UMEM Educational Pearls - Critical Care

The Maintenance Phase of Therapeutic Hypothermia

Therapeutic hypothermia (TH) has become standard in the care of patients with return of spontaneous circulation from cardiac arrest.  Although the optimal duration of TH is unknown, current literature supports 12-24 hours of cooling to 32-34^oC.  As many of our critically ill patients remain in the ED for seemingly endless lengths of stay, it is likely that most emergency physicians will be managing patients with TH during the maintenance phase of cooling.  Some pearls regarding the maintenance phase:

• Metabolic and hemodynamic homeostasis is critical
• Target volume-cycled mechanical ventilation to maintain a normal pH
• Maintain a MAP > 65 mm Hg
• Maintain blood glucose between 120 - 160 mg/dL
• Frequently check and aggressively replete potassium, magnesium, and phospate

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Acute Hyponatremia and the Critically Ill

• I just left a busy ED shift during which we had a patient with altered mental status and a serum Na of 115 mmol/L.
• Recall that severe hyponatremia may present with lethargy, disorientation, agitation, nausea/vomiting, altered mental status, abnormal respirations, and seizures.
• For severe, symptomatic hyponatremia, the treatment of choice is 3% hypertonic saline
• At a rate of 100 ml/hr, the serum Na should rise approximately 2 mmol/L per hour.
• In general, the duration of treatment with hypertonic saline is based upon sign and sypmtom improvement.
• For those with more longstanding hyponatremia, serum Na should not be increased by more than 12 mmol in the first 24 hours.

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Transient Hypotension and Mortality in Sepsis

• Not surprisingly, septic ED patients with persistent hypotension despite fluid resuscitation have increased mortality.
• What about the more common scenario of septic ED patients who have a transient drop in their BP?
• Recent evidence suggests that ED patients with sepsis who have non-sustained decrease in their BP (SBP < 100 mm Hg) have a 3-fold increased risk of in-hospital mortality compared with those who maintain arterial pressure.
• Take Home Point: Any drop in BP in a septic patient, even if it responds to fluids, portends a higher mortality.  Be vigilant and aggressively resuscitate these patients.

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Heparin for Maintaining Arteral Catheter Patency ?

• Arterial catheter placement is common in many critically ill ED patients.
• Typically, a heparin solution is used in arterial catheters based on the belief that it helps to maintain catheter patency.
• In one of the most recent studies (referenced below), the use of a heparinized solution did not improve the functionality, or increase the duration of patency, of arterial catheters when compared to a saline solution.
• As the incidence of heparin-induced thrombocytopenia (HIT) continues to increase, it is worth noting that the routine use of heparin to maintain arterial catheter patency is not well supported by the literature.

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NICE-SUGAR and Glucose Control in the Critically Ill

• Hypergycemia is associated with increased morbidity and mortality in hetergeneous populations of critically ill patients.
• Over the past few years there has been great interest in aggressively controlling glucose through the use of continuous insulin infusions.
• Results of recent trials and meta-analyses, however, question the benefit of tight glucose control and highlight the marked increase in severe hypoglycemia rates.
• Recently, the results of the NICE-SUGAR study were published, the largest trial to date (6000 patients)evaluating intensive vs. conventional glucose control in the critically ill.
• Investigators found an INCREASED mortality among adults randomized to intensive glucose control
• Given the lack of benefit, potential harm, risks of severe hypoglycemia, and resource utilization, intensive glucose control should not be a therapy routinely implemented in the ED.

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Platelet Transfusions and the Critically Ill

• Current literature suggests that platelets are given too frequently and inappropriately
• Recall that approximately 50% of platelet transfusions fail to increase counts
• In addition, bacterial contamination of units is a special concern, with sepsis occurring 10x more frequently than with PRBCs
• In general, platelet transfusions in nonbleeding patients can be withheld untl the count reaches 10 x 10³/mm³
• A transfusion trigger of 50 x 10³/mm³ should be used for invasive procedures

Ultrasound of the IVC for Volume Assessment

• In a recent pearl, I discussed that a 15% variation in IVC collapsibility could be used as a marker of hypovolemia
• As a follow up and since % variation is sometimes difficult to calculate at the bedside, consider the following numbers:
  • The normal diameter of the IVC is 1.6 - 1.75 cm
  • Patients with hypovolemia typically have an IVC diameter < 0.8 - 1.0 cm
  • In general, the IVC diameter should increase 1 mm for every 100 ml of isotonic fluid

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New Perspectives on Clostridium difficile

• In the past 5 years, C.difficile infection rates have doubled and the overall disease severity appears to be worsening.
• Particularly concerning is the increase in community acquired infections in young patients without antibiotic or nosocomial exposure.
• These epidemiologic changes are likely due to a new strain of C.difficile characterized by increased virulence and quinolone resistance.
• Importantly, the efficacy of metronidazole has waned in recent years.  In fact, > 25% of patients with moderate to severe disease do not respond to metronidazole therapy.
• As a result, vancomycin has become first-line therapy for any critically ill patient with C.difficile.

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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.