Postoperative Hyponatremia Predicts an Increase in Mortality and In-Hospital Complications after Cardiac Surgery

Association Between Early Hyponatremia and Clinical Outcomes in Critically Ill Patients: A Retrospective Cohort Study

INTRODUCTION

Hyponatremia, frequently encountered in intensive care (ICU) settings, plays a critical role in shaping patient outcomes. Despite its prevalence, contemporary research into its newly classified severity categories and their implications on mortality, renal function, and length of stay remains limited. This study aims to fill this gap by examining the impact of hyponatremia severity on these critical outcomes.

METHODS

A retrospective analysis of ICU patients aged >18 years who were admitted between March 2019 and December 2022 was conducted at Hamamatsu University Hospital, Shizuoka, Japan. Patients who were readmitted or had incomplete data were excluded. Hyponatremia was categorized as mild (130-135 mmol/L), moderate (125-129 mmol/L), or severe (<125 mmol/L), following the criteria set by the European Society of Intensive Care Medicine. This classification utilized the lowest sodium concentration within 24 hours of ICU admission. The outcomes were in-hospital mortality, ICU mortality, newly implemented renal replacement therapy (RRT), and length of hospital and ICU stay. Outcomes were analyzed using multivariable logistic and linear regression models, adjusting for relevant covariates including age, sex, Acute Physiology and Chronic Health Evaluation (APACHE) III scores, and the use of mechanical ventilation.

RESULTS

Of the 3,538 patients analyzed, 1,072 (30.3%) experienced hyponatremia: 894 (25.3%) mild, 144 (4.1%) moderate, and 34 (1.0%) severe. Multivariable analysis revealed no significant association between hyponatremia severity and in-hospital mortality rates across normonatremia (3.8%), mild (5.2%), moderate (11.8%), and severe (23.5%) groups, nor with ICU mortality. However, compared to normonatremia, moderate and severe hyponatremia were associated with increased RRT initiation (odds ratios = 3.83 and 6.36, respectively) and prolonged hospital stay (mean difference = 7.06 and 9.66 days, respectively), and ICU stays (mean difference, 1.02 and 2.70 days, respectively). Mild hyponatremia was not significantly associated with RRT or length of stay.

CONCLUSION

Moderate-to-severe hyponatremia did not influence mortality but was associated with increased RRT initiation and prolonged hospital and ICU stay. By contrast, mild hyponatremia was not associated with any clinical outcome. Further research is required to determine if correcting hyponatremia directly improves ICU patient outcomes, given the observational nature of the study.

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.

Impacts of perioperative hyponatremia relevant to outcomes and prognosis of non-small cell lung cancer in octogenarians

BACKGROUND

A recent study reported the effect of preoperative hyponatremia on postoperative outcomes of patients with non-small cell lung cancer. However, the influence of postoperative hyponatremia on postoperative outcomes has not been completely investigated.

METHODS

We retrospectively studied 75 octogenarians who underwent pulmonary surgery for non-small cell lung cancer between 2009 and 2018. We divided them into hyponatremic and non-hyponatremic groups, depending on preoperative and immediate postoperative serum sodium levels, and investigated their clinicopathological characteristics and outcomes. Disease-specific survival and cumulative incidence of relapse rates between the two groups were calculated and compared using the stratified Kaplan-Meier method. Univariable and multivariable analyses were performed to identify prognostic factors.

RESULTS

Preoperative hyponatremia was associated with 66.7% of postoperative respiratory and 88.9% of non-cardiovascular complications. The long-term prognosis of the postoperative hyponatremic group was significantly worse than that of their counterpart. The 3-year disease-specific survival and 3-year cumulative incidence of relapse rate were 55.9% and 46.2%, respectively, and the median observation period after surgery was 37.4 (interquartile range, 23.7-51.0) months for the entire cohort. Kaplan-Meier curves showed that hyponatremia was associated with worse disease-specific survival and cumulative incidence of relapse. Multivariable analysis identified hyponatremia as a factor that predicted unfavorable disease-specific survival and cumulative incidence of relapse.

CONCLUSIONS

Immediate postoperative hyponatremia is an independent predictor of non-small cell lung cancer outcomes among octogenarians. Preoperative hyponatremia was associated with a high frequency of postoperative respiratory and non-cardiovascular complications. Surgical indications in older patients with hyponatremia should be carefully considered with follow-up.

Prevalence, risk factors, and potential symptoms of hyponatremia after spinal surgery in elderly patients

Old age and spinal surgery significantly increase the risk of postoperative hyponatremia. However, detailed analyses of postoperative hyponatremia after spinal surgery in elderly patients are lacking. Therefore, we retrospectively reviewed the records of 582 consecutive patients aged > 60 years who underwent spinal surgery to evaluate the frequency, risk factors, and symptoms of postoperative hyponatremia after spinal surgery in the elderly population. Postoperative hyponatremia was defined as a postoperative blood sodium level < 135 meq/L at postoperative day (POD)1, POD3, and/or after POD6. A total of 92 (15.8%) patients showed postoperative hyponatremia. On a multivariate analysis, a diagnosis of a spinal tumor/infection, decompression and fusion surgery, and lower preoperative sodium levels were significant independent factors of postoperative hyponatremia (p = 0.014, 0.009, and < 0.001, respectively). In total, 47/92 (51%) cases could have been symptomatic; vomiting was noted in 34 cases (37%), nausea in 19 cases (21%), headache in 14 cases (15%), and disturbances in consciousness, including delirium, in ten cases (21%); all incidences of these symptoms were significantly higher in elderly patients with postoperative hyponatremia than in the matched control group without postoperative hyponatremia (p < 0.05, respectively). Additionally, the length of stay was 2 days longer in patients than in the matched controls (p = 0.002).

Preoperative Hyponatremia is an Independent Risk Factor for Prolonged Hospital Stay Following Anterior Cervical Discectomy and Fusion

OBJECTIVE

To determine the effects of preoperative hyponatremia on short-term postoperative complications and healthcare utilization (length of stay, readmissions) following anterior cervical fusion and discectomy (ACDF).

METHODS

Patients who underwent ACDF were identified in the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database. Patients who had revision surgery, trauma, vertebral malignancy, or infection were excluded. Eunatremia was defined as sodium (Na) level between 135 and 145 mEq/L, whereas hyponatremia was defined as Na < 135 mEq/L. Preoperatively hyponatremic patients were matched 1:1 with eunatremic patients using propensity-score matching based upon age, gender, American Society of Anesthesiology (ASA) score, and baseline comorbidities. Minor adverse events included superficial infection, dehiscence, urinary tract infection, pneumonia, and renal insufficiency or failure. Serious adverse events included deep wound infection, reintubation, pulmonary embolism, cerebrovascular accident, cardiac arrest, deep vein thrombosis, sepsis, return to operating room, and death within 30 days. Complications were analyzed using bivariate and logistic analysis with significance set at p<0.05.

RESULTS

Of the 9,094 patients undergoing ACDF, 3.64% (331 patients) were preoperatively hyponatremic. Preoperative hyponatremia was an independent risk factor for postoperative pneumonia following ACDF (OR=4.47; p=0.020) as well as extended length of hospital stay greater than one standard deviation above the mean (OR=1.71; p=0.042). Preoperative hyponatremia was an independent risk factor for having a serious adverse event (OR=2.40; p=0.005), as well as any adverse event (OR=2.44; p=0.009).

CONCLUSION

Preoperative hyponatremia is an independent risk factor for pneumonia and prolonged length of stay following ACDF.

Predischarge Prediction of Readmission After Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy: Derivation and Validation of a Risk Prediction Score

BACKGROUND

Ninety-day hospital readmission rates following cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) range from 20 to 40%.

OBJECTIVE

The aim of this study was to develop and validate a simple score to predict readmissions following CRS/HIPEC.

STUDY DESIGN

Using a prospectively maintained database, we retrospectively reviewed clinicopathologic, perioperative, and day-of-discharge data for patients undergoing CRS/HIPEC for peritoneal surface malignancies between 2010 and 2018. In-hospital mortalities and discharges to hospice were excluded. Multivariate logistic regression was utilized to identify predictors of unplanned readmission, with three-quarters of the sample randomly selected as the derivation cohort and one-quarter as the validation cohort. Using regression coefficient-based scoring methods, we developed a weighted 7-factor, 10-point predictive score for risk of readmission.

RESULTS

Overall, 1068 eligible discharges were analyzed; 379 patients were readmitted within 90 days (35.5%). Seven factors were associated with readmission: stoma creation, Peritoneal Cancer Index score ≥ 15, hyponatremia, in-hospital major complication, preoperative chemotherapy, anemia, and discharge to nursing home. In the validation cohort, 25 patients (9.2%) were categorized as high risk for readmission, with a predicted rate of readmission of 69.3% and an observed rate of 76.0%. The score had fair discrimination (area under the curve 0.70) and good calibration (Hosmer-Lemeshow goodness-of-fit p-value of 0.77).

CONCLUSION

Our proposed risk score, easily obtainable on day of discharge, distinguishes patients at high risk for readmission over 90 days following CRS/HIPEC. This score has the potential to target high-risk individuals for intensive follow-up and other interventions.

Implications of Postpancreatectomy Hypophosphatemia

BACKGROUND

Electrolyte abnormalities are commonly found after major abdominal surgery for malignancy. We hypothesized that the severity of hypophosphatemia developed in pancreatectomy patients would be associated with the incidence of complications postoperatively.

METHODS

A retrospective analysis of an institutional database was conducted for all pancreatic resections (2009-2017). Patient charts were reviewed for demographics, clinicopathologic factors, and perioperative outcomes.

RESULTS

In a cohort of 283 pancreatectomy patients, 107 (37.8%) and 134 (47.3%) developed mild (2.0-2.5 mg/dL) and moderate/severe hypophosphatemia (<2.0 mg/dL), respectively. Nadir serum phosphate levels were shown to occur on postoperative day (POD) 2 for patients without complications and POD3 for patients who had at least 1 complication. Patients who developed severe hypophosphatemia were significantly more likely to suffer fistula-related complications (P = .0401).

CONCLUSIONS

Assessing the severity and timing of postpancreatectomy hypophosphatemia presents an opportunity for early detection of impending fistula-related complications.

Efficacy of tolvaptan for fluid management after cardiovascular surgery: A systematic review and meta-analysis of randomized control trials

The purpose of this study was to systematically search the literature and analyze evidence from randomized controlled trials (RCTs) comparing tolvaptan with conventional diuretics for postoperative fluid management in cardiac surgery patients. An electronic search of PubMed, Scopus, BioMed Central, CENTRAL (Cochrane Central Register of Controlled Trials) and Google scholar databases was carried out up to 1st December 2019. Four RCTs were included. Tolvaptan was co-administered with conventional diuretics in all the studies. The mean postoperative urine output was significantly greater in patients receiving tolvaptan as compared to controls (MD=0.39; 95% CI: 0.17 to 0.61; P=0.006, I²=48%). Body weight of patients on tolvaptan returned to pre-operative levels significantly earlier (MD=-1.57; 95% CI: -2.48 to -0.66; P=0.007, I²=50%). There was statistical significant difference in the highest postoperative serum sodium levels (MD=2.34; 95% CI: -1.65 to 3.03; p<0.00001, I²=0%), lowest serum sodium levels (MD=2.05; 95% CI: 1.41 to 2.68; p<0.00001, I²=0%) and mean serum sodium levels (MD=1.69; 95% CI: 0.98 to 2.40; p<0.00001, I²=0%) between the tolvaptan and control groups. Lowest serum potassium was significantly higher with tolvaptan as compared to the control group (MD=0.10; 95% CI: 0.01 to 0.18; P=0.03, I²=19%). There was no significant difference in the length of ICU stay or incidence of arrhythmias between the two groups. The quality of the included studies was not high. Within the limitations of our study, our results indicate that co-administration of tolvaptan with low dose of conventional diuretics significantly increases urine output while maintaining electrolyte balance in postoperative cardiac surgery patients. Faster return of body weight to pre-operative levels is evident with tolvaptan. Further high-quality RCTs are required to confirm this evidence.

Trends and Outcomes in Sepsis Hospitalizations With and Without Atrial Fibrillation: A Nationwide Inpatient Analysis

OBJECTIVES

Atrial fibrillation is frequently seen in sepsis-related hospitalizations. However, large-scale contemporary data from the United States comparing outcomes among sepsis-related hospitalizations with versus without atrial fibrillation are limited. The aim of our study was to assess the frequency of atrial fibrillation and its impact on outcomes of sepsis-related hospitalizations.

DESIGN

Retrospective cohort study.

SETTING

The National Inpatient Sample databases (2010-2014).

PATIENTS

Primary discharge diagnosis of sepsis with and without atrial fibrillation were identified using prior validated International Classification of Diseases, 9th Edition, Clinical Modification codes.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Overall, 5,808,166 hospitalizations with the primary diagnosis of sepsis, of which 19.4% (1,126,433) were associated with atrial fibrillation. The sepsis-atrial fibrillation cohort consisted of older (median [interquartile range] age of 79 yr [70-86 yr] vs 67 yr [53-79 yr]; p < 0.001) white (80.9% vs 68.8%; p < 0.001) male (51.1% vs 47.5%; p < 0.001) patients with an extended length of stay (median [interquartile range] 6 d [4-11 d] vs 5 d [3-9 d]; p < 0.001) and higher hospitalization charges (median [interquartile range] $44,765 [$23,234-$88,657] vs $35,737 [$18,767-$72,220]; p < 0.001) as compared with the nonatrial fibrillation cohort. The all-cause mortality rate in the sepsis-atrial fibrillation cohort was significantly higher (18.4% and 11.9%; p = 0.001) as compared with those without atrial fibrillation. Although all-cause mortality (20.4% vs 16.6%) and length of stay (median [interquartile range] 7 d [4-11 d] vs 6 d [4-10 d]) decreased between 2010 and 2014, hospitalization charges increased (median [interquartile range] $41,783 [$21,430-$84,465] vs $46,251 [$24,157-$89,995]) in the sepsis-atrial fibrillation cohort. The greatest predictors of mortality in the atrial fibrillation-sepsis cohort were African American race, female gender, advanced age, and the presence of medical comorbidities.

CONCLUSIONS

The presence of atrial fibrillation among sepsis-related hospitalizations is a marker of poor prognosis and increased mortality. Although we observed rising trends in sepsis and sepsis-atrial fibrillation-related hospitalizations during the study period, the rate and odds of mortality progressively decreased.

A Simple Predictive Factor for Mortality in Fontan Surgery: Serum Hypo-Osmolality

OBJECTIVE

Close follow-up is important after the Fontan procedure, which is a palliative surgical method for a single ventricle. In this period, serum osmolality is an important parameter with the advantages of easy to obtain and poor outcome prediction.

METHODS

Patients who had undergone Fontan operation between May 2011 and February 2017 were retrospectively evaluated. Patients were divided into three groups based on their serum osmolality values: hypoosmolar (Group 1), isosmolar (Group 2), and hyperosmolar (Group 3). Demographics, clinical information and postoperative data of the groups were compared.

RESULTS

Forty-three patients had undergone extracardiac Fontan operation in the study period. There were 8, 19 and 16 patients in Groups 1, 2 and 3, respectively. Among the three groups, postoperative intubation and length of hospital stay, prolonged pleural effusion, need for inotropic support and mortality were statistically significantly higher in Group 1.

CONCLUSION

After the Fontan procedure, one of the determinants of cardiac output might be affected by serum osmolality. Decreased serum osmolality might be associated with poor prognosis after Fontan procedure. Serum osmolality monitoring may be beneficial to improve postoperative outcomes in these patients.

The use of mannitol in cardiopulmonary bypass prime solution-Prospective randomized double-blind clinical trial

BACKGROUND

The optimal prime solution for the cardiopulmonary bypass (CPB) circuit in adult cardiac surgery has not yet been defined. Mannitol is widely used in the priming solution for CPB despite the fact that there is no clear consensus on the role of mannitol in cardiac surgery. The aim of this study was to investigate the effect of mannitol in the CPB prime solution.

METHODS

This prospective, randomized, double-blind study included 40 patients with normal cardiac and renal functions, who underwent coronary artery bypass grafting. One group received a prime based on Ringer's acetate (n = 20), and the other a prime consisting of Ringer's acetate with 200 mL mannitol (n = 20). Changes in osmolality, acid-base status, electrolytes, and renal-related parameters were monitored.

RESULTS

No significant differences were found in osmolality between the Ringer's acetate group and the mannitol group at any time. The mannitol group showed a pronounced decrease in sodium, from 138.7 ± 2.8 mmol/L at anaesthesia onset, to 133.9 ± 2.6 mmol/L after the start of CPB (P < .001). No differences were seen in the renal parameters between the groups, apart from a short-term effect of mannitol on peroperative urine production (P = .003).

CONCLUSION

We observed no effects on osmolality of a prime solution containing mannitol compared to Ringer's acetate-based prime in patients with normal cardiac and renal function. The use of mannitol in the prime resulted in a short-term, significant decrease in sodium level.

Intravenous maintenance fluid tonicity and hyponatremia after major surgery- a cohort study

BACKGROUND

Intravenous maintenance fluid (IMF) tonicity and composition influence plasma electrolyte balance.

OBJECTIVE

To determine if hypotonic IMF therapy contributes to post-surgical hyponatremia.

SETTING

Single-center tertiary institution.

PARTICIPANTS

Adults who underwent major surgery and received peri-surgical IMF, with exclusive administration of hypotonic pre-mixed 0.33% saline, 5% dextrose and potassium chloride (DK0.33%S), or isotonic 0.9% saline with or without 5% dextrose (NS/DNS).

OUTCOMES AND MEASURES

We examined post-surgical hyponatremia, hypokalemia and acute kidney injury (AKI), associated with use of either IMF.

RESULTS

We studied 659 patients, of whom 161 patients (24%) developed post-surgical hyponatremia. DK0.33%S (versus NS/DNS) IMF was administered in 52% of patients who developed hyponatremia, compared to 38% of patients with stable natremia (p = 0.001). More patients with hyponatremia underwent gastrointestinal-hepatobiliary or abdominal (GI/HBS/Abd) surgery versus other surgical-sites (p = 0.001). Hypokalemia developed in 1% versus 10% of patients who received DK0.33%S and NS/DNS IMF respectively (p< 0.001), with corresponding AKI rates of 3% versus 7% (p = 0.02). On multivariate analysis, adjusted for timing of biochemistry post-surgery, IMF infusion rate and volume; independent factors associated with post-surgical hyponatremia included DK0.33%S administration, GI/HBS/Abd surgery (versus other sites), and post-surgical AKI (p < 0.05). Subgroup analysis by surgical sites showed that association of DK0.33%S administration with hyponatremia was most evident in GI/HBS/Abd surgery.

CONCLUSIONS

Administration of DK0.33%S IMF, compared with NS/DNS, is associated with post-surgical hyponatremia in adults after major surgery, but with less hypokalemia. The higher rate of AKI observed with NS/DNS IMF requires further evaluation.

Hyponatremia Predicts Poor Outcomes in Patients With Chronic Kidney Disease Undergoing Heart Operation

BACKGROUND

Preoperative hyponatremia adversely affects outcomes of cardiothoracic operation. However, in patients with chronic kidney disease, the association of sodium levels on postoperative events has never been evaluated. We investigated the impact of preoperative hyponatremia on outcomes after cardiac operation in patients with non-dialysis-dependent chronic kidney disease. Primary end points were operative mortality and acute kidney injury that required dialysis. Secondary end points were major infection and long-term survival.

METHODS

The study is observational and includes all patients with stage III to IV chronic kidney disease (non-dialysis) undergoing cardiac operation between February 2000 and January 2016. Patients were stratified into two groups by preoperative sodium levels: sodium less than 135 mEq/L and sodium of 135 mEq/L or more.

RESULTS

There were 1,008 patients (mean estimated glomerular filtration rate [GFR]: 43 ± 14 mL • min^-1 • 1.73 m^-2) with 92 patients (9%) in the low-sodium group. Patients with low sodium had higher operative mortality (p = 0.0004), need for new dialysis (p = 0.0008), and infection (p = 0.002). Predictors of operative mortality were European System for Cardiac Operative Risk Evaluation (EuroSCORE) (hazard ratio [HR] 1.03. 95% confidence interval [CI]: 1.02 to 1.05, p < 0.0001), decreasing values of sodium (HR 1.14. 95% CI: 1.07 to 1.2, p = 0.0002), and decreasing values of GFR (HR 1.01, 95% CI: 1.003 to 1.03, p = 0.007). Sodium less than 135 mEq/L was independently associated with increased need for dialysis (HR 1.3, 95% CI: 1.1 to 1.7, p = 0.0008). By linear regression, decreasing values of preoperative sodium were proportionate to the incidence of operative mortality (p < 0.0001) and need for dialysis (p < 0.0001).

CONCLUSIONS

Preoperative hyponatremia is a predictor of increased mortality and other adverse events in patients with non-dialysis-dependent chronic kidney disease undergoing cardiac operation. These findings are similar to those in hyponatremic patients without kidney disease.

Hyponatremia in Guillain-Barré Syndrome

OBJECTIVES

To evaluate incidence, risk factors, and in-hospital outcomes associated with hyponatremia in patients hospitalized for Guillain-Barré Syndrome (GBS).

METHODS

We identified adult patients with GBS in the Nationwide Inpatient Sample (2002-2011). Univariate and multivariable analyses were used.

RESULTS

Among 54,778 patients hospitalized for GBS, the incidence of hyponatremia was 11.8% (compared with 4.0% in non-GBS patients) and increased from 6.9% in 2002 to 13.5% in 2011 (P < 0.0001). Risk factors associated with hyponatremia in multivariable analysis included advanced age, deficiency anemia, alcohol abuse, hypertension, and intravenous immunoglobulin (all P < 0.0001). Hyponatremia was associated with prolonged length of stay (16.07 vs. 10.41, days), increased costs (54,001 vs. 34,125, $USD), and mortality (20.5% vs. 11.6%) (all P < 0.0001). In multivariable analysis, hyponatremia was independently associated with adverse discharge disposition (odds ratio: 2.07, 95% confidence interval, 1.91-2.25, P < 0.0001).

CONCLUSIONS

Hyponatremia is prevalent in GBS and is detrimental to patient-centered outcomes and health care costs. Sodium levels should be carefully monitored in high-risk patients.

Comparison of the incidences of hyponatremia in adult postoperative critically ill patients receiving intravenous maintenance fluids with 140 mmol/L or 35 mmol/L of sodium: retrospective before/after observational study

PURPOSE

The purpose of this study was to compare the incidences of hyponatremia in adult postoperative critically ill patients receiving isotonic and hypotonic maintenance fluids.

METHODS

In this single-center retrospective before/after observational study, we included patients who had undergone an elective operation for esophageal cancer or for head and neck cancer and who received postoperative intensive care for >48 h from August 2014 to July 2016. In those patients, sodium-poor solution (35 mmol/L of sodium; Na₃₅) had been administered as maintenance fluid until July 2015. From August 2015, the protocol for postoperative maintenance fluid was revised to the use of isotonic fluid (140 mmol/L of sodium; Na₁₄₀). The primary outcome was the incidence of hyponatremia (<135 mmol/L) until the morning of postoperative day (POD) 2.

RESULTS

We included 179 patients (Na₃₅: 87 patients, Na₁₄₀: 92 patients) in the current study. The mean volume of fluid received from ICU admission to POD 2 was not significantly different between the two groups (3291 vs 3337 mL, p = 0.84). The incidence of postoperative hyponatremia was 16.3% (15/92) in the Na₁₄₀ cohort, which was significantly lower than that of 52.9% (46/87) in the Na₃₅ group (odds ratio = 0.17, 95% confidence interval 0.09-0.35, p < 0.001]. The incidences of hypernatremia, defined as serum sodium concentration >145 mmol/L, were not significantly different between the two groups.

CONCLUSION

In this study, the use of intravenous maintenance fluid with 35 mmol/L of sodium was significantly associated with an increased risk of hyponatremia compared to that with 140 mmol/L of sodium in adult postoperative critically ill patients.

The Economic Burden of Hyponatremia: Systematic Review and Meta-Analysis

BACKGROUND

Hyponatremia is the most common electrolyte abnormality observed in clinical practice. Several studies have demonstrated that hyponatremia is associated with an increased length of hospital stay and of hospital resource utilization. To clarify the impact of hyponatremia on the length of hospitalization and costs, we performed a meta-analysis based on published studies that compared hospital length of stay and cost between patients with and without hyponatremia.

METHODS

An extensive Medline, Embase, and Cochrane search was performed to retrieve all studies published up to April 1, 2015 using the following words: "hyponatremia" or "hyponatraemia" AND "hospitalization" or "hospitalisation." A meta-analysis was performed including all studies comparing duration of hospitalization and hospital readmission rate in subjects with and without hyponatremia.

RESULTS

Of 444 retrieved articles, 46 studies satisfied the inclusion criteria, encompassing a total of 3,940,042 patients; among these, 757,763 (19.2%) were hyponatremic. Across all studies, hyponatremia was associated with a significantly longer duration of hospitalization (3.30 [2.90-3.71; 95% CIs] mean days; P < .000). Similar results were obtained when patients with associated morbidities were analyzed separately. Furthermore, hyponatremic patients had a higher risk of readmission after the first hospitalization (odds ratio 1.32 [1.18-1.48; 95% CIs]; P < .000). A meta-regression analysis showed that the hyponatremia-related length of hospital stay was higher in males (Slope = 0.09 [0.05-0.12; 95% CIs]; P = .000 and Intercept = -1.36 [-3.03-0.32; 95% CIs]; P = .11) and in elderly patients (Slope = 0.002 [0.001-0.003; 95% CIs]; P < .000 and Intercept = 0.89 [0.83-0.97; 95% CIs]; P < .001). A negative association between serum [Na(+)] cutoff and duration of hospitalization was detected. No association between duration of hospitalization, serum [Na(+)], and associated morbidities was observed. Finally, when only US studies (n = 8) were considered, hyponatremia was associated with up to around $3000 higher hospital costs/patient when compared with the cost of normonatremic subjects.

CONCLUSIONS

This meta-analysis confirms that hyponatremia is associated with a prolonged hospital length of stay and higher risk of readmission. These observations suggest that hyponatremia may represent one important determinant of the hospitalization costs.

Prevalence, Timing, Causes, and Outcomes of Hyponatremia in Hospitalized Orthopaedic Surgery Patients

BACKGROUND

Hyponatremia is common among orthopaedic patients and is associated with adverse clinical outcomes. We examined the prevalence, timing, causes, and outcomes of hyponatremia in adult hospitalized orthopaedic surgery patients.

METHODS

We evaluated the medical records of 1067 consecutive orthopaedic surgery patients admitted to a tertiary academic institution. The medical records were reviewed to investigate hyponatremia (serum sodium <135 mEq/L) that (1) had been present on hospital admission or (2) had developed postoperatively. The primary outcomes were the prevalence and timing of, and risk factors for, presentation with or development of hyponatremia. Secondary outcomes were hospital length of stay, total hospital cost, and discharge disposition. Multivariable logistic regression models were used to assess the variables associated with hyponatremia and the effects of hyponatremia on clinical outcomes.

RESULTS

Of the 1067 patients, seventy-one (7%) had preoperative hyponatremia and 319 (30%) developed hyponatremia postoperatively. Of the latter, 298 (93%) developed hyponatremia within forty-eight hours postoperatively. Compared with patients with normonatremia, those who presented with hyponatremia, on the average, were older (67.2 versus 60.5 years, p < 0.001), had longer hospital stays (4.6 versus 3.3 days, p < 0.001), incurred higher hospital costs ($19,200 versus $17,000, p = 0.006), and were more likely to be discharged to an extended-care facility (odds ratio [OR] = 2.87, p < 0.001). Developing hyponatremia postoperatively resulted, on average, in a longer hospital stay (3.7 versus 3.3 days, p = 0.002) and greater hospital cost ($18,800 versus $17,000, p < 0.001). Age (OR = 1.13 per decade, p = 0.012), spine surgery (OR = 2.76 versus knee, p < 0.001), hip surgery (OR = 1.76 versus knee, p < 0.001), and the amount of lactated Ringer solution used (OR = 1.16, p = 0.002) increased the risk of developing hyponatremia.

CONCLUSIONS

Hyponatremia in orthopaedic patients is associated with longer, costlier hospitalizations. The factors that significantly increased the risk of developing postoperative hyponatremia were an older age, spine fusion, hip arthroplasty, and the amount of lactated Ringer solution used.

Moderate-to-large increases in perioperative serum sodium concentration associated with adverse neurologic events after continuous flow left ventricular assist device implantation

OBJECTIVE

It was hypothesized that preoperative hyponatremia is associated with increased 30-day mortality after left ventricular assist device placement, and that large increases in sodium concentration are associated with adverse neurologic events and 30-day mortality.

DESIGN

Data were collected retrospectively on all patients having continuous flow left ventricular assist device implantation between January 1, 2009 and March 31, 2013. Preoperative variables, operative variables, and perioperative sodium concentrations were recorded. Both 30-day mortality and 72-hour adverse neurologic events (stroke or seizure) were recorded as primary outcome variables. Preoperative sodium and Δ sodium (postoperative sodium-preoperative sodium) were analyzed as tests for 30-day mortality and adverse neurologic events using receiver operating characteristic curves. Both crude and adjusted logistic regression analyses were used to estimate odds ratios for the outcome variables.

SETTING

Tertiary care academic medical center.

PARTICIPANTS

Patients having durable continuous flow left ventricular assist device placement.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Among 88 patients, 30-day mortality was 14% (12 of 88) and the rate of perioperative stroke or seizure was 9% (8 of 88). There were 3 strokes and 5 tonic-clonic seizures. Preoperative sodium was a poor discriminative test for 30-day mortality and stroke or seizure (AUC=0.47 and 0.57, respectively). Δ sodium was a poor discriminative test for 30-day mortality, but a fair discriminative test for stroke or seizure (AUC=0.55 and 0.78, respectively). Δ sodium was a good discriminative test for seizure alone (AUC=0.82) and a fair discriminative test for stroke alone (AUC=0.70). It also increased the odds of stroke or seizure significantly, even when adjusting for possible confounders.

CONCLUSIONS

Moderate-to-large increases in sodium concentration during left ventricular assist device placement appear to be associated with adverse postoperative neurologic events. Preoperative hyponatremia has no relationship with 30-day mortality or adverse perioperative neurologic events.

A case-control study of hyponatraemia as an independent risk factor for inpatient mortality

OBJECTIVES

Hyponatraemia is strongly associated with increased inpatient mortality, but it is unknown whether hyponatraemia per se contributes to excess mortality. Our hypothesis was that if hyponatraemic patients had significantly greater mortality compared with controls despite no difference with regard to gender, age, comorbidities and type of primary pathology, this would incriminate hyponatraemia as an independent predictor of mortality.

DESIGN

Single-centre, case-control study.

PATIENTS

Cases (N = 139) were hospitalized patients with serum Na ≤ 128 mmol/l over 3 months. Controls were 254 age- and gender-matched patients residing in the same hospital ward with serum Na > 128 mmol/l.

MEASUREMENTS

Data were collected about age, gender, comorbidities, drug history, serum creatinine, intensive care unit (ICU) admission and length of hospitalization. The main outcome measure was inpatient mortality.

RESULTS

Hyponatraemic patients had an inpatient mortality rate of 17·3% and were more than three times more likely to die during their hospital stay compared with controls (OR 3·33, 95% CI 1·68-6·58, P < 0·01) despite no statistically significant difference with respect to age, gender, comorbidities, use of common drugs, serum creatinine, ICU admission rate and length of hospitalization. Comparison of cases with the normonatraemic subgroup of controls demonstrated that cases were almost 12 times more likely to die during admission than normonatraemic controls (OR 11·89, 95% CI 2·75-51·51, P < 0·01).

CONCLUSIONS

This study showed that hyponatraemia is an independent predictor of mortality, and hyponatraemia per se is likely to contribute to excess mortality. Further studies are needed to examine whether correction of hyponatraemia can reduce mortality.