UMEM Educational Pearls - By Mark Sutherland

It's important to remember the differential for the patient with Ventricular Assist Device (VAD) difficulties, as these patients are likely to show up in your ED. 

1) Assess the patient as you usually would (signs of life, mental status, breathing, arrhythmias on monitor, etc). Listen for a hum over the chest.  Don't expect to feel a pulse.

2) Look at the VAD including controller, driveline, and power source for alarms, disconnections, signs of infection, and other obvious issues.

3) Look at the power (displayed flow), pulsatility index, and pump speed on the controller to help determine the cause of the issue (see attached chart).  Once you have a suspected etiology, typical management of these issues is usually similar to non-VAD patients (i.e. gentle IVF for hypovolemia, vasodilators if low flow is due to afterload/hypertension, defibrillation/CPR for arresting pts, etc).

Don't forget to call your VAD coordinator when able.  Consider a-line placement for precise evaluation of blood pressure (focus on MAP).

Bottom Line: Consider obstruction/thrombosis, bleeding, infection, hypovolemia, afterload/hypertension, arrhythmia, worsening LV function, and suction events when troubleshooting VADs.  The power, pulsatility index, and pump speed help differentiate these conditions.

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Attachments

VAD_Differential.jpg (134 Kb)

With increasing critical care boarding and the opioid crisis leading to more intubations for overdose, extubation - which was once a very rare event in the ED - is taking place downstairs more often.  Prolonged mechanical ventilation is associated with a ton of complications, so it's important for the ED physician to be comfortable assessing extubation readiness.  There is no single accepted set of criteria, but most commonly used are some variant of the following:

• Reason for intubation (e.g. overdose, pneumonia, pulmonary edema, AMS, etc) has resolved
• Minimal vent settings - Typically FiO2 < 40%, PEEP <= 5
• Spontaneous breathing present (i.e. pt breathes with reasonable rate on PS, SIMV, VS, PPS, etc) and able to maintain reasonable pH and pCO2 on these settings
• Neuromuscular function adequate - Ask patient to lift head off bed
• Mental status adequate - Ask patient to give thumbs up or squeeze hands
• Secretions tolerable - Ask RN or RT for frequency of suctioning and sputum character.  Think twice about extubation if getting purulent, thick secretions every 15 minutes.
• Clinical course does not require further intubation (i.e. no immediate trips planned to OR, MRI; pt not hemodynamically unstable, etc.)

If the above criteria are met, two additional tests are frequently considered:

• Spontaneous Breathing Trial (SBT) - Typically done by placing pt on PS with low settings (0/0 to 5/5).  Let pt equilibrate (time of SBT is variable) on these settings, then calculate RSBI (RR/Vt). RSBI < 105 is traditionally considered acceptable for extubation.  Remember - lower is better.  Ask RT for this. 
• Cuff Leak Test - becoming less popular, but may consider in patients at risk for laryngeal edema (e.g. prolonged intubation, angioedema, etc). Historically thought to predict airway swelling, but data is mixed.  Ask RT for this.

And don't forget to consider extubating high risk patients directly to BiPAP or HFNC!

Bottom Line: For conditions requiring intubation where significant clinical improvement may be expected while in the ED (e.g. overdose, flash pulmonary edema, etc), be vigilant about, and have a system for, assessing readiness for extubation.

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With a shortage of push dose epi, this may be an opportune time to review alternative options (see also Ashley's email on the subject).

The dose of vasopressor required to reverse hypotension has been most studied in pregnant women undergoing c-section who get epidurals and experience spinal-induced vasoplegia and hypotension (not necessarily our patient population, but we can extrapolate...)  

Phenylephrine was found to reverse hypotension 95% of the time at a dose of 159 micrograms (a neo stick has 100 ug/mL, so around 1-2 mL out of the stick)

Norepinephrine reversed hypotension in 95% of patients at a dose of 5.8 ug.  The starting dose for our norepi order in Epic is 0.01 ug/kg/min, so if you have a levophed drip hanging and have an acutely hypotensive patient, you may want to briefly infuse at a higher rate such as 0.1 ug/kg/min (for a typical weight patient), or bolus approximately 3-7 ug for a typical patient.  Of course the degree of hypotension, particular characteristics of your patient and clinical context should be taken into consideration.  When your a lucky enough to have this resource, always consult your pharmacist.

Bottom Line: To reverse acute transient hypotension you may consider:

-A bolus of phenylephrine 50-200 ug (0.5-2 mL from neo-stick)

-A bolus of norepinephrine 3-7 ug

-Briefly increasing your norepinephrine drip (if you have one) to something around 0.1 ug/kg/min in a typical weight patient

-Always search for other causes of hypotension and consider clinical context.

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Some patients with severe pulmonary hypertension receive continuous infusions at home of prostacyclins, such as epoprostanol (flolan).  These are generally delivered via a pump that the patient wears, which is attached to an indwelling catheter.  As with any indwelling device, they are at risk for infection and other complications, including malfunction.

Interruption of delivery of the medication can result in rapid cardiovascular collapse, sometimes within minutes.  In this instance, the medication should be resumed as quickly as possible (by a traditional IV if the catheter is not functional), and the patients should be treated as one would approach a patient with decompensated right heart failure.

I once saw a patient in the ED whose listed chief complaint was "medication refill", but was actually there for dislodgement of her prostacyclin catheter (thankfully she was ok).  With more patients receiving devices they are dependent upon (insulin pumps, AICDs, prostacyclin catheters), be wary of chief complaints such as "medication refill" or "device malfunction."

Bottom Line: Interruption of continuous prostacyclin therapy for pulmonary hypertension can be rapidly fatal and should be addressed immediately.

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• ANDROMEDA-SHOCK compared using capillary refill time versus lactate clearance as a guide for resuscitation in septic shock patients
• The cap refill group showed better SOFA scores at 72 hours, and a trend to lower mortality
• In the study, cap refill was performed by pressing a glass microscope slide to the ventral surface of the second finger distal phalanx, holding until blanched for 10 seconds, and releasing.  Cap refill > 3 seconds was considered abnormal.

Bottom Line: Consider using capillary refill as an alternate (or complimentary) endpoint to lactate clearance when resuscitating your septic shock patients.

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Many, if not nearly all, of our intubated patients in the ED have altered mental status, a potential to clinically worsen, or a requirement for medications that would alter their respiratory status (e.g. propofol, opioids, paralytics).  It is imperative to place these patients on appropriate ventilator modes to avoid apnea when their respiratory status changes.

• Spontaneous modes (see partial list below) REQUIRE patients to initiate breaths on their own.  No ventilation occurs in a true spontaneous mode without patient effort.  
• Patients who have alterations in respiratory drive, neuromuscular function, or are receiving paralytics should NOT be placed on:
  • Pressure Support (PSV),
  • Volume Support (VSV),
  • CPAP/BiPAP/APAP,
  • Pressure-Assisted Ventilation (PAV) / Proportional Pressure Support (PPS),
  • or other spontaneous modes
• Our hypothermia order set includes a prn paralytic (cisatracurium infusion, vecuronium bolus) to combat shivering.  Discontinue these medications for patients on spontaneous modes.
• Our Servo-I ventilators automatically backup to a control mode (VS-->VC, PS-->PC) after a period of apnea (default is anywhere from 15-45 seconds, but it depends on how the RT has set the ventilator) as a safety mechanism, but this could still cause dangerous hypoxia or hypercapnea in severely ill patients.
• If the mechanics of pressure support are desired in patients at risk of apnea, there are other methods to achieve this (PC, descending flow VC, SIMV VC+PS with a low rate, and others).
• Always consult your RT when changing ventilator settings, and be sure to take vent alarms seriously.

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Attachments

Apnea_Alarm.JPG (16 Kb)