UMEM Educational Pearls - Critical Care

The Severely Hypoxemic ED Patient

  • Most define hypoxemia as a PaO2 < 60 mm Hg.
  • Perhaps a better definition of hypoxemia is a PaO2 that is associated with continued tissue hypoxia (rising lactate, low ScvO2), the need for vasopressor medications, or severe metabolic acidosis.
  • For ED patients that remain hypoxemic despite increased FiO2 and high levels of PEEP, consider the following rescue therapies:
    • Recruitment maneuvers - brief periods of high PEEP (35-50 cm H2O) or pressure-controlled breaths to reopen collapsed alveoli
    • High-frequency oscillatory ventilation - employs a high airway pressure to recruit closed alveolar segments
    • Prone positioning - believed to improve oxygenation through a redistribution of ventilation and perfusion
    • Extracorporeal membrane oxygenation

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Hemodynamic Monitoring in the Ventilated Patient

  • Consider pulse pressure variation (PPV) as a method to monitor volume responsiveness in your mechanically ventilated ED patients.
  • The theory behind PPV:
    • When a positive pressure breath is delivered via the ventilator, pleural pressure rises and causes a decrease in venous return, right heart filling, and right heart output.
    • Simultaneously, the positive pressure breath causes an increase in left heart filling and a decrease in left heart afterload.  This is reflected clinically as an increase in blood pressure.
    • Within a few beats, the decreased right heart output is transmitted to the left heart resulting in a decrease in blood pressure during expiration.
  • Patients who are volume depleted can have significant differences in blood pressure between inspiration and expiration - i.e. a large variation in pulse pressure.
  • PPV values > 12% have been shown to identify patients who are volume responsive.
  • Importantly, PPV works best in vented patients who have no spontaneous respiratory effort, are in sinus rhythm, and receiving 8 ml/kg tidal volumes.

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Category: Critical Care

Title: How good is the McConnell sign for diagnosing pulmonary embolism?

Keywords: Pulmonary embolism, PE, echocardiography, ultrasound, hemodynamics, McConnell sign, right ventricle (PubMed Search)

Posted: 2/15/2011 by Haney Mallemat, MD (Updated: 12/8/2022)
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  • McConnell sign is right ventricular (RV) free wall hypokinesis with normal apical contraction on echocardiography.
  • Finding McConnell sign has been associated with submassive and massive pulmonary embolism (PE) when moderate to high clinical suspicion exists. This is important if unstable patients are unable to tolerate other diagnostic studies.
  • After its description, the specificity of McConnell sign’s for PE has been questioned, as other pathologies can produce it (e.g., RV infarction and severe pulmonary HTN).
  • The paper referenced below retrospectively found that the sensitivity, specificity, positive predictive value, and negative predictive value of McConnell sign for diagnosing PE was 70, 33, 67, ad 36%, respectively.
  • Bottom line: The McConnell sign must be used with caution if used alone to diagnose PE; especially if thrombolytics are being considered.


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Acute LV Dysfunction in the Critically Ill

  • Approximately one-third of critically ill hospitalized patients develop acute LV dysfunction, most often due to a stress-induced cardiomyopathy.
  • In these patients, up to 25% develop an acute dynamic LV outflow tract obstruction.
  • Consider acute LV outflow tract obstruction in hypotensive patients with a new systolic ejection murmur in the left parasternal area.
  • Aggressive IVFs is central to the management of these patients with LV outflow tract obstruction.

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Category: Critical Care

Title: Critical illness and hemoglobin concentration

Keywords: hemoglobin, anemia, transfusions, hemorrhage, conservative, liberal, hemorrhaging (PubMed Search)

Posted: 2/1/2011 by Haney Mallemat, MD
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The optimal hemoglobin concentration during critical illness is unknown. Although a liberal transfusion strategy (Hb 10-12 g/dL) was once believed to be beneficial for hemodynamics, evidence suggests targeting a conservative strategy (Hb 7-9 g/dL) does not increase mortality, while the unnecessary transfusion of blood products can cause harm (transfusion associated lung injury, infection, etc.) in the non-hemorrhaging patient. 

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Valproic Acid in Status Epilepticus

  • In previous pearls, we have discussed the treatment of status epilepticus (SE) with first-line (benzodiazepines) and second-line agents (phenytoin/fosphenytoin).
  • Refractory SE is defined as the failure to respond to both first- or second-line antiepileptic medications.
  • Valproic acid is listed in many algorithms as a third-line agent for treating SE.
  • Avoid valproic acid in refractory SE patients who have hepatic disease or dysfunction.
  • Although rare, valproic acid can cause a fatal hepatotoxicity in these patients. 

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Category: Critical Care

Title: Testing for Brain Death

Keywords: Apnea test, brain death, brain stem death, coma, death, cardiopulmonary death (PubMed Search)

Posted: 1/17/2011 by Haney Mallemat, MD
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Brain death is the permanent absence of cerebral and brainstem functions (coma, absent pupillary reflexes, no spontaneous respiration, etc.). Legally, brain death is equivalent to cardiopulmonary death.

  • Prior to brain death testing, ensure the following:
  • SBP > 100, core temp >36 Celsius, and absent brainstem reflexes.
  • An identified cause of brain death.
  • No metabolic abnormalities or intoxication.
  • CNS insult on imaging.

If brain death is suspected, confirmation is necessary. The apnea test is most commonly used, evaluating for spontaneous breaths when disconnected from the ventilator. If apnea testing is not possible (e.g., ambiguous clinical exam or cardiopulmonary instability) ancillary testing is needed:

  • EEG
  • Evoked potentials
  • Cerebral angiography
  • CT Angiogram
  • MR Angiography
  • Transcranial Doppler
  • Nuclear Medicine 

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Dexmedetomidine for Sedation in Acute Neurologic Disease

  • Critically Ill patients with acute neurologic disease are managed daily in the ED.
  • Due to the need for frequent neurologic assessments, these patients can be challenging should they require sedation.
  • Dexmedetomidine, a selective alpha-2 adrenergic receptor agonist, has emerged as an alternative to traditional sedatives (i.e. opioids and benzodiazepines).
  • Dexmedetomidine provides sedation and anxiolysis, while producing little effect on level of arousal and cognitive function.  In essence, it reduces discomfort while permitting the patient to arouse for a neurologic examination.

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Category: Critical Care

Title: Posterior Reversible Encephalopathy Syndrome

Keywords: PRES, hypertensive crisis, seizures, visual loss, ecclampsia, hypertensive emergency, cyclopsporine, tacrolimus (PubMed Search)

Posted: 1/4/2011 by Haney Mallemat, MD
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Posterior reversible encephalopathy syndrome (PRES) is a syndrome of visual loss, headache, altered mental status, and seizures, typically with severe hypertension. PRES usually occurs with hypertensive encephalopathy or ecclampsia, although cyclosporin and tacrolimus use have been implicated. 

PRES is due to a combination of endothelial damage, impaired auto-regulation and increased cerebral perfusion pressure. Classic CT and MRI findings are parietal-occipital, cerebellar, or brainstem cortical and subcortical edema. 


Early recognition and symptomatic treatment is key; IV anti-hypertensives (hypertensive encephalopathy), anti-epileptics (seizures), IV magnesium and emergent delivery (ecclampsia), and discontinuing offending medications (cyclosporin and tacrolimus).  


With treatment, partial to complete recovery is normal, although residual neurological and visual deficits may persist.

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Vancomycin Dosing in the Critically Ill Obese Patient

  • Obesity related changes to drug metabolism and distribution can significantly impact the critically ill obese patient.
  • Many meds can either be underdosed or overdosed depending on which body weight (ideal vs. actual) is used.
  • With the increased incidence of MRSA infections, vancomycin is often included in the initial antibiotic selection for most critically ill ED patients.
  • Importantly, vancomycin is one of the most studied antibiotics in obese patients.
  • Recent guidelines recommend that an initial vancomycin dose of 25-30 mg/kg actual body weight be considered for any critically ill patient, with subsequent dosing dependent upon renal function and trough levels.

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Category: Critical Care

Title: Thrombocytopenia in the Critically-ill

Keywords: thrombocytopenia, critically0ill, sepsis, death, mortality, prognosis (PubMed Search)

Posted: 12/21/2010 by Haney Mallemat, MD
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The incidence and prevalence of thrombocytopenia in the ICU is poorly defined however, it has been found to be an independent predictor of death in the critically-ill. Increased mortality does not appear to be related to bleeding complications. On the other hand, survivors of critical illness tend to recover platelet faster as compared to non-survivors. 


Thrombocytopenia in the critically-ill is a marker for systemic inflammation/infection although the exact mechanisms are unknown. Common risk factors associated with thrombocytopenia in the ICU population are:



Renal failure

High-illness severity

Organ dysfunction


Bottom line:  Thrombocytopenia in the critically-ill is associated with increased mortality. 

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Category: Critical Care

Title: Antibiotic Timing

Posted: 12/15/2010 by Mike Winters, MD (Updated: 12/8/2022)
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The Importance of Antibiotic Timing for Sepsis and Septic Shock

  • Septic shock is perhaps the most common critical illness that emergency physicians manage.
  • In several studies, delays in initiating antibiotics for patients with septic shock were the strongest predictor of mortality.
  • Broad spectrum antibiotics should be administered ASAP (preferably within 60 minutes) to patients with septic shock. 
  • Selection of antibiotics should be based on the presumed source, the antibiogram at your institution, and the patient's risk factors for resistant organisms.

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Category: Critical Care

Title: Linezolid and Serotonin Syndrome

Keywords: Antibiotics, linezolid, serotonin syndrome, delirium, critical care (PubMed Search)

Posted: 12/7/2010 by Haney Mallemat, MD
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Linezolid is used for gram-positive infections resistant to conventional therapy (e.g., Vancomycin-resistant enterococcus and Methicillin Resistant Staph Aureus). Linezolid is an oxazolidinone, but more importantly it is a weak monoamine oxidase inhibitor (MAOI) and serotonin syndrome (e.g., altered mental status, neuromuscular abnormalities, autonomic instability) may occur when combined with selective serotonin re-uptake inhibitors (SSRIs) or with recent discontinuation of SSRI. 


Be aware that the following drugs can precipitate serotonin syndrome when combined with Linezolid:


Mirtazpine       Buproprion       Fentanyl

Trazodone       Buspirone         Bromocryptine

Levodopa        Lithium               Amphetamines

Cocaine           Codeine            Reserpine

Ergots               MAOI's





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Beware Trendelenburg Positioning in the Critically Ill Obese Patient

  • When inserting a central venous catheter (CVC) into the internal jugular or subclavian vein, clinicians often place patients in the Trendelenburg position to increase the size of the vein.
  • When possible, avoid Trendelenburg position for CVC placement in the morbidly obese patient.
  • These patients can quickly deteriorate in this position due to reduced lung volumes, increased right heart pressures, decreased cardiopulmonary reserve, and the effects in intra-abdominal pressure.

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Category: Critical Care

Title: Beware of Non-Convulsive Status Epilepticus

Keywords: Status epilepticus, non-convulsive, altered mental status, seizure, critical care, ICU, neurology (PubMed Search)

Posted: 11/23/2010 by Haney Mallemat, MD
Click here to contact Haney Mallemat, MD

Non-Convulsive Status Epilepticus (NCSE) is generally under reported. An ICU study found 10% admissions for altered mental status (AMS) were eventually diagnosed as NCSE.


- Include NCSE in the AMS differential

- NCSE may occur with or without convulsive seizures

- Difficult to distinguish from a post-ictal state (14% of convulsive seizures convert to  


- Reported mortality is up to 44%


Consider NCSE when:

- Seizure history / recent seizures

- Post-ictal period >1 hour

- Odd behaviors (e.g., chewing, blinking, personality change) and abnormal eye 

  movements (86% specific)

- AMS without structural, metabolic or traumatic etiology

- Patient intubated for status epilepticus 


If you are unsure but suspicious of NCSE order a STAT EEG.  Treat NCSE like a convulsive status.

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Positioning for Ventilated, Critically Ill Obese Patients

  • Up to one-quarter of patients in the ICU are obese, as defined by a BMI > 35 kg/m2
  • Obesity can significantly alter pulmonary physiology causing
    • reduced lung volumes
    • decreased compliance
    • abnormal ventilation to perfusion relationships
    • respiratory muscle inefficiency
  • For intubated obese patients, body position can affect ventilatory management
  • In the supine position, obese patients can have collapse of lung segments along with increased impedance of the diaphragm
  • Elevating the head of the bed to 30-45 degrees in intubated obese patients has been shown to improve tidal volumes and lower respiratory rates.

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Category: Critical Care

Title: Ocular sonography and elevated intracranial pressure

Keywords: ultrasound, ocular, sonography, intracranial pressure, optic nerve sheath, ICP (PubMed Search)

Posted: 11/9/2010 by Haney Mallemat, MD
Click here to contact Haney Mallemat, MD


Ocular sonography is a fast, simple, and non-invasive tool to detect elevated intracranial pressure (ICP) by measuring the optic nerve sheath diameter (ONSD). Several studies have shown a positive correlation between increased ONSD (>5.7mm) and elevated ICP (>20mmHg).  Although ultrasound may not replace CT or MRI to diagnose the cause of the increased ICP, its use as a triage tool can expedite these tests.


The technique:

  1. Use linear probe on closed eyelid.
  2. Identify the optic nerve sheath.
  3. Measure the optic nerve sheath, 3mm behind globe.
  4. Rotate probe 90 degrees and measure again.
  5. Average both diameters.

Please see the references below for more information and, as with any new technique please consult local experts prior to making clinical decisions

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Ventilation Pearls in the Post-Cardiac Arrest Patient

  • Some ventilation pearls from the recently released 2010 AHA guidelines include:
    • Set the tidal volume to 6-8 ml/kg ideal body weight
    • Titrate minute ventilation to achieve a PaCO2 between 40-45 mm Hg or PETCO2 between 35-40 mm Hg
    • Reduce the FiO2 to maintain SpO2 > 94%

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Category: Critical Care

Title: Long-term complications of ICU Delirium

Keywords: delirium, dementia, ICU, (PubMed Search)

Posted: 10/25/2010 by Haney Mallemat, MD (Updated: 12/8/2022)
Click here to contact Haney Mallemat, MD

Increasing literature demonstrates ICU delirium is bad. Delirium in mechanically ventilated patients is an independent predictor for long-term cognitive defects (e.g., managing money, following detailed instructions, reading maps, and developing dementia). The cited study found 80% of patients with ICU delirium had cognitive dysfunction at three months, and 70% had residual dysfunction at one year (33% had severe dysfunction).

You must be aggressive to prevent delirium:

-         Implement daily assessment tools (e.g., CAM-ICU)

-         Daily awakening and spontaneous breathing trials

-         Early patient mobilization

-         Aggressive pharmacological treatment of delirium

-         For more information:

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Ketamine for RSI in Hemodynamically Unstable ED Patients

  • Recall that ketamine acts as a sympathomimetic resulting in increases in heart rate, blood pressure, and ultimately cardiac output.
  • Because of its rapid transport across the blood-brain barrier, its sympathomimetic effects, and lack of significant adverse effects, ketamine is recommended by many organizations as a first line agent for RSI in unstable patients.
  • Important contraindications to ketamine include an acute coronary syndrome, aortic dissection, and acute heart failure.
  • Take Home Point: Consider using ketamine the next time you need to intubate a hypotensive, critically ill ED patient.

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