Smoking And Anaesthesia

Dr Gunjan Badwaik

Consultant Anaesthesiologist
Nagpur

Introduction:

WHO has described tobacco as ‘the only legal drug that kills many of its users when used exactly as intended by manufacturers’.[1] Smoking increases the risk of perioperative morbidity and mortality in a dose-dependent manner. Quitting smoking before surgery leads to a reduced incidence of postoperative complications. The longer the period of cessation before surgery, the greater the benefit.
The National Survey on Drug Use and Health (NSDUH) defined a current smoker as one who confessed smoking part or all of a cigarette during the 30 days preceding the interview and consumed >100 cigarettes in his life time [2]. Light smoker: A smoker who confessed consuming between 1 and 10 cigarettes per day. Moderate smoker: A smoker who confessed consuming between 11 and 19 cigarettes per day. Heavy smoker: A smoker who consumes 20 cigarettes or more per day. Out of almost 4500 toxic substances in cigarette smoke, Nicotine and CO are the two toxic substances which are most undesirable. Electronic nicotine delivery systems or E cigarettes do not burn tobacco but instead vaporise nicotine solution and hence equally dangerous. As Passive smoking or second‑hand smoking is unintentional inhalation, smokes are unfiltered, contain more carcinogenic and irritant materials and possess a greater health hazard than active smoking. So history suggestive of passive smoking should be asked by anaesthesiologist. Hukka contain more nicotine (2%–4% vs. 1%–3%) and higher CO concentration (0.34%–1.4% vs. 0.41%) than cigarette.

When to stop smoking before surgery?

There is an ill‑founded study that stopping smoking shortly before surgery may increase complications [3]. However, a recent meta‑analysis concludes no such association.[4] Quitting smoking at any time before or after surgery is always beneficial for the patients.[5] Stopping smoking even for 1 day before surgery helps in improving tissue oxygen delivery by reducing the carboxyhaemoglobin (COHb) levels and shifting the oxygen dissociation curve to the right. The half‑life of nicotine and COHb are 30–60 min and 4–6 h, respectively.[6] However, to reduce the volume of sputum production, smoking cessation of at least for 1–2 weeks is needed.[6] Abstinence of at least 3–4 weeks is needed to reduce complications related to wound healing.[7] Most investigators suggest that stopping smoking 2 months before surgery provides the maximum benefit.[9]

Systemic Effects of Smoking:

Cardiovascular system
Nicotine stimulates the adrenal medulla to secrete adrenaline which stimulates the sympathetic system. The resultant increases in heart rate, blood pressure, contractility and peripheral vascular resistance imbalances the myocardial oxygen supply‑demand ratio which makes the heart vulnerable for ischaemic damage.[10]

Respiratory system
The irritants and ciliotoxins present in tobacco smoke increases mucous production and weakens the mucus clearance mechanism in the tracheobronchial tree.[11] This leads to clogging of the lungs with hyper‑viscous thick mucus secretion, bacteria and dead cells making lungs vulnerable to various infections.[12] An increase in proteolytic and elastolytic enzymes leads to loss of elasticity and emphysema. Furthermore, CO in the cigarette smoke binds to haemoglobin replacing oxygen with COHb up to 7%–15% and this shifts the oxygen dissociation curves to left and will reduce oxygen availability to tissues.[13] Strong affinity of CO for binding to haemoglobin (250 times more than that of oxygen) can be offset by allowing the patients to breath 100% oxygen before anaesthesia induction. Increased airway reactivity due to smoke irritants predisposes the patient to frequent episodes of breath holding, laryngeal spasm, bronchospasm, hypoventilation and hypoxia during anaesthesia induction and emergence.

Gastrointestinal system
Smoking relax the gastro‑oesophageal sphincter, which returns to normal within minutes after stopping.

Renal system
Smoking results in increased secretion of anti‑diuretic hormone leading to dilutional hyponatraemia.

Hepatobilliary system
The pharmacokinetics and pharmacodynamics of drugs being metabolised in the liver become unpredictable because of induction of liver microsomal enzymes because of smoking.

Neuromuscular junction
The potency of amino steroid muscle relaxants (rocuronium and vecuronium) decreases in smoker. Although the exact mechanism is not clear, altered pharmacodynamics leading to either resistance or increased metabolism of drug at the receptor site has been suggested. [14,15]

Immunological function
Smoking impairs humoral activity and cell‑mediated immunity and decreases immunoglobulin and leucocyte activity which predisposes the smoker to increased risk of infection and malignancy.

Anaesthesia Management

Pre‑operative assessment
Patients are advised to stop smoking on their first pre‑operative visit. Abstinence of 8 weeks would be ideal however, an abstinence for 12–14 hours improve ciliary function and brings down the nicotine level to normal. Abstinence related anxiety and nicotine withdrawal symptoms need to be reassured and treated symptomatically.

Regional anaesthesia
Patients suitable for regional anaesthesia should be counselled and a suitable regional analgesia technique is used. High‑level of neuraxial blockade may result in difficulty in breathing by abolishing expiratory muscle power. Epidural analgesia must be considered in suitable cases for early mobilisation.

Pre-medication
Antisialogogues are important to reduce secretions and prevent spasm. Good analgesia and sedation ensure better depth of anaesthesia. Opioids are preferred over NSAIDS for risk of spasms.

Induction of anaesthesia
Anaesthesia induction should be preceded by pre‑oxygenation with 100% oxygen. Adequate depth of anaesthesia at the time of laryngoscopy and tracheal intubation has to be maintained to minimise the risk of bronchospasm. Ketamine increases secretions whereas sulphur moiety in Thiopentone can produce bronchospasm. Propofol abolishes airway reflexes and hence considered ideal for induction.

Inhaled Anaesthetics
Its better to use non irritant inhalational agents like sevoflurane or Halothane rather than irritant agents like Isoflurane.

Muscle Relaxants
Smokers may need an additional dose of amino‑steroid neuromuscular blocking agents because of altered pharmacodynamics at the neuromuscular junction receptors. Histamine secreting agents like Atracurium should be avoided.[16,17]

Post‑operative period
Early mobilisation is encouraged whenever feasible to improve lung function and sputum clearance. Smokers neither have a lower threshold for pain nor do they need less analgesia than non‑smokers.

Post‑operative nausea and vomiting
Smokers may have developed statistically insignificant tolerance to PONV because of the chronic emetogenic influence of nicotine.

Conclusion
Smoking is a health hazard and no amount of smoking is safe. Anaesthesiologist should have complete knowledge about pathophysiology and effects of smoking for successful patient management.

References:

1. World Health Organisation. WHO global report of trends in prevalence of tobacco smoking. Geneva: WHO Press; 2015
2. 2.Ryan H, Trosclair A, Gfroerer J. Adult current smoking: Differences in definitions and prevalence estimates – NHIS and NSDUH, 2008.J Environ Public Health 2012;2012:918368.
3. Warner MA, Offord KP, Warner ME, Lennon RL, Conover Jansson‑Schumacher U. Role of preoperative cessation of smoking and other factors in postoperative pulmonary complications: A blinded prospective study of coronary artery bypass patients. Mayo Clin Proc1989;64:609‑16.
4. Myers K, Hajek P, Hinds C, McRobbie H. Stopping smoking shortly before surgery and postoperative complications: A systematic review and meta‑analysis. Arch Intern Med 2011;171:983‑9.
5. van Domburg RT, Meeter K, van Berkel DF, Veldkamp RF,van Herwerden LA, Bogers AJ. Smoking cessation reduces mortality after coronary artery bypass surgery: A 20‑year follow‑up study. J AmColl Cardiol 2000;36:878‑83.
6. Moores LK. Smoking and postoperative pulmonary complications. An evidence‑based review of the recent literature. Clin Chest Med S2000;21:139‑46.
7. Wong J, Lam DP, Abrishami A, Chan MT, Chung F. Short‑term preoperative smoking cessation and postoperative complications: A systematic review and meta‑analysis. Can J Anaesth 2012;59:268‑79.
8. Bluman LG, Mosca L, Newman N, Simon DG. Preoperative smoking habits and postoperative pulmonary complications. Chest 1998;113:883‑9.
9. Khan MA, Hussain SF. Pre‑operative pulmonary evaluation. J Ayub Med Coll Abbottabad 2005;17:82‑6.
10. Erskine RJ, Hanning CD. Do I advise my patient to stop smoking pre‑operatively? Curr Anaesth Crit Care 1992;3:175‑80.
11. Pearce AC, Jones RM. Smoking and anesthesia: Preoperative abstinence and perioperative morbidity. Anesthesiology 1984;61:576‑84.
12. Schwilk B, Bothner U, Schraag S, Georgieff M. Perioperative respiratory
    events in smokers and nonsmokers undergoing general anaesthesia. Acta Anaesthesiol Scand 1997;41:348‑55.
13. Castleden CM, Cole PV. Carboxyhaemoglobin levels of smokers and non‑smokers working in the city of London. Br J Ind Med
    1975;32:115‑8.
14. Farhat K, Waheed A, Pasha AK, Iqbal J, Mansoor Q. Effect of smoking
    on nausea, vomiting and pain in the post‑operative period. J Postgrad
    Med Int 2014;28:277‑81.
15. Chimbira W, Sweeney BP. The effect of smoking on postoperative nausea and vomiting. Anaesthesia 2000;55:540‑4.
16. Teiriä H, Rautoma P, Yli‑Hankala A. Effect of smoking on dose requirements for vecuronium. Br J Anaesth 1996;76:154‑5.
17. Latorre F, de Almeida MC, Stanek A, Kleemann PP. The interaction between rocuronium and smoking. The effect of smoking on neuromuscular transmission after rocuronium. Anaesthesist 1997;46:493‑5.