2.2 Off Pump Bypass

Question 1

a) What are the theoretical advantages of ‘off-pump’ coronary artery bypass grafting (OPCAB)
compared to ‘on bypass’ technique? (35%)

Answer 1

> > Avoidance of complications of CPB:

• Platelet dysfunction.
• Consumption of clotting factors.
• Accelerated fibrinolysis.
• Blood transfusion due to coagulation defects.
• Renal dysfunction.
• SIRS.
• Air emboli.
• Neurological dysfunction.
• Fluid overload/depletion.
• Electrolyte disturbance.

> > Earlier extubation, shorter/no ICU stay, reduced cost.

> > Overall reduced morbidity and mortality.

Question 2

b) What causes haemodynamic instability during OPCAB? (20%)

Answer 2

> > Ischaemia due to vessel anastomosis
(shunts are used to minimise this).

> > Manipulation of the heart for access
to lateral and posterior aspects:
lifting of heart vertically out of pericardial sac, ventricular filling must then
happen vertically upwards,
mitral and tricuspid annulus deformation
resulting in reflux.

> > Impaired filling due to immobilisation device.

> > Arrhythmias induced by ischaemia,
manipulation, reperfusion.

> > Bleeding.

Question 3

c) Which strategies help to minimise this haemodynamic instability? (25%)

Answer 3

> > Good communication between
the anaesthetist and the surgeon.

> > Minimise manipulation, stop if major instability.

> > Periods of ischaemia minimised,
including through the use of shunts.

> > Keep heart rate low/normal:
minimises oxygen requirement,
reduces effect of periods of ischaemia.

> > Monitor and treat electrolyte disturbances:
keep potassium over 4.5 mmol/l;
give magnesium routinely.

> > Ensure that patient is adequately filled,
guided by cardiac output monitoring.

Question 4

d) Outline the measures that help to minimise perioperative hypothermia during OPCAB. (20%)

Answer 4

Comply with NICE guidance on avoidance of perioperative hypothermia:

> > Preoperative:
check patient temperature,
use extra bedding or forced air
warming if necessary.

>> Intraoperatively: monitor temperature; 
minimise periods of leaving patient
uncovered; use warmed fluids, 
forced air warming blanket, under-body
warming mattress, heat conserving hat 
and ambient theatre temperature
at a minimum of 21°C.

> > Postoperatively:
continue to monitor temperature;
use extra bedding and
forced air warming as necessary.

Question 5

Off pump bypass

Answer 5

Don’t know anything about ‘off-pump’ surgery?

Basically, it means not using cardiopulmonary bypass (the pump) to facilitate heart surgery, operating
on the beating heart instead.

An immobilisation device is used to reduce
movement of the area of myocardium being operated on at the time.

Search for a video of off-pump surgery
if you haven’t seen it before.

Think of all the issues that are associated with ‘on-pump’ surgery and what might therefore
be avoided by staying ‘off-pump.’