What are the causes of severe metabolic acidosis in pregnancy?

From the Guidelines

Severe metabolic acidosis in pregnancy is a life-threatening condition that requires immediate medical intervention to protect both mother and fetus, and treatment should begin with identifying and addressing the underlying cause, which may include diabetic ketoacidosis, lactic acidosis, renal failure, or toxic ingestions, as recommended by recent guidelines 1.

Key Considerations

• The management of severe metabolic acidosis in pregnancy involves a multidisciplinary approach, including obstetricians, hepatologists, and other specialists, to ensure the best possible outcomes for both mother and fetus.
• Initial management includes intravenous fluid resuscitation with isotonic crystalloids, such as normal saline, at 1-2 L over the first hour, followed by maintenance fluids based on clinical response.
• Sodium bicarbonate therapy may be considered when pH falls below 7.1 or bicarbonate is less than 12 mEq/L, though its use remains controversial.
• Insulin therapy is essential if diabetic ketoacidosis is present, starting with an IV bolus of 0.1 units/kg followed by continuous infusion at 0.1 units/kg/hour.
• Electrolyte replacement, particularly potassium, calcium, and magnesium, should be guided by serum levels.
• Continuous maternal and fetal monitoring is crucial, with arterial blood gas measurements every 2-4 hours until stabilization.

Specific Recommendations

• Women with severe metabolic acidosis in pregnancy should be managed in a monitored setting, with antihypertensive therapy using oral labetalol, nifedipine, or methyldopa, if severe hypertension is present 1.
• Magnesium sulphate should be given to women with severe metabolic acidosis in pregnancy with co-existing severe hypertension to prevent eclamptic seizures, and also as a neuroprotective agent for preterm preeclampsia if delivery is required before 32 weeks’ gestation 1.
• Corticosteroid treatment should not be given to improve maternal outcomes in severe metabolic acidosis in pregnancy, unless there is a specific indication, such as fetal lung maturity 1.
• Delivery may be necessary if maternal condition deteriorates despite treatment or if fetal distress occurs.

Monitoring and Follow-up

• Continuous maternal and fetal monitoring is crucial, with arterial blood gas measurements every 2-4 hours until stabilization.
• Serum liver tests may be measured in women with severe metabolic acidosis in pregnancy, as they are elevated in 40-50% of severe cases, and hyperemesis gravidarum-associated abnormalities are usually mild and self-limiting 1.
• Women with severe metabolic acidosis in pregnancy who have markedly raised serum liver tests should be screened for a primary liver disease 1.

From the FDA Drug Label

Dichlorphenamide treatment can cause metabolic acidosis [see Warnings and Precautions ( 5. 4)] . The effect of dichlorphenamide-induced metabolic acidosis has not been studied in pregnancy; however, metabolic acidosis in pregnancy (due to other causes) can cause decreased fetal growth, decreased fetal oxygenation, and fetal death, and may affect the fetus’ ability to tolerate labor.

Pregnant patients should be monitored for metabolic acidosis and treated as in the nonpregnant state

Newborns of mothers treated with dichlorphenamide should be monitored for metabolic acidosis because of possible occurrence of transient metabolic acidosis following birth

The use of dichlorphenamide in pregnancy may cause metabolic acidosis, which can lead to:

• Decreased fetal growth
• Decreased fetal oxygenation
• Fetal death
• Affect the fetus’ ability to tolerate labor Pregnant patients should be monitored for metabolic acidosis and treated as in the nonpregnant state 2. Newborns of mothers treated with dichlorphenamide should be monitored for metabolic acidosis because of possible occurrence of transient metabolic acidosis following birth 2.

From the Research

Definition and Treatment of Severe Metabolic Acidosis

• Severe metabolic acidosis is defined by a pH < 7.2 with HCO3- < 8 mE- q/L in plasma 3.
• The best treatment is to correct the underlying cause, but acidemia can produce multiple complications such as resistance to catecholamines, pulmonary vasoconstriction, and impaired cardiovascular function 3.
• Intravenous NaHCO3 can buffer severe acidemia, preventing associated damage and gaining time while the causal disease is corrected 3.

Administration of Sodium Bicarbonate

• The indication for sodium bicarbonate requires a risk-benefit assessment, considering complications such as hypernatremia, hypokalemia, ionic hypocalcemia, rebound alkalosis, and intracellular acidosis 3.
• Therapy must be "adapted" and administered judiciously, with monitoring of serial evaluation of the internal environment, especially arterial blood gases, plasma electrolytes, and ionized calcium 3.
• Isotonic solutions should be preferred instead of hypertonic bicarbonate, and the development of hypernatremia must be prevented 3.

Epidemiology and Management of Metabolic Acidosis

• Metabolic acidosis is a major complication of critical illness, with an incidence of 14.0% in ICU patients 4.
• Early sodium bicarbonate was given to 18.0% of patients with early metabolic acidosis, with a median dose of 110 mmol in the first 24 hours 4.
• The administration of sodium bicarbonate was associated with an adjusted odds ratio of 0.85 for ICU mortality, and may be beneficial in patients with vasopressor dependency 4.

Pathophysiology and Diagnosis of Metabolic Acidosis

• Metabolic acidosis is characterized by a primary reduction in serum bicarbonate concentration, a secondary decrease in PaCO2, and a reduction in blood pH 5.
• The calculation of the serum anion gap aids diagnosis, classifying disorders into categories of normal or elevated anion gap 5.
• Adverse effects of acute metabolic acidosis include decreased cardiac output, arterial dilatation with hypotension, and impairment of the immune response 5.

Treatment of Metabolic Acidosis

• The use of base to treat acute metabolic acidosis is controversial due to a lack of definitive benefit and potential complications 5, 6.
• The administration of base for the treatment of chronic metabolic acidosis is associated with improved cellular function and few complications 5.
• The appropriate treatment of acute metabolic acidosis, particularly organic acidosis, is cessation of acid production via improvement of tissue oxygenation 6.