How is metabolic acidosis managed in pregnancy?

Management of Metabolic Acidosis in Pregnancy

The management of metabolic acidosis in pregnancy requires immediate identification of the underlying cause, with treatment prioritizing rapid correction through intravenous dextrose-containing fluids for starvation ketoacidosis (the most common cause in pregnancy) or sodium bicarbonate for severe acidosis (pH <7.2), while simultaneously considering emergent delivery if maternal stabilization fails or fetal distress develops. 1, 2, 3

Immediate Assessment and Stabilization

Identify the Underlying Cause

The first critical step is determining the etiology of metabolic acidosis, as pregnancy creates unique vulnerabilities:

• Starvation ketoacidosis is the most common cause in pregnancy and can develop after only 12-14 hours of inadequate oral intake due to pregnancy-induced insulin resistance and enhanced lipolysis 2, 3
• Check serum and urine ketones, blood glucose, lactate, and calculate the anion gap 2, 3
• Consider diabetic ketoacidosis (occurs at lower glucose thresholds in pregnancy), lactic acidosis from shock/dehydration, drug intoxications, and renal failure 1, 4
• Critical pitfall: Pregnant patients with severe metabolic acidosis often appear clinically well despite profound biochemical derangements, leading to delayed recognition 3

Assess Severity

• Severe metabolic acidosis is defined as pH <7.2, base deficit >10 mmol/L, or bicarbonate <12 mmol/L 5
• Obtain arterial blood gas, electrolytes, and continuous fetal monitoring 1, 6
• Metabolic acidosis threatens fetal neural development, intelligence, and can cause fetal demise 2

Treatment Algorithm

For Starvation Ketoacidosis (Most Common)

Administer intravenous dextrose-containing fluids immediately as first-line therapy:

• Start 5-10% dextrose in normal saline or lactated Ringer's solution 2, 3
• Add thiamine (100 mg IV) and folic acid before dextrose administration to prevent Wernicke's encephalopathy 2
• Acidosis typically resolves rapidly (within hours) with dextrose administration alone 2, 3
• Continue dextrose infusion until oral intake is adequate and ketones clear 3

For Severe Metabolic Acidosis (pH <7.2)

Sodium bicarbonate is indicated when rapid correction is crucial:

• Initial dose: 1-2 ampules (44.6-100 mEq) IV push in cardiac arrest, or 2-5 mEq/kg over 4-8 hours for less urgent situations 1
• Monitor arterial pH, blood gases, and plasma osmolarity closely 1
• Important caveat: Avoid overcorrection in the first 24 hours—target total CO2 of approximately 20 mEq/L rather than complete normalization, as ventilatory compensation lags behind and can cause rebound alkalosis 1
• Bicarbonate solutions are hypertonic and may cause hypernatremia, but in severe acidosis the benefits outweigh this risk 1

For Specific Etiologies

• Diabetic ketoacidosis: Insulin therapy is the primary treatment, with bicarbonate reserved for pH <7.0 1
• Lactic acidosis from shock: Restore blood volume and tissue perfusion first 1
• Drug intoxications: Bicarbonate promotes urinary alkalinization for salicylates and barbiturates 1

Delivery Considerations

Emergency delivery may be both life-saving for the mother and the only way to deliver a viable infant:

• If maternal acidosis fails to improve rapidly with medical management, proceed with emergent delivery 6
• Severe metabolic acidosis often resolves dramatically immediately after delivery, suggesting the pregnancy itself contributes to the metabolic derangement 6
• Delivery should be considered when maternal stabilization is not achieved or fetal distress develops 6
• However, with prompt recognition and appropriate therapy (especially dextrose for starvation ketoacidosis), emergency cesarean section can often be avoided 3

Monitoring During Treatment

• Serial arterial blood gases every 1-2 hours until stabilized 1
• Continuous fetal heart rate monitoring 6
• Serum electrolytes, particularly potassium (may shift with correction) 1
• Blood glucose monitoring 2, 3
• Urine and serum ketones to guide therapy duration 2, 3

Prevention of Recurrence

• Ensure adequate caloric intake throughout pregnancy, particularly during periods of nausea/vomiting 3
• Educate patients that even short periods of fasting (12-14 hours) can precipitate ketoacidosis in pregnancy 3
• Stressful situations (acute illness, medications like beta-agonists for tocolysis, corticosteroids) can accelerate and worsen acidosis 4, 7
• Provide antiemetics aggressively for hyperemesis gravidarum 3

Special Populations

Preterm Infants (if delivery occurs)

• Avoid excessive chloride intake in parenteral nutrition, as cumulative chloride >3.3 mmol/kg/day can induce metabolic acidosis 5
• Use "chloride-free" sodium and potassium solutions when possible 5