Q&A
Clinicians Are Asking: Renal Diet
Renal practitioners tackle three common questions from their primary care colleagues, including input on the renal diet.
Your renal practitioners/department editors have chosen three typical situations you might encounter in practice.
• Nutrition and diet help control kidney disease, but also heart disease, diabetes, and other comorbid states.
• Renal patients, like many others, often require surgeries; what specific concerns exist for surgical patients requiring dialysis?
• The Medicare education benefit has been a particular bonus for advanced practitioners, as we teach many of the classes.
We welcome your questions and comments.
Q: We scheduled a total knee replacement for a patient on dialysis, and anesthesia balked because the patient had a potassium level of 5.5 mEq/L. The nephrology practice, apparently not concerned, agreed to dialyze the patient, but only because anesthesia insisted. If the practice uses our facility, where 5.3 mEq/L is the upper limit of serum potassium, how can a potassium level of 5.5 mEq/L not be of concern in a hemodialysis patient?
This is a question that occurs frequently regarding patients receiving dialysis. Hyperkalemia is a problem faced by many dialysis patients as a result of the kidneys’ inability to remove potassium with the loss of renal function. Patients’ potassium levels are monitored routinely, and low-potassium diets are a staple of any nephrology clinic or dialysis unit.
For patients in our dialysis unit, the normal potassium range is 3.5 to 6.0 mEq/L, which is 0.9 mEq/L higher than for a patient without end-stage renal disease (ESRD). Dialysis patients with ESRD often have an increased tolerance for hyperkalemia.
When potassium levels are elevated, a 12-lead ECG is used to detect any physiological cardiac changes. These are generally not seen until the serum potassium exceeds 6.0 to 6.5 mEq/L. ECG changes seen in hyperkalemia include peaked T waves, a prolonged PR interval, and absent P waves with a widened QRS complex. These changes, which can lead to ventricular tachycardia or ventricular fibrillation, are not based on numbers or values of serum potassium, but are thought to reflect the transcellular potassium gradient. 3
When questioning a potassium level in a dialysis patient and considering whether presurgical dialysis is needed, it is important to consider the surgery planned. In surgeries during which potassium might be released secondary to tissue trauma, potassium levels can rise higher during surgery. 3
It is important to assess hypokalemia as well. Arrhythmias such as premature atrial and ventricular beats, sinus bradycardia, paroxysmal atrial or junctional tachycardia, atrioventricular block, and ventricular tachycardia or fibrillation can occur with hypokalemia. ECG changes include depression of the ST segment, a decrease in the amplitude of the T wave, and an increase in the amplitude of U waves, which occur at the end of the T wave. U waves are often seen in the lateral precordial leads V4 to V6. 3
Laura MacGregor, RN, MS, NP-C
Grand Street Medical Associates, Kingston, New York
REFERENCES
1. National Kidney Foundation Kidney Disease Outcome Quality Initiative (NKF-K/DOQI) Clinical Practice Guidelines for Nutrition in Chronic Renal Failure (2000). www.kidney.org/professionals/kdoqi/guidelines_updates/doqi_nut.html. Accessed February 16, 2012.
2. Medicare.gov. Medical nutrition therapy. www.medicare.gov/navigation/manage-your-health/preventive-services/medical-nutrition-therapy.aspx?AspxAutoDetectCookieSupport=1. Accessed February 16, 2012.