Exam 2 Flashcards
List the order of vessels branching off from the Aortic Arch
- Aortic Arch
- Brachiocephalic which becomes the Right Subclavian, then the Right Common Carotid Artery
- Left Common Carotid Artery
- Left Subclavian
What percentage of live births are affected by congenital heart defects
1% (7-10/1000)
2 examples of anatomic shunts
- ASD (atrio-septal defect)
2. VSD (ventriculo-septal defect)
Name and describe the 3 shunts in fetal circulation
- Ductus Venosus - fetal blood vessel connecting the umbilical vin to the IVC, bypassing the liver (~50% of blood)
- Foramen Ovale - allows most of the oxygenated blood entering the right atrium to pass to the left atrium, bypassing pulmonary circulation.
- Ductus Arteriosus - Shunts blood from pulmonary trunk to aorta
In fetal circulation, which ventricle provides systemic blood flow? What type of circulation (parallel or series)?
both ventricles provide systemic blood flow through parallel circulation
Where does oxygenated blood from the placenta return to the fetus?
Umbilical vein
Pvr is ___ and redirects ___ of blood into the ___ aorta via the ductus arteriosus in normal fetal circulation
Pvr is high and redirects 90% of blood into the descending aorta via the ductus arteriosus
What is the O2 Sat of blood entering the ascending aorta from the RA? Blood from the LV?
RA Blood O2 sat is 65-70% and oxygenates the brain and heart in utero. LV blood O2 sat is 55-65% and returns to the placenta.
What type of atmosphere is a growing fetus in?
Relatively cyanotic
What other type of defects are children with CHD usually born with?
Neurological
What changes in the fetal body does a reduction in alveolar PCO2, reduced prostaglandin circulation and increase in alveolar PO2 after cord clamping lead to?
A reduction in PVR which increases pulmonary blood flow and increases LV volume and afterload
When do we expect the ductus arteriosus to close by?
58% by day 2 and 98% by day 4
What causes closure of the ductus venosus?
Portal pressure falling after umbilical vein ligation
What causes functional closure of the foramen ovale?
LA pressure exceeding RA pressure
In what percentage of children <5 years old does a PFO remain anatomically patent? Adults?
Children <5 = 50% (this is why it is very important to eliminate any micro bubbles in IV tubing and syringes)
Adults 25-30%
At what time period do we expect there to be fibrous tissue where the ductus venosus was?
at about 3 months
What is the definition of shunting?
Shunting is when venous return in one circulatory system is recirculated through the arterial outflow of the same system
__ atrial blood shunted to aorta produces recirculation of systemic venous blood, resulting in a __ to __ shunt
Right atrial blood shunted to aorta produces recirculation of systemic venous blood, resulting in a right to left shunt
__ atrial blood shunted to the pulmonary artery produces recirculation of pulmonary venous blood, resulting in a __ to __ shunt
Left atrial blood shunted to the pulmonary artery produces recirculation of pulmonary venous blood, resulting in a left to right shunt
What is a physiologic shunt? Anatomic shunt?
Physiologic shunts are a recirculation of blood, usually as the result of an anatomic shunt.
Anatomic shunt is the communication between cardiac chambers or great vessels
Which type of shunt (large or small) is highly dependent on PVR and SVR
large shunts
3 examples of Acyanotic defects
- PDA
- ASD
- VSD
These recirculate pulmonary venous blood = left to right shunt
5 characteristics of acyanotic defects
- Increased Fatigue (even with things such as normal daily feeding)
- Heart murmurs
- Increased risk of endocarditis
- CHF
- Growth retardation
6 things to avoid with left to right shunts
- Vasodilators
- 100% FiO2
- Decreased PCO2
- Alkalosis
- Increase in SVR
- Decrease in PVR
3 and 4 can decrease PVR, which increasing pulmonary blood flow, increased the left to right shunt
5 physiologic results of left to right shunts
- Decreased systemic perfusion
- Low CO
- Hypotension
- LV failure
- LV volume load
4 physiologic results of right to left shunts
- Decreased pulmonary flow
- Hypoxemia
- LV Volume Load
- LV dysfunction
6 things to avoid in right to left shunts
- Sympathetic stimulation can increase PVR and reduce pulmonary blood flow
- Decreased FiO2
- Increased PCO2
- Acidosis
- Decrease in SVR
- Decrease in PVR
Name 5 cyanotic heart defects
- Tetralogy
- Transposition
- Truncus Arteriosus
- Total Anomalous pulmonary venous return
- Hypoplastic left heart syndrome
2 clinical findings associated with severe, long-standing cyanosis
- Clubbing of the fingertips (hypertrophic osteoarthropathy)
- Polycythemia
Why are we extremely careful not to allow any sort of air bubbles in IV tubing/syringes in patients with R to L shunt?
The shunt permits venous emboli to bypass the lungs and directly enter the systemic circulation
4 considerations related to anesthetic practice in patients with right to left shunt
- Obstruction of pulmonary blood flow
- Delayed uptake of inhaled anesthetics d/t bypassing pulmonary circulation
- Judicious avoidance of air in lines
- Increased PaCO2 and ETCO2 gradient
What is a major condition that prolongs transitional circulation?
Hypoxemia
Do we see any sort of affect from left to right shunts on inhalation induction?
No; There is a higher blood concentration of anesthetic in the pulmonary circulation which leads to a reduction in uptake, but this is nullified due to recirculation of pulmonary blood causing an increased uptake of anesthetic
3 Hemodynamic consequences of mixed shunts
- Hypoxemia of varying degrees
- Qp/Qs very dependent on PVR and SVR
- Elevcated hct and hyperviscosity
4 Hemodynamic goals with mixed shunts
- Adjust PVR/SVR for optimal Qp/Qs and oxygen saturations
- Decreased FiO2 and Increased PaCO2 if Qp/Qs is high
- Improve mixed venous saturation
- Optimize tissue O2 delivery
2 examples of mixed shunts
- Hypoplastic left heart
2. Truncus arteriosus
By what age does PVR reach near adult levels
6 months
At what point does PVR lead to a right to left shunt through DA and FO?
When PVR exceeds SVR
Why does PVR significantly decrease after birth?
Lung expansion (Incr. FRC) and oxygenation (Incr. Alveolar PO2)
9 factors that reduce PVR
- No PEEP
- Low airway pressures
- Lung expansion to FRC
- High Fio2
- Respiratory and Metabolic Alkalosis
- Low Hematocrit
- Blunted stress response (Deep Anesthesia)
- Nitric Oxide
- Vasodilators
5 Pharmacologic Descriptors of Nitric Oxide
- Selective pulmonary vasodilator
- Endogenous and produces vascular smooth muscle relaxation and vasodilation
- Delivered by ventilation to treat Pulmonary HTN
- 20-40 ppm usually used
- Rebound pulmonary htn can occur after discontinuation
What is the best way to alter PVR without making major changes to SVR?
Ventilation changes
PaO2 and PaCO2 goal to decrease PVR
PaO2 > 60mmHG
PaCO2 30-35 mmHg
2 major factors that increase pulmonary output
- Decreased PVR
2. Increased SVR
2 major factors that increase systemic output
- Increased PVR
2. Decreased SVR
Why is a good premed important in pedi patients with a shunt?
To reduce distress so that we do not exacerbate symptoms and put us in a bad spot hemodynamically
How do we protect the lips from the TEE remaining in place?
Tegaderms over the lips!
NPO time for clear liquids?
2 hours
Describe NIRS (5)
- Near infrared spectroscopy
- Real time monitoring of tissue oxygenation
- Value obtained is a reflection of underlying tissue
- Used to assess brain O2 delivery
- A 20% drop from baseline is considered significant and interventions need to be performed to improve this
Calcium Chloride concentration for pedi heart pts >10kg, <10kg
> 10 kg: 100mg/mL
<10kg: Diluted to 10mg/mL
Phenylephrine and Epinephrine dilution doses for pedi hearts (3)
- 1 mcg/mL (<3kg)
- 10 mcg/mL
- 100 mcg/mL (>40kg)
What type of intubation do we normally perform for pediatric hearts?
Nasal = need magills!
Why do we use a small (wee) medline in pediatric hearts?
So that we do not have to use a ton of fluid to flush drugs, want to connect this to a proximal port
Is CVP in pediatric hearts always representative of right atrial pressure?
No, this is dependent on the type of defect present
When do we use steroids in pediatric heart patients?
Only if we go on pump to reduce the inflammatory response associated
4 maintenance drugs for pediatric hearts
- Methadone 0.1-0.2 mg/kg
- Rocuronium
- Sevo
- Sufentanil infusion
LR, Dopamine, Epinephrine, Milrinone and Sufentanil infusion rates in pediatric hearts
- LR @ low basal rate based on patient weight
- Dopamine @ 5mcg/kg/min
- Epinephrine @ .05mcg/kg/min
- Milrinone @ 0.5mcg/kg/min
- Sufentanil @ 0.5mcg/kg/hr started after induction and foley in place, prior to TEE placement
Why do we always use the same pump set up in pediatric hearts?
To reduce the threshold for error in emergencies
6 other transfusions commonly used in pediatric hearts
- TXA esp. in re-do
- Prexedex @ 0.3-0.7 mcg/kg/hr
- Nicardipine @ 0.5mcg/kg/hr up to 1mcg/kg/hr titrated at 0.5 mcg increments
- Vasopressin
- Norepinephrine
- Alprostadil (PGE1) : Keeps PDA open
Why might we need to give FFP in pediatric heart patients prior to incision?
Low AT3 levels
When do we usually expect to administer platelets and cryo in pediatric heart cases?
After coming off cardiopulmonary bypass
How do we prepare blood for pediatric hearts?
Blood should be in the room and checked for quick administration if needed
How do we administer FFP if AT3 is low?
20mL/kg administered total.
10mL/kg administered IV.
10mL/kg given to the perfusionist.
How much heparin do we administer and what is our goal ACT in pediatric hearts?
300-400 units/kg heparin for an ACT >300 seconds
How does heparin work with AT3
Combines with AT3 to bind and inhibit thrombin, so if AT3 levels are low, then heparin is going to be less effective
5 considerations when going on pump for pediatric hearts
- Dose midazolam
- Re-dose NMB (roc)
- Once perfusionist verifies you are at full flow, you can stop ventilation or flutter the lungs
- Begin to cool the patient (reduction in cerebral and whole body O2 consumption by 5-6% for each 1 degree Celsius decrease in body temp)
- Watch NIRs trend
What does it mean to “flutter” the lungs
High rate, low pressure allows for small tidal volume to prevent atelectasis
4 consideration when coming off pump for pediatric hearts
- Temp > 35 Celsius (use a nasal and bladder temp, remember that nasal will get there quicker so base your goal of bladder temp)
- Stable rhythm (pacemaker ready)
- Good cardiac function assessed by cardiologist using TEE
- Products ready? (2 platelets and 2 cryo or 3 plt, 3 cryo, 1 ffp for bigger cases such as hypoplastic left heart)
(4) Describe modified ultrafiltration (Muf) when coming off pump in pediatric hearts
- Allows the bypass circuit to remain primed with pt blood volume and pump circuit volumes to be hemoconcentrated.
- usually lasts 10-15minutes
- Allows for greater hemoconcentration especially in children
- Do not administer protamine during this time as we are still on pump
What is the usual dose for protamine with pediatric hearts?
1-1.5mg per 100 units of heparin, may sometimes have to re-dose, check act after administration
What is the rule of 4’s for coming off cardiopulmonary bypass with pediatric hearts
pH 7.4
HcT 40%
PCO2 40mmHg
What device do we use to deliver nitric oxide?
NOXBOX
5 examples of volume overload lesions for pediatric heart patients
- PDA
- ASD
- VSD
- Atrioventricular septal defect/AV canal (AVC)
- Truncus arteriosus
What patients is a PDA often found in?
preterm infants (10% of all CHD)
4 conditions that cause delayed functional closure of PDA
- Preterm infants at risk d/t higher circulation of prostaglandin levels
- Decreased degradation of PGE1
- Increased production of PGE1
- Diminished sensitivity to ductal constricting effects of oxygen
Who performed the first successful PDA ligation?
Dr. Robert Gross in 1938
3 conditions PDA can be associated with
- Necrotizing enterocolitis
- Renal Failure
- Intraventricular hemorrhage
3 interventions to close PDA
- Percutaneously in the cath lab by interventional cardiologist
- Surgically closed in OR via left thoracotomy
- Surgically closed in NICU on infants less than 1kg and ventilated
5 steps in the physiology of PDA
- Initially high PVR after birth limits the shunt magnitude
- After PVR decreases a left to right shunt develops that increases pulmonary blood flow
- LV output must increase to maintain systemic blood flow
- Increase LA pressure develops from increased PBF
- Pulmonary artery hypertension can develop
What position is the patient placed in for closure of PDA
right lateral decubitus to allow for a left thoracotomy
During a thoracotomy for PDA closure, when can we expect some difficulty with lung ventilation?
during lung retraction
What nerve can be damaged with a left thoracotomy
left RLN
6 anesthetic considerations for PDA closure
- Maintain CO
- Avoid decreases in pvr:svr to maintain systemic blood flow
- avoid increases in pvr:svr
- 2 pulse oximeters
- 2 large bore IVs at minimum
- Upper and lower extremity blood pressure cuff.
How does an increased PVR affect pediatric shunts? Decreased PVR?
Increased PVR: can reverse shunt and compromise blood flow to the lungs
Decreased PVR: can increase the left to right shunt and reduce systemic blood flow
What is normal for opioid usage during PDA closure?
High dose such as 50-100mcg/kg
What type of IVF are normally used for PDA closure?
Dextrose containing
Describe preductal and postductal oximetry
Right hand is perfused by aorta and should have good flow (preductal)
Left hand and feet are perfused by mixed blood (postductal)
A patient has a >10% difference between the preductal and postductal oximetry, what could this indicate?
ductal dependent lesions or PDA present
What type of shunt is present with an ASD?
left to right, meaning this is an acyanotic defect
What percentage of PFO’s remain patent after birth?
about 30%
What age group are PFOs present in about 50% of patients?
Children < 5 years of age
By what age are 15% of PFOs closed?
4 years of age
Where is the defect for ASDs?
in the intra atrial septum
What is the most common ASD?
Secundum Type
Which ASD is also known as an unroofed coronary sinus?
Coronary sinus defect
Which ASD can be associated with a cleft mitral valve?
Primum atrial septal defect
Which ASD can be associated with anomalous pulmonary drainage?
Superior sinus venosus defect
Which ASD is dependent on pvr:svr
Large, unrestrictive ASDs (<1mm), as small, restrictive ASDs have minimal flow
Where do we see volume overload in patients with ASDs?
RA, RV and LV