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)

Group 2

·         Left heart disease

Group 3

·         Chronic hypoxic lung disease

Group 4

·         Chronic venous thromboembolism

Group 5

·         Unclear

 

Diagnosis:

Pre-capillary

i.e. not left heart

·         mPAP >20

·         PCWP <15

Post-capillary

i.e. left heart

·         mPAP >20

·         PCWP <15

·         PVR <3

·         TPG <12?

·         DPG <7

Both

·         mPAP >20

·         PCWP <15

·         PVR >3

·         TPG >12?

·         DPG >7

Considerations

Note mPAP is affected by:

·         Volume status

·         Cardiac output

 

Severity:

NYHA

1.    No limitation

2.    SOB with decent activity

3.    SOB with minimal activity

4.    SOB at rest

mPAP

·      Mild: 20-40

·      Moderate: 40-55

·      Severe: >55

 

Modification:

Physical

·      Minimise IPPV

·      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

·      Nitrous oxide

 

Anaesthesia goals:

Physiological

Avoid RV ischaemia:

·      Maximise P1 (SVR hence mAP)

·      Minimise P2 (PVR hence mPAP – see above)

·      Maintain perfusion time (HR)

Avoid RV failure:

·      Maintain preload

·      Minimise afterload (PVR – see above)

·      Maintain contractility

·      Maintain sinus rhythm

Clinical

Cardiovascular: avoid…

·      Hypotension – i.e. crystalloid + noradrenaline + careful induction

·      Tachycardia – i.e. generous opioid

Respiratory: avoid…

·      Hypoxia – i.e. ↑FiO2, minimise apnoea

·      Hypercapnoea – i.e. rock

·      Positive pressure ventilation – i.e. hard place

Metabolic:

·      Acidosis – i.e. controlled ventilation + adequate mAP

·      Hypothermia – i.e. forced air warmer pre-op and intra-op

 

Anaesthesia application:

Airway

·      Default: ETT + IPPV

·      Alternative: 2nd generation LMA + IPPV

·      Beware sedation without airway device

Access

·      Big IV + pump set

·      Arterial line

·      ±CVCs

·      ±PAC

Monitoring

·      Sat probe

·      5 lead ECG

·      Arterial line

·      ±CVP

·      ±mPAP

·      Core temperature

Drugs

Induction:

·      Propofol 0.5-1mg/kg

·      Fentanyl 5-7mcg/kg

·      Rocuronium 1.2mg/kgs

Vasoactives:

·      Noradrenaline ideal:

o  ↑Contractility

o  ↑Coronary perfusion pressure

 

Feedback welcome at ketaminenightmares@gmail.com