Perioperative Tourniquet Use

Introduction

• A tourniquet is a constrictive, circumferential band used to transiently stop blood flow to an appendage. The two major tourniquets used during surgical procedures are pneumatic and the Esmarch bandage.¹
• Pneumatic tourniquets require an inflation device that introduces air into the cuff and pressurizes it. The Esmarch tourniquet is made of elastic rubber. The Esmarch bandage is tightly wrapped around the limb to occlude blood flow.¹
• Pneumatic tourniquets are regarded as safer than Esmarch tourniquets as the latter do not allow the measurement or adjustment of tourniquet compression pressure.¹¹
• Dating back to the 16th century, tourniquets were initially used to control hemorrhage during an amputation. Currently, limb elevation and direct pressure with hemostatic gauze are used initially for out-of-hospital limb hemorrhage emergencies.²
• Tourniquets are now primarily used for intravenous (IV) regional anesthesia, IV regional sympathectomy for chronic pain regional syndromes, and to reduce blood loss and improve visualization during extremity surgery.

Complications of Tourniquet Use

Tourniquet use can cause direct injury to the underlying skin, vasculature, muscle, and nerve.

Skin Injury

• Tourniquet-induced skin injury is uncommon. At-risk patients include those with friable, frail skin or pediatric patients. Improperly positioned tourniquets can cause skin abrasion, and excessive compression pressure can lead to skin necrosis.

Vascular Injury

Vascular injury is also a rarity. Patients with a history of vascular surgery in the surgical limb or severe peripheral vascular disease (nonpalpable distal pulses or calcified femoral-popliteal vasculature) may have contraindications to tourniquet use. In these patients, mechanical pressure from inflation can disturb calcified plaque and accelerate thrombosis.²

Muscle Injury

• Tourniquet-induced muscle injury may go unrecognized in many cases. Extensive muscle injury is termed “post-tourniquet syndrome” and presents with weakness, numbness, stiffness, and pallor. Muscle compression by the tourniquet increases microvascular permeability and endothelial injury. This leads to edema. Severe cases of muscle edema with reperfusion hyperemia after tourniquet release resulting in compartment syndrome and rhabdomyolysis have been reported.^5,6

Nerve Injury

• Nerve injury from tourniquet compression usually resolves within 6 months. Symptoms are typically mild, with paresthesias, but there are reported cases of tourniquet-induced permanent nerve injury resulting in paralysis.⁵
• These cases involved tourniquet pressure calibration errors and were not the result of normal functioning tourniquets. Upper extremities are more sensitive to tourniquet-induced nerve injury, specifically the radial nerve. The median nerve is the most resistant to injury in the upper limb. The sciatic nerve is commonly injured in tourniquet-induced nerve injuries of the lower extremities.
• Tourniquet nerve injury is directly related to high tourniquet compression pressures and not necessarily the duration of tourniquet inflation. The Esmarch bandage tourniquet is associated with a higher incidence of nerve injury than the pneumatic tourniquet. Nerve injury from tourniquet use results from mechanical pressure under the cuff, which increases endoneural microvascular permeability and edema, ultimately leading to axon damage.
• Nerve injury is typically observed at the proximal and distal edges of the tourniquet.

Systemic Effects

Metabolic

• Ischemic byproducts, potassium and lactate, increase after the tourniquet is deflated. After an inflation duration of 60-120 minutes, potassium increases by a mean of 0.28 mmol/L. Lactate increases to a mean peak of 2.13.²
• These metabolic effects persist for 30 minutes. Hypercarbia and elevated lactate levels cause a temporary metabolic acidosis for 10-30 minutes, with more severe acidosis observed at 4 minutes post-tourniquet deflation.² 
• Two minutes following deflation, O₂ consumption increases by 55% and CO₂ production rises by 80%. These return to pre-deflation values within 8 minutes. All of the aforementioned metabolic changes depend on the duration of inflation, rather than on tourniquet occlusion pressure.²

Cardiovascular

• Inflation of arterial tourniquets increases circulating blood volume and, in turn, systemic vascular resistance. This results in a transient elevation of CVP and systolic blood pressure (SBP). There are reported cases of circulatory overload and cardiac arrest in patients with bilateral thigh tourniquets.⁸ 30-60 minutes after inflation, heart rate (HR) and blood pressure (BP) increase, and are believed to be due to tourniquet pain. This phenomenon can be resistant to analgesics and a deeper depth of anesthesia. Tourniquet deflation produces a 15-minute reduction in CVP and arterial BP as blood volume redistributes back into the ischemic limb.²

Cerebral Circulation

• The hypercapnia that develops after tourniquet deflation can increase the velocity of middle cerebral artery blood flow by 50% 2-4 minutes after deflation. Cerebral blood flow (CBF) returns to pre-deflation levels within 10 minutes.2 Due to the correlation with hypercapnia and elevated intracranial pressure (ICP), caution is advised in patients with pre-existing elevated ICP. Hyperventilation can be used to prevent elevations in EtCO₂, CBF, or ICP.

Respiratory

• Tourniquet deflation allows for CO₂-rich venous blood from the ischemic limb to enter systemic circulation. EtCO₂ levels peak at 1 minute and return to baseline levels in 10 minutes. Hypercarbia is more pronounced when lower-extremity tourniquets are used. This can be counteracted by increasing minute ventilation by 50% from baseline for 5 minutes during tourniquet deflation.²

Hematologic

• Hematologic changes during tourniquet use in surgery are multifactorial. Surgical pain and tourniquet inflation elicit catecholamine release, which promotes platelet aggregation and, consequently, a transient hypercoagulable state. Multiple studies have not shown a direct correlation between the use of arterial tourniquets and an increased incidence of postoperative deep venous thrombosis (DVT).⁹ In the absence of tourniquets, orthopedic surgeries that involve the medullary cavity, such as total knee arthroplasty, have revealed small and large venous emboli via continuous transesophageal echocardiogram recordings.¹⁰
• However, a recent meta-analysis indicated that lower-extremity tourniquets in total knee arthroplasty may increase the risk of DVT, which warrants further study.¹¹ There may be contraindications to tourniquet use in patients with a history of DVT or increased risk of DVT, such as patients with trauma or extended periods of immobilization. Additionally, early perioperative low-dose heparin has been suggested for total joint arthroplasty to prevent venous emboli.
• During tourniquet inflation, there is an accumulation of antithrombin 3 and the thrombomodulin-protein C anticoagulation system in the ischemic limb. Tourniquet deflation releases these proteins, creating a brief hypocoagulable state that lasts up to 30 minutes. This hypocoagulable state has been ascribed to post-tourniquet bleeding.

Temperature

• Inflation of arterial tourniquets increases core temperature by reducing heat loss from the distal skin of the ischemic limb and by reducing heat transfer from the core to the periphery. In contrast, deflating the tourniquet allows cooler venous blood from the exsanguinated limb to return and redistributes body heat, resulting in a temporary drop in body temperature.

Tourniquet Pain^1,2

• Tourniquet pain is characterized by vague, dull pain in the ischemic limb. Tourniquet inflation is tolerated for 31 min before the patient reports pain. This time is extended to 45 minutes when patients are sedated.
• During general anesthesia, tourniquet pain is identified by increased HR and BP. The increase in BP is caused, in part, by an adaptive immune response to pain.
• Loss of sensation to touch has a slower onset and a faster resolution than loss of sensation to pinprick. Therefore, neuraxial anesthesia with adequate dermatomal blockade of sensation may not prevent elevated HR and BP that occur with tourniquet pain.
• The sensation of tourniquet pain is largely due to activation of type C unmyelinated nerve fibers. These type C fibers are normally hindered by larger, myelinated A-delta nerve fibers. Mechanical compression with a tourniquet slows and eventually stops nerve conduction much earlier in the larger A-delta fibers (30 min after inflation), leaving the C-type nerve fibers unregulated. Additionally, tourniquet compression induces prostaglandin release, sensitizing pain receptors and increasing pain perception. Limb ischemia also directly activates NMDA receptors, thereby inducing central sensitization.
• Many agents have been used to treat tourniquet pain, including deepened anesthesia, infiltration with local anesthetic (LA), topical LA cream, IV opioids, clonidine, neuraxial anesthesia, and peripheral nerve blocks. These modalities are typically combined for enhanced effect, but the definitive treatment for tourniquet pain is cuff deflation.

Recommendations for Tourniquet Use

• Most studies suggest a maximum of 1.5-2 hours of continuous tourniquet inflation to decrease the risk of nerve, muscle, and vascular injury.²
• Several techniques are used to achieve a safe duration of tourniquet application. Tourniquets can be released for 10 minutes every hour. Cooling the limb for 30 minutes can allow for 4 hours of cuff inflation.³
• A double-cuff tourniquet allows for alternate inflation at hourly intervals. Recommended maximum pressure for tourniquets ranges from 190-200 mmHg for upper extremities and 230-250 mmHg for lower extremities.
• The Association of Surgical Technologists recommends choosing an inflation pressure 50 mmHg above SBP for upper extremities and 100 mmHg above SBP for lower limbs, but supports the use of Doppler to confirm arterial occlusion.⁴

Special Considerations

• Tourniquets should be used cautiously in the following patient populations: sickle cell disease, due to the risk of vaso-occlusive crisis; osteogenesis imperfecta, due to the risk of bone fractures; and peripheral vascular disease, due to the risk of thrombosis.

Tourniquet Safety

• It is recommended that specific checks be performed before using a tourniquet to prevent malfunctions, premature deflation, and potential injury.
• Maintenance checks of tourniquet equipment should be performed regularly. The pressure gauge should be frequently calibrated, and the tourniquet should be tested to ensure it’s free of leaks for at least 30 minutes at 400mm Hg.
• The tourniquet should be physically inspected to verify there’s no degradation of connections, cuffs, or tubing.
• During use, tourniquet pressure should be monitored. Proper cuff sizing can reduce the risk of localized complications. The cuff should be sized 7-15 cm larger than the target limb circumference. The point of the largest circumference of the extremity should mark the site of tourniquet placement.
• Padding beneath the cuff should be flattened to avoid excess pressure on the underlying skin. The skin cleansing solution should be completely dry, and the final cuff position should be confirmed before cuff inflation. At agreed-upon intervals, the surgeon should be notified of the duration of inflation.