Skip main navigation

Changes associated with obesity

Join us this week to discuss how obesity affects our body in terms of physiology, pharmacokinetics and pharmacodynamics

Cardiovascular

  • Physiology
    • ↑ Blood volume,
    • ↑ Systolic volume
    • ↑ Cardiac output
  • Presents as
    • Ischaemic heart disease
      • obesity is an independent risk factor for ischaemic heart disease
    • Hypertension
      • ↑ Extracellular volume and cardiac output are characteristic of obesity‐induced hypertension.
    • Cardiac failure
      • Left ventricular hypertrophy and ↓compliance, combined with ↑ blood volume
Weighted adjusted metabolic, blood volume and cardiac output are decreased when per kg values are used
  • Blood volume 50ml/kg vs 75ml/kg non obese
  • Pharmacokinetics (PK)
    • Drugs with narrow therapeutic indices may cause adverse effects if administered according to their actual body weight
    • ↑ Initial drug distribution
    • ↑ Loading dose required
    • ↑ Maintenance requirements
    • ↑Renal and hepatic blood flow
    • Using linear per kg dosing schemes designed for non-obese patients overestimates volumes and clearances
      • ↑ Overdose adverse effects
    • Obesity-related cardiovascular compromise
      • ↓ Distribution
      • ↓ Clearance for drugs that have high intrinsic clearance and are perfusion limited (e.g. propofol)

Respiratory

  • Difficult Airway
    • Incidence of difficult airway approximately 13%
    • Increased neck circumference
    • Fatty infiltration of the pharynx and peri glottic area
      • Increased risk of airway obstruction
    • Consideration to AFOI
  • Obstructive sleep apnoea (OSA)
    • 5%
    • Screening Test: STOP BANG criteria
      • Snoring: Snore loudly
      • Tiredness: Day time somulence
      • Observed: Stop Breathing or Choking/Gasping during your sleep
      • Pressure: High Blood Pressure
      • BMI: Body Mass Index more than 35 kg/m2
      • Age: >50years
      • Neck Circumference: Shirt collar 16 inches / 40cm or larger
      • Gender: Male
    • Polysomnography in a sleep laboratory
  • Obesity hypoventilation syndrome
    • The acid–base disturbance of OSA
    • Progressive desensitization of the respiratory centres
    • Ventilation reliance on hypoxic drive for ventilation
  • Pickwickian syndrome: Hypoventilation syndrome in an obese persons – Diminished to absent ventilatory chemoresponsiveness, – Chronic hypoxia, – Hypercapnia – Polycythemia – Hypersomnolence
  • Lung volume – Fatty deposits in the chest wall and increased intra-abdominal fat – Decrease thoracic compliance – Decrease lung volume – Functional residual capacity (FRC) – Rapid desaturation post-induction despite pre‐oxygenation. – Expiratory reserve volume (ERV)
  • Gas exchange
    • PEEP improves the PaO2 but only at the expense of cardiac output and oxygen delivery
    • Increased V/Q mismatch
This article is from the free online

Introduction to Using Total Intravenous Anaesthesia (TIVA)

Created by
FutureLearn - Learning For Life

Our purpose is to transform access to education.

We offer a diverse selection of courses from leading universities and cultural institutions from around the world. These are delivered one step at a time, and are accessible on mobile, tablet and desktop, so you can fit learning around your life.

We believe learning should be an enjoyable, social experience, so our courses offer the opportunity to discuss what you’re learning with others as you go, helping you make fresh discoveries and form new ideas.
You can unlock new opportunities with unlimited access to hundreds of online short courses for a year by subscribing to our Unlimited package. Build your knowledge with top universities and organisations.

Learn more about how FutureLearn is transforming access to education