obesity and general anaesthesia

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General anaesthesia in the obese patient is a difficult task because of a number of major complicating factors:

  • cardiovascular:
    • majority have moderate to severe hypertension
    • predisposed to atherosclerosis and the complications of ischaemic heart disease
    • right or left ventricular failure
    • increased risk of venous thrombosis
    • difficult intravenous access
  • respiratory:
    • poor airway access and management due to reduced neck and mouth mobility, relatively increased size of oropharyngeal tissue - difficult intubation
    • decreased chest wall compliance, inspiratory and expiratory volume, ventilatory effort
    • greater tendency to shunt blood to underperfused parts of lung; increased incidence of sleep apnoea
    • possibly, reliance on hypoxic drive for respiration - "Pickwickian syndrome"
  • endocrine:
    • impaired glucose tolerance - a tendency to hyperglycaemia
  • biochemistry:
    • deranged lipid levels and hypercholesterolaemia
    • labile LFT's because of lipid infiltration of liver
  • abnormal pharmokinetics:
    • greater size of lipid compartment and reduced size of water compartment alters the volume of distribution of a drug depending on whether it is hydrophobic or hydrophilic
    • altered drug binding and clearance
    • excessive degradation of halothane resulting in hepatitis
  • miscellaneous:
    • increased risk of wound infection
    • greater frequency of hiatus hernia, higher gastric pH and increased risk of aspiration
    • generally longer operations are needed

Last reviewed 10/2021

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