Assessment of the efficiency of warming devices during neonatal surgery

Abstract

This study assessed the relative efficiency of different warming devices (surgical sheets covering the body and a tubegauze on the head, forced-air warming, warming mattress) commonly used to prevent body hypothermia during neonatal surgery. Dry heat losses were measured from a thermal manikin, which simulated a low-birth-weight neonate of 1,800 g. The manikin's surface temperatures (35.8 degrees C) corresponded to those of neonates nursed in closed incubators. Experiments were performed in a climatic chamber at an ambient temperature of 30 degrees C, as commonly found in operating theatres. The supine manikin was naked or covered with operative sheets with a 5x5 cm aperture over the abdomen. Its head could be covered by a tube-gauze. Additional warming was provided by conduction through a warming mattress (surface temperature, 39 degrees C) and/or by convection (Bair Hugger, forced-air temperature 38 degrees C). Covering the manikin with surgical sheets decreased the dry heat loss by 10.4 W. Additional forced-air warming was more efficient than the warming mattress to reduce the total dry heat loss (6.8 W vs 2.1 W). Heat losses were reduced by 7.9 W when combining the warming mattress and Bair Hugger. The heat loss from the head of the covered manikin was reduced from 4.5 W to 3.9 W when the head was covered with the tubegauze. Our data indicate that forced-air warming is more effective than conductive warming in preventing neonatal hypothermia during abdominal operations.

Peri‐operative warming devices: performance and clinical application

“…The authors of one paper described water mattresses as reasonably effective in rewarming hypothermic infants, although this study was only observational with no other active treatment group for comparison [121]. Most comparative studies in children have shown inferior performance of water mattress warming against forced-air warming [122] and water garments [123], which accords with studies in adults.…”

“…These are, however, more expensive than other warming methods [108]. Only a handful of studies have tested the use of water mattresses or garments in paediatric cases [121][122][123]. The authors of one paper described water mattresses as reasonably effective in rewarming hypothermic infants, although this study was only observational with no other active treatment group for comparison [121].…”

The safety and effectiveness of a modified convection heating system for children during anesthesia

“…(8) described benefit of convection heating over radiant in rewarming 24 children after cardiac bypass procedures. Subsequent reports have been disappointing either because they were: retrospective reviews [(9) 25 children having cardiac bypass surgery], gave almost no details about methodology – including technique of warming – device, temperature and so [(10) 10 children, (2) 17 neonates, correspondence] or used techniques known to give inaccurate results (3,10). Szmuk et al.…”

“…It has proven difficult to reverse this, particularly during long procedures in young children with open body cavities. It has been common practice to raise ambient temperature ( T ambient ) in pediatric theaters – the exact extent of this varying from institution to institution [25°C (2) to 30°C (3)]. Significant elevation increases the discomfort for staff, decreases their performance and has a potentially negative impact on the outcome of surgery.…”

A Simulation Study of Gel Pillow Heat Conductance

“…6,7 Normal body temperature is maintained by balancing heat loss with heat gain. 5,9,10 Because of these risk factors, heat exchange between the body and the surrounding environment is greater for an infant than for an adult. Infants have a larger body surface area in relation to body mass ratio.…”