UMEM Educational Pearls - By Mike Winters

Lung Protective Ventilator Settings Still Underutilized

• It's been over 10 years since the publication of the ARDSnet trial, which demonstrated an 8.8% absolute reduction in short-term mortality for patients with ARDS ventilated with "lung protective" settings (tidal volume 6 ml/kg, plateau pressure < 30 cm H20).
• A recent study in the BMJ evaluated the association of these settings with 2-yr survival in patients with acute lung injury.
• The study, carried out in 13 ICUs from 4 academic hospitals in Baltimore, found some surprising results:
  • In patients whose ventilator settings were 100% compliant with lung protective settings, there was an 8% absolute reduction in mortality.
  • For each increase of 1 ml/kg above recommended tidal volume there was an 18% relative increase in mortality.
  • 37% of patients never received lung protective ventilation.
• Take home point: lung protective settings appear to confer not only short-term but also long-term mortality benefit for patients with acute lung injury, yet remain underutilized even in major academic centers.

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Steroids and Septic Shock

• Do low-dose steroids improve mortality or shock reversal in patients with septic shock?
• A recent systematic review published in the Journal of Emergency Medicine found:
  • A statistically significant improvement in shock reversal (RR 1.17)
  • A favorable, but not statistically significant, mortality benefit for patients with refractory septic shock (RR 0.92; CI 0.79-1.07)
• Most guidelines recommend against steroids for septic patients that are responding to fluid resuscitation and vasopressor therapy.
• Updated guidelines from the Surviving Sepsis Campaign (soon to be published) will continue to recommend low-dose IV corticosteroids (200 mg over 24hrs) for those who are refractory to fluids/vasopressors.

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Anaphylaxis

• The incidence of anaphylaxis appears to be rising.
• Recall that death can occur anywhere from 5 to 30 minutes after allergen exposure.
• A few important pearls in management:
  • Epinephrine is the drug of choice and should be given intramuscularly (not subcutaneous) in the mid-anterolateral thigh.
  • Be aggressive with IV fluids, as up to 35% of circulating volume can be extravasated within 10-15 minutes of symptom onset.
  • Get an ECG ASAP! Mast cells are located around the coronary arteries.  The release of mediators can induce vasospasm and precipitate an acute coronary syndrome.

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Acute Kidney Injury and Tumor Lysis Syndrome

• Tumor lysis syndrome (TLS) is characterized by hyperkalemia, hyperphosphatemia, hypocalcemia, and hyperuricemia.
• Acute kidney injury in TLS increases patient mortality and can be caused by an obstructive uropathy from calcium phosphate crystalluria or uric acid crystal precipitation.
• Fluid resuscitation remains the primary treatment for TLS.
• Urine alkalinization, however, is no longer recommended, as it can result in calcium phosphate crystal precipitation. 
• Recombinant urate oxidase rapidly decreases uric acid levels and should be given to patients at high-risk for TLS and those with pre-existing kidney disease and high uric acid levels.

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Use the Measured Sodium Concentration!

• During a recent shift, a question arose regarding whether to use the measured or corrected sodium to calculate the anion gap in a critically ill patient with DKA.
• Recall that the anion gap provides an estimation of unmeasured anions - in this case acetoacetate and beta-hydroxybutyrate.
• Glucose is electrically neutral and therefore does not affect the anion gap.
• When calculating the anion gap in a patient with DKA, use the actual (measured) serum Na, rather than the corrected value.

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Severe UGIB

• Differentiating between upper and lower GIB can be challenging. 
• A recent review evaluated the accuracy of historical features, symptoms, signs, and lab values in distinguishing between UGIB and LGIB. 
• Features with the highest likelihood for identifying UGIB included:
  • Melenic stool on exam (LR 25)
  • A prior history of UGIB (LR 6.2)
  • Serum urea:creatinine ratio > 30 (LR 7.5)
• Features that increased the likelihood of severe UGIB (defined as requiring blood transfusion, need for urgent endoscopy, surgery, or interventional radiology) included:
  • Heart rate > 100 bpm (LR 4.9)
  • Hemoglobin < 8 g/dL (LR 6.2)
  • History of cirrhosis or cancer (LR 3.7)
• For patients with an UGIB, the Blatchford Score can be used to determine the need for urgent intervention.  Those with a Blatchford Score of 0 have a low likelihood for severe UGIB and may not need emergent intervention.

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Balloon Tamponade for Variceal Bleeding

• Despite advances in pharmacology and endoscopy, placement of a balloon tamponade device is occasionally required to stabilize a patient with acute variceal bleeding.
• Currently, there are 3 devices available: the Linton-Nachlas (gastric balloon only), the Blakemore (gastric and esophageal balloons), and the Minnesota (gastric and esophageal balloons) tubes.
• The tube should initially be passed at least to the 50-cm mark and preferably to the maximum depth allowed by the length of the tube.
• Once the gastric balloon is inflated and correct position confirmed, traction must be applied to keep the gastric balloon engaged in the cardia and fundus of the stomach.
• An overhead pulley system is the preferred method to deliver traction.  If you don't have weights for the pulley system, a 1-liter bag of crystalloid provides the desired 1.0 kg of traction.

SBP, HRS, and Albumin

• Spontaneous bacterial peritonitis (SBP) is the most common infection in patients with end-stage liver disease (ESLD).
• In critically ill patients, SBP can precipitate type 1 hepatorenal syndrome (HRS), which, if not treated, carries a mortality > 90%.
• Infusion of albumin at 1.5 g/kg at the time of SBP diagnosis (and a second dose of 1 g/kg on day 3) has been shown to significantly decrease the incidence of type 1 HRS and decrease mortality.
• In your next critically ill patient wth ESLD, strongly consider giving albumin at the time of SBP diagnosis.

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Cuff Pressures and the Prevention of VAP

• As highlighted in a recent pearl, ventilator-associated pneumonia (VAP) is the second most common nosocomial infection in the US and is associated with increases in ICU length of stay and mortality.
• With increasing ED lengths of stay for many critically ill patients receiving mechanical ventilation, measures to prevent VAP should be initiated in the ED.
• In addition to elevating the head of the bed to 30-45 degrees, another low cost intervention is the measurement of endotracheal tube cuff pressures.
• Cuff pressures below 20 cm H₂O increase the risk of VAP.
• Measure cuff pressure within 4 hours of inflation and maintain between 20-30 cm H₂O.

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Transferring Multidrug-Resistant Organisms

• Hospital-associated infections are a major cause of morbidity and mortality, especially among the critically ill.
• Worldwide, the emergence of multidrug-resistant (MDR) bacteria has caused significant problems.
• A recent study from the University of Maryland examined the impact of environmental contamination on the rate of transfer of MDR bacteria to healthcare workers clothing.
• Two important findings from this study of ICU patients were:
  • Up to 8% of healthcare workers entered a patient's room with MDR bacteria on their hands
  • Almost 5% of healthcare workers had MDR bacteria (most notably Acinetobacter) on their hands upon exiting the room despite using gloves and a gown
• Take Home Point: Be sure to use hand hygiene upon entering and exiting a patient's room who is colonized with MDR bacteria!

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High-Frequency Oscillatory Ventilation for ARDS?

• High-frequency oscillatory ventilation (HFOV) is increasingly utilized for adult patients with ARDS who remain hypoxemic despite optimal settings of conventional mechanical ventilation (CMV).
• HFOV maintains a constant mean airway pressure and delivers very small tidal volumes (1-3 ml/kg) at very high respiratory rates (frequency range up to 10 Hz).
• Potential advantages to HFOV over CMV include greater alveolar recruitment, prevention of atelectrauma, and limiting excess alveolar distension (i.e. volutrauma).
• Studies on HFOV in adults are not as numerous as those in neonates.  As a result, optimal timing for initiation of HFOV is unclear.
• Nevertheless, some recommend considering HFOV for patients who persistently need an F_iO₂ > 60% with at least 10 cm H₂O of PEEP on CMV.
• Due to the ventilator settings, patients receiving HFOV often require significant sedation and often neuromuscular blockade.  

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Preventing VAP in the Intubated ED Patient

• Ventilator-associated pneumonia (VAP) occurs in 9-27% of patients receiving mechanical ventilation (MV).
• VAP increases the duration of MV and increases the ICU length of stay.
• VAP is primarily caused by aspiration of oropharyngeal secretions either during intubation or while receiving MV.
• While there are many interventions that may potentially reduce the incidence of VAP (aspiration of subglottic secretions, selective digestive decontamination, monitoring endotracheal cuff pressure), a simple, no cost intervention is patient positioning.
• Placing intubated patients in the semirecumbent position is associated with a lower risk of VAP.

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Ice-Cold Crystalloid for Therapeutic Hypothermia

• Therapeutic hypothermia (TH) is a critical component in the care of patients with ROSC from out-of-hospital cardiac arrest.
• Despite recent guidelines, initiation of TH in the ED for appropriate patients remains less than optimal.
• Reported barriers to the induction of TH in the ED include lack of familiarity, lack of collaboration with the ICU, access to special equipment, and the logistics of cooling.
• A recent analysis of studies on the use of ice-cold crystalloids (ICC) found that an infusion of 4⁰ C fluid is a safe, effective, inexpensive, and readily available method for inducing TH.
• Importantly, no study reported any significant hemodynamic complication (i.e. CHF) from the use of ICC.
• Lastly, once the target temperature has been reached, ICC alone cannot maintain TH.  Additional methods, such as surface cooling blankets or ice packs, should be used.

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ECMO for ARDS and Refractory Hypoxemia

• Extracorporeal membrane oxygenation (ECMO), or extracorporeal life support (ECLS), is increasingly being used for a variety of cardiac and pulmonary conditions.
• Venovenous ECMO (VVE) should be considered in the treatment of patients with profound gas-exchange abnormalities that are refractory to accepted standards in ventilator management.
• Although indications vary slightly by institution, general indications for VVE include:
  • Severe hypoxemia: P_aO₂/F_iO₂ < 80 despite high levels of PEEP for at least 6 hours
  • Uncompensated hypercapnia with pH < 7.15
  • Excessively high plateau pressures (> 45 cm H₂0)

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SAH and Pulmonary Edema - Think Twice About Diuresis!

• Delayed cerebral ischemia (DCI) is the most common cause of secondary neurologic injury in patients with aneurysmal subarachnoid hemorrhage (SAH).
• Intravascular volume depletion is one of several factors thought to cause, or worsen, DCI.
• Pulmonary edema frequently occurs in patients with SAH.
• A recent study in patients with SAH and pulmonary edema demonstrated that many were not volume overloaded.  In fact, many were intravascularly volume depleted.
• Think twice about aggressive diuresis in patients with SAH and pulmonary edema, as this may exacerbate volume depletion and may worsen DCI.

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Hypertonic Saline for Intracranial Hypertension

• Mannitol is commonly used to treat acute increases in intracranial pressure in patients with TBI, ICH, tumor, and CVA.
• While there is currently no conclusive evidence of superiority, a growing body of literature suggests hypertonic saline (HTS) may be more favorable than mannitol for acute increases in ICP.
• HTS is believed to work by:
  • osmotic effect
  • increasing cardiac output and MAP, thereby increasing cerebral oxygen delivery
  • improving microcirculatory flow
  • anti-inflammatory effects
• When administering HTS, concentrations ranging from 1.5% - 23.4% can be used, titrating to a serum Na concentration of 145-155 and a serum osm > 350 mOsm/L.

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VBG to Assess Respiratory Function?

• Arterial blood gas (ABG) analysis is often used in to evaluate pulmonary function in critically ill ED patients.
• In recent years, venous blood gas (VBG) analysis has replaced ABG analysis for assessing acid-base status (pH, HCO₃^-) in conditions such as DKA.
• Some key points about the VBG for assessing pulmonary function:
  • VBG does not replace an ABG in determining the exact P_aO₂
  • The agreement between the VBG and ABG PCO₂ is often poor and unpredictable
  • There is emerging literature on the use of VBG PCO₂ as a screen for hypercarbia but more data is needed
• Bottom line: With the possible exception of screening for hypercarbia, VBG has limited utility in the assessment of pulmonary function.

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The Crashing Patient with PAH

• In recent weeks, we've highlighted some pearls regarding the management of patients with pulmonary arterial hypertension (PAH).
• In the crashing patient with PAH, think about the following:
  • Catheter occlusion or malfunction (for those receiving IV prostacyclin analogues)
  • PE (for those inadequately anticoagulated)
  • Pneumonia
  • RV ischemia
  • GI bleeding
  • Ischemic bowel
• In the patient receiving IV epoprostenol (Flolan) who presents with a catheter occlusion or malfunction, time is of the essence. Restart the medication through a peripheral IV as soon as possible.

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Hypotension in the PAH Patient

• Hypotension in the critically ill patient with pulmonary arterial hypertension (PAH) must be rapidly treated to avoid cardiovascular collapse.
• Hypotension in the PAH patient is not always due to hypovolemia.  In fact, excessive volume loading may further decrease LV stroke volume.  Consider starting with a fluid bolus of 250 ml of an isotonic crystalloid solution and monitoring response.
• Patients with severe PAH may present to the ED with a continuous flow pump of a pulmonary vasodilator (epoprostenol, treprostinil).  These medications can also cause hypotension at excessive doses.  Consider decreasing the rate of the infusion by 25% to see if overdosing is the cause.

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Hypertensive Emergency Pearls

• Recent literature indicates that many patients with a true hypertensive emergency are mismanaged.
• Patients with a hypertensive emergency should have an arterial line placed and receive a continuous infusion of a short-acting, titratable medication to reduce blood pressure.  Avoid oral, sublingual, and intermittent IV bolus administration of antihypertensives. 
• Recall that most patients with a hypertensive emergency are volume depleted.  Providing IV fluids can help to prevent marked drops blood pressure when you start an IV antihypertensive medication.
• Avoid diuretics (due to volume depletion) and hydralazine.  Hydralazine can cause precipitous drops in blood pressure and is felt by many to have no role in the treatment of hypertensive emergencies.

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