1. Incidence of and Risk Factors for Neurological Complications of Cardiac Bypass Surgery in Children with Congenital Heart Disease
Dr Neeraj Bhangu, Dr John Pappachan, Prof Fenella Kirkham, Dr Katharine Forrest

2. Background
Children requiring surgery with cardio-pulmonary bypass (CPB) for palliation or correction of congenital heart disease (CHD)
80% survival rates into adulthood for those surviving beyond 1 year of age Knowles et al 2012
The decline in mortality is leading to a shift in emphasis towards reducing morbidity
Well recognised that children with CHD often have neurological abnormalities
Aetiology multifactorial Fallon et al 1995

3. Aetiology of Neurological abnormalities in children with CHD
Pre-Operative – acidosis, hypoxia, pre existing neuro-dev abnormalities, low birth weight, co-morbidities, genetic diagnoses e.g. Di George SyndromeMaharasingam 2003
Intra-Operative - length of CPB, low perfusion pressures, pH management, depth of hypothermia, embolic events, inflammatory response due to blood exposed to bypass circuit
Post-Operative - low perfusion pressures, haemodynamic instability

4. Post CPB Neurological Complications (NC)
Fallon et al 1995 single centre UK study - acute NC in 6% of 523 procedures (411 involved CPB)
Seizures are most common neurological complication
Incidence 4-25%
Usually on day 1-4 post operatively
Choreoathetosis historically common NC post surgery
Risk factors
Prolonged deep hypothermic arrest (rare now)
Duration of bypass
Uneven cooling of the brain related to pCO2 and CBF
?Haematocrit: pre, intra, post operative

5. Background - Haematology
Paediatric
Intraoperative haemotocrit
no difference to 1 year developmental score 25 vs 35% Newburger et al 2008
Adult
Pre and post operative anaemia and low intra operative haematocrit may be associated with
increased risk stroke
increased risk of other morbidities
mortality.

6. Objectives
Case review conducted in an English centre currently providing paediatric cardiac surgery services (1 of 9) was designed to establish the current incidence of and risk factors for post-operative neurological complications (NC).
Case control study to explore the secondary hypothesis that lower intra and post operative haematocrits in patients undergoing CPB lead to increased risk of NCs

7. Methods and Study Design
All children (<16 years) with CHD undergoing CPB (including circulatory arrest) between 01/04/2003–31/03/2015 included.
Patients identified from the electronic procedural database, and discharge summaries reviewed independently by 2 consultant paediatric neurologists, with case note review if information required clarification, and for all with NC.
Cases: data on EEG and cerebral CT/MRI images reviewed
Haematology
Cases
diagnosis, age & gender-matched controls

8. Definition of NC
A NC was defined as an event occuring, regardless of cause, within 30 days of surgery or after 30 days during the same hospitalisation subsequent to the operation.
In this time frame, both intra and post operative complications are included.
This is according to consensus definitions of the Multi-Societal Database Committee for Paediatric and Congenital Heart Disease (6).

9. Neurological complications
Results
1934 CPB operations in 1576 children
44 (2.2%) deaths
Neurological Complications in 94 (4.9%)
CNS Neurological Complications in 32/94
Death
Neurological complications
Odds ratio
95% CI p
95% CI
Bypass time
1.006
1.002, 1.009
.001
1.004
1.002, 1.007
.002
Cross clamp time
0.998, 1010 .2
1.002
0.997, 1.007 .4
Circ arrest time
1.048
1.032, 1.063
1.014
0.996, 1.033 .1

10. Results – Neurological Complications
N (total 94)
Cerebrovascular disorders (AIS, SVT) 11
Chorea 1
Seizures
4 cardio-respiratory arrest
7 with hypocalcaemia (2 Di George)
-Responded to electrolyte correction and/or a single load of anticovulsant medication
-Typically transient 20
Phrenic Nerve Palsy 22
Miscellaneous 40

11. Results - Haematocrit Matched for date of birth, gender and diagnosisNC
Controls p
Intra-operative PCV
0.316+/-0.1
0.350+/-0.02
0.035
Post-operative PCV
0.357+/- 0.07
0.389+/-0.075
0.049

12. Discussion Range of observed NC following CPB may be changing
?Less CNS complications
Previous lit did not include phrenic N. palsy
CNS more long term impact
Low intra & post-operative haematocrit may be associated with acute neurological complications and may be modifiable
Examine pre-operative Hct