Pulmonary hypertension:

 

Summary:

If healthy

·       Pulmonary vessels should be under low pressure

·       Right ventricle does not adapt well to high afterload

·       Right coronary flow should be continuous

If PHTN

·       All the above is ruined

·       Susceptible to arrhythmias, RV ischaemia, RV failure

·       High risk of decompensation and death under anaesthesia

 

Causes:

Group 1

·       Pulmonary arterial hypertension (the highest risk kind)

o  Idiopathic

o  Connective tissue disease

o  Others

Group 2

·       Left heart disease

Group 3

·       Chronic hypoxic lung disease

Group 4

·       Chronic venous thromboembolism

Group 5

·       Unclear

 

Diagnosis:

Pre-capillary

i.e. lung

·       mPAP >20

·       PCWP <15

·       PVR > 3

·       TPG >12

·       DPG >7

Post-capillary

i.e. left heart

·       mPAP >20

·       PCWP >15

·       PVR <3

·       TPG <12

·       DPG <7

Combined

i.e. both

·       mPAP >20

·       PCWP >15

·       PVR >3

·       TPG >12

·       DPG >7

Confounders

·       Volume status

·       Cardiac output / exercise

 

Severity:

NYHA

1.    SOB with > ordinary activity

2.    SOB with = ordinary activity

3.    SOB with < ordinary activity

4.    SOB at rest

mPAP

·     Mild: 20-40mmHg (ESC & AHA)

·     Moderate: 40-55mmHg

·     Severe: >55mmHg

sPAP

·     Mild: 40-60mmHg

·     Moderate: 60-90

·     Severe: >90mmHg

 

Manipulation of PVR:

Physical

·     Minimise airway pressure

·     Normal lung volume (FRC)

Physiological

·     Normal O2

·     Normal CO2

·     Normal pH

·     Normal temp

Pharmacological

General:

·     Volatile anaesthetics

·     Propofol

Specific:

·     Nitric oxide (GTN, NTP, NO)

·     Prostanoids (iloprost)

·     Calcium channel antagonist

·     Endothelin receptor antagonists

Avoid:

·     Ketamine (probably not that bad? 2015 blue book)

·     Nitrous oxide

 

Goals:

Physiological goals

Supply the RV:

·     ↑SVR = ↑mAP

·     ↓PVR = ↓mPAP

·     ↓HR

Support the RV:

·     ↑Preload

·     ↓Afterload

·     ↑Contractility

·     Sinus rhythm

Clinical goals

Avoid the following:

 

CVS:

·     Hypotension

·     Tachycardia

Resp:

·     Hypoxaemia

·     Hypercapnoea

Metabolic:

·     Acidosis

·     Hypothermia

In practice

·     Fluid

·     Noradrenaline

·     Opioid

·     Relaxant

·     IPPV

·     Bair hugger

 

Anaesthesia application:

Anaesthetic

·     Relaxant GA

Airway

·     Default: ETT + IPPV

·     Alternative: 2nd generation LMA + IPPV

·     Beware sedation without airway device

Access

·     Big IV + pump set

·     Arterial line

·     ±CVCs

Monitoring

·     Sat probe

·     5 lead ECG

·     Arterial line

·     ±CVP

·     Core temperature

Drugs

·     Fluid bolus

·     Metaraminol vs noradrenaline

·     Fentanyl 5mcg/kg

·     Propofol 0.5-1mg/kg

 

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