Stopping smoking 24 hours before surgery is a mandatory safety measure designed to protect the patient from immediate risks during the procedure. This protocol is essential for reducing the likelihood of severe complications related to anesthesia and surgical stress. Smoking introduces chemicals that interfere with fundamental physiological processes, making the body less resilient during an operation. The 24-hour window allows for the clearance of the most rapidly acting compounds found in tobacco smoke, which compromise oxygen delivery, cardiovascular function, and airway health.
The Immediate Threat: Oxygen Deprivation
One of the most immediate threats posed by smoking shortly before surgery is the presence of carbon monoxide (CO) in the bloodstream. CO rapidly enters circulation and binds strongly to hemoglobin, the protein that carries oxygen in red blood cells. This binding forms carboxyhemoglobin (COHb), which effectively displaces oxygen, significantly reducing the blood’s oxygen-carrying capacity. This creates a state of functional anemia, severely compromising tissues, especially the brain and heart, which require a constant, high supply of oxygen. Since CO clears quickly, with COHb levels dropping significantly within 12 to 24 hours, this rapid clearance is the primary physiological basis for the mandatory 24-hour cessation rule.
Nicotine’s Impact on Heart Rate and Blood Pressure
Nicotine acts as a potent stimulant that directly affects the cardiovascular system. It triggers the release of stress hormones, causing an immediate increase in the patient’s heart rate and blood pressure. This cardiovascular instability is a major concern for the anesthesiologist, who relies on stable vital signs to safely manage the patient under general anesthesia. Nicotine also acts as a vasoconstrictor, narrowing blood vessels, which increases resistance and forces the heart to work harder. This stress increases the risk of cardiac events during the operation; therefore, the 24-hour period allows nicotine’s immediate stimulant effects to subside, stabilizing heart function before anesthesia.
Compromising the Lungs and Airways
Smoking acutely compromises the respiratory system, creating mechanical issues in the airways that elevate surgical risk. Smoking irritates the airways, increasing mucus production while simultaneously paralyzing the cilia, the hair-like structures responsible for clearing it. This dual effect leads to a significant accumulation of thick secretions that can clog the breathing tube used during general anesthesia, posing a direct threat to oxygen delivery. Furthermore, the irritation makes the airway hypersensitive, significantly increasing the risk of laryngospasm during intubation. While full ciliary function takes weeks to recover, a 24-hour break reduces acute irritation and mucus production, making initial anesthetic management safer.