Pulmonary hypertension and right ventricular failure

Case

A 40 year old female presents by EMS with significant dyspnea. She has had a fever and cough for 2 days, and has been getting progressively more short of breath. Today, she almost fainted when she stood up, so she called 911. Her vital signs are HR 135, BP 88/45, RR 35, and an oxygen saturation of 90% on a nonrebreather. She is quite somnolent. As she is being transferred to the stretcher, the paramedic mentions that she has a pump of some sort to treat her pulmonary hypertension…

Pathophysiology

It is very rare for my to write about pathophysiology, but understanding the pathophysiology of the right ventricle is essential to understanding the appropriate emergency management of these patients.

In the normal state, the pulmonary circulation is a low-pressure, low-resistance system. Pulmonary pressures are increased in response to hypoxia, hypercapnia, and acidosis. The right ventricle is thin walled and can accomodate large changes in volume, but has very limited ability to cope with increased afterload (pulmonary vascular pressures). Finally, unlike the left ventricle, the right ventricle is perfused both during systole and diastole. These features set up the potential “spiral of death” that occurs with elevated pulmonary vascular pressures.

In the setting of pulmonary hypertension, the right ventricle is impaired both mechanically and by ischemia. Increased RV pressure leads to bowing of the septum into the left ventricle, which leads to decreased LV filling and decreased cardiac output. Right ventricular stretching will cause tricuspid regurgitation, which will also result in decreased cardiac output. Any decrease in cardiac output will result in decreased perfusion to the right ventricle. Finally, increased pulmonary pressures increase the RV wall tension and induce RV hypertrophy, which decreases perfusion to the right ventricle, ultimately worsening cardiac output further. (True experts are probably cringing at this over-simplified explanation, but I think it is enough to understand the management, which is my priority.)

Therefore, we are faced with a situation in which high pulmonary pressures decrease cardiac output causing ischemia, and ischemia worsening cardiac output further: a spiral that quickly leads towards death. (Greenwood 2015)

My approach

There are 2 main priorities: (Greenwood 2015)

1. Identify and treat the underlying cause
2. Improve right ventricle (RV) function

Call for help

Both the underlying pathophysiology and the management of pulmonary hypertension and right ventricular failure are incredibly complex. Call for help from the closest pulmonary hypertension referral center as soon as possible. (Hoeper 2011)

Fix hypoxia and hypercapnia

Hypoxia and hypercapnia both result in increased pulmonary vasoconstriction and need to be addressed early. However, intubation of patients with pulmonary hypertension and right ventricular failure will frequently precipitate hemodynamic collapse and even cardiac arrest, and therefore should be avoided if at all possible. (Greenwood 2015; Mosier 2015; Wilcox 2015) Start with basic airway maneuvers. Although any positive airway pressure can worsen hemodynamics, noninvasive positive pressure ventilation is preferred as it is rapidly reversible. (Mosier 2015; Wilcox 2015)

Manage hypotension

Maintaining an appropriate systolic blood pressure is essential, because if the systolic pressure drops below the elevated pulmonary artery pressure, right ventricular ischemia occurs, worsening cardiac output, resulting in a spiral towards death.

Clinical assessment of volume status is very difficult in the setting of RV failure. (Greenwood 2015; Wilcox 2015) The right ventricle is dependant on preload for function, but most right ventricular failure will be associated with volume overload. (Wilcox 2015) A fluid bolus is reasonable in hypotensive patients when there is clinical evidence of volume depletion, but low volume boluses (250-500 ml crystalloid) and frequent clinical reassessment are essential. (Greenwood 2015) Another option would be to assess the patient’s response to a passive leg raise before giving a bolus. The fluid bolus may actually worsen hemodynamics by increasing RV stretch. Somewhat paradoxically, most patients will actually require diuresis to improve hemodynamics, because the bulging septum is a major contributor to decreased cardiac output. (Hoeper 2011) If you are unsure which way to go, err on the side of volume constriction.

Start a vasopressor early for hypotensive patients with RV failure. Norepinephrine is generally considered the first choice. (Greenwood 2015; Wilcox 2015) Vasopressin is another reasonable option, and may actually decrease pulmonary vascular resistance. (Wilcox 2015) Phenylephrine should be avoided because it increases pulmonary vascular resistance. (Wilcox 2015).

Check for a pump

Some patients with pulmonary arterial hypertension are on a continuous infusion of a pulmonary vasodilator. Abrupt discontinuation of the infusion can lead to rebound pulmonary hypertension and rapid deterioration. If the patient presents with a malfunction of their pump, the medication should be restarted immediately through a peripheral IV. (Greenwood 2015; Wilcox 2015)

Look for and manage arrhythmias

Tachydysrhythmias are particularly dangerous in the setting of pulmonary hypertension, as patients are often reliant on the atrial kick for ventricular filling and cardiac output. (Greenwood 2015; Wilcox 2015) Get an ECG early. Beta-blockers and calcium channel blockers should be avoided, as they will impair cardiac contractility and therefore worsen already impaired cardiac output. Cardioversion is the preferred approach. (Greenwood 2015; Wilcox 2015) That being said, sedation is risky because of the risks of hypotension, hypoxia, and hypercapnia, so chemical cardioversion may be a better option than electrical.

Look for and manage other precipitants

There are a number of secondary causes of pulmonary hypertension, such as COPD, left ventricular failure, pulmonary embolism, and obesity hypoventilation. These underlying causes should be identified and aggressively managed. (Wilcox 2015) Anemia can also worsen cardiac ischemia and some experts recommend transfusing to maintain a hemoglobin greater than 100 mmol/L (10 g/dL). (Greenwood 2015; Hoeper 2011)

Improve RV function

Inotropes will frequently be required for patients in whom oxygen delivery and volume overload are not adequately managed by diuresis alone. Start dobutamine at 2mcg/kg/min and titrate up to 10 mcg/kg/min. Higher doses should be avoided in the setting of RV failure. (Greenwood 2015) Dobutamine frequently causes hypotension, which can be devastating in RV failure, and so a vasopressor should always be ready when dobutamine is started. (Greenwood 2015) Milrinone is another option.

Reduce RV afterload

Remembering that hypoxia, hypercapnia, and acidosis all cause pulmonary vasoconstriction, the first priority is basic resuscitation aimed at remedying those issues. (Greenwood 2015) You have to be very careful when using sedatives and opioids, because it is essential to avoid respiratory depression. (Wilcox 2015)

There are a number of medications that are used specifically to reduce right ventricular afterload. I do not anticipate having to start one of these medications de-novo without consultation with a specialist, but if the patient is already one of these medications, it absolutely should be continued (or restarted) in the emergency department. (Greenwood 2015; Wilcox 2015)

Inhaled nitric oxide is another potent pulmonary vasodilator that may be used by facemask to try to prevent intubation. (Greenwood 2015) Phosphodiesterase inhibitors (such as sildenafil) are also used, as they potentiate the effects of nitric oxide, but aren’t used in the management of critically ill patients. (Greenwood 2015)

Final options

ECMO is an option to manage severe shock or hypoxia in patients with pulmonary hypertension, but is obviously extremely resource intensive, and should only be used as a bridge in the scenario that a definitive therapy such as transplantation is available. (Greenwood 2015)

Intubation

There is a clear consensus that every attempt should be made to avoid intubation. If intubation is necessary, awake intubation, facilitated with ketamine if necessary, is probably the preferred approach. Systemic blood pressure needs to be kept higher than the pulmonary artery pressure, which means having vasopressors ready or already running at the time of intubation. Avoiding hypoxia is essential. Airway pressure should be kept to a minimum, but hypercapnia needs to be avoided. (Greenwood 2015; Hoeper 2011; Wilcox 2015)

Notes

The management of sick pulmonary hypertension patients is distinctly lacking in evidence, and so is primarily based on expert opinion.

Pulmonary hypertension is a common cause of RV failure, but RV failure can also occur as the result of other diseases such as myocarditis or RV myocardial infarction.

Pulmonary hypertension is often missed until quite late in the disease. (Greenwood 2015) In the emergency department, it should be considered in any patient with unexplained dyspnea.

Some common ECG findings associated with pulmonary hypertension: (Greenwood 2015)

• Right-axis deviation
• Right bundle branch block
• rSR’ in V1
• qR V1
• Large inferior P waves
• ST depression or T-wave inversion inferiorly and in the V1
• RV hypertrophy

There are 5 WHO groups of pulmonary hypertension. Understanding these groups will probably help emergency physicians catch undiagnosed cases of pulmonary hypertension and better manage sick patients with pulmonary hypertension. (Wilcox 2015)

• Group 1: Primary PAH – Idiopathic, familial, drug induced
• Group 2: Caused by left sided heart disease
• Group 3: Caused by lung disease or hypoxia (CPDO, sleep apnea, obesity hypoventilation)
• Group 4: Caused by chronic thromboembolic disease (large, multiple, or recurrent PEs)
• Group 5: Miscellaneous (The least helpful category, that includes vasculitis, sarcoidosis, hemodialysis, and thyroid disorders)

Other FOAMed Resources

EMCrit 272 – Right Heart Failure with Sara Crager

EM Cases CritCases 7: Pulmonary hypertension

EMCrit 181: Pulmonary Hypertension and Right Ventricular Failure with Susan Wilcox

For a much more in depth talk: Playford on Pulmonary Hypertension on ICN

EMOttawa: Getting it ‘right’: Pulmonary hypertension in the EM

Right heart strain on 5 minute sono

References

Greenwood JC, Spangler RM. Management of Crashing Patients with Pulmonary Hypertension. Emergency medicine clinics of North America. 2015; 33(3):623-43. PMID: 26226870

Hoeper MM, Granton J. Intensive care unit management of patients with severe pulmonary hypertension and right heart failure. American journal of respiratory and critical care medicine. 2011; 184(10):1114-24. PMID: 21700906

Mosier JM, Joshi R, Hypes C, Pacheco G, Valenzuela T, Sakles JC. The Physiologically Difficult Airway. The western journal of emergency medicine. 16(7):1109-17. 2015. PMID: 26759664 [free full text]

Wilcox SR, Kabrhel C, Channick RN. Pulmonary Hypertension and Right Ventricular Failure in Emergency Medicine. Annals of emergency medicine. 2015; 66(6):619-28. PMID: 26342901