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

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    • **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
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  • 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
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        • 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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