UMEM Educational Pearls - Critical Care

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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Re-expansion Pulmonary Edema After Chest Tube Placement

• Tube thoracostomy is a common procedure in the emergency department.
• For patients who develop respiratory distress after chest tube placement, think about re-expansion pulmonary edema.
• While a rare occurrence, re-expansion pulmonary edema is reported to have a mortality rate of up to 20%.
• The mechanism by which edema forms remains controversial, but is thought to be due to increased alveolar-capillary membrane permeability in the expanding lung.
• Treatment is supportive with supplemental oxygen and diuretics.  Some patients may require mechanical ventilation depending on the degree of distress and hypoxia.

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The open cricothyrotomy technique is taught as the trauma airway standard when one “cannot intubate and cannot ventilate” however, it is not without difficulty and limitations. The B.A.C.T. (Bougie-Assisted Cricothyrotomy Technique) may improve the procedure by using a bougie to assist.

Steps for the B.A.C.T. (as described in the paper):
1. Stabilize the larynx with the thumb and middle finger, then identify the cricothyroid membrane.
2. Make a transverse stabbing incision with a scalpel through both skin and cricothyroid membrane.
3. Insert tracheal hook at the inferior margin of the incision and pull up on the trachea.
4. Insert a bougie through the incision with curved tip directed towards the feet
5. Pass 6-0 endotracheal tube or Shiley over bougie into trachea.

Advantages of a bougie:
1. Thin and easy to insert into incision
2. Tactile feedback from tracheal rings confirms proper placement
3. Ensures that stoma will not be lost during procedure

EMRAP.tv has a great video of Dr. Darren Braude demonstrating the procedure;
http://bit.ly/nB3BMG

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When may an ED thoracotomy be futile?

• Performing an ED thoracotomy is incredibly stressful and a resource-intense procedure.
• While we've all learned that stab wounds to a ventricle have the highest survival rate, what about indicators that an ED thoracotomy may be futile?
• A recent study of 18 trauma centers across the US found that ED thoracotomy was unlikely to yield productive survival in the following:
  • Blunt trauma patients that require > 10 min of prehospital CPR without response
  • Penetrating trauma patients that require > 15 min of prehospital CPR without response
  • Patients presenting in asystole without evidence of pericardial tamponade on bedside ultrasound.

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Pregnancy causes many physiologic changes, which may be challenging during trauma resuscitations. A few pearls on the ABC’s:

Airway

• Increased progesterone levels cause mucosal hyperemia and edema, increasing risk of bleeding and smaller (i.e., edematous) airway.
• PEARL: Have smaller tubes ready and let the most experienced person intubate.

Breathing

• The enlarging uterus pushes the diaphragms into the thorax, reducing the total lung capacity and the functional residual capacity.
• PEARL: During intubation, patients in late pregnancy may have less oxygenation reserve and apnea time, desaturating faster during RSI.

Circulation

• The late stage uterus can compress the IVC when supine, reducing venous return to the heart (i.e., the Supine-Hypotension syndrome) subsequently reducing cardiac output.
• PEARL: Have a 30-degree wedge placed under patient's right hip, moving the uterus off IVC and improving venous return.
• BONUS PEARL: During resuscitation, ask medical students to manually move the uterus midline, relieving the compressed IVC. They will appreciate that you got them clinically involved.

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Blood Pressure in the Critically Ill Obese Patient

• Recall that incorrectly sized cuffs can significantly overestimate blood pressure, especially in obese patients.
• In fact, some studies show that false BP readings can occur in up to 75% of obese patients.
• By relying solely on noninvasive BP measurements, many of your critically ill obese patients may actually be hypotensive and under perfused.
• When you've got a sick obese patient, strongly consider early placement of an arterial line to assess and monitor blood pressure.

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Heat stroke is hyperthermia (>41.6 Celsius / 106 Fahrenheit) plus neurologic findings (e.g., altered mental status, seizures, coma, etc.); it also causes systemic inflammation response syndrome (i.e., cytokine release), coagulation disorders (e.g., thrombosis in end organs) and tissue abnormalities (e.g., acute kidney injury and rhabdomyolysis)

Two classifications exist:

• Exertional heatstroke (young people engaged in strenuous physical activities in hot climates)
• Non-exertional heatstroke occurring in sedentary people (elderly, debilitated, or chronically-ill patients) who are unprotected from the elements (e.g., trapped in apartments during heat waves)

Treatment includes:

• Insertion of a continuous core thermometer
• Supporting ABC’s
• Cooling by at least to 0.2 degrees celsius per minute to 39 degrees (to avoid overshoot)
• Benzodiazepines for sedation, shivering, and seizures
• Antipyretics and phenytoin have not been shown beneficial
• Support and protect end-organs with particular attention to kidneys; increased risk of kidney injury from rhabdomyolysis, ischemia and systemic inflammation.

Despite the most aggressive therapy, up to 30% survivors may have permanent neurologic or multi-organ system dysfunction months to years after recovery

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Hemodynamic Optimization in the Post-Arrest Patient

• Hemodynamic instability is common in the post-cardiac arrest patient.
• While the optimal targets remain unclear, hemodynamic stabilization often consists of intravenous fluids, vasopressors, and in rare cases mechanical support, such as an intra-aortic balloon pump or left-ventricular assist device.
• Based on recent literature, current recommendations for mean arterial pressure (MAP) in the post-arrest patient range from 65-100 mm Hg.
• Depending upon the baseline blood pressure and degree of myocardial stunning, many post-arrest patients will need a higher MAP (80-100 mm Hg) in order to maintain critical perfusion pressure to vital organs such as the brain.

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Hepato-Renal Syndrome

• Hepato-renal syndrome (HRS) is the development of acute kidney injury (AKI) in patients with advanced cirrhosis.
• HRS is traditionally divided into two types based upon how quickly AKI develops:
  • Type I: a rapid decline in function in less than 2 weeks
  • Type II: a slow decline in function over weeks to months
• Type I is more likely to be seen in the ED and is often due to a precipitating event such as:
  • GI bleed
  • Spontaneous bacterial peritonitis (SBP)
  • Hypovolemia from aggressive diuresis
• In ED patients with advanced cirrhosis and new, or worsening, AKI think about HRS. 
• If suspected, look for precipitants (i.e. SBP), restore volume with IVFs, avoid nephrotoxins (IV contrast), and administer vasopressor therapy when indicated.

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Cancer patients admitted to ICUs with AKI or who develop AKI during their ICU stay have increased risk of morbidity and mortality. AKI in cancer patients is typically multi-factorial:

Causes indirectly related to malignancy

• Septic, cardiogenic, or hypovolemic shock (most common)

• Nephrotoxins:

  • Aminoglycosides

  • Contrast-induced nephropathy

  • Chemotherapy 

• Hemolytic-Uremic Syndrome

Causes directly related to malignancy

• Tumor-lysis syndrome

• Disseminated Intravascular Coagulation

• Obstruction of urinary tract by malignancy

• Multiple Myeloma of the kidney

• Hypercalcemia

Because AKI increases the already elevated morbidity and mortality in these patients, prevention (e.g., using low-osmolar IV contrast, avoiding nephrotoxins), early identification (e.g., strict attention to urine output and renal function), and aggressive treatment (e.g., early initiation of renal replacement therapy) is essential.

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