CABG

Surgical approach

• Access: median sternotomy (most common); occasionally minimally invasive (MIDCAB) via left anterior thoracotomy for LAD grafting
• Conduit harvest
  • LIMA/RIMA (internal mammary) harvested pedicled or skeletonised; LIMA→LAD most common
  • Saphenous vein (open or endoscopic) ± radial artery (requires spasm prophylaxis and adequate collateral flow)
• On-pump CABG (with CPB): cannulation and bypass
  • Systemic heparinisation → aortic cannula + right atrial (two-stage) venous cannula (or bicaval)
  • Initiate CPB; temperature management (often mild hypothermia); haemodilution
  • Aortic cross-clamp; cardioplegia (antegrade via aortic root and/or retrograde via coronary sinus) ± topical cooling
  • Distal anastomoses on arrested heart; proximal anastomoses to aorta (often during partial clamp) or using composite grafts
  • De-airing; remove cross-clamp; reperfusion; wean from CPB; protamine reversal; haemostasis; pacing wires; chest drains; sternal closure
• Off-pump CABG (OPCAB): beating-heart revascularisation
  • Heparinisation to lower target ACT than CPB; heart stabiliser and positioner used
  • Coronary occlusion/shunt during distal anastomosis; haemodynamic instability common with heart displacement (especially posterior vessels)

Anaesthetic management (headline)

• Type of anaesthesia: General anaesthesia with awake arterial line
• Airway: cuffed ETT
• Duration: typically 3–6 hours (longer if complex/multiple grafts, redo, combined procedures)
• Pain: moderate–severe (sternotomy + chest drains). Multimodal opioid-sparing analgesia; aim early extubation where appropriate
• Key aims: maintain myocardial oxygen supply-demand balance; avoid tachycardia/hypotension; ensure anticoagulation/ACT targets; manage CPB physiology; meticulous haemostasis and temperature control

Indications and patient profile

• Indications: prognostic and/or symptomatic benefit in coronary artery disease
  • Left main stem disease, triple vessel disease (esp. with LV dysfunction), proximal LAD disease, diabetes with multivessel disease, refractory angina despite optimal medical therapy/PCI
  • Urgent/emergency CABG: ongoing ischaemia, failed PCI, mechanical complications (rare as isolated CABG), cardiogenic shock in selected cases
• Common comorbidity burden: LV dysfunction, valvular disease, pulmonary hypertension, CKD, carotid disease, frailty, anaemia, diabetes, COPD, obesity, OSA
• Risk stratification: EuroSCORE II (and local models). Use to inform planning (ICU bed, blood products, invasive monitoring, inotropes/MCS readiness)

Preoperative assessment and optimisation

• History/exam: angina class, recent ACS, exercise tolerance, heart failure symptoms, syncope, arrhythmias, prior PCI/stents, bleeding history, stroke/TIA, claudication
• Investigations to review
  • Coronary angiography (targets, LVEDP if available), echocardiography (LV/RV function, valves, pulmonary pressures), ECG
  • Bloods: FBC (anaemia/platelets), U&E (CKD/K+), coagulation, HbA1c, group & save/crossmatch; consider iron studies if anaemic and time allows
  • CXR; spirometry if significant lung disease; carotid duplex if indicated (bruit, prior TIA/stroke, high-risk features per local policy)
• Medication management (typical patterns; follow local protocol)
  • Aspirin usually continued; P2Y12 inhibitors (clopidogrel/ticagrelor/prasugrel) stopped pre-op when possible (bleeding vs ischaemia trade-off)
  • Beta-blockers usually continued (avoid withdrawal tachycardia). Nitrates continued if symptomatic
  • ACEi/ARB: often held on day of surgery if concern about vasoplegia/hypotension (institution-dependent)
  • Anticoagulants: warfarin stopped and bridged only if strong indication; DOACs stopped according to renal function and bleeding risk
  • Diabetes: adjust insulin/agents; SGLT2 inhibitors usually withheld pre-op to reduce ketoacidosis risk
• Optimisation: treat infection, correct anaemia if time, manage heart failure (diuresis), smoking cessation, discuss postoperative ventilation/ICU, consent for transfusion and invasive lines

Monitoring and access

• Standard: ECG (5-lead with ST analysis), SpO2, NIBP, capnography, temperature, urine output
• Invasive: arterial line pre-induction if unstable; central venous access (drug delivery, CVP trends); large-bore peripheral access
• Advanced monitoring (case-dependent): cardiac output monitoring, SvO2, pulmonary artery catheter (selected: severe pulmonary HTN/RV failure/complex), cerebral oximetry (NIRS) where available
• TOE: commonly used; essential in many centres for assessment of ventricular function, volume status, regional wall motion, valve pathology, aortic atheroma, air, and causes of instability
• Defibrillator pads; external pacing availability; warming devices; rapid infuser and cell salvage (if used locally)

Induction and maintenance (key principles)

• Goals: avoid tachycardia, hypotension, hypertension, and myocardial ischaemia; maintain coronary perfusion pressure; preserve RV function; ensure smooth laryngoscopy and sternotomy response control
• Induction: titrated opioid + hypnotic (propofol/etomidate) ± benzodiazepine; neuromuscular blockade (e.g. rocuronium). Consider vasopressor ready (metaraminol/phenylephrine/noradrenaline)
• Maintenance: volatile (isoflurane/sevoflurane) or TIVA; balanced with opioid; consider volatile myocardial preconditioning (evidence mixed but widely used). Maintain depth to prevent sympathetic surges
• Ventilation: avoid hypoxia/hypercapnia (↑PVR), avoid excessive PEEP impairing venous return; lung-protective strategy; recruitment after sternotomy/CPB
• Haemodynamic targets (typical): HR ~50–80 (avoid tachycardia), MAP often 60–80 pre-CPB (individualise; higher if critical carotid/renal disease), maintain sinus rhythm where possible

Anticoagulation, ACT and protamine

• Heparin before cannulation (on-pump) or before coronary occlusion (off-pump). Dose commonly 300–400 IU/kg for CPB (institutional variation)
• ACT targets
  • On-pump: typically ACT > 480 s (or per local protocol/device)
  • Off-pump: often lower target (e.g. ACT 250–350 s), per surgeon preference/protocol
• Heparin resistance: consider antithrombin deficiency (heparin exposure, sepsis, liver disease). Management: additional heparin, AT concentrate or FFP, confirm ACT device/function
• Protamine reversal post-CPB: dose guided by heparin dose/ACT/heparin concentration systems. Give slowly; watch for hypotension, pulmonary hypertension, anaphylactoid reactions
  • High-risk protamine reactions: prior exposure (e.g. NPH insulin), vasectomy, fish allergy (association debated), rapid administration

Cardiopulmonary bypass (CPB): physiology and practical implications

• Core features: non-pulsatile flow, haemodilution, hypothermia (often), systemic inflammatory response, altered coagulation and platelet dysfunction, microemboli risk
• Perfusion targets (typical): pump flow ~2.2–2.6 L/min/m²; MAP often 50–80 mmHg (individualise: chronic HTN, carotid disease)
• Gas exchange on CPB: oxygenator; CO2 management; alpha-stat vs pH-stat strategies (centre-specific; pH-stat more common in deep hypothermia/paediatrics)
• Temperature: hypothermia reduces metabolic rate; rewarming must be controlled to avoid gaseous microemboli and cerebral hyperthermia; aim normothermia at separation
• Electrolytes/acid-base: monitor K+ (cardioplegia-related hyperkalaemia), lactate, ionised Ca2+; treat metabolic acidosis by addressing cause (flow/oxygen delivery)

Myocardial protection and ischaemia management

• Cardioplegia: high K+ arrests heart; may be blood or crystalloid; repeated dosing; antegrade/retrograde routes
• Recognise intra-op ischaemia: ST changes, new regional wall motion abnormality on TOE, haemodynamic deterioration, ventricular arrhythmias
• Management: optimise supply-demand (HR, BP, Hb, oxygenation), treat hypotension (vasopressors), consider nitrates for spasm, inotropes for LV failure, discuss graft issues with surgeon

Weaning from CPB: structured approach

• Prerequisites: normothermia/rewarmed, adequate ventilation, rhythm (sinus/pace), electrolytes corrected (K+, Ca2+, Mg2+), Hb acceptable, lungs recruited, surgical field ready
• Assess with TOE: LV/RV function, volume status, valve function, regional wall motion, tamponade/air, aortic pathology
• Haemodynamic support: vasopressor for vasoplegia (noradrenaline/vasopressin), inotrope for pump failure (dobutamine/adrenaline/milrinone), pacing for brady/AV block
• Common problems at separation
  • LV failure (ischaemia, inadequate protection, graft issue), RV failure (PHTN, air, ischaemia), vasoplegia, bleeding/coagulopathy, tamponade, residual air, arrhythmias
• Mechanical circulatory support (MCS): IABP, VA-ECMO, Impella (centre-dependent). Indications: refractory cardiogenic shock despite optimisation

Bleeding and transfusion strategy

• Causes: surgical bleeding, residual heparin, platelet dysfunction (CPB), hypofibrinogenaemia, dilutional coagulopathy, hyperfibrinolysis
• Approach: quantify blood loss; check ACT; use point-of-care testing where available (TEG/ROTEM) to guide targeted therapy
• Typical components: RBCs (aim Hb per patient/physiology), platelets, FFP, fibrinogen (cryoprecipitate/concentrate), calcium replacement, tranexamic acid (common)
• Re-sternotomy risk: persistent high drain output, haemodynamic instability, rising lactate, tamponade signs; early surgical review

Analgesia and fast-track extubation

• Multimodal: paracetamol, opioids (fentanyl/remifentanil intra-op; morphine/oxycodone post-op), consider ketamine low-dose, magnesium; avoid NSAIDs in CKD/bleeding risk
• Regional adjuncts (centre-specific): parasternal/pectointercostal fascial plane blocks, ESP blocks; neuraxial techniques limited by anticoagulation and bleeding risk
• Fast-track: aim extubation within ~6 hours in suitable patients (stable haemodynamics, normothermia, acceptable bleeding/gas exchange, good analgesia)

Postoperative issues (ICU/HDU)

• Cardiac: low cardiac output syndrome, arrhythmias (AF common), ischaemia/infarction, pacing needs, tamponade
• Respiratory: atelectasis, pleural effusions, pneumonia, pulmonary oedema; manage with physiotherapy, recruitment, diuresis as appropriate
• Renal: AKI risk (CPB, hypotension, emboli); optimise perfusion, avoid nephrotoxins, monitor urine output/creatinine
• Neurological: delirium, stroke, cognitive dysfunction; manage BP, oxygenation, glucose; early mobilisation and delirium prevention bundle
• Glycaemic control: avoid severe hyperglycaemia and hypoglycaemia; insulin infusion protocols common