Off-Pump Cardiac Bypass Surgery

Take home messages

• Off-pump surgery involves grafting a new vessel, usually the internal mammary artery, onto the obstructed vessel while the heart is still beating

I'll just let that sink in for a second.

• To do this, the heart is stabilised in the pericardium and the area of interest essentially pinned in place while the rest of the heart continues to beat around it
• Clearly, this can have profound haemodynamic effects that the anaesthetist needs to anticipate and manage

The Surgical Technique

If you do nothing else today, pop the kettle on and watch this insanely cool video on how this whole thing works.

There's also this video on aortic cannulation for 'on-pump' surgery which is interesting.

A bit of history

Off pump surgery has been around since the 1960s, but the invention of bypass rather took over and the off pump techniques took somewhat of a back seat. However since the 1980s there has been more interest in the off-pump option, largely because you avoid all the potential complications of bypass, and it may well be a better option for a certain cohort of patients.

If you're wondering who in the world has the best answer to the question:

"Tell me about a time you dealt with stress"

Well, on February 18, 2012, these guys performed a successful off-pump coronary artery bypass operation on Emperor Akihito.

Yes.

Emperor.

Anaesthetic Techniques

• Many places still employ the good old fashioned combination of high dose opioids, volatiles and propofol
• Isoflurane and sevoflurane may have the added benefit of preconditioning the heart muscle against the inevitable intraoperative ischaemia
• Some places use spinal or thoracic epidural anaesthesia as well as GA

• A key aim is to avoid arrhythmias, which is easier said than done, but one can consider giving 5g of magnesium after induction (slowly please) and maintaining potassium above 4.5mmol/litre

Anticoagulation

Every other surgeon: "It's not safe to operative above an INR of 1.4"

Cardiothoracic surgeons: "Give another trillion units of heparin as I make a hole in the aorta"

Heparinisation is usually given prior to dividing the internal mammary artery, and 1–2 mg kg⁻¹ is usually enough and reversal is with protamine.

Haemodynamics

There are three main reasons the blood pressure can be all over the place during handling of the heart:

• It's tilted such that the blood has to flow upwards into the ventricles, needing a greater filling pressure to maintain cardiac output
• The retractors used to hold it in place unsuprisingly restrict the ability of the ventricles to fill effectively
• The change in orientation of the heart can distort the valves and lead to substantial regurgitation

Your aim as the anaesthetist is to maintain a mean arterial pressure above 70mmHg, with a well-filled and preferably slow-beating heart.

Esmolol is your friend here, and you can pace if it's too slow.

Monitoring

Clearly an ECG is going to be less accurate when the heart isn't really in the chest anymore, however you can still detect ischaemia with a 12 lead trace, especially if monitoring the trend of ST elevation over time.

The same applies to trans-oesophageal echocardiography - it usually produces poor images given the heart is being lifted away from the oesophagus, but it can still be of some use, so is often employed given it is fairly low risk as an intervention.

Invasive arterial blood pressure monitoring and central venous catheterisation probably goes without saying.

Oh and remember to say 'AAGBI' or something similar in your viva.

Outcomes

This seems a little contentious.

Previously, it was reported, according to the National Adult Cardiac Surgery Database, that there was a "reduction in risk adjusted mortality from 2.9% in CABG to 2.3%" for off-pump surgery.

Apparently the complication rate was also reduced from 12% to 8%.

However if you read the tweets below, it may not seem so clear cut.

Useful Tweets

References and Further reading:

Anaesthesia for off-pump coronary artery surgery

Off-pump coronary artery surgery was first developed in the 1960s. The subsequent introduction of cardiopulmonary bypass (CPB) with bubble oxygenators and cardi

OUP AcademicDavid A Hett, FRCA

Off‐pump coronary artery bypass surgery: physiology and anaesthetic management†

Abstract. Increasing interest is being shown in beating heart (off‐pump) coronary artery surgery (OPCAB) because, compared with operations performed with cardio

OUP AcademicP.‐G. Chassot

Anaesthesia for minimally invasive cardiac surgery

Significant advances in cardiac surgery followed the introduction of cardiopulmonarybypass (CPB), which was first established in the early 1950s. Over time, refinementsin surgical and anaesthetic techniques combined with improved technology and the useof intraoperative transoesophageal echocardio…

BJA EducationSearch for articles by this author

Recommended Textbooks:

• CRQs for the Final FRCA - Akuji, Martin, Chambers and Thomas
• CRQs and SBAs for the Final FRCA: questions and detailed answers - Sumner, Allen, Feneley, Raithatha

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