Shivering and shivering-like tremor during labor with and without epiduralanalgesia

Background: Effective treatment and prevention of hyperthermia and shiverin g-like tremor during labor is hindered by a poor understanding of their cau ses. The authors sought to identify the incidence of nonthermoregulatory sh ivering-like tremor and the factors associated with this activity. Methods: The authors studied women in spontaneous fullterm labor who chose epidural analgesia (n = 21) or opioid sedation (n = 31). Shivering-like tre mor and sweating were evaluated by observation, Core temperature was record ed in the external auditory canal using a compensated infrared thermometer. Arteriovenous shunt tone was evaluated with forearm minus fingertip skin t emperature gradients; gradients less than 0 mere considered evidence of vas odilation. Tremor was considered nonthermoregulatory when core temperature exceeded 37 degrees C and the arms were vasodilated. Pain was evaluated usi ng a visual analog scale. Results: Shivering-like tremor was observed in 18% of 290, 30-min data-acqu isition epochs before delivery. The patients were both normothermic and vas odilated during 15% of these epochs. Shivering was observed in 16% of 116 p ostdelivery epochs and was nonthermoregulatory in 28%. Sweating was observe d in 30% of predelivery epochs, and the patients were both hypothermic and vasoconstricted during 12%. The mean core temperature in patients given epi dural analgesia was approximately 0.2 degrees C greater than in those given sedation. Hyperthermia was observed during 10 epochs (38.4 +/- 0.3 degrees C) during epidural analgesia and during 10 epochs (38.4 +/- 0.3 degrees C) with sedation. The patients were vasoconstricted in more than 50% of these epochs in each group. Multivariate mixed-effects modeling identified high pain scores and vasoconstriction as significant predictors of shivering. Th ere were no predictors for shivering epochs in patients who were simultaneo usly normothermic and vasodilated. Significant predictors of sweating were time before delivery, high pain scores, hypothermia with vasoconstriction, high thermal comfort, and low mean skin temperature. There were no predicto rs for sweating epochs in patients who were simultaneously hypothermic and vasoconstricted. Conclusions: This study confirms the clinical impression that some peripart um shivering-like tremor is nonthermoregulatory. The authors also identifie d nonthermoregulatory sweating. These data indicate that shivering-like tre mor and sweating in the peripartum period is multifactorial.