1. Peri-operative Management of Pulmonary Hypertension
DR SP MACHAWIRA
University of Wits

2. Introduction
Pulmonary hypertension complicates 2% of patients undergoing congenital cardiac surgery(Adatia I et al 2009)
In India 60% of post operative deaths due to PHT crises(Choudhary SK et al Ann Thorac Surg 1999)
The functional and structural status of the pulmonary bed important
Immediate post-operative period the most vulnerable time
Pulmonary endothelium dysfunction the most important factor but pathophysiology incompletely understood

3. Introduction
The outcome of patients has improved due to better understanding of peri-operative management
PHT is an independent risk factor in morbidity and mortality in patients undergoing congenital cardiac surgery
Pulmonary hypertensive crisis is the extreme end and a feared complication associated with increased morbidity and mortality

4. Hypertensive Pulmonary Crisis
Complicates 0.75% of congenital cardiac surgery and has a mortality of 20%
Pathophysiology incompletely understood and complex
Increased post operative vasoreactivity to sympathetic stimuli
Vasospastic stimuli result in sudden increase of pulmonary artery pressure and resistance
Right heart failure with TR
Systemic hypotension and MI
Increased airway resistance

5. Management Complex and unpredictable Prevention is the best
Identifying patients at risk
Pre-operative care
Intra-operative care
Post-operative care

6. General
Early surgery prevents the development of pulmonary vascular obstructive disease
Sedation with fentanyl and paralysis first 24 hours
Prevent acidosis: pH and not pCO2 increases pulmonary vascular resistance
Correct hypothermia
Maintain adequate oxygenation but avoid baro and volutrauma
Correct polycythaemia to reduce PVR

7. Patients At Risk
Difficult to predict influenced by age, lesion & pre-existing endothelial cell dysfuction
Usually affects patients with reactive pulmonary vascular beds
Patients with pulmonary venous hypertension(TAPVC) have extremely reactive beds
Extra-cardiac syndromes eg Trisomy 21, omphalocele

8. Patients at risk
PA arising from the aorta, Truncus arteriosus, AP window
Single ventricle physiology with unrestricted pulmonary blood flow
mPAP >25mmHg or 50-60% of systemic on coming off bypass with signs of low cardiac output
Patients with residual lesions

9. Pre-operative Care Severe CCF needs significant resuscitation
Intubation and ventilation may be necessary to correct metabolic derangements
Control and treat sepsis
Avoid hypotension at induction may cause cardiac ischaemia
Need to maintain Qp:Qs at 1:1 to ensure adequate organ perfusion as pulmonary overcirculation implies systemic hypoperfusion
Hypercapnia and low FiO2 increase PVR to ensure adequate systemic blood flow
Research on pre-op iNO, sildenafil and endothelin inhibitors

10. Intra-operative Strategies
Smaller tidal volumes once sternum open
Cardiopulmonary bypass, hypothermia and circulatory arrest enhances pulmonary vaso-reactivity
Complete repair where possible
PFO may be a life saving procedure allowing for pop-off valve
Use of PAP lines debatable increased risk of bleeding, overreacting to changes, considered mandatory in research on new drugs

11. Effect of Bypass on Haemodynamicc

12. Post-operative ICU care plays a critical role in the patient outcome
Anticipate and treat PHT crises aggressively
Sedation with Fentanyl and paralysis in the first 24 hours especially when suctioning to avoid pain and anxiety
Adequate oxygenation without barotrauma or hyperoxygenation
Avoid hypercapnia however pH control more important
pH> 7.4 or pH>7.5 when patient has had a crisis:
HCO3 and hyperventilation may be necessary

13. III. INOTROPIC SUPPORT IN THE PERI-OP PERIOD
Effect of pH and CO2 on PVR

14. Post-operative Strategies
Use of inodilators eg milrinone, dobutamine, low dose adrenaline with nitroglycerin
Specific pulmonary vasodilators iNO, prostacyclin, sildenafil
Investigate surgical accuracy ie residual lesions
ECMO
RVAD

16. Inhaled Nitric Oxide
Nitric oxide produced by endothelial cell final pathway to vasodilation
Accepted mode of treatment for post-operative pulmonary hypertension
Easy to administer, minimal side effects and specific for pulmonary vascular bed
Dose 2-80ppm, however no clinical benefits of doses>10-20ppm
Rebound PHT wean slowly from 5ppm at 0.5ppm/2hours- prolongs ventilation
Side effect methaemoglobinaemia(>5%) negligible

17. iNO vs Placebo on PVRI

18. Sildenafil Type 5 phosphodiesterase inhibitor
Can be used to assist with weaning off iNO hence earlier extubation
At doses of mg/kg/6hourly can be used to prevent rebound PHT on weaning iNO
Can be used in conjuction with iNO, and inhaled Illoprost in patients who are in refractory PHT
May be useful in transition to chronic therapy

19. Illoprost
Prostacyclin analogue, inhibits thrombocyte aggregation and brings about vasodilation
Can be inhaled or intravenous
Inhaled has half life 30 minutes
No toxic effects
Effect comparable to iNO
Can be used in PHT resistant iNO
Can be used intermittently thus allows for weaning off from ventilation

20. Other Strategies
ECMO used much less often due to general improvement in peri-operative care
RVAD
Prophylactic therapy citrulline, sildenafil and endothelin receptor inhibitors
Combination therapy in refractory cases