Does hyperventilation improve operating condition during supratentorial craniotomy? A multicenter randomized crossover trial.

BACKGROUND: Hyperventilation has been an integral, but poorly validated part of neuroanesthetic practice. We conducted a two-period, crossover, randomized trial to evaluate surgeon-assessed brain bulk and measured intracranial pressure (ICP) in patients undergoing craniotomy for removal of supratentorial brain tumors during moderate hypocapnia or normocapnia. METHODS: Two-hundred and seventy-five adult patients with supratentorial brain tumors were randomized to one of two treatment sequences: hyperventilation (arterial carbon dioxide tension, PaCO2 = 25 +/- 2 mm Hg) followed by normoventilation (PaCO2 = 37 +/- 2 mm Hg) or normoventilation followed by hyperventilation. Ventilation and end-tidal CO2 tension were kept constant for 20 min. Patients were also randomly assigned to receive a propofol infusion or isoflurane anesthesia. At the end of each study period, subdural ICP was measured and the neurosurgeon, blinded to the treatment group, was asked to rate the brain bulk using a four-point scale. RESULTS: Using a generalized estimation equation model, we found that hyperventilation decreased the risk of increased brain bulk by 45%, P = 0.004, 95% confidence intervals 22% to 61%, and the number needed to treat was 8. The mean (+/-SD) ICP during hyperventilation, 12.3 +/- 8.1 mm Hg, was lower than that during normoventilation, 16.2 +/- 9.6 mm Hg, P < 0.001. Anesthetic regimen did not affect brain bulk assessment or ICP. CONCLUSIONS: In patients with supratentorial brain tumors, intraoperative hyperventilation improves surgeon-assessed brain bulk which was associated with a decrease in ICP.

ECG changes in pediatric patients with severe head injury.

Although ECG changes in subarachnoid hemorrhage and head injury have been described in adults, they have been rarely reported in children. We present 3 pediatric head-injured patients who developed severe ischemic changes on ECG. Three children (ages 9 months, 2.5 years, and 12 years) were admitted with severe head injury. All of them developed progressive ST segment depression of 4 to 7 mm during the surgical procedure. The first case, a 9-month-old child, also had bradycardia and cardiac arrest following ST depression. He was promptly resuscitated with simultaneous evacuation of extradural hematoma. In the other two cases, ST depression also gradually came up to baseline coinciding with surgical treatment of main pathology. All of the patients were ventilated postoperatively for 36 to 48 hours and discharged with no neurologic deficit. ECG changes and myocardial ischemia in head-injured patients have been attributed to extreme sympathetic stimulation and raised intracranial pressure in adults. But there has been no such systematic study in children. From our observations, we can conclude that ECG changes do occur in children with head injury, although the exact mechanism awaits further evaluation.