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NEWS: Variations in ICP After Decompressive Craniectomy Are Associated With Outcomes

By Currents Editor posted 05-14-2018 10:35

  
Authors: Sauvigny T, Göttsche J, Czorligh P, Vettorazzi E, Westphal M, and Regelsberger J.  Intracranial pressure (ICP) in patients undergoing decompressive craniectomy: new perspective on thresholds. J Neurosurgery. March 2018; 128(3): 819-827

Reviewed by: Sara Stern-Nezer, MD, MPH, Assistant Clinical Professor, University of California, Irvine

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Methods

This study investigated the association between ICP and outcome after decompressive hemicraniectomy (DH) in patients with malignant cerebral infarction or TBI. The authors performed a retrospective analysis of patients who underwent unilateral DH for acute SDH in the setting of TBI or MCA infarction; indication for surgical decompression was verified by a senior neurosurgeon and senior neurologist based on current guidelines. Only TBI patients with SDH causing critical mass effect were included to increase comparability. They excluded patients with variable surgical technique (e.g. bifrontal decompression). All patients had ICP monitoring postoperatively which was treated with aggressive medical treatment including avoidance of hypotension and hypoxia; goal CO2 was 35-38mmHg. Hourly ICP and CPP values were analyzed for 168 hours after DH. ICP was measured using intraparenchymal ICP monitor placed ipsilateral to the decompression. Primary outcome was mRS after rehabilitation. Favorable outcome was defined as mRS 0-4. Analysis was done using conditional inference tree analysis and Kaplan Meier survival analysis. Predictive power analysis was done to see whether ICP helped to predict outcome in addition to other standard prognostic factors, including diagnosis, anisocoria and SAPS II score.

Results

102 patients were included in the study (37.3% female, mean age 53.2 years); 57 were stroke patients and 45 TBI patients with acute SDH. Mean follow-up period was 129 days after DH. There were no statistically significant differences in age, gender, GCS, NIHSS, size of decompression severity of illness, presence of EVD or level of sedation. There was also no significant difference between patients who received DH within 48 hours compared to those who had DH more than 48 hours after injury. When comparing ICP over time between the two groups (mRS 0-4 vs mRS 5-6), the ICP values in the good outcome group were consistently lower than the poor outcome group. Mean ICP in the good outcome group was 11.5mmHg compared to 17.5mmHg in the poor outcome group (p<0.001); max ICP was 14mmHg in the good outcome group compared to 25mmHg in the poor outcome group. This difference held true when separately analyzing the patients with MCA infarction (mean ICP 11.7 vs 19.7mmHg in good vs poor outcome respectively, p<0.001) as well as the TBI group (mean ICP 10.9 vs 15.8mmHg in the good vs poor outcome groups respectively, p<0.001). In the predictive power analysis, mean ICP over 12 hours improved prediction of outcome when added to presence of anisocoria and diagnosis (p<0.001); SAPS II did not improve the predictive power of the model. Using their data, the authors calculated 15mmHg as the ICP threshold and using this to define low vs. high ICP groups; Kaplan-Meier method showed a significantly higher survival rate in the low ICP group (p<0.001).

Commentary

This retrospective study showed that in TBI and stroke patients who underwent decompressive hemicraniectomy, ICP values were significantly different between patients who had severe disability or death (mRS 5-6) and those with better outcomes (mRS 0-4). One of the most interesting aspects of this study is that in both groups, mean ICP was less than 20mmHg despite the difference in outcomes. They also demonstrated that elevated ICP is a robust prognostic factor for their defined good and poor outcomes – even within the framework of what we consider a “normal” ICP and thus do not aggressively treat. The significant limitation of this study is that it was a retrospective trial, and thus it is unclear that treatment of ICP in this population could improve outcomes or if it is just a marker of severity of disease. However, the study brings to light the importance of reinvestigating what constitutes a safe ICP threshold in patients who have undergone decompressive hemicraniectomy. #LiteratureWatch #NEWSReview #SaraStern-Nezer
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