UMEM Educational Pearls - Critical Care

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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Carotid or vertebral artery injury following blunt trauma is a rare (%1 of blunt trauma), but a potentially serious injury potentially causing stroke and long-term disability.

Injury leads to an intimal tear becoming a nidus for platelet aggregation; thrombosis and/or distal emboli may subsequently develop.

Mechanisms of injury include:

• Blunt trauma to the neck
• Hyper-extension of neck with contralateral rotation of the head
• Intra-oral trauma
• Arterial laceration secondary to adjacent sphenoid or petrous bone fracture.

Symptoms of carotid injury may include contralateral sensorimotor deficits; Symptoms of vertebral injury may include ipsilateral facial pain and numbness, headache, ataxia, or dizziness.

Angiography is the diagnostic “gold standard” but these days a 16-slice CT angiography (or greater) is a reliable screening tool.

Anticoagulation with heparin is the treatment of choice for severe injury, if there are no contraindications (e.g., intracranial bleeding). Anti-platelet drugs may be acceptable in certain cases.

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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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Amiodarone-induced lung toxicity (ALT) is a serious and sometimes fatal complication of amiodarone use.

Symptoms range from mild (e.g., dyspnea with exertion) to acute respiratory distress syndrome and risk of death.

ALT is secondary to either release of toxic oxygen radials that are directly toxic to the lung or the reaction is secondary to an indirect immunologic reaction.

Risk factors for ALT: use > 2 months, dose > 400mg/day, advanced age, or pre-existing lung injury

ALT is typically a diagnosis of exclusion so suspect ALT through a detailed history; physical exam and radiology are non-specific. Lung biopsy is the only confirmatory test.

Treat ALT by discontinuing the drug, steroids, and supportive care. In rare cases where amiodarone cannot be safely discontinued (i.e., life-threatening arrhythmia), dosage should be reduced and steroids added immediately.

Generally, ALT is reversible with a good prognosis.

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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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Up until recently, a tight-fitting mask was one of the only ways to deliver non-invasive positive-pressure ventilation.

High-flow nasal cannulas (HFNC) have been adapted from use in neonates to adults to deliver continuous positive airway pressure (CPAP).

HFNC provides continuous, high-flow (up to 60 liters), and humidified-oxygen via nasal cannula providing positive pressure to the pharynx and hypopharynx. Patients tolerate it well and it is less claustrophobic than tight-fitting masks.

HFNC does not generate the same amount of pressure as CPAP so it may be best utilized as an intermediate step between low-flow oxygen (i.e., traditional nasal cannula) and non-invasive positive pressure ventilation with tight-fitting masks.

Check with your respiratory department if these devices are locally available.

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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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Determining the exact etiology of hypotension / shock can sometimes be difficult in the Emergency Department.

The Rapid Ultrasound for Shock / Hypotension (RUSH) exam is a sequential, 5 step-protocol (typically requiring less than 2 minutes) that can be used to determine the cause(s) of hypotension.

The mnemonic for the exam is “HI MAP”, and is easy to remember because a "HI MAP" is our goal with hypotensive patients.

H - Heart (parasternal and four-chamber views)
I  - Inferior Vena Cava (for volume responsiveness)
M - Morrison’s pouch (i.e., FAST exam) and views of thorax (looking for free fluid)
A - Aortic Aneurysm (ruptured abdominal aneurysm)
P - Pneumothorax (i.e., Tension PTX)

Refer to the link for a more detailed discussion and podcast from the creators of this exam: emcrit.org/rush-exam

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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Positive-pressure ventilation (e.g., mechanical ventilation) increases intrathoracic pressure potentially reducing venous return, right-ventricular filling, and cardiac output.

Pericardial tamponade similarly causes hemodynamic compromise through increased pericardial pressure which reduces right-ventricular filling and cardiac output.

When mechanically ventilating a patient with known or suspected pericardial tamponade the mechanisms above may be additive, causing cardiovascular collapse and possibly PEA arrest.

For the patient with known or suspected pericardial tamponade consider draining the pericardial effusion prior to intubation or delaying intubation until absolutely necessary.

If intubation is unavoidable, consider maintaining the intrathoracic pressure as low as possible (by keeping the PEEP and tidal volumes to a minimum) to ensure adequate cardiac filling and cardiac output.

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Mechanical Ventilation in Patients with Pulmonary HTN 

• In the critically ill patient with pulmonary HTN and respiratory failure, improper mechanical ventilator settings can be disastrous.
• Large lung volumes and high levels of PEEP can result in acute cardiovascular collapse.
• When setting the ventilator is these patients, select low tidal volumes and relatively low levels of PEEP (3-5 cm H₂O).
• In addition, small studies suggest avoiding permissive hypercapnia, as this may increase pulmonary vascular resistance and mean pulmonary arterial pressure.

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• On October 25, 2011, Eli Lilly announced a voluntary-recall of activated drotrecogin alfa (Xigris) following a recent trial (PROWESS-SHOCK), which demonstrated no survival benefit when using the drug when compared to placebo.

• Activated drotrecogin alfa is a recombinant form of human activated protein C previously recommended for adults with severe sepsis and a high-risk of death (APACHE II > 25 or multi-organ failure); it is included in the 2008 International Sepsis Guidelines (Grade 2b recommendation).

• The PROWESS-SHOCK trial reported an all-cause mortality rate of 26.4% in the drotrecogin alfa group compared with 24.2% in the placebo group; this difference was not statistically significant.

• Interestingly, the study also found that severe bleeding (the drug's main side-effect) was found to be 1.2% in the activated drotrecogin alfa group compared to 1.0% for the placebo group (also non-significant) suggesting it does not increase the risk of bleeding as it had previously been reported.

• Hospitals should revise their sepsis guidelines based on this recent news.

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SAH and Electrolyte Disorders

• Hyponatremia can be seen in up to 40% of patients with a SAH.
• Most often, hyponatremia in patients with an SAH is due to SIADH or the cerebral salt wasting syndrome.
• To date, hyponatremia has not been associated with poor outcome.
• Treatment should focus on the underlying cause and often includes volume replacement with isotonic crystalloids (0.9% NaCl).

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Lisiteria Monocytogenes is typically transmitted from ingestion of contaminated food such as unpasteurized milk or cheese, raw foods, and recently cantaloupes; transmission from veterinary exposure, infected soil and water have also been reported.

Listeria has a predilection for the central nervous system (CNS) causing several infections including meningioencephalitits, brain or spinal abscess, cerebritis (infection of brain parenchyma), and rhomboencephalitis (encephalitis of the brainstem).

Risk factors include immunosuppression, advanced age, newborns, and pregnancy.

There is no clinical way to distinguish CNS infection with Listeria from other pathogens, therefore blood and cerebrospinal fluid (CSF) culture is required.

CSF analysis demonstrates pleocytosis, elevated protein, and low glucose. CSF gram stain has a low sensitivity (~33%), but consider Listeria in the differential if "diptheroid-like" bacteria are reported on gram stain.

Ampicillin is the drug of choice and should be continued for at least three weeks (sometimes longer). Adding gentamycin is sometimes recommended for synergy in severe infection.

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Fever and ICH

• Fever is a common event in patients with intracerebral hemorrhage (ICH) and is associated with an increased length of ICU stay, cognitive impairment, and poor outcome.
• While much of the management (and controversies) of the patient with ICH focuses on blood pressure control and reversal of oral anticoagulants or antiplatelet agents, don't forget about temperature control.
• Aggressively treat temperatures ≥ 38.3^oC in patients with an ICH.
• Importantly, there is currently insufficient evidence to support a superior method of fever control (antipyretics or surface/intravascular cooling devices).

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·  The use of epinephrine in cardiac arrest is currently standard of care.

·  Several observational and non-randomized trials have demonstrated the efficacy of epinephrine in cardiac arrest, but there has never been a randomized double-blind placebo-controlled trial in humans.

·  A recently published Australian trial randomized cardiac patients (of any type) to receive either 1 mg of epinephrine (n=272) or 0.9% normal saline (n=262); the primary end-point was survival to hospital discharge. Secondary end-points were pre-hospital return of spontaneous circulation (ROSC) and neurological outcomes at hospital discharge.

·  Significantly more patients had pre-hospital ROSC in the epinephrine group (regardless of the underlying rhythm), however, there was no statistically significant difference in survival to discharge (the primary outcome) between groups.

·  This randomized double-blinded placebo-controlled trial raises many new and interesting questions about epinephrine, but more study is needed before changing current practice.

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Spontaneous Bacterial Peritonitis

• Critically ill patients with end-stage liver disease (ESLD) may be some of the sickest patients you'll ever manage.
• Recall that patients with ESLD have higher rates of infection and worse outcomes.
• Always consider spontaneous bacterial peritonitis (SBP) in the sick patient with ESLD.  In fact, SBP is the most common infection in ESLD patients.
• Physician impression alone has been repeatedly shown to be inaccurate in ruling out SBP.
• In the critically ill patient with ESLD and ascites, tap the belly!

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Radial and femoral arteries are common sites for arterial-line placement, but are not without complications (e.g., Radial artery: malfunction with positioning and Femoral artery: contamination and infection); an alternative site to consider is the axillary artery.

The axillary artery's superficial location and large size make it a desirable choice for cannulation.

The "anatomical-landmark" and "palpation" methods have been the traditional techniques of axillary arterial cannulation, however these methods may be difficult for to a variety of reasons (e.g., obesity, anasarca, arterial disease, etc.)

Ultrasound allows visualization of the axillary artery and avoids unintended injury to structures in close proximity (e.g., brachial plexus, pleura, axillary vein, etc.); please see figures 1 and 2 in the referenced Sandhu article and http://www.youtube.com/watch?v=Z31YiyV7cNQ.

A recent study (Killu, 2011) found that ultrasound increases success rates when compared to the traditional landmark approach.

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Fungal Sepsis in the Critically Ill

• In recent years, the incidence of invasive fungal infections has risen dramatically.
• Candida species (C. albicans, C. glabrata, C. parapsilosis, C tropicalis, C. krusei) account for the majority of invasive infections in the critically ill patient.
• Key risk factors for invasive candidal infections include:
  • Exposure to broad spectrum antibiotics
  • Cancer chemotherapy
  • Indwelling catheters
  • TPN administration
  • Neutropenia
  • Hemodialysis
• Given the significant mortality of invasive fungal infections, early and appropriate antifungal therapy is paramount.
• First-line empiric antifungal therapy recommendations from the Infectious Disease Society of America include caspofungin, micafungin, or fluconazole.  Amphotericin B is now reserved for patients who are either intolerant or not responding to the echinocandins (caspofungin, micafungin).

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• Multiple methods of confirming endotracheal tube placement exist, however quantitative waveform capnography is the most reliable method. Unfortunately this may not be immediately available at all medical centers.

• Recent studies demonstrate that bedside ultrasound may assist in the detection of proper endotracheal tube placement.

• The T.R.U.E. (Tracheal Rapid Ultrasound Exam) was demonstrated to be 99% sensitive, 94% specific, 99% PPV, and 94% NPV during intubation.

• The basic exam involves placing a high-frequency linear-array probe on the anterior neck above the sternal notch and identifying the trachea and esophagus during intubation.

• The following video is an example of what you DO NOT want to see during an intubation: http://www.youtube.com/watch?v=LvfThxhQ93A

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