• Pulmonary hypertension (PH) is defined as a mean pulmonary artery pressure > 25 mm Hg. Pulmonary artery hypertension is also defined as pulmonary vascular resistance (PVR) > 3 Wood units (240 dynes s/cm⁵) (1). It can result from chronic disturbances or diseases in pulmonary venous and arterial pressures, cardiac output, or left atrial pressures.
  • Primary PH: Due to intrinsic pathology of reactive pulmonary vasculature.
  • Secondary PH: As a result of some other primary pathology of lung, heart, or systemic diseases.
• The pulmonary vasculature is often responsive to hypoxia, hypercarbia, acidosis, and noxious stimuli such as airway instrumentation or suctioning; in PH, it may be hyperreactive. Increased pulmonary artery pressures can result in RV dysfunction, ischemia, and failure, as well as systemic hypotension, and cardiac arrest.

See classifications

• Resistance = pressure/flow (1)
  • Therefore, PVR = (PAP - LAP)/CO
  • Alternatively, PAP = LAP + (CO * PVR), where PVR is pulmonary vascular resistance, PAP is pulmonary artery pressure, LAP is left atrial pressure, CO is cardiac output
• Depending upon the etiology, PH may result from a rise in the left atrial pressure, right heart blood flow, pulmonary vascular resistance, or a mix of these conditions.
• Increased left atrial pressure (as may be seen with left ventricular failure, long-standing mitral stenosis, or severe mitral regurgitation) increases the "afterload" of the pulmonary vasculature.
• Increased right heart blood flow, from "shunting" or "mixing" cardiac lesions (atrial septal defect, ventricular septal defect) increases flow through the pulmonary vasculature with a resultant increase in pulmonary pressure.
• Increased PVR or pulmonary arterial hypertension (PAH) can result from vasoconstriction, cellular proliferation, thrombosis, and apoptosis in pulmonary arteries. At a molecular level, this is often mediated by nitric oxide, endothelin, prostacyclin, serotonin pathways, or genetic constitution like BMPR2, ALK-1, or 5-HTT mutations.
• With time, PH results in right ventricular hypertrophy or dilation, followed by dysfunction or failure due to:
  • High RV afterload
  • RV ischemia from hypoperfusion during systole (normally RV perfusion happens both in systole and diastole) due to elevated PA pressure
  • Systemic hypotension from interventricular septal shifting of the dilated RV that leads to restricted LV filling

• The anaesthetist needs to be aware of the underlying pathophysiology and severity of the disease, as well as assess if the patient is currently optimized. The RV status should be determined and the use of pulmonary vasodilators may be necessary.
• Perioperative goals include avoidance of hypoxia, hypercarbia, coughing, and bucking during induction or emergence; in addition, appropriate volume status, cardiac output, and systemic BP need to be maintained.
• In PH, TPG = mPAP – PCWP; where TPG is transpulmonary gradient, mPAP is mean pulmonary artery pressure, and PCWP is pulmonary capillary wedge pressure. If the TPG >12 mm Hg, PH may be due to high PVR; if the TPG <12 mm Hg, PH may be due to left heart failure.

• Fatigue, weakness
• Dyspnea
• Angina can result from an imbalance in oxygen supply and demand

• Supplemental oxygen
• Medication pump installed to continuously deliver pulmonary vasodilators
• Lung transplantation (or awaiting one)

• Anticoagulation: Perioperative management should be discussed with the surgeon and primary physician. In addition, it may preclude neuraxial anesthesia.
• Diuretics can affect electrolytes and volume status
• Contraception: Severe PH is considered unsafe for labor and delivery.
• Calcium channel blockers provide systemic and pulmonary vasodilation; may be useful in reversible PH
• Phosphodiesterase inhibitors (PDE-5i)
• Endothelial receptor antagonist (ETRA)

• Liver dysfunction
• Left heart disease
• Arrhythmias from dilated chambers

Acute RV ischemia, dysfunction, or failure

• World Health Organization classification of PH (Venice, 2003) (2):
  • (I) Pulmonary hypertension: Idiopathic, familial, associated with diseases (congenital heart disease, collagen vascular disease, portal hypertension, HIV, drugs, toxins)
  • (II) PH secondary to left heart disease: Left-sided hypertension or ventricular heart disease.
  • (III) PH secondary to lung disease with or without hypoxemia: Interstitial lung disease, chronic obstructive pulmonary disease, sleep-disorders, alveolar hypoventilation disease, chronic exposure to altitude
  • (IV) PH secondary to thrombotic or embolic disease: Thromboembolic obstruction of the proximal or distal pulmonary arteries
  • (V) Miscellaneous: Sarcoidosis, histiocytosis X

• Bedside telemetry at a minimum is usually needed.
• ICU/HDU care may be necessary in severe disease, intraoperative events, inotropic support, or pulmonary vasodilator treatment.

• Pulmonary and/or cardiology consult; consider having a discussion with the patient's specialist who is managing their disease prior to the procedure to discuss any recommendations and establish good follow-up.
• Inhaled vasodilators (nitric oxide or prostacyclin)

• Obstructive Sleep Apnea

• 416.0 Primary pulmonary hypertension
• 416.8 Other chronic pulmonary heart diseases

• I27.0 Primary pulmonary hypertension
• I27.2 Other secondary pulmonary hypertension

Nirvik Pal , MD

Anand Lakshminarasimhachar , MBBS, FRCA