The aim of this study was to determine the general understanding of hyponatremia in the context of congestive heart failure through a survey of Canadian healthcare practitioners. We identified that Canadian healthcare providers appear to have a less than expected understanding of the pathophysiology and management strategies for hypervolemic hyponatremia. Trainees responded similarly or better than staff specialists in every aspect (pathophysiology and management) and while these findings were not confirmed with statistical analyses due to small sample sizes, this remains a hypothesis-generating observation.

There may be a number of possible explanations for why trainees outscored their staff counterparts in the identification and management of hyponatremia. Firstly, this may reflect the fact that most internal medicine, cardiology, and nephrology trainees are hospital-based and thus would have a reasonable familiarity with the cases presented in the survey based on patients assessed in emergency rooms and on inpatient wards. In this context, trainees may be more frequent users of current literature and therefore more aware of appropriate management strategies for hyponatremia in heart failure. Additionally, this may reflect a relatively standardized education program at the level of a clinical trainee, which further enhances the trainee’s knowledge of hyponatremia.

This study highlighted a number of knowledge gaps in the treatment of hyponatremia amongst Canadian healthcare professionals. One of the cornerstones in the management of hyponatremia is following a strict rate of sodium correction in chronic hyponatremia, but most Canadian participants failed to select the appropriate correction rate. This is concerning as inappropriate targets for sodium correction can have catastrophic consequences. Notwithstanding the low response rates, trends within the specialty groups suggest that cardiologists are more conservative than nephrologists in choosing rates of correction. The cardiologists consistently chose lower rates of sodium correction irrespective of the complexity of the patient, which may be the result of differences in education programs between specialties or variability in familiarity with the management of hyponatremia between the two groups. While the numbers selecting hypertonic saline for the management of stable hypervolemic hyponatremia were small, it is still concerning that this potentially dangerous therapy was chosen at all. Cardiologists and nephrologists were most likely to use hypertonic saline inappropriately, and trainees and general internists least likely to do so. This may be due to the fact that in many centers, the management of hyponatremia has shifted towards the realm of the general internist. In addition, trainees are expected to understand the management of hyponatremia regardless of their chosen specialty. It may be that without interval updates on current management strategies for hyponatremia, staff cardiologists, and nephrologists are more inclined to use outdated therapies than are their colleagues in general internal medicine who consult on this issue regularly. While the tendency to manage stable hyponatremia with hypertonic saline was low overall, it is apparent that Canadian healthcare providers are not in consensus on when to initiate hypertonic saline therapy (a potentially harmful and contraindicated therapy in stable hypervolemic hyponatremia), and this is a concerning fact that must be addressed. Lastly, internists and cardiologists were more inclined to opt for vaptan therapy than were other physicians. This may be a reflection of their level of comfort dealing with acutely ill patients with hyponatremia in the context of decompensated heart failure and renal dysfunction. Nephrologists may be less likely to use vaptans due to an unfamiliarity in this population as they are often consulted only once renal failure is advanced, requiring ultrafiltration to manage extracellular volume overload and concomitant hyponatremia. In addition, the relative unwillingness of trainees to opt for vaptan therapy may reflect either a detailed understanding of the literature (which to date have failed to demonstrate any hard endpoint benefit), or a lack of familiarity with this relatively novel therapy. In this situation, vaptans have not been rigorously studied and the data surrounding their use remains somewhat controversial. For this reason, it is not surprising that responses regarding the correct use of vaptans were varied.

This study would suggest that there is a need for better education surrounding the identification and management of hyponatremia in CHF; however, sample sizes were small and thus, these results may serve only as a suggestion of possible trends amongst healthcare provider subgroups. Collectively, however, these observations would imply that there remains significant uncertainty amongst Canadian healthcare providers about the etiology of hyponatremia in CHF and the management strategies for hypervolemic hyponatremia. This highlights the need not only for a structured approach to hyponatremia at the trainee level but also for ongoing educational updates throughout the span of a physician’s career, perhaps with continuing medical education (CME) credit. This may be the highest yield intervention given the observation that staff physicians scored substantially worse than did trainees who are earlier in their careers and perhaps closer to a formal education curriculum.

This study had a number of strengths, including the fact that the survey cases were designed by a team of cardiologist and nephrologists, as opposed to one person or specialist group in isolation. The cases were promoted to cardiologists, nephrologists, and general internists through various internet associations and local hospitals resources. There were a large number of respondents, and response numbers overall were large, despite small sample sizes in several subcategories.

It is important, however, to recognize that this study had a number of significant limitations. Firstly, data was compiled from the assessment of responses to a voluntary survey, which implies innate sample bias. The survey was posted to the UKidney.com website which is a learning tool for nephrologists and those with an interest in nephrology. As such, those who chose to complete the survey might be systematically different from the general medical community on the basis of being highly motivated with an underlying interest in hyponatremia and a desire to participate in a knowledge assessment survey. Alternatively, respondents may have been those with a relative deficiency in their understanding of hyponatremia and a desire to enhance their knowledge. The number of responses within individual specialities was small, and therefore, differences in responses between specialities are explorative. Furthermore, the use of multiple-choice questions as a survey tool has the potential to mislead or oversimplify responses to complex medical problems, which may modify survey results and add to response bias. Another notable limitation is that what has been determined the correct response to the survey questions was largely based on expert opinion following review by a panel of Canadian nephrologists and cardiologists. This is because in many aspects of hyponatremia management, there are no clear evidence-based guidelines, and expert opinion is all that exists to guide therapy decisions. Lastly, this survey was presented to participants as a series of three cases, each progressively more complex than the previous. There was a high attrition rate from case 1 to case 3 (which progressed in terms of complexity). While this may simply reflect a loss of interest, it also may represent unfamiliarity and a lack of confidence amongst healthcare providers when it comes to more complex cases of hyponatremia. This in itself may result in a certain degree of sample bias given that it is possible that only the most informed and confident respondents persevered through to the more difficult cases.