THE PATIENT WITH PULMONARY HYPERTENSION

ANAESTHESIA FOR THE PATIENT WITH
PULMONARY HYPERTENSION
ANAESTHESIA TUTORIAL OF THE WEEK 228

JUNE 2011
Dr Sarah Thomas, Senior Anaesthetic Registrar
Royal Hobart Hospital
Correspondence to sarah.thomas@dhhs.tas.gov.au
QUESTIONS
Before continuing, consider the following scenario and question.  The answers can be found at the end
of the article, together with an explanation.
You are to anaesthetise a 65-year-old woman for laparoscopic sigmoid colectomy.  She has recently
been diagnosed with colorectal carcinoma.  The patient has been a heavy smoker in the past and has
severe chronic obstructive pulmonary disease (COPD), with secondary pulmonary hypertension.  She
also has essential hypertension.  Medications include a beta-blocker, ACE inhibitor, inhaled
steroid/beta-agonist and aspirin.
What are your concerns in anaesthetising this patient?
INTRODUCTION
The disease spectrum of Pulmonary Hypertension (PH) has received greater interest in the past decade,
as specific therapies have been developed and survival has improved.  More patients with PH are now
presenting for surgery, and this poses a challenge to the anaesthetist.  Knowledge of the underlying
physiology is paramount in preventing the feared complication of right heart failure.
DEFINITION AND CLASSIFICATION
Pulmonary Hypertension is defined as a mean pulmonary artery pressure (PAP) >25mmHg at rest with
a pulmonary capillary wedge pressure <12mmHg.   Pulmonary hypertension is considered moderately
severe when mean  PAP >35mmHg.  Right ventricular failure is unusual unless mean PAP is
>50mmHg.
The World Health Organisation classifies pulmonary hypertension by aetiology into five groups. The
disease, including its classification, was comprehensively reviewed at the 4
th World Symposium on
Pulmonary Hypertension in 2008.
Table 1: Clinical classification of pulmonary hypertension
1 Pulmonary Hypertension (PAH)
2 Pulmonary hypertension owing to left heart disease
3 Pulmonary Hypertension owing to lung disease
4 Chronic thromboembolic pulmonary hypertension (CTEPH)
5 Pulmonary hypertension with unclear multifactorial mechanisms
Group 1 includes the disease idiopathic pulmonary hypertension (formerly known as primary
pulmonary hypertension), as well as PH associated with connective tissue disorders. This group of
diseases share similar pathological findings and clinical appearance.  The incidence of idiopathic PH is
higher than previously thought, although remains relatively rare at 15 per million.
Of greater interest to the anaesthetist are the more common forms of PH: those due to left heart disease
(group 2) and those due to lung disease (group 3).  Cardiac anaesthetists have long been familiar with
PH due to left heart disease,  which often occurs  in patients undergoing cardiac surgery.  Examples
would include patients with mitral valve disease undergoing valve replacement, or patients with severe
LV failure undergoing coronary bypass surgery.
Non-cardiac anaesthetists are more likely to encounter PH in patients with lung disease.  Underlying
diseases include COAD, interstitial lung disease, and sleep disordered breathing.  The majority of
patients in this group have modest PH.
PITFALLS IN DIAGNOSIS
Pulmonary hypertension may be suspected after  patient  assessment  based on history, examination,
ECG and chest x-ray.  The symptoms of PH are non-specific, and diagnosis can be delayed.
If PH is suspected, transoesophageal echocardiography (TTE) is usually the first investigation
undertaken.  TTE utilizes Doppler across a tricuspid regurgitant jet, to estimate pulmonary artery
pressure.  This technique has been shown to under or over estimate PAP in up to half of patients at risk
of PH, and therefore as a diagnostic test has limitations in accuracy.
Right heart catheterization is required to confirm the diagnosis.  A vasodilator challenge forms part of
this assessment.



UNDERSTANDING THE PHYSIOLOGY
Providing anaesthesia to patients with PH poses some challenges.  An underlying knowledge
of the cardiovascular pathophysiology is paramount to providing safe anaesthesia in these
patients.
Right ventricular output is dependent on preload, afterload, contractility and heart rate.
Consideration must be given to optimizing each of these parameters.
Raised pulmonary vascular resistance (PVR) places an additional pressure load on the right
ventricle.  The right heart is poorly designed to deal with these increases in afterload.  A rise
in PVR and hence right ventricular afterload can put the right heart into failure.  Left
ventricular failure can then ensue, due to both reduced volume reaching the left heart, and
septal interdependence.
Factors which can raise PVR include hypoxia, hypercarbia, hypothermia, acidaemia, and
pain.  Anaesthetic technique is aimed at preventing these occurrences.
The coronary circulation to the right heart is dependent on perfusion pressure at the aortic
root, which in turn is dependent on cardiac output and systemic  vascular resistance (SVR).
SVR must be aggressively defended in order to maintain coronary perfusion to the right heart.
Ischaemia to the right ventricle can put in place a downward spiral of right heart failure, with
ensuing cardiovascular collapse.
ANAESTHETIC TECHNIQUES
Many anaesthetic techniques have been employed in anaesthetising patients with pulmonary
hypertension.  The actual technique chosen is probably less important than the manner in
which it is executed.
Extended monitoring will be useful.  Invasive blood pressure monitoring is ideal as it will aid
early and aggressive treatment of systemic hypotension.  A pulmonary artery catheter can be
useful in monitoring trends in PAP.  A rising PAP may indicate a rising PVR or a failing  right
ventricle (RV). Transoesophageal echocardiography or other cardiac output monitors can
also be useful.
An effort to obtund the response to laryngoscopy should be made.
A variety of anaesthetic induction drugs have been safely employed in patients with PH.  One
technique would be to use a combination of midazolam and fentanyl.  Etomidate has been
described as an ideal agent in PH.  Propofol and thiopentone have also been used without
problems.  Concern has been raised that ketamine may raise PVR, however it too has been
utilized safely in humans with PH.
Non-depolarising and depolarising muscle relaxants can be used safely, and  should be
chosen based on airway management issues.
A balanced anaesthetic of volatile agent and opioids can be used as maintenance.  All of the
commonly used modern volatile agents have been safely used in PH, and there is no
evidence to recommend one over the other.  Nitrous oxide should be used with caution as it
may raise PVR.
A systemic vasoconstrictor such as  phenylephrine, noradrenaline or metaraminol should be
on hand to treat reductions in systemic blood pressure.  A carefully titrated infusion may be
commenced at induction.
Inotropes can be employed to improve right heart contractility but they are often more
beneficial to the left heart  than the right heart.  The inodilators such as milrinone and
dobutamine will cause systemic vasodilation and hence reduce coronary perfusion pressure,
which limits their utility.
RV failure and raised PVR can be targeted with inhaled selective pulmonary vasodilators.
Agents such as nitric oxide and prostacyclin are increasingly being employed perioperatively
in these patients.
Neuraxial anaesthesia and analgesia, can be used safely in PH, however the anaesthetist
must be vigilant about the cardiovascular consequences of sympathetic blockade.  There are
no alpha-1 adrenoreceptors in the pulmonary circulation, hence it is unlikely that neuraxial
blockade has a direct effect on PVR.  Systemic vasodilation however, will reduce aortic
coronary perfusion pressure, as well as venous return to the right heart.  A decrease in right
atrial filling can reduce stretch on atrial receptors, resulting in reflex bradycardia.  Loss of the
cardio-accelerator fibres at T1-T4 may result in bradycardia and loss of inotropy. Bradycardia
and hypotension can cause right heart failure and can be lethal in patients with PH.
SUMMARY OF ANAESTHETIC TECHNIQUES IN PH
Avoid any stimulus which can increase PVR including: nitrous oxide, adrenaline, dopamine,
protamine, serotonin, thromboxane A2, prostaglandins such as PGF2alpha and PGE2,
hypoxia, hypercarbia, acidosis, PEEP and lung hyperinflation, cold, anxiety and stress.
If PVR is increased it can be reduced by: hypocarbia (via hyperventilation), nitric oxide,
morphine, glyceryl trinitrate, sodium nitroprusside, tolazoline, prostacycline (PGI2),
isoprenaline, and aminophylline.
Aims are to avoid marked decreases in venous return (correct blood and fluid loss quickly),
avoid marked decreases in SVR, avoid drugs which cause myocardial depression, and to
maintain a normal heart rate
A feared complication of pulmonary hypertension is right
heart failure
Understanding the physiology of right ventricular function
and coronary perfusion are important when anaesthetising
patients with pulmonary hypertension
Anaesthetic aims in PH are to avoid increased PVR, to
avoid marked decreases in venous return or SVR, to avoid
myocardial depression and to maintain normal heart rate.
SUMMARY
ANSWERS TO QUESTIONS
Your concerns in anaesthetising this patient may include:
1. The presence of severe systemic disease in a patient undergoing intermediate risk surgery.
Optimisation of the patient’s chronic obstructive pulmonary disease and pulmonary
hypertension is warranted pre-operatively.
2. The cardiovascular and respiratory sequelae of pneumoperitoneum, trendelenburg position,
and potentially prolonged surgery.
3. Anticipation and prevention of perioperative right heart failure in the patient with pulmonary
hypertension.
4. Provision of excellent perioperative pain relief, especially in the patients with lung disease, to
reduce the risk of respiratory complications.
REFERENCES and FURTHER READING
Pritts CD and Pearl RG.  Anaesthesia for patients with pulmonary hypertension.   Current Opinion in
Anaesthesiology 2010, 23:411-416
Mehta S and Little S.  Editorial:  Screening for Pulmonary Hypertension in Scleroderma.   Journal of
Rheumatology 2006; 33:2 204-206
Manecke GR.  Anaesthesia for pulmonary endarterectomy.  Semin cardiovasc thorac surgery 18: 236-
242
Slinger PD.  Anaesthetic planning for the patient with co-existent disease: the patient with lung disease.
New York Society of Anesthesiologists, 64th
Annual PGA. Scientific Panel December 2010