27.1 Total Joint Arthroplasty, Bone Cement Implantation Syndrome & Tourniquet Physiology

Why This Topic Matters on the NCE

Domain IV.A.8 of the content outline lists orthopedic anesthesia as five sub-topics: arthroscopic procedures, closed reduction, fractures, total joint replacement and arthroplasty, and procedures of the hand and foot. Arthroplasty is where three uniquely orthopedic physiologies appear — cement, tourniquets, and marrow embolization — in an elderly, comorbid population.

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1. Bone Cement Implantation Syndrome

Polymethylmethacrylate (PMMA) is mixed at the field and injected into the prepared femoral canal under pressure. Bone cement implantation syndrome (BCIS) is the resulting constellation of hypoxia, hypotension, dysrhythmias, and occasionally cardiac arrest.

When it happens

Timing is highly predictable and is the reason communication with the surgeon matters:

1. Cementation
2. Prosthesis insertion
3. Reduction of the joint
4. Tourniquet deflation

Mechanisms

• Embolization of fat, marrow, air, and cement particles into the pulmonary circulation from the pressurized medullary canal — this is now regarded as the dominant mechanism
• Release of vasoactive mediators, histamine, and complement activation
• Direct vasodilatory effect of residual circulating methylmethacrylate monomer
• Acute rise in pulmonary vascular resistance with right ventricular strain

Severity grading

Risk factors and prevention

Risk is highest in the elderly, ASA physical status III and IV patients, those with significant cardiopulmonary disease or pulmonary hypertension, patients with pathological or osteoporotic fractures, and hip hemiarthroplasty for fractured neck of femur — the classic BCIS scenario.

Preventive measures:

• Increase the inspired oxygen concentration before cementation and ensure euvolemia
• Communicate: the surgeon should announce cementation
• Surgical measures: medullary lavage to remove marrow debris, a distal vent hole or suction catheter to relieve pressurization, and retrograde cement insertion with a cement gun
• Consider an uncemented prosthesis in the highest-risk elderly patient
• Avoid hypovolemia and avoid excessive anesthetic depth at the moment of cementation

Treatment is supportive: 100 percent oxygen, aggressive volume, vasopressors and inotropes with attention to right ventricular support, and resuscitation as needed.

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2. Fat Embolism Syndrome

Distinct from BCIS in timing and presentation.

• Follows long bone and pelvic fractures, intramedullary reaming, and rarely liposuction.
• Onset is typically 24 to 72 hours after injury, not immediately.
• Gurd criteria — major: hypoxemia, central nervous system depression, petechial rash (axilla, conjunctiva, chest, neck); minor: tachycardia, fever, retinal fat emboli, thrombocytopenia, anemia, raised erythrocyte sedimentation rate, fat globules in urine or sputum.
• The petechial rash is the pathognomonic finding and appears in only about half of cases.
• Treatment is supportive with oxygenation and ventilation support. Early fracture fixation reduces incidence. Corticosteroid prophylaxis remains controversial and is not standard.

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3. Tourniquet Physiology

Pneumatic tourniquets create a bloodless field but produce systemic effects that appear on the exam repeatedly.

Pressure and time

• Inflation pressure: roughly 100 mmHg above systolic for the upper limb and 100 to 150 mmHg above systolic for the lower limb, or set from a measured limb occlusion pressure, which is the more modern approach and generally allows lower pressures.
• Duration: aim to keep total inflation under 2 hours. If longer is required, deflate for 10 to 15 minutes to reperfuse before reinflating.
• Apply over adequate padding, at the widest practical cuff, on the proximal limb.

On inflation

• Autotransfusion of roughly 500 to 800 mL from a lower limb into the central circulation; bilateral inflation can precipitate failure in a patient with poor cardiac reserve
• Rise in central venous pressure and systemic blood pressure

Tourniquet pain

A dull, aching, poorly localized pain that begins 45 to 60 minutes after inflation, accompanied by hypertension and tachycardia even under an apparently adequate block or anesthetic. It is attributed to C-fiber-mediated transmission that escapes local anesthetic blockade as the block regresses. It resolves rapidly on deflation.

On deflation

A cluster of predictable, simultaneous changes:

• Fall in systemic blood pressure from reperfusion of a dilated limb and washout of vasoactive metabolites
• Rise in end-tidal and arterial carbon dioxide as accumulated CO2 washes back into the circulation — a spike in end-tidal CO2 immediately after deflation is expected, and in a neurosurgical patient could raise intracranial pressure
• Hyperkalemia and lactic acidosis from washed-out ischemic metabolites
• Fall in core temperature
• Embolic showers detectable on transesophageal echocardiography

Complications

• Nerve injury — the most common tourniquet complication, from direct compression at the cuff edge. The radial nerve is most vulnerable in the upper limb.
• Rhabdomyolysis and compartment syndrome with prolonged inflation
• Skin injury from preparation solution wicking under the cuff
• Tourniquets are avoided or used with great caution in sickle cell disease, severe peripheral vascular disease, and previously irradiated or infected limbs

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4. Total Joint Arthroplasty

Anesthetic technique

Neuraxial anesthesia for hip and knee arthroplasty is associated with less blood loss, lower venous thromboembolism rates, and reduced transfusion compared with general anesthesia in observational and some randomized data, although mortality differences are not consistently demonstrated. Multimodal regional analgesia is standard:

Other essentials

• Tranexamic acid, typically 1 g intravenously before incision, substantially reduces blood loss and transfusion in arthroplasty and is now near-universal.
• Venous thromboembolism prophylaxis timing must be reconciled with ASRA neuraxial guidelines before catheter placement or removal.
• Antibiotic prophylaxis timed before tourniquet inflation, since inflation stops delivery to the limb.

Positioning

• Lateral decubitus for total hip arthroplasty: axillary roll, careful dependent-eye and ear protection, and brachial plexus protection.
• Beach chair position for shoulder surgery is a recurring exam topic. Cerebral hypoperfusion has caused catastrophic neurologic injury. The blood pressure at the circle of Willis is lower than the cuff pressure at the arm by approximately 0.77 mmHg per centimeter of vertical height difference (equivalently about 2 mmHg per inch), so a cuff reading of 100 mmHg with the head 25 cm above the cuff corresponds to roughly 81 mmHg at the brain. Measure at the level of the external auditory meatus or correct for the gradient, and avoid permissive hypotension in this position.

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Exam Traps

• BCIS occurs at cementation, prosthesis insertion, joint reduction, and tourniquet deflation. Raise the FiO2 and ensure euvolemia before cementation.
• Fat embolism appears 24 to 72 hours later with a petechial rash — BCIS is immediate.
• Tourniquet deflation raises end-tidal CO2 and potassium and drops blood pressure.
• Tourniquet pain starts at 45 to 60 minutes and is C-fiber mediated.
• In the beach chair position, correct arm cuff pressure by 0.77 mmHg per cm to estimate cerebral perfusion.