Surgical Tourniquets

Types of Tourniquets

  1. Pneumatic:
    • Automatic: More accurate.
    • Manual.
  2. Non-Pneumatic:
    • E.g., for finger surgery.

Contra-indications to Tourniquet Use

  1. Absolute:
    • Severe crush injuries.
    • Compartment syndrome.
  2. Relative:
    • Sickle cell disease.
    • Peripheral vascular disease.

Cuff Design and Pressures

  • Pressures:
    • Highest at the center of the cuff where skin pressure is 95% of the cuff pressure.
    • Higher cuff pressure correlates to higher tissue pressure.
    • Tissue pressures fall as limb circumference increases.
    • Only a 2% decrease in pressure from the surface to the deepest tissues.
  • Cuff Width:
    • Narrower cuffs require higher occlusion pressure for the same limb circumference.
    • Wider cuffs should be used in larger limbs to reduce the risk of neurological injury.

Limb Occlusion Pressures (LOP)

  • Pressure required to occlude arterial flow distal to the cuff.
  • Traditional Recommendations:
    • Add 50–75 mmHg to the systolic pressure for the upper limb.
    • Double the systolic pressure for the lower limb.
  • More Accurate Method:
    1. Gradually increase tourniquet pressure until the distal pulse is lost.
    2. Adjust:
      • Add 40 mmHg for occlusion pressures <130 mmHg.
      • Add 60 mmHg for occlusion pressures <190 mmHg.
      • Add 80 mmHg for occlusion pressures >190 mmHg.
    • This method results in significantly lower tourniquet pressures.

Limb Exanguination

  • More effective than elevation alone.
  • Contraindications:
    • Infection.
    • Metastatic disease.
    • Venous thrombosis.

Limb Protection

  • Studies show padding under the cuff reduces skin injuries.
  • Two-layer elastic stockinette is superior to Velband padding.

Duration of Tourniquet Use

  • Recommended: 2 hours (safe, especially in the upper limb).
  • No definitive unsafe time, but:
    • Longer durations = increased risk of nerve injury and tissue ischaemia.
    • Up to 3 hours may be acceptable in the lower limb (use common sense).

Complications of Tourniquet Use

Local

  • Neuropraxia.
  • Muscle ischaemia and necrosis.
  • Vascular injury.
  • Post-release swelling and joint stiffness.
  • Haematoma formation.
  • Delayed recovery of muscle power.

Systemic

  • Embolism of fat and metabolites.
  • Cardio-respiratory decomposition (not conclusively proven).

Neuropraxia

  • Resolves within 3 months.
  • Affects motor and sensory functions (temperature sensation preserved).
  • Pulses, skin appearance, and temperature are normal.
  • EMG findings: Conduction block at the level of the tourniquet.

Muscle Ischaemia

  • Re-perfusion injury to the muscle.
  • Longer tourniquet times = higher CK levels and more tissue ischaemia.
  • Tissue markers normalize between 2 and 20 minutes after reperfusion.
  • No evidence that deflating and re-inflating the tourniquet improves safety.

Myonephrotic Metabolic Syndrome

  • Rare, occurs in severe ischaemia.
  • Features:
    • Renal failure.
    • Metabolic acidosis.
    • Myoglobinuria.
    • Hyperkalaemia.

Tourniquet Deflation

  • No evidence that tourniquet use increases the risk of DVT or PE after deflation.
  • Precautions:
    • Monitor patients undergoing intramedullary procedures for sudden fat or metabolite embolism.
  • Effects of Deflation:
    • Increases production of antithrombin 3 and Protein C, leading to increased bleeding and reduced clotting.

Tourniquet Release in Total Knee Replacement (TKR)

  • Pre-closure deflation:
    • Increases blood loss and transfusion needs.
    • Associated with increased infection risk.
  • Post-closure deflation:
    • More likely to require return for wound washout.
  • Surgeon’s Discretion:
    • Balance between minimizing blood loss and reducing infection risk.
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