Normothermic Cardiopulmonary Bypass Increases Cerebral Tissue Oxygenation during Combined Valve Surgery: A Single-Centre, Randomized Trial

OBJECTIVES:

In cardiac surgery, the choice of
temperature regimen during cardiopulmonary bypass (CPB) remains a
subject of debate. Hypothermia reduces tissue metabolic demands, but may
impair the autoregulation of cerebral blood flow and contribute to
neurological morbidity. The aim of this study was to evaluate the effect
of two different temperature regimens during CPB on the systemic oxygen
transport and the cerebral oxygenation during surgical correction of
acquired heart diseases.

METHODS:

In a prospective study,
we randomized 40 adult patients with combined valvular disorders
requiring surgical correction of two or more valves into two groups: (i)
a normothermic (NMTH) group (n = 20), in which the body core
temperature was maintained at 36.6°C during CPB and (ii) a hypothermic
(HPTH) group (n = 20), in which the body was cooled to a core
temperature of 32°C maintained throughout the period of CPB. The
systemic oxygen transport and the cerebral oxygen saturation (SctO2)
were assessed by means of a PiCCO2 haemodynamic monitor and a cerebral
oximeter, respectively. All the patients received standard perioperative
monitoring. We assessed haemodynamic and oxygen transport parameters,
the duration of mechanical ventilation and the length of the ICU and the
hospital stays.

RESULTS:

During CPB, central venous
oxygen saturation was significantly higher in the HPTH group but SctO2
was increased in the NMTH group (P < 0.05). Cardiac index, systemic oxygen delivery and consumption increased postoperatively in both groups. However, oxygen delivery and consumption were significantly higher in the NMTH group (P < 0.05). The duration of respiratory support and the length of ICU and hospital stays did not differ between the groups.

CONCLUSIONS:

During combined valve surgery,
normothermic CPB provides lower central venous oxygen saturation, but
increases cerebral tissue oxygenation when compared with the hypothermic
regimen.