9.6 Pulmonary Hypertension Flashcards
Define pulmonary hypertension (PHT).
severe?
Pulmonary hypertension is defined as a mean pulmonary artery pressure
(PAP) > 25 mmHg at rest
or
with a pulmonary capillary wedge pressure (PCWP) < 15 mmHg.
_______________________________________________________
Pulmonary hypertension is considered moderately severe when mean
PAP > 35 mmHg.
PAP > 50 mmHg can be associated with right ventricular failure.
How can you classify PHT?
WHO classification
Group 1. Pulmonary arterial hypertension (PAH)
Group 2. Pulmonary venous hypertension due to left heart diseases
Group 3. Pulmonary hypertension due to lung diseases and/or hypoxemia
Group 4. Chronic thromboembolic pulmonary hypertension
Group 5. PH with unclear multifactorial mechanisms
Group 1. Pulmonary arterial hypertension (PAH)
- Idiopathic (BMPR2 gene mutation)
- Drug- and toxin-induced
- Associated with connective tissue diseases
- Congenital heart disease
Group 2. Pulmonary venous hypertension due to left heart diseases
- Systolic dysfunction
- Diastolic dysfunction
- Valvular disease
Group 3. Pulmonary hypertension due to lung diseases and/or hypoxemia
- Chronic obstructive pulmonary disease
- Interstitial lung disease
- Sleep-disordered breathing
Group 5. PH with unclear multifactorial mechanisms
- Haematological disorders:
myeloproliferative disorders, splenectomy - Systemic disorders:
sarcoidosis, neurofibromatosis, vasculitis - Metabolic disorders:
glycogen storage disease, thyroid disorders
Explain the pathophysiology of PHT.
- Pulmonary vasculature
Any of the above causes result in medial hypertrophy
and intimal fibrosis of the pulmonary vasculature thereby narrowing the vessels.
- Pulmonary vasculature
The endothelin, nitric oxide, and prostacyclin pathway
also have a role in the development of PHT.
The end result is an increase in pulmonary vascular pressures.
- Right ventricle
As the right heart has to pump against an increased afterload,
it hypertrophies and fails when the PAP is > 50 mmHg.
- Right ventricle
- Left ventricle
Left ventricular failure can then ensue,
due to both reduced volume reaching the left heart
and interventricular septal interdependence. - Coronary perfusion
The coronary circulation to the right heart is dependent on perfusion
pressure at the aortic root, which in turn is dependent on systemic
vascular resistance (SVR).
- Coronary perfusion
SVR must be aggressively defended in order to maintain coronary perfusion
to the right heart.
Ischaemia to the right ventricle can put in place a
downward spiral of right heart failure,
with ensuing cardiovascular collapse.
What are the symptoms of PHT?
Symptoms
- Dyspnoea (60% of patients)
- Weakness (19%)
- Recurrent syncope (13%)
What are the Sx of PHT?
Signs
* Fixed or paradoxical splitting of second heart sound
in the presence of severe right ventricular dysfunction
.
* Pulmonary and tricuspid valve regurgitation murmur.
- Elevated jugular venous pressure (JVP) in the presence of volume
overload and right ventricular failure.
Large ‘v’ waves are present in associated severe tricuspid regurgitation.
- Hepatomegaly and ascites.
- Dependent pitting edema of varying degrees
How would you diagnose PHT?
Clinical findings
* As above
Investigations
* CXR
- ECG:
right atrial enlargement,
right axis deviation,
right ventricular hypertrophy, and
characteristic ST depression and T-wave inversions in the anterior leads - Echocardiography:
useful for assessing right and left ventricular function,
pulmonary systolic arterial pressure and
excluding congenital anomalies
and valvular disease - V/Q scanning:
excludes interstitial lung disease and thromboembolic disease - Pulmonary angiography:
excludes thromboembolic disease - Cardiac catheterisation:
assesses pressures and determines pulmonary vasoreactivity - Cardio pulmonary exercise testing:
6-minute walk testing commonly used
as a surrogate test for aerobic capacity and severity
What is the finding on the chest radiography
Right heart
- Right atrial enlargement may be present if significant tricuspid
regurgitation is present, which is shown as a widened right heart border. - Right ventricular enlargement is seen as a decrease in the retrosternal
space on the lateral image.
Pulmonary vasculature
- Enlarged central pulmonary arteries that taper distally.
- Increase in the transverse diameter of the right interlobar artery is
indicative of pulmonary hypertension. - Peripheral vessel opacity—oligaemic lung fields.
- Kerley B lines may be present. These indicate the presence of pulmonary
venous hypertension.
What are the treatment options?
- Dilators
- Ancillary treatment.
- Surgical
What are the treatment options?
Dilators
Dilators
- Calcium channel blockers—
dilate the pulmonary resistance vessels and
lower the pulmonary artery pressure. - Epoprostenol—
intravenous, parenteral prostacyclin analogue - Bosentan—
oral, endothelin receptor antagonist - Sildenafil—
oral phosphodiesterase type 5 (PDE-5) inhibitor
Ancillary treatment
Ancillary treatment
* Oxygen
* Digoxin
* Diuretics
Surgical
- Atrial septostomy—palliative
- Lung transplant
What are the anaesthetic implications?
Induction
Maintenance
Monitoring
Induction
* All IV induction drugs have been safely used,
although Ketamine can increase PVR.
- Non-depolarising and depolarising muscle relaxants can be used safely.
Maintenance
* All volatile agents can be safely used in PHT except nitrous oxide.
Monitoring
* Invasive blood pressure and cardiac output monitoring.
- Pulmonary artery catheter is indicated in severe cases and in major surgery.
What are the anaesthetic implications?
Drugs
Blocks
Specific drugs
RV failure and raised PVR can be targeted with inhaled selective pulmonary
vasodilators such as nitric oxide and prostacyclin.
Neuraxial blocks
No direct effect on PVR but can cause
decreased SVR and coronary perfusion pressure.
It can also lead to bradycardia due to inhibition of cardioaccelerator fibres.
Decreased preload and bradycardia can be detrimental.
Avoid GA
Rx high PVR
Avoid
- Increased PVR
- Decreased venous return
- Marked decreases in SVR
- Myocardial depression
- Tachy/brady arrythmias
Treat high PVR:
Hyperventilation,
nitric oxide,
morphine,
glyceryl trinitrate,
sodium nitroprusside,
tolazoline,
prostacyclin (PGI2), isoprenaline, and aminophylline
What increases PVR?
Nitrous oxide,
adrenaline, dopamine,
protamine, serotonin, thromboxane A2,
prostaglandins such as PGF2 α and PGE2,
hypoxia, hypercarbia, acidosis, PEEP and lung hyperinflation,
cold, anxiety and stress
