Mrs. Kalen is a 70 year old female who has arrived into the ER due to persistent vomiting for two days now. She appears to be lethargic and weak and has myalgia. She is noted to have dry mucus membranes and her capillary refill takes >4 seconds. She is diagnosed as having gastroenteritis and dehydration. Measurement of arterial blood gas shows pH 7.5, PaO2 85 mm Hg, PaCO2 40 mm Hg, and HCO3 34 mmol/L. What would you interpret the acid-base disorder to be?

Respiratory acidosis is a primary acid-base imbalance that occurs when there is an excess of carbon dioxide (CO2) in the body due to impaired ventilation or inadequate removal of CO2 from the lungs. In this case, Colleen's depressed ventilation, indicated by shallow and slow respirations, can lead to inadequate elimination of CO2 from her body. The excessive CO2 levels can result in an accumulation of carbonic acid (H2CO3) in the blood, leading to an increase in acidity and a decrease in pH.

The profuse bleeding from both ears indicates a potential head injury, which can lead to decreased neurological function and impaired control over the respiratory center in the brain. This can further contribute to depressed ventilation and the development of respiratory acidosis. Metabolic acidosis, characterized by a decrease in bicarbonate (HCO3-) levels or an increase in non-carbonic acids in the blood, is not the primary acid-base imbalance in this case since the scenario does not provide information indicating a primary metabolic disorder. Respiratory alkalosis, characterized by decreased levels of CO2 in the blood, leading to increased pH and alkalinity, is not the primary acid-base imbalance in this case. The depressed ventilation and associated increase in CO2 levels indicate the opposite, respiratory acidosis. Metabolic alkalosis, characterized by an increase in bicarbonate levels or a decrease in non-carbonic acids, is not the primary acid-base imbalance in this case as the scenario does not provide information indicating a primary metabolic disorder.

The pH value of 7.5 indicates alkalosis, as it is above the normal range of 7.35-7.45. The elevated bicarbonate (HCO3-) level of 34 mmol/L suggests metabolic alkalosis, as it is higher than the normal range of 22-28 mmol/L. The PaCO2 level of 40 mm Hg falls within the normal range of 35-45 mm Hg.

In this case, the primary disturbance is metabolic alkalosis, which is likely caused by vomiting leading to excessive loss of gastric acid (hydrogen ions) and chloride ions from the stomach. This loss of acid and chloride results in an imbalance of electrolytes and an increase in bicarbonate levels, leading to metabolic alkalosis.

The arterial blood gas results do not indicate any compensation. Compensation occurs when the body attempts to restore the pH balance by adjusting the respiratory or metabolic systems. In this case, there is no compensation observed because the PaCO2 level is within the normal range and not significantly altered.