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Core Temperature Monitoring in Obstetric Spinal Anesthesia Using an Ingestible Telemetric Sensor

du Toit, Leon, MBChB*; van Dyk, Dominique, FCA(SA)*; Hofmeyr, Ross, MMed, FCA(SA)*; Lombard, Carl, J., PhD(SA)†,‡; Dyer, Robert, A., FCA(SA), PhD*

doi: 10.1213/ANE.0000000000002326
Obstetric Anesthesiology: Original Clinical Research Report

BACKGROUND: Perioperative hypothermia may affect maternal and neonatal outcomes after obstetric spinal anesthesia. Core temperature is often poorly monitored during spinal anesthesia, due to the lack of an accurate noninvasive core temperature monitor. The aim of this study was to describe core temperature changes and temperature recovery during spinal anesthesia for elective cesarean delivery. We expected that obstetric spinal anesthesia would be associated with a clinically relevant thermoregulatory insult (core temperature decrease >1.0°C).

METHODS: A descriptive study was conducted in 28 women. An ingestible telemetric temperature sensor was used to record core temperature over time (measured every 10 seconds). The primary outcome was the maximum core temperature decrease after spinal anesthetic injection. The secondary outcomes were lowest absolute core temperature, time to lowest temperature, time to recovery of core temperature, hypothermic exposure (degree-hours below 37.0°C), and the time-weighted hypothermic exposure (median number of degrees below 37.0°C per hour). Basic descriptive statistics, median spline smooth, and integration of the area below the 37.0°C line of the temperature-over-time curve were utilized to analyze the data.

RESULTS: Intestinal temperature decreased by a mean (standard deviation) of 1.30°C (0.31); 99% confidence interval (CI), 1.14 to 1.46 after spinal anesthetic injection. The median (interquartile range [IQR]) time to temperature nadir was 0.96 (0.73–1.32) hours (95% CI, 0.88–1.22). Fourteen of the 28 participants experienced intestinal temperatures below 36.0°C after spinal injection. Temperature was monitored for a minimum of 8 hours after spinal injection. In 8 of 28 participants, intestinal temperature did not recover to baseline during the monitored period. A median (IQR) of 4.59 (3.38–5.92) hours (95% CI, 3.45–5.90) was required for recovery to baseline intestinal temperature in the remaining 20 patients. Participants experienced a median (IQR) of 1.97 (1.00–2.68) degree-hours of hypothermic exposure (95% CI, 1.23–2.45). The median (IQR) number of degrees below 37.0°C per hour was 0.45 (0.35–0.60) (95% CI, 0.36–0.58).

CONCLUSIONS: During cesarean delivery under spinal anesthesia, women experienced a rapid decrease in core temperature. Using an intestinal telemetric sensor, the perioperative thermal insult and recovery were documented with high resolution. Fifty percent of participants in this study became hypothermic. Although the surgical procedure is typically of short duration, women undergoing spinal anesthesia for cesarean delivery experience significant hypothermic exposure and compromised thermoregulation for several hours.

Published ahead of print August 9, 2017.

From the *Department of Anaesthesia and Perioperative Medicine, University of Cape Town, Cape Town, South Africa

Biostatistics Unit, South African Medical Research Council, Cape Town, South Africa

School of Public Health and Family Medicine, University of Cape Town, Cape Town, South Africa.

Published ahead of print August 9, 2017.

Accepted for publication June 25, 2017.

Funding: The Jan Pretorius Research Grant (South African Society of Anaesthetists) was used to purchase study equipment. The study was supported by Departmental research funding.

Conflicts of Interest: See Disclosures at the end of the article.

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Reprints will not be available from the authors.

Address correspondence to Leon du Toit, MBChB, Department of Anaesthesia and Perioperative Medicine, University of Cape Town, Groote Schuur Hospital, Main Rd, Observatory, Cape Town 7925, South Africa. Address e-mail to

© 2018 International Anesthesia Research Society
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