June 1, 2017

Episode #58 Push Dose Pressors & Push Dose Nitroglycerin @emscritcare #EMSWeek2017

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https://emcrit.org/wp-content/uploads/push-dose-pressors.pdf 

Resuscitation – beginning from initial patient contact to the emergency department to the intensive care unit is a continuun of care – though the first few minutes of patient contact with a critically ill patient can have tremendous repercussions on the patient’s ultimate outcome.  Whether in critical care transport or in 911 emergency response, patient’s may require a medication in small aliquots immediately that would be either unfeasible or cumbersome to administer via infusion on a dedicated pump.

While circumstances in which a patient needs a push dose medication may be uncommon, the administration of these drugs can be potentially lifesaving.  There are two prehospital scenarios in which the paramedic carries the necessary medication in their armamentariam and with appropriate instruction and training can safely reconstitute into an appropriate dose for use in out-of-hospital resuscitation for the critically ill patient.

Push dose pressors are often employed in profoundly hypotensive patients that will require endotracheal intubation.  Rapid Sequence Intubation and Positive Pressure Ventilation are both associated with hypotension, thus in the patient that requires advanced airway and is hypotensive upon EMS arrival, push dose pressors may be employed to effectively “resuscitate before you intubate”.  Typically Epinephrine is diluted to an appropriate dose and adminstered in small aliquots (10mcg/ml) for inotropoic support to optimize hemodynamics prior to RSI or intubation.  There is also anaesthesia literature supporting the use of neosynephrine as well as phenylephrine for this purpose, though these medications are less readily available prehospitally.  Even brief episodes of relative hypotension can cause effects seen days later; in critically hypotensive patients these may be even more pronounced.  By using push dose pressors, a field provider can safely and effectively resuscitate their patient in order to mitigate the risks associated with endotracheal intubation prior to securing an advance airway.

Conversely, a separate and distinct class of patients who suffer from decompensated heart failure may present with respiratory distress due to volume overload with pathophysiology associated with marked systemic hypertension. While CPAP is the mainstay of therapy for these patients prehospitally and has significantly reduced intubation of the CHF patient over the past several years, IV Lasix and topical Nitroglycerin play little role in the EMS management of the decompensated heart failure patient.  Nevertheless, these patients often require preload and afterload reduction to manage their symptomatology; it is common to initiate nitroglycerin infusions in critical care transport as well as in the emergency department for management of this hypertension.

Nitroglycerin lowers preload via venous vasodilation at low doses and lowers after load via arterial vasodilation at higher doses, making the patient’s vascular container larger lowering the systemic pressure. Aggressive, high dose NTG paired with the recruitment of the alveoli using CPAP & PEEP make up the mainstay of pre-hospital treatment of APE and decompensated heart failure. Bolus doses as high as 2 mg (2000 mcg) of nitroglycerin have been given safely and effectively in previous studies.

In emergent resuscitations we need to focus on bolus dose medications in the acute phase versus starting and titrating critical care infusions while a patient is in extremis. The goal is to achieve clinical end points of treatment faster with bolus dosing at the bedside and then begin maintenance infusions once resuscitation goals are met and the hemodynamics are stable.  Similar to push dose pressors in the acutely hypotensive EMS patient requiring resuscitation, patients with decompensated heart failure may benefit acutely with push dose nitroglycerin, a potent vasodilator.

 

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