A comparison of patient rewarming devices after cardiac surgery

Abstract

SummaryThree regimens for rewarming patients after cardiac surgery involving hypothermic cardiopulmonary bypass were studied in 30 patients. The control group (n = 10) received no active rewarming, the oesophageal group (n = 10) was warmed centrally using an oesophageal heat exchanger and the radiant group (n = 10) was warmedperipherally with an overhead radiant heater. There were no statistically SignEficant diFerences between the groups apart from the higher mean skin temperatures in the peripheral group. Key wordsTemperature; body. Surgery; cardiovascular. Equipment.A device for noninvasive central rewarming of hypothermic patients by recirculation of warm water through an oesophageal tube has recently become available (The Exacon thermal therapy system) and was effective in experimental hypothermia in dogs,' accidental hypothermia in humans2 and in prevention of peroperative hypothermia.' There have been no studies using this technique after cardiopulmonary bypass procedures; however, peripheral warming using a radiant overhead heater was demonstrated to be effective in this situation."h This study was designed to compare the efficacy of central oesophageal rewarming with peripheral rewarming using a radiant overhead heater (the Aragona mobile thermal ceiling) after cardiac surgery. MethodsThirty patients after routine coronary artery bypass grafting were randomly allocated to one of three groups: a control group, no active rewarming in the postoperative period; an oesophageal group, rewarming using the Exacon TT8200 thermal therapy system. This consists of a disposable double lumen oesophageal tube and a base unit comprising water heater, circulating pump and monitor/ alarm module. Sterile distilled water is circulated through the oesophageal tube at a rate of 3 litres/minute. The temperature of the circulating water is variable and in this study the maximum temperature of 42°C was used. The oesophageal tube was inserted in theatre after heparinisation had been reversed; a radiant group, rewarming using the Aragona mobile thermal ceiling. The heating surface was mounted approximately 1 m above the patients and the output adjusted initially to maximum but then decreased to maintain skin temperature at 37°C. The patients were treated identically in all other respects.Anaesthesia consisted of premedication with papaveretum, hyoscine and droperidol given 1-2 hours pre-operatively and induction with a sleep dose of thiopentone and fentanyl (50 pg/kg). Neuromuscular blockade was achieved using pancuronium (0.15 mg/kg) and anaesthesia was maintained with 50% nitrous oxide in oxygen; muscle relaxation was not reversed at the end of surgery. Bypass temperatures of 27-28°C were used for all patients. Temperature monitoring probes were attached on arrival in the intensive care unit (ICU) and allowed to stabilise for 15 minutes before the readings started. Intermittent positive pressure ventilation was continued after operation with oxygen-enriched air. Humidification of inspired gases was achieved using the Engstrom E...

Pre-emptive use of the space blanket reduces shivering after general anaesthesia

“…Perhaps the most persuasive evidence in support of the thermogenic theory is that the application of radiant heat was found to greatly diminish or abolish shivering [13,21], while Lennon and colleagues found a forced air warming system effective [23]. However, a comparison of physical methods of treating established shivering after anaesthesia for cardiac surgery found direct radiant heaters and oesophageal heat exchangers less than satisfactory [24].…”

“…Most authors agree that prevention of postoperative shivering is desirable [1,2,16,17,28]. The use of drugs to treat established shivering has been questioned, as it suppresses physiological attempts to restore normothermia [24], while there are conflicting reports on the efficacy of physical methods [13,23,24]. These forms of technology are also expensive and cumbersome.…”

Convective warming blankets improve peroperative heat preservation in congenital heart surgery

“…Previous studies have shown, that in patients treated with radiant heating systems during the postoperative period, postoperative rewarming was accomplished in a shorter time and almost without endogenous muscular thermogenesis ( 18, 21–23). So far, we have only used the Bairhugger peroperatively in congenital heart surgery.…”

Convective warming combined with vasodilator therapy accelerates core rewarming after coronary artery bypass surgery

“…Such "after-drop" in core temperature is possibly related to the redistribution of heat from the core to other body compartments, especially skeletal muscle [15]. Other types of heating devices have been tried in this setting; the oesophageal heat exchanger, for example, has been shown to be ineffective and radiant heaters to be effective only in warming the skin but at the expense of convenience [16].…”