How to manage metabolic acidosis with impaired renal function in an elderly patient?

From the Guidelines

Managing metabolic acidosis in this 97-year-old male patient with impaired renal function (GFR 49) requires careful consideration of the underlying cause and avoidance of further kidney damage, with a focus on treating the condition while monitoring serum bicarbonate concentrations to ensure they do not exceed the upper limit of normal, as per the KDIGO 2024 clinical practice guideline 1. Given the patient's CO2 level of 18 and anion gap of 20, indicating metabolic acidosis, and considering the impaired renal function (Cr 132 and GFR 49), the management approach should prioritize correcting the acidosis while being cautious of the patient's renal status.

• Initial steps should involve identifying and treating the underlying cause of the metabolic acidosis, such as reviewing medications that could be contributing to the condition (e.g., NSAIDs, certain antibiotics, metformin) and adjusting or discontinuing them as necessary.
• Dietary modifications are crucial, including increasing the consumption of fruits and vegetables, which can help improve the acid-base balance, and limiting animal protein intake, which can exacerbate acidosis.
• Sodium bicarbonate therapy may be considered, especially if the serum bicarbonate level is significantly low, typically below 16-18 mEq/L, with the aim of correcting the acidosis without overcorrecting, as emphasized by the KDIGO guideline 1.
• The dose of sodium bicarbonate should be carefully selected, often starting with oral sodium bicarbonate 650 mg three times daily, with adjustments based on the patient's response and regular monitoring of electrolytes, renal function, and acid-base status.
• For severe acidosis (pH < 7.2), intravenous sodium bicarbonate may be necessary, but this should be done with close monitoring due to the potential risks, especially in a patient with impaired renal function.
• Regular monitoring and follow-up are essential, with initial assessments every 1-2 days, then weekly to monthly, depending on the patient's stability and response to treatment.
• Considering the patient's age and the complexity of managing metabolic acidosis with impaired renal function, consultation with a nephrologist is recommended to ensure the best possible outcomes and to adjust the treatment plan as necessary, based on the most recent and highest quality evidence available, such as the KDIGO 2024 guideline 1.

From the FDA Drug Label

In less urgent forms of metabolic acidosis, Sodium Bicarbonate Injection, USP may be added to other intravenous fluids The amount of bicarbonate to be given to older children and adults over a four-to-eight-hour period is approximately 2 to 5 mEq/kg of body weight - depending upon the severity of the acidosis as judged by the lowering of total CO2 content, blood pH and clinical condition of the patient In metabolic acidosis associated with shock, therapy should be monitored by measuring blood gases, plasma osmolarity, arterial blood lactate, hemodynamics and cardiac rhythm. Bicarbonate therapy should always be planned in a stepwise fashion since the degree of response from a given dose is not precisely predictable

The patient has metabolic acidosis with a CO2 level of 18 and an anion gap of 20, and impaired renal function with a creatinine level of 132 and a GFR of 49.

• The dose of sodium bicarbonate should be 2 to 5 mEq/kg of body weight over a period of 4 to 8 hours, depending on the severity of the acidosis.
• Monitoring of blood gases, plasma osmolarity, arterial blood lactate, hemodynamics, and cardiac rhythm is necessary.
• Stepwise therapy should be planned, as the degree of response from a given dose is not precisely predictable.
• It is unwise to attempt full correction of the low total CO2 content during the first 24 hours of therapy, as this may be accompanied by an unrecognized alkalosis.
• The goal is to achieve a total CO2 content of about 20 mEq/liter at the end of the first day of therapy, which will usually be associated with a normal blood pH 2.

From the Research

Metabolic Acidosis Management in Elderly Patients with Impaired Renal Function

The patient's laboratory results show a CO2 level of 18 and an anion gap of 20, with a creatinine level of 132 and a GFR of 49. This indicates the presence of metabolic acidosis with impaired renal function.

• The patient's GFR is 49, which is below the normal range, indicating impaired renal function 3.
• Metabolic acidosis is common in patients with chronic kidney disease (CKD) and can lead to poor outcomes such as bone demineralization, muscle mass loss, and worsening of renal function 4.
• The treatment of metabolic acidosis in CKD patients usually involves oral bicarbonate supplementation to maintain serum bicarbonate levels within the normal range 4.
• However, the administration of base aimed at normalization of plasma bicarbonate concentration might be associated with certain complications, such as volume overload, exacerbation of hypertension, and facilitation of vascular calcifications 5.
• A low-potassium diet is recommended for patients with GFR less than 20 ml/min, or GFR less than 50 ml/min if drugs that raise serum potassium are taken 3.
• Limitation of daily protein intake to less than 1 g/kg/day is also useful in managing metabolic acidosis in CKD patients 3.

Considerations for Elderly Patients

• Elderly patients with CKD are more prone to developing metabolic acidosis due to decreased renal function and other age-related factors 6.
• The therapeutic approach should be aimed at early correction of concurrent clinical problems, such as fluids and hemodynamic optimization, in parallel to the formulation of a diagnosis 7.
• The administration of alkalizing agents should be carefully evaluated, taking into account the risk of side effects, as well as the potential need for renal replacement therapy 7.

Monitoring and Treatment

• Regular monitoring of the patient's serum bicarbonate levels, electrolytes, and renal function is essential to manage metabolic acidosis effectively 3, 4.
• The use of diuretics, such as loop diuretics, may be effective in managing volume overload in CKD patients, but should be used with caution in elderly patients due to the risk of dehydration and electrolyte imbalances 3.