NBME Surgery Shelf Practice Test

Smoking exerts the strongest direct impact on the wound bed by compromising oxygen delivery and immune function. Nicotine causes vasoconstriction, reducing blood flow to the surgical site, while carbon monoxide from smoke lowers the amount of oxygen carried by red blood cells. The resulting tissue hypoxia hinders essential processes for wound healing—neutrophil killing of bacteria, collagen synthesis, and new blood vessel formation—leading to slower healing and a higher chance of infection. Although obesity, age, and sleep deprivation can influence infection risk, none affect the wound environment as profoundly as smoking does through these oxygenation and immune defects. Stopping smoking before surgery improves oxygen delivery and immune response, reducing postoperative infection risk.