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

The TIGHT-K STUDY. Prevention of Dysrhythmias on the Cardiac Intensive Care Unit - Does Maintenance of High-normal Serum Potassium Levels Matter

The purpose of this study is to determine whether a strategy of maintaining serum potassium levels at ≥3.6 mEq/L is non-inferior to a strategy of usual treatment (≥4.5 mEq/L) on the occurrence of new onset atrial fibrillation after cardiac surgery (AFACS) in patients undergoing isolated coronary artery bypass graft (CABG) surgery.

Study Overview

• Status: Active, not recruiting
• Conditions: Arrhythmias, Cardiac
• Intervention / Treatment: Drug: Potassium

Detailed Description

At least one in three patients is affected by atrial fibrillation after cardiac surgery(AFACS), 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From the (unpublished) data from our Tight-K Feasibility Study, all 160 patients would have required at least one dose of potassium to supplement their levels to this high-normal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.

• Study Type: Interventional
• Enrollment (Actual): 1684
• Phase: Phase 3

Contacts and Locations

• Study Contact: Name: Professor Ben O'Brien; Phone Number: 0207 927 2505; Email: benobrien@doctors.org.uk
• Study Contact Backup: Name: Zahra Jamal; Phone Number: 0207 927 2505; Email: tightk@lshtm.ac.uk

Study Locations

• United Kingdom
  • London
    • London Borough of Sutton, London, United Kingdom, EC1A 7DN
      • Barts Health NHS Trust

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Scheduled to have isolated CABG surgery
• Patient in sinus rhythm

Exclusion Criteria:

• Age less than 18 years
• Previous history of Atrial Fibrillation, Atrial Flutter and/or Atrial Tachyarrhythmia
• Pre-operative high-degree atrioventricular (AV) block (defined as Mobitz type 2 second degree AV block or complete heart block)
• Pre-operative serum [K+] greater than 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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Tight control; Patients randomised to the 'Tight' group will receive potassium supplementation if their serum potassium falls below 4.5 mEq/L (current practice).	Drug: Potassium; The trial treatment will start when patients are admitted to the intensive care unit after their surgery. The patient will undergo regular blood investigations, as per current practice. The frequency of K+ monitoring while on ICU will be according to clinician / nursing staff preference. Potassium supplementation will be according to local hospital protocols. This can be either via an intravenous infusion or as a tablet. Patients will otherwise be treated as per current hospital protocol.
Experimental: Relaxed control; Those randomised to the 'Relaxed' Group will receive potassium supplementation only if their serum potassium drops below 3.6 mEq/L.	Drug: Potassium; The trial treatment will start when patients are admitted to the intensive care unit after their surgery. The patient will undergo regular blood investigations, as per current practice. The frequency of K+ monitoring while on ICU will be according to clinician / nursing staff preference. Potassium supplementation will be according to local hospital protocols. This can be either via an intravenous infusion or as a tablet. Patients will otherwise be treated as per current hospital protocol.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The presence of new onset AFACS until until hour 120 after initial admission to ICU/post-operative care facility, or discharge from hospital, whichever occurs first.	Episode of AFACS lasting ≥30 seconds that is both clinically detected and electrocardiographically confirmed (on either a 12-lead electrocardiogram (ECG), telemetry or Holter monitoring	Maximum of 5 days

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
In-patient mortality		Maximum 6 months
6-month mortality		Maximum 6 months
Critical care length of stay	Number of days patients are in inpatients in critical care	Maximum 6 months
Hospital length of stay	Number of days patients are inpatients in all hospital wards	Maximum 6 months
Costs relating to potassium therapy	Financial cost of administering potassium therapy to patients	Maximum of 5 days
Quality of life at 6 months: questionnaire	Quality of life questionnaire(EQ-5D-5L) administered before surgery and at 6 month follow up	6 months
The incidence of new onset AFACS	Detected on Holter monitor until hour 120 after initial admission to ICU/post-operative care facility or discharge from hospital, whichever occurs first.	Maximum of 5 days
The incidence of at least one episode of AFACS	Clinically identified AFACS or Holter-identified AFACS until hour 120 after initial admission to ICU/post-operative care facility or discharge from hospital, whichever occurs first.	Maximum of 5 days
Number of patients experiencing at least one episode of a non-AF arrhythmia.	Identified on Holter monitor until hour 120 after after initial admission to ICU/post-operative care facility or discharge from hospital, whichever occurs first	Maximum of 5 days

Collaborators and Investigators

• Sponsor: Barts & The London NHS Trust
• Collaborators: London School of Hygiene and Tropical Medicine; King's College Hospital NHS Trust; The Leeds Teaching Hospitals NHS Trust; Nottingham University Hospitals NHS Trust; Guy's and St Thomas' NHS Foundation Trust; Sheffield Teaching Hospitals NHS Foundation Trust; Mid and South Essex NHS Foundation Trust; Liverpool Heart and Chest Hospital NHS Foundation Trust; University Hospitals Bristol and Weston NHS Foundation Trust; Hull University Teaching Hospitals NHS Trust; Oxford University Hospitals NHS Trust; St George's University Hospitals NHS Foundation Trust; German Heart Institute; Royal Sussex County Hospital; Royal Infirmary of Edinburgh; Wythenshawe Hospital; Blackpool Victoria Hospital; Hammersmith Hospitals NHS Trust; Golden Jubilee National Hospital; Aberdeen Royal Infirmary; Derriford Hospital; Freeman Health System; Universität Münster

Study record dates

Study Major Dates

• Study Start (Actual): October 20, 2020
• Primary Completion (Actual): November 22, 2023
• Study Completion (Estimated): May 1, 2024

Study Registration Dates

• First Submitted: August 9, 2019
• First Submitted That Met QC Criteria: August 12, 2019
• First Posted (Actual): August 13, 2019

Study Record Updates

• Last Update Posted (Actual): February 20, 2024
• Last Update Submitted That Met QC Criteria: February 16, 2024
• Last Verified: February 1, 2024

More Information

Terms related to this study

• Keywords: cardiac surgery; atrial fibrillation; potassium; cardiovascular; coronary artery bypass grafting; potassium supplementation
• Additional Relevant MeSH Terms: Pathologic Processes; Heart Diseases; Cardiovascular Diseases; Arrhythmias, Cardiac
• Other Study ID Numbers: 260639

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No