate Professor, Department of Anesthesiology, Shimane Medical University, 89-1 Enya-cho, Izumo City, 693-8501 Japan. Phone: 81-853-20-2295; Fax: 81-853-20-2292; E-mail; ssakura{at}shimane-med.ac.jp


   Abstract
TOP
 Abstract
Introduction
 Patients and methods
 Results
 Discussion
 References
 
Purpose: Perioperative hypothermia results largely from core-to-peripheral heat redistribution. Droperidol, which is often used for premedication, promotes vasodilation, and thus may affect redistribution of heat. Accordingly, we tested the hypothesis that preanesthetic droperidol would affect perioperative hypothermia.

Methods: Twenty-three ASA physical status I patients scheduled for arthroscopic ligament reconstruction were randomly assigned to two groups to receive no premedication or im droperidol 0.1 mg•kg–1 30 min before anesthesia. Anesthesia was induced and maintained with propofol and fentanyl. We monitored core (tympanic) and peripheral (palm) temperatures, and skin (fingertip) blood flow for two hours after the induction of anesthesia during surgery.

Results: Before the induction of anesthesia, patients given droperidol were more deeply sedated than those given no premedication. Core temperature, which was similar in both groups before induction, decreased significantly more in the control than in the droperidol patients (0.75 ± 0.34°C and 0.37 ± 0.20°C, respectively, at 75 min after induction; P <0.01). Preinduction peripheral temperature and skin blood flow were lower in the control group than in the droperidol group, but the two variables became similar in both groups after induction.

Conclusion: The results of the present study confirm our hypothesis that premedication with droperidol affects perioperative hypothermia. Droperidol may prevent core-to-peripheral heat redistribution after the induction of anesthesia.


   Introduction
TOP
 Abstract
 Introduction
Patients and methods
 Results
 Discussion
 References
 
HYPOTHERMIA is common during anesthesia and surgery and has been shown to be associated with adverse clinical outcomes including postoperative shivering,1 increased blood loss,2 decreased drug metabolism and clearance,3 postoperative myocardial ischemia,4 wound infection,5 and delayed postanesthetic recovery.6 Available data indicate that much of this hypothermia results largely from an internal core-to-peripheral redistribution of body heat.7 Thus, it is important to know the effect of perioperative medication and procedures on this redistribution.

Droperidol is a commonly used sedative and often used for premedication before anesthesia.8 In addition, it decreases {alpha}-adrenergic tone producing vasodilation, and, thus, may affect the redistribution of heat. Although the effect of droperidol on thermoregulatory responses was investigated in combination with fentanyl in animals,9 no clinical data is available concerning the effects of its use for premedication on core and peripheral temperatures. Accordingly, we tested the hypothesis that preanesthetic droperidol would affect perioperative hypothermia.


   Patients and methods
TOP
 Abstract
 Introduction
 Patients and methods
Results
 Discussion
 References
 
After Institutional Review Board approval and written informed consent, we studied 23 ASA physical status I patients scheduled for arthroscopic ligament reconstruction lasting more than two hours. Obese patients, patients with thyroid disease, dysautonomia, or Raynaud's syndrome, and those taking vasodilating drugs were excluded.

Patients were randomly assigned to one of two groups to receive no premedication (Group C) or intramuscular droperidol 0.1 mg•kg–1 on the ward 30 min before entering the operating room (Group D). The temperature in the ward and the operating room was adjusted to 24–25°C. After an iv infusion of acetated Ringer's solution was initiated in the left hand at a rate of 10 mL•kg–1•hr–1, anesthesia was induced with 1.5 mg•kg–1 propofol and 23 µg•kg–1 fentanyl. Tracheal intubation was facilitated with 1.5 ~ 2.0 mg•kg–1 vecuronium. Anesthesia was maintained with 6 ~ 8 mg•kg–1•hr–1 propofol and 2 ~ 5 µg•kg–1•hr–1 fentanyl. Ventilation was adjusted to maintain the end-tidal PCO2 near 35 mmHg. The fresh gas flow of oxygen 1 L•min–1 and air 5 L•min–1 was administered via a semiclosed circle system without airway heating or humidification. The patients were only covered with a single surgical drape of synthetic cloth, and no active warming system was used during the study.

The level of sedation was assessed before the induction of anesthesia using a sedation score of 1–4, where 1=asleep, 2=drowsy, 3=calm, and 4=alert. Ambient temperature was measured at the level of the patient, well away from any heat-producing equipment before the induction of anesthesia. Core and peripheral temperatures were monitored for two hours after the induction of anesthesia. Core temperature was measured at the tympanic membrane. The aural probe (Tympanic Temperature Sensor, Respiratory Support Products, CA, USA) was inserted, and the external ear was covered with a cotton pad. Peripheral temperature was measured at the palm that was kept open with the shoulder abducted. The skin surface thermometer probe (Skin Temperature Sensor, Respiratory Support Products, CA, USA) was placed on the right palm and covered with cotton. Peripheral blood flow was measured at the palmar side of the right index finger, to which a plate-type probe of a laser Doppler flowmeter (ALF 2100, Advance, Tokyo, Japan) was attached. Recording of core and peripheral temperatures and blood flow was started at least 15 min after the placement of the probes and conducted every 15 min during the two hours of the study.

Heart rate, blood pressure, and arterial oxygen saturation were monitored thoughout the study period using three lead electrocardiography, sphygmomanometer, and pulse oxymetry, respectively, and recorded every five minutes. The sphygmomanometer and the pulse oxymeter were placed on the right arm and the left fingertip, respectively.

Sample size was determined by power analysis of ANOVA based on the variability observed in our pilot study and the ability to detect a difference in the decrease in core temperature of 0.3 with beta set at 0.2 and alpha set at 0.05. Results are expressed as mean ± SD unless otherwise stated. Morphometric and anesthetic data in both groups were compared using Student's t test and {chi}2 test, as appropriate. Continuous variables including temperatures, peripheral blood flow, heart rate, blood pressure, and arterial oxygen saturation were analyzed using repeated measures ANOVA, and Dunnet test or Student's t test for post hoc testing. The Mann-Whitney U test was used to determine a difference in the sedation level. P <0.05 was considered statistically significant.


   Results
TOP
 Abstract
 Introduction
 Patients and methods
 Results
Discussion
 References
 
Of 23 patients enrolled in the study, 13 patients received no premedication (Group C) and ten droperidol (Group D). The two groups did not differ in morphometric and anesthetic data, including the dose of fentanyl and volume of fluid administered for the study period of two hours (TableGo).


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  		TABLE Morphometric and anesthetic data
 
Patients in Group D were more deeply sedated than those in Group C before the induction of anesthesia (Figure 1Go). Preinduction core (tympanic) temperature was comparable in the two groups before induction: 36.30 ± 0.26°C and 36.14 ± 0.22°C in Groups C and D, respectively. In contrast, peripheral temperature and peripheral blood flow were significantly lower in Group C than in Group D before induction (Figures 2 and 3GoGo).



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  		FIGURE 1 The number of patients in each sedation score in the two groups. *Significantly different between groups.

 


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  		FIGURE 2 Time course of peripheral (palm) temperature. While preinduction (Pre) temperature was significantly higher in patients given droperidol than in the others, both groups of patients showed similar course after the induction (Ind) of general anesthesia. *Significantly different from control group.

 


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  		FIGURE 3 Time course of skin (index fingertip) blood flow. While preinduction (Pre) blood flow was significantly greater in patients given droperidol than in the others, both groups of patients showed similar course after the induction (Ind) of general anesthesia. *Significantly different from control group.

 
After the induction of anesthesia, core temperature decreased significantly in both groups, but the decrease in core temperature in group D was significantly smaller than that in group C. (Figure 4Go). In contrast, time courses of peripheral temperature and peripheral blood flow fluctuations were similar in the two groups during surgery.



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  		FIGURE 4 Time course of change in core (tympanic membrane) temperature ({Delta}T tym). The two groups of patients developed a significant decrease after induction (Ind), but the {Delta}T tym was greater in patients without premedication than those given droperidol. *Significantly different from control group.

 
The heart rate, blood pressure, and pulse oximetry data were similar in the two groups throughout the study period and did not change significantly except immediately after the administration of propofol.


   Discussion
TOP
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
References
 
The results of the present study showed that premedication with droperidol reduced intraoperative redistribution hypothermia. Patients given droperidol developed hypothermia after the induction of anesthesia, but the decrease in core temperature was smaller than that in patients who received no premedication. Since the use of droperidol did not affect peripheral temperature during surgery, it seems that core-to-peripheral heat redistribution after induction was smaller in patients who received droperidol than in those who did not.

The effects of droperidol on thermoregulatory mechanisms have been examined while being used in combination with fentanyl in rats. According to the results of a study by Wixson et al.,9 the combination caused a decrease in rectal temperature but the depression of thermoregulation was minimal as compared with pentobaribitone, ketamin-xylazine and ketamine-diazepam. However, no study has focused on the effects of droperidol alone.

In addition to volatile10 and iv anesthetics including propofol,11 a variety of anesthetic adjuvants12,13 have been shown to impair thermoregulatory responses in humans. However, the effects of preanesthetic sedatives on perioperative hypothermia have not been adequately investigated. Recently, Bernard et al.14 showed that oral clonidine as premedication did not impair redistribution hypothermia in patients during orthopedic surgery performed under general anesthesia. Clonidine, an {alpha}2 adrenoceptor agonist, reduces sympathetic tone but produces peripheral vasoconstriction related to {alpha}2 adrenergic stimulation.15

Droperidol has potent sedative and alpha blocking properties, and thus may produce cutaneous vasodilation more than clonidine does. In this study, patients given droperidol developed higher peripheral blood flows and peripheral temperatures before the induction of general anesthesia. In contrast, preanesthetic droperidol did not alter preinduction core temperature. Thus, it is highly likely that, in a patient given droperidol, the initial small core-to-peripheral temperature gradient minimized subsequent redistribution hypothermia after general anesthesia was induced.

Similar findings have been observed in patients given vasodilators before surgery. In a study by Vassilieff et al.,16 patients undergoing hip arthroplasty who received nifedipine, a calcium-channel blocker, both the night before and the morning of surgery developed less intraoperative hypothermia than those who did not receive the vasodilator. Morioka et al.17 minimized redistribution hypothermia by applying transdermal nitroglycerin before gastrointestinal surgery.

It should be noted that a vasodilating effect might further aggravate redistribution hypothermia depending on the time of administration. Vasodilatation that occurs well before induction of anesthesia can reduce the core-to-peripheral tissue temperature gradient and minimize subsequent redistibution during surgery. However, when given only immediately before induction, nifedipine lowered core temperature more profoundly.16

It may be surprising that preanesthetic droperidol did not alter preinduction core temperature in the present study, in view of a recent study by Matsukawa et al.18 showing that im midazolam, which is also often used for premedication, induced a concentration (dose) dependent decrease in core temperature. The authors suspected that midazolam-induced vasodilatation allowed redistribution of heat from the core thermal compartment to peripheral tissues. According to their study, midazolam 0.075 mg•kg–1 decreased core temperature 0.6 ± 0.1°C for 30 min. However, their subjects (young healthy volunteers) were kept in a room at a temperature of about 22°C, whereas ours (patients) were kept in a ward at a temperature of 24–25°C. The core-to-peripheral temperature gradient before premedication was smaller in our patients than in their subjects.

Limitations to this study include the effects of ambient temperature. Since the patients' environment was based on institutional and Japanese standards, the ambient temperature measured in the present study was higher than that of most previous studies.19–21 Higher ambient temperatures would keep peripheral temperatures higher. In fact, peripheral temperature measured at the palm in patients given droperidol before the induction of anesthesia was 35.77 ± 0.56°C and the initial core-to-peripheral gradient was only 0.37 ± 0.49°C. In a colder environment, thus, the results might have been different.

In conclusion, the results of the present study confirm our hypothesis that premedication with droperidol affects perioperative hypothermia. Droperidol can provide adequate sedation and vasodilatation, may decrease core-to-peripheral heat redistribution, and minimize hypothermia after the induction of anesthesia.

Revision received June 4, 2001. Accepted for publication April 11, 2001.


   References
TOP
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
1 Frank SM, Fleisher LA, Olson KF, et al. Multivariate determinants of early postoperative oxygen consumption in elderly patients. Effects of shivering, body temperature, and gender. Anesthesiology 1995; 83: 241–9.[Medline]

2 Bock M, Müller J, Bach A, Böhrer H, Martin E, Motsch J. Effects of preinduction and intraoperative warming during major laparotomy. Br J Anaesth 1998; 80: 159–63.[Abstract/Free Full Text]

3 Heier T, Caldwell JE, Sessler DI, Miller RD. Mild intraoperative hypothermia increases duration of action and spontaneous recovery of vecuronium blockade during nitrous oxide-isoflurane anesthesia in humans. Anesthesiology 1991; 74: 815–9.[Medline]

4 Frank SM, Fleisher LA, Breslow MJ, et al. Perioperative maintenance of normothermia reduces the incidence of morbid cardiac events. A randomized clinical trial. JAMA 1997; 277: 1127–34.[Abstract]

5 Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalization. N Engl J Med 1996; 334: 1209–15.[Abstract/Free Full Text]

6 Lenhardt R, Marker E, Goll V, et al. Mild intraoperative hypothermia prolongs postanesthetic recovery. Anesthesiology 1997; 87: 1318–23.[Medline]

7 Matsukawa T, Sessler DI, Sessler AM, et al. Heat flow and distribution during induction of general anesthesia. Anesthesiology 1995; 82: 662–73.[Medline]

8 Tobias MD, Zuckerman LA. Premedication: drugs to start, continue, or withhold. In: Longnecker DE, Murphy FL (Eds.). Introduction to Anesthesia, 9th ed., Philadelphia: W. B. Saunders Company, 1997: 27–35.

9 Wixson SK, White WJ, Hughes HC Jr, Lang CM, Marshall WK. The effects of pentobarbital, fentanyl-droperidol, ketamine-xylazine and ketamine-diazepam on core and surface body temperature regulation in adult male rats. Lab Anim Sci 1987; 37: 743–9.[Medline]

10 Støen R, Sessler DI. The thermoregulatory threshold is inversely proportional to isoflurane concentration. Anesthesiology 1990; 72: 822–7.[Medline]

11 Leslie K, Sessler DI, Bjorksten AR, et al. Propofol causes a dose-dependent decrease in the thermoregulatory threshold for vasoconstriction but has little effect on sweating. Anesthesiology 1994; 81: 353–60.[Medline]

12 Kurz A, Sessler DI, Annadata R, Dechert T, Christensen R, Bjorksten AR. Midazolam minimally impairs thermoregulatory control. Anesth Analg 1995; 81: 393–8.[Abstract]

13 Kurz A, Go JC, Sessler DI, Kaerk K, Larson MD, Bjorksten AR. Alfentanil slightly increases the sweating threshold and markedly reduces the vasoconstriction and shivering thresholds. Anesthesiology 1995; 83: 293–9.[Medline]

14 Bernard JM, Fulgencio JP, Delaunay L, Bonnet F. Clonidine does not impair redistribution hypothermia after the induction of anesthesia. Anesth Analg 1998; 87: 168–72.[Abstract/Free Full Text]

15 Khan ZP, Ferguson CN, Jones RM. Alpha-2 and imidazoline receptor agonists. Anaesthesia 1999; 54: 146–65.[Medline]

16 Vassilieff N, Rosencher N, Sessler DI, Conseiller C, Lienhart A. Nifedipine and intraoperative core body temperature in humans. Anesthesiology 1994; 80: 123–8.[Medline]

17 Morioka N, Ozaki M, Matsukawa T, Suzuki H. Transdermal nitroglycerine before induction of anesthesia prevents redistribution hypothermia in patients under general anesthesia. Masui (Jpn J Anesthesiol) 1998; 47: 1459–63.

18 Matsukawa T, Hanagata K, Ozaki M, Iwashita H, Koshimizu M, Kumazawa T. I.m. midazolam as premedication produces a concentration-dependent decrease in core temperature in male volunteers. Br J Anaesth 1997; 78: 396–9.[Abstract/Free Full Text]

19 Sessler DI, Olofsson CI, Rubinstein EH. The thermoregulatory threshold in humans during nitrous oxide-fentanyl anesthesia. Anesthesiology 1988; 69: 357–64.[Medline]

20 Hynson JM, Sessler DI, Belani K, et al. Thermoregulatory vasoconstriction during propofol/nitrous oxide anesthesia in humans: threshold and oxyhemoglobin saturation. Anesth Analg 1992; 75: 947–52.[Abstract/Free Full Text]

21 Kurz A, Sessler DI, Christensen R, Dechert M. Heat balance and distribution during the core-temperature plateau in anesthetized humans. Anesthesiology 1995; 83: 491–9.[Medline]





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