UMEM Educational Pearls - By Mike Winters

Gastrointestinal Changes of Obesity that Complicate Critical Illness

  • Obesity predisposes patients to several gastrointestinal abnormalities that can cause, or complicate, critical illness.
  • Important abnormalities to keep in mind when managing a critically ill obese patient include:
    • Increased intra-abdominal pressure which predisposes to abdominal compartment syndrome
    • Increased incidence of nonalcoholic fatty liver disease which may lead to prolonged drug metabolism
    • Increased incidence of cholelithiasis which may result in pancreatitis or cholangitis

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Category: Critical Care

Title: Combination Therapy for Bacteremia

Keywords: staphylococcal aureus, aminoglycoside, monotherapy, combination therapy (PubMed Search)

Posted: 4/19/2011 by Mike Winters, MD (Updated: 9/27/2022)
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Combination Antimicrobial Therapy for Gram (+) Bacteremia

  • Bacteremia is a major cause of morbidity and mortality in the critically ill patient.
  • S.aureus remains a common isolate in patients with either hospital-acquired or community-acquired bacteremia.
  • In cases of suspected endocarditis due to S.aureus, traditional teaching has been to give an aminoglycoside (i.e. gentamicin) in combination with vancomycin or an antistaphylococcal penicillin.
  • Importantly, there is no strong evidence to support this combination in patients with suspected S.aureus bacteremia.
  • Furthermore, patients receiving the aminoglycoside combination have higher rates of renal impairment without any added clinical benefit.

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Aspiration Pneumonitis and Pneumonia

  • Aspiration of low pH gastric fluid or food matter is common in critically ill patients and often underdiagnosed.
  • Patients with aspiration initially develop a pneumonitis that, in some, can be complicated by bacterial pneumonia.  Up to 33% develop severe ALI/ARDS, with an associated 30% mortality rate.
  • Aspiration pneumonitis presents with hypoxia and a CXR demonstrating infiltrates in the dependent portion of the lungs.  Often, the degree of respiratory distress is worse than the CXR appearance.
  • Since it is challenging to differentiate aspiration pneumonia from aspiration pneumonitis, current recommendations suggest initiating empiric antibiotics with agents that have adequate Gram-negative coverage.  Routine coverage against anaerobic bacteria is not currently recommended, except in patients with severe periodontal disease and those with a lung abscess on CXR or CT.
  • Despite the initial inflammatory response, steroids are not indicated for patients with aspiration.

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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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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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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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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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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: Antibiotic Timing

Posted: 12/15/2010 by Mike Winters, MD (Updated: 9/27/2022)
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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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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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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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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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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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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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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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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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Category: Critical Care

Title: Hemostatic Therapy for ICH

Posted: 8/24/2010 by Mike Winters, MD (Updated: 9/27/2022)
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Hemostatic Therapy for ICH - Updated Guidelines

  • The AHA/ASA just published updated guidelines for the diagnosis and treatment of acute spontaneous intracerebral hemorrhage (ICH).
  • Regarding hemostatic therapy, new/revised recommendations from the 2007 AHA/ASA guidelines include:
    • Patients with severe thrombocytopenia or factor deficiency should receive platelets or factor replacement
    • Patients with ICH due to oral anticoagulants (warfarin) should receive intravenous vitamin-K and vitamin-K dependent factor replacement
      • Prothrombin complex concentrates (PCCs) are being increasingly used and are considered a reasonable alternative to FFP.  To date, studies have not shown improved outcome with PCCs.
      • Recombinant factor VIIa (rFVIIa) is not recommended as a sole agent for warfarin-related ICH
    • rFVIIa is not recommended in unselected patients
    • Usefulness of platelet transfusions for patients using antiplatelet medications is unclear and currently investigational.

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Category: Critical Care

Title: Drug-Induced Hypophosphatemia

Posted: 8/10/2010 by Mike Winters, MD (Updated: 9/27/2022)
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Drug-Induced Hypophosphatemia

  • Hypophosphatemia is seen in almost 30% of critically ill patients.
  • As discussed in a prior pearl, hypophosphatemia can result in respiratory failure along with cardiac and neurologic abnormalities.
  • Although common ED causes of hypophosphatemia include sepsis, hypothermia, and dialysis, don't forget about medications.
  • Medications that can cause significant hypophosphatemia in the critically ill (along with their mechanism) include:
    • Decreased GI intake: antacids, sucralfate
    • Transcellular shift: aspirin overdose, albuterol, catecholamines, insulin, and bicarbonate
    • Increased urinary excretion: diuretics, acetaminophen overdose, and theophylline overdose

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Hypocapnia and Brain Injury

  • Hypocapnia indirectly reduces cerebral blood volume through reductions in arterial cerebral blood flow.
  • Despite its continued and frequent use, hypocapnia can actually aggravate cerebral hypoxia through reductions in oxygen supply and increases in cerebral oxygen demand.
  • In addition to inducing further cerebral injury, hypocapnia can cause deleterious effects on the heart, lung, and GI tract.
  • To date, there is no evidence that hypocapnia improves outcome in patients with traumatic brain injury or acute stroke.
  • Induced hypocapnia in critically ill ED patients with acute brain injury should primarily be reserved for those with imminent brain herniation.

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