DR SP MACHAWIRAUniversity of Wits

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

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

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

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

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

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

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

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

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

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

Effect of pH and CO2 on PVR

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

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

Type 5 phosphodiesterase inhibitor Can be used to assist with weaning off iNO

hence earlier extubation At doses of 0.3-0.5mg/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

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

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