9.6 Pulmonary Hypertension

Question 1

Define pulmonary hypertension (PHT).

severe?

Answer 1

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.

Question 2

How can you classify PHT?

Answer 2

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

Question 3

Group 1. Pulmonary arterial hypertension (PAH)

Answer 3

• Idiopathic (BMPR2 gene mutation)
• Drug- and toxin-induced
• Associated with connective tissue diseases
• Congenital heart disease

Question 4

Group 2. Pulmonary venous hypertension due to left heart diseases

Answer 4

• Systolic dysfunction
• Diastolic dysfunction
• Valvular disease

Question 5

Group 3. Pulmonary hypertension due to lung diseases and/or hypoxemia

Answer 5

• Chronic obstructive pulmonary disease
• Interstitial lung disease
• Sleep-disordered breathing

Question 6

Group 5. PH with unclear multifactorial mechanisms

Answer 6

• Haematological disorders:
  myeloproliferative disorders, splenectomy
• Systemic disorders:
  sarcoidosis, neurofibromatosis, vasculitis
• Metabolic disorders:
  glycogen storage disease, thyroid disorders

Question 7

Explain the pathophysiology of PHT.

Answer 7

1. • Pulmonary vasculature
     Any of the above causes result in medial hypertrophy
     and intimal fibrosis of the pulmonary vasculature thereby narrowing the vessels.

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.

2. • Right ventricle
     As the right heart has to pump against an increased afterload,
     it hypertrophies and fails when the PAP is > 50 mmHg.
3. Left ventricle
   Left ventricular failure can then ensue,
   due to both reduced volume reaching the left heart
   and interventricular septal interdependence.
4. • 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).

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.

Question 8

What are the symptoms of PHT?

Answer 8

Symptoms

• Dyspnoea (60% of patients)
• Weakness (19%)
• Recurrent syncope (13%)

Question 9

What are the Sx of PHT?

Answer 9

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

Question 10

How would you diagnose PHT?

Answer 10

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

Question 11

What is the finding on the chest radiography

Answer 11

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.

Question 12

What are the treatment options?

Answer 12

1. Dilators
2. Ancillary treatment.
3. Surgical

Question 13

What are the treatment options?

Dilators

Answer 13

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

Question 14

Ancillary treatment

Answer 14

Ancillary treatment
* Oxygen
* Digoxin
* Diuretics

Question 15

Surgical

Answer 15

• Atrial septostomy—palliative
• Lung transplant

Question 16

What are the anaesthetic implications?

Induction

Maintenance

Monitoring

Answer 16

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.

Question 17

What are the anaesthetic implications?

Drugs

Blocks

Answer 17

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.

Question 18

Avoid GA

Rx high PVR

Answer 18

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

Question 19

What increases PVR?

Answer 19

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