Neurological Complications after Coronary Artery Bypass Surgery

Question 1

What are the central neurological complications of coronary artery bypass surgery

Answer 1

Postoperative cognitive dysfunction (both short and long term)

Stroke (ischaemic, embolic or haemorrhagic) can be as a result of existing thrombus vessel legions or cardiopulmonary bypass

TIA

Gas Emboli

Ischaemic Spinal Cord Injury

Delirium

Question 2

What are the peripheral neurological complications of coronary artery bypass surgery

Answer 2

Brachial plexus injury
( from central line insertion, patient positioning, sternal retraction [rotation of the 1st rib pushes the clavicles into retro clavicular space putting traction on the plexus] and internal mammary artery harvesting [as wider retraction needed])

Ulnar nerve injury
(from positioning associated with radial artery harvesting)

Phrenic Nerve Injury
(the left phrenic nerve passes between the lung and the mediastinal pleura so is at greater risk with internal mammary artery harvesting)

Recurrent Laryngeal Nerve Injury
(from intubation which can be prolonged and with periods of hypotension or during surgical dissection especially during dissection of the internal mammary artery)

Saphenous Nerve Injury
(occurring during saphenous vein harvesting due to it’s close proximity to the nerve at the ankle)

Intercostal Nerve Damage
(During minimally invasive direct coronary artery bypass as the incision is between the ribs rather than a sternotomy)

Question 3

What patient risk factors are there for the development of central neurological complications due to coronary artery bypass surgery

Answer 3

Age
Hypertension
Hypercholesterolemia
History of Stroke
Diabetes Mellitus
Carotid Stenosis
Preoperative cognitive dysfunction (including Alzheimer’s , Parkinson’s and Cerebral Vascular Disease)
History of Substance or Alcohol misuse
Poor Left Ventricular Function

Question 4

What surgical risk factors are there for the development of central neurological complications after coronary artery bypass surgery

Answer 4

Duration of surgery
(potentially multifactorial, relating to the stress response to surgery, disruption of the blood brain barrier and altered autoregulation)

Micro emboli from a diseased aorta when clamped, cannulated or handled

Micro emboli from the cardiopulmonary bypass circuit

Rapid Rewarming after hypothermia can cause a loss of autoregulation resulting in cerebral oedema

Failure to maintain adequate cerebral perfusion pressure during Cardiopulmonary bipass

Question 5

What anaesthetic risk factors are there for the development of central neurological complications after coronary artery bypass surgery

Answer 5

Prolonged deep hypnotic time

Low Intraoperative mean arterial pressure and hence cerebral perfusion pressure

Question 6

What intraoperative approaches are there to minimise the risk of central neurological complications after coronary artery bypass surgery

Answer 6

Minimally invasive techniques
(which reduce the stress response)

Adequate priming of the cardiopulmonary bypass circuit (if used) and use of bubble traps and embolus filters

Surgical care to avoid disrupting aortic plaques on clamping and cannulation, e.g. the use of ultrasound to check vessels before canulation

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 is induced to avoid fast rewarming which predisposes to cerebral oedema

Cerebral regional oximetry monitoring with appropriate management in response to decreases