THE VALUE OF PREOPERATIVE AND OPERATIVE FEATURES IN PREDICTING ELECTROLYTE DERANGEMENTS AFTER TRANSURETHRAL RESECTION OF PROSTATE; A RECEIVER OPERATOR CHARACTERISTIC CURVE ANALYSIS

ABSTRACT
Background: Transurethral resection of prostate (TURP) is one of the commonest urological procedure. Despite tremendous
advancements in the technique itself, electrolyte derangements are common, where as much as one third
of patients develop the TUR-syndrome, resulting in significant morbidity and mortality.
Objective: Our aim was to analyse the predictive value of preoperative and operative features which could be used to
develop a model for estimating the risk of electrolyte derangements following TURP.
Methods: This is a prospective case series study conducted at Urology Unit LRH where we included patients admitted
for TURP between January 2014 and December 2015 (24-months). Record was made of patient age, comorbids,
preoperative electrolytes (sodium/potassium), renal functions (urea/creatinine), procedure time (in minutes) and the
volume of irrigation solution used. All patients were followed postoperatively by determining their electrolytes, renal
functions, symptoms related to electrolytes derangement, early complications related to electrolytes derangements
and mortality attributable to it.
Results: 93 patients were operated during the study period with an overall mean age of 65.16 years ± 5.49 SD. Comorbidities
were present in 31 (33.3%) patients. Hypertension was the commonest comorbidity which was present in
18 (19.4%) patients. The overall preoperative mean serum sodium was 137.57 mmol/L ± 3.94 SD and mean serum
potassium was 4.26 mmol/L ± 0.44 SD. Overall mean postoperative serum sodium was 134.63 mmol/L ± 4.45 SD,
mean potassium was 4.17 mmol/L ± 0.41 SD. Overall length of stay was 2.59 days ± 0.92 SD with a mortality rate of
1.1%. In multivariate logistic regression analysis, the overall predictive value of comorbids, preop serum Na+, K+ and
procedure length was determined. Sensitivity was 84.0%, specificity was 92.6%, positive predictive value was 80.7%
and negative predictive value was 94.02%.
Conclusions: Preoperative presence of comorbids, preop serum Na+ & K+ and intraoperative procedure time and total
volume of irrigating solution used are highly predictive of postoperative electrolyte derangements. Significant morbidity
and mortality can be prevented if these factors are considered, particularly in a combined model.
Key Words: Benign prostatic hyperplasia, Transurethral resection of prostate, TUR-syndrome, preoperative prediction.