Conference Lectures

Smoking and Anaesthesia
           
Aloka Samantaray
Professor
Department of Anaesthesiology and Critical Care,
Sri Venkateswara Institute of Medical Sciences
SVIMS University
Tirupati
Andhra Pradesh.

Introduction
Smoking whether active or passive is always a general health problem but when such patients come for surgery possess additional challenges to the anaesthesiologist [1,2].This lecture note will give a brief account of :(1) who is a smoker and different terminology being described in literature to describe smoking;(2)who need to quit smoking before surgery and when;(3)how smoking adversely affect the physiology of body and based on the available literature formulate an anaesthetic plan in smokers.
Who are a smoker and the terminology surrounding smoking?
According to world health organisations (WHO's) Smoking and Tobacco Use Policy, a smoker is someone who smokes any tobacco products (entirely or partly made of the leaf tobacco as raw material), either daily or occasionally. A daily smoker is someone who smokes any tobacco product at least once a day. An occasional smoker is someone who smokes, but not every day [3].
The National Center for Health Statistics (NCHS) at the Centers for Disease Control and Prevention (CDC) defines an “ever smoker” as one, who has smoked at least 100 cigarettes in their entire life. A “current smoker” is a subset of ever smoker and includes daily smoker and occasional smoker. A “former smoker” is a subset of ever smoker, who was not smoking at the time of the interview. A “never smoker” is a person who was neither smoking at the time of interview nor consumed 100 cigarette in his life time [4].The National Survey on Drug Use and Health(NSUDH) has redefined a current smoker as one,  who both reported smoking part or all of a cigarette during the 30 days preceding the interview and consumed more than 100 cigarette in his life time. So obviously the prevalence of current smokers yields a higher percentage as per modified NSDUH criteria [5].
Light smoker: a smoker who reports consuming between 1-10 cigarettes per day.
Moderate smoker: a smoker who reports consuming between 11-19 cigarettes per day.
Heavy smoker: a smoker who reports consuming 20 cigarettes or more per day.
Electronic nicotine delivery systems (ENDS): Electronic cigarettes are devices that do not burn or use tobacco leaves but instead vaporise a nicotine solution which the user inhales. The other constituents of the solution are propylene glycol, with or without glycerol and flavouring agents.
Passive smoking or second-hand smoking: Involuntary inhalation of a mixture of the smoke given off directly by the burning of tobacco and the smoke exhaled by smokers. As these smokes are unfiltered they contain more carcinogenic and more irritant materials and possess a greater health hazard than active smoking.
Water pipe smoking or “Hukka”: They contain more nicotine(2-4% vs. 1-3%) and higher CO concentration(0.34-1.4% vs.0.41%) than cigarette
Who need to quit smoking and when?
Considering the fact that smoking is a general public health concern it is advisable to stop smoking whether somebody need to undergoes a surgery or not. There is an ill-founded study that stopping smoking shortly before surgery may increase complications [6].However recent data did not substantiate such finding and concludes no increase in complications amongst smokers who quit within two months of surgery [7].Quitting smoking at any time before or after surgery is always beneficial for the patients [8] .However most investigators suggest that stopping smoking two months prior to surgery provides the maximum benefit[7,9,10]
How smoking adversely affects the body physiology?

There are several toxic substances that can be isolated from cigarette smoke [11]. Nicotine and carbon monoxide (CO) are the two toxic substances in cigarette smoke which bring undesirable imbalance in physiological response. Apart from nicotine and CO the other toxic substances are nitrogen oxides, volatile aldehydes, alkenes and the toxin hydrogen cyanide. In smokers, there are

no changes in the action of volatile agents but increased metabolism can lead to higher levels of toxic metabolites [12].

  1. Cardiovascular system

Nicotine stimulates the adrenal medulla to secrete adrenaline which in turn 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 ischemic damage. The ischemic myocardial damage is further compounded by raised intracellular calcium, a response to nicotine stimulation [13].
Carbon monoxide inactivates myocardial mitochondrial enzyme system by reversibly binding with cytochrome oxidase and myoglobin .So a negative inotropic effects set in with decrease in the intracellular oxygen transport and utilisation as a result of chronic tissue hypoxia.
The half-life of nicotine and carboxy haemoglobin (COHb) are 30-60 minutes[ 13]  and 4-6 hours respectively. The elimination of effects of nicotine depend on abstinence from smoking where as that of CO depends chiefly on pulmonary ventilation [14]. So even a brief period (4-6hours) of abstinence from smoking eliminates the harmful effects of nicotine and CO and brings a favourable myocardial oxygen-demand supply ratio. The author believes that Smokers presenting for an emergency surgery or are unable to quit smoking till they have been scheduled for elective surgery should be advised to refrain from smoking on the day of the operation

  1. Respiratory system

The substances in tobacco and tobacco smoke may cause harm even at low levels of exposure. The irritants and ciliotoxins present in tobacco smoke increases mucous production and impair mucus clearance from the tracheobronchial tree [15]. This result in complete paralysis of the defence mechanism of the respiratory tract and leads to clogging of the lungs with hyper viscous thick mucus secretion, bacteria and dead cells .This makes the lungs vulnerable to various infections[9,16].The irritant smoke damages the lung epithelium which result in small airway narrowing(decreased closing volume),chronic bronchitis. In addition to damaged epithelium an increase in proteolytic and elastolytic enzymes leads to loss of elasticity and emphysema. All these pathological changes leads impaired gas exchange function[17].Further more CO in the cigarette smoke binds to hemoglobin replacing oxygen with COHb up to 7-15% [18]and this shifts the oxygen dissociation curves to left and  will reduce oxygen availability to tissues. Though the affinity of CO is 250 times more than that of oxygen for binding to haemoglobin,the removal of CO from haemoglobin can be expediated by administering 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 induction and emergence from anaesthesia.

  1. Gastrointestinal system

Smoking as such has no direct effect on the gastric volume or the pH of gastric secretions and do not increases the risk for acid pulmonary secretion. Smoking may relaxes the gastro-oesophageal sphincter but returns to normal within minutes after stopping.

  1. Renal system

Smoking results in increased secretion of anti-diuretic hormone (ADH) leading to dilutional hyponatremia.

  1. Hepatic system

The pharmacokinetics and pharmacodynamics of drugs being metabolised in liver become unpredictable because smoking induces liver microsomal enzymes and enhances biotransformation of many drugs that share cytochrome P-450 mixed oxidase pathway. Smoking significantly influences the requirement for opioid analgesics. Smokers neither have a lower threshold for pain nor do they need less analgesia than non-smokers.

  1. Neuromuscular junction

The potency of aminosteroid muscle relaxants (rocuronium and vecuronium) decreases in smoker. Though the exact mechanism is not clear but an altered pharmacodynamics leading to either resistance or increased metabolism of drug at the receptor site has been suggested[19,20].Smokers who refrain from smoking for > 10 h require a smaller maintenance dose of atracurium than non-smokers. However, using a transdermal nicotine system prevents the decrease in maintenance dose of atracurum during abstinence [21]

  1. Immunological function

There is well documented evidence that, smoking Impairs humoral activity and cell mediated immunity, decreases immunoglobulin and leucocyte activity. All this predisposes the smoker to increased risk of increased risk of infection and malignancy [15].
Anaesthesia planning

Preoperative assessment: Patients are advised to stop smoking on their first preoperative visit. An abstinence of 8 weeks derives the most benefits of stopping smoking. However an abstinence for 12-14 hours improves ciliary function and brings down the nicotine level to normal; abstinence for 2 weeks helps return sputum volume to normal levels; abstinence for 5-10 days improves laryngeal and bronchial activity; abstinence for 4 weeks reduces early

 

  1. small airway closure; abstinence for 3 months maximise tracheobronchial clearance. A small subset of patients exhibits anxiety and nicotine withdrawal symptoms and they need to be reassured and treated symptomatically.
  2. Regional anaesthesia: patients suitable for regional anaesthesia should be identified and a suitable regional analgesia technique is used.
  3. Induction of anaesthesia: Should be preceded by pre-oxygenation with 100% oxygen routinely. The need for tracheal intubation should always be anticipated while using supraglottic airway devices or total intravenous anaesthesia in lieu of hyperactive airway. Adequate depth of anaesthesia at the time of laryngoscopy and tracheal intubation has to be maintained to minimise the risk of inciting a bronchospasm.
  4. Anaesthetic drugs: Smokers may need an additional dose of amino-steroid neuromuscular blocking agents because of altered pharmacodynamics at the neuromuscular junction receptors. Adequate and appropriate analgesia in the form of epidural analgesia should be considered in lieu of their beneficial role in preventing postoperative pulmonary complications particularly in patients undergoing thoracic and upper abdominal surgeries.
  5. Postoperative period: Early mobilization is encouraged whenever feasible to improve lung function and sputum clearance

Conclusions
Smoking is a health hazard and no amount of smoking is safe. Anaesthesiologist as a responsible care taker of national /global health should involve himself/herself actively to council the patients against smoking in any form.

References

  1. Theadom A, Cropley M. Effects of preoperative smoking cessation on the incidence and risk of intraoperative and postoperative complications in adult smokers: a systematic review. Tob Control. 2006 Oct;15(5):352-8.
  2. Sadr Azodi O, Bellocco R, Eriksson K, Adami J. The impact of tobacco use and body mass index on the length of stay in hospital and the risk of post-operative complications among patients undergoing total hip replacement. J Bone Joint Surg Br. 2006 Oct;88(10):1316-20.
  3. World Health Organization, WHO Report on the Global Tobacco Epidemic, 2013: Available on http://www.who.int/tobacco/global_report/2013/en/.Assessed on 18.10.2014
  4. Centers for Disease Control and Prevention (CDC). Cigarette smoking among adults--United States, 1992, and changes in the definition of current cigarette smoking. MMWR Morb Mortal Wkly Rep. 1994 May 20;43(19):342-6. Erratum in: MMWR Morb Mortal Wkly Rep 1994 Nov 4;43(43):801-3.
  5. 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. doi: 10.1155/2012/918368. Epub 2012 May 9.
  6. Warner MA, Offord KP, Warner ME, Lennon RL, Conover MA, 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 Proc. 1989 Jun;64(6):609-16.
  7. 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 Jun 13;171(11):983-9.
  8. 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 Am Coll Cardiol. 2000 Sep;36(3):878-83.
  9. Bluman LG, Mosca L, Newman N, Simon DG. Preoperative smoking habits and postoperative pulmonary complications. Chest. 1998 Apr;113(4):883-9.
  10. Khan MA, Hussain SF. Pre-operative pulmonary evaluation. J Ayub Med Coll Abbottabad. 2005 Oct-Dec;17(4):82-6.
  11. Dawson GW, Vestal RE. Smoking and drug metabolism. Pharmacol Ther. 1981;15(2):207-21. Review.
  12. Sweeney BP, Grayling M. Smoking and anaesthesia: the pharmacological implications. Anaesthesia. 2009 Feb;64(2):179-86.
  13. Erskine RJ, Hanning CD. Do I advise my patient to stop smoking pre-operatively? Current Anaesthesia and Critical Care 1992;3:175-80.
  14. Nicod P, Rehr R, Winniford MD, Campbell WB, Firth BG, Hillis LD. Acute systemic and coronary hemodynamic and serologic responses to cigarette smoking in long-term smokers with atherosclerotic coronary artery disease. J Am Coll Cardiol. 1984 Nov;4(5):964-71.
  15. Pearce AC, Jones RM. Smoking and anesthesia: preoperative abstinence and perioperative morbidity. Anesthesiology. 1984 Nov;61(5):576-84.
  16. Schwilk B, Bothner U, Schraag S, Georgieff M. Perioperative respiratory events in smokers and nonsmokers undergoing general anaesthesia. Acta Anaesthesiol Scand. 1997 Mar;41(3):348-55.
  17. Nunn JF. Smoking in Applied Respiratory Physiology. 3rd ed London: Butterworth; 1989:337-41
  18. Castleden CM, Cole PV. Carboxyhaemoglobin levels of smokers and non-smokers working in the City of London. Br J Ind Med. 1975 May;32(2):115-8.
  19. Teiriä H, Rautoma P, Yli-Hankala A. Effect of smoking on dose requirements for vecuronium. Br J Anaesth. 1996 Jan;76(1):154-5.
  20. 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 Jun;46(6):493-5.
  21. Puura AI, Rorarius MG, Laippala P, Baer GA. Does abstinence from smoking or a transdermal nicotine system influence atracurium-induced neuromuscular block? Anesth Analg. 1998 Aug;87(2):430-3.