POSSUM, a Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity was first proposed in 1991 by Copeland et al as a simple scoring system for general use in surgery as a risk indicator of mortality and morbidity.
Scores are allocated to twelve physiological variables measured on admission and six to the patient’s operative procedure. Two totals, preoperative and operative, are then applied to the Possum algorithm to calculate morbidity and mortality rates. In this way, patient data can be standardised so that patient outcomes can be compared irrespective of differing patterns of referral and population.
A followup study in Porstmouth in 1996 refined the algorithm, called P- Possum, to reduce the overprediction of mortality in the group at lowest risk. In a further study comparing Possum with P- Possum in general surgery, P- Possum provided the more accurate in predicting in-hospital mortality.
Possum has since been applied to a number of surgical groups including
orthopaedic, vascular, head & neck and colorectal. Although proving to be a successful audit tool in general surgery, doubts have been raised when predicting mortality at the extremes of age and in high-risk emergency work.
The Possum factors used are:
| Physiological |
Operative |
Age
Cardiac history
Respiratory history
Blood pressure
Pulse rate
Glasgow coma score
Haemoglobin
White cell count
Venous blood urea
Venous blood NA
Venous blood K
Electrocardiogram |
Multiple procedures
Total blood loss
Peritoneal soiling
Malignancy present
Mode of surgery
|
Further reading :
G.P. Copeland, D. Jones, M. Walters : British Journal of Surgery, 1991, vol 78. 356-360
M.S. Whiteley, D.R. Prytherch, B. Higgins, P.C. Weaver, W.G. Prout : British Journal of Surgery, 1996, vol 83. 812-815
D.R. Prytherch , M.S. Whiteley, B. Higgins, P.C. Weaver, W.G. Prout, S.J. Powell : British Journal of Surgery, 1998, vol 85. 1217-1220
L.D. Wijesinghe, T. Mahmood, D.J.A. Scott, D.C. Berridge, P.J. Kent, R.C. Kester : British Journal of Surgery, 1998, vol 85. 209-212
P.P.Tekkis, N.Kessaris, H.M.Kocher, J.D.Poloniecki, J.Lyttle and A.C.J.Windsor: British Journal of Surgery 2003; 90: 340-345
