Pulmonary Arterial Hypertension

1
Pulmonary Arterial Hypertension

• Dr. Amy Rodgers
• PGY-4 Anesthesia
• Aug. 10, 2007

2
Definition

• Progressive increase in mean pulm arterial
  pressure (PAP) gt25mmHg at rest or 30mmHg during
  exercise

3
Pathophysiology

• Acute ? RV afterload, ? EDV, ? EF, ?SV of RV
• Chronic progressive systolic pressure overload
  of RV that dilates and hypertrophies, gradual RV
  dysfunction
• ?venous return compromises RV preload and pulm
  blood flow
• results from positive intrathoracic pressure
  (ex. PEEP) which also causes alveolar
  overdistension which ?PVR and ? pulm blood flow

4
Pathophysiology

• -?PVR limits RV SV and the volume for LV filling
• -LV compressed by intraventricular septum during
  systole, ? LV volume/filling, ?CO/BP
• -?BP leads to ?coronary perfusion which can lead
  to myocardial ischemia/R sided failure
• -coronary blood flow to RV usually occurs during
  diastole and systole but is decreased if RV
  pressures are equal to or higher than systemic
  pressures
• -hypoxemia from ?CO/?pulm blood flow or from R to
  L intracardiac shunt (if RA pressures higher than
  LA)

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Classification

• Pulmonary (pulm) arterial HTN
• Primary pulm HTN (sporadic, familial)
• Pulm arterial HTN (related to collagen vascular
  disease- scleroderma, lupus, RA)
• Congenital systemic-to-pulmonary shunts
  (Eisenmenger syndrome), portopulmonary HTN
• HIV, drugs, toxins
• Pulm HTN associated with disorders of resp system
  and/or hypoxemia
• Parenchymal lung disease (COPD, interstitial
  pulmonary fibrosis, CF)
• Chronic alveolar hypoxemia (exposure to long-term
  low oxygen tension such as in high altitudes)

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Classification

• Pulm venous HTN
• Mitral valve disease
• Chronic LV dysfunction
• Pulm venoocclusion disease
• Pulm HTN due to chronic thrombotic and/or
  embolic disease
• Thromboembolic obstruction of prox pulm arteries
• Obstruction of distal pulm arteries
• Pulm HTN due to disorders directly affecting the
  pulm vasculature
• Inflammatory
• Pulm capillary hemangiomatosis

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Etiology -Peds

• Persistent pulm htn of the newborn meconium,
  RDS, pneumonia, sepsis, severe hypoxia
• Congenital cardiac lesions L to R shunt
• Post cardiac surgery (CPB induces a pulmonary
  inflammatory response)
• Chronic lung disease (2º Pulm HTN)
• Idiopathic

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Signs of Disease Severity

• Dyspnea at rest
• Low cardiac output with metabolic acidosis
• Hypoxemia
• Signs of right heart failure (large V wave on
  jugularis vein, periph edema, hepatomegaly)
• Syncope (poor prognosis)
• Chest pain (2? to RV ischemia)

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Physical Exam

• Loud P2 (increases PAP)
• Left parasternal heave (R sided overload)
• Pulm valve regurgitation (dilatation of pulm
  valve annulus)
• S3 gallop (advanced RV failure)

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Recommended Tests before Anesthesia

• ECG RV/RA enlargement
• CXR enlarged central and R/L pulmonary arteries,
  ?cardiac silhouette
• ABG
• ECHO ? TR, ?PFO, estimation of pulm pressure, RV
  hypertrophy, dilatation of RV with impairment of
  LV filling, paradoxical mvmt of IV septum
• Cardiac Catheterization pulm pressures, CO,
  response to vasodilators, ?PFO, status of
  coronary circulation

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Anesthetic Considerations Pre-op

• Maintain all pulm vasodilators ex. prostacyclin,
  Ca2 antagonists, phosphodiesterase-5-inhibitors
  (sildenafil, dypiridamole), endothelin receptor
  antagonists (Bosentan) and O2
• If pulm HTN diagnosed immediately pre-op and OR
  cant be delayed, start sildenafil (0.1mg/kg
  daily up to 0.5mg/kg q6hrs, adults 50-100mg
  daily, IV 0.2mg/kg/hr) and l-arginine (15gm
  daily) if clinical signs of pulm HTN or poor ex
  tolerance
• Heparin should replace indirect anticoagulant
  (ie. Coumadin) until OR
• Premed slight midaz OK as long as resp
  acidosis/?BP not induced

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Anesthetic Considerations Goals

• Maintain NSR
• Avoid tachycardia
• Avoid hypotension/hypertension
• Avoid all factors that increase PVR
• Hypoxia
• Hypercarbia
• Acidosis
• Pain/noxious stimuli
• Low lung volumes/overdistension

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Anesthetic Considerations Induction

• Few studies showing effect on vasoreactivity
• Opioids used at a dose to block the cardioresp
  response of intubation, they have no direct
  effect on pulm vessels
• Lidocaine (1mg/kg) can help suppress response to
  intubation
• Propofol, pentothal or etomidate may be used
• Depolarizing or nondepolarizing muscle relaxants
  could be used (avoid MR releasing histamine)

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Anesthetic Considerations Maintenance

• Volatiles (iso-most common, des, sevo) can be
  used
• Desflurane
• Potentiates pulm vasoconstriction to adrenoceptor
  activation
• Isoflurane
• Attenuates magnitude of hypoxic pulm
  vasoconstriction
• Potentiates vasodilator response to B1
  adrenoceptor activation
• No effect on alpha 1 vasoconstriction
• Maintain opioids at a surgical analgesic level
• Maintain muscle relaxation

15
Monitoring

• Art line
• CVP or PAC
• TEE if available

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Treatment of Pulm HTN During Surgery

• Inhaled NO (20-40 ppm)
• Milrinone (50ug/kg bolus then 0.5-0.75ug/kg/min)
• Dypiridamole (0.2-0.6 mg/kg IV over 15min q
  12hrs)
• Inhaled prostacyclin (nebulized or IV 2-20
  mcg/kg/min)
• Mg smooth muscle relaxant, attenuates the effect
  of hypoxia on PVR (serum conc 3-5mmol/L)

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Nitric Oxide

• Selective pulmonary vasodilation, improves
  oxygenation
• ? cGMP
• Used in ARDS, PPHN, cardiogenic shock, post CPB
• Risks methemoglobinemia and carboxyhemoglobinemia
  , rebound pulm HTN when stopped
• Requires closed inhalational circuit

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Phosphodiesterase inhibitors

• Inhibition of nitric oxide degradation
• Sildenafil (PDE-5 inhibitor) ? PAP/PVR
• Min effects on systemic vasculature
• Synergistic with NO
• Reduction in RV mass role in prevention or
  reversal of remodeling of RV
• Milrinone (PDE-3 inhibitor) ? PVR/PAP/SVR in
  setting of CV shock
• Nebulized minimizes systemic vasodilation

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Prostacyclins

• Potent pulm and systemic vasodilators with
  antiplatelet properties
• Epoprostenol (IV) ? PVR, better CO/ex. Tolerance
• s/e ?BP, need for central line (risk of
  infection)
• Beraprost (PO) Longer duration
• Iloprost (nebulized)

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Endothelin receptor antagonists

• Endothelin-1 neurohormone that causes pulm
  vasoconstriction, smooth muscle proliferation,
  fibrosis
• Stimulates endothelin receptors A B
• A vasconstriction
• B vasodilation
• Nonselective Bosentan
• A selective sitaxsentan, ambrisentan
• Chronic pulm htn tx given long ½ life and no IV
  preparation
• s/e hepatic toxicity

21
Ca channel blockers

• Chronic pulm HTN Rx
• s/e hypotension causing reflex tachycardia
• Only 15-25 of pts respond
• Need to undergo vasoreactivity testing prior to
  starting

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Post-op

• ICU
• Optimal analgesia with continuous epidural,
  regional block or parenteral opioids
• Avoid, hypoxemia, ?BP, hypovolemia
• Risk of acute pulm vasospasm, PE, arrhythmia,
  fluid shifts, ? sympathetic tone, ? pulm vasc
  tone
• Wean any pulmonary vasodilators progressively

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Periop Complications in Children with Pulm HTN
undergoing Noncardiac Surgery or Cardiac Cath

• ? complication in pts with systemic (PAP 70-100
  of systemic BP) or suprasystemic (PAP gt100
  systemic BP)
• Major complications more frequent during cardiac
  cath 3/141 cardiac arrests, 2/141 deaths
  associated with pulm THN crises
• No association with age, etiology of PAH, type of
  anesthetic, or airway mngt technique

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Pulm HTN Crises

• Rapid ? in PVR where PAP gt syst BP
• R heart failure ??PBF, ? CO, hypoxia and
  Biventricular failure
• Rx 100 O2, hyperventilation, attenuation of
  noxious stimuli, pulm vasodilators

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Obstetric Anesthesia

• Epidurals used successfully
• Risk of ? venous return/BP from sympathetic
  blockade
• Keep BP within 15 of baseline and below basal
  level
• Systemic pressure should always be higher than
  pulm pressure
• Use a low concentration of LA/opioids to reduce
  drop in BP

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C-section

• Uterine contraction large bolus of blood to
  circulation may be poorly tolerated if severe
  pulm HTN or MS
• Vasodilators eg. NTG
• Diuretics

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References

• Carmonsino, MJ et al. Perioperative Complications
  in Children with Pulmonary Hypertension
  Undergoing Noncardiac Surgery or Cardiac
  Catheterization. Anesthe Analg 2007 104 512-7.
• Haj RM et al. Treatment of Pulmonary
  Hypertension with selective pulmonary
  vasodilators
• Petros AJ. The Management of Pulmonary
  Hypertension. Pediatric Anesthesia 2006 16
  816-821.
• Warltier, DC et al. Pulmonary Arterial
  Hypertension Pathophysiology and Anesthetic
  Approach. Anesthesiology 2003 99 1415-32.