• Arterial tourniquets
    • Local effects
      • Muscle
        • Progressive decrease in pO₂
          Decline in energy stores (ATP and creatine gone by 2-3 hrs)
          Lactate production
          Increased pCO₂ and intracellular acidosis
          Local fibre necrosis in 2hrs
          Post-tourniquet syndrome if >2hrs (post release, vascular permeability increased resulting in interstitial oedema. This results in a pale, stiff limb with weakness but not paralysis lasting 1-6 weeks)
      • Nerve
        • Physiological conduction block in 15-45 mins
          Direct compression can cause a longer tourniquet paralysis of up to 6/12
    • Complications
      • Nerve injury
        • Commoner in LL tourniquets
          Incidence about 0.025%
          Can resolve over next 6/12
      • Muscle injury
        • Post tourniquet syndrome
          Compartment syndrome
          Rhabdomyolysis
      • Skin injury
        • Chemical burns from alcohol solutions
          Friction burns
      • Vascular injury
        • Arterial injury can lead to amputations
          Likely due to plaque rupture
      • Intra-op bleeding
        • Due to incomplete exsanguination
          Under pressurised cuff
          Due to blood entering intramedullary vessels
    • Duration of use is recommended to be 1.5-2hrs max in a fit adult. If it needs to be deflated, allow 15 mins before re-inflating
      • Inflation to 100mmHg above SBP for UL or 150mmHg above SBP for LL surgery
      • Tourniquet pain is poorly understood and can occur even with a working epidural. May be due to c-fibre mediated pain afferents. Hypertension may be due to catecholamines or pain.
    • Systemic effects
      • Cardiovascular
        • Increase in SVR with transient increase in BP
          Increased circulating volume can cause CCF
          Tourniquet pain causes a 2nd increase in BP
          Tourniquet release causes low BP and CVP
      • Respiratory
        • With release, EtCO₂ increases (peak 1 min)
          Bigger effect with LL tourniquets
          CO₂ is raised for 6 mins unless MV increased
      • CNS
        • Increased pCO₂ due to deflation causes increased CBF. Maintain normocapnoea in HI patients
      • Haem effects
        • Global hypercoagulable state due to catecholamines, but a brief period of increased fibrinolytic activity may cause bleeding
      • Temperature
        • Core temperature increases with inflation, then decreases with deflation
      • Metabolic
        • Small increases in K+, lactate and CO₂
          Reduction in arterial pH
          Brief increase in O₂ consumption and CO₂ production with deflation
    • CEACCP
      Link:ceaccp.oxfordjournals.org/content/9/2/56.full.pdf