UMEM Educational Pearls - By Mike Winters

Acute Cor Pulmonale and Ventilation In the critically ill,

Acute cor pulmonale (ACP) is usually observed in the setting of massive pulmonary embolism or acute respiratory distress syndrome (ARDS). As we manage more and more critically ill patients in the ED, it is likely that you will manage patients who develop ARDS.

We have discussed in previous pearls that, especially in ARDS, using a low tidal volume and monitoring plateau pressure are key components to mechanical ventilation.

For patients with ARDS who develop ACP, consider lower plateau pressure thresholds (< 26 cm H20) and minimizing PEEP to < 8 cm H2O.

If ACP persists despite lower plateau pressures and low PEEP, consider prone position ventilation as a last resort.

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Assessing Volume Status in the Critically Ill

• In previous pearls we have discussed the many limitations of central venous pressure as an accurate marker of volume status.
• Importantly, the focus of volume assessment should be on determining which patients are likely to augment their cardiac output in response to additional IVFs, i.e. 'preload responsive'.
• Ultrasound can be used in the ED to assist in identifying which patients are preload responsive.
• In general, a 15% variation in the inferior vena cava diameter with respiration predicts response to additional fluids.

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Mechanical Ventilation and Obesity

• Obesity is defined as a BMI of 30 - 34.99 kg/m2, with class II obesity defined as 35 - 39.9 kg/m² and extreme obesity as > 40 kg/m²
• In obese patients:
  • oxygen consumption is increased with a high proportion going to the work of breathing
  • lung volumes are abnormal with reduced expiratory reserve
  • the alveolar - arterial oxygen difference is increased
  • respiratory system compliance is markedly reduced
• These changes are futher exacerbated in the supine position
• To overcome the effects of reduced compliance, higher levels of PEEP are generally needed
• In addition, higher plateau pressures may be necessary to achieve adequate tidal volumes

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Ventilation in the Brain-injured Patient

• As we have discussed in previous pearls, the ARDSnet trial forms the basis for ventilatory management in the ICU.  A primary component to current ventilatory management is the focus on maintaining lower and safer distending pressures through the use of lower tidal volumes.
• Similar to last week's pearl on the obstetric patient, these ventilatory settings may not be applicable to all patients.
• Recall that the use lower tidal volumes results in lower minute ventilation.  This leads to the accumulation of CO₂, termed permissive hypercapnia.  In general, we tolerate higher levels of CO₂ in favor of lower plateau pressures.
• For the brain-injured patient, however, increases in CO₂ may increase intracranial pressure (ICP) causing adverse effects.
• Current recommendations for mechanical ventilation in the brain-injured patient include maintaining a P_aCO₂ between 35 - 40 mm Hg.  Thus, you need to be more vigilant at following P_aCO₂ in this patient population.

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Mechanical Ventilation of the Obstetric Patient

• In previous pearls, we have discussed ventilatory settings to avoid excessive volumes and limit plateau pressures to < 30 cm H₂O
• Importantly, these settings have not be extensively evaluated in pregnant patients
• Some important pearls when ventilating the pregnant patient:
  • Avoid hyperventilation, as this adversely affects uterine blood flow
  • Optimize oxygenation to ensure adequate fetal oxygen delivery (us 100% F_iO₂)
  • In the presence of adequate oxygenation, P_aCO_s values <= 60 mm Hg do not appear to be detrimental to the fetus

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Critical Illness-Related Corticosteroid Insufficiency (CIRCI)

• CIRCI is defined as inadequate corticosteroid activity for the severity of illness of a patient
• CIRCI arises due to steroid tissue resistance and inadequate circulating levels of free cortisol
• Hypotension refractory to fluids and requirement of vasopressors is the primary manifestation of CIRCI
• In contrast to chronic adrenal insufficiency, hyponatremia and hyperkalemia are uncommon
• Consider CIRCI in all critically ill patients requiring vasopressor support

So, which critically ill patients do you treat with steroids?  Current literature suggests the indications for steroid treatment include vasopressor dependent septic shock and persistent ARDS despite supportive therapy and lung protective ventilation.  A patient who requires only an hour or two of a vasopressor while being fluid resuscitated is unlikely to benefit.  An accepted dosing schedule is hydrocortisone 50 mg IV every 6 hours.

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Early Critical Care Management of Aneurysmal SAH

• 30,000 patients per year have an SAH
• Early ED management certainly should focus on airway assessment, emergent CT scanning, continuous caridac monitoring, and serial neurologic exams
• A few other pearls regarding management:
  • Volume management - maintain euvolemia with an isotonic crystalloid fluid
  • Anticonvulsants - routine use is associated with cognitive impairment and is not recommended
  • Steroids - once used to reduce meningeal irritation, however, there is no convincing evidence of a beneficial effect.  As such, corticosteroids are no longer recommended.
  • Rebleeding - risk of rebleeding is highest in first 24 hours after initial SAH.  Definitive prevention is done by repair via surgery or endovascular coiling.  A large, prospective study found outcome was better with endovascular coiling.

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Neuromuscular Blocking Agent (NMBA)

• NMBAs are used to facilitate intubation when performing RSI
• Importantly, NMBAs have no analgesic or amnestic effects
• Indiscriminate and repeated dosing of NMBA can lead to prolonged recovery and critical illness polyneuromyopathy, a devastating complication of critical illness that prolongs ventilation, ICU/hospital length of stay, and increases mortality
• Take Home Point: provide adequate amounts of sedation and analgesia to your intubated ED patients rather then reflexively giving repeated doses of NMBA

The Crashing Intubated ED Patient

• For intubated ED patients who develop respiratory distress and are hemodynamically unstable, perform the following:
  • Immediately disconnect from the ventilator
  • Manually ventilate with 100% F_iO₂
  • Exclude tension pneumothorax (decompress)
  • Exclude auto-PEEP (allow for lung deflation)
  • Check ET tube for kinks, twisting, or obstruction
  • Check for air leak (check pilot balloon and listen for air coming from mouth/nose during manual ventilation)
  • Check the ventilator circuit

Sepsis in Pregnancy

• Sepsis in the setting of pregnancy is primarily the result of pelvic infections such as chorioamnionitis, endometritis, septic abortion, or urinary tract infection
• In these patients, aerobic gram-negative rods (E. coli, Enterococci, Beta-hemolytic strep) are the principal etiologic agents
• An empiric broad spectrum antibiotic regimen is ampicillin, gentamicin, and clindamycin (or metronidazole)

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Ventilator Associated Pneumonia (VAP)

• VAP is the leading cause of death among hospital acquired infections
• VAP causes prolongation of mechanical ventilation, ICU/hospital length of stay, and adds about $40,000 to the patient's admission
• As we care for more and more intubated patients for longer and longer periods of time, it is crucial to know some simple preventative measures we can do in the ED to reduce morbidity and mortality
• In the absence of contraindications, elevate the head of the bed to 30-45 degrees for intubated patients
• This is a simple, no cost intervention that has been shown to decrease the incidence of VAP

Sedation and Analgesia in Mechanical Ventilation

• Mechanically ventilated patients routinely experience pain and anxiety from the presence of an endotracheal tube, ventilator strategies, placement of invasive catheters, surgical procedures, and even nursing procedures such as suctioning and repositioning.
• Recent literature highlights that many of our vented patients received inadequate amounts of analgesia and anxiolysis
• When giving anxiolytics and analgesics, focus first on analgesics. 
• Patients given analgesics first, followed by anxiolytics, consistently achieve goals with less amounts of supplemental medications needed.

Pneumonia and Sepsis

• As we have discussed, one of the most important components in the ED management of sepsis is the administration of early and appropriate broad-spectrum antibiotics
• Pneumonia remains one of the most common causes of sepsis in the US and worldwide
• Given the steady rise in incidence of MRSA, remember to add vancomycin to your empiric treatment of patients with pneumonia and severe sepsis or septic shock

Clinical Manifestations of Anaphylaxis

• Importantly, manifestations of anaphylaxis occur along a continuum and are dependent upon the type, route, and quantity of antigen exposure.
• Cutaneous (90%), respiratory (40-70%), cardiovascular (30-35%), gastrointestinal (40%), neurologic (10%), ocular, and genitourinary symptoms can all be seen.
• Include anaphylaxis in the differential of any patient with undifferentiated shock, as 10% will not manifest the cutaneous symptoms of urticaria and/or angioedema.

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Sepsis and Mechanical Ventilation

• Essential components of the ED management of sepsis include early identification, antibiotics ASAP, fluid resuscitation, and maintaining adequate perfusion pressure.
• If patients continue to have evidence of shock (i.e. high lactate) despite adequate fluids and/or pressors, strongly consider intubation, even in the patient without acute respiratory decompensation.
• The respiratory muscles are avid consumers of oxygen and can use up to 50% of circulating O₂.
• Intubation and paralysis not only increase available O₂ to vital organs, it can also augment cardiac output for patients with persistent septic shock.

Intracerebral hemorrhage and fluid management

• Isotonic fluids (0.9% saline) are the standard IV fluid for patients with ICH
• The goal for fluid management is to maintain euvolemia with a urine output > 0.5 cc/kg
• Importantly, 0.45% saline and dextrose containing IVFs should be avoided, as they can exacerbate cerebral edema and increase ICP
• Hypertonic saline has become a popular aternative to normal saline in patients with significant perihematomal edema and mass effect
• Goals when using hypertonic saline are to maintain serum osmolality between 300 - 320 mOsm/L and serum sodium between 150 - 155 mEq/L

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Blood Pressure Control in ICH

• Aggressive BP reduction after ICH is currently the focus of an ongoing NINDS study (ATACH Study)
• Current literature recommends that extreme levels of BP after ICH be treated to reduce hematoma expansion
• Mean arterial pressures (MAP) > 130 mmHg should be treated with continous IV medications
• Current recommended medications include labetalol, esmolol, nicardipine, and fenoldopam
• Nitroprusside is avoided by many given its tendency to increase ICP
• Oral and sub-lingual medications are not indicated for immediate and precise BP control

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Hemofiltration

• Renal replacement therapy (RRT) involves the use of semipermeable membranes to remove fluid and toxic substances from the bloodstream
• The basic methods of RRT are hemodialysis (HD) and hemofiltration (HF)
• There have been a few cases in our ED in which our Renal consultants have used HF
• Hemofiltration can remove large volumes of fluid (up to 3 Liters per hour)
• Major advantages to HF: less likely to produce hypotension than HD, can remove larger molecules than HD
• Disadvantages to HF: must be done continuously to provide effective dialysis, requires anticoagulation to maintain circuit patency, not well suited for hypotensive patients (requires a hydrostatic pressure gradient for solute clearance)

Catheter Positioning

• Central venous catheters (CVC) inserted from the left side must make an acute angle downward when the enter the SVC from the innominate vein
• CVCs that do no make this turn can end up with the tip pointing directly at the lateral wall of the SVC
• CVCs in this position can cause perforation of the SVC
• If the catheter tip is pointing at the SVC, then advance the catheter further down

Central Venous Catheter Occlusion

• Many of us care for patients that present with pre-existing CVCs
• Catheter occlusion is the most common complication associated with CVC
• Thrombosis is the most common cause of obstruction of CVCs
• Thrombosis is often be due to insoluble precipitates; meds such as diazepam, digoxin, phenytoin, and TMP-SMX can cause these precipitates
• Local instillation of a thrombolytic agent (tPA) can be effective in restoring CVC patency
• One protocol for use of tPA in CVC occlusion is to:
  • reconstitute a 50 mg vial with 50 mL sterile water (1 mg/mL)
  • draw up 2 mL in a 5 cc syringe and inject into the CVC - total tPA dose 2 mg
  • leave in place for approximately 2 hours
  • attempt to flush the CVC with a saline solution
• If the catheter remains obstructed, a new CVC should be placed at a new site
• The total drug dose in this regimen (4 mg) is too small to cause systemic thrombolysis