Factors predicting postoperative hyponatremia and efficacy of hyponatremia management strategies after more than 1000 pituitary operations

Gender potentially affects early postoperative hyponatremia in pituitary adenoma: XGBoost-based predictive modeling

Purpose

The occurrence of hyponatremia is a prevalent complication following transnasal transsphenoidal surgery for pituitary adenoma surgery, which adversely affects patient prognosis, hospitalization duration, and rehospitalization risk. The primary objective of this study is to strengthen the correlation between clinical factors associated with pituitary adenoma and postoperative hyponatremia. Additionally, the study aims to develop a predictive model for postoperative hyponatremia in patients with pituitary adenoma, with the ultimate goal of establishing a basis for reducing the occurrence of postoperative hyponatremia following surgical interventions.

Methods

The chi-square test or Fisher test was employed for nominal data, while the t-test or Mann-Whitney test was utilized for continuous data analysis. In cases where the data exhibited statistical differences, binary logistic analysis was conducted to examine the risk and protective factors associated with postoperative hyponatremia. XGBoost was employed to construct predictive models for hyponatremia in this study. The patients were partitioned into training and test sets, and the most suitable parameters were determined through five-fold cross-validation and subsequently utilized for training on the training set. The discriminatory capability was assessed on the internal validation set.

Results and conclusions

Out of the total 280 patients included in this investigation, 82 patients experienced early postoperative hyponatremia. Among these individuals, male gender (P = 0.02, odds ratio = 1.98) was identified as a risk factor for early postoperative hyponatremia, while preoperative chloride levels (P = 0.021, odds ratio = 0.866) and surgery time (P = 0.039, odds ratio = 0.990) were identified as protective factors against postoperative hyponatremia. The XGBoost model exhibited a sensitivity of 94.2%, a specificity of 61.5%, a positive predictive value of 51.6%, a negative predictive value of 96%, and identified male gender, preoperative sodium, and preoperative cortisol as the most significant predictors. Our findings indicate that gender may have influence in the development of early postoperative hyponatremia in patients with pituitary adenomas.

Association between postoperative changes in natremia and outcomes in patients undergoing elective craniotomy

Postoperative dysnatremias, characterized by imbalances in serum sodium levels, have been linked to increased resource utilization and mortality in surgical and intensive care patients. The management of dysnatremias may involve medical interventions based on changes in sodium levels. In this study, we aimed to investigate the impact of postoperative changes in natremia on outcomes specifically in patients undergoing craniotomy.We conducted a retrospective analysis of patient records from the Department of Neurosurgery at West China Hospital, Sichuan University, covering the period from January 2011 to March 2021. We compared the highest and lowest sodium values in the first 14 postoperative days with the baseline values to define four categories for analysis: no change < 5 mmol/L; decrease > 5 mmol/L; increase > 5 mmol/L; both increase and decrease > 5 mmol/L. The primary outcome measure was 30-day mortality.A total of 12,713 patients were included in the study, and the overall postoperative mortality rate at 30 days was 2.1% (264 patients). The increase in sodium levels carried a particularly high risk, with a tenfold increase (OR 10.21; 95% CI 7.25-14.39) compared to patients with minimal or no change. Decreases in sodium levels were associated with an increase in mortality (OR 1.60; 95% CI 1.11-2.23).Moreover, the study revealed that postoperative sodium decrease was correlated with various complications, such as deep venous thrombosis, pneumonia, intracranial infection, urinary infection, seizures, myocardial infarction, and prolonged hospital length of stay. On the other hand, postoperative sodium increases were associated with acute kidney injury, deep venous thrombosis, pneumonia, intracranial infection, urinary infection, surgical site infection, seizures, myocardial infarction, and prolonged hospital length of stay.Changes in postoperative sodium levels were associated with increased complications, prolonged length of hospital stay, and 30-day mortality. Moreover, the severity of sodium change values correlated with higher mortality rates.

A Conspectus of Euvolemic Hyponatremia, Its Various Etiologies, and Treatment Modalities: A Comprehensive Review of the Literature

Hyponatremia is the most prevalent electrolyte imbalance encountered among hospitalized patients, athletes, the elderly, patients with chronic ailments, postoperative patients, and a few asymptomatic individuals. Clinical manifestations of hyponatremia can be diverse, with characteristic neurological symptoms. Depending on in-depth medical history, physical examination (including volume status assessment), laboratory investigation, and drug history, patients can be classified broadly as undergoing hypervolemic, euvolemic, or hypovolemic hyponatremia. However, patients with hypervolemic hyponatremia often present with distinctive signs such as edema or ascites, and the clinical presentation of hypovolemic and euvolemic hyponatremia poses significant challenges for clinicians. The convolution in clinical manifestations of patients is due to the varied etiologies of euvolemic hyponatremia, such as syndrome of inappropriate antidiuretic hormone secretion (SIADH), adrenocortical insufficiency, hypothyroidism, psychogenic polydipsia, different classes of drugs (chemotherapeutics, antipsychotics, antidepressants), endurance exercise events, and reset osmostat syndrome (ROS). The management of hyponatremia depends on the rate of hyponatremia onset, duration, severity of symptoms, levels of serum sodium, and underlying comorbidities. Over the last decade, the clinical understanding of hyponatremia has been scattered due to the introduction of innovative laboratory markers and new drugs. This article will be a conspectus of all the recent advancements in the field of diagnosis, investigations, management, and associations of hyponatremia, along with traditional clinical practices. Subsequently, a holistic overview has been laid out for the clinicians to better understand and identify knowledge deficiencies on this topic.

Fluid Restriction Reduces Delayed Hyponatremia and Hospital Readmissions After Transsphenoidal Surgery

CONTEXT

Postoperative hyponatremia leads to prolonged hospital length of stay and readmission within 30 days.

OBJECTIVE

To assess 3 strategies for reducing rates of postoperative hyponatremia and analyze risk factors for hyponatremia.

DESIGN

Two retrospective analyses and 1 prospective study.

SETTING

Tertiary referral hospital.

PATIENTS

Patients undergoing transsphenoidal surgery for pituitary adenomas and other sellar and parasellar pathologies.

INTERVENTION(S)

Phase 1: no intervention. Phase 2: postoperative day (POD) 7 sodium testing and patient education. Phase 3: fluid restriction to 1 L/day on discharge in addition to phase 2 interventions.

MAIN OUTCOME MEASURES

Rates of early and delayed hyponatremia and readmissions. Secondary outcomes were risk factors for hyponatremia and readmission costs.

RESULTS

In phase 1, 296 patients underwent transsphenoidal surgery. Twenty percent developed early and 28% delayed hyponatremia. Thirty-eight percent underwent POD 7 sodium testing. Readmission rates were 15% overall and 4.3% for hyponatremia. In phase 2 (n = 316), 22% developed early and 25% delayed hyponatremia. Eighty-nine percent complied with POD 7 sodium testing. Readmissions were unchanged although severity of hyponatremia was reduced by 60%. In phase 3 (n = 110), delayed hyponatremia was reduced 2-fold [12.7%, relative risk (RR) = 0.52] and readmissions 3-fold [4.6%, RR = 0.30 (0.12-0.73)]; readmissions for hyponatremia were markedly reduced. Hyponatremia readmission increased costs by 30%.

CONCLUSIONS

Restricting fluid to 1 L/day on discharge decreases rates of delayed hyponatremia and readmissions by 50%. Standardized patient education and POD 7 sodium testing decreases severity of hyponatremia but does not impact readmission rates. These protocols should be considered standard practice for patients undergoing transsphenoidal surgery.

Predictors of Delayed Hyponatraemia After Surgery for Pituitary Tumour

Delayed hyponatraemia(DH) is a common complication following trans-sphenoidal surgery(TSS) for pituitary tumour. We evaluated the prevalence of DH following TSS, and assessed the factors associated with DH, including early post-operative diabetes insipidus(EPDI). This retrospective study included 100 TSS for pituitary tumours in 98 patients, over a period of 26 months. Subjects were divided into two groups: those who developed hyponatraemia and those who did not develop hyponatraemia, during post-operative days 4 to 14. The clinical characteristics and peri-operative parameters were compared between the two groups, to identify factors predicting DH. The mean age of the patients was 42.0±13.6 years, 58 (59%) were females and 61 (61%) had functional tumours. Thirty-six patients(36%) developed DH following TSS of whom majority(58%) were diagnosed on post-operative days 7 and 8; only 8/36 (22%) were symptomatic. Syndrome of inappropriate antidiuretic hormone secretion(SIADH) was found to be the most common aetiology of DH. On logistic regression analysis, intra-operative cerebrospinal fluid(CSF) leak (OR 5.0; 95% CI 1.9-13.8; p=0.002), EPDI (OR 3.4; 95% CI 1.3-9.2; p=0.015) and peri-operative steroid use (OR 3.6; 95% CI 1.3-9.8; p=0.014) were found to be significantly associated with DH. In conclusion, EPDI, intra-operative CSF leak and peri-operative steroid use were significant predictors of DH. EPDI predicts moderate to severe hyponatraemia with 80% specificity but has low sensitivity(47%). As most patients have asymptomatic hyponatraemia, serum sodium measurement on POD 7 to 10 would be helpful to identify DH in patients at increased risk.

The Potential of Self-Assessment and Associated Factors for Delayed Symptomatic Hyponatremia Following Transsphenoidal Surgery: A Single Center Experience

(1) Background: We identified screening parameters and associated factors for delayed, symptomatic hyponatremia (DSH) following inpatient discharge after transsphenoidal surgery (TSS). (2) Methods: In this prospective, monocentric study, 108 patients who underwent TSS for pituitary pathologies were included, provided with a questionnaire and instructed to document urine specific gravity, fluid intake/urine output, body weight and clinical symptoms for every of five days following discharge from hospital. (3) Results: The overall incidence of DSH within 14 days following discharge from the hospital was 14.8% (n = 9). Symptomatic patients presented on average 8.6 days after surgery. Mild DSH was present in 3.3% of the patients, moderate in 1.6% and severe hyponatremia in 9.8% of patients. Female sex (p = 0.02) and lower BMI (p = 0.02), as well as nausea (66.7%; p < 0.01) and emesis (33.3%; p < 0.05), were associated with DSH. A significant weight delta between morning and afternoon weight two days before the event of DSH between both groups (1.26 kg (n = 5) vs. 0.79 kg (n = 52), p < 0.05) was detected. (4) Conclusions: Handing out a symptom questionnaire at discharge seems to be an easy and feasible tool for the detection of DSH after hospital discharge.

Disorders of Salt and Water Balance After Pituitary Surgery

Transsphenoidal surgery is the first-line treatment for many clinically significant pituitary tumors and sellar lesions. Although complication rates are low when performed at high-volume centers, disorders of salt and water balance are relatively common postoperatively. Both, or either, central diabetes insipidus (recently renamed arginine vasopressin deficiency - AVP-D), caused by a deficiency in production and/or secretion of arginine vasopressin, and hyponatremia, most commonly secondary to the syndrome of inappropriate antidiuresis, may occur. These conditions can extend hospital stay and increase the risk of readmission. This article discusses common presentations of salt and water balance disorders following pituitary surgery, the pathophysiology of these conditions, and their diagnosis and management.

Multidisciplinary Postoperative Care Pathway to Reduce Readmissions following Endoscopic Transsphenoidal Pituitary Surgery: Improving Quality of Patient Care

Background  Thirty-day unplanned readmission following endoscopic transsphenoidal pituitary surgery (ETPS) occurs in up to 14% of patients. Delayed hyponatremia is one of the most common causes, accounting for 30% of readmissions and often occurs within 1 week of surgery. The authors' prior retrospective review identified endocrinology follow-up as protective factor. Objectives  Implementation of a multidisciplinary postoperative care (POC) pathway: (1) to reduce 30-day hospital readmissions following ETPS and (2) improve inpatient and outpatient coordination of care with endocrinologist. Methods  This study is a single institution temporal cohort study of patients prior to (control cohort) and after implementation of the POC pathway (intervention cohort). The POC pathway utilized postdischarge 1 to 1.5 L/d fluid restriction, postoperative days 5 to 7 serum sodium, and endocrinology follow-up within 1 week of discharge to stratify patients into tiered hyponatremia regimens. Results  A total of 542 patients were included in the study, 409 (75%) in the control cohort and 133 (25%) in the intervention cohort. All-cause readmission was significantly reduced following implementation of the POC pathway (14 vs. 6%, p  = 0.015). Coordination with endocrinologist significantly increased in the inpatient (96 vs. 83%, p  < 0.001) and outpatient (77 vs. 68%, p  = 0.042) settings. Patients who were not in the POC pathway had the highest risk of readmission (odds ratio: 2.5; 95% confidence interval: 1.1-5.5). Conclusion  A multidisciplinary POC pathway incorporating endocrinologist in conjunction with postdischarge weight-based fluid restriction and postoperative serum sodium levels can safely be used to reduce 30-day readmissions following ETPS.

Impact of surgical factors on delayed hyponatremia in patients with nonfunctioning pituitary adenoma after endonasal endoscopic transsphenoidal procedure

PURPOSE

Delayed hyponatremia can occur after pituitary surgery, resulting in prolonged hospitalization. However, the influence of surgical factors after such a procedure has not been well established. The impact of surgery and related factors on delayed hyponatremia was investigated.

METHODS

This was a retrospective analysis of 137 consecutive patients who underwent transsphenoidal surgery for a nonfunctioning pituitary adenoma between 2008 and 2019. Preoperative (demographics, comorbidities), intraoperative (resection extent, operation time, blood loss volume, cerebrospinal fluid leak, tumor consistency), and postoperative [hematoma, meningitis, diabetes insipidus (DI), hormonal assessment] data were collected, with statistical analysis of each factor performed.

RESULTS

Among the 137 patients, delayed hyponatremia occurred in 31 (22.6%). Multivariate analysis revealed that those with hypertension had a significantly higher likelihood of avoiding delayed hyponatremia (p = 0.004). Although no correlations of direct surgical factors with delayed hyponatremia were found, multivariate analysis of indirect surgical factors showed that presence of a firm tumor, transient DI, and meningitis were significantly associated with delayed hyponatremia (p = 0.014, 0.001, and 0.047, respectively). There was also a significant association of severe hyponatremia with appearance of symptoms (p = 0.002).

CONCLUSION

There was a tendency for hypertension to be associated with delayed hyponatremia avoidance, with indirect surgical factors including tumor consistency, transient DI, and meningitis found to have an influence on delayed hyponatremia. It was concluded that attention should be given to non-hypertensive patients with a firm tumor, transient DI, or meningitis after pituitary surgery, as delayed hyponatremia may occur.

Effect of vasopressin V2-receptor antagonist tolvaptan on syndrome of inappropriate antidiuresis (SIAD) after transsphenoidal pituitary surgery: recovery of measured osmolality

Background

Delayed hyponatremia after pituitary surgery can be treated with the V2-receptor antagonist, oral tolvaptan. We investigated the pharmacological effect of oral tolvaptan against SIAD in patients with hyponatremia after pituitary surgery.

Methods

Thirty-nine patients with pituitary adenoma treated by endoscopic transsphenoidal surgery developed SIAD according to the major guidelines, and 7 patients (17.9%) were treated with tolvaptan. Tolvaptan was administrated orally half a tablet (3.75 mg) once in the first two cases, and half a tablet twice in the other five cases. Serum osmolality, urinary osmolality, urinary sodium concentration, urinary volume, and serum sodium and potassium concentration were evaluated before administration, and after the last oral administration of tolvaptan. Serum osmolality and urine osmolality were physically measured.

Results

Serum sodium concentration was significantly increased from 132.1 ± 4.0 to 143.0 ± 2.9 mmol/L (mean ± standard deviation, n = 7, P < 0.001). Serum osmolality was significantly increased from 266.3 ± 7.7 to 289.6 ± 6.7 mOsm/kg (n = 7, P < 0.001). Urine osmolality was significantly reduced from 607.1 ± 240.4 to 262.7 ± 115.6 mOsm/kg (n = 7, P = 0.01). Urinary sodium concentration was significantly decreased from 121.3 ± 48.4 to 36.9 ± 35.0 mOsm/kg (n = 7, P = 0.001). Urine output (24-hour including the first administration) was significantly increased from 1384.2 ± 550.7 to 3291.3 ± 1710.9 mL/day (n = 6, P = 0.026).

Conclusions

Oral tolvaptan administration corrects SIAD after pituitary surgery. Hyponatremia after pituitary surgery was confirmed to be due to SIAD.

The management and outcome of hyponatraemia following transsphenoidal surgery: a retrospective observational study

Purpose

Hyponatraemia is a common complication following transsphenoidal surgery. However, there is sparse data on its optimal management and impact on clinical outcomes. The aim of this study was to evaluate the management and outcome of hyponatraemia following transsphenoidal surgery.

Methods

A prospectively maintained database was searched over a 4-year period between January 2016 and December 2019, to identify all patients undergoing transsphenoidal surgery. A retrospective case-note review was performed to extract data on hyponatraemia management and outcome.

Results

Hyponatraemia occurred in 162 patients (162/670; 24.2%) with a median age of 56 years. Female gender and younger age were associated with hyponatraemia, with mean nadir sodium being 128.6 mmol/L on postoperative day 7. Hyponatraemic patients had longer hospital stay than normonatraemic group with nadir sodium being inversely associated with length of stay (p < 0.001). In patients with serum sodium ≤ 132 mmol/L, syndrome of inappropriate antidiuretic hormone secretion (SIADH) was the commonest cause (80/111; 72%). Among 76 patients treated with fluid restriction as a monotherapy, 25 patients (25/76; 32.9%) did not achieve a rise in sodium after 3 days of treatment. Readmission with hyponatraemia occurred in 11 cases (11/162; 6.8%) at a median interval of 9 days after operation.

Conclusion

Hyponatraemia is a relatively common occurrence following transsphenoidal surgery, is associated with longer hospital stay and risk of readmission and the effectiveness of fluid restriction is limited. These findings highlight the need for further studies to better identify and treat high-risk patients, including the use of arginine vasopressin receptor antagonists.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00701-022-05134-9.

Predictive factors for delayed hyponatremia after transsphenoidal surgery in patients with pituitary adenomas

OBJECTIVE

The aim of this study was to evaluate the incidence and duration of delayed hyponatremia and to assess the factors influencing the development of delayed hyponatremia after transsphenoidal surgery (TSS) in pituitary adenomas.

METHODS

We retrospectively analyzed the clinical data of patients with pituitary adenoma who underwent TSS. Univariable and multivariable statistics were carried out to identify factors independently associated with the occurrence of delayed hyponatremia.

RESULTS

Of the 285 patients with pituitary adenoma who underwent microscopic TSS, 44 (15.4%) developed postoperative-delayed hyponatremia and 241 (84.6%) did not. The onset of delayed hyponatremia occurred an average of 5.84 days post-surgery and persisted for an average of 5.36 days. Logistic regression analysis showed the highest risk of delayed hyponatremia in patients with significant change in tumor cavity height (odds ratio (OR), 1.158; 95% CI, 1.062, 1.262; P = 0.001), preoperative hypothalamus-pituitary-thyroid axis hypofunction (OR, 3.112; 95% CI, 1.481, 6.539; P = 0.003), and significant difference in blood sodium levels before and 2 days after TSS (OR, 1.101; 95% CI, 1.005, 1.206; P = 0.039).

CONCLUSIONS

Preoperative hypothyroidism, difference in blood sodium levels before and 2 days after TSS, and the change in tumor cavity height after TSS played important roles in predicting postoperative-delayed hyponatremia onset in patients with pituitary adenomas.

Novel Nomograms to Predict Delayed Hyponatremia After Transsphenoidal Surgery for Pituitary Adenoma

OBJECTIVE

This study aimed to develop a nomogram of clinical variables and magnetic resonance imaging scans to predict delayed hyponatremia after transsphenoidal surgery for pituitary adenoma.

METHODS

Patients who underwent transsphenoidal surgery for pituitary adenoma in Fuzong Clinical Medical College of Fujian Medical University between January 2012 and December 2020 were retrospectively investigated. Medical records, MRI findings, and laboratory examination results were recorded as candidate variable predictors of delayed hyponatremia. A nomogram to predict delayed hyponatremia was formulated based on the multivariable model of risk factors. The predictive accuracy and discriminative ability of the nomogram were assessed using the receiver operating characteristic (ROC) curve, calibration plot, and decision curve analyses. The model underwent prospective validation in three medical centers with patients who underwent transsphenoidal surgery for pituitary adenoma between January 2021 and February 2022.

RESULTS

The model that incorporated the postoperative length of "measurable pituitary stalk," pituitary stalk deviation angle difference, postoperative diabetes insipidus, sinking depth of diaphragma sellae, and blood sodium level on the second postoperative day was developed and presented as the nomogram of the training cohort. The nomogram achieved area under the ROC curve (AUCs) of 0.806 and 0.849 for the training cohort and the testing cohort, respectively, and displayed good calibration. Decision curve analysis showed that the nomogram was clinically useful when the threshold probability was 13-96%.

CONCLUSIONS

We developed a nomogram to evaluate the individualized prediction of delayed hyponatremia after transsphenoidal surgery for pituitary adenomas.

Relationship between postoperative hypothalamic injury and water and sodium disturbance in patients with craniopharyngioma: A retrospective study of 178 cases

OBJECTIVE

To investigate the relationship between postoperative hypothalamo-hypophyseal injury (HHI) and postoperative water and sodium disturbances in patients with craniopharyngioma.

METHODS

The medical records, radiological data, and laboratory results of 178 patients (44 children and 134 adults) who underwent microsurgery for craniopharyngioma in a single center were reviewed. Postoperative HHI was assessed using magnetic resonance imaging. Structural defects of the hypothalamo-hypophyseal system (pituitary, pituitary stalk, floor and lateral wall of the third ventricle) were assessed in four standard T1-weighted images. The defect of each structure was assigned 1 score (0.5 for the unilateral injury of the third ventricle wall), and a HHI score was calculated.

RESULTS

The number of patients with HHI scores of 0-1, 2, 2.5-3, and >3 was 35, 49, 61, and 33, respectively. Diabetes insipidus (DI) worsened in 56 (31.5%) patients with preoperative DI, while 119 (66.9%) patients were diagnosed with new-onset DI. Hypernatremia and hyponatremia developed in 127 (71.3%) and 128 (71.9%) patients after surgery, respectively. Syndrome of inappropriate antidiuresis occurred in 97(54.5%) patients. During hospitalization, hypernatremia recurred in 33 (18.5%) patients and in 54 (35.7%) during follow-up, of which 18 (11.9%) were severe. DI persisted in 140 (78.7%) patients before discharge. No relationship was found between the HHI score and incidence of early DI, hyponatremia, syndrome of inappropriate diuretic hormone, or prolonged DI. Compared with patients with a score of 0-1, those with scores =2.5-3 (OR = 5.289, 95% CI:1.098-25.477, P = 0.038) and >3 (OR = 10.815, 95% CI:2.148-54.457, P = 0.004) had higher risk of developing recurrent hypernatremia. Patients with a score >3 had higher risk of developing severe hypernatremia during hospitalization (OR = 15.487, 95% CI:1.852-129.539, P = 0.011) and at follow-up (OR = 28.637, 95% CI:3.060-267.981, P = 0.003).

CONCLUSIONS

The neuroimaging scoring scale is a simple tool to semi-quantify HHI after surgery. Recurrent and severe hypernatremia should be considered in patients with a high HHI score (>2.5). An HHI score >3 is a potential predictor of adipsic DI development. Preventive efforts should be implemented in the perioperative period to reduce the incidence of potentially catastrophic complications.

Diaphragma sellae sinking can predict the onset of hyponatremia after transsphenoidal surgery for pituitary adenomas

PURPOSE

Sinking of the diaphragma sellae (DS) may stretch the pituitary stalk, which in turn impairs neurohypophyseal function; thus, it may play a role in the development of postoperative hyponatremia. We aimed to assess the factors influencing the development of hyponatremia after transsphenoidal surgery (TSS) for pituitary adenomas and analyze the effect of DS sinking on hyponatremia.

METHODS

After applying the inclusion and exclusion criteria, we retrospectively analyzed the clinical data of patients with pituitary adenoma who underwent TSS. The pituitary gland was scanned using a 3.0-T magnetic resonance imaging, and sagittal and coronal images were acquired. We evaluated the following: preoperative and postoperative hypothalamus‒pituitary‒thyroid axis function, hypothalamus‒pituitary‒adrenal axis function, intra-operative cerebrospinal fluid leaks, diabetes insipidus, hyponatremia, time from the day of surgery to the day of discharge, and time of hyponatremia onset.

RESULTS

Of the 460 patients who had microscopic TSS for pituitary adenoma, 83 experienced postoperative hyponatremia. Hyponatremia occurred approximately 5.25 days postoperatively and persisted for 5.54 days. The lowest average blood sodium level was 123.9 mEq/L, which occurred at 7.49 days after surgery. Logistic regression analysis showed that the risk of hyponatremia was greater for patients with a significant DS sinking depth, a large pituitary stalk deviation angle difference, and a longer postoperative "measurable pituitary stalk". The difference in blood sodium levels between pre-TSS and 2 days post-TSS was also an independent predictor of postoperative hyponatremia onset.

CONCLUSION

DS sinking plays an important role in predicting hyponatremia onset after TSS for pituitary adenomas.

Syndrome of Inappropriate Antidiuretic Hormone Secretion and Trimethoprim-Related Hyponatremia Following Transurethral Bladder Wall Biopsy

Postoperative hyponatremia is common. It results from the physiological antidiuretic hormone (ADH) response to surgery and associated exacerbating factors. Common exacerbating factors include medications, excessive fluid administration, and syndrome of inappropriate antidiuretic hormone (SIADH) secretion. High-dose trimethoprim can cause transient salt-losing nephropathy, resulting in SIADH-like hyponatremia associated with hypovolemia, hyperkalemia, and metabolic acidosis. We present a patient who developed symptoms of vomiting, loss of appetite, fatigue, and abdominal discomfort six days after having a transurethral bladder wall biopsy. He had also started a course of trimethoprim two days prior to the onset of the symptoms. Initial investigations demonstrated severe hyponatremia, concentrated urine, and compensated metabolic acidosis. These results suggested postoperative SIADH possibly exacerbated by trimethoprim-related hyponatremia. Cautious IV normal sodium chloride infusion resulted in a rapid recovery. While raising the awareness of postoperative hyponatremia, this case also highlights the difficulty distinguishing between SIADH and trimethoprim-related hyponatremia.

Routine postoperative fluid restriction to prevent syndrome of inappropriate antidiuretic hormone secretion after transsphenoidal resection of pituitary adenoma

OBJECTIVE

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common problem during the postoperative course after pituitary surgery. Although treatment of this condition is well characterized, prevention strategies are less studied and reported. The authors sought to characterize outcomes and predictive factors of SIADH after implementation of routine postoperative fluid restriction for patients undergoing endoscopic transsphenoidal surgery for pituitary adenoma.

METHODS

In March 2018, routine postoperative fluid restriction to 1000 ml/day for 7 days was instituted for all patients who underwent surgery for pituitary adenoma. These patients were compared with patients who underwent surgery for pituitary adenoma between March 2016 and March 2018, prior to implementation of routine fluid restriction. Patients with preoperative history of diabetes insipidus (DI) or concern for postsurgical DI were excluded. Patients were followed by neuroendocrinologists and neurosurgeons, and sodium levels were checked between 7 and 10 days postoperatively. SIADH was defined by a serum sodium level less than 136 mmol/L, with or without symptoms within 10 days after surgery. Thirty-day readmission was recorded and reviewed to determine underlying reasons.

RESULTS

In total, 82 patients in the fluid-unrestricted cohort and 135 patients in the fluid-restricted cohort were analyzed. The patients in the fluid-restricted cohort had a significantly lower rate of postoperative SIADH than patients in the fluid-unrestricted cohort (5% vs 15%, adjusted OR [95% CI] 0.1 [0.0-0.6], p = 0.01). Higher BMI was associated with lower rate of postoperative SIADH (adjusted OR [95%] 0.9 [0.9-1.0], p = 0.03), whereas female sex was associated with higher rate of SIADH (adjusted OR [95% CI] 3.1 [1.1-9.8], p = 0.03). There was no difference in the 30-day readmission rates between patients in the fluid-unrestricted and fluid-restricted cohorts (4% vs 7%, adjusted OR [95% CI] 0.5 [0-5.1], p = 0.56). Thirty-day readmission was more likely for patients with history of hypertension (adjusted OR [95% CI] 5.7 [1.3-26.3], p = 0.02) and less likely for White patients (adjusted OR [95% CI] 0.3 [0.1-0.9], p = 0.04).

CONCLUSIONS

Routine fluid restriction reduced the rate of SIADH in patients who underwent surgery for pituitary adenoma but was not associated with reduction in 30-day readmission rate.

30-Day Readmissions and Coordination of Care Following Endoscopic Transsphenoidal Pituitary Surgery: Experience with 409 Patients

Objective The study aimed to (1) quantify readmission rates and common causes of readmission following endoscopic transsphenoidal pituitary surgery (ETPS); (2) identify risk factors that may predict readmission within 30 days; (3) assess postoperative care coordination with endocrinology follow-up; and (4) identify patients for whom targeted interventions may reduce 30-day readmissions.

Methods Retrospective quality improvement review of patients with pituitary adenoma who underwent ETPS from December 2010 to 2018 at a single tertiary care center.

Results A total of 409 patients were included in the study, of which 57 (13.9%) were readmitted within 30 days. Hyponatremia was the most common cause of readmission (4.2%) followed by pain/headache (3.9%), cerebrospinal fluid leak (3.4%), epistaxis (2.7%), hypernatremia (1.2%), and adrenal insufficiency (1.2%). Patients with hyponatremia were readmitted significantly earlier than other causes (4.3 ± 2.2 vs. 10.6 ± 10.9 days from discharge, p = 0.032). Readmitted patients had significantly less frequent outpatient follow-up with an endocrinologist than the nonreadmitted cohort (56.1 vs. 70.5%, p = 0.031). Patients who had outpatient follow-up with an endocrinologist were at lower risk of readmission compared with those without (odds ratio: 0.46; 95% confidence interval: 0.24–0.88).

Conclusion Delayed hyponatremia is one of the most common causes of 30-day readmission following ETPS. Postoperative follow-up with an endocrinologist may reduce risk of 30-day readmission following ETPS.

Implications for Clinical Practice A multidisciplinary team incorporating otolaryngologist, neurosurgeons, and endocrinologist may identify patients at risk of 30-day readmissions. Protocols checking serum sodium within 1 week of surgery in conjunction with endocrinologist to tailor fluid restriction may reduce readmissions from delayed hyponatremia.

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.

Tolvaptan in the Management of Acute Euvolemic Hyponatremia After Transsphenoidal Surgery: A Retrospective Single-Center Analysis

INTRODUCTION

Syndrome of inappropriate antidiuresis (SIAD) can be a complication of hypothalamus-pituitary surgery. The use of tolvaptan in this setting is not well established, hence the primary aim of this study was to assess the sodium correction rates attained with tolvaptan compared with standard treatments (fluid restriction and/or hypertonic saline). Furthermore, we compared the length of hospital stay in the two treatment groups and investigated the occurrence of overcorrection and side effects including osmotic demyelination syndrome.

METHODS

We retrospectively reviewed 308 transsphenoidal surgical procedures performed between 2011 and 2019 at our hospital. We selected adult patients who developed post-operative SIAD and recorded sodium monitoring, treatment modalities and outcomes. Correction rates were adjusted based on pre-treatment sodium levels.

RESULTS

Twenty-nine patients (9.4%) developed post-operative SIAD. Tolvaptan was administered to 14 patients (median dose 15 mg). Standard treatments were employed in 14 subjects (fluid restriction n=11, hypertonic saline n=1, fluid restriction and hypertonic saline n=2). Tolvaptan yielded higher adjusted sodium correction rates (12.0 mmolL^-1/24h and 13.4 mmolL^-1/48h) than standard treatments (1.8 mmolL^-1/24h, p<0.001, and 4.5 mmolL^-1/48h, p=0.004, vs. tolvaptan). The correction rate exceeded 10 mmolL^-1/24h or 18 mmolL^-1/48h in 9/14 and 2/14 patients treated with tolvaptan, respectively, and in no patient who received standard treatments. No side effects including osmotic demyelination occurred. Tolvaptan was associated with a shorter hospital stay (11vs.15 days, p=0.01).

CONCLUSIONS

Tolvaptan is more effective than fluid restriction (with or without hypertonic saline) and allows for a shortened hospital stay in patients with SIAD after transsphenoidal surgery. However, its dose and duration should be carefully tailored, and close monitoring is recommended to allow prompt detection of overcorrection.

Delayed Postoperative Hyponatremia Following Endoscopic Transsphenoidal Surgery for Non-Adenomatous Parasellar Tumors

Little is known about delayed postoperative hyponatremia (DPH) accompanied with transsphenoidal surgery for non-adenomatous skull base tumors (NASBTs). Consecutive data on 30 patients with parasellar NASBT was retrospectively reviewed with detailed analyses on perioperative serial sodium levels. Serological DPH (sodium ≤ 135 mmol/L) was observed in eight (27%), with four (13%) of them being symptomatic. DPH developed on postoperative day 7-12 where the mean sodium levels were 134 mmol/L (a mean of 7 mmol/L drop from the baseline) in asymptomatic and 125 mmol/L (a mean of 17.5 mmol/L drop from the baseline) in symptomatic DPH. Serological DPH was accompanied with "weight loss and hemoconcentration (cerebral salt wasting type)" in four (50%), "weight gain and hemodilution (syndrome of inappropriate antidiuretic hormone secretion type)" in three (38%), and no significant weight change in one. Intraoperative extradural retraction of the pituitary gland was the only significant factor for serological DPH (p = 0.035; odds ratio, 12.25 (95% confidence interval, 1.27-118.36)). DPH should be recognized as one of the significant postsurgical complications associated with TSS for NASBTs. Although the underlying mechanism is still controversial, intraoperative extradural compression of the pituitary gland and subsequent dysregulation of the hypothalamo-hypophyseal axis may be responsible.

Readmission after endoscopic transsphenoidal pituitary surgery: analysis of 584 consecutive cases

OBJECTIVE

Hospital readmission is a key component in value-based healthcare models but there are limited data about the 30-day readmission rate after endonasal endoscopic transsphenoidal surgery (EETS) for pituitary adenoma. The objective of this study was to determine the incidence and identify factors associated with 30-day readmission after EETS for pituitary adenoma.

METHODS

The authors analyzed a prospectively acquired database of patients who underwent EETS for pituitary adenoma from 2005 to 2018 at NewYork-Presbyterian Hospital, Weill Cornell Medicine. Clinical, socioeconomic, and radiographic data were reviewed for cases of unplanned readmission within 30 days of surgery and, as a control group, for all other patients in the series who were not readmitted. Statistical significance was determined with an alpha < 0.05 using Pearson's chi-square and Fisher's exact tests for categorical variables and the independent-samples t-test for continuous variables.

RESULTS

Of 584 patients undergoing EETS for pituitary adenoma, 27 (4.6%) had unplanned readmission within 30 days. Most readmissions occurred within the first week after surgery, with a mean time to readmission of 6.6 ± 3.9 days. The majority of readmissions (59%) were for hyponatremia. These patients had a mean sodium level of 120.6 ± 4.6 mEq/L at presentation. Other causes of readmission were epistaxis (11%), spinal headache (11%), sellar hematoma (7.4%), CSF leak (3.7%), nonspecific headache (3.7%), and pulmonary embolism (3.7%). The postoperative length of stay was significantly shorter for patients who were readmitted than for the controls (2.7 ± 1.0 days vs 3.9 ± 3.2 days; p < 0.05). Patients readmitted for hyponatremia had an initial length of stay of 2.6 ± 0.9 days, the shortest of any cause for readmission. The mean BMI was significantly lower for readmitted patients than for the controls (26.4 ± 3.9 kg/m2 vs 29.3 ± 6.1 kg/m2; p < 0.05).

CONCLUSIONS

Readmission after EETS for pituitary adenoma is a relatively rare phenomenon, with delayed hyponatremia being the primary cause. The study results demonstrate that shorter postoperative length of stay and lower BMI were associated with 30-day readmission.

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.

Tolvaptan Versus Fluid Restriction in the Treatment of Hyponatremia Resulting from SIADH Following Pituitary Surgery

Context

The relevance of hyponatremia has been acknowledged by guidelines from the United States (2013) and Europe (2014). However, treatment recommendations differ due to limited evidence.

Objective

In hyponatremia following pituitary surgery-caused by the syndrome of inappropriate antidiuretic hormone (SIADH) secretion-we compared fluid restriction with the pharmacological increase of water excretion by blocking the vasopressin 2 receptors with tolvaptan at a low and a moderate dose.

Design

Prospective observational study.

Setting

Neurosurgical Department of a University hospital with more than 200 surgical pituitary procedures per year.

Patients

Patients undergoing pituitary surgery and developing serum sodium below 136 mmol/L. The diagnosis of SIADH was established by euvolemia (daily measurement of body weight and fluid balance), inappropriately concentrated urine (specific gravity), and exclusion of adrenocorticotropic and thyroid-stimulating hormone deficiency.

Intervention

Patients were treated with fluid restriction (n = 40) or tolvaptan at 3.75 (n = 38) or 7.5 mg (n = 48).

Main Outcome Measures

Treatment efficacy was assessed by the duration of hyponatremia, sodium nadir, and length of hospitalization. Safety was established by a sodium increment below 10 mmol/L per day and exclusion of side effects.

Results

Treatment with 7.5 mg of tolvaptan resulted in a significant attenuation of hyponatremia and in a significant overcorrection of serum sodium in 30% of patients. The duration of hospitalization did not differ between treatment groups.

Conclusions

Tolvaptan at a moderate dose is more effective than fluid restriction in the treatment of SIADH. Overcorrection of serum sodium may be a side effect of tolvaptan even at low doses.

ICAR: endoscopic skull-base surgery

BACKGROUND

Endoscopic skull-base surgery (ESBS) is employed in the management of diverse skull-base pathologies. Paralleling the increased utilization of ESBS, the literature in this field has expanded rapidly. However, the rarity of these diseases, the inherent challenges of surgical studies, and the continued learning curve in ESBS have resulted in significant variability in the quality of the literature. To consolidate and critically appraise the available literature, experts in skull-base surgery have produced the International Consensus Statement on Endoscopic Skull-Base Surgery (ICAR:ESBS).

METHODS

Using previously described methodology, topics spanning the breadth of ESBS were identified and assigned a literature review, evidence-based review or evidence-based review with recommendations format. Subsequently, each topic was written and then reviewed by skull-base surgeons in both neurosurgery and otolaryngology. Following this iterative review process, the ICAR:ESBS document was synthesized and reviewed by all authors for consensus.

RESULTS

The ICAR:ESBS document addresses the role of ESBS in primary cerebrospinal fluid (CSF) rhinorrhea, intradural tumors, benign skull-base and orbital pathology, sinonasal malignancies, and clival lesions. Additionally, specific challenges in ESBS including endoscopic reconstruction and complication management were evaluated.

CONCLUSION

A critical review of the literature in ESBS demonstrates at least the equivalency of ESBS with alternative approaches in pathologies such as CSF rhinorrhea and pituitary adenoma as well as improved reconstructive techniques in reducing CSF leaks. Evidence-based recommendations are limited in other pathologies and these significant knowledge gaps call upon the skull-base community to embrace these opportunities and collaboratively address these shortcomings.

Criteria for Hyponatremic Overcorrection: Systematic Review and Cohort Study of Emergently Ill Patients

BACKGROUND

Hyponatremia is the most common electrolyte disturbance amongst hospitalized patients. An overly rapid rate of correction of chronic hyponatremia is believed to increase the risk of poor clinical outcomes including osmotic demyelination syndrome (ODS). There is disagreement in the literature regarding the definition of hyponatremic overcorrection.

METHODS

We performed a systematic review of all English language studies to identify those that calculated sodium correction rate and classified patients' overcorrection status. We then identified all patients who presented to our hospital's emergency department between 2003 and 2015 with a corrected serum sodium ≤ 116 mmol/L. All methods from the systematic review for sodium correction rate calculation and overcorrection status were applied to this cohort.

RESULTS

We identified 24 studies citing 9 distinct sodium correction rate methods and 14 criteria for overcorrection. Six hundred twenty-four patients presenting with severe hyponatremia (median initial value 113 mMol) were identified. Depending on the method used, the median sodium correction rates in our cohort ranged from 0.271 to 1.13 mmol/L per hour. The proportion of patients classified with overcorrection with the different criteria varied almost 11-fold, ranging from 8.5 to 89.9%.

CONCLUSION

Published methods disagree regarding the calculation of sodium correction rates and the definition of hyponatremic overcorrection. This leads to wide variations in sodium correction rates and the prevalence of overcorrection in patient cohorts. Definitions based on ODS risk are needed.

Inappropriate Antidiuretic Hormone Secretion and Cerebral Salt-Wasting Syndromes in Neurological Patients

The differential diagnosis of syndrome of inappropriate antidiuretic hormone secretion (SIADH) and cerebral salt-wasting syndrome (CSWS) in patients with neurological disorders has been a perplexing clinical controversy. The purpose of this review is to summarize the characteristics and risk factors of patients with different types of neurological disorders complicated by hyponatremia (HN) and review various methods to distinguish SIADH from CSWS. Common neurological disorders with high rates of HN include subarachnoid hemorrhage (SAH), traumatic brain injuries, stroke, cerebral tumors, central nervous system (CNS) infections, and Guillain-Barré syndrome (GBS), which have their own characteristics. Extracellular volume (ECV) status of patients is a key point to differentiate SIADH and CSWS, and a comprehensive assessment of relevant ECV indicators may be useful in differentiating these two syndromes. Besides, instead of monitoring the urinary sodium excretion, more attention should be paid to the total mass balance, including Na⁺, K⁺, Cl^-, and extracellular fluid. Furthermore, the dynamic detection of fractional excretions (FE) of urate before and after correction of HN and a short-term infusion of isotonic saline solution may be useful in identifying the etiology of HN. As for brain natriuretic peptide (BNP) or N-terminal prohormone of BNP (NT-proBNP), more prospective studies and strong evidence are needed to determine whether there is a pertinent and clear difference between SIADH and CSWS.

CLINICAL PRACTICE PATTERNS FOR POSTOPERATIVE WATER BALANCE AFTER PITUITARY SURGERY

Objective: Abnormalities of water and sodium balance, including diabetes insipidus and the syndrome of inappropriate antidiuretic hormone (SIADH), are common complications of transsphenoidal surgery. Postoperative practice patterns vary among clinicians, and no consensus guidelines exist to direct their monitoring and management. We aimed to identify and compare practice patterns regarding the evaluation and management to these postoperative complications. Methods: A questionnaire was utilized to capture demographic data and practice habits in the postoperative setting. Respondents were members of the Pituitary Society, an international organization comprised of clinicians and researchers dedicated to the study of pituitary disease. Results: Eighty-six respondents completed at least part of the survey. The geographic distribution of respondents was roughly even between American and non-American practitioners. The majority of respondents practiced at academic institutions (67.4%), worked in multidisciplinary teams (88.4%), and possessed significantly greater than 10 years of clinical experience (71%). Compared to non-American practitioners, American practitioners described a shorter length of stay postoperatively (P<.001) and prescribed more restrictive volume recommendations for postoperative SIADH (P = .0035). Early career clinicians (less than 10 years in practice) checked first postoperative sodium level earlier than later career clinicians (P = .010). Conclusion: Water and sodium dysregulation are common following transsphenoidal surgery, but their management is not well-standardized in clinical practice. We created a questionnaire to define and compare practice patterns. Most respondents practice in academic settings in multidisciplinary teams. The length of clinical experience did not significantly impact practice habits. Practice location influenced length of stay postoperatively and fluid restriction in SIADH. Abbreviations: AVP = arginine vasopressin; DI = diabetes insipidus; LOS = length of stay; SIADH = syndrome of inappropriate antidiuretic hormone.

Strategies to reduce readmissions for hyponatremia after transsphenoidal surgery for pituitary adenomas

PURPOSE

Disorders of water balance, particularly hyponatremia from altered antidiuretic hormone (ADH) secretion, are a common post-operative complication of transsphenoidal surgery (TSS). We present our results from implementation of a 2-week 1.5 liter/daily fluid restriction on readmission rates for hyponatremia.

METHODS

A retrospective chart review was performed on 295 patients that underwent TSS for pituitary adenomas at the University of Colorado, between March 2014 and March 2017. Groups were divided into those before and after the implementation of a two-week, 1.5 liter daily fluid restriction and measurement of a serum sodium level 7 days (+/- 2 days) after discharge. A standard-of-care approach for variable degrees of hyponatremia was also utilized to guide hyponatremia management. Patient demographics, hospital course, post-operative complication rates, and rates of hospital admissions for hyponatremia were then evaluated.

RESULTS

Readmissions for symptomatic hyponatremia within 30 days of TSS occurred in 9 of 118 (7.6%) of patients prior to fluid restriction implementation and in four of 169 (2.4%) of patients in the post-implementation, fluid-restricted group (p-value = 0.04): a 70% reduction in hospitalizations. The two groups were similarly matched for pituitary tumor sub-type, age and gender. None of these factors were predictive for hyponatremia. Importantly, the mild fluid restriction did not result in any hospital readmissions for hypernatremia.

CONCLUSIONS

Mild fluid restriction (to 1.5 liters daily), in addition to a single post-operative serum sodium level, is an effective approach to preventing readmission for hyponatremia after TSS for pituitary adenomas.

Implementation of a Postoperative Outpatient Care Pathway for Delayed Hyponatremia Following Transsphenoidal Surgery

BACKGROUND

After transsphenoidal surgery, delayed hyponatremia (DH) is the leading cause of 30-d unplanned hospital readmissions.

OBJECTIVE

To determine the impact of a DH care pathway on 30-d readmissions after transsphenoidal surgery.

METHODS

Data from before and after DH care pathway implementation were retrospectively reviewed. Patient demographics and clinical characteristics were compared. Readmission causes, clinical pathway failures, sodium trends, and symptoms were evaluated.

RESULTS

Before the DH care pathway implementation, 229 (55%) patients were treated (group 1); afterward, 188 (45%) were treated (group 2). Baseline characteristics were equivalent between groups, except for glucocorticoid supplementation, which was higher in group 2. The incidence of detected DH was significantly lower in group 1 (16/229, 7%) than group 2 (29/188, 15%) (P = .006) likely due to the impact of routine screening in group 2. Ten group 1 patients (4%) were readmitted for hyponatremia and 6 (3%) were managed as outpatients. Eleven group 2 patients (6%) were readmitted and 17 (9%) were managed as outpatients. Readmission rates between groups were similar (P = .49). Patients readmitted with severe hyponatremia experienced symptoms ≥24 h before presentation. The protocol failed to prevent readmission because outpatient management for mild or moderate DH (n = 4) failed, sodium levels precipitously declined after normal screening (n = 3), and severe hyponatremia developed after scheduled screenings were missed (n = 3).

CONCLUSION

Although more DH patients were identified after care pathway implementation, readmission rates were not reduced and clinical outcomes were not changed. Because DH onset timing varies, some patients have highly acute presentation, and most readmitted patients develop symptoms before reaching their sodium nadir, close symptom monitoring may be a reasonable alternative to routine screening.

A practical method for prevention of readmission for symptomatic hyponatremia following transsphenoidal surgery

INTRODUCTION

Patients undergoing transsphenoidal pituitary surgery (TSS) are at risk for several serious complications, including the syndrome of inappropriate antidiuretic hormone and subsequent hyponatremia.

OBJECTIVE

In this study, we examined the effect of 1 week of post-discharge fluid restriction to 1.0 L daily on rates of post-operative readmission for hyponatremia.

METHODS

We retrospectively analyzed all patients undergoing TSS from 2008 to 2014 and prospectively recorded patient data from 2015 to 2017. Patients were divided into a control cohort (2008-2014), who were discharged with instructions to drink to thirst; and an intervention cohort (2015-2017) who were instructed to drink less than 1.0 L daily for 1 week post-operatively.

RESULTS

This study included 788 patients; 585 (74.2%) in the control cohort and 203 (25.8%) in the intervention cohort. Overall, 436 (55.3%) were women, the median age was 47 (range 15-89), and average BMI was 29.4 kg/m² (range 17.7-101.7). Patients were relatively well matched. Of patients in the intervention group, none was readmitted for hyponatremia (0/203), compared to 3.41% (20/585) in the control group (p = 0.003). Patients in the intervention group also had significantly higher post-operative week one sodium levels (140.1 vs 137.5 mEq/L; p = 0.002). No fluid balance complications occurred in patients who followed this protocol.

CONCLUSION

Hyponatremia can be a life-threatening complication of TSS, and prevention of readmission for hyponatremia can help improve patient safety and decrease costs. Mandatory post-discharge fluid restriction is a simple and inexpensive intervention associated with decreased rates of readmission for hyponatremia and normal post-operative sodium levels.

Physiologic Mechanisms of Water and Electrolyte Disturbances After Transsphenoidal Pituitary Surgery

BACKGROUND

Disturbances in water and electrolyte homeostasis are common after transsphenoidal surgery. These disorders are variable and unpredictable, increasing patient risk and complicating postsurgical treatment. Clinically, it is generally accepted that damage to the pituitary is the cause, but the mechanisms behind the response variability and underlying pathophysiology remain unknown.

OBJECTIVE

To test the hypothesis that changing the degree of damage to the pituitary stalk produces a spectrum of water and electrolyte disturbance along which all presentations of postsurgical water and electrolyte disturbances can be identified.

METHODS

We used HumMod, a large mathematical model of physiology, to simulate pituitary stalk damage at differing fractions: 20%, 40%, 60%, and 80%. The damaged neurons were modeled to undergo a 5-day countdown to degeneration and release stored antidiuretic hormone as they die, as is proposed to occur.

RESULTS

Lower pituitary damage (20%) resulted in transient polyuria and intermediate damage (40%) was associated with delayed polyuria and diabetes insipidus. Higher levels of damage (60% and 80%) showed a triphasic pattern of diabetes insipidus.

CONCLUSIONS

We postulate that our model provides a plausible mechanistic explanation for some varieties of postsurgical water and electrolyte disturbances, in which increasing damage to the pituitary potentiates the likelihood of a full triphasic response. However, our simulation shows that merely modifying the level of damage does not produce every presentation of water and electrolyte imbalance. This theory suggests that other mechanisms, which are still unclear and not a part of this model, may be responsible for postoperative hyponatremia and require further investigation.

Efficacy of oral tolvaptan versus 3% hypertonic saline for correction of hyponatraemia in post-operative patients

Background and Aims:

Hyponatraemia is frequent in post-operative patients and may be corrected with hypertonic saline (HTS). Oral tolvaptan is used to treat hypervolaemic or euvolaemic hyponatraemia. This study was performed to assess the efficacy of oral tolvaptan in correcting postoperative hyponatraemia compared to HTS.

Methods:

This prospective, randomised study was conducted in 40 symptomatic patients with serum sodium level ≤130 mEq/L. In Group H (n = 20), 3% HTS was infused at 20–30 mL/h aiming for correction of 6 mEq/L/day. Group T received oral tolvaptan 15 mg on the 1^st day. If daily correction was <4 mEq/L, the dose was increased by 15 mg/day to a maximum of 45 mg. The primary outcome was serum sodium concentration 48 hours after starting treatment. Paired t-test was used to compare changes in sodium levels.

Results:

Baseline sodium and values at 12, 24 and 48 h were comparable in both groups. At 72 h, Group T had significantly higher sodium levels as compared to Group H (133.4 ± 1.9 vs. 131.3 ± 2.4 mEq/L). Intragroup analysis had shown a significant increase in sodium levels from baseline values in both groups at 12, 24, 48 and 72 h. Group H had a significantly lower potassium level and lower negative fluid balance on day 3.

Conclusion:

Oral tolvaptan and 3% HTS were equally effective in correcting hyponatraemia at 48 hours, but serum sodium levels were higher at 72 hours after oral tolvaptan.

Delayed Hyponatremia Is the Most Common Cause of 30-Day Unplanned Readmission After Transsphenoidal Surgery for Pituitary Tumors

BACKGROUND

Unplanned readmission after surgical procedures is an important quality metric. Yet, readmission rates and causes have not been evaluated for patients after transsphenoidal surgery for pituitary tumors.

OBJECTIVE

To analyze unplanned 30-day readmissions at a pituitary center and to encourage the development of effective clinical pathways to prevent readmission.

METHODS

A retrospective review of adult patients who underwent transsphenoidal surgery for pituitary lesions at Barrow Neurological Institute (January 2011-March 2014) was performed to identify causes of unplanned readmission within 30 days of surgery. Patient demographics, tumor details, surgical complications, and endocrine function were documented.

RESULTS

Of 303 patients who had transsphenoidal surgery, 27 (8.9%) were readmitted within 30 days. Most of the 27 (15 [55.6%]) had delayed hyponatremia. Other causes were diabetes insipidus (4 [14.8%]), adrenal insufficiency (2 [7.4%]), and cerebrospinal fluid leak, epistaxis, cardiac arrhythmia, pneumonia, urinary tract infection, and hypoglycemia (1 each [3.7%]). Outpatient sodium screening was performed as needed. In cases of hyponatremia, the mean postoperative day of readmission was day 8 (range, 6-12 days) and the mean serum sodium was 119 mmol/L (range, 111-129 mmol/L). Numerous patient and surgical factors were examined, and no specific predictors of readmission were identified. We developed an outpatient care pathway for managing hyponatremia with the goal of improving readmission rates.

CONCLUSION

This study establishes a quality benchmark for readmission rates after transsphenoidal surgery for pituitary lesions and identifies delayed hyponatremia as the primary cause. Implementation of an outpatient care pathway for managing hyponatremia may improve readmission rates.

Incidence and Risk Factors for Prolonged Hospitalization and Readmission after Transsphenoidal Pituitary Surgery

Objective

To evaluate the incidence and factors associated with 30-day readmission and to analyze risk factors for prolonged hospital length of stay following transsphenoidal pituitary surgery.

Study Design

Retrospective longitudinal claims analysis.

Setting

American College of Surgeons National Surgical Quality Improvement Program.

Subjects and Methods

The database of the American College of Surgeons National Surgical Quality Improvement Program was queried for patients who underwent transsphenoidal pituitary surgery ( Current Procedural Terminology code 61548 or 62165) between 2005 and 2014. Patient demographic information, indications for surgery, and incidence of hospital readmission and length of stay were reviewed. Risk factors for readmission and prolonged length of stay, defined as >75th percentile for the cohort, were identified through logistic regression modeling.

Results

A total of 1006 patients were included for analysis. Mean hospital length of stay after surgery was 4.1 ± 0.2 days. Predictors of prolonged length of stay were operative time ( P < .001, odds ratio [OR] = 1.7, 95% confidence interval [95% CI] = 1.5-2.0), bleeding disorder ( P = .049, OR = 3.1, 95% CI = 1.0-9.5), insulin-dependent diabetes ( P = .007, OR = 2.4, 95% CI = 1.3-4.4), and reoperation ( P < .001, OR = 10.3, 95% CI = 4.7-23.9). In a subset analysis of 529 patients who had surgery between 2012 and 2014, 7.2% (n = 38) required hospital readmission. History of congestive heart failure (CHF) was a predictor of hospital readmission ( P = 0.03, OR = 12.7, 95% CI = 1.1-144.0).

Conclusion

This review of a large validated surgical database demonstrates that CHF is an independent predictor of hospital readmission after transsphenoidal surgery. Although CHF is a known risk factor for postoperative complications, it poses unique challenges to patients with potential postoperative pituitary dysfunction.

Diagnosis and treatment of hyponatraemia in neurosurgical patients

Hyponatraemia is the most common electrolyte imbalance in neurosurgical patients. Acute hyponatraemia is particularly common in neurosurgical patients after any type of brain insult, including brain tumours and their treatment, pituitary surgery, subarachnoid haemorrhage or traumatic brain injury. Acute hyponatraemia is an emergency condition, as it leads to cerebral oedema due to passive osmotic movement of water from the hypotonic plasma to the relatively hypertonic brain which ultimately is the cause of the symptoms associated with hyponatraemia. These include decreased level of consciousness, seizures, non-cardiogenic pulmonary oedema or transtentorial brain herniation. Prompt treatment is mandatory to prevent such complications, minimize permanent brain damage and therefore permit rapid recovery after brain insult. The infusion of 3% hypertonic saline is the treatment of choice with different rates of administration based on the severity of symptoms and the rate of drop in plasma sodium concentration. The pathophysiology of hyponatraemia in neurotrauma is multifactorial; although the syndrome of inappropriate antidiuresis (SIADH) and central adrenal insufficiency are the commonest causes encountered. Fluid restriction has historically been the classical treatment for SIADH, although it is relatively contraindicated in some neurosurgical patients such as those with subarachnoid haemorrhage. Furthermore, many cases admitted have acute onset hyponatraemia, who require hypertonic saline infusion. The recently developed vasopressin receptor 2 antagonist class of drug is a promising and effective tool but more evidence is needed in neurosurgical patients. Central adrenal insufficiency may also cause acute hyponatraemia in neurosurgical patients; this responds clinically and biochemically to hydrocortisone. The rare cerebral salt wasting syndrome is treated with large volume normal saline infusion. In this review, we summarize the current evidence based on the clinical presentation, causes and treatment of different types of hyponatraemia in neurosurgical patients.

Hyponatremia in Neurotrauma: The Role of Vasopressin

Hyponatremia is frequent in patients suffering from traumatic brain injury, subarachnoid hemorrhage, or following intracranial procedures, with approximately 20% having a decreased serum sodium concentration to <125 mmol/L. The pathophysiology of hyponatremia in neurotrauma is not completely understood, but in large part is explained by the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). The abnormal water and/or sodium handling creates an osmotic gradient promoting the shift of water into brain cells, thereby worsening cerebral edema and precipitating neurological deterioration. Unless hyponatremia is corrected promptly and effectively, morbidity and mortality increases through seizures, elevations in intracranial pressure, and/or herniation. The excess mortality in patients with severe hyponatremia (<125 mmol/L) extends beyond the time frame of hospital admission, with a reported mortality of 20% in hospital and 45% within 6 months of follow-up. Current options for the management of hyponatremia include fluid restriction, hypertonic saline, mineralocorticoids, and osmotic diuretics. However, the recent development of vasopressin receptor antagonists provides a more physiological tool for the management of excess water retention and consequent hyponatremia, such as occurs in SIADH. This review summarizes the existing literature on the pathophysiology, clinical features, and management of hyponatremia in the setting of neurotrauma.

Treatment of Hyponatremia with Tolvaptan in a Patient after Neurosurgical Treatment of a Pituitary Tumor: Case Report and Review of Literature

Hyponatremia is a frequent complication following pituitary surgery. We report a case with hyponatremia after surgery of a pituitary adenoma that was successfully treated with tolvaptan. A 68-year-old man with a pituitary tumor presented with mild hyponatremia (133 mEq/L) before surgery. The patient developed hyponatremia (125 mEq) 4 days postsurgery, and 10% sodium chloride was infused. Seven 7 days postsurgery, hyponatremia was improved (132 mEq/L), and tolvaptan 15 mg was given orally as a single dose instead of the 10% sodium chloride infusion. His serum sodium remained within normal limits. The syndrome of inappropriate antidiuretic hormone secretion (SIADH) after pituitary surgery most probably led to the hyponatremia, and tolvaptan was effective because it is an oral vasopressin receptor antagonist.

Hyponatremia in the neurocritical care patient: An approach based on current evidence

In the neurocritical care setting, hyponatremia is the commonest electrolyte disorder, which is associated with significant morbimortality. Cerebral salt wasting and syndrome of inappropriate antidiuretic hormone have been classically described as the 2 most frequent entities responsible of hyponatremia in neurocritical care patients. Nevertheless, to distinguish between both syndromes is usually difficult and useless as volume status is difficult to be determined, underlying pathophysiological mechanisms are still not fully understood, fluid restriction is usually contraindicated in these patients, and the first option in the therapeutic strategy is always the same: 3% hypertonic saline solution. Therefore, we definitively agree with the current concept of "cerebral salt wasting", which means that whatever is the etiology of hyponatremia, initially in neurocritical care patients the treatment will be the same: hypertonic saline solution.

Incidence, Etiology and Outcomes of Hyponatremia after Transsphenoidal Surgery: Experience with 344 Consecutive Patients at a Single Tertiary Center

Hyponatremia is often seen after transsphenoidal surgery and is a source of considerable economic burden and patient-related morbidity and mortality. We performed a retrospective review of 344 patients who underwent transsphenoidal surgery at our institution between 2006 and 2012. Postoperative hyponatremia was seen in 18.0% of patients at a mean of 3.9 days postoperatively. Hyponatremia was most commonly mild (51.6%) and clinically asymptomatic (93.8%). SIADH was the primary cause of hyponatremia in the majority of cases (n = 44, 71.0%), followed by cerebral salt wasting (n = 15, 24.2%) and desmopressin over-administration (n = 3, 4.8%). The incidence of postoperative hyponatremia was significantly higher in patients with cardiac, renal and/or thyroid disease (p = 0.0034, Objective Risk (OR) = 2.60) and in female patients (p = 0.011, OR = 2.18) or patients undergoing post-operative cerebrospinal fluid drainage (p = 0.0006). Treatment with hypertonic saline (OR = −2.4, p = 0.10) and sodium chloride tablets (OR = −1.57, p = 0.45) was associated with a non-significant trend toward faster resolution of hyponatremia. The use of fluid restriction and diuretics should be de-emphasized in the treatment of post-transsphenoidal hyponatremia, as they have not been shown to significantly alter the time-course to the restoration of sodium balance.

Neurosurgical Hyponatremia

Hyponatremia is a frequent electrolyte imbalance in hospital inpatients. Acute onset hyponatremia is particularly common in patients who have undergone any type of brain insult, including traumatic brain injury, subarachnoid hemorrhage and brain tumors, and is a frequent complication of intracranial procedures. Acute hyponatremia is more clinically dangerous than chronic hyponatremia, as it creates an osmotic gradient between the brain and the plasma, which promotes the movement of water from the plasma into brain cells, causing cerebral edema and neurological compromise. Unless acute hyponatremia is corrected promptly and effectively, cerebral edema may manifest through impaired consciousness level, seizures, elevated intracranial pressure, and, potentially, death due to cerebral herniation. The pathophysiology of hyponatremia in neurotrauma is multifactorial, but most cases appear to be due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Classical treatment of SIADH with fluid restriction is frequently ineffective, and in some circumstances, such as following subarachnoid hemorrhage, contraindicated. However, the recently developed vasopressin receptor antagonist class of drugs provides a very useful tool in the management of neurosurgical SIADH. In this review, we summarize the existing literature on the clinical features, causes, and management of hyponatremia in the neurosurgical patient.