Clinical types of neural damage

• Neurological deficits secondary to air embolism are usually transient and resolve completely at a variable rate post operatively

• Embolization of particulate matter is usually more devastating with resolution [if it occurs] occurring over a prolonged time

a) Severe CNS Damage [stroke]

• Stroke is the major cause of severe neurological disability after cardiac surgery
• Severe brain injury leading to death or frank stroke (eg hemiparesis or aphasia) occurs in relatively few patients (≤ 5%)
• Stroke:“a focal CNS deficit of relatively sudden onset that lasts more than 24 hours
• Incidence of stroke:

1. Closed Chamber procedure:1 — 2%

2. Open Chamber: 3—5 %

• 70% of strokes occur intraoperatively; 30% occur in early postoperative period
• Using MRI: 30% of CABG patients showed significant new changes 8 days post op
• A proportion of stroke patients die in hospital due to persistent coma or multiorgan dysfunction with inability to be weaned from the ventilator

b) Subtle CNS damage

• Includes visual field changes, subtle motor-sensory limitations due to CNS injury 2° exposure to CPB
• In up to 50% of all patients early post CPB period
• Incidence may be independent of surgey type
• By 2 months post op, incidence decreases to 20% and persists for at least a year

• The major recovery after CPB related brain damage occurs in the first few months

§ CABG: a significant proportion of neuropsychological deficits observed shortly after surgery persist [78% had deficits 1 week post; 29% had deficits 1 year post]

• Valvular: 27% had deficits 2 months post, mitral valve surgery have poorest outcome
• Neuropsychological deficits: some resolve with time, but a high proportion persist to disable patients by impairing memory, concentration, hand-eye co-ordination with a negative impact on lifestyle

c) Cognitive dysfunction

• Symptoms of intellectual impairment eg concentration, retention, processing of new information
• Up to 80% in 1st week post CABG
• 35% still show some degree of cognitive dysfunction at 2-month & 12-months

d) Peripheral Nerve Injury

• Peripheral nerve injury of the upper extremity occurs in 6% of patients undergoing medial sternotomy due to stretching of brachial plexus with sternal retraction
• Other nerves injured after cardiac surgery include: phrenic, ulnar, radial, saphenous, facial.
• More than 90% of symptoms associated with peripheral nerve injury of upper extremity resolve within 3 months