Transient Delayed Hyponatremia After Transsphenoidal Surgery: Attempting to Enlighten the Epidemiology and Management of a Still-Obscure Complication

A Simple Scoring System for Predicting the Risk of Delayed Hyponatremia After Endoscopic Transsphenoidal Surgery for Pituitary Adenomas

BACKGROUND

To identify high-risk patients for delayed postoperative hyponatremia (DPH) early, we constructed a simple and effective scoring system.

METHODS

We retrospectively analyzed 141 consecutive patients who underwent endoscopic transsphenoidal surgery from January 2019 to December 2022. Patients were divided into DPH group and nondelayed postoperative hyponatremia group based on whether hyponatremia occurred after the third postoperative day. Multivariable logistic regression analysis was conducted to determine the predictive factors of DPH, and a simple scoring system was constructed based on these predictors.

RESULTS

Among 141 patients, 36 (25.5%) developed DPH. Multivariable logistic regression analysis showed that age ≥48 years (odds ratio [OR], 3.74; 95% confidence interval [CI], 1.14-12.21; P = 0.029), Knosp grade ≥3 (OR, 5.17; 95% CI, 1.20-22.27; P = 0.027), postoperative hypokalemia within three days (OR, 3.13; 95% CI, 1.05-9.33; P = 0.040), a difference in blood sodium levels between the first and second day after surgery ≥1 mEq/L (OR, 3.65; 95% CI, 1.05-12.77; P = 0.043), and postoperative diabetes insipidus (OR, 3.57; 95% CI, 1.16-10.96; P = 0.026) were independent predictors of DPH.

CONCLUSIONS

This scoring system for predicting DPH has an area under the receiver operating characteristic curve of 0.856 (95% CI, 0.787-0.925), indicating moderate to good predictive value for DPH in our cohort, but further prospective external validation is needed.

Development and external validation of clinical prediction models for pituitary surgery

Introduction

Gross total resection (GTR), Biochemical Remission (BR) and restitution of a priorly disrupted hypothalamus pituitary axis (new improvement, IMP) are important factors in pituitary adenoma (PA) resection surgery. Prediction of these metrics using simple and preoperatively available data might help improve patient care and contribute to a more personalized medicine.

Research question

This study aims to develop machine learning models predicting GTR, BR, and IMP in PA resection surgery, using preoperatively available data.

Material and methods

With data from patients undergoing endoscopic transsphenoidal surgery for PAs machine learning models for prediction of GTR, BR and IMP were developed and externally validated. Development was carried out on a registry from Bologna, Italy while external validation was conducted using patient data from Zurich, Switzerland.

Results

The model development cohort consisted of 1203 patients. GTR was achieved in 207 (17.2%, 945 (78.6%) missing), BR in 173 (14.4%, 992 (82.5%) missing) and IMP in 208 (17.3%, 167 (13.9%) missing) cases. In the external validation cohort 206 patients were included and GTR was achieved in 121 (58.7%, 32 (15.5%) missing), BR in 46 (22.3%, 145 (70.4%) missing) and IMP in 42 (20.4%, 7 (3.4%) missing) cases. The AUC at external validation amounted to 0.72 (95% CI: 0.63-0.80) for GTR, 0.69 (0.52-0.83) for BR, as well as 0.82 (0.76-0.89) for IMP.

Discussion and conclusion

All models showed adequate generalizability, performing similarly in training and external validation, confirming the possible potentials of machine learning in helping to adapt surgical therapy to the individual patient.

Fluid Restriction After Transsphenoidal Surgery for the Prevention of Delayed Hyponatremia: A Systematic Review and Meta-Analysis

OBJECTIVE

Delayed hyponatremia is the primary cause of readmission after transsphenoidal surgery, with a reported incidence of 9% to 30.7%. Studies have failed to identify consistent predictive factors for postoperative hyponatremia; thus, it is difficult to determine patients that are at a high risk. Fluid restriction is one approach for the prevention of hyponatremia. We have performed a meta-analysis and systematic review of the literature to evaluate the impact of fluid restriction on hyponatremia and hospital readmissions.

METHODS

Ovid EMBASE, PubMed, Scopus, and Cochrane were searched from inception to May 2021, using the Population, Intervention, Comparison, Outcome, and Study question format: Do patients who underwent transsphenoidal surgery and followed a postoperative fluid restriction regimen differ in terms of hyponatremia and readmission rates? Studies that implemented fluid restriction and reported hyponatremia and/or readmission rates were included for analysis. Data were pooled by meta-analysis and analyzed using fixed effect and random effect models.

RESULTS

A total of 143 manuscripts representing 103 unique studies were identified, with 5 studies included for analysis, yielding a pooled cohort of 1586 patients: 594 on fluid restriction protocols and 992 control patients. Fluid restriction protocols ranged from 1.0 to 2.5 L and varied in the length time between postoperative days 1 to 15. Patients on fluid restriction had a decreased risk of hyponatremia (risk ratio: 0.34; 95% CI, 0.21-0.57; P < .00001) and readmission due to hyponatremia (risk ratio: 0.24; 95% CI, 0.09-0.63; P = .0038).

CONCLUSION

Postoperative fluid restriction after transsphenoidal surgery represents an effective method for the prevention of hyponatremia and hospital readmission and has the potential to decrease health care costs.

Delayed Hyponatremia Following Surgery for Pituitary Adenomas: An Under-recognized Complication

Background

Delayed hyponatremia is a serious complication seen after pituitary surgery. We document the incidence, presentation, outcome and risk factors for this condition.

Materials and Methods

This was a retrospective study involving 222 patients operated for nonfunctioning pituitary macroadenomas between 2007-2016. Delayed hyponatremia was defined as serum sodium <135 mmol/L, occurring after the third post-operative day. Hyponatremia was categorized as mild (134-130 mmol/L), moderate (129-125 mmol/L) and severe (<125 mmol/L). All patients received intravenous (0.9%) saline, intravenous hydrocortisone and 12g oral salt over 24 hours. Patients with severe hyponatremia were given 3% saline.

Results

Fifty eight patients (26%) developed delayed hyponatremia; thirty (13.5%) had severe hyponatremia. Delayed hyponatremia usually (43.1%) occurred on the seventh post-operative day (range, 3-15 days). Most patients (81%) remained asymptomatic; 11 patients developed vomiting (5), seizures (3), lethargy (1), fever (1) and paralytic ileus (1). One patient developed status epilepticus. Patients who manifest symptoms had lower sodium levels as compared to those who did not have symptoms (mean 117.7 mmol/L vs. 123 mmol/L; P < 0.01). Male gender (P = 0.002) and intra-operative CSF leak (P = 0.003) were risk factors for developing delayed hyponatremia. Other factors like, age, pre-operative cortisol levels, extent of resection and post-operative diabetes insipidus did not correlate with the occurrence of delayed hyponatremia. Patients who maintained their mean serum sodium levels >138 mmol/L (day 1-day 3) were unlikely to develop delayed hyponatremia (sensitivity, 55.2% and specificity, 83.9%), positive predictive value, 63.2% [confidence interval (CI) 48, 76.7%] and negative predictive value, 78.8% (CI 70.6, 85.5%). In most patients (57%) hyponatremia was corrected within 48 hours (h).

Conclusions

We recommend routine serum sodium testing on the seventh post-operative day for all patients undergoing pituitary surgery. Most patients remain asymptomatic and unless they are detected early they can go on to develop serious complications.

An Effective and Practical Fluid Restriction Protocol to Decrease the Risk of Hyponatremia and Readmissions After Transsphenoidal Surgery

BACKGROUND

Delayed hyponatremia is a common complication following transsphenoidal surgery (TSS) of pituitary lesions, which leads to significant patient morbidity, as well as increased hospital costs associated with readmission.

OBJECTIVE

To report the effects of fluid restriction, during a postoperative period of 4 d, to decrease rates and readmissions for hyponatremia in a cohort of patients undergoing TSS.

METHODS

Because of our observed postoperative rates of hyponatremia, we implemented 1000-mL fluid restriction limited to postoperative days (POD) 4 to 8 in consecutive patients undergoing surgery at our center between March 2018 and January 2019. Patients were monitored for the development of hyponatremia and readmissions. We compared outcomes with those of patients who had undergone TSS prior to fluid restriction.

RESULTS

Data from 57 patients who underwent TSS following implementation of fluid restriction were compared to prior patients who underwent TSS without restriction. The rate of hyponatremia in patients (n = 57) prior to fluid restriction was 12.3%. Following implementation of fluid restriction, we had zero cases of hyponatremia or readmissions. We found body mass index to be inversely related to the risk of hyponatremia and readmissions. Furthermore, male gender, follicle stimulating hormone and/or luteinizing hormone staining on pathology, and administration of preoperative and intraoperative glucocorticoids were associated with decreased risk of hyponatremia readmissions.

CONCLUSION

The implementation of 1000-mL fluid restriction between POD 4 and 8 is a highly successful and simple approach to decrease the risk of delayed hyponatremia after TSS.

Incidence and Factors Associated with Postoperative Delayed Hyponatremia after Transsphenoidal Pituitary Surgery: A Meta-Analysis and Systematic Review

INTRODUCTION

Postoperative delayed hyponatremia is a complication associated with transsphenoidal pituitary surgery. Due to a wide spectrum of symptoms, the reported incidence and predictors of postoperative delayed hyponatremia vary among studies, and this deserves to be reviewed systematically.

METHODS

PubMed, EMBASE, and CENTRAL databases were searched until September 1, 2020. Studies were included when (1) the event number of delayed hyponatremia after transsphenoidal pituitary surgery was reported, or (2) the associated factors of such complication were evaluated.

RESULTS

A total of 27 studies were included for meta-analysis. The pooled incidence of overall and symptomatic delayed hyponatremia was 10.5% (95% confidence interval (CI) = 7.4-14.7%) and 5.0% (95% CI = 3.6-6.9%), respectively. No overt variations of the pooled estimates were observed upon subgroups stratified by endoscopic and microscopic procedure, publication year, and patients' age. In addition, 44.3% (95% CI = 29.6-60.2%) of unplanned hospital readmissions within 30 days were caused by delayed hyponatremia. Among the predictors evaluated, older age was the only significant factor associated with increased delayed hyponatremia (odds ratio = 1.16, 95% CI = 1.04-1.29, P = 0.006).

CONCLUSION

This meta-analysis and systematic review evaluated the incidence of postoperative delayed hyponatremia and found it as a major cause of unplanned readmissions after transsphenoidal pituitary surgery. Older patients are more prone to such complications and should be carefully followed. The retrospective nature and heterogeneity among the included studies and the small number of studies used for risk factor evaluation might weaken the corresponding results. Future prospective clinical studies are required to compensate for these limitations.

Feasibility of machine learning based predictive modelling of postoperative hyponatremia after pituitary surgery

PURPOSE

Hyponatremia after pituitary surgery is a frequent finding with potential severe complications and the most common cause for readmission. Several studies have found parameters associated with postoperative hyponatremia, but no reliable specific predictor was described yet. This pilot study evaluates the feasibility of machine learning (ML) algorithms to predict postoperative hyponatremia after resection of pituitary lesions.

METHODS

Retrospective screening of a prospective registry of patients who underwent transsphenoidal surgery for pituitary lesions. Hyponatremia within 30 days after surgery was the primary outcome. Several pre- and intraoperative clinical, procedural and laboratory features were selected to train different ML algorithms. Trained models were compared using common performance metrics. Final model was internally validated on the testing dataset.

RESULTS

From 207 patients included in the study, 44 (22%) showed a hyponatremia within 30 days postoperatively. Hyponatremic measurements peaked directly postoperatively (day 0-1) and around day 7. Bootstrapped performance metrics of different trained ML-models showed largest area under the receiver operating characteristic curve (AUROC) for the boosted generalized linear model (67.1%), followed by the Naïve Bayes classifier (64.6%). The discriminative capability of the final model was assessed by predicting on unseen dataset. Large AUROC (84.3%; 67.0-96.4), sensitivity (81.8%) and specificity (77.5%) with an overall accuracy of 78.4% (66.7-88.2) was reached.

CONCLUSION

Our trained ML-model was able to learn the complex risk factor interactions and showed a high discriminative capability on unseen patient data. In conclusion, ML-methods can predict postoperative hyponatremia and thus potentially reduce morbidity and improve patient safety.

Diabetes insipidus and syndrome of inappropriate antidiuresis (SIADH) after pituitary surgery: incidence and risk factors

Electrolyte disorders are relatively frequent and potentially serious complications after pituitary surgery. Both DI (diabetes insipidus) and SIADH (syndrome of inappropriate antidiuresis) can complicate and prolong hospital and intensive care unit stay, and the latter may even be preventable. We aim to assess the incidence of both electrolyte disorders and their risk factors. From a prospective registry of patients who underwent endoscopic transnasal transsphenoidal surgery (TSS) for pituitary adenoma, patients with postoperative DI and SIADH were identified. Univariable and multivariable statistics were carried out to identify factors independently associated with the occurrence of either DI or SIADH. A total of 174 patients were included, of which 73 (42%) were female. Mean age was 54 years (range 20-88). During postoperative hospital stay, 13 (7.5%) patients presenting with DI and 11 (6.3%) with SIADH were identified. Patients who developed DI after surgery had significantly longer hospital stays (p = 0.022), as did those who developed SIADH (p = 0.002). Four (2.3%) patients were discharged with a diagnosis of persistent DI, and 2 (1.1%) with the diagnosis of SIADH. At the last follow-up, 5 (2.9%) patients presented with persistent DI, while none of the patients suffered from SIADH. Younger age (odds ratio (OR) 0.97, 95% confidence interval (CI) 0.94-1.01, p = 0.166) and pituitary apoplexy (OR 2.69, 95% CI 0.53-10.65, p = 0.184) were weakly associated with the occurrence of DI. We identified younger age (OR 0.96, 95% CI 0.92-0.99, p = 0.045) and lower preoperative serum sodium (OR 0.83, 95% CI 0.71-0.95, p = 0.008) as independent risk factors for SIADH. Although we found a weak association among age, pituitary apoplexy, and the occurrence of DI, no independent predictor was identified for DI. For postoperative SIADH however, lower age and preoperative serum sodium were identified as significant predictors. None of these findings were sufficiently supported by preexisting literature. Both electrolyte disorders are exquisitely hard to predict preoperatively, and further research into their early detection and prevention is warranted.

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) and Subsequent Central Diabetes Insipidus: A Rare Presentation of Pituitary Apoplexy

Pituitary apoplexy (PA) is a rare endocrine emergency that occasionally presents with sodium disturbances. Here we present a rare case with a previously healthy 41-year-old female who presented with acute onset headache and nausea without visual impairment or overt pituitary dysfunction. Plasma sodium concentrations declined abruptly during the first two days of admission to a nadir of 111 mmol/l. Urine and blood chemistry were consistent with syndrome of inappropriate antidiuretic hormone secretion (SIADH). Magnetic resonance imaging revealed recent bleeding into a pituitary cystic process. Hyponatremia was successfully corrected with fluid restriction and both visual function and anterior pituitary function remained intact. Subsequently, the patient developed central diabetes insipidus (CDI), which responded well to desmopressin substitution. To our knowledge, this is the first case of PA presenting predominantly with posterior pituitary dysfunction that transitioned from SIADH to permanent CDI.