Management of Sudden Intraoperative Hypotension During CABG

Immediate Assessment and Diagnosis

Perform a rapid bedside evaluation for hemodynamic stability by checking for end‑organ dysfunction (e.g., altered mental status, reduced urine output, worsening acidosis) 3.
Record precise vital parameters—including arterial pressure, heart rate, cardiac output, systemic vascular resistance, and pulmonary artery pressures when available 5.
Consider acute graft failure or thrombosis as the leading cause of early ischemia in the immediate post‑anastomosis period; this should trigger preparation for urgent coronary angiography, vasopressor support, and possible intra‑aortic balloon pump (IABP) placement 1, 2.

Initiate norepinephrine as the first‑line vasopressor to keep mean arterial pressure ≥ 65 mmHg and sustain systemic vascular resistance 6.
Add inotropic agents (dobutamine, milrinone, or epinephrine) when cardiac output remains low despite adequate preload; these drugs have neutral or beneficial effects on pulmonary vascular resistance 5.

Use a passive leg‑raise test to assess fluid responsiveness before giving fluids 3.
If the test raises arterial pressure, give a crystalloid bolus (e.g., normal saline or balanced electrolyte solution) 4.
If the test does not improve pressure, prioritize vasopressor or inotropic therapy rather than additional volume 4.

Consider IABP support in the setting of systemic hypotension or severe left‑ventricular dysfunction because it enhances coronary perfusion pressure 1.
Place the IABP before proceeding to emergency surgical or percutaneous interventions when hemodynamic instability persists 2.
Perform urgent coronary angiography to identify the anatomic cause of ischemia when graft failure is suspected 1.
Emergency percutaneous coronary intervention (PCI) of focal graft stenosis or acute graft thrombosis can relieve ischemia in most patients 1; balloon dilation across suture lines is safe within days after surgery 1.

Prefer mechanical thrombectomy during PCI over intracoronary fibrinolysis in the first postoperative week to lower bleeding risk 1.
Deploy intracoronary stents when feasible to improve immediate patency 1.
Use adjunctive antiplatelet therapy cautiously because of recent surgery 1.

Keep systolic systemic arterial pressure higher than systolic pulmonary arterial pressure to protect right‑ventricular perfusion 5.
Administer inhaled nitric oxide at ~20 ppm to acutely reduce pulmonary vascular resistance and boost cardiac output without harming systemic vascular resistance 5.
Choose dobutamine over milrinone for its shorter half‑life when hypotension is a concern 5.
Consider replacement‑dose vasopressin to counteract drops in systemic vascular resistance 5.

Maintain continuous arterial blood‑pressure and electrocardiogram monitoring to detect ongoing ischemia or arrhythmias 8.
Serially assess systemic perfusion markers (lactate, mixed/central venous oxygen saturation, urine output, mental status) 6.
Limit peak airway pressures to < 30 cm H₂O and positive‑end‑expiratory pressure to ≤ 10 cm H₂O to avoid increasing right‑ventricular afterload 5.
Avoid permissive hypercapnia; acidosis and elevated CO₂ raise pulmonary vascular resistance 5.
Target systemic oxygen saturation > 90 % because hypoxia acutely increases pulmonary vascular resistance 5.

Do not postpone urgent coronary angiography when acute graft failure is suspected; early intervention markedly improves outcomes 1.
Do not give large fluid volumes without first testing responsiveness; roughly half of hypotensive patients will not respond and will need vasopressor or inotropic support 3.
Avoid using phenylephrine as the sole vasopressor in the presence of bradycardia, as it can cause reflex bradycardia especially when preload‑independent 4.
Do not abruptly stop vasopressors once started, as sudden withdrawal can precipitate hemodynamic collapse 6.
Do not proceed to emergency redo CABG when target anatomy is unsuitable or a no‑reflow state exists; alternative percutaneous strategies are preferred 9.