Case 63 - Congenital Heart Disease Flashcards
What are general anesthetic considerations for common congenital cardiac lesions?
1) Exctracardiac defects
- patients with congenital heart disease (CHD) may also have other congenital anomalies like GU tract
- associated with chromosal anomalies like Down’s (trisomy 21)
2) prevention of air embolism
- all CHD pts are at risk for air emboli into systemic circulation
- shunts are bi-directional
- air embolism can obstruct RVOT and caue a L-R shunt to change into a R-L shunt.
3) Endocarditis prophylaxis
- dental procedures and procedures involving respiratory tract, skin structures, or musculoskeletal tissues that are infected
- not needed for GI or GU or flexible bronch procedures
What are some precautions you can take to prevent air embolism in a patient with CHD?
- CHD patients have shunts that are often bi-directional
- 1) LV has earlier relaxation than RV –> temporary reverse of L-R shunt
- 2) air in RVOT can reverse shunt due to acute increase in RV pressure
- Goal = avoid air embolism to enter systemic circulation
Precautions
- debubble all IV tubing
- all IV lines connected while free flowing
- all syringes clear of air
- air filters on tubing
Which patients with congenital heart disease require endocarditis prophylaxis?
1) patients with unrepaired CHD (including palliative shunts and conduits)
2) repaired CHD with proesthetic material or device w/i 6 months of surgery
3) repaired CHD with residual defect at site
What is an atrial septal defect?
- Left to Right Shunting
- ASD involves a patent foramen ovale
- LA to RA shunting
- can go asymptomatic, eventually increase blood flow to right side of heart –> pulm HTN and RV volume overload –> reversal of shunt (eisenmengers synd)
Anesthethic concern –> prevent systemic embolization of air
What is a ventricular septal defect?
- Left to right shunting
- flow depends on ratio of PVR to SVR
- if PVR is high and matches SVR –> no shunting occurs
- if PVR is higher than SVR –> R to left shunting
- If PVR is less than SVR –> L to Right shunting
- Problem is 3 fold
- left to right shunting promotes more blood returning to left side of heart –> Left heart CHF 2/2 to volume overload of LV
- large L to R shunting promotes more blood to enter right side of heart than systemic circulation (path of least resistence) = systemic underperfusion and CV collapse
- L to R shunt promotes increase pulmonary blood flow –> increase in PVR –> reversal of shunt
What is patent ductus arteriosus?
- Left to right shunt
- Aorta shunts blood to pulmonary artery
- meds to close shunt = prostaglandin inhibitors (indomethacin)
- surgical closure if indicated
What are anesthetic considerations for L to R shunting lesions?
1) Airway Management
- intubation and mech ventilation
- infants have chronicially congested lungs due to increase pulm blood flow from L to R shunting
2) Prevent paradoxical air embolism
- debubble all IV tubing
- Air filters
- med syringes with no air
3) Maintain relatively high PVR
- infants with large PVR have chronically congested lungs due to inc pulm blood flow assoc with shunting
-
high PVR to minimize further pulm congestion
- least FiO2 necesary for adequate saturation
- normocarbia or mild hypercarbia
- Recall - inc O2, alkalosis, hypocarbia = pulm vasodilation
4) prevent significant decrease in SVR
- If SVR < PVR, then reversal of shunt –>hypoxic blood into systemic circualtion
- low dose inhaled anes + opioid + ketamine
5) anes induction
- inhalation induction not affected by L to R shunt
- IV induction delayed –> more drug returns to lung
6) endocarditis prophylaxis
- first 6 months after CHD repair
- repair but residual defect
What is tetraology of Fallot?
- VSD, RVH, pulmonary valve stenosis, overriding aorta
- Right to Left Shunting
- symptoms may improve by keeping ductus arterosius open prior to surgical correction (prostaglandin E1).
in TOF, what are hypercyanotic (aka tet) spells and what are goals of tx for tet spells?
- episodes of further increase in right to left shunting
-
caused by severe infundibular spasm
-
induced by decrease venous return
- decrease pulm blood flow = less blood to be oxygenated
- decrease LV filling pressure –> promotes more R to L shunting
-
decrease SVR
- decreases LV pressure, promotes more R to L shunting
-
induced by decrease venous return
Treatment
-
decrease indundibular spasm
- decrease contracility, HR
- increase preload
- increase SVR
How will you prevent tet spells, how will you tx tet spells if it occurs?
Prevention
- beta-adrenergic blockade
- relaxes cardiac muscle = prevents infundibular spasm
- avoid hypovolemia
- avoid SVR reduction
- maintain adequate anesthsetic depth to prevent infundibular spasm
Tx:
- 1) decrease contracility and HR
- Esmolol
- 2) increase preload
- fluid bolus
- 3) increase SVR
- phenylephrine bolus and infusion
What are anesthetic considerations for right to left shunting lesions with reduced pulmonary blood flow?
1) Prevent paradoxical air embolism
- debubble all IV lines
- air filters on IV tubing
- avoid admin medication with air in syringes
2) avoid dehydration
- results in decrease preload (decrease LV filling pressure) –> promotes further shunting
- clear liquids until 2 hrs prior to sx
- IV fluid
3) cardiac
- maintain SVR (dec R to L shunting)
- avoid bradycardia
- CaO2 low 2/2 hypoxemia. To maintain Do2, need to maintain CO (SV x HR)
4) Pulmonary
- cyanotic and hypoxic patients (R to L shunting)
- pts with dec pulm blood flow will have V/Q mismatch (dead space ventilation)
- increase PaCo2 and ETCO2 gradient (since not all of blood undergoes gas exchange in lungs)
- moderate degree of hyperventilation necessary to maintain normocarbia
5) Induction
- prolonged with poorly soluble inhalation anes (sevo, des, N2O)
- b/c dilution from gas exchanged and non-gas exchanged blood –> overall concentration in blood is very low –> very little gets to brain
- accelerated with IV agents (bypass lungs)
