What medications should be given before aortic cross‑clamping in an adult undergoing open aortic surgery?

Medications Prior to Aortic Cross-Clamping

Heparin is the only medication universally required before aortic cross-clamping in open aortic surgery, administered after aortic dissection and before applying the clamp. 1

Anticoagulation (Mandatory)

• Systemic heparinization must be administered after the aorta is dissected and immediately before cross-clamping to prevent thrombosis in the clamped segment and distal vessels. 1
• The standard dose is typically 100-150 units/kg IV, titrated to achieve an activated clotting time (ACT) >250-300 seconds, though specific dosing protocols vary by institutional practice and surgical approach.

Infection Prophylaxis (Mandatory)

• Surgical antibiotic prophylaxis must be administered before skin incision (not before cross-clamping specifically) to reduce wound infection and endocarditis risk, which occurs in 1-5% of cases when timing is inadequate. 2

Spinal Cord Protection (Selective Use)

Methylprednisolone

• Methylprednisolone 30 mg/kg IV may be given both before and after aortic occlusion to reduce spinal cord edema and enhance free-radical scavenging, particularly in thoraco-abdominal aortic repairs where spinal cord ischemia risk is highest (6-8%). 1, 2
• This carries a Class IIb recommendation (may be reasonable) from the American Heart Association. 2

Mannitol

• Mannitol 0.25-1.0 g/kg IV before cross-clamping may modulate ischemic spinal cord injury through osmotic diuresis and reduction of spinal cord edema. 2
• However, mannitol carries a Class III (harm) recommendation when used solely for renal protection during descending aortic surgery, as it has not demonstrated renal benefit. 2

Hemodynamic Management (Context-Dependent)

For Acute Aortic Dissection Requiring Surgery

• Intravenous esmolol must be started immediately to achieve heart rate ≤60 bpm before any vasodilator, reducing aortic wall shear stress by lowering left ventricular ejection force. 3, 2

• Esmolol's ultra-short half-life (5-15 minutes) permits rapid titration. 3

• Target systolic blood pressure is 100-120 mmHg after adequate heart rate control. 3, 2

• Sodium nitroprusside, nicardipine, or clevidipine may be added only after adequate beta-blockade if systolic BP remains >120 mmHg. 3, 2

• Vasodilators must never be used alone before beta-blockade because they provoke reflex tachycardia and can worsen dissection propagation (Class III - harm). 3, 2

For Elective Thoracic Aortic Aneurysm Surgery

• Moderate systemic hypothermia (≈32°C) should be induced before cross-clamping in thoracic aortic aneurysm surgery, as it is associated with improved outcomes and is generally well tolerated. 2
• This carries a Class IIa recommendation (moderate benefit). 2
• Excessive hypothermia can precipitate atrial or ventricular fibrillation. 2

Renal Protection (Not Recommended)

• Pre-operative hydration to optimize volume status is reasonable (Class IIb) before cross-clamping in open descending aorta repairs. 2
• Furosemide, mannitol (when used only for renal protection), and dopamine carry Class III (harm) recommendations for routine renal protection during descending aortic surgery, as they have not demonstrated benefit. 2

Monitoring Requirements Before Cross-Clamping

• Invasive arterial line placement (preferably right radial) must be established for continuous accurate blood pressure monitoring (Class I). 2
• Bilateral arm pressures should be measured to exclude pseudo-hypotension from arch branch obstruction. 2
• At least one large-volume IV line (peripheral or central) must be secured prior to cross-clamping (Class I). 2
• Immediate defibrillator access with pre-applied pads is required before cross-clamping (Class I). 2

Critical Pitfalls to Avoid

• Do not administer vasodilators before beta-blockade in aortic dissection—this practice is harmful and may exacerbate the dissection (Class III - harm). 3, 2
• Do not rely on furosemide, mannitol, or dopamine for renal protection during descending aortic repairs (Class III - harm). 2
• Avoid volume depletion before cross-clamping—underfilled ventricles can precipitate rapid hemodynamic deterioration, especially in patients with severe left ventricular hypertrophy (Class I). 2

Adjunctive Spinal Cord Protection Measures

• Cerebrospinal fluid drainage is recommended (Class I, Level B) in surgery of the thoraco-abdominal aorta to reduce the risk of paraplegia, with continuation up to 72 hours post-operatively to prevent delayed onset. 1
• The risk of paraplegia after thoraco-abdominal repair is 6-8%, and procedural measures including permissive systemic hypothermia (34°C) and re-attachment of distal intercostal arteries between T8 and L1 are beneficial. 1
• Spinal cord tamponade from increased spinal fluid pressure after aortic clamping can contribute to spinal cord infarction. 4, 5