Prevalence, risk factors, and complications associated with hyponatraemia following elective primary hip and knee arthroplasty

Abstract

Background Hyponatraemia, defined as a serum sodium [Na] concentration below 135 mmol/L, is common following surgery. As inpatient peri-operative stays shorten, there is a need to recognise pre-operative risk factors for post-operative hyponatraemia and complications associated with a peri-operative drop in Na. This audit aimed to investigate the prevalence of, risk factors for, and complications associated with hyponatraemia following elective primary hip and knee arthroplasty. Methods Data were collected within a retrospective audit of inpatient complications and unplanned reattendance or readmission at hospital in consecutive elective primary hip and knee arthroplasty patients in a single high throughput elective primary joint unit. The hospital’s electronic database identified 1000 patients who were admitted electively between February 2012 and June 2013 under the care of a single consultant orthopaedic surgeon for either total hip arthroplasty, total knee arthroplasty, or uni-compartmental knee arthroplasty. Groups were compared using appropriate tests, including chi-square analysis (or Fisher’s exact test), Mann-Whitney U test, Kruskal-Wallis test, and Wilcoxin signed-rank test. Logistic regression analysis was used to determine factors associated with hyponatraemia. Results Of the total 1000 patients, 217 (21.7%) developed post-operative hyponatraemia. Of these, 177 (81.6%) had mild (Na 130–134 mmol/L), 37 (17.1%) had moderate (Na 125–129 mmol/L), and 3 (1.4%) had severe (Na < 125 mmol/L) hyponatraemia. In multivariate analysis, age, pre-operative Na, and fasting glucose on day 1 remained significantly associated with having hyponatraemia post-operatively. There were no significant differences in reattendance at emergency departments and/or readmission within 90 days between those who had post-operative hyponatraemia whilst in hospital (39/217 = 18.0%) and those who did not (103/783 = 13.2%), or between those who were discharged with hyponatraemia (18/108 = 16.7%) and those discharged with normal Na (124/880 = 14.1%). Conclusion Approximately one fifth of elective joint arthroplasty patients had post-operative hyponatraemia. In these patients, older age, lower pre-operative Na and higher fasting glucose predicted post-operative hyponatraemia. We found no evidence that those discharged with hyponatraemia had more reattendance at emergency departments or readmission to hospital. We suggest that otherwise well patients with mild hyponatraemia can safely be discharged and followed up in the community.

Hyponatremia Is an Overlooked Sign of Trouble Following Total Joint Arthroplasty

“…This was consistent for both primary and revision TJA. While Macdonald et al found that postoperative hyponatremia was not independently associated with increased LOS or 90-day readmission 24 , multiple studies have found hyponatremia to adversely affect perioperative outcomes 5,10,17,18 .…”

“…With advancements in perioperative protocols and the push toward less frequent laboratory evaluation 13 , it is important to identify individuals who are at risk for electrolyte disturbances following TJA. Previous studies have identified several risk factors for postoperative hyponatremia, including older age, lower preoperative sodium levels, the use of diuretics, longer operative time, greater blood loss, and greater comorbidities 5,6,10,17 . Consistent with these findings, the present study identified older age, the use of general anesthesia, higher CCI, congestive heart failure, and chronic kidney disease, among others, as risk factors for postoperative hyponatremia.…”

“…A few prior studies have examined perioperative hyponatremia and its association with clinical outcomes following TJA 4,5,7,9,10,[16][17][18][19][20][24][25][26] . Four of those studies utilized large registry databases that, despite including larger cohorts, most likely had inherent biases because hyponatremia was identified using ICD codes as opposed to the actual laboratory measurements [18][19][20]25 .…”

“…In addition, other studies have reported that hyponatremia leads to increased LOS and readmission rates, which consequently increase health-care costs 10,15 . Nevertheless, relatively few studies have evaluated the impact of hyponatremia in orthopaedic sur-gery 6,10,[16][17][18] . Even fewer studies have investigated the association between the preoperative-to-postoperative change in sodium level and perioperative outcomes 9 .…”

Oral Hydration Before and After Hip Replacement: The Notion Behind Every Action

“… 1 The undesirable high rates of fluid disturbances in hip surgery mirror this hesitation. 2 - 4 We know that the extent of pre-existing conditions 5 or their chronicity 6 is an important forecaster for a fraction of postoperative events like hyponatremia. However, in the current era of perioperative medicine where everything should be enclosed by recommendations, each blind spot undermines the efficiency of the system, and it is thus time to recall the concept behind fluid administration.…”