Author: Michael Vlessides
A significant contributor to morbidity and mortality, pulmonary hypertension is associated with diverse cardiac, pulmonary and systemic diseases among neonates, infants and older children. Yet some experts say the significant risk presented by these patients can be mitigated by adaptability and vigilance on the part of the anesthesiologists who treat them.
|Table. Risk Stratification of Patients With PH Presenting For Noncardiac Surgery|
|Patient Factors||Higher Risk Category|
|Echocardiography||Systemic or suprasystemic PAP; RV enlargement or dysfunction|
|Cardiac catheterization data||PVRI elevated; RAP >10 mm Hg; CI <2.0 L/min/m2|
|Functional capacity||Fatigues easily; FTT; increased school absence; WHO class III and IV|
|PH therapy||Escalating therapies; supplemental oxygen|
|Etiology||Idiopathic and hereditary|
|Comorbidities||Limited cardiopulmonary reserve|
|Procedural Factors||Higher Risk Category|
|Type of surgery||Major thoracoabdominal surgery and cardiac catheterization|
|BNP, brain natriuretic peptide; CI, cardiac index; FTT, failure to thrive; PAP, pulmonary artery pressure; PH, pulmonary hypertension; PVRI, pulmonary vascular resistance index; RAP, right atrial pressure; RV, right ventricle; WHO, World Health Organization|
Most recently, a 2018 study by Meghan Bernier, MD, an assistant professor of anesthesiology at the Johns Hopkins University School of Medicine, in Baltimore, Dr. Unegbu and their colleagues (Pulm Circ 2018;8:2045893217738143) examined perioperative events in children with pulmonary hypertension undergoing noncardiac procedures. The retrospective cohort study comprised 77 children with active or pharmacologically controlled pulmonary hypertension who underwent cardiac catheterization or noncardiac surgery between 2006 and 2014.
Of note, the study found that preoperative inhaled nitric oxide (odds ratio [OR], 0.32; P=0.046) and prostacyclin analog therapies (OR, 0.24; P=0.008) were both associated with decreased incidence of minor events, but not major events.
This relationship between pulmonary vasodilation and outcomes in pediatric pulmonary hypertension also was explored in a 2015 study (Anesth Analg 2015;120:420-426). In assessing the impact of targeted therapies for pulmonary hypertension on pediatric intraoperative morbidity or mortality, the researchers reviewed the records of 122 children who underwent 284 non–cardiopulmonary bypass procedures between 2008 and 2012.
The study found that the use of disease-modifying agents was not associated with significantly reduced complications: 4.1% in treated and 8.6% in untreated patients (P>0.14). “There was a trend toward significance,” Dr. Unegbu explained, “so if more patients were included, the pulmonary vasodilators may have been found to have a protective effect.”
Luckily, other therapeutic approaches may prove successful in treating children with pulmonary hypertension. “In general, patients with pulmonary hypertension or pulmonary vascular disease are felt to have an imbalance between their vasodilatory and vasoconstrictor pathways,” Dr. Unegbu said. “They have a relative deficiency of vasodilator pathways, and an abundance of pulmonary vasoconstrictors.”
Medications used to manage pediatric pulmonary hypertension aim to dilate the pulmonary vasculature via either the nitric oxide, endothelin or prostacyclin pathways. Inhaled nitric oxide is the most commonly used agent during pulmonary hypertensive crises. Patients who respond to nitric oxide often are transitioned to sildenafil, which also helps to inhibit the degradation of cyclic guanosine monophosphate.
“Prostacyclin analogs are other drugs we may use here,” said Dr. Unegbu, whose presentation was at the 2018 annual meeting of the Society for Pediatric Anesthesia. “These can be administered by a number of routes. Specifically, epoprostenol and treprostinil can be administered subcutaneously, intravenously or inhaled.” Endothelin receptor antagonists are typically used for chronic therapy, not in the presence of an acute crisis.
With respect to diagnosing children with pulmonary hypertension, cardiac catheterization offers an unparalleled level of diagnostic capabilities, including critical information about the pulmonary veins. “Pulmonary vein stenosis is a silent saboteur, and can be very difficult to look at with transthoracic echocardiography,” Dr. Unegbu said.
Recent guidelines state that cardiac catheterization should be performed in these patients before the initiation of pulmonary vasodilator therapy. “I would say that almost never happens,” Dr. Unegbu said. “These patients are usually so sick that we tend to throw everything at them, allow them to cool off, and then do a catheterization.
“The problem with this strategy is that if the patient has pulmonary vein stenosis and you administer aggressive vasodilators, you can put them into pulmonary edema.”
When it comes to performing surgery in pediatric patients with pulmonary hypertension, Dr. Unegbu strongly recommended a very conservative approach. “Do not do elective cases in these high-risk patients,” she said. “It’s not worth it and you will often regret it.”
- Ensure access to advanced therapies such as extracorporeal membrane oxygenation.
- Advocate for early scheduling to ensure maximum resource availability.
- Minimize nil per os (or, nothing by mouth) time.
- Use experienced anesthesiologists and surgeons who can ensure the shortest surgical time possible.
“Finally,” she added, “if they’re presenting with an upper respiratory illness as an outpatient, that is cause for an immediate cancellation. These patients do very poorly.”
Successful Induction Is Key
Proper anesthetic management also plays a vital role in ensuring surgical success in these patients. This is particularly true during induction, which Dr. Unegbu said represents the greatest anesthetic risk to children with pulmonary hypertension. “We really need to do a balanced induction and not use too much of a single anesthetic agent,” she said.
“When you’re ventilating these patients, be careful not to overventilate and overdistend,” she continued. “Also, increasing their intrathoracic pressure compromises preload and venous return to the right ventricle, which is very sensitive. And do everything you can to minimize their pulmonary vascular resistance.”
As Dr. Unegbu concluded, many gaps remain in our current knowledge of the unique features of pulmonary hypertension in children. With continuing research and adherence by clinicians to optimal clinical evaluations and treatment strategies, improving the quality of life and long-term outcomes of these individuals is a realizable objective.