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Perioperative Abstinence from Cigarettes: Physiologic and Clinical Consequences R4 장 지 혜
Smoking status can affect many perioperative outcomes by contributing to the pathophysiology of diseases such as chronic obstructive pulmonary disease and atherosclerosis via the acute pharmacologic actions of smoke constituents such as carbon monoxide and nicotine All smokers requiring surgery are abstinent from tobacco for at least some period of time. These informationis of practical importance toanesthesiologists ? Clinically relevant effects on anesthetic management and periop. outocome
Mechanisms by which exposure to cigarette smoke may affect responses of patients undergoing anesthesia
Cardiovascular function • Respiratory function • Wound and bone healing • Nervous system function • Implications for periop. smoking interventions
Cardiovascular functionMechanisms of Injury and Recovery • Nicotine • Myocardial work ↑ • Sympathetic tone & catecholamines ↑ • HR, BP, myocardial contractility ↑ • Coronary vasoconstriction in pts. with coronary a. dz. • Carbon monoxide • Carboxy hemoglobin → O2 carrying capacity ↓ • Oxyhemoglobin dissociation cure : shifting to Lt. ☞ Exercise-induced angina in smokers with coronary a. dz. and frequency of ventricular arrhythmias ↑ • Cytochrome C oxidase inhibition → mitochondrial respiration ↓ • Cyanide
Cardiovascular functionMechanisms of Injury and Recovery • Promotion of atherosclerosis • endothelial injury, oxidant injury, enhanced thrombosis, and adverse effects on blood lipids. • Abstinence from cigarettes decreases cardiovascular risk. • the risk for all-cause mortality in smokers with coronary a. dz. by 1/3 • the time needed to fully realize this benefit is estimated to be at least several months. • Nicotine and carboxyhemoglobin • relatively brief half-lives (1h and 4h, respectively) • even brief cessation(i.e., over a few hours) is plausible. • Improvement in smoking related dz. such as atherosclerosis may occur more slowly.
Cardiovascular functionPerioperative Risk • Smoking may contributes to perioperative cardiac risk. • It is not clear whether status as an active smoker itselt (apart from the presence of smoking-related cardiac dz.) increases the periop. risk of cardiac events. • Most studies have been unable to identify preop. smoking status as an independent risk factor for major cardiac events during and after either cardiac or noncardiac surgery.
Cardiovascular Risk of NRT(Nicotine Replacement Therypy) • NRT is a valuable therapy for tobacco dependence. • The safety of therapeutic nicotine in pts. with cardiovascular dz. • Overwhelming evidence now supports the safety of NRT in pts. with cardiac disease. • NRT does not affect the patency of experimental coronary a. bypass grafts. • The benefits of NRT to aid pts. with coronary heart dz. stop smoking far outweigh the risk of continued smoking or NRT itself. • Other components of cigarette smoke contribute to adverse effects. • The serum concentrations of nicotine produced by NRT are less than the peak concentrations produced by cigarettes.
Respiratory FunctionMechanisms of Injury and Recovery • Smoking induces an inflammatory state in the lung. • Alveolar macrophage function is impaired in smokers compared with nonsmokers. • Impaired ability to mount an effective response to infection. • Airway epithelial structure and function are altered. • Goblet cell hyperplasia and other structural epithelial abnormalities • Increased airway smooth m. and fibrosis • Accelerated age-related decline in FEV1 • Response to inhaled bronchoconstrictors is increased, but the ability of inhaled irritants(eg. capsaicin and citric acid) to produce cough is diminished in helthy smokers. • Depletion of neuropeptides from sensory nn. responsible for cough. • Smokers become more tolerant to inhaled irritants.
Respiratory FunctionMechanisms of Injury and Recovery • Recovery process of lung with abstinence. • Symptoms of cough and wheezing decrease within weeks. • Abstinence slows the accelerated decline in FEV1 obseved. • Goblet cell hyperplasia and mucus production decreases with cessation. • Inflammatory markers decrease. • But, fibrosis, alveolar destruction and smoth m. hyperplasia may be permanent. • Mucociliary clearance seems to at least partially improve in smokers, requiring at least 1 week to show improvement.
Respiratory FunctionPerioperative Risk • Smoking status is a consistent univariate risk factor for several periop. pulmonary complications (PPCs) • Respiratory failure, unanticipated ICU admission, pneumonia, airway events during induction(cough, laryngospasm) • Excessive production of mucus itself seems to be a risk factor for PPCs. • The sensitivity of upper airway reflexes to chemical stimulants(eg. Desflurane) is increased. • Bronchial mucus transport during general anesthesia is slowed compared with nonsmokers.
Respiratory FunctionEffects of Abstinence on Risk • Prolonged abstinence from smoking decreases the risk of many PPCs. • At least 12 weeks of abstinence was needed for full benefit. • In terms of reducing PPCs, the longer the duration of abstinence is, the better, at least within the first few months of cessation.
Wound and Bone HealingPerioperative Risk and Mechanism of Injury • Smokers are more likely to have development of postop. wound-related complications. • Factors decreasing tissue oxygenation • Nicotine and corbon monoxide • via pph. vasoconstriction and impaired carrying capacity of Hb, respectively • Function of cells such as fibroblasts and immune cells • Most of these cells express nicotinic Ach receptor • Nicotine could directly inhibit cellular responses to injury. • The healing of bone may also be impaired in smokers. • Significant effects on bone metabolism • A major risk factor for osteoporosis
Wound and Bone HealingEffects of Abstinence on Risk • Preop. smoking cessation can reduce wound-related complications. • Smoking intervention goup, beginning 6-8 weeks preoperatively, has dramatically reduced relative risk for wound-related complications. • Wound infection rate were similar in the abstinence group and nonsmoker group. • Postop. Smoking behavior may also affect the risk of complication. • The rate of nonunion was approximately twice as high in pts. who continued smoking after surgery compared with non-smokers. • For smokers who quit postoperatively, their nonunion rate approached that of the non-smokers.
Risk of NRT to Wound Healing • NRT would not contribute to wound-related complications. • During NRT and smoking cessation, microvascular responses were significantly improved with before cessation. • The infection rate was not different between abstinent smokers who did or did not receive NRT. • NRT can decrease exposure to higher nicotine doses and other smoke constituents.
Nervous System FunctionMechanisms of Action and Recovery • Nicotine activates several subtypes of nicotinic acetylcholine receptors (nAChRs). • Withdrawal symptoms • When nicotine intake is reduced or eliminated. • Somatic complaint • GI Sx. Increased appetite • Affective symptoms • craving for cigarettes, depressed mood, anxiety, dysphoria • They may be manifest within hours of abstinence from nicotine and may last for several weeks. • Prevention of these Sx. may be an important motivational factor in the maintenance of smoking behavior. • Neuronal nAChRs modulate pain. • Depending on location and dose, nAChRs in CNS can have either pronociceptive or antinociceptive effects.
Nervous System FunctionPerioperative Consequences • Neuronal nAChRs are inhibited by isoflurane and propofol at clinically relevant concentrations. • The acute administration of nicotine produces a small decrease in MAC in mice. • Cigarette smoking increases both tolerance and threshold to painful stimulation. • Cigarettes is a stress management tool? • No effect of active nicotine patches on stress or nicotine withdrawal compared with placebo patches. • Withdrawal Sx. may be lessened under stressful situations that demand forced abstinence, such as military training or prisoners.
Implications for Perioperative Smoking Interventions • Chronic exposure to cigarette smoke produces profound changes in the physiology of many organ systems. • The periop. period may present unique opportunities for smokers to attempt prolonged postop. abstinenc. • NRT has proven to be both safe and effective in treating tobacco dependence, even in pts. with smoking-related dz. • The longer the duration of preop. abstinence is, the better, especially with regard to pulmonary complications. • Sustained abstinence produces tremendous benefits to the long-term health of the surgical pt.(or anyone) who smoke.