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Tourniquets

Key Points

• Pneumatic limb tourniquets create a bloodless surgical field but cause predictable ischaemic and compression injury that becomes clinically important after ~2 h.
• Contemporary guidelines advocate individualised inflation pressure based on limb occlusion pressure (LOP) rather than fixed values.
• Nerve injury is the commonest serious complication; risk triples for every additional 30 min of inflation beyond 60–90 min.

Local Effects

Tissue	Change during inflation	Thresholds for injury
Muscle	↑ PCO₂, ↑ lactate, ↓ pH; ATP depletion	Irreversible fibre necrosis after 2–3 h continuous ischaemia
Nerve	Conduction block (ischaemic within 30 min) and compression (mechanical)	Compression ≥ 300 mmHg or time > 90 min → axonotmesis (sciatic & radial most vulnerable)
Micro‑vasculature	Capillary leak, no‑reflow phenomenon	Histological injury evident at 120 min

Systemic Reperfusion Effects (on deflation)

• Cardiovascular: ↓ SVR & MAP (5–20 %), transient ↑ pulmonary artery pressure; arrhythmias if hyperkalaemia > 5.5 mmol L⁻¹.
• Respiratory: EtCO₂ rises 1–3 kPa within 60–90 s owing to wash‑out of CO₂‑rich blood and ↑ cardiac output.
• Metabolic: Serum K⁺ ↑ 0.4–0.8 mmol L⁻¹; lactate ↑ 1–2 mmol L⁻¹; base excess falls 2–3 mEq L⁻¹.
• CNS: ↑ PaCO₂ → cerebral vasodilatation; consider in patients with raised intracranial pressure.

Safe Inflation Pressures

Determine LOP with Doppler then add safety margin:

LOP (mmHg)	Adult margin*	Paediatric margin
< 130	+ 40	+ 50
131–190	+ 60	+ 50
> 190	+ 80	+ 50

British Orthopaedic Association BOAST 2021 recommends the same margins; adjust upward if hypertension or limb manipulation anticipated. Standard “fixed” pressures (250 mmHg upper limb, 300 mmHg thigh) over‑pressurise ~60 % of patients.

Safe Inflation Time

• Adults: Aim < 90 min continuous; strong data show three‑fold increase in neurological injury for every extra 30 min (systematic review 2024)
• If surgery > 2 h required, deflate for 10–15 min to allow reperfusion before reinflation.
• Children: Keep within 60 min wherever possible (low ischaemic tolerance)

Tourniquet Pain & Tourniquet‑Induced Hypertension (TIH)

Mechanism	Clinical sign	Prevention / Treatment
C‑fibre activation & sympathetic surge	Dull ache after 30–45 min, ↑ HR & BP (TIH)	Dense neuraxial block (epinephrine ± clonidine), IV ketamine 0.1–0.25 mg kg⁻¹ bolus or 0.3 mg kg⁻¹ h⁻¹ infusion, dexmedetomidine 0.2–0.5 µg kg⁻¹ h⁻¹; intra‑op clonidine 1 µg kg⁻¹ blunts TIH. Recent RCTs show esketamine 0.25 mg kg⁻¹ prevents TIH without psychomimetic emergence.

Contra‑indications (Relative)

• Severe peripheral arterial disease or dialysis fistula in limb
• Sickle‑cell disease (risk of crisis)
• Crush injury with compartment syndrome
• Neuropathy (diabetes, demyelinating disorders)
• Previous deep‑vein thrombosis or pulmonary embolism
• Patient refusal

Complications & Prevention

Complication	Incidence	Mitigation
Nerve injury (sciatic > radial)	0.1–0.2 %	Use LOP + margin; limit < 90 min; wide contoured cuff
Rhabdomyolysis & AKI	rare (< 0.01 %)	Avoid > 3 h; aggressive hydration post‑deflation
Skin burns / blisters	0.04 %	Proper padding, avoid barbs/glues under cuff
Vascular injury / thrombosis	rare	Avoid in severe PAD; ultrasound distal pulses post‑op if concern
Paradoxical bleeding under cuff	—	Complete exsanguination (Esmarch/limb elevation); verify cuff seal & pressure

Practical Checklist

1. Measure limb circumference; select widest possible contoured cuff (width ≥ 50 % limb diameter).
2. Ascertain LOP with Doppler; add safety margin.
3. Document inflation time start on theatre whiteboard; audible reminder at 60 & 90 min.
4. Maintain normothermia; monitor EtCO₂ & electrolytes for high‑risk patients.
5. Deflate slowly (10–30 s) with anaesthetist prepared for hypotension, arrhythmia & acidaemia.

Links

• Anaesthesia equipment

References:

1. Deloughry, J. L. and Griffiths, R. (2009). Arterial tourniquets. Continuing Education in Anaesthesia Critical Care &Amp; Pain, 9(2), 56-60. https://doi.org/10.1093/bjaceaccp/mkp002
2. Brunner UF, et al. Safe duration of pneumatic tourniquet inflation: systematic review. BMC Surg. 2024;24:197.
3. Ferguson KB, et al. Limb occlusion pressure versus fixed pressure in upper limb surgery: RCT. Bone Joint J. 2023;105‑B:1150‑7.
4. BOA Standards. BOAST: The safe use of intra‑operative tourniquets. British Orthopaedic Association; 2021.
5. Wilson JM, et al. Systematic review & meta‑analysis of tourniquet pressures in orthopaedic surgery. J Orthop Res. 2025;43:1294‑1305.
6. Ali M, et al. Esketamine prevents tourniquet‑induced hypertension in below‑knee surgery: RCT. Eur J Anaesthesiol. 2025;42:311‑8.
7. Ahmad N, et al. Sub‑anaesthetic ketamine attenuates TIH: double‑blind RCT. Pakistan Armed Forces Med J. 2022;72:230‑4.
8. Hanif A, et al. Tourniquet‑related nerve injury: narrative review. EFORT Open Rev. 2022;7:577‑589.
9. Hu Y, et al. Systematic review of tourniquet use in paediatric orthopaedics. EFORT Open Rev. 2023;8:30‑40.
10. FRCA Mind Maps. (2024). Retrieved June 5, 2024, from https://www.frcamindmaps.org/
11. Anesthesia Considerations. (2024). Retrieved June 5, 2024, from https://www.anesthesiaconsiderations.com/

Summaries
Tourniquets

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© 2025 Francois Uys. All Rights Reserved.

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