Prediction of postoperative hypokalemia in patients with oral cancer undergoing en bloc cancer resection: a retrospective cohort study

Abstract

Background: The factors associated with postoperative hypokalemia in patients with oral cancer remain unclear. We determined the preoperative factors associated with postoperative hypokalemia in patients with oral cancer following en bloc cancer resection and established a nomogram for postoperative hypokalemia prediction.

Methods: Data from 381 patients with oral cancer who underwent en bloc cancer resection were retrospectively analyzed. Univariate and multivariate analyses were performed to identify the risk factors for postoperative hypokalemia. We used receiver operating characteristic (ROC) curves to quantify the factors' effectiveness. A nomogram was created to show each predictor's relative weight and the likelihood of postoperative hypokalemia development. The multinomial regression model's effectiveness was also evaluated.

Results: Preoperative factors, including sex, preoperative serum potassium level, and preoperative platelet-to-lymphocyte ratio (PLR), were significantly associated with postoperative hypokalemia. Based on the ROC curve, the preoperative serum potassium and PLR cut-off levels were 3.98 mmol/L and 117, respectively. Further multivariate analysis indicated that female sex, preoperative serum potassium level < 3.98 mmol/L, and preoperative PLR ≥ 117 were independently associated with postoperative hypokalemia. We constructed a predictive nomogram with all these factors for the risk of postoperative hypokalemia with good discrimination and internal validation.

Conclusions: The predictive nomogram for postoperative hypokalemia risk constructed with these factors had good discrimination and internal validation. The developed nomogram will add value to these independent risk factors that can be identified at admission in order to predict postoperative hypokalemia.

Keywords: Nomogram; Oral cancer; Platelet-to-lymphocyte ratio; Postoperative complication; Postoperative hypokalemia.

Fig. 1

ROC curve for preoperative serum potassium levels and preoperative PLR as risk predictors of postoperative hypokalemia in patients who underwent en-bloc oral cancer resection. Abbreviation: PLR: platelet-to lymphocyte ratio

Fig. 2

Nomogram to predict the risk of postoperative hypokalemia: to estimate the probability of postoperative hypokalemia of patients with oral cancer who underwent en-bloc resection, the “Total Point” is calculated by summing the respective “Points” values corresponding to each variable. Using this “Total Point”, patients’ probability of postoperative hypokalemia can be predicted according to the scale shown in row 7. Abbreviation: PSPL: preoperative serum potassium level (mmol/L); PPLR: preoperative platelet-to-lymphocyte ratio

Fig. 3

Receiver operating characteristic (ROC) curve and calibration plot for model-development and validation sets of the present nomogram. a ROC curve for the model-development set of 253 patients. b ROC curve for validation set of 128 patients. c Calibration plot for the model-development set. d Calibration plot for the validation set. The x-axis represents the nomogram-predicted probability and the y-axis represents the observed rate of postoperative hypokalemia. A perfect prediction would correspond to the 45° dashed line