<prompt> A patient with salicylic acid poisoning has the following arterial blood gas analysis report: pH is 7.12 , PCO2 is 18 mm Hg HCO3 is 12 mmolL. The resulting acid-base abnormality can be best labelledMetabolic acidosis with respiratory alkalosisMetabolic acidosis with respiratory acidosisRespiratory acidosis with metabolic alkalosisMetabolic acidosis  <response>: First stepDetermine whether it is acidosis or alkalosisLow pH 7.2 means that it is acidosisSecond stepObserve HCO3- CO2 to determine the cause of acidosis or a decrease in pHDecreased PCO2 means respiratory alkalosisDecreased HCO3- means metabolic acidosisThe abnormality which is in sync with the change in pH, i.e., the abnormality which is causing acidosis is decreased HCO3- So, the primary abnormality in the case is metabolic acidosisThird stepThe third step requires determining whether the patients compensation is appropriate or not.Refer to the tableChange in HCO3- 12 mmol LExpected change in PCO2 1.25 x 12 mmol 15 for 12 mmol change in HCO3- PaCO2 is expected to decrease 1.25 mm Hg for each mmolL decrease in HCO3-Thus, the decrease in PCO2 is more than the expected. This suggests that there must be coexisting respiratory alkalosis, which causes more than the expected decrease in PCO2. 