Critical Care Medicine-Neurologic Disorders>>>>>Shock States
Question 9#

A 40-year-old woman with idiopathic pulmonary arterial hypertension on continuous treprostinil has worsening shortness of breath and weight gain of 8 kg in the setting of nonadherence to her home diuretic regimen. On evaluation in the emergency department, she is found to have:

• T 37°C
• BP 90/62 mm Hg
• HR 126 beats per minute
• respiratory rate 40 breaths per minute
• SpO₂ 74% that improves to 84% on high-flow nasal cannula at 60 L/min and FiO₂ 0.6

While undergoing other workup, the patient’s respiratory status worsens and the decision is made to intubate her.

Which of the following is most accurate regarding her physiology?

A. She should receive an IV fluid bolus before induction to maintain preload
B. Vasopressin may help preserve right ventricular systolic function during intubation
C. She should receive high minute ventilation with a high positive end-expiratory pressure to maintain her oxygenation during intubation
D. There is evidence that norepinephrine is the best medication for hemodynamic support in this situation
E. Propofol is the preferred agent for induction in this patient

Correct Answer is B

Comment:

Correct Answer: B

Patients with right heart failure and cardiogenic shock have very tenuous hemodynamics, and intubation presents a uniquely dangerous challenge in this patient population. The combination of induction medications and mechanical ventilation with increased intrathoracic pressures acutely decreases preload to the right ventricle and can increase afterload via an increase in pulmonary vascular resistance with overdistention of the lungs. In addition to avoiding intubation whenever possible, strategies can be undertaken to minimize risk if intubation is unavoidable. Vasopressor support is recommended, and both neosynephrine and vasopressin can preserve right ventricular systolic function by preserving cardiac preload in the setting of vasodilatory induction drugs and by preserving perfusion to the right ventricle and preventing worsening ischemia (answer B is correct). Norepinephrine provides additional inotropic support and is commonly used but there is no high-quality evidence that shows that norepinephrine is superior to other agents (answer D is incorrect). 

Although hypercarbia is poorly tolerated, aggressive ventilation with high tidal volumes, high respiratory rate, and high positive end-expiratory pressures can worsen right ventricular afterload by increasing pulmonary vascular resistance, which is lung volume dependent (answer C is incorrect). Propofol is vasodilatory, therefore decreasing preload, and has a potential negative inotropic effect and for those reasons is not a preferred agent in this setting (answer E is incorrect). Etomidate is often recommended, given its smaller effect on hemodynamics. Although an acute decrease in preload is a concern, this patient is already volume overloaded and additional IV fluids are not recommended (answer A is incorrect). 

References:

1. Price LC, Wort SJ, Finney SJ, et al. Pulmonary vascular and right ventricular dysfunction in adult critical care: current and emerging options for management: a systematic literature review. Crit Care. 2010;14(5):R169.
2. Maxwell BG, Pearl RG, Kudelko KT, et al. Case 7-2012 airway management and perioperative decision making in the patient with severe pulmonary hypertension who requires emergency noncardiac surgery. J Cardiothorac Vasc Anesth. 2012;26(5):940-944.
3. Green EM, Givertz MM. Management of acute right ventricular failure in the intensive care unit. Curr Heart Fail Rep. 2012;9(3):228-235.