[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anaesthesia and ICU](https://durgical.com/en/anaesthesia/) › [By patient and by surgery](https://durgical.com/en/anaesthesia/areas/by-patient/) › Anaesthesia for cardiac surgery, in principle

# Anaesthesia for cardiac surgery, in principle

- Patient and surgery

Heart operations often stop the heart while a machine pumps and oxygenates the blood; the anaesthetist protects the heart, brain and kidneys throughout.

Updated Nov 13, 2026

## Key points

- Full heparinisation is confirmed by the activated clotting time before bypass and reversed with protamine after it.
- Protamine can cause hypotension, pulmonary hypertension and anaphylactoid reactions; give it slowly and watch closely.
- Bypass causes haemodilution, inflammation, platelet dysfunction and fibrinolysis; tranexamic acid reduces bleeding.
- Weaning from bypass needs rewarming, a stable rhythm (pacing if needed), restarted ventilation, and support for a stunned heart.
- Enhanced recovery after cardiac surgery: opioid-sparing analgesia, glucose control, early extubation, delirium and kidney protection.

## What it is

Cardiac surgery, most often coronary artery bypass grafting and valve repair or replacement, is commonly done on cardiopulmonary bypass: blood is drained from the venous side, oxygenated and pumped back into the arterial circulation while the heart is arrested with cardioplegia and the lungs rest. The anaesthetist manages a patient with little cardiac reserve through induction, full anticoagulation with heparin before bypass (checked with the activated clotting time), the bypass period, weaning from bypass, and reversal of heparin with protamine. Bypass itself causes haemodilution, a systemic inflammatory response, platelet dysfunction, fibrinolysis and often deliberate cooling, so bleeding, coagulopathy and vasoplegia are expected problems. Transoesophageal echocardiography, an arterial line and central venous access are standard. Enhanced recovery after cardiac surgery (ERACS) applies the enhanced-recovery idea to this setting: correct anaemia and poor glucose control before surgery, avoid long fasting, use multimodal opioid-sparing analgesia, antifibrinolytics, goal-directed fluids and inotropes, tight glucose control, prevention of acute kidney injury and delirium, early extubation within hours of arrival in intensive care, and early mobilisation.

## What changes in this patient

- Patients arrive with ischaemia, poor ventricular function or a severe valve lesion, so induction must be slow and controlled.
- Cardiopulmonary bypass replaces the heart and lungs; cardioplegia arrests and protects the myocardium while the surgeon works.
- Bypass dilutes the blood, triggers inflammation, damages platelets and activates fibrinolysis, so bleeding is expected.
- After bypass the heart is often stunned and the vessels dilated (vasoplegia): inotropes and vasopressors are commonly needed.
- Transoesophageal echocardiography guides surgery, checks the repair, detects air and shows ventricular function.
- Atrial fibrillation, acute kidney injury, delirium and stroke are common after cardiac surgery.

## Anaesthetic plan (and why)

- Optimise before surgery: correct anaemia, control glucose, stop smoking, improve nutrition — each lowers complications and transfusion.
- Shorten fasting and consider a carbohydrate drink where protocol allows — this reduces insulin resistance and patient discomfort.
- Place an arterial line before induction, then central access and transoesophageal echocardiography — they guide every later step.
- Induce slowly with drugs chosen for stability — the poorly functioning heart tolerates neither hypotension nor tachycardia.
- Give heparin and confirm the activated clotting time before bypass — clotting in the circuit is a catastrophe.
- Give an antifibrinolytic such as tranexamic acid — it reduces bleeding and transfusion after bypass.
- Before weaning, rewarm, correct potassium and acid-base, restore rhythm or pace, and restart ventilation — the heart needs all of these to take over.
- Reverse heparin slowly with protamine and treat bleeding by the coagulation tests — guided products avoid needless transfusion.
- Use multimodal opioid-sparing analgesia and aim for early extubation in intensive care — it speeds recovery and reduces lung complications.
- Control glucose, avoid kidney toxins and screen for delirium after surgery — these are common and partly preventable harms.

## The phases of a cardiac operation on bypass

| Phase | What happens | Anaesthetic focus |
| --- | --- | --- |
| Induction and pre-bypass | Lines, echo, sternotomy, cannulation | Stability; heparin and activated clotting time |
| On bypass | Heart arrested with cardioplegia, machine perfuses | Perfusion pressure, depth of anaesthesia, temperature, glucose |
| Weaning | Heart takes over the circulation | Rewarm, rhythm, ventilation, inotropes and vasopressors |
| After bypass | Protamine, haemostasis, chest closure | Protamine reactions, bleeding, tamponade |
| Intensive care | Recovery, early extubation | Analgesia, glucose, kidney, delirium, atrial fibrillation |

## Risks and complications

- Bleeding and cardiac tamponade: rising drain output, falling pressure and rising filling pressures after surgery.
- Low cardiac output from a stunned heart, and vasoplegia with low resistance after bypass.
- Protamine reactions: hypotension, acute pulmonary hypertension and right heart failure, or anaphylaxis.
- Postoperative atrial fibrillation, which is common and raises the risk of stroke.
- Stroke and delirium from emboli, low flow or inflammation; acute kidney injury from low flow and inflammation.
- Heparin-induced thrombocytopenia, sternal wound infection and prolonged ventilation.

## Next step

- Hand over in intensive care with the bypass and clamp times, the drugs running, the echo findings and any bleeding problem.
- Call the surgeon and a senior at once for rising drain output with falling pressure: tamponade needs reopening.
- Aim for early extubation and mobilisation once warm, stable and not bleeding.
- Watch for atrial fibrillation, delirium and acute kidney injury every day, and treat them early.
- Plan cardiac rehabilitation and follow-up of the repair with the cardiology team.

## Test yourself

Think of the answer, then tap the question to see it.

## How is anticoagulation for cardiopulmonary bypass checked and reversed?

Heparin is given and the activated clotting time is checked before bypass starts; after bypass heparin is reversed with protamine, given slowly.

## Which adverse reactions can protamine cause?

Systemic hypotension, acute pulmonary hypertension with right heart failure, and anaphylactic or anaphylactoid reactions.

## Why do patients bleed after cardiopulmonary bypass?

Residual heparin, haemodilution of clotting factors, platelet dysfunction, fibrinolysis and hypothermia all impair clotting.

## What are the main elements of enhanced recovery after cardiac surgery?

Preoperative optimisation, short fasting, antifibrinolytics, multimodal opioid-sparing analgesia, glucose control, early extubation, delirium and kidney protection, early mobilisation.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anaesthesia/anaesthesia-for-cardiac-surgery-in-principle/)

## Elsewhere in DurgiPedia

- [Cardiac output and what sets it](https://durgical.com/en/physiology/cardiac-output-and-what-sets-it/)
- [Coronary circulation and myocardial ischemia](https://durgical.com/en/physiology/coronary-circulation-and-myocardial-ischemia/)
- [Echocardiography: transthoracic and transoesophageal](https://durgical.com/en/clinical-skills/echocardiography-transthoracic-and-transoesophageal/)
- [Arterial line insertion](https://durgical.com/en/clinical-skills/arterial-line-insertion/)
- [Pericardiocentesis](https://durgical.com/en/clinical-skills/pericardiocentesis/)

## Connections

## Related 8

- [The patient with heart disease having non-cardiac surgery](https://durgical.com/en/anaesthesia/the-patient-with-heart-disease-having-non-cardiac-surgery/)
- [Enhanced recovery after surgery (ERAS)](https://durgical.com/en/anaesthesia/enhanced-recovery-after-surgery/)
- [Haemodynamic monitoring: arterial line, CVP, cardiac output and lactate](https://durgical.com/en/anaesthesia/haemodynamic-monitoring-arterial-line-cvp-cardiac-output-and-lactate/)
- [Massive haemorrhage in theatre](https://durgical.com/en/anaesthesia/massive-haemorrhage-in-theatre/)
- [Vasopressors and inotropes by receptor and mechanism](https://durgical.com/en/anaesthesia/vasopressors-and-inotropes-by-receptor-and-mechanism/)
- [Transfusion thresholds in the ICU](https://durgical.com/en/anaesthesia/transfusion-thresholds-in-the-icu/)
- [Postoperative delirium](https://durgical.com/en/anaesthesia/postoperative-delirium/)
- [Perioperative hypothermia and shivering](https://durgical.com/en/anaesthesia/perioperative-hypothermia-and-shivering/)

## Related conditions 7

- [Stable angina](https://durgical.com/en/conditions/stable-angina/)
- [Myocardial Infarction (Heart Attack)](https://durgical.com/en/conditions/myocardial-infarction/)
- [Aortic Valve Stenosis](https://durgical.com/en/conditions/aortic-valve-stenosis/)
- [Mitral regurgitation](https://durgical.com/en/conditions/mitral-regurgitation/)
- [Atrial fibrillation](https://durgical.com/en/conditions/atrial-fibrillation/)
- [Cardiac tamponade](https://durgical.com/en/conditions/cardiac-tamponade/)
- [Cardiogenic shock](https://durgical.com/en/conditions/cardiogenic-shock/)

## In Pharmacology 9

- [Heparin](https://durgical.com/en/pharmacology/heparin/)
- [Protamine sulfate](https://durgical.com/en/pharmacology/protamine-sulfate/)
- [Tranexamic acid](https://durgical.com/en/pharmacology/tranexamic-acid/)
- [Milrinone](https://durgical.com/en/pharmacology/milrinone/)
- [Dobutamine](https://durgical.com/en/pharmacology/dobutamine/)
- [Epinephrine](https://durgical.com/en/pharmacology/epinephrine/)
- [Norepinephrine](https://durgical.com/en/pharmacology/norepinephrine/)
- [Vasopressin](https://durgical.com/en/pharmacology/vasopressin/)
- [Amiodarone](https://durgical.com/en/pharmacology/amiodarone/)

[← All of anaesthesia](https://durgical.com/en/anaesthesia/)

Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: [Anesthetic Management for Enhanced Recovery After Cardiac Surgery (ERACS)](https://www.ncbi.nlm.nih.gov/books/NBK572107/) (StatPearls (NCBI Bookshelf), 2023).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anaesthesia/anaesthesia-for-cardiac-surgery-in-principle/