UMEM Educational Pearls - Critical Care

DSI, Ketamine, and Apnea

• In recent years, delayed sequence intubation (DSI) with ketamine has been used in select patients to maximize preoxygenation and dinitrogenation. 
• Importantly, DSI is not well studied. In the only prospective trial of DSI, patients received approximately 1.4 mg/kg of ketamine.
• Driver, et al. report the abrupt onset of apnea in a patient who received a much lower dose of ketamine (25 mg) for DSI.
• Take Home Point: If DSI is a part of your preoxygenation armamentarium, apnea can occur even at low doses of ketamine.  Stand at the patient's bedside and be ready to immediately intubate the patient.

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While lung protective ventilatory strategies have long been accepted as vital to the management of patients undergoing mechanical ventilation, the translation of such practices to the Emergency Department is still limited and inconsistent.

Fuller et al employed a protocol ensuring lung-protective tidal volumes, appropriate setting of positive end-expiratory pressure, rapid weaning of FiO2, and elevating the head-of-bed. The authors found the number of patients who had lung protective strategies employed in the Emergency Department increased from 46.0% to 76.7%. This increase in protective strategies was associated with a 7.1% decrease in the rate of pulmonary complications (ARDS and VACs), 14.5% vs 7.4%, and a 14.3% decrease in in-hospital mortality, 34.1% vs 19.6%.

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Preoxygenation in Critically Ill Patients

• Achieving adequate preoxygenation and denitrogenation prior to intubating critically ill patients can be challenging.
• Critically ill patients have physiologic alterations (i.e., derangements in oxygen consumption, anemia, reduced cardiac output, air space disease) that can markedly reduce safe apnea time.
• For patients with significant air space disease and shunt physiology, noninvasive ventilation (NIV) can decrease shunt fraction, increase functional residual capacity, improve PaO2, and lengthen safe apnea time.
• Importantly, NIV should be used for at least 3 minutes to achieve improvements in alveolar recruitment.
• It is also important to remove NIV just prior to larygnoscopy, as alveoli will begin to derecruit when NIV is removed.

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A recently published study adds to the growing body of literature supporting the use of IV//IM ketamine as a first line agent for the control of the acutely agitated patient. In this observational cohort Riddell et al found patients given ketamine more frequently achieved adequate sedation at both 5 and 10 minutes compared to benzodiazepines, Haloperidol, given alone or in combination. This rapid sedation was achieved without an increase in the need for additional sedation or the rate of adverse events. 

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Sepsis Mimics

• Emergency physicians are well versed in the resuscitation of patients with sepsis and septic shock.
• With the recent publication of the 2016 SSC Guidelines and the emphasis in meeting various quality measures, sepsis is routinely included in the differential diagnosis of critically ill patients.
• Notwithstanding, it is important to consider other disease states that can present similarly to sepsis or septic shock.  Some of these include:
  • Anaphylaxis
  • Adrenal insufficiency
  • DKA
  • Thyroid storm
  • Toxic ingestion or withdrawal

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Identifying patients at risk of hypotension during intubation is not always straight forward. The prevalence of peri-intubation hypotension in the Emergency Department has been demonstrated to be approximately 20%.¹ And while certain variables increase the likelihood of peri-intubation hypotension (ex. Shock index> 0.80), no single factor predicts it accurately enough to be used at the bedside.² In the majority of patients undergoing intubation, clinicians should be prepared for peri-intubation hypotension with either vasopressor infusions or push dose pressors.

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At the Society of Critical Care Meeting (SCCM) this month, updates to the Surviving Sepsis Guidelines were released. Recommendations include:

--Initial 30mL/kg crystalloid resuscitation with frequent reassessment of fluid responsiveness using dynamic (not static) measures [goodbye CVP/ScvO2!]

--Initiation of broad-spectrum antibiotics within ONE hour of sepsis recognition [two agents from different classes]

--Further hemodynamic assessement (e.g. echo for cardiac function) if clinical assessment does not reveal the type of shock [get out the ultrasound!]

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Epinephrine in Anaphylaxis

• Delayed administration of epinephrine for patients witih anaphylaxis is associated with increased morbidity and mortality.
• Providers are often hesitant to administered epinephrine to older patients with anaphylaxis for fear of precipitating an adverse cardiovascular event.
• A recent retrospective study of almost 500 patients demonstrated that older patients were significantly less likely to receive epinephrine, despite meeting the definition for anaphylaxis.
• Furthermore, cardiovascular complications occurred in just 9 patients, 6 of which received an excessive dose via the IV route.
• Take Home Point: There are no absolute contraindications (including age) for epinephrine in patients with anaphylaxis.  Give the initial dose IM into the anterolateral thigh.

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It is not uncommon for critically ill patients to require invasive monitoring of their blood pressure. In these patients, radial arterial lines are often inserted. Traditionally these lines are placed using palpation of the radial pulse. This technique can lead to unacceptably high failure rate in the hypotensive patient commonly encountered in the Emergency Department.

A recent meta-analysis by Gu et al demonstrated the use of dynamic US to assist in the placement of radial arterial lines decreased the rate of first attempt failure, time to line insertion and the number of adverse events associated with insertion.

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--Recent meta-analysis comparing continuous infusion versus intermittent bolus dosing of beta-lactam antibiotics demonstrates mortality benefit (NNT = 15) in patients with severe sepsis or septic shock. (1)

--Consider beta-lactam continuous infusion on your septic patients if your hospital pharmacy allows

[Thanks to Anne Weichold, CRNP for providing the article for this pearl!]

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PaCO2 and the Post-Arrest Patient

• Alterations in PaCO2 are common during the post-arrest period and have been associated with worse patient centered outcomes.
• Hypercarbia can dilate cerebral vessels, increase cerebral blood flow, and may increase intracranial pressure.
• Conversely, hypocarbia can constrict cerebral vessels and may reduce cerebral blood flow.
• Though the current evidence is primarily limited to observational trials, a recent meta-analysis found that "normocarbia" was associated with improved hospital survival and neurologic outcome. 
• Take Home: Adjust mechanical ventilation to target normocarbia (PaCO2 or ETCO2) in the post-arrest patient.

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It is well known that the early aggressive utilization of IV nitrates and non-invasive positive pressure ventilation (NIV) in patients presenting with acute pulmonary edema will decrease the number of patients requiring endotracheal intubation and mechanical ventilation. 

Often our tepid dosing of nitroglycerine is to blame for treatment failure. Multiple studies have demonstrated the advantages of bolus dose nitroglycerine in the early management of patients with acute pulmonary edema. In these cohorts, patients bolused with impressively high doses of IV nitrates every 5 minutes, are intuabted less frequently than patients who received a standard infusion (1,2). No concerning drops in blood pressure in the patients who received bolus doses of nitrates were observed. Using the standard 200 micrograms/ml nitroglycerine concentration, blood pressure can be rapidly titrated to effect.

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The Neurocritical Care Society and Society of Critical Care Medicine just came out with new Guidelines for Reversal of Antithrombotics in Intracranial Hemorrhage (ICH) [1]

--PCC is now recommended over FFP in reversal of vitamin K antagonists (VKA) with elevated INR. Either should be co-administered with 10mg IV vitamin K. (Strong recommendation, moderate quality evidence)

TAKE AWAY: PCC should be probably be given over FFP in VKA-ICH when available

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Mechanical Ventilation in the Obese Patient

• Obesity can result in decreased lung volumes, decreased lung and chest wall compliance, and increased work of breathing.
• Unfortunately, there is very little literature to guide the emergency physician on mechanical ventilation in obese patients.
• A recent study of intubated ED patients by Goyal, et al found that over 1 in 5 patients were ventilated with potentially injurious tidal volumes.
• Importantly, obesity increased the odds of inappropriate ventilator settings.
• In the intubated obese patient, be sure to set tidal volume based on ideal body weight and consider starting with a higher PEEP setting (i.e., 10 to 15 cm H2O).

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The prognosis of patients who experienced OHCA, who have not achieved ROSC by the time they present to the Emergency Department, is dismal. As such, it behooves us as Emergency Physicians to identify the few patients with a potentially survivable event. Drennan et al examined the ROC data base and identified the cohort of patients who had not achieved ROSC and were transported to the hospital. The overall survival in this cohort was 2.0%. Factors that predicted survival were initial shockable rhythm and arrest witnessed by the EMS providers. Patients arriving to the ED without ROSC, that had neither of those prognostic factors had a survival rate of 0.7%. 

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--In this study, PE was diagnosed in ~17% of patients hospitalized for syncope (though this represents only ~4%% of patients presenting to the ED with syncope).

--Patients with PE were more likely to have tachypnea, tachycardia, relative hypotension, signs of DVT, and active cancer -- take a good history and do a good physical exam!

--Consider risk stratifying (Wells/Geneva) and/or performing a D-dimer (i.e "rule out" PE) on your syncope patients, particularly when no alternative diagnosis is apparent.

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What Matters in Cardiac Arrest?

• Approximately 500,000 adults suffer sudden cardiac arrest each year in the United States.
• The most important components of cardiac arrest care that have been shown to improve outcomes are:
  1. High-quality CPR with little to no interruptions
  2. Defibrillation for ventricular arrhythmias
  3. Optimal post-arrest care
     • Target an SpO2 of 94-98%
     • Target an ETCO2 of 35-40 mm Hg (PaCO2 of 40-45 mm Hg)
     • Targeted temperature management
     • Early cardiac catheterization

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It is well documented that when left to our own respiratory devices we will consistently over-ventilate patients presenting in cardiac arrest (1). A simple and effective method of preventing these overzealous tendencies is the utilization of a ventilator in place of a BVM. The ventilator is not typically used during cardiac arrest resuscitation because the high peak-pressures generated when chest compressions are being performed cause the ventilator to terminate the breath prior to the delivery of the intended tidal volume. This can easily be overcome by turning the peak-pressure alarm to its maximum setting. A number of studies have demonstrated the feasibility of this technique, most recently a cohort in published in Resuscitation by Chalkias et al (2). The 2010 European Resuscitation Council guidelines recommend a volume control mode targeting tidal volumes of 6-7 mL/kg and a respiratory rate of 10 breaths/minute (3).

It's Election Day in the US, so here are some interesting facts about Presidential causes of death:

George Washington likely died from epiglottitis on 12/14/1799

• However, "iatrogenic" should also be listed on his cause of death
• Washington was blood let for almost 2.4L of blood!!!
• He also received an enema and multiple "blistering" treatments to draw the evil humors out of his throat
• He died before his fourth doctor, who planned to perform a tracheostomy, could arrive

CLICK BELOW FOR MORE INTERESTING FACTS!

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Dynamic LVOT Obstruction

• Recent literature has indicated that dynamic LVOT obstruction can occur in critically ill patients without hypertrophic cardiomyopathy. In fact, a recent study found that this condition may be present in many patients with septic shock.
• Risk factors for  LVOT obstruction include any condition that decreases afterload, decreases preload, or increases heart rate.
• Consider LVOT obstruction when your ultrasound demonstrates close approximation of the lateral wall and septum plus systolic anterior motion of the anterior mitral leaflet.
• The treatment of patients with dynamic LVOT obstruction includes:
  • Increasing preload with aggressive IVFs
  • Increasing afterload (phenylephrine may be a good choice)
  • Avoiding inotropes
  • Decreasing heart rate (often with esmolol)

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