Prevention of Dysrhythmias on the Cardiac Intensive Care Unit - Does Maintenance of High-normal Serum Potassium Levels Matter

  • End date
    Jun 28, 2023
  • participants needed
  • sponsor
    Barts & The London NHS Trust
Updated on 28 January 2021


The purpose of this study is to determine whether maintaining serum potassium levels at 3.6 mEq/L is non-inferior to normal treatment (4.5 mEq/L) on the occurrence of new onset atrial fibrillation (AF) dysrhythmia post-surgery in patients undergoing isolated coronary artery bypass graft (CABG) surgery.


At least one in three patients is affected by atrial fibrillation (AF) after cardiac surgery, with most episodes occurring in the first five postoperative days. AF occurrence is associated with increased morbidity, short and long-term mortality, intensive care unit (ICU) and hospital stay and cost of care. Persistence of these associations after adjustment for potential confounding factors suggests that they may be causal. The incidence and prevalence of AF and its associated costs are expected to increase as the surgical population ages. Extensive effort is undertaken to prevent AF after cardiac surgery from occurring, but clinical practice in this area is highly variable and the evidence base for most interventions is sparse.

Potassium plays an important role in cardiac electrophysiology. Serum potassium concentrations ([K+]) are commonly low following cardiac surgery, and appear marginally lower in those suffering atrial arrhythmias in non-surgical cohorts. Despite an absence of proof that this association is causal, efforts to maintain serum [K+] in the 'high-normal' range ( 4.5 mEq/L), as opposed to just intervening if potassium drops below its lower 'normal' threshold (<3.6 mEq/L), are considered 'routine practice' for AF prevention in post-surgical patients in many centres across the world.

From the (unpublished) data from our Tight-K Feasibility Study, all 160 patients would have required at least one dose of potassium to supplement their levels to this high-normal range and 45.5% of all serum [K+] measurements were below 4.5mEq/L at some point. Data from the same pilot study show a median number of potassium doses given in the 'tight' group (high-normal serum potassium target) of seven, compared to a median of one, with most patients not receiving any potassium supplementation at all, in the 'relaxed' group. This demonstrated for the first time ever, that the practice does achieve a separation in serum potassium levels between the two groups, so the protocol is indeed effective in achieving higher serum potassium levels.

The efficacy of the practice of maintaining high-normal serum potassium levels for the prevention of AF after cardiac surgery, however, remains unproven and data supporting it are extremely limited, being derived from observational studies rather than randomised trials. Indeed, no data exist to demonstrate that maintaining a high-normal potassium level is beneficial in these circumstances, or that aggressive replenishment of potassium in these patients improves outcome.

Meanwhile, potassium supplementation may cause discomfort or harm. Routine central venous potassium administration in the early post-operative period, when oral supplementation is not possible, is time-consuming, costly and associated with clinical risk: rapid infusion can prove fatal, and leaving central venous catheters in situ for the sole purpose of potassium replacement increases infection risk. Oral replacement (when feasible) is commonly associated with profound nausea and gastrointestinal side effects, and is very poorly tolerated by patients. The annual costs of intravenous potassium exceed those for other drugs in many cardiac surgical units due to the large quantities administered. Nursing time (e.g. for drug checks and administration) will add to this cost.

The routine maintenance of serum [K+] 4.5 mEq/L is a costly practice of unproven efficacy that is unpleasant and may be hazardous for patients. The investigators shall address this issue, performing the first appropriately powered non-inferiority multicentre randomised trial of potassium supplementation in patients undergoing coronary artery bypass surgery.

Condition Arrhythmia, Dysrhythmia
Treatment Potassium
Clinical Study IdentifierNCT04053816
SponsorBarts & The London NHS Trust
Last Modified on28 January 2021


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Inclusion Criteria

Is your age greater than or equal to 18 yrs?
Gender: Male or Female
Do you have any of these conditions: Arrhythmia or Dysrhythmia?
Do you have any of these conditions: Dysrhythmia or Arrhythmia?
Do you have any of these conditions: Arrhythmia or Dysrhythmia?
Undergoing isolated CABG surgery

Exclusion Criteria

Age <18
Previous AF
Ongoing infection/sepsis at the time of recruitment
Pre-operative high-degree atrioventricular block
Pre-operative serum K+ >5.5 mEq/L
Current/previous use of medication for the purposes of cardiac rhythm management
Dialysis-dependent end-stage renal failure
Concurrent patient involvement in another clinical trial assessing cardiac rhythm post-operative interventions
Unable to give informed consent
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