Preoperative Potassium Test

Before undergoing anesthesia, patients must have a preanesthesia assessment to evaluate their medical conditions, perioperative risk, and readiness for the procedure, which will inform the development of an anesthetic plan. The goals of this evaluation are to assess the patient’s medical status, minimize anesthesia and surgery risks, and prepare them for the procedure. Preoperative testing should be done selectively and should consider the patient’s medical status, the planned procedure, and the potential impact of test results on management or risk assessment. Testing is recommended when abnormal results are suspected based on clinical risk factors and when results can influence decision-making regarding surgery, medication, type of surgery, anesthetic technique, monitoring, postoperative care, or perioperative risk profile. One preoperative test that can be invaluable is a potassium test.

It is valuable to consider obtaining a metabolic panel, which offers insights into the body’s electrolyte status, including sodium, potassium, and calcium levels. These electrolytes play pivotal roles in physiological processes. Potassium, especially, is crucial for maintaining cellular polarization and ensuring the transmission of electrical impulses through the myocardium. Any imbalance between intracellular and extracellular potassium concentrations can lead to severe arrhythmias. Patients at higher risk of electrolyte abnormalities include those with alcohol abuse, anasarca, low body mass index (e.g., anorexia nervosa), known cardiac arrhythmias, heart failure, severe shortness of breath, inflammatory bowel disease, malabsorption, malnutrition, syncope, and renal disease. Furthermore, patients taking specific medications, such as digoxin and diuretics, may also be predisposed to electrolyte imbalances.

High potassium levels, called hyperkalemia, often stem from impaired urinary potassium excretion due to acute or chronic kidney disease, disorders, or medications that inhibit the renin-angiotensin-aldosterone axis. The most serious effects of hyperkalemia include muscle weakness or paralysis, cardiac conduction issues, and arrhythmias. These symptoms usually arise when serum potassium levels reach ≥7.0 mEq/L in chronic cases or possibly at lower levels when the increase in serum potassium is sudden. On the other hand, hypokalemia, or low potassium levels, can result from potassium entering cells or more commonly from losses through vomiting, diarrhea, or diuretic use. Symptoms of hypokalemia include severe muscle weakness, rhabdomyolysis, cardiac arrhythmias, kidney problems, and glucose intolerance. These symptoms typically appear when serum potassium falls below 3.0 mEq/L.

The effects of hyper- or hypokalemia can impact the safety and outcomes of a procedure. A multi-center study conducted by Wahr et al. investigated the prevalence and correlation of potassium abnormalities with adverse perioperative outcomes. The study included prospective data from 2402 patients undergoing elective coronary artery bypass grafting. Among these patients, 1290 (53.7%) experienced perioperative arrhythmias, with 238 (10.7%) having intraoperative arrhythmias, 329 (13.7%) experiencing postoperative nonatrial arrhythmias, and 865 (36%) developing postoperative atrial flutter or fibrillation. A serum potassium level below 3.5 mmol/L was identified as a predictor of serious perioperative arrhythmias, intraoperative arrhythmias, and postoperative atrial fibrillation/flutter, even after adjusting for confounding factors. Another study by Shah et al. examined 688 consecutive patients over 70 years old with cardiac disease undergoing noncardiac surgery. They found that hypokalemia was an independent predictor of mortality. These studies highlight the association between hypokalemia and serious arrhythmias, suggesting that a preoperative potassium test in patients with known ischemic heart disease can help identify those at increased risk of adverse outcomes. Delaying surgery until normal potassium levels are restored, when electrolyte abnormalities are detected during perioperative tests, could improve patient outcomes.

Preoperative evaluation is essential for assessing patients’ readiness for surgery and minimizing perioperative risks. Clinicians must balance the added information and potential safety impacts provided by obtaining a preoperative potassium test with the cost and time of doing so. Understanding the association between electrolyte imbalances and adverse outcomes can help clinicians identify high-risk patients, obtain testing as needed, and optimize preoperative management, potentially improving surgical outcomes and patient safety.

References

Wahr JA, Parks R, Boisvert D, Comunale M, Fabian J, Ramsay J, Mangano DT. Preoperative serum potassium levels and perioperative outcomes in cardiac surgery patients. Multicenter Study of Perioperative Ischemia Research Group. JAMA. 1999 Jun 16;281(23):2203-10. doi: 10.1001/jama.281.23.2203. PMID: 10376573.

Sanjay OP. pre-operative serum potassium levels and peri-operative outcomes in patients undergoing cardiac surgery. Indian J Clin Biochem. 2004 Jan;19(1):40-4. doi: 10.1007/BF02872387. PMID: 23105424; PMCID: PMC3453902.

Arora P, Pourafkari L, Visnjevac O, Anand EJ, Porhomayon J, Nader ND. Preoperative serum potassium predicts the clinical outcome after non-cardiac surgery. Clin Chem Lab Med. 2017 Jan 1;55(1):145-153. doi: 10.1515/cclm-2016-0038. PMID: 27107837.

Shah KB, Kleinman BS, Rao TL, Jacobs HK, Mestan K, Schaafsma M. Angina and other risk factors in patients with cardiac diseases undergoing noncardiac operations. Anesth Analg. 1990 Mar;70(3):240-7. doi: 10.1213/00000539-199003000-00002. PMID: 2305974.

Montford JR, Linas S. How Dangerous Is Hyperkalemia? J Am Soc Nephrol. 2017 Nov;28(11):3155-3165. doi: 10.1681/ASN.2016121344. Epub 2017 Aug 4. PMID: 28778861; PMCID: PMC5661285.

Montague BT, Ouellette JR, Buller GK. Retrospective review of the frequency of ECG changes in hyperkalemia. Clin J Am Soc Nephrol. 2008 Mar;3(2):324-30. doi: 10.2215/CJN.04611007. Epub 2008 Jan 30. PMID: 18235147; PMCID: PMC2390954.

Krijthe BP, Heeringa J, Kors JA, Hofman A, Franco OH, Witteman JC, Stricker BH. Serum potassium levels and the risk of atrial fibrillation: the Rotterdam Study. Int J Cardiol. 2013 Oct 15;168(6):5411-5. doi: 10.1016/j.ijcard.2013.08.048. Epub 2013 Aug 24. PMID: 24012173.