Congenital Heart Defects

Hemodynamics, Pharmacology, and Updates

Amanda L. Affleck CRNA, MAEProvidence Anesthesia Services

Five Basic QuestionsIs 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?

Acyanotic vs CyanoticACYANOTIC

Left-to-right shuntOxygenated blood mixes with venous returnImpediment to systemic perfusion

CYANOTICRight-to-left shuntVenous blood mixes with systemic flow, as well as less blood going to the lungs for oxygenation.Impediment to pulmonary perfusion.

Acyanotic Defects

OBSTRUCTIONOn the left side decreases systemic

flow=hypoperfusion

SHUNTLeft-to-rightPulmonary over-circulation may lead to pulm htn,

and eventually pulmonary vascular obstructive disease (Eisenmenger’s Syndrome)

Acyanotic DefectsVentricular Septal DefectAtrial Septal DefectPersistent Ductus ArteriosusAortic StenosisCoarctation of the AortaComplete Common Atrioventricular Canal

Acyanotic DefectsWhat increases left-to-right

shunt?

Dramatic increase in SVR relative to PVR.

Dramatic decrease in PVR relative to SVR.

Cyanotic DefectsOBSTRUCTION

On the right side, decreases pulmonary flow=hypoxemia

SHUNTRight-to-leftLess blood reaches the lungs for

oxygenationVenous blood mixes with systemic

flow

Cyanotic DefectsPulmonary StenosisTetralogy of FallotTransposition of the Great ArteriesTricuspid AtresiaPulmonary Atresia

Atresia: absence or closure of a natural passage of the body

Cyanotic DefectsWhat increases right-to-left

shunt?Decrease in SVR.

Increase in PVR.

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.

PVR & SVRSVR nml values and definition SVR Inhalational agents H2 release

Ganglionic blockade SVR RX

PVR & SVRPVRNormal 90-250 dynes/s/cm-5

PVR Hypoxemia Acidosis N2O

PainRX

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.

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.

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.

Anesthetic Considerations for Acyanotic Defects

Induction:Potent intravenous and inhalational agents will decrease

SVR.

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.

Anesthetic Considerations for Acyanotic Defects

IntraOp:Positive pressure ventilation and Valsalva maneuvers may cause transient reversal of flow in left-to-right shunts.

Anesthetic Considerations for Acyanotic Defects

PostOp:Drugs to decrease pulmonary htn:

Inhaled nitric oxide, prostacyclin, prostaglandin I2, prostaglandin E2

Phosphodiesterase inhibitorsNTG, Nitroprusside

Pain control: Pain causes increased sympathetic stimulation=inc PVR, but oversedation causes hypercapnia=inc PVR.

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.

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.

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 DRUGSTheoretically, 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

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.

Anesthetic Considerations for Cyanotic Defects

IntraOp:Maintain SVRA 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.

Anesthetic Considerations for Cyanotic Defects

IntraOp:EtCO2 significantly 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.

Anesthetic Considerations for Cyanotic Defects

PostOp:Adequate analgesia without sedation-induced hypercapnia.

Pain yields sympathetic stimulations which PVR.

Over-sedation yields hypercapnia which PVR.

Right Ventricular Failure

&

Pulmonary Arterial Hypertension

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.

endothelial cells

smooth muscle cells

Nitric oxideProstacyclin

vasodilate

Thromboxane A2Endothelin-1

vasoconstri

ct

Pulmonary Hypertension

mPAP greater than 25 mmHg

PVR greater than 240 dynes/cm/-5

WHO Classification of Pulmonary Hypertension

I. Pulmonary arterial hypertension (ex. familial, congenital left-to-right shunt)

II. Pulmonary venous hypertension (ex. left-sided valvular heart disease)III. PH with disorders of the respiratory system

(ex. COPD)IV. PH d/t chronic embolic disease (ex. PE)V. PH d/t disorders affecting pulmonary vasculature directly (ex. sarcoidosis)

Intraoperative causes of PH

Hypoxia, hypercarbia, acidosisEmbolism (thrombus, CO2, air)Bone cementProtamineCardiopulmonary bypassIschemia-reperfusion syndrome (clamping, declamping of aorta)Loss of lung vessels (pneumonectomy)

Right VentricleThin-walled, highly compliant, but poorly contractile chamber.

Under normal conditions ejects blood against 25% of the afterload, compared to the LV.

*

*RV failure

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.

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.

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

Anesthetic Management

Anesthetic ManagementPreOp:Maintain any current pulmonary vasodilator therapy to avoid rebound pulmonary hypertension.

Careful sedation to avoid respiratory acidosis and subsequent in PVR.

Anesthetic ManagementSpinal 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.

Anesthetic ManagementArterial line

Central venous pressure monitoring of fluid trends

Trans esophageal echo

Induction AgentsFentanyl, 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.

MaintenanceReduce PVR

Avoid metabolic acidosisAdequate analgesia & anesthesia

to avoid catecholamine surgeAvoid shivering

Maintenance

Maintain RV functionAvoid hypovolemia or fluid overload

(RV is less pre-load responsive compared to LV)

Appropriate fluid challenge is 250-500ml

Ventilatory StrategiesAvoid HPV with high FiO2Moderate hyperventilation (PaCO2

30-35)PEEP <15cmH2O (compression of

alveolar vessels RV afterload)Avoid high airway pressures which compress pulmonary vasculature.No Nitrous!!!

Pharmacologic SupportMaintain SVR to support coronary perfusion

NorepinephrinePhenylephrine (’s PVR)

Inotropic support of RV functionMilrinone, Dobutamine: support

RV function and PVR**vasopressor support may

be needed as it will SVR)

Pharmacologic SupportInhaled Nitric Oxide

Potent and specific pulmonary vasodilator

Immediately inactivated in the circulation by

hemoglobin binding.Sildenafil

’s PVROnly available orally

Post Op

Factors that increase PVRHypoxemiaAcidosisHypercapniaHypothermiaIncreased sympathetic stimulation