Pulmonary Hypertension

Elevated mean PAP ⩾20mmHg; and is classified by both:

Epidemiology and Risk Factors

Pathophysiology

Mostly notes from Hastings lecture that need to be classified better

Change in mPAP can be due to:

  • ↑ RV CO
  • ↑ PVR
  • ↑ LAP

PASP in one metric to assess severity of disease. Key other metrics:

  • CVP
  • RV systolic function

Classifications:

  • Pre-capillary
    • PAH
      • Small derangements have large implications
    • lung disease
    • CTEPH
    • Weird stuff
  • Post-capillary
    • LV
      • HFpEF
      • HFrEF
      • MV disease
  • Mixed
    • LV failure

Assessment:

  • Where is the primary pathology
  • What are the consequences
    • What is the PA pressure?
      Less important compared to functional severity and stability.

Hypoxia primarily due to impaired diffusion capacity Other cause is intracardiac shunting (reopening of FO)

Aetiology

Clinical Manifestations

Symptoms often present for up to two years prior to diagnosis

Non specific cardiac and respiratory features:

  • Exertional dyspnoea
  • Fatigue
  • Hoarseness
    From recurrent laryngeal nerve stretch.
  • RV dysfunction
    • Exertional chest pain
    • Exertional syncope
      Rare and late.
    • Fluid overload
    • Anorexia
    • Hepatic congestion
      • Abdominal pain
      • Ascites

Examination:

  • Loud S2
  • Elevated JVP
  • Hepatomegaly
  • Pulsatile liver
  • Ascites
  • Peripheral oedema

Diagnostic Approach and DDx

Investigations

Six minute walk test:

  • Desaturation of >10% or distance <350m is significant of perioperative morbidity

Right heart catheterisation:

  • Diagnostic
  • Of greater utility in type 1 and type 2
  • Sometimes required to determine treatment eligibility

Echocardiography:

  • Evaluate for signs and degree of PAH
    • RVSP
    • RV overload
      • Flattening of IV septum
  • Evaluate for signs of LV dysfunction as cause
    • Enlarged LA
    • LVH
    • Raised E/e’
  • Evaluate for valvular disease as cause
    • Mitral valve
    • Aortic valve

Imaging:

  • V/Q scan
    Assess for pulmonary obstruction, as present in CTEPH.
  • HRCT
    Assess for presence of primary respiratory disease.

Management

Management options depend on aetiology

Principles of management:

  • Initial medical monotherapy for patients with mild-moderate disease
  • Prostanoid may be added as a third line agent
  • Consider prostacyclins as first line in severe disease

Acute Management

Principles:

  • Treat any precipitating factors
    • Arrhythmia
      Restore sinus rhythm.
    • Sepsis
    • Anaemia
    • Thrombus
  • Optimise RV preload
    Poor tolerance to change in loading conditions.
    • Diuretics
    • Fluid
  • Reduce RV afterload
    • Inodilators
      Milrinone.
    • Prostainoid
    • Nitric oxide
  • Maintain RV perfusion pressure
    • Vasopressors
      • Noradrenaline generally accepted as first line
      • Vasopressin useful for patients resistant to noradrenaline
  • Improve RV contractility
    • Inodilators
    • Inotropes
  • ECMO

Medical Management

Pulmonary vasodilators:

  • Prostacyclins
    ↑ dose as tolerated to prevent systemic hypertension.
    • Epoprostenol
      • Reduces mortality
      • Administered by continued infusion
        Requires long-term central access.
      • Temperature sensitive
    • Iloprost
      • Longer duration of action than epoprostenol
      • May be nebulised Q4H or given by continued infusion
  • Endothelin receptor antagonists
    Type 1 only.
    • Bosentan
    • Ambrisentan
    • Macitentan
  • Phosphodiesterase inhibitors
    • Sildenafil
    • Tadalafil
  • Nitric oxide

Surgical Management

Pulmonary endarterectomy:

  • May be performed for CTEPH
  • Very few centres capable
  • Perioperative mortality ~5%

Transplantation:

  • Lung transplantation
  • Heart transplantation
  • Heart-lung transplantation

Anaesthetic Considerations

↑ perioperative morbidity and mortality.

Consider the package:

  • High risk
    • Group I
    • sPAP >70/PVR >3 Wood units
    • WHO III/IV
    • Major surgery
    • Long operations
    • Emergency surgery
  • C
    • Preoperative medication optimisation
    • 5-lead ECG
    • Arterial line
    • Consider CVC/PAC TOE
    • Have pulmonary vasodilators available
      • NO available
    • Potential acute RV dysfunction
      • May lead to haemodynamic collapse
        The spiral of death.
      • Optimise PVR by avoiding:
        • Hypoxia
        • Hypercarbia
        • Acidosis
        • Hypothermia
        • Sympathetic stimulation
          Pain.
        • RV overload
          Use appropriate PEEP; usually 5-8cmH2O.
      • Optimise preload
        Narrow range of preload tolerance.
        • Cautious fluid use
        • Diuretics
      • Defend RV perfusion
      • Maintain sinus rhythm
      • Optimise rate
        High-normal.
    • Haemodynamic goals
      • Avoid ↑ PVR
        • Hypoxia
        • Hypercapnoea
        • Acidosis
        • Cautious PEEP
        • Positioning
        • Be careful of pneumoperitoneum
      • Vasopressor
        • Vasopressin
          Allegedly will not ↑ PVR.
        • Noradrenaline
      • Inotropes
        • Dobutamine
        • Milrinone
      • Inhaled pulmonary vasodilators
        • iNO

Marginal and Ineffective Therapies

Complications

Prognosis

Death:

  • 50% of patients requiring CRRT will die in hospital

Key Studies

References

  1. Condliffe R, Kiely DG. Critical care management of pulmonary hypertension. BJA Educ. 2017;17(7):228-234. doi:10.1093/bjaed/mkw074