24.8 Pulmonary Hypertension

Question 1

a) Define pulmonary hypertension. (2 marks)

Answer 1

Mean pulmonary artery pressure of 25 mm Hg

or greater at rest or 30 mm Hg on exercising.

Question 2

b) What are the causes of pulmonary hypertension? (5 marks)

Answer 2

1&raquo_space; Pulmonary arterial hypertension:

• Idiopathic
(may be familial,
abnormal genes have been identified).

• Associated with systemic disease such
as connective tissue diseases,
HIV, chronic haemolytic anaemia.

• Drug and toxin associated.

• Persistent pulmonary hypertension of the newborn.

2&raquo_space; Left heart disease.

3&raquo_space; Chronic lung disease.

4&raquo_space; Chronic thromboembolic disease.

5&raquo_space; Other unclear underlying cause.

Question 3

c) What are the specific anaesthetic goals when anaesthetising a patient with pulmonary
hypertension? (7 marks)

Answer 3

Chronic pulmonary hypertension results
in hypertrophy of the right heart.

It therefore requires better perfusion
due to the increased muscle bulk
but actually gets less,
resulting in ischaemia.

Coronary perfusion occurs in
diastole and is dependent on
aortic root pressure and
so is compromised by tachycardia,
poor left ventricular output and
reduced systemic afterload.

Reduced right ventricular output
and deviation of the interventricular septum
due to overfilling of the right ventricle
may result in reduced left heart filling
and consequent reduced output.

A rise in pulmonary vascular resistance
may result in acute right heart failure.

1 Avoidance of increased pulmonary vascular resistance.

Triggers include the following:
» Hypoxaemia.
» Hypercarbia.
» Hypothermia.
» Pain.
» Acidaemia.
» High airway pressures and PEEP.
» Use of nitrous oxide.

2 Avoidance of reduction in systemic vascular resistance (coronary perfusion being dependent
on perfusion pressure at aortic root):

> > Invasive blood pressure monitoring starting
prior to induction to facilitate
rapid response to a decrease in
blood pressure:
aim to maintain BP at preoperative values.

> > Cardiostable induction using
increased opioid dose,
reduced induction agent dose.

> > Use of vasoconstrictor to mitigate
vasodilatory effects of commonly used
anaesthetic agents.

3 Avoidance of reduction in preload:
» Treat blood loss rapidly.

> > Appropriate fluid loading in response
to vasodilatory effects of general
or neuraxial anaesthetic techniques.

> > Consideration of cardiac output monitoring to guide fluid administration.

4. Maintenance of sinus rhythm, normal rate:

> > Avoidance of causes of tachycardia:
pain, light anaesthesia, drugs.

> > Avoidance of bradycardia:
prompt management of reflex bradycardia
due to vagal stimulation,
beware of effect of loss of thoracic sympathetic
stimulation associated with high spinal blockade

Question 4

d) What pharmacological treatments are available for this condition? (6 marks

Answer 4

Treatment of underlying condition:

> > Long-term anticoagulation with
warfarin to reduce thromboembolic risk.

> > Inhaled beta-2-agonists and steroid treatment
as part of the management
of chronic lung disease.

> > Diuretics and
angiotensin-converting-enzyme inhibitor
or angiotensin receptor blocker
as part of the management of left heart disease.

General treatment for patients
with pulmonary hypertension:

> > Warfarin or direct oral anticoagulants
(abnormal vasculature may
predispose to clots in the
pulmonary vessels causing further
deterioration).

> > Diuretics to reduce fluid retention
associated with right heart failure.

> > Oxygen to raise oxygen saturations
and cause pulmonary vasodilatation.

Targeted treatment to cause pulmonary vasodilatation
in idiopathic pulmonary arterial hypertension:

> > Calcium channel blockers.
Endothelin receptor antagonists.
Phosphodiesterase 5 inhibitors.
Prostaglandins.
Soluble guanylate cyclase stimulators.