Which of the following is a major advantage of using IV opioids to reduce the amount of volatile anesthetic administered during thoracic surgery?
a) Decreased postoperative Ileus
b) Decreased risk of postoperative respiratory depression and atelectasis
c) Preservation of hypoxic pulmonary vasoconstriction
d) Maintenance of sympathetic nervous system responses
e) Decreased need for neuraxial anesthesia
Answer c.
Hypoxic pulmonary vasoconstriction is largely responsible for the mammalian ability to maintain normal arterial oxygen saturation via optimization of V/Q matching. All inhalational anesthetics blunt this response (although isoflurane may cause less inhibition), and opioids may allow for less volatile agent and thus improved V/Q matching intraoperatively. Opioids also blunt autonomic responses and are often used for this reason in patients with high risk of myocardial ischemia. However, these agents do increase the risk of ileus as well as respiratory depression and atelectasis in the postoperative period. An alternative is neuraxial anesthesia, which optimizes both V/Q matching intraoperatively and postoperative analgesia and pulmonary clearance.