Plasma substance P concentrations in patients undergoing general anesthesia: an objective marker associated with postoperative nausea and vomiting

BACKGROUND: This study investigated plasma concentrations of substance P (SP) in patients undergoing general anesthesia (GA) and postoperative nausea and vomiting (PONV). This prospective, observational, cohort study included 23 patients who underwent scheduled surgery under general anesthesia. Blood was collected from the radial artery at predetermined time points (15–30 mins prior anesthesia, 15–30 mins after surgery/GA, and 24 h after surgery). PONV, SP concentrations, risk factors, and analgesics used were measured. FINDINGS: Nine of 23 patients experienced PONV. In patients without PONV, SP concentrations significantly decreased (P < 0.0001) at the end of surgery/GA, compared to baseline, and recovered at 24 h after surgery/GA (452.9 ± 146.2 vs. 666.9 ± 176.5 vs. 580.7 ± 168.6 pg/mL, respectively), whereas SP levels were unchanged during surgery/GA and increased at 24 hours after surgery (P = 0.020) in patients with PONV (726.1 ± 167.8 vs. 655.8 ± 168.0 vs. 779.7 ± 220.7 pg/mL, respectively). CONCLUSIONS: These finding suggest that SP levels may be utilized as an objective marker for PONV.