Induced hypothermia in the management of refractory low cardiac output states following cardiac surgery in infants and children

Post-operative low cardiac output states remain a major cause ofmortality following cardiac surgery in infants and children. Since 1979 wehave used moderate induced whole-body hypothermia in the management oflow-output states refractory to conventional modes of therapy. This isbased not only upon the relationship between body temperature and oxygenconsumption, but also on experimental work showing a beneficial effect ofcooling upon myocardial contractility, particularly when there ispre-existing impairment of ventricular function. Between July 1986 and June1990, 20 children with refractory low-output states were cooled by means ofa thermostatically controlled water blanket to a rectal temperature of32-33 degrees C. The median age was 12 months (1 week-11 years) with amedian weight of 6 kg (3.5-33 kg). Ten children survived to leave hospitalwhile a further two made a haemodynamic recovery. There was a markedreduction in heart rate (P ≪ 0.001). The mean arterial pressure rose (P= 0.037) while there was a fall in mean atrial pressure (P ≪ 0.001).There was a significant improvement in the urine output (P = 0.002). A fallin the platelet count (P ≪ 0.001) was not accompanied by any change inthe white cell count (P = 0.15). Although it is impossible to say whethercooling influenced the outcome in any of these children, it was usuallyeffective in stabilising their clinical condition. The technique is simpleand has a sound theoretical basis.