Clinical study
Intraoperative applications of intracranial pressure monitoring in patients with severe head injury

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Abstract

From December 2002 to January 2004, 30 patients (20 men and 10 women; mean age 36.8 years [±14.9 years]) with preoperative Glasgow Coma Scale scores of 8 or less underwent emergency haematoma evacuation surgery and continuous intracranial pressure (ICP), cerebral perfusion pressure (CPP) and mean arterial blood pressure monitoring to determine ICP and CPP thresholds to predict patient outcomes. Receiver-operating characteristic (ROC) curves were plotted. Using the ROC curve, the diagnostic accuracy is given by the area under the curve and at the point on the curve farthest from the diagonal, which indicates the threshold value. The results showed that the initial ICP for unfavourable outcomes was 47.4 ± 21.4 mmHg, resulting in a CPP of 22.8 ± 12.83 mmHg. The initial ICP for favourable outcomes was 26.4 ± 10.1 mmHg, resulting in a CPP of 48.8 ± 13.4 mmHg. The CPP had the largest area under the ROC curve in all stages of the operation, corresponding to intraoperative CPP thresholds of 37 mmHg (initial), 51.8 mmHg (intraoperative) and 52 mmHg (after scalp closure). The ROC curve analysis showed that CPP was a better predictor of outcome than ICP.

Introduction

The optimal cerebral perfusion pressure (CPP) in severe head injury is still controversial. In 2000, Juul et al. indicated that a CPP of greater than 60 mmHg appeared to have little influence on the outcome of patients with severe head injury.1 In 2000, recommendations from the Brain Trauma Foundation advocated raising CPP to at least 70 mmHg.2 In 2003, Nordstrom et al. suggested that CPP may be reduced to 50 mmHg in patients with severe traumatic brain lesions.3 However, in most of this literature, data were recorded postoperatively.[1], [2], [3], [4], [5], [6], [7], [8], [9] Continuous recordings of intracranial pressure (ICP) and CPP values during surgery were not included.10

The receiver-operating characteristic (ROC) curve is a tool to evaluate the benefits of a procedure or to compare one procedure with another. Using the ROC curve, the diagnostic accuracy of a test is given by the area under the ROC curve and at the point on the curve farthest from the diagonal, which indicates the threshold value.[11], [12] The purposes of this study were to establish the early values of ICP and CPP which may be better predictors of outcome and to determine the thresholds of ICP and CPP during surgery that were predictive of outcome, using ROC curves.

Section snippets

Materials and methods

Patients with isolated brain injury with acute subdural haemorrhage (SDH) and/or epidural haemorrhage (EDH) or intracerebral haemorrhage (ICH) and preoperative Glasgow Coma Scale (GCS) scores of ⩽8 were admitted to the Neurosurgical Intensive Care Unit of Chi-Mei Medical Center, Taiwan. All patients underwent emergency craniectomy for haematoma removal. They received anaesthesia induction with fentanyl, propofol, xylocaine and atracurium and general anaesthesia with desflurane. Desflurane

Results

The mean age of the 30 patients (20 male and 10 female) was 36.8 ± 14.9 years (range, 20–61 years). There was a significant predominance of male patients (66.7%). The primary lesions included acute SDH in 22, ICH in six and EDH in two patients. The mean preoperative GCS score was 6.5 ± 1.1. The admission and preoperative GCS scores were significantly lower in patients with a GOS of 1–3. Patients with preoperatively reactive pupils had favourable outcomes. Midline shift on brain CT scan was not a

Discussion

The early values of ICP and CPP during neurosurgery for severe head injury are not well studied. This is primarily because the surgical team is concerned with the rapid removal of the haematoma, rather than placement of monitoring devices before clot evacuation. Of the ICP monitors placed intraoperatively, most are placed at the end of the surgery, and the first ICP measurement is not taken until after scalp closure or on arrival in the intensive care unit. However, the presence of an ICP

Conclusions

We conclude that the initial ICP may be higher than suspected and CPP very low in patients with severe head injury, particularly those with unfavourable outcomes. Removal of the skull flap at surgery results in a significant reduction in ICP, which is further decreased by opening the dura and evacuating the haematoma. Simultaneously, the CPP increased stepwise. Based on ROC curve analyses, CPP is a better predictor of outcome than ICP. Our measured intraoperative CPP thresholds (initial of 37

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