Intravascular Volume Expansion During Therapeutic Moderate Hypothermia for Brain-Injured Patients: Preliminary Report

Summary

Hemodynamic depressions during moderate hypothermia may worsen cerebral ischemia after brain injury. In this preliminary report, we examined retrospectively the effects of intravascular volume expansion on hemodynamic changes, intracranial pressure (ICP), and internal jugular oxygen saturation (SJO₂) in seven brain-injured patients, who were selected because of their elevated ICPs even after induction of hypothermia. All patients were ventilated, and hypothermia was induced by surface cooling using midazolam, buprenorphine, and vecuronium. After the hypothermic period (divided into the initial, middle, and late phases), patients were gradually rewarmed at a rate of approximately 1°C per day. Mean blood pressure (MBP), central venous pressure (CVP), cerebral perfusion pressure (CPP), cardiac output (CO), ICP, and SJO₂were measured. Despite a large amount of infusion ranging from approximately 4000 to 5000 ml/day, ICP decreased from the middle phase compared to the initial phase of the therapy. After such volume expansion, higher levels of CVP (ranging from 9.7 ± 0.8 to 10.7 ± 1.5 mmHg) were found during the hypothermic period in association with CO levels (5.2 ± 0.1 to 5.3 ± 0.21/min) similar to those of normothermia. Sustained CPP was accompanied by reduced ICP, increased SJO₂, and augmented CO. These results suggest that even a large amount of infusion to the brain-injured patients decreases ICP and improves CO during moderate hypothermia, which may be beneficial to the cerebral circulation and metabolism in the patients. The current study warrants further future studies to test such a hypothesis.