UMEM Educational Pearls - Critical Care

Category: Critical Care

Title: Sugar isn't always so sweet

Posted: 10/22/2012 by Haney Mallemat, MD (Emailed: 10/24/2012) (Updated: 10/24/2012)
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A study by Perner, et al recently published in NEJM observed that using hydroxyethyl starch (HES) as a resuscitation fluid increased mortality and renal replacement therapy at 90 days as compared to lactated acetate.
 
Another recent trial, called the “Crystalloid versus Hydroxyethyl Starch Trial” (CHEST) was a prospective randomized control trial from Australia comparing the use of 6% HES and 0.9% sodium chloride as a resuscitation fluid in the critically ill. 
 
With 7,000 patients enrolled (3,500 in each group), the CHEST trial is the largest single-trial of HES to date; the primary outcome was 90-day mortality and secondary outcomes were acute kidney injury (AKI) and renal-replacement therapy
 
The study concluded that there was no difference between groups for either morality or renal failure, but significantly more patients in the HES group required renal replacement therapy.
 
Bottom line: There is still no convincing data that patients receiving HES as part of their resuscitation have better outcomes compared to crystalloid (normal saline or lactated ringers) and there is increased harm with their use. Furthermore, the increased cost of HES does not appear to justify their routine use.

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Category: Critical Care

Title: Delirium in the Critically Ill

Posted: 10/16/2012 by Mike Winters, MD (Updated: 1/27/2023)
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Delirium in the Critically Ill

  • Delirium has been shown to be an independent predictor of mortality and can occur in up to 75% of critically ill patients.
  • Whether preventing or treating delirium in the critically ill patient, consider the following:
    • Minimize the use of anticholinergic medications (i.e. diphenhydramine, chlorpromazine)
    • Ensure pain is adequately controlled (avoid meperidine and tramadol)
    • Be careful with sedative medications; consider bolus dosing and daily interruption of continuous infusions
  • Additional measures to treat delirious patients include reducing sensory deprivation, promoting normal sleep-wake cycles, early physical rehabilitation, and treating psychosis.

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Question

70 year-old male recently treated for community-acquired pneumonia presents with bloody diarrhea, fever, and severe abdominal pain. Abdominal Xray is shown below. Diagnosis?  

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Category: Critical Care

Title: TTP

Posted: 10/2/2012 by Mike Winters, MD (Updated: 1/27/2023)
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Thrombotic Thrombocytopenic Purpura (TTP)

  • TTP is a true hematologic emergency.  As a result of delays in diagnosis and initiation of treatment, mortality remains around 20%.
  • Often, patients present with nonspecific symptoms that include weakness, anorexia, nausea, vomiting, and diarrhea.
  • Recall that the textbook pentad is rarely present upon presentation.  In fact, renal failure and neurologic deficits are late findings.
  • Plasma exchange remains the treatment of choice for critically ill ED patients with TTP.
  • If plasma exchange is not immediately available, consider FFP (15-30 ml/kg) and methylprednisolone (10 mg/kg).

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Intubated patients may occasionally meet certain criteria for extubation while in the Emergency Department. Extubation is not without its risk, however, as up to 30% of patients have respiratory distress secondary to laryngeal and upper airway edema, with some patients requiring re-intubation.

Prior to extubation, Intensivists use a brief “cuff-leak” test (deflation of the endotracheal balloon to assess the presence or absence of an air-leak around the tube) to indirectly screen for the presence of upper airway edema and ultimately the risk of re-intubation. The cuff-leak test is performed by deflating the endotracheal balloon followed by one or more of the following maneuvers:

  • Using the ventilator to measure the difference between inspired and expired tidal volumes; if there is a difference in the measured volumes, then air is “leaking” around the endotracheal tube, implying minimal airway edema.
  • Auscultation for an air “leak” around the tube during mechanical ventilation; auscultation of a leak implies that air is passing around the tube and minimal airway edema is present.
  • Disconnecting the patient from the ventilator and occluding the endotracheal tube during spontaneous breathing; auscultation of a leak implies that there is air passing around the tube and minimal airway edema is present.

Ochoa et al. performed a systematic review to determine the accuracy of the “cuff-leak” test to predict upper airway edema prior to extubation. The authors concluded that a positive cuff-leak test (i.e., absence of an air-leak) indicates an elevated risk of upper airway obstruction and re-intubation. A negative cuff-leak test (i.e., presence of an air-leak), however, does not reliably exclude the presence of upper airway edema or the need for subsequent re-intubation.

Bottom line: No test prior to extubation reliably predicts the absence of upper airway edema. Patients extubated in the Emergency Department require close observation with airway equipment located nearby.

 

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The Lung Transplant Patient in Your ED

  • The number of lung transplant recipients is increasing.  With improved immunosuppressant medications, pts are living longer.  In fact, the 5-yr survival rate is now approximately 60%.
  • When evaluating a lung transplant pt who is < 1 yr following transplant, think about acute rejection and infection
  • Acute rejection occurs in up to 40% of pts, can present with cough, SOB, malaise, or hypoxia, and is treated with high-dose corticosteroids.
  • Infection
    • Bacterial infections usually occur in the early stages following transplant, with Pseudomonas the predominant organism
    • CMV is the most common organism affecting up to 33% of pts during the first year after transplant

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Question

40 year-old male with severe uncontrolled hypertension presents with altered mental status (head CT below). The CXR is from the same patient. What's the connection?

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Right Heart Failure in the Critically Ill

  • In its most simplistic form, right heart failure (RHF) is due to either to right ventricular contractile dysfunction or elevated right ventricular afterload.
    • Primary causes of RV contractile dysfunction include: coronary ischemia, sepsis, drug toxicity, and acute pulmonary hypertension
    • Primary causes of increased RV afterload include: LV dysfunction, venous thromboembolism, hypoxic pulmonary vasoconstriction, and lung injury
  • Management of the patient with RHF centers on identifying and treating reversible causes, optimizing preload, inotropes, and possible implantation of a right ventricular assist device.
  • Importantly, excessive volume loading can worsen RV contractile function, increase RV dilatation, and impair LV output and systemic perfusion.
  • Consider early use of inotropic agents, such as dobutamine, in critically ill patients with RHF.

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A Cochrane review of 37 studies concluded that Succinylcholine (SUC) is superior to Rocuronium (ROC) during rapid sequence intubation.

The authors claim that compared to ROC, SUC has a faster onset of action (45 vs. 60 seconds) and overall a shorter duration of action (10 vs. 60 minutes).

Dr. Reuben Strayer wrote a letter to the journal editors and stated that these findings should be interpreted carefully; he highlighted that most of the studies in the review used doses of ROC less than 0.9 mg/kg (most studies used 0.6mg/kg).

Dr. Strayer asserted that ROC’s onset of action is dose dependent; when using doses of 1.2 mg/kg, ROC’s onset is indistinguishable from that of SUC. He also stated another major benefit of ROC is the lack of adverse effects that SUC possesses (hyperkalemia and malignant hyperthermia).

What are your thoughts on this? Go to http://www.facebook.com/Criticalcarenow and take the poll (there are 5 choices). Results will be posted next week.

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Category: Critical Care

Title: Fluids and AKI

Posted: 8/21/2012 by Mike Winters, MD (Updated: 1/27/2023)
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AKI and Fluid Balance

  • Up to 70% of critically ill patients develop acute kidney injury (AKI), with 5-6% of ICU patients requiring renal replacement therapy (RRT). 
  • Maintaining adequate renal perfusion is central to the management of AKI in the critically ill patient.  As such, fluids are frequently administered.
  • As we've highlighted in previous pearls, there is mounting evidence to indicate that a positive fluid balance may be detrimental for select critically ill patients.
  • Results from a recent publication suggest a positive fluid balance in patients with AKI may be harmful.
    • Bellomo, et al analyzed data from the RENAL trial to determine the association between daily fluid balance and outcomes.
    • Investigators found a 70% reduction in 90-day mortality for critically ill patients who had a negative mean daily fluid balance compared to those that had a positive balance.
    • A negative fluid balance was also associated with decreased ICU length of stay and the need for RRT.
  • Take Home Point: Once critically ill patients with AKI are resuscitated, maintaining a slightly negative daily fluid balance may be beneficial.

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Femoral venous access is typically limited to the acute resuscitation of critically-ill patients. Several practice-guidelines recommend avoiding the femoral site, or removal once admitted to the ICU, because of the risk of catheter-related bloodstream infection (CRBI) and deep-vein thrombosis (DVT).

A recent systematic review and meta-analysis (including two randomized-control trials and eight cohort-studies) evaluated the risk of CRBI and DVT for catheters placed in either the internal jugular, subclavian, or femoral-venous sites. No difference in the rate of CRBI or DVT was found between the three sites, although the DVT data was less robust (i.e., contained heterogeneous data).

The authors hypothesized that improvements in sterility during central-line placement (e.g., full-barrier precautions), improved nursing care (e.g., central-line site care), and ultrasound guidance may have led to a reduction in femoral site complications. 

Although a prospective randomized-control trial is necessary to confirm these results, this meta-analysis challenges the traditional teaching that femoral central-access should be avoided.

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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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Crystalloids (i.e., 0.9% saline and lactated ringers) have been used during resuscitation for more than a century. Their invention, however, was more accidental than intentional.

Crystalloids were first used during the European Cholera epidemic of 1831. Hartog Hamburger later modified this solution in 1896 to the solution we know today as "normal" saline. Hamburger's solution was only intended for in vitro study of RBC lysis and was never intended for clinical use.  

Around this time, Sydney Ringer was testing several fluids to use for physiologic studies. Ringer's lab assistant was erroneously substituting tap water for distilled water when preparing these solutions. Ringer later discovered that this tap water contained minerals making the solution "physiologic", isotonic, and safe for human use; Alexis Hartmann later added sodium lactate to create Ringer's Lactate. 

Since the invention of crystalloids, many types of resuscitation fluids have been created and studied (i.e., albumins, gelatins, and starches); all have been shown to be more expensive, with no more benefit, and with possibly more harm when compared to crystalloids. 

The "perfect" resuscitation fluid still alludes us today, but of all of the solutions marketed crystalloids are arguably the best...despite their accidental history.

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Category: Critical Care

Title: Steroids and Septic Shock

Posted: 7/24/2012 by Mike Winters, MD (Updated: 1/27/2023)
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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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Wernicke encephalopathy (WE) is a neurologic disorder secondary to prolonged thiamine deficiency; it is characterized by confusion, ataxia, and ocular abnormalities. 

Traditional medical teaching advises against the administration of glucose (or glucose containing fluid) in thiamine deficient patients, without first giving thiamine, as this may precipitate WE. 

This teaching is problematic, however, in hypoglycemic patients who require the immediate administration of glucose while simultaneously being suspected of thiamine deficiency (e.g., malnourished alcoholics). Delays in treating hypoglycemia may be more harmful (e.g., seizures, permanent neurologic deficits, etc.) than the risk of WE.

Schabelman et. al performed a literature search to unearth the origins of this teaching. Nineteen papers related to this topic were found consisting of case reports, animal studies, and expert opinion; there were no randomized trials, cohort studies, or case-control studies.

Bottom-line: The available evidence does not support withholding glucose treatment until thiamine can be administered and educators should consider abolishing this dogmatic teaching until better evidence is available.

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Category: Critical Care

Title: Anaphylaxis

Posted: 7/10/2012 by Mike Winters, MD (Updated: 1/27/2023)
Click here to contact Mike Winters, MD

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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Category: Critical Care

Title: Decisions, Decisions...Crystalloid or Colloid?

Keywords: hydroxyethyl starch crystalloid, colloid, lactated ringers, normal saline, resuscitation, sepsis, hypotension (PubMed Search)

Posted: 7/3/2012 by Haney Mallemat, MD
Click here to contact Haney Mallemat, MD

Septic patients with hemodynamic instability often require intravenous fluids as part of their resuscitation. Major debate has occurred whether the optimal resuscitation fluids are crystalloids (e.g., normal saline) or colloids (e.g., albumin).

In theory, colloids are more potent intravascular expanders than crystalloids because their oncotic pressure is higher and should increase intravascular volume similarly to larger amounts crystalloid (i.e., colloids require less volume during resuscitation). 

Despite these theoretical benefits, the colloid hydroxyethyl starch (HES), has come under scrutiny after prior studies have linked its use with adverse outcomes. 

A recent prospective randomized-control trial compared the use of HES to lactated acetate for resuscitating septic patients and found that HES significantly increased both the incidence of renal-replacement therapy and mortality at 90 days (both primary end-points in the study).

Bottom line: There is no convincing data that HES performs superiorly to crystalloid for resuscitation in sepsis and there is increased harm with its use. Furthermore, the increased cost of HES compared to crystalloids does not justify its routine use.

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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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Two recently presented abstracts at the 2012 Society of Critical Care Medicine conference suggest that the combination of vancomycin and piperacillin-tazobactam may lead to acute kidney injury (AKI) in the critically ill. There may also be evidence to suggest that piperacillin-tazobactam alone increases the risk of AKI.

Both abstracts retrospectively compared patients who received either vancomycin alone or the combination of vancomycin and piperacillin-tazobactam. In both studies, the rates of AKI were significantly lower in patients treated with vancomycin alone as compared to patients receiving both vancomycin and piperacillin-tazobactam.

Bottom line: Although the current evidence does not support a change in our clinical practice, more prospective studies exploring this topic are necessary.

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Category: Critical Care

Title: Anion Gap in DKA

Posted: 6/13/2012 by Mike Winters, MD (Updated: 1/27/2023)
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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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