Thermoregulatory Response Thresholds During Spinal Anesthesia

Abstract

Reportedly, during spinal anesthesia, the shivering threshold is reduced approximately 1 degree C but the vasoconstriction threshold remains normal. Such divergence between the shivering and vasoconstriction thresholds is an unusual pattern of thermoregulatory impairment and suggests that the mechanisms of impairment during regional anesthesia may be especially complex. Accordingly, we sought to define the pattern of thermoregulatory impairment during spinal anesthesia by measuring response thresholds. Seven healthy women volunteered to participate on two study days. On one day, we evaluated thermoregulatory responses to hypothermia and hyperthermia during spinal anesthesia; on the other day, responses were evaluated without anesthesia. Upper body skin temperature was kept constant throughout the study. The volunteers were warmed via the lower body and cooled by central venous infusion of cold fluid. The core temperatures triggering a sweating rate of 40 g.m-2 x h-1, a finger flow of 0.1 mL/min, and a marked and sustained increase in oxygen consumption were considered the thermoregulatory thresholds for sweating, vasoconstriction, and shivering, respectively. Spinal anesthesia significantly decreased the thresholds for vasoconstriction and shivering, and the decrease in each was approximately 0.5 degree C. The range of temperatures not triggering thermoregulatory responses (those between sweating and vasoconstriction) was 0.9 +/- 0.6 degree C during spinal anesthesia. The synchronous decrease in the shivering and vasoconstriction thresholds during spinal anesthesia is consistent with thermoregulatory impairment resulting from altered afferent thermal input.

Randomised Double-Blind Comparative Study of Dexmedetomidine and Tramadol for Prevention of Perioperative Shivering in Transurethral Resection of Prostate Under Spinal Anaesthesia

“…[16] Further it also causes a redistribution of core heat from the trunk to the peripheral tissue. [17] The other risk factors for shivering is old age, cold irrigating fluid, operation theatre temperature and level of sensory block. [18] The commonest age group of patients presenting for TURP surgery is 50-70 years.…”

Persistent hypothermia after intrathecal morphine: case report and literature review

“…Normal body temperature was measured after treatment with a small dose of sublingual lorazepam. While spinal anesthesia causes a drop in body temperature due to vasodilatation and a loss of the shivering reflex, 4 the resulting hypothermia is usually treated successfully with external re-warming techniques, such as increasing the room temperature, provision of dry linens and gowns, and the use of forced-air warming blankets. In this case, other causes of perioperative hypothermia were considered as causes for this patient's hypothermia, including low ambient room temperatures, cold intraoperative intravenous fluid administration, high spinal blockade, and a relatively small bodyto-surface area ratio in this short-statured patient.…”

“…2 Intrathecal doses of morphine can also be associated with pruritis, urinary retention, nausea, and delayed respiratory depression. 2,3 While hypothermia can be a common consequence of spinal anesthesia due to vasodilatation and the loss of the shivering reflex, 4 several anecdotal reports describe persistent hypothermia in the obstetrical population after spinal anesthesia using intrathecal morphine. [5][6][7][8][9] This case report describes persistent hypothermia following spinal anesthesia using intrathecal morphine for total knee arthroplasty and the return to normothermia after sublingual lorazepam.…”

Thermoregulatory responses of spinal cord injured and able-bodied athletes to prolonged upper body exercise and recovery

“…The external ear was then insulated with cotton wool. 18 Aural temperature was employed in the present study as rectal temperature has been considered to be inappropriate as a measure of core temperature in paraplegics during exercise 19 and subject discomfort is often reported from the use of oesophageal probes. 20,21 Skin thermistors were placed at the forehead, forearm, upper arm, back, chest, abdomen, thigh and calf in order to establish the whole body thermoregulatory response.…”