Hemodynamics, Pharmacology, and Updates. Amanda L. Affleck CRNA, MAE. Providence Anesthesia Services. Five Basic Questions. Is the patient acyanotic or cyanotic?. Is pulmonary arterial blood flow increased or not?. ID: 401707
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Congenital Heart Defects
Hemodynamics, Pharmacology, and Updates
Amanda L. Affleck CRNA, MAE
Providence Anesthesia Services
Slide2Slide3Five 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?
Slide4Acyanotic 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.
Slide5Slide6Acyanotic Defects
OBSTRUCTION On the left side decreases systemic flow=hypoperfusionSHUNT Left-to-right Pulmonary over-circulation may lead to pulm htn, and eventually pulmonary vascular obstructive disease (Eisenmenger’s Syndrome)
Slide7Acyanotic Defects
Ventricular Septal DefectAtrial Septal DefectPersistent Ductus ArteriosusAortic StenosisCoarctation of the AortaComplete Common Atrioventricular Canal
Slide8Acyanotic Defects
What increases
left-to-right
shunt?
Dramatic increase in SVR relative to PVR.
Dramatic decrease in PVR relative to SVR.
Slide9Cyanotic Defects
OBSTRUCTION On the right side, decreases pulmonary flow=hypoxemiaSHUNT Right-to-left Less blood reaches the lungs for oxygenation Venous blood mixes with systemic flow
Slide10Cyanotic Defects
Pulmonary StenosisTetralogy of FallotTransposition of the Great ArteriesTricuspid AtresiaPulmonary Atresia
Atresia: absence or closure of a natural passage of the body
Slide11Cyanotic Defects
What increases
right-to-left
shunt?
Decrease in SVR.
Increase in PVR.
Slide12How 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.
Slide13PVR & SVR
SVR
nml
values and definition
SVR
Inhalational agents
H
2
release
Ganglionic blockade
SVR
RX
Slide14PVR & SVR
PVR
Normal 90-250 dynes/s/cm
-5
PVR
Hypoxemia
Acidosis
N
2
O
Pain
RX
Slide15Slide16Anesthetic 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 SpO
2
.
De-bubble and filter IV lines.
Slide17Anesthetic 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.
Slide18Anesthetic 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.
Slide19Anesthetic Considerations for Acyanotic Defects
Induction:
Potent intravenous and inhalational agents will decrease SVR.
Slide20Anesthetic Considerations for Acyanotic Defects
IntraOp
:
Avoid acute & long-term increases in SVR or decreases in PVR (worsens the left-to-right shunt).
High O
2
concentrations decrease PVR and increase SVR.
Hypoxemia increases PVR & decreases SVR.
Acidosis increases PVR.
IV bolus
meperidine
may increase PA pressures.
Slide21Anesthetic Considerations for Acyanotic Defects
IntraOp
:
Positive pressure ventilation and
Valsalva
maneuvers may cause transient reversal of flow in left-to-right shunts.
Slide22Anesthetic Considerations for Acyanotic Defects
PostOp:
Drugs to decrease pulmonary
htn
:
Inhaled nitric oxide, prostacyclin, prostaglandin I
2
, prostaglandin E
2
Phosphodiesterase inhibitors
NTG, Nitroprusside
Pain control: Pain causes increased sympathetic stimulation=
inc
PVR, but
oversedation
causes
hypercapnia
=
inc
PVR.
Slide23Slide24Anesthetic 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 SpO
2
.
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.
Slide25Anesthetic 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.
Slide26Anesthetic 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
Slide27Anesthetic Considerations for Cyanotic Defects
Induction:
By decreasing SVR IA’s may increase shunt and cyanosis, so titrate agents up slowly.
A fall in SpO
2
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.
Slide28Anesthetic 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.
Slide29Anesthetic Considerations for Cyanotic Defects
IntraOp
:
EtCO
2
significantly
underestimates PaCO
2
.
Increases in physiologic dead space (ventilation without perfusion)
Increases in venous admixture (right-to-left shunt)
As right-to-left shunt increases, etCO
2
is less accurate.
Slide30Anesthetic Considerations for Cyanotic Defects
PostOp:
Adequate analgesia without sedation-induced
hypercapnia
.
Pain yields sympathetic stimulations which
PVR.
Over-sedation yields
hypercapnia
which
PVR.
Slide31Right Ventricular Failure
&
Pulmonary Arterial Hypertension
Slide32Pulmonary 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 A
2
, serotonin) which act on the smooth muscle cells.
Slide33endothelial cells
smooth muscle cells
Nitric oxide
Prostacyclin
vasodilate
Thromboxane A2
Endothelin-1
vasoconstrict
Slide34Pulmonary Hypertension
mPAP greater than 25 mmHgPVR greater than 240 dynes/cm/-5
Slide35WHO 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
)
Slide36Intraoperative causes of PH
Hypoxia,
hypercarbia
, acidosis
Embolism (thrombus, CO
2
, air)
Bone cement
Protamine
Cardiopulmonary bypass
Ischemia-reperfusion syndrome (clamping,
declamping
of aorta)
Loss of lung vessels (
pneumonectomy
)
Slide37Right Ventricle
Thin-walled, highly compliant, but poorly contractile chamber.
Under normal conditions ejects blood against 25% of the afterload, compared to the LV.
Slide38*
*RV failure
Slide39RV 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.
Slide40The 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.
Slide41Thin-walled RV dilates in the face of increased afterload.
Septal shift compresses the LV chamber, further compromising systemic output.
Slide42Anesthetic Management
Slide43Anesthetic Management
PreOp
:
Maintain any current pulmonary vasodilator therapy to avoid rebound pulmonary hypertension.
Careful sedation to avoid respiratory acidosis and subsequent
in PVR.
Slide44Anesthetic 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.
Slide45Anesthetic Management
Arterial line
Central venous pressure monitoring of fluid trends
Trans esophageal echo
Slide46Induction 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.
Slide47Maintenance
Reduce PVR
Avoid metabolic acidosis
Adequate analgesia & anesthesia to avoid catecholamine surge
Avoid shivering
Slide48
Maintenance
Maintain RV function
Avoid
hypovolemia
or
fluid overload (RV is less pre-load responsive compared to LV)
Appropriate fluid challenge is 250-500ml
Slide49Ventilatory Strategies
Avoid HPV with high FiO
2
Moderate
hyperventilation (PaCO
2
30
-35
)
PEEP <15cmH
2
O (compression of alveolar vessels
RV afterload)
Avoid
high airway
pressures which compress pulmonary vasculature.
No Nitrous!!!
Slide50Pharmacologic 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)
Slide51Pharmacologic Support
Inhaled Nitric Oxide Potent and specific pulmonary vasodilator Immediately inactivated in the circulation by hemoglobin binding.Sildenafil ’s PVR Only available orally
Slide52Post Op
Factors that increase PVR
Hypoxemia
Acidosis
Hypercapnia
Hypothermia
Increased sympathetic stimulation
Slide53Slide54Slide55Slide56Slide57
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