- Tobacco smoke contains a delightful cocktail of carcinogenic and other toxic compounds, such as:
| Nicotine | Benzene | Toluene |
| Tar | Phenol | Hydrogen cyanide |
| Carbon monoxide | Acetaldehyde | Ammonia |
| Nitric oxide | Acrylamide | Benzanthracene |
Smoking
Smoking
The curriculum asks us to: 'explain the effects of smoking on health', presumably beyond the fact it's bad for pretty much every organ.
Indeed an SAQ on smoking from 2018 (70% pass rate) asked about 'the effects of smoking, its pathophysiology and anaesthetic implications'.
Resources
- Smoking and anaesthesia (BJA Education, 2018)
- Smoking and Anaesthesia: Perioperative Smoking Cessation and the Role of the Anaesthetist (WFSA, 2022)
- The implications of vaping for the anaesthetist (BJA Education, 2021)
- Consensus recommendations for perioperative management of cannabis and cannabinoid-based medicine users by a modified Delphi process (BJA, 2020)
- Consensus Guidelines on the Management of the Perioperative Patient on Cannabis and Cannabinoids (American Society of Regional Anaesthesia and Pain Medicine, 2023)
Respiratory
- There is an increase in carboxyhaemoglobin levels to 2-15%
- Seeing as CO has a 250x greater affinity for Hb than oxygen, this greatly impairs oxygen carriage
- COHb causes a left-shift of the oxyHb-dissociation curve, which further reduces oxygen delivery/supply by impairing the ability of Hb to release oxygen
- Decreased surfactant production reduces lung compliance, causing small airway closure
- Reflexive bronchoconstriction to inhaled particles
- Accelerated decline in FEV1 from 30ml/yr to 70ml/yr
- Increases in:
- Mucous production, mucous viscosity and ciliary dysfunction → difficult clearing secretions
- Cough and bronchial reactivity → increased incidence of laryngospasm, bronchospasm and breath holding
- Rates of respiratory disease such as COPD and lung cancer
- Rates of perioperative pulmonary complications:
| Perioperative respiratory complications associated with smoking |
| Post-operative pulmonary complication |
| Breath-holding |
| Laryngospasm |
| Bronchospasm |
| PE |
| Sputum retention |
| Pulmonary oedema |
Cardiovascular
- Nicotine induces catecholamine release, activating the sympathetic nervous system and leading to increases in:
- Heart rate i.e. tachycardia and higher propensity to dysrhythmia
- Hypertension
- Systemic vascular resistance
- Overall this increases myocardial work while simultaneously impairing oxygen supply, predisposing patients to myocardial ischaemia
- Elevated carbon monoxide levels also contribute to myocardial ischaemia via:
- Increasing myocardial oxygen demand
- Coronary vasoconstriction
- Reducing the oxygen-carrying capacity of haemoglobin
- Atherosclerosis
- Chemicals in tobacco smoke injure the arterial endothelium
- They diminish endothelial production of nitric oxide, impairing endothelium-dependent relaxation of arteries
- There is up-regulation of leucocyte adhesion molecules, while monocyte migration and adhesion is promoted by increased LDL oxidation
- Continued stimulation of intimal cells by oxidised LDLs leads to development of atherosclerosis
- Polycythaemia, increased fibrinogen concentration and altered platelet activity increases risk of thrombosis
| Cardiovascular disease states associated with smoking |
| Coronary artery disease (2-4x ↑ risk) |
| Peripheral vascular disease (10x) |
| Stroke inc. SAH (2x) |
| Heart failure |
| Arrhythmias |
| Coronary vasospasm |
| VTE |
Gastrointestinal
- There is an increased risk of:
- GORD due to relaxation of lower gastro-oesophageal sphincter
- Peptic ulcer disease
- Crohn's disease
- There is a perhaps counter-intuitive reduction in PONV and the incidence of ulcerative colitis
Other systems
- Neurological; CNS stimulant and physiological dependence
- Malignancy; increased risk of malignancy of virtually any type
- Immunosuppression; delays wound healing and increases risk of wound infection
- Metabolic; osteoporosis due to alterations in bone metabolism
- Reproductive system; higher incidences of infertility, ED and a host of pregnancy-associated complications (stillbirth, ectopic, pre-term labour, abruption)
- Pharmacological:
- CYP450 enzyme inducer (CYP1A1, 1A2 and 2E1), which reduces the effective concentration of some drugs inc. volatile agents
- Increased post-operative opioid requirement
- Can cause a lung function impairment similar to tobacco smoking
- It is associated with oropharyngitis and uvular oedema which can increase risk of acute airway obstruction in patients receiving GA
- There may be post-operative withdrawal effects
Anaesthetic implications
- Patients using significant quantities should wean off cannabis-containing substances if >1 day until surgery
- Consider intra-operative depth of anaesthesia monitoring; patients may require a greater depth of anaesthesia
- Cannabis itself is an anti-emetic, but patients may require greater anti-emetic doses due to cannabis-influenced dysfunction of endogenous cannabinoid receptors
- Cannabis may have some analgesic properties, however it can:
- Cause tolerance to some effects of NSAIDs or opioids, necessitating higher post-operative doses
- Decrease post-operative pain tolerance through distress and/or cannabis withdrawal syndrome
- Long-term outcomes unknown
- Presence of vitamin E acetate may be associated with e-cigarette/vape-associated lung injury (EVALI), which causes ARDS
- Other issues include: gateway to smoking in the young, nicotine overdose and burn injuries
Anaesthetic implications
- Tendency towards increased airway reactivity and bronchospasm, with reduced ciliary function and impaired cough reflex
- Still suffer cardiovascular and neuropsychological effects of nicotine
- E-cigarette use may be associated with endothelial dysfunction and oxidative stress
Perioperative management of the patient who smokes
- Encourage cessation; leaflet | referral to specialist services | prescription for nicotine replacement therapy
- Quitting prior to surgery reduces incidence of peri-operative complications
- The longer the period of cessation, the greater the benefit
Positive effects of cessation
| Timeline | Effect |
| 24hrs | Clearance of nicotine (t1/2 30mins) - [NB active metabolite t1/2 20hrs] Clearance of CO (t1/2 4hrs) Improved DO2 Improved physiological reserve w.r.t coping with hypoxia Heart rate normalises ↓ myocardial oxygen demand |
| 1-3 weeks | ↓ cough & wheeze ↓ lung inflammation Improved mucociliary clearance |
| 4 weeks | Risk of wound infection same as for non-smoker |
| Months | Mortality reduced by 1/3rd in those with existing coronary artery disease |
| Long-term (10-15 years) |
Lung inflammation subsides ↓ risk of IHD ↓ risk of stroke Slower decline in FEV1 |
Negative effects of cessation
- There may be initial negative psychological sequelae such as anxiety, withdrawal or agitation
- There is an initial increase in sputum production and airway reactivity upon smoking cessation, with mucociliary clearance improving after a week
- There is a higher rate of PONV
- Alveolar destruction and fibrosis may be permanent
Cannabis
- Establish product type, amount and frequency of use
- Check for date/time of last consumption
- Counsel patient on risks including increased post-operative pain and PONV
- Consider delaying non-emergent surgery for at least two hours following the most recent consumption as potentially associated with incresed risk of MI
- Consider cancelling elective surgery where adults are under the influence of acute cannabinoid intoxication
- May need to modify anaesthetic technique based on comorbidities associated with smoking, e.g. COPD, cardiovascular disease
- Anticipate respiratory adverse events, as the incidence of all of them is increased (see above)
- Especially prominent in the young (16-39yrs) and the obese
Cannabis
- Consider intra-operative depth of anaesthesia monitoring; patients may require a greater depth of anaesthesia
- Multi-modal analgesia as may have tolerance to NSAIDs and/or opioids
- Multi-modal anti-emesis due to dysregulated endogenous cannabinoid system
VTE
- Higher VTE risk due to:
- Secondary polycythaemia
- Enhanced platelet function
- Increased fibrinogen levels
- Co-existing vascular disease
- Provide VTE prophylaxis as appropriate
Complications
- There is an overall increased risk of morbidity and mortality in smokers
- In brief, there is an increased risk of all respiratory, cardiovascular and septic complications
- The relationship between smoking and post-operative morbidity is dose-dependent
- The increased risk is consistent across a variety of surgeries
| Perioperative complication | Odds ratio |
| Unplanned HDU admission | - |
| ↑ duration hospital stay | - |
| ↑ rate of re-admission | - |
| 30-day mortality | 1.38 |
| Pneumonia | 2.09 |
| Unplanned intubation | 1.87 |
| Mechanical ventilation | 1.53 |
| MI | 1.80 |
| Stroke | 1.73 |
| Cardiac arrest | 1.57 |
| Superficial wound infection | 1.30 |
| Deep wound infection | 1.42 |
| Organ space infection | 1.38 |
| Septic shock | 1.55 |
Cannabis
- Monitor for cannabis withdrawal symptoms
- Ongoing multi-modal anti-emesis and analgesia