Reduction in the Shivering Threshold Is Proportional to Spinal Block Height

Background Hypothermia is nearly as common, and may be as severe, during spinal and epidural anesthesia as during general anesthesia. The authors have proposed that thermoregulatory failure results when regional anesthesia increases apparent leg skin temperature to a level far exceeding actual leg skin temperature. Extensive dermatomal blocks will alter thermal input to the hypothalamus from a greater skin‐surface area more than less extensive ones and thus might be expected to impair central thermoregulatory control more. Accordingly, they tested the hypothesis that reduction in the shivering threshold is directly related to the number of dermatomes blocked during spinal anesthesia. Methods Eleven men, aged 62+/‐6 yr (mean+/‐SD), undergoing urologic surgery were studied. Ice‐cold lactated Ringer's solution was administered intravenously before spinal blockade, and the shivering threshold (triggering core temperature) was established. Spinal anesthesia then was induced using a randomly assigned dose of 0.5% bupivacaine (2–4 ml). Again, sufficient cold lactated Ringer's solution was given to induce shivering. Tympanic membrane, ambient and skin temperatures were measured, and extent of block was defined by loss of temperature discrimination. Presence of shivering was evaluated by a blinded observer. Mean upper‐body skin and ambient temperatures, cooling rates and intravenous fluid volumes at the two thresholds were compared using paired, two‐tailed t tests (P < 0.05). Linear regression defined the relationship between reduction in shivering threshold and the number of dermatomes blocked. Results There were no significant differences between mean upper‐body skin and ambient temperatures, cooling rates or intravenous fluid volumes at the control and spinal shivering thresholds. Spinal anesthesia reduced the shivering threshold in direct relation to the number of dermatomes blocked: Delta threshold = 0.74 ‐ 0.06 (dermatomes blocked); r2 = 0.58, P < 0.006. Conclusions Extensive spinal blockade impairs central thermoregulatory control more than less extensive blockade. Clinicians can thus anticipate more core hypothermia during extensive than during restricted spinal blockade.

[1]  D. Sessler,et al.  Mild hypothermia increases blood loss and transfusion requirements during total hip arthroplasty , 1996, The Lancet.

[2]  D. Sessler,et al.  Shivering Threshold during Spinal Anesthesia Is Reduced in Elderly Patients , 1995, Anesthesiology.

[3]  M. Ozaki,et al.  Heat Flow and Distribution during Epidural Anesthesia , 1995, Anesthesiology.

[4]  Hank Lin,et al.  Increasing Mean Skin Temperature Linearly Reduces the Core‐ temperature Thresholds for Vasoconstriction and Shivering in Humans , 1995, Anesthesiology.

[5]  D. Sessler,et al.  INCREASING MEAN SKIN TEMPERATURE LINEARLY REDUCES THE VASOCONSTRICTION AND SHIVERING THRESHOLDS IN HUMANS , 1994 .

[6]  M. Ozaki,et al.  Epidural anesthesia increases apparent leg temperature and decreases the shivering threshold. , 1994 .

[7]  M. Ozaki,et al.  Thermoregulatory Thresholds during Epidural and Spinal Anesthesia , 1994, Anesthesiology.

[8]  D. Himpe,et al.  Bair hugger forced-air warming maintains normothermia more effectively than thermo-lite insulation. , 1994, Journal of clinical anesthesia.

[9]  Makoto Ozaki,et al.  Rate and Gender Dependence of the Sweating, Vasoconstriction, and Shivering Thresholds in Humans , 1994, Anesthesiology.

[10]  M. Ozaki,et al.  Epidural Anesthesia Impairs Both Central and Peripheral Thermoregulatory Control during General Anesthesia , 1994, Anesthesiology.

[11]  A. Kurz,et al.  Thermoregulatory response thresholds during spinal anesthesia. , 1993, Anesthesia and analgesia.

[12]  L. Beydon,et al.  Clonidine Comparably Decreases the Thermoregulatory Thresholds for Vasoconstriction and Shivering in Humans , 1993, Anesthesiology.

[13]  D. Sessler,et al.  The Threshold for Thermoregulatory Vasoconstriction during Nitrous Oxide/Isoflurane Anesthesia Is Lower in Elderly Than in Young Patients , 1993, Anesthesiology.

[14]  D. Sessler,et al.  Preanesthetic skin-surface warming reduces redistribution hypothermia caused by epidural block. , 1993, Anesthesia and analgesia.

[15]  D. Sessler,et al.  Heat Loss in Humans Covered with Cotton Hospital Blankets , 1993, Anesthesia and analgesia.

[16]  A. Kurz,et al.  Forced-air warming maintains intraoperative normothermia better than circulating-water mattresses. , 1993, Anesthesia and analgesia.

[17]  S. Gottlieb,et al.  Unintentional Hypothermia Is Associated with Postoperative Myocardial Ischemia , 1993, Anesthesiology.

[18]  A. Kimball,et al.  Epidural versus general anesthesia, ambient operating room temperature, and patient age as predictors of inadvertent hypothermia. , 1992, Anesthesiology.

[19]  R. Thisted,et al.  Central temperature changes are poorly perceived during epidural anesthesia. , 1992, Anesthesiology.

[20]  D. Sessler,et al.  Perioperative thermal insulation. , 1991, Anesthesiology.

[21]  D. Sessler,et al.  Thermal balance and tremor patterns during epidural anesthesia. , 1991, Anesthesiology.

[22]  D. Sessler,et al.  The thermoregulatory threshold in infants and children anesthetized with isoflurane and caudal bupivacaine. , 1990, Anesthesiology.

[23]  D. Sessler,et al.  Thermoregulatory vasoconstriction decreases cutaneous heat loss. , 1990, Anesthesiology.

[24]  M. N. Workhoven.  Intravenous fluid temperature, shivering, and the parturient. , 1986 .

[25]  M. Bengtsson.  Changes in Skin Blood Flow and Temperature during Spinal Analgesia Evaluated by Laser Doppler Flowmetry and Infrared Thermography , 1984, Acta anaesthesiologica Scandinavica.

[26]  E. Theriot,et al.  Shivering Following Epidural Anesthesia in Obstetrics , 1984, Regional anesthesia and pain medicine.

[27]  C F Roe,et al.  Effect of bowel exposure on body temperature during surgical operations. , 1971, American journal of surgery.

[28]  R. H. Morris.  Operating room temperature and the anesthetized, paralyzed patient. , 1971 .

[29]  R. H. Morris.  Influence of Ambient Temperature on Patient Temperature During Intraabdominal Surgery , 1971, Annals of surgery.

[30]  A. W. Pratt,et al.  THE THERMOSTATIC CONTROL OF HUMAN METABOLIC HEAT PRODUCTION. , 1961, Proceedings of the National Academy of Sciences of the United States of America.

[31]  T. P. Lim.  Central and peripheral control mechanisms of shivering and its effects on respiration. , 1960, Journal of applied physiology.