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Tourniquet Physiology + Deflation Management
TEXTEquipment · 6 min read
Pneumatic tourniquets enable bloodless extremity surgery — and produce a predictable, sometimes dangerous, deflation cascade. Know the limb-occlusion pressure, the 2-hour rule, and the K-spike on release.
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2 min read6 sectionsCuff pressure — limb-occlusion-pressure (LOP) method
LOP is determined by Doppler-confirmed loss of distal pulse with progressive cuff inflation.
Recommended cuff pressure = LOP + 50 mmHg (upper extremity) or LOP + 75-100 mmHg (lower extremity)Typical resulting pressures: 200-250 mmHg arm, 250-300 mmHg leg — well below the old fixed 250/350 mmHg that produced unnecessary nerve compression.
AORN + AAOS now endorse the LOP-based approach.
Wide cuffs (contoured) require lower pressures than narrow cuffs.
Duration limits + reperfusion intervals
If surgery exceeds 2 hours: deflate for 10-15 min reperfusion interval then re-inflate.
Each interval clears metabolic byproducts + restores tissue oxygenation.
Above 3 hours of cumulative time, rhabdomyolysis + nerve injury risk rise sharply.
Document inflation + deflation times in the chart — a quality measure tracked at most institutions.
Tourniquet pain
30-45 min after inflation in awake or lightly anesthetized patients.Mechanism: ischemic + compressive activation of unmyelinated C-fibers; relatively opioid-refractory.
Under GA: manifests as unexplained HTN + tachycardia after ~45 min.
Under spinal: cephalad-spreading discomfort, sometimes despite a high block.
Mitigation: peripheral nerve block (femoral + sciatic for lower extremity, IV regional/Bier for short upper-extremity cases) covers the tourniquet area; otherwise deepen anesthesia + add adjunct (clonidine, ketamine).
Deflation hemodynamics — the predictable cascade
5-15 mmHg from peripheral pooling + reactive hyperemia (sometimes more in dehydrated/sympathectomized patients).5-15 mmHg from CO₂ washout of the ischemic limb — visible within 30-60 seconds, peak by 3-5 min, resolves by 10-15 min.0.5-1.0 mEq/L transiently — usually inconsequential but can trigger arrhythmias in patients with baseline hyperkalemia.Mixed venous saturation falls briefly.
Pre-deflation strategy
5 mmHg (so the post-release rise doesn't overshoot).Ensure euvolemia — give a 250-500 mL crystalloid bolus 10 min pre-release if any concern for hypovolemia.
Have vasopressor drawn (phenylephrine 100 mcg).
If neurosurgery patient with intracranial concerns: hyperventilation + osmotic diuresis may be needed to blunt the CO₂ rise.
Communicate with surgeon — many staged bilateral procedures stagger the deflations to avoid summed effects.
Contraindications + complications
- severe peripheral vascular disease
- recent ipsilateral DVT (embolism risk)
- sickle cell disease (sickling in stasis)
- severe HTN (worsens reperfusion injury)
- open fracture with vascular concern
- severe diabetic neuropathy
Complications: nerve injury (radial in upper extremity most common — typically transient neurapraxia, resolves weeks-months; permanent injury rare), muscle infarction in prolonged ischemia, compartment syndrome on release, tourniquet shock (rare — hypotension + acidosis severe enough to require resuscitation), pressure necrosis under the cuff.
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