During coronary artery bypass grafting, after the third graft, the patient develops sudden hypotension. What is the immediate management and how should we proceed?

Immediate Management of Sudden Hypotension During CABG After Third Graft

Immediately assess for acute graft failure or thrombosis as the most likely cause, confirm hemodynamic stability, and prepare for urgent coronary angiography while initiating vasopressor support and considering intra-aortic balloon pump placement if hypotension persists despite initial resuscitation. 1

Initial Assessment and Stabilization

Immediate Diagnostic Steps

• Perform rapid bedside assessment to determine if the patient is hemodynamically stable or unstable by checking for signs of end-organ dysfunction including altered mental status, decreased urine output, and worsening acidosis 1
• Document exact blood pressure, heart rate, cardiac output, systemic vascular resistance, and pulmonary artery pressures if available 1
• Assess for acute graft failure or thrombosis as the primary cause, which occurs most commonly in the immediate post-anastomosis period and represents the leading etiology of early ischemia during CABG 1
• Evaluate for other intraoperative causes including protamine reaction (which can cause catastrophic pulmonary vasoconstriction and noncardiogenic pulmonary edema), air embolism, or myocardial ischemia from incomplete revascularization 2

Hemodynamic Support Algorithm

For hypotension with adequate preload:

• Initiate norepinephrine as first-line vasopressor to maintain mean arterial pressure ≥65 mmHg and systemic vascular resistance 3, 4
• Consider low-dose vasopressin (0.03 U/min) as adjunctive therapy, particularly if the patient was on ACE inhibitors preoperatively, as this prevents post-CPB hypotension without increasing systemic vascular resistance excessively 5
• Use inotropes (dobutamine, milrinone, or epinephrine) if cardiac output is reduced despite adequate preload, as these agents have neutral or beneficial effects on pulmonary vascular resistance 1

For hypotension with suspected hypovolemia:

• Perform passive leg raise test to assess fluid responsiveness before administering volume 1
• If passive leg raise increases blood pressure, administer crystalloid bolus (normal saline or Ringer's lactate) 1, 4
• If passive leg raise does not correct hypotension, focus on vascular tone and inotropy rather than additional fluid 1

Critical Interventions for Persistent Hypotension

Intra-aortic balloon pump consideration:

• IABP support should be strongly considered in the context of systemic hypotension or severe LV dysfunction, as flow in vein graft conduits is pressure-dependent and IABP improves coronary perfusion pressure 1
• Place IABP before proceeding to emergency interventions if severe hemodynamic instability persists 1

Urgent coronary angiography:

• Urgent coronary angiography is indicated to define the anatomic cause of ischemia when acute graft failure is suspected 1
• Emergency PCI of focal graft stenosis or recanalization of acute graft thrombosis may successfully relieve ischemia in the majority of patients 1
• Balloon dilation across suture lines can be accomplished safely within days of surgery 1

Specific Management Based on Etiology

Acute Graft Thrombosis

• Emergency PCI with mechanical thrombectomy is preferred over intracoronary fibrinolysis during the first week postoperatively due to lower hemorrhage risk 1
• Deploy intracoronary stents if feasible to enhance immediate results 1
• Administer adjunctive antiplatelet therapy cautiously given recent surgery 1

Right Ventricular Dysfunction

• Maintain systolic systemic arterial pressure higher than systolic pulmonary arterial pressure to prevent right ventricular ischemia, as RV perfusion occurs during both systole and diastole 1
• Employ inhaled nitric oxide at 20 parts per million to acutely decrease pulmonary vascular resistance and improve cardiac output without detrimental effects on systemic vascular resistance 1
• Use dobutamine over milrinone due to shorter half-life in the face of hypotension risk 1
• Consider replacement-dose vasopressin to offset potential drops in systemic vascular resistance 1

Vasoplegic Syndrome

• Implement retrograde autologous priming, stepwise CPB initiation, and pulsatile flow techniques to reduce early hypotensive phenomena, though these are preventive rather than therapeutic measures 6
• Administer norepinephrine in 1-ml boluses titrated to effect 6

Monitoring and Ongoing Management

Continuous Monitoring Requirements

• Institute continuous arterial blood pressure and electrocardiogram monitoring to detect ongoing ischemia or arrhythmias 7
• Monitor serial markers of systemic perfusion including lactate, mixed or central venous oxygen saturations, urine output, and mental status 3, 4
• Assess cardiac index, systemic vascular resistance index, and oxygen delivery index if available 6

Ventilation Management

• Maintain peak airway pressures <30 cmH₂O and limit positive end-expiratory pressure to ≤10 cmH₂O to minimize increases in RV afterload 1
• Avoid permissive hypercapnea as acidosis and hypercapnea acutely increase pulmonary vascular resistance 1
• Target systemic oxygen saturation >90% as hypoxia acutely increases pulmonary vascular resistance 1

Critical Pitfalls to Avoid

• Do not delay urgent coronary angiography if acute graft failure is suspected, as early intervention dramatically improves outcomes 1
• Avoid excessive fluid administration without assessing fluid responsiveness, as approximately 50% of hypotensive patients will not respond to volume and require vasopressor or inotropic support instead 1
• Do not use phenylephrine as sole vasopressor if bradycardia is present, as it causes reflex bradycardia especially in preload-independent states 1
• Avoid abrupt discontinuation of vasopressors once initiated, as this can lead to hemodynamic collapse 3
• Do not perform emergency redo CABG if revascularization is impossible due to target anatomy or no-reflow state 1