UMEM Educational Pearls - Critical Care

Question

Elderly patient who originally presented for severe pancreatitis now intubated for worsening hypoxemia. CXR is shown below, what's the diagnosis?  

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HIV, ART, and the ICU

• Though survival has dramatically improved for patients with HIV, there has been no decrease in the quantity of ICU admissions for this select patient population.
• One of the most common reasons for ICU admission is now adverse effects of antiretroviral therapy (ART).
• When managing a critically ill HIV patient in the ED or ICU, consider the following effects of ART as an etiology:
  • Lactic acidosis
    • Seen with nucleoside reverse transcriptase inhibitors (NRTIs): greatest risk with didanosine, stavudine, and zidovudine
    • Presentation: fatigue, malaise, vomiting, abdominal pain, hepatomegaly
    • Lactate often > 10 mmol/L
  • Abacavir hypersensitivity
    • Usually within first 6 weeks of drug initiation
    • Presentation: rash, fever, shortness of breath, vomiting, abdominal pain
    • Can rapidly progress to cardiovascular collapse

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COPD treatment guidelines (e.g., GOLD) recommend 10-14 days of steroid therapy following a COPD exacerbation to prevent recurrences; the supporting data is weak.

A recent noninferiority trial (here) compared patients with a severe COPD exacerbation who received either a 5-day course (n=156) or 14-day course (n=155) of prednisone 40mg.

The results were:

• No significant reduction in time until the next exacerbation (primary end-point)
• No significant difference in mortality, incidence of mechanical ventilation, FEV1, or dyspnea scores (secondary end-points)

What you need to know:

• This was a non-inferiority trial, which has limitations
• All subjects received broad-spectrum antibiotics and an initial dose of IV steroid
• Surprisingly, there were no differences between groups with respect to steroid complications (e.g., hyperglycemia, hypertension, etc.)

Bottom-line: 5 days of prednisone may be as effective as 14-days for COPD exacerbations.

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Hydroxyethyl starch (HES) is a colloid used for volume resuscitation in critically-ill patients.

Previous studies (click here) have compared crystalloids to HES during fluid resuscitation and have demonstrated that HES has an increased cost with more adverse effects. Adverse effects may include:

• Coagulopathy
• Acute kidney injury
• Increased mortality

In the United States, the Federal Drug Administration published a warning on June 24^th 2013 with respect to the use of HES in critically ill adult patients. Specifically, it warned about the use of HES in patients,

• with sepsis
• with pre-existing kidney injury
• admitted to the ICU
• undergoing heart surgery with cardiopulmonary bypass

If a decision to use HES is made, the FDA warning advises to:

• discontinue use of HES at the first sign of renal injury or coagulopathy
• continue to monitor renal function for at least 90 days (all patients)

Bottom line: With an increased cost and evidence of harm compared to crystalloids, it appears the indications for use of HES are rapidly declining.

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CVP and Fluid Responsiveness

• Central venous pressure (CVP) has been used over the last 50 years to assess volume status and fluid responsiveness in critically ill patients.
• Despite widespread practice habit, CVP has not been shown to reliably predict fluid responsiveness in the critically ill.
• In a recent updated meta-analysis, Marik et al reviewed 43 studies, totaling over 1800 patients.
  • 57% of patients were fluid responders
  • The mean CVP was 8.2 mm Hg for fluid responders and 9.5 mm Hg for non-responders
  • For studies performed in ICU patients, the correlation coefficient for CVP and change in cardiac index was just 0.28.
• Bottom line: Current literature does not support the use of CVP as a reliable marker of fluid responsiveness.

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Keep Immune Thrombocytopenic Purpura (ITP) in your differential for patients with thrombocytopenia and evidence of bleeding. Although ITP has classically been described in children, it can occur in adults; especially between 3^rd- 4^th decade.

Thrombocytopenia leads to the extravasation of blood from capillaries, leading to skin bruising, mucus membrane petechial bleeding, and intracranial hemorrhage.

ITP occurs from production of auto-antibodies which bind to circulating platelets. This leads to irreversible uptake by macrophages in the spleen. Causes of antibody production include:

• Medication exposure
• Infection (usually viral), including HIV and hepatitis
• Immune disorders (e.g., lupus)
• Pregnancy
• Idiopathic

Suspect ITP in patients with isolated thrombocytopenia on a CBC without other blood-line abnormalities. Abnormality in other blood-line warrants consideration of another diagnosis (e.g., leukemia).

ITP cannot be cured; treatments include:

• Steroid to suppress antibody production (first-line therapy)
• Intravenous immunoglobulin (IVIG)
• IV Rho immunoglobulin (for Rh+ patients only)
• Rituximab +/- dexamethasone
• Splenectomy (rare cases of massive hemorrhage refractory to pharmacologic treatment)

Rhabdomyolysis in the Critically Ill

• Rhabdomyolysis can be disastrous in the critically ill patient, resulting in metabolic acidosis, life-threatening hyperkalemia, acute kidney injury, and acute renal failure (ARF).  In fact, mortality can be as high as 60% for those that develop ARF secondary to rhabdomyolysis.
• Although creatine kinase (CK) is a sensitive marker of muscle injury and used for diagnosis, it is actually the presence of myoglobinuria that results in ARF.
• Current guidelines recommend treatment when the CK level is > 5000 U/L.
• The mainstay of treatment remains aggressive fluid resuscitation with crystalloids.
• The administration of bicarbonate to alkalinize the urine, diuretics to increase urine output, and osmotic agents (mannitol) to augment urine output remain controversial and are not supported by current literature.

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Therapeutic hypothermia (TH) following out-of-hospital cardiac arrest (OHCA) has increasingly been utilized since it was first described. TH following in-hospital cardiac arrest (IHCA), on the other hand, is not as commonplace or consistent despite a recommendation by the American Heart Association (AHA).

A recent prospective multi-center cohort-study demonstrated that of 67,498 patients with return of spontaneous circulation (ROSC) following IHCA only 2.0% of patients had TH initiated; of those 44.3% did not even achieve the target temperature (32-34 Celsius). 

The factors found to be most associated with instituting TH were:

• Younger patients
• Admission to non-ICU units
• Arrests occurring Monday through Friday (as compared to weekends)
• Arrests within teaching hospitals (as compared to non-teaching institutions)

Bottom-line: Hospitals should consider instituting and adhering to local TH protocols for in-house cardiac arrests.

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End-expiratory Occlusion Test

• Volume expansion is a cornerstone of resuscitation for circulatory failure.
• As discussed in previous pearls, only 50% of unstable critically ill patients respond to fluid therapy.  For the 50% that don't respond, additional fluids may increase morbidity and mortality.
• In recent years, there has been tremendous focus on dynamic markers of fluid responsiveness, including respirophasic changes in IVC diameter, passive leg raising, and pulse pressure variation (PPV).
• An additional dynamic marker of fluid responsiveness is the end-expiratory occlusion test.
• Unlike PPV, this test can be performed on patients with spontaneous breathing activity and those with cardiac arrhythmias.
• Recent literature indicates that a 5% increase in cardiac output during a 15-second end-expiratory occlusion test predicts a positive response to a 500 ml saline infusion.

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The Macklin Effect

Pneumomediastinum (click here for image) may be caused by many things:

1. Esophageal perforation (e.g., complication from EGD)
2. Tracheal / Bronchial injury (e.g., trauma, complication of bronchoscopy, etc.)
3. Abdominal viscus perforation with translocation of air across the diaphragmatic hiatus
4. Air may reach mediastinum along the fascial planes of the neck.
5. Alveolar rupture, also known as the "Macklin Effect"

The "Macklin Effect" is typically a self-limiting condition leading to spontaneous pneumomediastinum and massive subcutaneous emphysema after the following:

1. Alveolar rupture from increased alveolar pressure (e.g., asthma, blunt trauma, positive pressure ventilation, etc.)
2. Air released from alveoli dissects along broncho-vascular sheaths and enters mediastinum
3. Air may subsequently track elsewhere (e.g., cervical subcutaneous tissues, face, epidural space, peritoneum, etc.)

Pneumomediastinum secondary to the Macklin effect frequently leads to an extensive workup to search for other causes of mediastinal air. Although, no consensus exists regarding the appropriate workup, the patient's history should guide the workup to avoid unnecessary imaging, needless dietary restriction, unjustified antibiotic administration, and prolonged hospitalization.

Treatment of spontaneous pneumomediastinum includes:

• Supplemental oxygen and observation for airway obstruction secondary to air expansion within the neck
• Avoiding positive airway pressure, if possible
• Avoiding routine chest tubes (unless significant pneumothorax is present)
• Administering prophylactic antibiotics are typically unnecessary
• Ordering imaging as needed

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Monitoring Hyperosmolar Therapy

• Hyperosmolar therapy (mannitol or hypertonic saline) is commonly used in the treatment of neurocritical care paitents with elevated ICP.
• When administering mannitol, guidelines recommend monitoring serum sodium and serum osmolarity.  Though targets remain controversial, most strive for a serum sodium of 150-160 mEq/L and a serum osmolarity between 300 - 320 mOsm/L.
• Unfortunately, serum osmolarity is a poor method to monitor mannitol therapy.
• Instead of serum osmolarity, follow the osmolar gap.  It is more representative of serum mannitol levels and clearance.  If the osmolar gap falls to normal, the patient has cleared mannitol and may be redosed if clinically indicated. 

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Fluid boluses are often administered to patients in shock as a first-line intervention to increase cardiac output. Previous literature states, however, that only 50% of patients in shock will respond to a fluid bolus. 

Several validated techniques exist to distinguish which patients will respond to a fluid bolus and which will not; one method is the passive leg raise (PLR) maneuver  (more on PLR here). A drawback to PLR is that it requires direct measurement of cardiac output, either by invasive hemodynamic monitoring or using advanced bedside ultrasound techniques.

Another technique to quantify changes in cardiac output is through measurement of end-tidal CO2 (ETCO2). The benefits of measuring ETCO2 is that it can be continuously measured and can be performed non-invasively on mechanically ventilated patients.

A 5% or greater increase in end-tidal CO2 (ETCO2) following a PLR maneuver has been found to be a good predictor of fluid responsiveness with reliability similar to invasive measures.

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Neuromuscular Blocking Agents in the Critically Ill

• NMBAs are used in critically ill patients for RSI, patient-ventilator asynchrony, reducing intra-abdominal pressure, reducing intracranial pressure, and preventing shivering during therapeutic hypothermia.
• There are a number of alterations in critical illness that affect the action of NMBAs
  • Electrolyte abnormalities
    • Hypercalcemia: decreases duration of blockade
    • Hypermagnesemia: prolongs duration of blockade
  • Acidosis: can enhance effect of nondepolarizing agents
  • Hepatic dysfunction: prolongs effects of vecuronium and rocuronium
• In addition, there are a number of medications that may interact with NMBAs
  • Increased resistance: phenytoin and carbamazepine
  • Prolongs effect: clindamycin and vancomycin
• Key complications of NMBAs in the critically ill include:
  • ICU-aquired weakness (controversial)
  • DVT: NMBAs are one of the strongest predictors for ICU-related DVT
  • Corneal abrasions: prevalence up to 60%

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Necrotizing fasciitis (NF) is a rapidly progressive bacterial infection of the fascia with secondary necrosis of the subcutaneous tissue. In severe cases, the underlying muscle (i.e., myositis) may be affected.

Risk factors for NF include immunosuppression (e.g., transplant patients), HIV/AIDS, diabetes, etc.

There are three categories of NF:

• Type I (poly-microbial infections)
• Type II (Group A streptococcus; sometimes referred to as the “flesh-eating bacteria)
• Type III (Clostridial myonecrosis; known as gas gangrene)

In the early stage of disease, diagnosis may be difficult; the physical exam sometimes does not reflect the severity of disease. Labs may be non-specific, but CT or MRI is important to diagnose and define the extent of the disease when planning surgical debridement.

Treatment should be aggressive and started as soon as the disease is suspected; this includes:

• Aggressive fluid and/or vasopressor therapy
• Broad spectrum antibiotics covering for gram-positive, gram-negative, and anaerobic bacteria; clindamycin should be added initially as it suppresses certain bacterial toxin formation
• Emergent surgical consult for debridement
• Once the patient is stable, other treatments may include intravenous immunoglobulin and hyperbaric oxygen therapy

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Massive Transfusion Pearls

• As discussed in previous pearls, massive transfusion (MT) is defined as the transfusion of at least 10 U of packed red blood cells (PRBCs) within 24 hours.
• While the optimal ratio of PRBCs, FFP, and platelets is not known, most use a 1:1:1 ratio.
• Though scoring systems have been published to identify patients who may benefit from MT (ABC, TASH, McLaughlin), they have not been shown to be superior to clinical judgment.
• A few pearls when implementing massive transfusion for the patient with traumatic shock:
  • Monitor temperature and aggressively treat hypothermia.
  • Monitor fibrinogen levels and replace with cryoprecipitate if needed.
  • Monitor calcium and potassium.  MT can induce hypocalcemia and hyperkalemia.

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Recent advances in resuscitation science have enabled emergency physicians to identify factors associated with good neurologic and survival outcomes. Cases of persistent ventricular dysrhythmia (VF or VT) present a particular challenge to the critical care provider. The evidence base for interventions in shock refractory ventricular VF mainly consists of case reports and retrospective trials, but such interventions may be worth considering in these difficult resuscitation situations:

1. Double sequential defibrillation
-For shock-refractory VF, 2 sets of pads are placed (anterior/posterior and on the anterior chest wall). Shocks are delivered as "closely as possible."^1,2

2. Sympathetic blockade in prolonged VF arrest
-"Eletrical storm," or incessant v-fib, can complicate some arrests in the setting of VF. An esmolol bolus and infusion may be associated with improved survival.³  Left stellate ganglion blockade has been identified as a potential treatment for medication resistant VF.⁴

3. Don't forget about magnesium! 
-May terminate VF due to a prolonged QT interval 

4. Invasive strategies
-Though resource intensive, there is limited experience with intra-arrest PCI and extracorporeal membrane oxygenation. Preestablished protocols are key to selecting patients who may benefit from intra-arrest PCI and/or ECMO. ⁵

5. Utilization of mechanical CPR devices 
-Though mechanical CPR devices were not officially endorsed by the AHA/ECC 2010 guidelines, there's little question that mechanical compression devices address the complication of provider fatigue during ongoing resuscitation. 

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Hormonal Dysfunction in Neurologic Injury

• In the critically ill patient with neurologic injury (SAH, TBI), the initial treatment focus is to maintain adequate cerebral perfusion pressure, control intracranial pressure, and limit secondary injury.
• Once stabilized, however, it is important to consider endocrine dysfunction in the brain injured patient.
• Endocrine dysfunction is common in neurologic injury and may lead to increased morbidity and mortality.  In fact, over half of SAH patients develop acute dysfunction of the HPA, resulting in low growth hormone, ACTH, and TSH. 
• In addition to hormonal dysfunction, sodium abnormalities (i.e. hyponatremia) are present in up to 80% of critically ill SAH patients.
• Consider hormonal replacement therapy (or hypertonic saline in cases of severe hyponatremia) for patients with evidence of endocrine dysfunction.  For some, this therapy can be life-saving.

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There are several reasons why a mechanically ventilated patient may decompensate post-intubation. Immediate action is often needed to reverse the problem, but it can be difficult to remember where to start as the vent alarm is sounding and the patient is decompensating.

Consider using the mnemonic “D.O.P.E.S. like D.O.T.T.S.” to assist you in first diagnosing the problem (D.O.P.E.S.) and then fixing the problem (D.O.T.T.S.). You can view an entire lecture on the Crashing Ventilated Patient here.

Step 1: Could this decompensation be secondary to D.O.P.E.S.?

• Displaced ET tube / ET tube cuff not inflated or has a leak
• Obstruction of ET tube
• Pneumothorax
• Equipment malfunction (disconnection of the ventilator, incorrect vent settings, etc.)
• Stacking (breath stacking / Auto- PEEP; click here for a review)

Step 2: Fix the problem with D.O.T.T.S.

• Disconnect – Disconnect patient from the ventilator
• Oxygen – Oxygenate patient with a BVM and feel for resistance as you bag
• Tube position / function – Did the ET tube migrate? Is it kinked or is there a mucus plug?
• Tweak the vent – Are the settings correct for this patient?
• Sonogram (ultrasound) – Sonogram to look for pneumothorax, mainstem intubation, etc. 

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Extubating in the ED

• With the increasing LOS for many of our intubated critically ill ED patients, it is possible that select patients may be ready for extubation while still in the ED.
• Patients who remain intubated unnecessarily are at increased risk for pneumonia, increased hospital LOS, and increased mortality.
• To be considered for extubation, patients should meet the following criteria:
  • The condition that resulted in intubation is improved or resolved
  • Hemodynamically stable (off pressors)
  • P_aO₂/F_iO₂ > 200 with PEEP < 5 cm H₂O
• If these criteria are met, perform a spontaenous breathing trial (SBT).
  • Discontinue sedation
  • Adjust the ventilator to minimal settings: pressure support or CPAP (5 cm H₂O) or use a T-piece.
  • Perform the trial for at least 30 minutes.
  • If the patient develops a RR > 35 bpm, S_pO₂ < 90%, HR > 140 bpm, SBP > 180 mm Hg or < 90 mm Hg, or increased anxiety, the SBT ends and the patient should remain intubated.
• Before removing the endotracheal tube, be sure to assess mentation, the quantity of secretions, and strength of cough.

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Mechanically ventilated patients can develop a condition in which air becomes trapped within the alveoli at end-expiration; this is called auto-PEEP.

Auto-peep has several adverse effects:

• Barotrauma from positive pressure trapped within the alveoli 
• Increased work of breathing
• Worsening pulmonary gas exchange
• Hemodynamic compromise secondary to increased intra-thoraic pressure

Auto-PEEP classically occurs in intubated patients with asthma or emphysema, but it may also occur in the absence of such disease. The risk of auto-PEEP is increased in patients with:

• Short expiration times (i.e., inadequate time for the evacuation of alveolar air at end-expiration)
• Bronchoconstriction
• Plugging of the bronchi (e.g., mucus or foreign body) creating a one-way valve and air-trapping

Auto-PEEP may be treated by:

• Reducing tidal volume
• Reducing the respiratory rate
• Decreasing inspiratory time
• Increasing PEEP

Patients may need to be heavily sedated to accomplish the above ventilator maneuvers.

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