UMEM Educational Pearls - By Mike Winters

Seizures in the Critically Ill

• Seizures are a common complication in medical and surgical patients commonly arising from coexisting conditions associated with critical illness
• Most seizures in the critically ill are generalized convulsions rather than focal
• The majority of seizures occur in patients without a pre-existing history of seizure disorder
• Common causes of seizures in the critically ill include sepsis, cardiovascular disease, metabolic abnormalities, medications, and drug intoxication/withdrawal
• Metabolic abnormalities account for 30 -35% of causes
• The most common metabolic abnormalities include hyponatremia, hypocalcemia, hypophosphatemia, uremia, and hypoglycemia
• Be sure to check these labs in ICU patients with a seizure

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Auto-PEEP in the non-COPD patient

• In previous pearls we have discussed the concept of auto-peep in patients with expiratory flow limitation (asthma and COPD)
• Unexpected auto-peep can also occur in up to 35% of patients without asthma or COPD
• In these patients, auto-PEEP typically occurs with high minute ventilations (> 20 L/min) with shortened exhalation times or if exhalation is blocked (blocked ETT, exhalation valve, or PEEP valve)
• Recall that auto-PEEP increases the work of breathing, worsens gas exchange, and can cause hemodynamic compromise 
• Treatment of auto-PEEP can be as follows:
  • Change ventilator settings
    • increase expiratory time
    • decrease respiratory rate
    • decrease tidal volume
  • Reduce ventilatory demand
    • reduce anxiety, pain, fever with sedatives
  • Reduce flow resistance
    • large-bore ETT
    • frequent suctioning
  • Apply external PEEP

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Ventilator Therapy for ED Patients with ARDS

• As we manage critically ill patients for longer periods of time, it is likely that many of us will manage patients who develop ARDS
• Current mortality for patients with ARDS ranges from 30-40%
• ED treatment for patients with ARDS includes treating the inciting event, supportive critical care, and ventilator management
• Current ventilator management in patients with ARDS includes:
  • avoiding alveolar overdistention (tidal volumes of 6 ml/kg)
  • maintaining F_iO₂ < 60% (mitigates oxygen toxicitty)
  • PEEP to prevent alveolar derecruitment (levels of 10-15 cm H₂O)
  • permissive hypercapnea

 Influenza and the Critically Ill

• It is that time of year again to be vigilant for cases of influenza
• Influenza is not benign and causes > 40,000 deaths per year and is the 7th leading cause of death in the US
• In the critically ill, the most severe disease occurs in patients > 65 and those with underlying cardiopulmonary disease
• Critically ill patients with influenza can present with fever, cough, bilateral interstitial infiltrates, hypoxemia, and leukopenia
• Other serious complications include myocarditis, encephalitis, and Reye syndrome
• Amantadine and rimantadine should no longer be used, as the resistance has risen to > 90% in some populations
• Oseltamivir (PO) and zanamivir (powder/inhalation) are the approved neuraminidase inhibitors; both decrease the severity and duration of illness; should be given as early as possible, preferably within 36 hours

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Can You Rely on Your Clinical Impression to Exclude SBP?

• SBP is an important can't miss diagnosis, as the mortality rate even for treated patients is approximately 20%
• The incidence of SBP ranges from 2.5% (clinic setting) to 12% of all patients admitted with decompensated cirrhosis
• SBP is diagnosed by a neutrophil count > 250 or a positive ascitic fluid culture obtained via paracentesis

• Can our clinical impression exclude SBP without performing a paracentesis? Unfortunately, the answer is NO.
• Sensitivity of physician clinical impression is just about 75%, with a specificity of 34%
• Fever is uncommon in patients with SBP (sensitivity as low as 17%)
• Take Home Point: only a diagnostic paracentesis can reliably exclude SBP in patients admitted for decompensated cirrhosis

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Tension gastrothorax?

• Tension gastrothorax is a life threatening condition characterized by herniation of the stomach through a defect in the diaphragm with compression of the mediastinal contents
• Although many cases occur in pediatric patients (secondary to congenital defects), adults with a history of diaphragmatic injury are at risk (also patients with a type III or IV hiatal hernia)
• The clinical presentation is the same as a tension pneumothorax - hypotension, tachycardia, hypoxia, JVD, and decreased breath sounds
• CXR appearance can be very similar to tension pneumothorax, however, the treatment is substantially different
• Needle decompression and tube thoracostomy are contraindicated, as this may cause visceral perforation
• The treatment of choice is NGT (or OGT) decompression followed by surgical repair

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Subcutaneous Insulin in the Critically Ill

• Although intensive insulin therapy in the critically ill remains controversial and a matter of much debate, hyperglycemia is common in the critically ill ED patient
• Hyperglycemia is associated with worse outcomes in this patient population
• When treating hyperglycemia in the critically ill ED patient, use caution with subcutaneous insulin
• Absoprtion of insulin administered subcutaneously is slow, erratic, and highly variable often due to poor perfusion, hypotension, and/or vasopressor therapy
• In these patients, IV insulin is a better route of administration and leads to more reliable control of hyperglycemia
• Recall that the onset of action of insulin given IV is 10 - 30 minutes, with a duration of action of about 1 hour

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AIDS: coming to a critically ill patient in your ED

• Acute intestinal distress syndrome (AIDS) is a recently coined term used in the continuum of intraabdominal hypertension (IAH) to abdominal compartment syndrome (ACS)
• In previous pearls we have discussed the importance of IAH in the critically ill and how to measure intraabdominal pressure (IAP)
• Recall that IAH is defined as a sustained elevation of IAP > 12 mmHg
• The focus of attention is shifting to "secondary ACS" - it is highly prevalent in the critically ill and is independently associated with increased mortality
• Sepsis is a cause of secondary ACS and is the most likely condition we will encounter in our critically ill patient population
• Current recommendations suggest that IAP be measured daily in patients at risk for IAH (i.e. the septic ED patient)

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Health care-associated pneumonia

• Health care-associated pneumonia (HCAP) is a distinct entity
• HCAP includes any patient with pneumonia and 1 or more of the following:
  • hospitalization for 2 or more days in an acute care facility within the preceeding 90 days
  • nursing home patients
  • patients of long-term care facilities
  • patients who attend a hospital or hemodialysis clinic
  • patients who received IV antibiotics, chemotherapy, or wound care within 30 days of infection
• Data indicate that the mortality for HCAP is higher than CAP
• The most common organisms in HCAP include S.aureus, P.aeruginosa, Klebsiella species, Haemophilus species, and Escherichia species
• An initial recommended antibiotic regimen includes a combination of an antipseudomonal cephalosporin plus a fluoroquinolone plus an agent active against MRSA

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Intraabdominal Hypertension and the Critically Ill

• Intraabdominal hypertension (IAH) is increasingly recognized in a wide variety of critically ill patients and is associated with significant morbidity and mortality
• Normal intraabdominal pressure (IAP) is 5 - 7 mm Hg
• IAH is defined as the sustained elevation in IAP of at least 12 mm Hg
• Physical exam is inaccurate in detecting IAP with sensitivities of 40-60%
• The most common method of measuring IAP is intravesicular (bladder)
• Importantly, IAP should be measured at end-expiration after ensuring that abdominal muscle contractions are absent, with the patient in the supine position, and with the transducer zeroed in the midaxillary line at the level of the iliac crest

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Bicarbonate for severe lactic acidosis from shock?

• In critically ill patients, one of the most common causes of acidosis is hypoperfusion induced lactic acidosis
• Importantly, the source of lactic acid during hypoperfusion/shock is intracellular, and the intracellular compartment is not readily accessible to extracellular bicarb
• Exogenous bicarbonate will certainly raise extracellular pH but does not readily correct intracellular acidosis
• This increase in pH is transient and typically lasts approximately 30 minutes
• In studies to date, exogenous bicarbonate did raise pH, serum bicarbonate concentrations, and P_aCO₂ but importantly did not improve cardiac output, mean arterial pressure, or sensitization to catecholamines
• Take Home Point: Based on available literature, there is no utility to giving bicarbonate in hypoperfusion induced lactic acidosis when the pH is > 7.0

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 Phentolamine for vasopressor extravasation

I was recently informed of a case from an another institution in which a patient was started on a vasopressor medication via a peripheral IV while attempts at central access where attempted.  The patient unfortunately suffered permanent extremity ischemia due to significant extravasation of the vasopressor medication into the soft tissue.

• Phentolamine is reportedly the antidote for vasopressor extravasation into the skin and soft tissues (the evidence is not robust and limited primarily to case reports and animal data)
• Phentolamine is a non-specific alpha-blocking agent that inhibits vasoconstriction and theoretically improves blood flow through the affected area
• Take 5-15 mg of phentolamine and mix in 10 mL of normal saline - inject this into the affected area as soon as possible
• Give the patient concurrent IVFs in the event of some systemic absorption

PEEP in Nonhypoxemic Respiratory Failure

• Patients with ALI/ARDS typically receive PEEP to improve oxygenation
• Patients without ALI/ARDS, however, receive PEEP less frequently (some recent reports indicate that < 50% of these patients receive PEEP)
• A recent study by Spanish investigators found that the use of PEEP (5 - 8 cm H₂0) in nonhypoxemic patients decreased the incidence of ventilator-associated pneumonia and decreased the number of patients who developed hypoxemia
• Interestingly, no differences were found in hospital mortality, duration of mechanical ventilation, or ICU LOS
• Take Home Point: In nonhyoxemic intubated patients, the addition of 5-8 cm H₂0 of PEEP is a reasonable practice and may be beneficial in preventing VAP (pending further study)

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Pressure Regulated Volume Control (PRVC)

• PRVC is a mode of mechanical ventilation that combines both volume and pressure control modes
• The main advantage to PRVC is that the tidal volume / minute ventilation is guaranteed while controlling airway pressures, thereby reducing the risk of ventilator induced lung injury
• In PRVC, the ventilator delivers a pressure-controlled breath, but tidal volume is the key setting
• The ventilator will automatically adjust inspiratory pressures until the desired TV is achieved
• When using PRVC you need to set: target TV, RR, peak pressure alarm, inspiratory time, FiO2, and PEEP

Post-intubation deterioration?  Remember DOPE

• The pneumonic DOPE can help you remember the most common causes of post-intubation hypoxia or deterioration
• Displacement: check the endotracheal tube for displacement (right mainstem) or dislodgement
• Obstruction: check the ETT for obstruction (mucous plug, kink in ventilator tubing)
• Pneumothorax - get an xray
• Equipment failure(unusual): disconnect patient from the ventilator and bag manually   

The Importance of Plateau Pressure

• Alveolar overdistention is a precursor to the development of acute lung injury (ALI)
• Plateau pressure is a measurement of alveolar overdistention, and is the pressure equilibration between the airways and the alveoli
• Plateau pressure is measured by using an inspiratory hold (for at least 3 seconds) at the end of inspiration
• Based on available data, you want to maintain the plateau pressure < 30 cm H₂O
• Remember that patients should be heavily sedated to obtain this measurement - any patient-ventilator asynchrony may provide inaccurate information

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Mechanical Ventilation in Asthma

• Approximately 25,000 asthmatics are intubated each year
• Mismanaged mechanical ventilation in asthma carries significant morbidity and mortality
• One of the primary goals of ventilating the asthmatic is to allow for lung deflation
• The most effective way to allow for lung deflation, and reduce hyperinflation, is to reduce minute ventilation (TV x RR)
• Initial tidal volume settings should be 6 ml/kg of predicted body weight; if plateau pressures are > 30 cm H₂O tidal volume should be decreased to 4 - 5 ml/kg
• Reduced respiratory rates will also allow longer exhalation times; initial recommended rates are 6 - 8 breaths per minute
• If plateau pressures are still high despite lowering tidal volume and respiratory rate, you can then shorten the inspiratory time to allow for longer exhalation

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 Noninvasive Ventilation Pearls

• Multiple studies support the use of noninvasive positive pressure ventilation (NPPV) in acute exacerbations of COPD, acute cardiogenic pulmonary edema, and immunocompromised patients (organ transplant) with hypoxic respiratory failure.
• The timing of NPPV initiation is important.  NPPV should be started as soon as possible, as delays increase the likelihood of intubation
• The best predictor of success is a favorable response to NPPV within the first 1 to 2 hours
  • reduction in respiratory rate
  • improvement in pH
  • improved oxygenation
  • reduction in PaCO2
• Also crucial to NPPV success is a well fitting interface (mask)
• Although patients report greater comfort with nasal masks, they also permit more air leakage through the mouth and have been associated with a higher rate of initial intolerance in the acute setting.
• For acute applications of NPPV in the ED, a full face mask is preferred 

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Hypotension begins at 110 mmHg?

• Many of us use the historical SBP cut-off point of 90 mmHg or less to identify hypotension and shock
• Importantly, there is no data to support this arbitrary value
• Particularly in older patients, hypotension, hypoperfusion, and increased mortality may begin sooner than previously realized
• In this study of over 80,000 patients from the National Trauma Data Bank, a SBP < 110 mmHg was found to be more clinically relevant for identifying hypotension and hypoperfusion
• Take Home Point: strongly consider raising your threshold for identifying hypotension and initiating resuscitation, especially in the older trauma patient.

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Recent Articles from the Critical Care Literature

Duration of adrenal insufficiency following a single dose of etomidate in critically ill patients