Effectiveness of a circulating-water warming garment in rewarming after pediatric cardiac surgery using hypothermic cardiopulmonary bypass

Intraoperative temperature regulation in children using a liquid-warming garment

PURPOSE

Children undergoing operative intervention while induced under general anesthesia are at risk for experiencing a significant decrease in core body temperature that can lead to adverse systemic effects. Given that the head contributes an estimated 18% of a child's body surface area, we theorized that a liquid-warming garment applied to the head could control a pediatric patient's core body temperature during surgical procedures.

METHODS

Patients undergoing elective, non-cranial, general surgical procedures were enrolled in the study. A head garment with an embedded network of tubing was placed on the patient. The garment connected to a computer-controlled water bath that managed the temperature of the water in the tubing through a feedback mechanism.

RESULTS

Ten patients with ages ranging from 1 day to 3 years (mean age 10.5 months) were enrolled in this study. The average procedure length was 82.5 min. The mean core body temperature throughout the procedure for all-comers was 36.5 ± 0.9 °C with an overall mean difference in maximum and minimum temperatures of 1.32 ± 1.1 °C.

CONCLUSION

A liquid-warming garment applied to the head of pediatric surgical patients is an innovative and relatively low-cost means to regulate and to maintain the ideal core body temperature of patients undergoing surgical procedures.

Peri-operative warming devices: performance and clinical application

Since the adverse consequences of accidental peri-operative hypothermia have been recognised, there has been a rapid expansion in the development of new warming equipment designed to prevent it. This is a review of peri-operative warming devices and a critique of the evidence assessing their performance. Forced-air warming is a common and extensively tested warming modality that outperforms passive insulation and water mattresses, and is at least as effective as resistive heating. More recently developed devices include circulating water garments, which have shown promising results due to their ability to cover large surface areas, and negative pressure devices aimed at improving subcutaneous perfusion for warming. We also discuss the challenge of fluid warming, looking particularly at how devices' performance varies according to flow rate. Our ultimate aim is to provide a guide through the bewildering array of devices on the market so that clinicians can make informed and accurate choices for their particular hospital environment.

New circulating-water devices warm more quickly than forced-air in volunteers

BACKGROUND

Newer circulating-water systems supply more heat than forced-air, mainly because the heat capacity of water is much greater than for that of dry warm air and, in part, because they provide posterior as well as anterior heating. Several heating systems are available, but three major ones have yet to be compared directly. We therefore compared two circulating-water systems with a forced-air system during simulation of upper abdominal or chest surgery in volunteers.

METHODS

Seven healthy volunteers participated on three separate study days. Each day, they were anesthetized and cooled to a core temperature near 34 degrees C, which was maintained for 45-60 min. They were then rewarmed with one of three warming systems until distal esophageal core temperature reached 36 degrees C or anesthesia had lasted 8 h. The warming systems were 1) energy transfer pads (two split torso pads and two universal pads; Kimberly Clark, Roswell, GA); 2) circulating-water garment (Allon MTRE 3365 for cardiac surgery, Akiva, Israel); and 3) lower body forced-air warming (Bair Hugger #525, #750 blower, Eden Prairie, MN). Data are presented as mean +/- sd; P < 0.05 was statistically significant.

RESULTS

The rate of increase of core temperature from 34 degrees C to 36 degrees C was 1.2 degrees C +/- 0.2 degrees C/h with the Kimberly Clark system, 0.9 degrees C +/- 0.2 degrees C/h with the Allon system, and 0.6 degrees C +/- 0.1 degrees C/h with the Bair Hugger (P = 0.002).

CONCLUSIONS

The warming rate with the Kimberly Clark system was 25% faster than with the Allon system and twice as fast as with the Bair Hugger. Both circulating-water systems thus warmed hypothermic volunteers in significantly less time than the forced-air system.

Postoperative hypothermia and blood loss after the neonatal arterial switch procedure

BACKGROUND

Numerous studies have demonstrated that mild hypothermia helps reduce hypoxic/ischemic brain injury that may occur during neonatal cardiac procedures. However, traditional intensive care practices emphasize aggressive rewarming, and the risk of excessive bleeding that may be related to hypothermia.

METHODS

An analysis was conducted of prospectively collected temperature and blood loss data on 47 neonates (30 boys, 17 girls) with transposition of the great arteries who underwent an arterial switch operation at median age 6 days (range, 2 to 23 days) and a mean weight of 3.6 +/- 0.6 kg. Blood loss was compared between 26 patients with mean temperatures below 35.5 degrees C for first 6 hours after operation (mild hypothermia group) and 21 patients at 35.5 degrees C or higher (normothermia group). Repeated-measures analysis of variance and regression modeling were used to evaluate the association between temperature and blood loss and to detect outliers.

RESULTS

Total postoperative blood loss was 31 +/- 28 mL in the first 6 hours and 61 +/- 37 mL at 24 hours (range, 15 to 238 mL). Postoperative blood loss between two groups at 6 or 24 hours did not differ significantly. After two outliers were removed, no significant relationship remained between body temperature at 6 hours and cumulative blood loss at 24 hours.

CONCLUSIONS

Mild postoperative hypothermia does not increase blood loss in neonates after the arterial switch operation. Lack of a difference between the two groups is not likely due to the study being underpowered. We recommend avoidance of aggressive rewarming, which might exacerbate potential neurologic injury.

Water warming garment versus forced air warming system in prevention of intraoperative hypothermia during liver transplantation: a randomized controlled trial [ISRCTN32154832]

BACKGROUND: The authors compared two strategies for the maintenance of intraoperative normothermia during orthotopic liver transplantation (OLT): the routine forced-air warming system and the newly developed, whole body water garment. METHODS: In this prospective, randomized and open-labelled study, 24 adult patients were enrolled in one of two intraoperative temperature management groups during OLT. The water-garment group (N = 12) received warming with a body temperature (esophageal) set point of 36.8 degrees C. The forced air-warmer group (N = 12) received routine warming therapy using upper- and lower-body forced-air warming system. Body core temperature (primary outcome) was recorded intraoperatively and during the two hours after surgery in both groups. RESULTS: The mean core temperatures during incision, one hour after incision and during the skin closing were significantly higher (p < 0.05, t test with Bonferroni corrections for the individual tests) in the water warmer group compared to the control group (36.7 PlusMinus; 0.1, 36.7 PlusMinus; 0.2, 36.8 PlusMinus; 0.1 vs 36.1 PlusMinus; 0.4, 36.1 PlusMinus; 0.4, 36.07 PlusMinus; 0.4 degrees C, respectively). Moreover, significantly higher core temperatures were observed in the water warmer group than in the control group during the placement of cold liver allograft (36.75 PlusMinus; 0.17 vs 36.09 PlusMinus; 0.38 degrees C, respectively) and during the allograft reperfusion period (36.3 PlusMinus; 0.26 vs 35.52 PlusMinus; 0.42 degrees C, respectively). In addition, the core temperatures immediately after admission to the SICU (36.75 PlusMinus; 0.13 vs 36.22 PlusMinus; 0.3 degrees C, respectively) and at one hr (36.95 PlusMinus; 0.13 vs 36.46 PlusMinus; 0.2 degrees C, respectively) were significantly higher in the water warmer group, compared to the control group, whereas the core temperature did not differ significantly afte two hours in ICU in both groups. CONCLUSIONS: The investigated water warming system results in better maintenance of intraoperative normothermia than routine air forced warming applied to upper- and lower body.