A male client with a massive pulmonary embolus is tachycardic, hypotensive, and has audible bilateral pulmonary crackles. His arterial blood gas (ABG) results are: pH 7.0: PaCO, 66 mm Fig; HCO3- 24 mEq/L (24 mmol/L); PaO, 60 mm Hg. Based on these findings, this client is at greatest risk for which pathophysiological condition? Reference Ranges: pH [7.35 to 7.45] PaCO, [35 to 45 mm Hg] HCO3- [21 to 28 mEq/L (21 to 28 mmol/L)] PaO, [80 to 100 mm Hg]