Mortality rates associated with severe lactic acidosis (blood pH < 7.2) due to sepsis or low-flow states are high. Eliminating the triggering conditions remains the most effective therapy. Although recommended by some, administration of sodium bicarbonate does not improve cardiovascular function or reduce mortality. This failure has been attributed to both reduction in serum calcium concentration and generation of excess carbon dioxide with intracellular acidification. In animal studies, hyperventilation and infusion of calcium during sodium bicarbonate administration improves cardiovascular function, suggesting that this approach could allow expression of the positive aspects of sodium bicarbonate. Other buffers, such as THAM or Carbicarb, or dialysis might also provide base with fewer untoward effects. Examination of these therapies in humans is warranted. The cellular injury associated with lactic acidosis is partly due to activation of NHE1, a cell-membrane Na+/H+ exchanger. In animal studies, selective NHE1 inhibitors improve cardiovascular function, ameliorate lactic acidosis, and reduce mortality, supporting future research into their possible use in humans. Two main mechanisms contribute to lactic acid accumulation in sepsis and low-flow states: tissue hypoxia and epinephrine-induced stimulation of aerobic glycolysis. Targeting these mechanisms could allow for more specific therapy. This Acid-Base and Electrolyte Teaching Case presents a patient with acute lactic acidosis and describes current and future approaches to treatment.
CASE A 22-year-old man was brought to the ED complaining of abdominal pain after a rollover motor vehicle accident. He was the front seat passenger and was wearing a seat belt. Although he was trapped in the vehicle and it caught on fire, he did not suffer any cutaneous burns. History The patient's past medical history was significant for attention-deficit hyperactivity disorder. He admitted to using tobacco and alcohol socially, but denied illicit drug use. He denied any medication use or drug allergies. A review of systems was positive for complaints of abdominal pain and anxiety. Physical examination The patient's vital signs were: BP, 112/51 mm Hg; heart rate, 110 beats/minute; respirations, 23; SpO 2 , 95% on room air; and temperature, 37.4° C (99.3° F). On ED arrival, he was awake, alert, and oriented but appeared anxious and agitated. His pupils were equal, round, and reactive to light. His head was normocephalic with a 2-cm laceration on the left ear. The pati...
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