A client with a bowel obstruction is experiencing intractable vomiting for the last several hours despite the administration of prescribed antiemetics. The nurse obtains the client's arterial blood gas (ABG) results which identify a pH of 7.50, a PaCO2 of 42 mm Hg, and an HCO3 of 33 me/L (33 mmol/L). The nurse should interpret these results as confirming which acid-base imbalance?