UMEM Educational Pearls - Critical Care

Ventilation During Cardiopulmonary Resuscitation  

• Cardiopulmonary resuscitations are often highly stressful and chaotic situations.  As a result, it is no surprise that ventilation rates can be as high as 60 breaths per minute.  
• Hyperventilation during cardiopulmonary resuscitation can increase intrathoracic pressure, impair venous return, decrease coronary perfusion pressure, and ultimately decrease survival.
• It is imperative that the team leader pay close attention to ventilation and ensure that approximately 8 to 10 breaths per minute are delivered.
• Once ROSC is achieved, the respiratory rate should be adjusted to maintain a PaCO2 between 40 and 45 mm Hg.  

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In patients with persistent VT/VF cardiac arrest, giving epinephrine before the 2nd defibrillation attempt (which should follow initial shock and 2 minutes of CPR) is associated with decreased ROSC, decreased hospital survival, and decreased functional outcome. 

Take Home Point:

"Electricity before Epi" in patients with persistent VT/VF arrest, at least for the initial epinephrine dose.

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The poor sensitivity of bedside echocardiography to identify all-comers with pulmonary embolism is well documented. Most series cite a sensitivity and specificity of 31% to 72% and 87% to 98%, respectively (1,2). But as Nazerian et al demonstrate in their recent publication in Internal and Emergency Medicine, the diagnostic performance of bedside echocardiography is far more reliable in the subset of patients presenting in shock (3).

Of the 105 patients included in the final analysis, in 43 (40.9%) PE was determined to be the etiology of their shock. Bedside echo demonstrated notable diagnostic prowess when employed in this subset of patients, sensitivity (91%), specificity (87%), –LR (0.11), +LR (7.03). The sensitivity and –LR were further augmented when the venous US of the LE was included (sensitivity of 95% and –LR of 0.06) in the diagnostic workup. 

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Antibiotics in Sepsis

• Currently international guidelines for the management of sepsis and septic shock recommend antibiotic administration within 1 hour of recognition.
• With the persistent problem of ED boarding, many patients with sepsis and septic shock remain in the ED long after the initial dose of broad-spectrum antibiotics.
• A recent single center, retrospective cohort study demonstrated that 1 out of 3 patients with sepsis or septic shock experienced major delays in the time to the second dose of antibiotics.  In fact, over 70% of patients who were given an initial antibiotic with a 6-hr recommended dosing interval experienced major delays.
• Inpatient boarding in the ED was found to be an independent risk factor for major delays.
• Take Home Point: Don't forget to write for additional doses of antibiotics in your boarding patients with sepsis.

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High flow nasal cannula (HFNC) is a valid option in the management of acute hypoxic respiratory failure (AHRF) without hypercapnia, as evidenced by multiple studies including the FLORALI trial. Failure of HFNC, however, may result in delayed intubation and worsened clinical outcomes. 

Factors predicting HFNC failure and subsequent intubation include:

• Lack of RR improvement at 30 and 45 minutes after initation of HFNC
• Lack of SpO2% improvement at 15, 30, and 60 minutes
• Persistence of paradoxic breathing (thoracoabdominal dyssynchrony) at 15, 30, 60, and 120 minutes
• Presence of additional organ system failure, especially hemodynamic (shock) or neurologic (depressed mental status)

Consider whether or not HFNC is appropriate in your patient with AHRF, and if you use it, reevaluate your patient to ensure improvement, or escalate their respiratory support. 

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Ventilator Settings for the Post-Arrest Patient

• The majority of patients with ROSC from OHCA require intubation and mechanical ventilation.
• Correctly managing the ventilator in the post-arrest patient is critical for improving outcomes.
• As patients are at high risk for ARDS, use lung-protective ventilation with tidal volumes between 6 to 8 ml/kg of ideal body weight and PEEP of 5 to 8 cm H2O.
• There is a U-shaped relationship between neurologic outcomes and both PaO2 and PaCO2.
  • Target normoxia (SpO2 94% to 96%) and avoid hyperoxia and hypoxia.
  • Target normocapnia (PaCO2 40 to 50 mm Hg) and avoid hypercapnia and hypocapnia.
• Use an analgosedation approach with short-acting analgesics and sedatives, such as fentanyl and propofol.

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Save time by using bedside ultrasound to confirm above-the-diaphragm central venous catheter (CVC) placement rather than waiting for chest x-ray confirmation:

1. Perform rapid push of saline (it doesn’t have to be agitated) through CVC while cardiac probe is placed with right atrium in view. Immediate visualization of bubbles (or “atrial swirl”) essentially confirms correct placement.

2. Perform the usual search for ipsilateral lung-sliding and the waves-on-the-beach to rule out procedural pneumothorax.

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The deleterious effects of hyperoxia are becoming more and more apparent. But obtaining a blood gas to ensure normoxia in a busy Emergency Department can be burdensome. And while the utilization of a non-invasive pulse oximeter seems ideal, the threshold that best limits the rate of hyperoxia is unclear.

Durlinger et al in a prospective observational study demonstrated that an oxygen saturation 95% or less effectively limited the number of patients with hyperoxia (PaO2 of greater than 100 mm Hg). Conversely when an SpO2 of 100% was maintained, 84% of the patients demonstrated a PaO2 of greater than 100 mm Hg.

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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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