Effect of carboxyhemoglobin on postoperative complications and pain in pediatric tonsillectomy patients

Carbon monoxide (CO) is a product of burning solid fuel in stoves and smoking. Exposure to CO may provoke postoperative complications. Furthermore, there appears to be an association between COHb concentrations and pain. We thus tested the primary hypothesis that children with high preoperative carboxyhemoglobin (COHb) concentrations have more postoperative complications and pain after tonsillectomies, and secondarily that high-COHb concentrations are associated with more pain and analgesic use.

100 children scheduled for elective tonsillectomy were divided into low and high carbon monoxide (CO) exposure groups: COHb ≤3 or ≥4 g·dl(-1) . We considered a composite of complications during the 7 days after surgery which included bronchospasm, laryngospasm, persistent coughing, desaturation, re-intubation, hypotension, postoperative bleeding, and reoperation. Pain was evaluated with Wong-Baker Faces pain scales, and supplemental tramadol use recorded for four postoperative hours.

There were 36 patients in the low-exposure group COHb [1.8 ± 1.2 g·dl(-1) ], and 64 patients were in the high-exposure group [6.4 ± 2.1 g·dl(-1) ]. Indoor coal-burning stoves were reported more often by families of the high- than low-COHb children (89% vs 72%, P < 0.001). Second-hand cigarette smoke exposure was reported by 54% of the families with children with high COHb, but only by 24% of the families of children with low COHb. Composite complications were more common in patients with high COHb [47% vs 14%, P = 0.0001, OR:7.4 (95% Cl, lower = 2.5-upper = 21.7)], with most occurring in the postanesthesia care unit. Pain scores in postanesthesia care unit and one hour after surgery were statistically significantly lower in the low-exposure group [respectively, P = 0.020 (95%CI, lower = -1.21-upper = -0.80), P = 0.026 (95% CI, lower = -0.03-upper = 0.70)], and tramadol use increased at 4 h (3.5 (interquartile range: 0-8) vs 6 (5-9) mg, P = 0.012) and 24 h (3.5 (0-8) vs 6 (5-9) mg, P = 0.008).

High preoperative COHb concentrations are associated with increased postoperative complications and pain.