UMEM Educational Pearls - Critical Care

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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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:

Sepsis

Renal failure

High-illness severity

Organ dysfunction

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

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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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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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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.

Pearls:

- 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  

  NCSE)

- 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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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 P_aCO₂ between 40-45 mm Hg or P_ETCO₂ between 35-40 mm Hg
  • Reduce the F_iO₂ to maintain S_pO₂ > 94%

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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: www.icudelirium.org

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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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Heliox is a mixture of oxygen and helium resulting in a gas less dense than air. In asthma, airway resistance causes turbulent airflow which increases the work of breathing. Heliox reduces airway resistance by increasing laminar airflow. 

Benefits: 

Better lung mechanics

Improved nebulizer delivery

Few known side-effects/complications

Drawbacks:

Expensive

Contraindicated in hypoxemic patients.

Paucity of large prospective randomized trials.

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EMS in Maryland has REMOVED endotracheal medication administration from its ADULT protocols

This is due to:

• Unclear efficacy and need for a much higher dosage
• Ability to administer drugs via IO route
• Decrease reliance on intubation
  • chest compressions only CPR
  • BiPAP use
• Note this does not pertain to PEDIATRICS, where it is still included in its protocols

Respiratory Distress in the Ventilated ED Patient

• In the ventilated patient with respiratory distress, evaluation of peak and plateau pressures can help to identify the cause.
• Isolated increases in peak pressure suggest increased resistance to airflow and should prompt consideration of the following:
  • kinked or twisted ET tube
  • patient biting ET tube
  • obstructed ET tube
  • bronchospasm
  • lower airway obstruction
• Increases in plateau pressure suggest decreased pulmonary compliance and should prompt consideration of the following:
  • unilateral intubation
  • pneumothorax
  • pulmonary edema
  • worsening pneumonia
  • abdominal HTN/compartment syndrome

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While you should always involve ID consultants when managing critically-ill HIV/AIDS patients on HAART, consider this; sub-therapeutic levels of anti-retrovirals may promote HIV resistance, potentially invalidating a class of drug for future use. Therefore, it may be advantageous to discontinue the drug(s) during critical-illness to avoid resistance. 

Two examples leading to sub-therapeutic HAART levels in critical-illness:

1. Reduced absorption of PO medications from bowel wall edema and/or decreased splanchnic perfusion.
2. Interactions with HAART medications and the multitude of other drugs administered in the ICU.

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Life-threatening Bleeding in Hemophilia A Patients

• Although an infrequent occurrence, patients with Hemophilia A can present with life-threatening hemorrhage (e.g. ICH).
• Recall that normal clotting factor levels range from 50-150 IU/dL - reported by the lab as 50-150%.
• Life-threatening bleeding requires Factor VIII levels between 80-100%.  In general, each unit of FVIII/kg raises plasma levels by 2%.
• Recombinant Factor VIII products are preferred over plasma derived concentrates or blood products and are dosed as:
  • FVIII - 50 IU/kg loading dose followed by infusion of 3 IU/kg/hr
• In the event you don't have access to recombinant or plasma derived FVIII concentrates, cryoprecipitate (contains FVIII) can be used.

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(Sorry for the previously mislabeled pearl...)

Necrotizing soft tissue infections (NSTI) are on the rise and, despite improved surgical and critical care, over the years there has only been a mild reduction in mortality. Survival is associated with early diagnosis and treatment. Unfortunately, NSTI are not always obvious because deeper tissues made be involved first. Despite a validated scoring system and better radiology, our clinical suspicion still rules and relies on a meticulous history and physical exam. 

Here are some subtle signs of NSTI:

Pain out of proportion to exam

Edema beyond region of erythema

Skin anesthesia

Skin erythema and/or hyperthermia

Epidemolysis

Skin bronzing

If NSTI is suspected, be vigilant! Start broad-spectrum antibiotics, begin appropriate resuscitation and involve your surgeons early.

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Pulmonary Contusion and Ventilator Management

• Pulmonary contusion is the most common injury in blunt thoracic trauma.
• Patients with pulmonary contusion often present with hypoxia, hypercarbia and increased work of breathing.
• Importantly, patients with pulmonary contusion have a low cardiopulmonary reserve.  Maintain a low threshold for initiating mechanical ventilation is these patients.
• When starting mechanical ventilation, think about the following:
  • Patients are at high risk for developing ARDS
  • Most centers use a low tidal volume ventilatory strategy
  • Higher levels of PEEP may be necessary to recruit collapsed alveoli
  • High frequency oscillatory ventilation (HFOV) and airway pressure release ventilation (APRV) are modes of ventilation that are gaining in popularity for ventilating patients with pulmonary contusions.

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Hyponatremia plagues many neurosurgical patients due to the syndrome of inappropriate secretion of ADH (SIADH) or the cerebral salt wasting syndrome (CSW). Both diseases may appear similar (hyponatremia, increased urine osmolarity, increased urine sodium, normal adrenal, renal and thyroid function), but there is one BIG difference. Patients with SIADH are euvolemic or hypervolemic (excess ADH causes fluid retention) whereas patients with CSW are fluid depleted (impaired renal handling of sodium and water). To differentiate, look for signs of hypovolemia: orthostatics, dry mucus membranes, hemoconcentration, pre-renal azotemia, and/or hemodynamics (IVC collapse anyone?).

Bottom line: Distinguish SIADH from CSW because the treatments are exact opposites:

SIADH: Fluid restrict

CSW: Give water and salt (i.e., 0.9% saline)

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