P-POSSUM scoring system for mortality prediction in general neurosurgery

The Physiological and Operative Severity Score for enUmeration of Mortality and morbidity (POSSUM) scoring systems have been designed for comparative audit and have been well validated in general and vascular surgery. The Portsmouth predictor equation (P-POSSUM) was highly predictive of mortality in a study of elective craniotomies for neurosurgery but has yet to be validated in spinal, peripheral nerve or acute cranial neurosurgery. The West Australian Categorisation of Operative Severity (WA classification) was created for all neurosurgical procedures. Case notes and laboratory results of 531 consecutive patients undergoing neurosurgery were reviewed retrospectively. All POSSUM variables were collected and the POSSUM and P-POSSUM mortality equations were applied. The observed mortality rate was 4.52% and the WA P-POSSUM predicted mortality rate was 4.58% (p>0.951). The WA P-POSSUM rate was more predictive than either the WA POSSUM rate (10.9%, p<0.0001) or the previously proposed elective craniotomy P-POSSUM classification (5.8%, p<0.198). We concluded that the P-POSSUM model with WA classification has the potential to be used in mortality audits for general neurosurgery. By quantifying preoperative risk, P-POSSUM might provide a useful denominator to observed death rates for meaningful comparison of individual neurosurgeons and between departments.