Congenital Heart Defects

1. Congenital Heart Defects Hemodynamics, Pharmacology, and Updates Amanda L. Affleck CRNA, MAE Providence Anesthesia Services

3. Five Basic Questions • Is the patient acyanotic or cyanotic? • Is pulmonary arterial blood flow increased or not? • Does the malformation originate in the left or right side of the heart? • Which is the dominant ventricle? • Is pulmonary hypertension present or not?

4. Acyanotic vs Cyanotic ACYANOTIC Left-to-right shunt Oxygenated blood mixes with venous return Impediment to systemic perfusion CYANOTIC Right-to-left shunt Venous blood mixes with systemic flow, as well as less blood going to the lungs for oxygenation. Impediment to pulmonary perfusion.

6. Acyanotic Defects OBSTRUCTION On the left side decreases systemic flow=hypoperfusion SHUNT Left-to-right Pulmonary over-circulation may lead to pulmhtn, and eventually pulmonary vascular obstructive disease (Eisenmenger’s Syndrome)

7. Acyanotic Defects Ventricular Septal Defect Atrial Septal Defect Persistent Ductus Arteriosus Aortic Stenosis Coarctation of the Aorta Complete Common Atrioventricular Canal

8. Acyanotic Defects What increases left-to-right shunt? Dramatic increase in SVR relative to PVR. Dramatic decrease in PVR relative to SVR.

9. Cyanotic Defects OBSTRUCTION On the right side, decreases pulmonary flow=hypoxemia SHUNT Right-to-left Less blood reaches the lungs for oxygenation Venous blood mixes with systemic flow

10. Cyanotic Defects Pulmonary Stenosis Tetralogy of Fallot Transposition of the Great Arteries Tricuspid Atresia Pulmonary Atresia Atresia: absence or closure of a natural passage of the body

11. Cyanotic Defects What increases right-to-left shunt? Decrease in SVR. Increase in PVR.

12. How do I know where the blood will go? PVR:SVR will determine the direction of shunt. Blood takes the path of least resistance, therefore these pressures are manipulated in order to maintain the patient’s oxygenation & cardiac output.

13. PVR & SVR SVRnml values and definition • SVR Inhalational agents H2 release Ganglionic blockade SVR RX

14. PVR & SVR PVR Normal 90-250 dynes/s/cm-5 • PVR Hypoxemia Acidosis N2O Pain RX

16. Anesthetic Considerations for Acyanotic Defects GOAL:Decrease shunt & maintain adequate oxygenation and perfusion PreOp:How big is the shunt? (echo) What palliative or corrective work has been done? Do you understand the plumbing? Baseline cardiorespiratory status. Functional status, exercise tolerance. Baseline VS, including RA SpO2. De-bubble and filter IV lines.

17. Anesthetic Considerations for Acyanotic Defects SBE prophylaxis? Recommended in shunts with cyanotic disease or patients with surgical or percutaneous procedure in the last 6 months. Otherwise endocarditis prophylaxis is not recommended for simple non- cyanotic lesions.

18. Anesthetic Considerations for Acyanotic Defects Induction: An inhalation induction is generally tolerable, if necessary (i.e., peds). Patients with severe pulmonary htn or RV failure should have an IV induction. Theoretically, left-to-right shunt may speed inhalation induction by decreasing the aterial-venous gradient of agent in the lungs.

19. Anesthetic Considerations for Acyanotic Defects Induction: Potent intravenous and inhalational agents will decrease SVR.

20. Anesthetic Considerations for Acyanotic Defects IntraOp: Avoid acute & long-term increases in SVR or decreases in PVR (worsens the left-to-right shunt). High O2 concentrations decrease PVR and increase SVR. Hypoxemia increases PVR & decreases SVR. Acidosis increases PVR. IV bolus meperidine may increase PA pressures.

21. Anesthetic Considerations for Acyanotic Defects IntraOp: Positive pressure ventilation and Valsalva maneuvers may cause transient reversal of flow in left-to-right shunts.

22. Anesthetic Considerations for Acyanotic Defects PostOp: Drugs to decrease pulmonary htn: Inhaled nitric oxide, prostacyclin, prostaglandin I2, prostaglandin E2 Phosphodiesterase inhibitors NTG, Nitroprusside Pain control: Pain causes increased sympathetic stimulation=inc PVR, but oversedation causes hypercapnia=inc PVR.

24. Anesthetic Considerations for Cyanotic Defects GOAL:Decrease shunt & maintain adequate perfusion & oxygenation. PreOp: How big is the shunt? (echo) What palliative or corrective work has been done? Do you understand the plumbing? Baseline cardiorespiratory status. Functional status, exercise tolerance. Baseline VS, including RA SpO2. De-bubble and filter IV lines!!! A bubble can easily pass through a right-to-left shunt to the systemic circulation to the brain or another end organ.

25. Anesthetic Considerations for Cyanotic Defects PreOp: Avoid preoperative dehydration (esp. with ToF, polycythemia, & Fontan physiology). Dehydration combined with polycythemia may cause stroke. Preop admission for overnight hydration may be necessary.

26. Anesthetic Considerations for Cyanotic Defects Induction: Maintain SVR>PVR to reduce right-to-left shunt. An inhalation induction is generally tolerable. Ketamine may maintain SVR. OTHER INDUCTION DRUGS Theoretically, right-to-left shunt may dilute the inhaled anesthetic agent in the LV, decreasing the amount of IA reaching the brain, slowing induction. CHECK THIS IV AND IA OR IA ONLY

27. Anesthetic Considerations for Cyanotic Defects Induction: By decreasing SVR IA’s may increase shunt and cyanosis, so titrate agents up slowly. A fall in SpO2 may actually reflect a fall in SVR, as more blood shunts right-to-left Desaturation not readily attributable to respiratory difficulty is likely d/t SVR with right-to-left shunt, & should be treated with a direct vasoconstrictor.

28. Anesthetic Considerations for Cyanotic Defects IntraOp: Maintain SVR A decrease in SVR and/or an increase in PVR worsens shunt and hypoxia. Avoid excessive positive airway pressure and excessive PEEP in patients with decreased pulmonary flow (ToF, pulmonary stenosis), as they will further decrease flow.

29. Anesthetic Considerations for Cyanotic Defects IntraOp: EtCO2significantly underestimates PaCO2. Increases in physiologic dead space (ventilation without perfusion) Increases in venous admixture (right-to-left shunt) As right-to-left shunt increases, etCO2 is less accurate.

30. Anesthetic Considerations for Cyanotic Defects PostOp: Adequate analgesia without sedation-induced hypercapnia. Pain yields sympathetic stimulations which PVR. Over-sedation yields hypercapnia which PVR.

31. Right Ventricular Failure & Pulmonary Arterial Hypertension

32. Pulmonary Vascular Bed A high flow, low pressure system Tone is maintained via balanced production by the pulmonary endothelium of vasodilators (prostacyclin, nitric oxide) & vasoconstrictors (endothelin-1, thromboxane A2, serotonin) which act on the smooth muscle cells.

33. endothelial cells Endothelin-1 Prostacyclin Nitric oxide Thromboxane A2 vasodilate vasoconstrict smooth muscle cells

34. Pulmonary Hypertension mPAP greater than 25 mmHg PVR greater than 240 dynes/cm/-5

35. WHO Classification of Pulmonary Hypertension Pulmonary arterial hypertension (ex. familial, congenital left-to-right shunt) II. Pulmonary venous hypertension (ex. left-sided valvular heart disease) PH with disorders of the respiratory system (ex. COPD) PH d/t chronic embolic disease (ex. PE) V. PH d/t disorders affecting pulmonary vasculature directly (ex. sarcoidosis)

36. Intraoperative causes of PH Hypoxia, hypercarbia, acidosis Embolism (thrombus, CO2, air) Bone cement Protamine Cardiopulmonary bypass Ischemia-reperfusion syndrome (clamping, declamping of aorta) Loss of lung vessels (pneumonectomy)

37. Right Ventricle Thin-walled, highly compliant, but poorly contractile chamber. Under normal conditions ejects blood against 25% of the afterload, compared to the LV.

38. * *RV failure

39. RV is bound by the RV free wall and the inter-ventricular septum. Failure of both to contract normally ultimately leads to reduced LV filling and cardiac output.

40. The free wall of the RV is served by the right coronary artery. Perfusion occurs during both systole and diastole. Perfusion pressure depends on the gradient between the aorta and RV pressures. Systemic hypotension or increased RV pressure result in decreased RV coronary perfusion.

41. Thin-walled RV dilates in the face of increased afterload. Septal shift compresses the LV chamber, further compromising systemic output.

42. Anesthetic Management

43. Anesthetic Management PreOp: Maintain any current pulmonary vasodilator therapy to avoid rebound pulmonary hypertension. Careful sedation to avoid respiratory acidosis and subsequent in PVR.

44. Anesthetic Management Spinal anesthesia is not safe d/t the sympathectomy. Epidural anesthesia may be safely used if the level is raised slowly and close attention is paid to volume status and SVR.

45. Anesthetic Management Arterial line Central venous pressure monitoring of fluid trends Trans esophageal echo

46. Induction Agents Fentanyl, Sufentanil, Propofol, Etomidate, and Thiopental have no effect on pulmonary tone. Ketamine may PVR d/t catecholamine effect. However pt’s with RV failure may be catecholamine depeleted. Caution with SVR leading to inadequate RV function.

47. Maintenance Reduce PVR Avoid metabolic acidosis Adequate analgesia & anesthesia to avoid catecholamine surge Avoid shivering

48. Maintenance Maintain RV function Avoid hypovolemiaor fluid overload (RV is less pre-load responsive compared to LV) Appropriate fluid challenge is 250-500ml

49. Ventilatory Strategies Avoid HPV with high FiO2 Moderate hyperventilation (PaCO2 30-35) PEEP <15cmH2O (compression of alveolar vessels  RV afterload) Avoid high airway pressures which compress pulmonary vasculature. No Nitrous!!!

50. Pharmacologic Support Maintain SVR to support coronary perfusion Norepinephrine Phenylephrine (’s PVR) Inotropic support of RV function Milrinone, Dobutamine: support RV function and  PVR **vasopressor support may be needed as it will SVR)