Value of Intracranial Pressure Monitoring in TBI Questioned

Megan Brooks

December 12, 2012

Results of a study published today question the cornerstone of care for patients with severe traumatic brain injury (TBI): intracranial pressure monitoring (ICP).

The trial found that care focused on maintaining monitored ICP at or below 20 mm Hg (as guidelines recommend) in order to avoid poor outcome was not superior to care based on serial computed tomography (CT) and neurologic clinical examination.

"Unfortunately, this study strongly demonstrates that we don't have our current approach right, but it doesn't provide a therapeutic response in terms of a new analytic pathway or treatment algorithm," Randall M. Chesnut, MD, Integra Endowed Professor of Neurotrauma, Department of Neurological Surgery, Harborview Medical Center, University of Washington, Seattle, told Medscape Medical News.

"Many of us," he added, "have suspected for some time that we were following far too simplistic an approach and have individually developed methods of using multiple monitors (multimodality monitoring) to fine tune and individualize treatment variables such as ICP (rather than simply accepting a treatment threshold of 20 mm Hg)."

"Since the treatments that we use to lower ICP all have associated toxicities, some severe, titrating the treatment threshold to the patient and the immediate situation attempts to minimize the risks of treatment without under treating," Dr. Chesnut said.

The study was published December 12 in the New England Journal of Medicine .

Clinical Signs Suitable

In a linked editorial, Allan H. Ropper, MD, Department of Neurology, Brigham and Women's Hospital, Boston, Massachusetts, notes that physiologic measurements are "inherently more appealing than clinical signs because they give the impression of precision and of proximity to disease."

"We are still likely to continue to doubt clinical signs, which indeed do not reflect global pressure inside the cranium," he writes, "but stupor, coma, posturing, and dilatation of the pupils indicate compression of the midbrain, and according to this study they are very suitable observations to use in directing treatment."

Although ICP monitoring is widely recognized as standard of care for patients with TBI, its use in guiding therapy has "incomplete acceptance," even in high-income countries, Dr. Chesnut and colleagues point out in their paper. Multiple versions of guidelines acknowledge that there is inadequate evidence of efficacy and call for randomized trials, while at the same time noting that there would be ethical issues of having a control group go without ICP monitoring.

The identification of a group of intensivists in Latin America who routinely managed severe TBI without using available ICP monitors and who had a balanced view of the value of ICP monitoring eliminated the ethical constraints and led to the current trial now reported, they say.

A total of 324 patients with severe TBI treated in intensive care units (ICUs) in Bolivia or Ecuador were randomly assigned to management based on ICP monitoring or management based on serial CT imaging and clinical examination (ICE). Intraparenchymal monitoring was chosen for its accuracy, ease of insertion, safety profile, and low maintenance requirements, the authors say.

The primary outcome was a composite of survival time, impaired consciousness, and functional status at 3 and 6 months and neuropsychological status at 6 months. This composite measure was based on performance across 21 measures of functional and cognitive status and was calculated as a percentile (with 0 indicating the worst and 100 the best performance).

Outcomes Similar

According to the investigators, there was no significant between-group difference in the primary outcome, with a score of 56 in the ICP group and 53 in the ICE group (P = .49).

Mortality at 6 months was also similar: 39% in the ICP group and 41% in the ICE group (P = .60).

The median length of ICU stay was also similar in the 2 groups (P = .25), although the number of days of brain-specific treatments administered in the ICU (hyperosmolar fluids and hyperventilation) was lower in the ICP group than in the ICE group (3.4 vs 4.8; P = .002). The distribution of serious adverse events was similar in both groups.

These results, the investigators say, "do not support the superiority" of treatment based on ICP monitoring over treatment guided by neurologic testing and serial CT imaging in improving short-term and long-term recovery in the general population of patients with severe TBI. However, they say it's possible the specific ICE protocol used in the study provided superior control of ICP.

"Although we showed no outcome difference between monitor-driven and ICE approaches, the qualitative nature of the ICE approach and the increased treatment efficiency that we found associated with ICP monitoring should not change the usage of ICP monitoring in areas where this resource is available," Dr. Chesnut told Medscape Medical News.

"Notably, however, for those patients treated in areas where ICP monitoring is not available, this study has provided the only published algorithm for management that has been demonstrated to result in successful management. Indeed, as likely > 95% of the world's brain injury patients are treated under such conditions, this alternate view of our results may indeed be one of the most important aspects of this study," he said.

Anticipated Objections

In his editorial, Dr. Ropper says several objections to the study are "easily anticipated," such as its locale, South America, which has ICU protocols that differ from those in North America and Europe.

The use of intraparenchymal monitors may be another "reservation." These monitors, unlike the external ventricular drains used in many ICUs, do not allow drainage of spinal fluid to reduce pressure. "But this technical difference is not enough to negate the conclusions of the study, since the measurements produced by each method are reasonably close," Dr. Ropper writes.

Another reservation may be the composite end point in the trial, which was "contrived," he points out. However, the finding of similar mortality at 14 and 30 days whether ICP was monitored or not "supports the conclusion that measurement makes little difference in terms of reducing the early damage caused by elevated [ICP]."

In their paper, Dr. Chesnut and colleagues emphasize that the value of knowing the precise ICP is not challenged by this study, nor is the value of aggressively treating severe TBI questioned.

"Rather our data suggest that a reassessment of the role of manipulating monitored [ICP] as part of multimodality monitoring and targeted treatment of severe [TBI] is in order."

The study was funded by the National Institutes of Health and the Fogarty International Center, the National Institute of Neurological Disorders and Stroke, and Integra Life Sciences. Disclosures for the study team and Dr. Ropper are available at www.NEJM.org.

N Engl J Med. Published online December 12, 2012. Abstract Editorial

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