Is POSSUM predictive of morbidity and mortality in laryngectomy patients?
Introduction
The outcome of any surgical procedure, whether successful or not, is not necessarily solely related to the abilities of the individual surgeon, but is a result of a multitude of interrelated and interacting variables relating to host, pathology and operator. Comparison of raw mortality and morbidity rates between units do not reflect these variables and thus the value of comparison of such data in isolation is questionable.
Unfortunately, in the light of the professional misconduct case at Bristol [1] such focus on comparisons, especially on outcomes in oncological surgery, is becoming commonplace. Units serving areas of greater wealth and higher social class will automatically be presented with a better educated patient group who, as a consequence, are less likely to partake of detrimental lifestyle habits and therefore be, amongst other things, better nourished; just one important factor of many which may have profound influence on both morbidity and mortality following surgery. More concerning may be the subliminal, or in some cases explicit, institutional pressure experienced by individual surgeons to select only low-risk cases in order to achieve a low mortality rate.
With this in mind, during the 1980s, following multivariate discriminant analysis of numerous peri-operative variables, a scoring system was developed to predict 30-day mortality and morbidity rates (The POSSUM audit system; Physiological and Operative Severity Score for the Enumeration of Mortality and Morbidity) [2], [3]. This was an attempt to create a tool of assessment of surgical quality that was risk adjusted for the patient's acute and chronic physiological status as well as for the nature of the operation.
This system was principally designed for a population of general surgical patients and there have been numerous subsequent papers validating it in this patient population [4], [5]. It was observed that POSSUM tended to overestimate peri-operative mortality [3], [6]; two-fold in high risk patients and up to seven-fold in low risk patients, with the smallest risk of death being 1.08% in the lowest risk group. Following further logistic regressional analysis of 1485 of their own patients Pytherch et al. readjusted the POSSUM formula for perioperative mortality creating the modified P-POSSUM (Portsmouth POSSUM) [7] resulting in a lowering of the minimal predicted risk of mortality to 0.2%.
Application of both of these scoring systems has been applied to other non-abdominal cavity surgical sites including the head and neck region [8], [9], [10], [11].
The authors present their evaluation of both POSSUM and P-POSSUM in a cohort of consecutive patients undergoing laryngectomy for squamous cell carcinoma of the head and neck (SCCHN) at University Hospital Aintree; a major tertiary referral centre for head and neck cancer in the North West of England. The specific aim of this study was to assess the ability of POSSUM or P-POSSUM to predict the development of post-operative pharyngo-cutaneous fistula formation, length of hospital stay and 30-day mortality in our patient cohort.
Section snippets
Methods
The data relating to patients undergoing surgery in our unit is entered into the Liverpool Head and Neck database. For the purpose of this study, consecutive patients undergoing total laryngectomy between October 2003 and October 2007 were included. The procedures were performed under the care of one of the four ORL-HN surgeons in the Department. All variables enabling calculation of POSSUM and P-POSSUM values for all patients were included in the analysis. Individual POSSUM scores were
Results
From October 2003 to October 2007 a total of 99 patients underwent total laryngectomy, for which 92 complete data sets and 93 POSSUM data sets are available (Table 1).
In all cases primary repair of the pharynx was performed. The pharynx was closed in the same way in all cases; 3 layered closure of mucosa, sub-mucosa and finally inferior constrictors. This method of closure has subsequently been changed within the department since we believe that closure of the inferior constrictors is
Discussion
Audit is now a fundamental obligation of current surgical practice, with a growing emphasis on comparative audit [15]. It plays a key part in maintaining and driving up clinical standards [16]. The POSSUM (Physiological and Operative Severity Score for the Enumeration of Morbidity and mortality) score was developed by Copeland et al. [3] as a tool for comparative audit in General Surgery and has been applied to many other specialities and operative sub-sites, including vascular surgery [17],
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