2.8 Neurological Complications of Bypass Flashcards
a) What are the central neurological complications of coronary artery bypass surgery?
(7 marks)
It hasn’t specified on-pump or off-pump surgery, so you should include the complications of both. Complications of prolonged surgery, surgery in an
arteriopath, the issues related to going on-pump and periods of hypotension should all be included, as well as the specific complications caused by the different surgical approaches.
Central:
» Postoperative cognitive dysfunction – short- and long-term.
> > Stroke: ischaemic, embolic
(from existing patient thrombus/vessel lesions or as a result of CPB) or haemorrhagic.
> > Transient ischaemic attack.
> > Gas emboli.
> > Subtle behavioural or personality changes.
> > Ischaemic spinal cord injury.
> > Delirium.
a) What are peripheral neurological complications of coronary artery bypass surgery other part of a
Peripheral:
» Brachial plexus injury:
central line insertion, positioning,
sternal retraction
(rotation of first rib,
pushes clavicles into
retroclavicular space
putting traction on plexus)
and internal mammary artery (IMA) harvesting (wider
retraction necessary).
> > Ulnar nerve injury:
positioning associated with artery harvesting.
> > Phrenic nerve injury (left phrenic nerve passes between lung and
mediastinal pleura so at greater risk)
with IMA harvesting.
> > Recurrent laryngeal nerve injury:
intubation (prolonged),
surgical dissection,
especially of IMA.
> > Saphenous nerve injury:
damage occurring during saphenous vein
harvesting due to close proximity at ankle.
> > Intercostal nerve damage:
minimally invasive direct coronary artery
bypass (MIDCAB),
where the incision is between
the ribs rather than sternotomy.
b) What are the risk factors for central neurological complications? (6 marks)
Patient factors (these are most significant):
» Age.
> > Hypertension.
> > Hypercholesterolaemia.
> > History of stroke.
> > Diabetes mellitus.
> > Carotid stenosis.
> > Preoperative cognitive dysfunction,
including that due to Alzheimer’s,
Parkinson’s and cerebral vascular disease.
> > Poor left ventricular function.
Surgical factors:
» Duration of surgery
(possibly relating to stress response,
disruption of the blood–brain barrier
and altered autoregulation).
> > Microemboli from diseased aorta
when clamped, cannulated or handled.
> > Microemboli from cardiopulmonary bypass
(CPB) circuit.
> > Rapid rewarming after hypothermia
can cause loss of autoregulation,
resulting in cerebral oedema.
> > Failure to maintain adequate
brain perfusion pressure during CPB.
Anaesthetic factors (least significant):
» Low mean arterial pressure and
so cerebral perfusion pressure.
> > Prolonged deep hypnotic time.
c) How can the incidence of central neurological complications be reduced? (7 marks)
Preoperative:
» Patient assessment,
identification of high-risk patients
and consider whether appropriate to proceed.
Intraoperative:
» Minimally invasive techniques to
reduce overall stress response.
> > Adequate priming of CPB circuit,**
if used, and use of bubble traps and
embolus filters.
> > Surgical care to avoid disrupting
aortic plaques on clamping and cannulation.
> > Maintenance of haemodynamic stability
to ensure adequate cerebral and
cord perfusion pressure.
> > Careful anticoagulation
monitoring and management.
> > Careful neck positioning, **
especially if there are risk factors that may
already compromise blood supply to cervical cord.
> > Optimal blood glucose management.
> > Possibly avoiding excessive periods
of excessively deep anaesthesia
with the use of depth of anaesthesia monitoring.
> > Monitoring and management of
acid–base balance to avoid deleterious
effects on brain autoregulation.
> > If hypothermia induced,
avoidance of fast rewarming which predisposes
to cerebral oedema.
> > Cerebral regional oximetry monitoring with appropriate management in response to decreases.
Postoperative:
» Avoidance of hypoxia.
> > Management of modifiable cerebrovascular disease risk factors such as blood glucose, blood pressure, cholesterol.
