Primary pulmonary hypertension

6yr old with primary pulmonary hypertension & obstructive sleep apnea is scheduled for a bilateral tonsillectomy and adenoidectomy. She also has idiopathic thrombocytopenia (platelet count of 34K) and oxygen dependence (2L of oxygen via nasal canula). She has normal coagulation studies and her echocardiogram shows moderately diminished RV function with septal flattening. Her most recent catheterization shows suprasystemic pulmonary pressures with mild response to nitric oxide. Her current medications are a Remodulin infusion, bosentan, sildenafil, Primary pulmonary hypertension
a. Definition and Diagnosis
-Defined as mean PAP >􂀀25 mmHg at rest or >30 mmHg during exercise. -Primary pHTN: diagnosis of exclusion, after other causes are ruled out. -Rare condition that mostly affects young women. -The familial form accounts for 6% of cases (autosomal dominant)
b. Pathophysiology:
-Imbalance between production of endogenous vasodilators (ie. NO) and -Increased thromboxane activity and diminished prostacyclin activity -Abnormal endothelial function & procoagulants  hypercoagulable state. -Symptoms: chest pain, dyspnea, syncope. Goals of current therapeutic regimens?
- possibly reverse vascular changes and medial hypertrophy in the lung. 2) Prior to vasodilator therapy, vasoreactivity testing is usually performed - cGMP active agents (inhaled nitric oxide and phosphodiesterase inhibitors). NO causes direct vascular relaxation via a cGMP mediated pathway. Phosphodiesterase inhibitors (such as sildenafil in this case) inhibit - antagonists of endothelin (vasoconstrictor that is elevated in pHTN patients). Dual receptor endothelin antagonists (such as bosentan in this patient) inhibit the endothelin receptors A and B  vasodilation. Selective ETA receptor antagonists are also used. - Prostacyclin analogues are used as continuous IV and subQ infusions. - the abrupt withdrawal of NO  rebound hypertension Preoperative preparation: How can we prepare this patient
preoperatively? Preoperative admission? Platelet transfusion? What are the
Preoperative admission is beneficial to maintain hydration and avoid decreased
cardiac output, particularly in patients who need to remain NPO patient Blood products (RBC and Platelets). The risks and benefits of platelet transfusion
and the platelet count threshold for transfusion should be discussed with the 1) The amount of histamine from leukocytes in stored platelet concentrates 2) Serotonin stored in granules in platelets is released during platelet storage. 3) Histamine and serotonin release  profound hypotension, wheezing, bronchospasm, pulmonary vasoconstriction  acute RV failure. In this case, the surgeon felt at ease to proceed with platelets on standby. Antifibrinolytic therapy can stabilize clot formation. Several case reviews support
that aminocaproic acid reduces transfusions and bleeding in thrombocytopenic patients, however, randomized controlled studies are lacking. Hematology consult recommended using aminocaproic acid pre- and 3. Intraoperative Management

a. Induction: What are the goals of the induction of anesthesia for this case?
What medications would be most useful to achieve these goals? 1) avoid increases in PVR (by preventing hypoxia, hypercarbia, acidosis, 2) maintain cardiac output, preserve RV function with adequate 3) Prevent decreases in SVR which may adversely affect coronary perfusion, particularly in the presence of poor RV function (vasopressin) 4) avoid increases in sympathetic tone (Remifentanil gtt during intubation) -Etomidate is an ideal agent for induction but other medications are also safe. -Muscle relaxation prevents coughing against ETT, can also use remifentanil -Inhaled agents ↓ SVR, use cautiously – mask induction can be dangerous - case by case assessment (ie. difficult awake IV access, inconsolable pHTN
b. Monitoring
-Standard ASA monitors + arterial line given the potential risk for bleeding. -TEE would be beneficial in the event of hemodynamic instability. Airway Management
-Spontaneous vs controlled positive pressure ventilation: affects on preload -Emergence from anesthesia should aim to prevent increases in PVR. -Role for deep extubation - caution hypoventilation  hypercarbia on emergence. - Low dose remifentail infusion (0.05mcg/kg/min)  awake extubation. -PEEP/PPV can ↓ venous return and cause ↓SVR  pHTN crisis
d. Medications:
What vasopressor medications or inotropes are most useful in a patient with PHTN? What rescue therapies are at our disposal? -Hypotension  pulmonary hypertensive crisis -Treat hypotension w/vasoconstrictors like vasopressin or phenylephrine to avoid RV coronary hypoperfusion and paradoxical septal wall motion. -Inovasodilators (ie. dopamine and milrinone) helpful; counter systemic vasodilating effects with vasoconstrictors. -Nitric oxide should be readily available. Inhaled iloprost has been used but short and long term efficacy has not been proven. e. Anesthesia Maintenance:

How should anesthesia be maintained? Medication effects on pHTN? -Maintenance of anesthesia: balance of IV hypnotics, narcotics and volatiles. -Volatile anesthetics blunt hypoxic pulmonary vasoconstriction, ↓ SVR  PHTN -Sympathetic responses to pain can be managed with remifentanil infusions which have short context sensitive half life, quick titratability. -Paralytics can be helpful to prevent bucking against the ETT and subsequent Postoperative Management: Admission? Floor or ICU?
-Admission to the ICU postoperatively is prudent in this case to monitor closely for
References:

Tulloh, R. Etiology, Diagnosis, and Pharmacologic Treatment of Pediatric Pulmonary
Hypertension. Paediatric Drugs; 2009; 11, 2; 115-28. Ivy, D. Diagnosis and Treatment of Severe Pediatric Pulmonary Hypertension. Cardiology in Review 2001 (9): 4: 227-238. Beghetti, M. Bosentan in Pediatric Patients with Pulmonary Arterial Hypertension. Current Vascular Pharmacology, 2009, 7, 225-233. Levy M et al. Add-On Therapy with Subcutaneous Treprostinil for Refractory Pediatric Pulmonary Hypertension. J Pediatr 2011;158:584-8. Hawkins A. Treatment of pediatric pulmonary hypertension. 509 Vascular Health and Risk Management 2009:5 509–524.

Source: http://pubs.societyhq.com/spaannual11/submissions/lunchpblds/cardiac/Cardiac_Sun-Dinavahi-Friesen.pdf