Anesthetic Considerations in Pulmonary Hypertension,
by Dr. Stephanie Grant.
Hello.
My name is Stephanie Grant and today I'm
going to be talking to you about pulmonary hypertension.
The goals of today's talk are to talk
about perioperative management of pulmonary hypertension,
including during the pre-operative, intra-operative,
and post-operative time.
We will also talk about pulmonary hypertensive crisis.
Background.
Pulmonary hypertension is a rare disease in neonates, infants,
and children.
Patients with pulmonary hypertension
present for cardiac and non-cardiac surgery,
and for general anesthesia and sedation.
Pulmonary hypertension is associated
with significant morbidity and mortality,
and poses an increased perioperative risk.
Patients with pulmonary hypertension
have increased risk of arrhythmias, cardiac arrest,
and death during the perioperative time.
This graph depicts three different studies.
The small green bar, which is on the left of each grouping,
shows the Pediatric Perioperative Cardiac Arrest
Registry.
This depicted a study which involved all patients
regardless of diagnosis and regardless of surgery
that they were having.
The incidence of cardiac arrest in these patients
was very small at .014%, and of those patients,
the risk of death was .0036%.
The study depicted in the red bar
indicates a study of patients with pulmonary arterial
hypertension who had general anesthesia for procedures
in the cardiac cath lab and also for non-cardiac surgery.
The incidence of cardiac arrest in these patients was 1.17%,
and the incidence of death in these patients was .78%.
These studies indicate that the incidence of cardiac arrest
and death is significantly higher in patients
with pulmonary hypertension.
This study indicates that the perioperative complications
are directly related to the severity
of pulmonary arterial hypertension.
Patients with supra-systemic right ventricular pressures
have greater complications during surgery
than patients with less severe forms
of pulmonary hypertension.
The baseline supra-systemic pulmonary arterial hypertension
is a significant predictor of major complications
during anesthesia.
This table is a nonvalidated tool
that looks at patients who may have low risk or high risk
complications during general anesthesia.
The patients are grouped into low risk or high risk
based on patient factors, surgery factors,
as well as the anesthetic factors involved.
Case Example - Part 1.
Let's look at a case as an example of a patient
with pulmonary hypertension.
The patient is a 15-year-old male
who is evaluated prior to an open reduction
internal fixation of his tibia.
The patient sustained this fracture
after falling while skateboarding.
The patient was diagnosed with pulmonary hypertension
one year ago after a syncopal event.
He reports occasional dyspnea on exertion,
but is otherwise doing OK.
His past medical history includes
idiopathic pulmonary hypertension.
He has never had surgery, and his medications
include Sildenafil, and he uses nasal cannula oxygen just
at night.
What is your anesthetic plan for this patient?
Pre-operative Anesthetic Management.
The pre-operative management for this patient and any patient
with pulmonary hypertension should include a visit
to the pre-op clinic if possible.
A thorough history and physical should
be performed for the patient, and review of any echo and cath
lab reports that the patient may have.
For a patient with an echo report,
it is important to look at the most recent echo report,
specifically looking at the patient's anatomy,
and if the patient has any pop-off.
A pop-off is a left to right shunt
which may convert to a right to left shunt
if the patient has an acute event,
and the right ventricular pressures
begin to increase in the heart and are greater
than the left pressures.
This is important because it serves
to decompress the right side of the heart
and to increase cardiac output.
On the echo report, it is also important to look
at the patient's function, look at the patient's
pulmonary arterial pressure as well as the right ventricular
pressure.
In our case example, looking at the echo report
we see that this patient has a flattened septal position
in systole, which is consistent with right ventricular
pressures greater than one half systemic levels.
This indicates that the patient does
have an increased risk for complications during surgery
due to the greater than one half systemic levels.
This patient also has qualitatively good
biventricular systolic function, which is a good sign.
On catheterization reports, it is
important to look at the pulmonary arterial pressure,
looking at the systolic, diastolic and mean levels.
Also, look at the right ventricular
pressure, the pulmonary vascular resistance,
the structure of the heart, the function of the heart,
to look at measured wedge pressures, as well
as the results of vasoactive testing.
For our sample patient, his cardiac catheterization report
indicated that at baseline, his right ventricle systolic
pressure was 72 millimeters mercury,
and systemic pressure was 100 millimeters mercury.
This indicates that his right ventricle pressure
is greater than one half systemic,
meaning that this places him at greater risk for complications
during general anesthesia.
During vasoreactive testing at baseline of 21% oxygen,
the patient had a mean pulmonary arterial pressure of 50,
and a pulmonary vascular resistance of 10.6.
During vasoreactive testing with 100% oxygen and exposure
to inhaled nitric oxide, both his mean pulmonary artery
pressure and pulmonary vascular resistance did decrease.
This was a mild decrease, but does
indicate that he does have vasoreactivity
within his pulmonary vasculature and would respond well
to inhaled nitric oxide or 100% oxygen
if he does have an acute event during surgery.
It is important to discuss the post-op plan
with the patient's cardiologist or an ICU physician.
It is important in these patients to minimize NPO times,
avoiding dehydration and decreased preload
during the pre-op time.
It is also very important to prepare emergency drugs
before the patient even enters the operating room.
These include having things such as inotropes,
including epinephrine, ready.
Inhaled nitric oxide available and in the operating room,
and to also consider ECMO on standby,
depending on the severity of the patient.
Intra-operative Anesthetic Management.
For anesthetic management of this patient,
it is important to give an adequate premedication,
including a benzodiazepine, or even ketamine.
It's important to have a calm patient
because a crying, screaming, and agitated patient
will lead to increased pulmonary vascular resistance,
will lead to changes that will cause
an acute event for pulmonary hypertension.
If the patient is on a pulmonary vasodilator
such as a targeted therapy, it is
important to continue this medication
during the perioperative time.
The main goals of an anesthetic management
for patients with pulmonary hypertension
is to avoid increases in pulmonary vascular resistance
and avoid decreases in systemic vascular resistance.
Decreases in systemic vascular resistance
will lead to changes that cause decreased coronary perfusion
pressure and decreased oxygen delivery to the myocardium,
leading to ischemia, which may precipitate
a pulmonary hypertensive crisis.
For these patients, it is important to place standard ASA
monitors on the patient before induction.
And depending on the case and the patient,
to determine if an arterial line is needed.
Induction of these patients, it's
important to use a balanced anesthetic technique.
It's important to maintain a dedicated
IV if the patient comes to the operating room
already on a pulmonary vasodialator infusion.
Stopping this infusion, even for a brief second for induction,
can lead and precipitate to an acute pulmonary hypertensive
crisis.
An IV induction is preferred for these patients.
However, it is possible to do an inhalational induction
on these patients, if the patient has
adequate ventricular function.
The potential problem with an inhalational induction
is that if you lose the patient's airway,
the patient will begin to hypoventilate,
become hypercarbic.
This will lead to acidosis and eventually hypoxia,
which is going to cause the patient
to have an acute pulmonary hypertensive crisis.
The ideal anesthetic for pulmonary hypertension
includes one in which it causes pulmonary vasodilation,
maintains cardiac contractility, maintains systemic vascular
resistance, and also maintains cardiac output.
However, an ideal anesthetic for pulmonary hypertension
does not exist.
We have our drugs that we are very familiar with,
our volitile anesthetics and our IV anesthetic agents.
However, each is not a perfect anesthetic
for pulmonary hypertension.
Most have good qualities, but also
have an element that causes hemodynamic instability,
potentially for a patient with pulmonary hypertension.
The use of ketamine in patients with pulmonary hypertension
has been controversial in the past.
However a study by Dr. Paul Hickey at Boston Children's
Hospital indicated that ketamine does not
change the pulmonary vascular resistance,
unless the patient also is hypoventilating and becomes
hypercarbic.
A balanced anesthetic technique is the best technique
for patients with pulmonary hypertension.
This technique includes sub-anesthetic doses
of multiple anesthetics in order to achieve an anesthetic state.
The anesthetic management for airway of these patients
is selected based on the procedure.
If the patient is to be intubated,
there needs to be an adequate depth of anesthesia
before intubation is achieved.
An LMA can be used, however it is
important to avoid hypoventilation in order
to avoid hypercarbia, which can lead
to increases in pulmonary vascular resistance.
For maintenance of these patients,
it is important to continue the depth of anesthetic that
is adequate for the stimulus.
A volatile inhalational anesthetic
or a total intravenous anesthetic
can be used for maintenance of these patients.
For ventilation of these patients,
it is very important to avoid hypercarbia and respiratory
acidosis, which both can lead to increases
in the pulmonary vascular resistance
as well as avoiding excessively low or high tidal volumes,
which both can increase the pulmonary vascular resistance.
And it is also important to avoid
excessive low or high peak inspiratory pressures, which
will lead to an increased pulmonary vascular resistance.
As well as avoiding increases in PEEP,
which will increase pulmonary vascular resistance.
The emergence of these patients.
It is very important to minimize noxious stimuli.
Suctioning the endotracheal tube or the patient's oropharynx
should be done while the patient is
under a deep plane of anesthesia.
Tracheal suction and oropharyngeal suction
have been known to precipitate an acute pulmonary hypertensive
crisis.
It is very important to have a smooth and calm extubation
of these patients.
Post-operative Anesthetic Management.
It is important to have adequate post-op monitoring for patients
with pulmonary hypertension.
If the patient is to be monitored
in the PACU versus the ICU depends
on patient factors, surgical factors,
and anesthetic factors.
It is very important in the post-operative course
to provide adequate analgesia and antiemesis,
and also to avoid hypoxia, hypotension, and hypovolemia.
It is very important to be prepared
when you have a patient with pulmonary hypertension,
and to always stay two steps ahead of potential changes
that can occur in these patients.
Case Example - Part 2.
Let's go back to our sample case--
a 15-year-old male with past medical history
of pulmonary hypertension for an ORIF of his tibia.
The patient received a pre-med consisting of midazolam,
and on induction a balanced anesthetic technique
was used with fentanyl, ketamine, propofol,
and rocuronium.
The patient remained stable on induction.
He had an easy intubation, and was also hemodynamically
stable on-- during intubation.
However, 30 minutes after incision, the patient suddenly
had a decrease in oxygen saturation, blood pressure
and end-tidal carbon dioxide.
What is your differential diagnosis,
and what are you going to do to treat this patient?
Pulmonary Hypertensive Crisis.
Patients with pulmonary hypertension,
you should always think if the patient decompensates,
the first thing that should be on your differential diagnosis
is a pulmonary hypertensive crisis.
The definition of pulmonary hypertensive crisis
is an acute on chronic increase in pulmonary vascular
resistance, resulting from an acute increase
in vascular tone of the reactive portion
of the pulmonary vasculature.
During these changes, a rapid increase in pulmonary vascular
resistance will lead to an increased right ventricular
afterload, causing right ventricular pressure
to increase, which will in turn lead
to decreases in the left ventricular preload, decreases
in coronary perfusion pressure, and eventually causing
ischemia, which will lead to changes such as hypoxia
and acidosis, which will further increase this cycle.
During an acute event, it is possible to have cardiac arrest
with low cardiac outputs.
If the patient does develop cardiac arrest,
it may be difficult to resuscitate these patients.
CPR may be ineffective due to an enlarged right ventricular
size that compresses the left ventricle, causing
ineffective cardiac output.
Pulmonary hypertensive crisis can happen at any time
during the perioperative period, and this can occur even hours
after the intra-operate time.
Intra-operative findings of pulmonary hypertensive crisis
include sudden desaturation, systemic hypotension,
decreases in end-tidal CO2, sinus tachycardia,
elevated central venous pressure, and a new onset
EKG change of RV strain or ischemia,
as well as bradycardia, which is an ominous sign
of impending cardiac arrest.
If you have access to a transesophageal
echocardiograph, you will see that the right ventricle is
dilated and poorly contracting, as well as an under filled
left ventricle.
And you will see pulmonary regurgitation
and tricuspid regurgitation, as well as
elevated right ventricular pressures.
For treatment of a pulmonary hypertensive crisis,
it is important to get rid of the stimulating event
and to stabilize the patient.
It is important to administer 100% oxygen to the patient.
Oxygen is a vasodilator and will vasodilate
the pulmonary vasculature.
It is also important to hyperventilate the patient.
Hyperventilation will lead to decreases in carbon dioxide
levels, and therefore vasodialate
the pulmonary vasculature.
It's also important to exclude other causes that
may mimic a pulmonary hypertensive crisis,
such as a pneumothorax.
It's important to decrease mean arterial pressures if possible,
and to correct metabolic acidosis.
Acidosis will lead to increases in pulmonary vascular
resistance and further increase the acute event.
It is also important to support the heart of the patient,
providing an inotrope such as epinepherine.
If the patient is in the middle of surgery,
it's important to administer proper analgesia
to get rid of any noxious stimuli which
may be precipitating an event.
It is also important to initiate ECMO early in these patients
in order to stabilize the patient
and provide adequate cardiac output to the patient.
If the patient does develop cardiac arrest,
it is very important to start PALS algorithm.
However, keep in mind that CPR may
be ineffective due to the enlarged right
ventricle compressing the left ventricle
and leading to decreased cardiac output.
Today's pulmonary hypertension talk,
the teaching points are: pulmonary hypertension
is associated with significant morbidity and mortality
in the perioperative time, careful planning
is very important pre-operatively,
and pulmonary hypertensive crisis
can occur both intra-op and post-op.
Thank you very much.
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