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4. Metabolic gap and non gap acidosis, respiratory acidosis; increase TV

The Henderson-Hasselbalch equation (pH=6.1 + log [HCO3⁻/0.03 X pCO2]) shows H+ = 65, consistent with a pH of 7.18
Metabolic acidosis by ABG with an anion gap ([Na⁺] − [Cl⁻ + HCO₃⁻]) of 10 but when adjusted for albumin (2.5 decrease in anion gap for every gram drop in albumin below 4) the normal anion gap is decreased to approximately 4 and therefore the anion gap is elevated.
Delta ratio ([measured anion gap - normal anion gap] / [24 - HCO₃⁻]) of approximately 0.6 also shows a non anion gap metabolic acidosis. A delta ratio below 1 indicates a greater fall in [HCO3-] than one would expect given the increase in the anion gap. This can be explained by a mixed metabolic acidosis, i.e., a combined elevated anion gap acidosis and a normal anion gap acidosis.
Winter’s formula (expected pCO2= [1.5 X HCO3^-] + 8) shows an expected pCO2 of 29 which is lower than the measured 38 suggesting a coexisting respiratory acidosis.
Increasing the TV with his existing RR of 40 will increase ventilation to maximize ventilator correction of his respiratory acidosis until the metabolic acidosis can be corrected. You must carefully monitor the peak and plateau pressures as this patient would be at high risk for pneumothorax.

What would be reasonable empiric antibiotic coverage for this patient? (click on correct answer to move to next panel)