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TYMPANIC TEMPERATURE DURING LABOUR AND PARTURITION
Br. J. Anaesth. (1975), 47, 600
TYMPANIC TEMPERATURE DURING LABOUR AND PARTURITION G. F. MARX AND D. A. Y. LOEW SUMMARY
Homeostasis of human body temperature is achieved by warm-sensitive neurones in the anterior portion of the hypothalamus. These induce sweating and vasodilatation for heat loss when their temperature exceeds a sharply set point near 37 °C. Similar warm-sensitive neurones inhibit, through a synaptic relay station in the posterior portion of the hypothalamus, the metabolic response to cold which is excited by cold-receptors of the skin firing from thresholds at 33-35°C (Benzinger, 1969). Thus, one small area in the brain stem functions as the terminal sensory centre of thermoregulation (Benzinger, Kitzinger and Pratt, 1963). The measurement of body temperature should, therefore, aim at central, brain stem, temperature. The blood supply to the brain stem from the carotid artery is closely associated with the tympanic membrane. Tympanic temperature has been shown to come close to representing hypothalamic temperature in rabbits (Tanabe and Takaori, 1964) and in primates (Rawson and Hammel, 1963). In man, a relationship has been noted between tympanic temperature and thermoregulatory responses such as rate of heat loss by sweating (Benzinger, Kitzinger and Pratt, 1963). We measured tympanic membrane temperature in 11 unselected healthy pregnant women at term (six primigravidae, five multigravidae), to gain information on central temperature changes during the active phase of labour, parturition and the immediate puerperium. METHOD
The study was performed in temperature-controlled labour and delivery rooms (21-23°C). All patients gave informed consent for the study. After checking that the auditory meatus was clean, a dispos-
able thermocouple was placed at the tympanic membrane, and temperature was monitored by a Radiation Systems tympanic thermometer. This was accepted readily by the patients. In two of the patients, rectal temperature was measured concurrently using a Yellow Springs telethermometer. However, the rectal probe became wet from leakage of amniotic fluid, was troublesome during internal examinations and bearing-down efforts, and had to be removed before delivery. RESULTS
Both tympanic and rectal temperatures increased progressively during the active phase of labour (table I). Tympanic thermometry proved to be more responsive, because increases in temperature observed by this method during the peak of each uterine contraction were not reflected in the rectal measurements. Furthermore, the cumulative increase in ear temperature exceeded that in rectal temperature in both patients in whom rectal temperature was measured. Increases in tympanic temperature associated with uterine contractions varied between 0.03 °C in a multigravida during the first stage of labour to 0.2°C in a primigravida during the second stage of labour. Both patients were receiving pethidinepromethazine medication. Progressive cumulative increases ranged from 0.04°C in a multigravida with less than 2 hr of active-phase labour to 2.0 c C in a primigravida with over 5 hr of active-phase labour. The mean increases are shown in table II. Three of the primigravidae received extradural GERTIE
F.
MARX,
MJ>., DOLORES A.
Y.
LOEW.
MJ>.,
Department of Anesthesiology, Albert Einstein College of Medicin; of Yeshiva University, 1300, Morris Park Avenue, Bronx, New York 10461, U.S.A. All correspondence to G.F.M.
Downloaded from http://bja.oxfordjournals.org/ at Johns Hopkins University on June 8, 2015
Tympanic temperature was monitored during labour and delivery in six primigravidae and five multigravidae. Temperature increased temporarily with each contraction and progressively during the course of labour. The increases, which were greater in primiparae than in multiparae (mean cumulative increase 1.46°C and 0.51°C respectively), reflect the metabolic expenditures associated with contraction of uterine and skeletal muscles.
601
TYMPANIC TEMPERATURE DURING LABOUR TABLE I. Summary of tympanic and rectal temperature recordings in a 17-year-old primigravida. Sedation: pethidine SO mg, promethazine 25 mgy t.y., at 9 a.m. Delivery: low forceps under nitrous oxide-oxygen analgesia. Tympanic temperature (Q (°Q Time (hour) 8.00 9.15 9.45 10.30 11.20
6 7 8 9 10 Prep. Delivery
Rectal temp, (CC) 37.5 38.0 38.0 38.0 38.3
35.8 36.7 37.0 37.3 37.5
35.6 36.6 36.9 37.2 37.4 37.2
37.3 37.4 37.2 37.2
TABLE II. Increases in tympanic temperature (mean ± standard deviation) in 11 unselected healthy parturient women. Increase (°C) Primigravidae Multigravidae (n=6) (n=5) Contraction of 1st stage 0.075±0.041 0.040±0.010 Contraction of 2nd stage 0.112 ±0.054 0.064 ±0.020 Cumulative during active stage and parturition 1.460±0.553* 0.510±0.167* *P<0.01
analgesia and three received intravenous medication using a mixture of pethidine and promethazine, combined with nitrous oxide analgesia. There was no significant effect on temperature response associated with either method of analgesia (table HI). Following delivery of infant and placenta, there was a rapid decrease of from 0.05 °C to 0.2 °C (mean 0.13°C; SD 0.06°C) with little further change during the next 20-30 min of observation; no correlation could be demonstrated between the increase during labour and the decline following delivery. However, postpartum temperatures were higher than those at the onset of labour in all primigravidae and three of the multigravidae. TABLE III. Mean increases in tympanic temperature in six primigravidae receiving pain relief by either segmented extradural block or pethidine-promethazine medication i.v. Duration of labour was longer in the women who received extradural analgesia. Increase (°C) Extradural Pethidineblock promethazine (n=3) (n=3) Contraction of 1st stage Contraction of 2nd stage Cumulative during active stage
0.073 0.107 1.490
0.077 0.117 1.430
Downloaded from http://bja.oxfordjournals.org/ at Johns Hopkins University on June 8, 2015
11.55 12.10 12.15 12.30
Dilatation cervix No During (cm) contraction contraction
DISCUSSION
The changes in tympanic temperature during labour and parturition resemble those in oxygen consumption and acid metabolites noted in previous studies. Oxygen consumption was found to increase during each contraction, to return to lower values during periods of uterine relaxation, and to show a trend towards a cumulative increase. In 19 parturient women, oxygen consumption increased from an average of 300 ml/min during the early phase of the first stage to 350 ml/min towards the end of the first stage and 470 ml/min during the second stage. Within 30 min of delivery, it decreased to 370 ml/min (Gemzell et al., 1957). Similarly, arterial lactate, pyruvate, and excess lactate concentrations studied in 10 patients, increased steadily during the course of labour, reached peak values at the time of delivery, and declined progressively thereafter. Increases in the metabolites occurred with every uterine contraction regardless of whether the woman was aware of the contraction or not, that is, regardless of whether pain relief was by regional block or systemic drug therapy. The maYimnm values of excess lactate were greater in the primiparous than in the multiparous patient group (Marx and Green, 1964). When variations in tympanic temperature were studied during acute changes in cerebral blood flow produced by hyperventilation or following 5% carbon dioxide administration in anaesthetized surgical patients (Tayyab and Halevy, unpublished observations), hypocapnia was associated with a decrease in temperature after an average lag period of 15 min, but hypercapnia did not lead to a significant temperature response. We conclude, therefore, that the increases in central temperature during labour are not related to circulatory changes associated with the expulsion of Wood out of the uterine sinuses into the central circulation, but rather reflect the metabolic expenditure associated with contraction of the uterus and skeletal muscles. Muscular exercise is accompanied by heat production leading to increases in body temperature, the magnitude of which varies with the metabolic level of the work accomplished (Bazett, 1949). Thus, depending on frequency and amplitude of uterine contractions and intensity of bearing-down efforts, increases in central temperature during labour may be considerable. The absence of a significant difference in temperature response between the primigravid patients receiving regional block and those on
BRITISH JOURNAL OF ANAESTHESIA
602
LA TEMPERATURE TYMPANIQUE DURANT LE TRAVAIL ET LA PARTURITION RESUME
On a surveille' la temperature tympanique durant le travail et l'accouchement chez six primipares et cinq multipares. La temperature augmentait temporairement lors dc chacunc des contractions et augmentait graduellement au cours du travail. Les augmentations, qui itaient plus importantes chez les primipares que chcz les multipares (augmentations cumulatives moyennes de 1,46°C et 0,51 °C respectivement), refletent les depenses mettboliques assoaces a la contraction des muscles ut6rins et squelettiques. TYMPANISCHE TEMPERATUR WAHREND DER WEHEN UND DER GEBURT
REFERENCES
ZUSAMMENFASSUNG
Bazett, H. C 0-949). The regulation of body temperatures; in Physiology of Heat Regulation and the Science of Clothing, p. 109. Philadelphia: W. B. Saunders Co. Benzinger, T. H. (1969). Clinical temperature: new physiological basis. JAMA., 209, 1200. Kitzinger, C , and Pratt, A. W. (1963). The human thermostat; in Temperature: Its Measurement and Control in Science and Industry, p. 637. New York: Reinhold Publishing Corp. Gemzell, C. A., Robbe, H., Stem, B., and Strom, G. (1957). Observations on circulatory changes and muscular work in normal labour. Ada Obstet. Gynecol. Scand., 36, 75. Marx, G. F., and Greene, N. M. (1964). Maternal lactate, pyruvate, and excess lactate production during labor and delivery. Am. J. Obstet. GynecoL, 90, 786. Rawson, R. O.? and Hammel, H. T. (1963). Hypothalamic and tympanic membrane temperatures in rhesus monkeys. Fed. Proc, 22, 283. Tanabe, K., and Takaori, S. (1964). Effects of cooling and wanning of the common carotid arteries on the brain and tympanic membrane temperatures in the rabbit. Jap. J. Pharmacol, 14, 67.
Die tympanische Temperatur wurde bei 6 Primiparae und 5 Pluriparae wahrend der Wchen und bei dcr Geburt iiberpruft. Die Temperatur stieg temporar bei jeder Zusammenziehung an, und progrcssiy weiter im Verlauf der Wehen. Diese Anstiege, die bei Primiparae groBcr waren als bei Pluriparae (mittlerer Gesamtanstieg jeweils 1,46°C und 0,51 ° Q , zeigen den metabolischen Aufwand, den Zusammenziehungen uteriner und Skelettmuskeln erfordern. TEMPERATURA TIMPANICA DURANTE DOLORES DEL PARTO Y PARTO SUMARIO
Se controld la temperatura timpinica durante los dolores del parto y el parto en seis pnmigravidas y cinco multigrividas. La temperatura aument6 temporalmente con cada contracci6n y progresivamente durante el curso del parto. Los aumentos, que fueron mayores en las primlparas que en las muldparas (aumento acumulativo principal del 1,46°C y 0,51 *C respectivamente), reflejaron los gastos metab61icos asociados con la contracd6n de los musculos uterinos y esqueWticos.
Downloaded from http://bja.oxfordjournals.org/ at Johns Hopkins University on June 8, 2015
intravenous medication may be the result of various factors. First, the extradural blocks were limited to the lower thoracic and upper lumbar segments, permitting the patients considerable motion of the lower extremities, while the patients under systemic drugs exhibited little movement Thus, the amount of general muscular activity may have been similar in both groups. Second, bearing-down efforts are not significantly reduced by extradural analgesia, because the power of the auxiliary forces of labour is retained. Finally, the metabolic contribution of the contracting uterus appears to outweigh that of the skeletal musculature.
TYMPANIC TEMPERATURE DURING LABOUR AND PARTURITION G. F. MARX AND D. A. Y. LOEW SUMMARY
Homeostasis of human body temperature is achieved by warm-sensitive neurones in the anterior portion of the hypothalamus. These induce sweating and vasodilatation for heat loss when their temperature exceeds a sharply set point near 37 °C. Similar warm-sensitive neurones inhibit, through a synaptic relay station in the posterior portion of the hypothalamus, the metabolic response to cold which is excited by cold-receptors of the skin firing from thresholds at 33-35°C (Benzinger, 1969). Thus, one small area in the brain stem functions as the terminal sensory centre of thermoregulation (Benzinger, Kitzinger and Pratt, 1963). The measurement of body temperature should, therefore, aim at central, brain stem, temperature. The blood supply to the brain stem from the carotid artery is closely associated with the tympanic membrane. Tympanic temperature has been shown to come close to representing hypothalamic temperature in rabbits (Tanabe and Takaori, 1964) and in primates (Rawson and Hammel, 1963). In man, a relationship has been noted between tympanic temperature and thermoregulatory responses such as rate of heat loss by sweating (Benzinger, Kitzinger and Pratt, 1963). We measured tympanic membrane temperature in 11 unselected healthy pregnant women at term (six primigravidae, five multigravidae), to gain information on central temperature changes during the active phase of labour, parturition and the immediate puerperium. METHOD
The study was performed in temperature-controlled labour and delivery rooms (21-23°C). All patients gave informed consent for the study. After checking that the auditory meatus was clean, a dispos-
able thermocouple was placed at the tympanic membrane, and temperature was monitored by a Radiation Systems tympanic thermometer. This was accepted readily by the patients. In two of the patients, rectal temperature was measured concurrently using a Yellow Springs telethermometer. However, the rectal probe became wet from leakage of amniotic fluid, was troublesome during internal examinations and bearing-down efforts, and had to be removed before delivery. RESULTS
Both tympanic and rectal temperatures increased progressively during the active phase of labour (table I). Tympanic thermometry proved to be more responsive, because increases in temperature observed by this method during the peak of each uterine contraction were not reflected in the rectal measurements. Furthermore, the cumulative increase in ear temperature exceeded that in rectal temperature in both patients in whom rectal temperature was measured. Increases in tympanic temperature associated with uterine contractions varied between 0.03 °C in a multigravida during the first stage of labour to 0.2°C in a primigravida during the second stage of labour. Both patients were receiving pethidinepromethazine medication. Progressive cumulative increases ranged from 0.04°C in a multigravida with less than 2 hr of active-phase labour to 2.0 c C in a primigravida with over 5 hr of active-phase labour. The mean increases are shown in table II. Three of the primigravidae received extradural GERTIE
F.
MARX,
MJ>., DOLORES A.
Y.
LOEW.
MJ>.,
Department of Anesthesiology, Albert Einstein College of Medicin; of Yeshiva University, 1300, Morris Park Avenue, Bronx, New York 10461, U.S.A. All correspondence to G.F.M.
Downloaded from http://bja.oxfordjournals.org/ at Johns Hopkins University on June 8, 2015
Tympanic temperature was monitored during labour and delivery in six primigravidae and five multigravidae. Temperature increased temporarily with each contraction and progressively during the course of labour. The increases, which were greater in primiparae than in multiparae (mean cumulative increase 1.46°C and 0.51°C respectively), reflect the metabolic expenditures associated with contraction of uterine and skeletal muscles.
601
TYMPANIC TEMPERATURE DURING LABOUR TABLE I. Summary of tympanic and rectal temperature recordings in a 17-year-old primigravida. Sedation: pethidine SO mg, promethazine 25 mgy t.y., at 9 a.m. Delivery: low forceps under nitrous oxide-oxygen analgesia. Tympanic temperature (Q (°Q Time (hour) 8.00 9.15 9.45 10.30 11.20
6 7 8 9 10 Prep. Delivery
Rectal temp, (CC) 37.5 38.0 38.0 38.0 38.3
35.8 36.7 37.0 37.3 37.5
35.6 36.6 36.9 37.2 37.4 37.2
37.3 37.4 37.2 37.2
TABLE II. Increases in tympanic temperature (mean ± standard deviation) in 11 unselected healthy parturient women. Increase (°C) Primigravidae Multigravidae (n=6) (n=5) Contraction of 1st stage 0.075±0.041 0.040±0.010 Contraction of 2nd stage 0.112 ±0.054 0.064 ±0.020 Cumulative during active stage and parturition 1.460±0.553* 0.510±0.167* *P<0.01
analgesia and three received intravenous medication using a mixture of pethidine and promethazine, combined with nitrous oxide analgesia. There was no significant effect on temperature response associated with either method of analgesia (table HI). Following delivery of infant and placenta, there was a rapid decrease of from 0.05 °C to 0.2 °C (mean 0.13°C; SD 0.06°C) with little further change during the next 20-30 min of observation; no correlation could be demonstrated between the increase during labour and the decline following delivery. However, postpartum temperatures were higher than those at the onset of labour in all primigravidae and three of the multigravidae. TABLE III. Mean increases in tympanic temperature in six primigravidae receiving pain relief by either segmented extradural block or pethidine-promethazine medication i.v. Duration of labour was longer in the women who received extradural analgesia. Increase (°C) Extradural Pethidineblock promethazine (n=3) (n=3) Contraction of 1st stage Contraction of 2nd stage Cumulative during active stage
0.073 0.107 1.490
0.077 0.117 1.430
Downloaded from http://bja.oxfordjournals.org/ at Johns Hopkins University on June 8, 2015
11.55 12.10 12.15 12.30
Dilatation cervix No During (cm) contraction contraction
DISCUSSION
The changes in tympanic temperature during labour and parturition resemble those in oxygen consumption and acid metabolites noted in previous studies. Oxygen consumption was found to increase during each contraction, to return to lower values during periods of uterine relaxation, and to show a trend towards a cumulative increase. In 19 parturient women, oxygen consumption increased from an average of 300 ml/min during the early phase of the first stage to 350 ml/min towards the end of the first stage and 470 ml/min during the second stage. Within 30 min of delivery, it decreased to 370 ml/min (Gemzell et al., 1957). Similarly, arterial lactate, pyruvate, and excess lactate concentrations studied in 10 patients, increased steadily during the course of labour, reached peak values at the time of delivery, and declined progressively thereafter. Increases in the metabolites occurred with every uterine contraction regardless of whether the woman was aware of the contraction or not, that is, regardless of whether pain relief was by regional block or systemic drug therapy. The maYimnm values of excess lactate were greater in the primiparous than in the multiparous patient group (Marx and Green, 1964). When variations in tympanic temperature were studied during acute changes in cerebral blood flow produced by hyperventilation or following 5% carbon dioxide administration in anaesthetized surgical patients (Tayyab and Halevy, unpublished observations), hypocapnia was associated with a decrease in temperature after an average lag period of 15 min, but hypercapnia did not lead to a significant temperature response. We conclude, therefore, that the increases in central temperature during labour are not related to circulatory changes associated with the expulsion of Wood out of the uterine sinuses into the central circulation, but rather reflect the metabolic expenditure associated with contraction of the uterus and skeletal muscles. Muscular exercise is accompanied by heat production leading to increases in body temperature, the magnitude of which varies with the metabolic level of the work accomplished (Bazett, 1949). Thus, depending on frequency and amplitude of uterine contractions and intensity of bearing-down efforts, increases in central temperature during labour may be considerable. The absence of a significant difference in temperature response between the primigravid patients receiving regional block and those on
BRITISH JOURNAL OF ANAESTHESIA
602
LA TEMPERATURE TYMPANIQUE DURANT LE TRAVAIL ET LA PARTURITION RESUME
On a surveille' la temperature tympanique durant le travail et l'accouchement chez six primipares et cinq multipares. La temperature augmentait temporairement lors dc chacunc des contractions et augmentait graduellement au cours du travail. Les augmentations, qui itaient plus importantes chez les primipares que chcz les multipares (augmentations cumulatives moyennes de 1,46°C et 0,51 °C respectivement), refletent les depenses mettboliques assoaces a la contraction des muscles ut6rins et squelettiques. TYMPANISCHE TEMPERATUR WAHREND DER WEHEN UND DER GEBURT
REFERENCES
ZUSAMMENFASSUNG
Bazett, H. C 0-949). The regulation of body temperatures; in Physiology of Heat Regulation and the Science of Clothing, p. 109. Philadelphia: W. B. Saunders Co. Benzinger, T. H. (1969). Clinical temperature: new physiological basis. JAMA., 209, 1200. Kitzinger, C , and Pratt, A. W. (1963). The human thermostat; in Temperature: Its Measurement and Control in Science and Industry, p. 637. New York: Reinhold Publishing Corp. Gemzell, C. A., Robbe, H., Stem, B., and Strom, G. (1957). Observations on circulatory changes and muscular work in normal labour. Ada Obstet. Gynecol. Scand., 36, 75. Marx, G. F., and Greene, N. M. (1964). Maternal lactate, pyruvate, and excess lactate production during labor and delivery. Am. J. Obstet. GynecoL, 90, 786. Rawson, R. O.? and Hammel, H. T. (1963). Hypothalamic and tympanic membrane temperatures in rhesus monkeys. Fed. Proc, 22, 283. Tanabe, K., and Takaori, S. (1964). Effects of cooling and wanning of the common carotid arteries on the brain and tympanic membrane temperatures in the rabbit. Jap. J. Pharmacol, 14, 67.
Die tympanische Temperatur wurde bei 6 Primiparae und 5 Pluriparae wahrend der Wchen und bei dcr Geburt iiberpruft. Die Temperatur stieg temporar bei jeder Zusammenziehung an, und progrcssiy weiter im Verlauf der Wehen. Diese Anstiege, die bei Primiparae groBcr waren als bei Pluriparae (mittlerer Gesamtanstieg jeweils 1,46°C und 0,51 ° Q , zeigen den metabolischen Aufwand, den Zusammenziehungen uteriner und Skelettmuskeln erfordern. TEMPERATURA TIMPANICA DURANTE DOLORES DEL PARTO Y PARTO SUMARIO
Se controld la temperatura timpinica durante los dolores del parto y el parto en seis pnmigravidas y cinco multigrividas. La temperatura aument6 temporalmente con cada contracci6n y progresivamente durante el curso del parto. Los aumentos, que fueron mayores en las primlparas que en las muldparas (aumento acumulativo principal del 1,46°C y 0,51 *C respectivamente), reflejaron los gastos metab61icos asociados con la contracd6n de los musculos uterinos y esqueWticos.
Downloaded from http://bja.oxfordjournals.org/ at Johns Hopkins University on June 8, 2015
intravenous medication may be the result of various factors. First, the extradural blocks were limited to the lower thoracic and upper lumbar segments, permitting the patients considerable motion of the lower extremities, while the patients under systemic drugs exhibited little movement Thus, the amount of general muscular activity may have been similar in both groups. Second, bearing-down efforts are not significantly reduced by extradural analgesia, because the power of the auxiliary forces of labour is retained. Finally, the metabolic contribution of the contracting uterus appears to outweigh that of the skeletal musculature.