Preoperative management of PMHx/Drugs

See also Diabetes and Surgery

Cardiac disease

• Drugs:
  • Statins can be continued as normal
  • Beta-blockers can be continued (but should not be started if patient was not previously taking them)
  • Antiplatelets should be withheld 7-14 days prior
  • ACE inhibitors and ARBs should be withheld the day of surgery (they can cause marked hypotension with GA)
  • Diuretics should also be withheld on the day of surgery
  • Warfarin should be withheld 3-5 days before surgery (see below)
  • Calcium channel blockers can be continued
• Pre-operative risk and management
  • Get a cardiology review if there is any concern over the patient’s fitness for surgery
  • For patients undergoing non-cardiac surgery, the ACC/AHA have produced the following guide flow-chart

• • **Risk**
    • Using the Revised Lee Cardiac Index (RLCI)
      • Any 2 or more of the following would be high risk (>1% risk of major cardiac event)
        • PMHx of MI, (positive ETT, Angina, use of GTN, ECG with pathological Q waves or signs of ischaemia)
        • PMHx of CCF/HF; (pulmonary oedema, PND, bilateral rales or S3 gallop, CXR showing pulmonary vascular redistribution)
        • PMHx of stroke/TIA
        • Preoperative treatment with insulin
        • Preoperative eGFR <30ml/min
  • **METs** (Metabolic equivalent- 1= 3.5ml O2 uptake/kg/min (resting O2 intake))
    • These are similar to assessing someone’s exercise tolerance
      • Self care, eat, dress, toilet etc – 1 MET
      • Walk up a flight of stairs/hill or walk briskly for prolonged time (~4 METs)
      • Can do heavy work, or climb 2 flights of stairs (6-10 METs)
      • Can do strenuous exercise (10+ METs)
• In patients with unstable Coronary artery disease, it may be appropriate to perform revascularisation (PCI) prior to surgery.  However, this would only represent a minority of patients.
• Patients with Valvular disease (in particular stenoses) should be considered for peri-operative antibiotic therapy to reduce the risk of endocarditis
• Post-operatively
  • Make sure to monitor any signs of silent ischaemia (cardiac monitoring) and heart failure

Respiratory Disease

• The main issue with surgery in patients with respiratory disease is due to anaesthesia
  • Sedation can cause hypoventilation and atelectasis, worsening hypoxaemia and hypercapnia, increased V/Q mismatch
  • Airway manipulation can cause a reactive bronchospasm which can be severe in patients with airways disease
  • Controlled ventilation may cause impaired airflow and increased hyperinflation of the lungs in patients with COPD (and even ‘dynamic hyperinflation’ i.e. continuous inflation of the lungs
  • As such, if possible, avoid general anaesthesia (i.e. use regional anaesthesia)
• Assessing/managing risk
  • Pulmonary function tests are crucial.  Note that most operations will result in a reduction in pulmonary function peri- and postoperatively, and this should be taken into account when deciding if surgery is appropriate
    • Deep breathing exercises +/- chest physiotherapy/rehabilitation is often useful in patients with COPD to improve function prior to surgery
    • If FEV1/FVC ratio <50%- risk of respiratory failure following surgery is increased dramatically
  • Smoking cessation- this will reduce the risk of post-operative complications including wound healing and pulmonary complications
  • Intra-operative PEEP (positive end expiratory pressure) and post-operative non-invasive ventilation (CPAP or BIPAP) may prevent respiratory failure
  • Make sure to correct any exacerbations prior to surgery
• Drugs
  • Inhalers/nebulisers should be taken pre-operatively (ideally close to induction)
  • For steroid use, see below
  • Note that anaesthetic drug choice may be important
    • Nitrous oxide may rupture bullae in COPD and cause pneumothorax
    • Opiates usually cause respiratory depression
    • Post operative pain may result in respiratory depression
    • General anaesthesia
      • Reduces muscle tone and thus residual capacity
      • Increases airway resistance and reduces lung compliance
      • Causes atelectasis in dependent zones (causing increased V/Q shunting)
      • Increases ventilatory dead space

Liver Disease

• Assessment
  • Contraindications to surgery include Acute or fulminant hepatitis, alcoholic hepatitis and severe chronic hepatitis
  • For other patients with liver disease, there are several scoring systems used to categorise risk (Child-Pugh and MELD scores)
    • In general, CP class A/MELD score <10 can undergo elective surgery; CP class B/MELD score 10-15 can undergo elective surgery with caution (see below) and CP class C/MELD score >15 should not undergo elective surgery
    • 
• Optimisation
  • In patients with prolong PT- vit K can be given pre-operatively to correct this
  • In patients with ascites and oedema, diuretics may be used to reduce this (alternatively ascites may be drained intraoperatively)
  • Electrolyte abnormalities should be corrected and renal function evaluated/optimised.
  • Patients with gastroesophageal varices should be treated optimally (whether with betablockers/nitrates or with banding/ligation) prior to surgery
  • Where possible, correct any jaundice prior to surgery

Diabetes (see diabetes and surgery)

Thyroid disease

Hypothyroid

• Potential adverse outcomes
  • Low cardiac output and increased risk of CVD (increased risk of MI; hypotension)
  • Blood loss poorly tolerated
  • Respiratory centre less responsive to O2 and CO2 pressures (hypoventilation; acidosis)
  • More sensitive to opiates
  • Hypothermia
  • Hypoglycaemia
  • Hyponatraemia
• Management
  • In overt hypothyroidism- correction (levothyroxine) should ideally be given prior to surgery where possible
    • In severe cases (myxoedema coma)- T3 and T4 may be given prior to surgery

Hyperthyroid

• Increased risk of
  • tachycardia; labile BP and arrhythmias (increased output and contractility due to increase in O2 demand)
  • dyspnoea (similar reason)
  • Thyroid storm- an uncontrolled release of thyroid hormone.  Causes hyperthermia and metabolic acidosis (high mortality)
    • Note that treatment is the same as for hyperthyroidism but increased dose/frequency and adequate ITU support. 
• Management
  • Ideally controlled with carbimazole or propylthiouracil prior to surgery
    • If surgery is urgent and hyperthyroidism not controlled- potassium iodide drops may temporarily halt to the release of hormones (not temporarily)
  • Propanolol can be used for symptomatic relief

A note about some drugs

• Steroids
  • Ideally, patients should not be on steroids, as they can lead to
    • Poor wound healing
    • Infection
    • Impaired glucose tolerance
    • Muscle wasting
    • Electrolyte disturbances
    • Masking of sepsis
  • However, patients that are taking or have recently (< 3 months) taken steroids at a dose of >10mg/day are at risk of adrenocorticoid insufficiency should they be stopped.
    • Peri-operatively, this could potentially cause cardiac failure or an Addisonian crisis
    • As such, steroids should be given to cover for this in these patients
    • 
      • Dosing equivalents: Prednisolone 10 mg is equivalent to Betamethasone 1,5 mg or Cortisone acetate 50 mg or Dexamethasone 1.5 mg or Hydrocortisone 40 mg or Deflazacort 12 mg or Methylprednisolone 8 mg
• Warfarin
  • Due to the risk of bleeding, warfarin should ideally be stopped 3-5 days prior to surgery (INR <1.5)
  • If the risk of thrombosis is high (e.g. metallic heart valve); then warfarin should be replaced with heparin.  If the risk is relatively low e.g. AF (without previous CVA), then it may be possible to stop without any heparin substitute.
• Antiplatelet agents (aspirin, clopidogrel etc)
  • Should be stopped 7-14 days prior to surgery due to risk of bleeding.
• Anti-epileptics
  • Should be continued where possible

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