Ventilation Strategies in ARDS MICU-ER Joint Conference

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Ventilation Strategies in ARDS MICU-ER Joint
Conference

• Dr. Rachmale, Dr. Prasankumar 12/3/08

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Initial ICU Management

• EGDT implemented, CVP- Subclavian line placed,
  Initial CVP8, Lactic Acid- 5.5
• CVP aim gt 12, Map gt 65? IV fluids 3L, Urine
  output gt0.5ml/kg/hr
• Antibiotics- zosyn/ ciprofloxacin within one hour
• Initial ABG
• pH 7.19 Po2 60 Pco2 48, sat 84
• At this time Ventilator setting
• AC/TV-400/RR-28/FiO2 100/PAP-36/PLP-30/
  peep- 7
• Pao2/Fi0260

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ARDS- Definition

• 1. PaO2/FiO2 200
• 2. Bilateral (patchy, diffuse, or homogeneous)
  infiltrates consistent with pulmonary edema
• 3. No clinical evidence of left atrial
  hypertension ( PCWPlt18)

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NIH-NHLBI ARDS Network Cause of Lung Injury
NHLBI ARDS Clinical Trials Network. N Engl J Med.
2004.
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Mortality from ARDS

• ARDS mortality rates - 31 to 74
• The main causes of death are non-respiratory
  causes (i.e., die with, rather than of, ARDS).
• Early deaths (within 72 hours) are caused by the
  underlying illness or injury, whereas late deaths
  are caused by sepsis or multi-organ dysfunction

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Stages of ARDS
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RATIONALE FOR LOW STRETCH VENTILATION

• Lung injury from
• Over-distension/shear - gt physical injury
• Mechanotransduction - gt biotrauma
• Repetitive opening/ closing
• Shear at open/ collapsed lung interface

volutrauma
atelectrauma
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ARDSNET- Initial Ventilator Strategies

• Low Tidal Volume (6ml/kg)
• Calculate predicted body weight (PBW)
• Males 50 2.3 height (inches)
• Females 45.5 2.3 height (inches) -60
• Plateau Pressure lt 30 cms

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Minimizing VILI- Plateau pressure goals

• If Pplat gt 30 cm H2O decrease VT by 1ml/kg steps
  (minimum 4 ml/kg)
• If Pplat lt 25 cm H2O and VTlt 6 ml/kg, increase VT
  by 1 ml/kg until Pplat gt 25 cm H2O or VT 6 ml/kg

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Mortality low vs. traditional tidal volume
RRR22 ARR8.8 NNT12
p0.007
Traditional tidal volume
Low tidal volume
ARDSNet. NEJM 20003421301.
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PEEP in ARDS

• Protective effect by avoiding alveolar collapse
  and reopening
• Prevent surfactant loss in the airways ?avoid
  surface film collapse
• Use of PEEP avoids end-expiratory collapse, thus
  Recruitment is obtained at end-inspiration

Lower PEEP/Higher FiO2
FiO2 .3 0.4 0.4 0.5 0.5 0.6 0.7 0.7 0.7 0.8 0.9 0.9 0.9 1.0
PEEP 5 5 8 8 10 10 10 12 14 14 14 16 18 18-24
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Recruitment Maneuvers

• Improve hypoxia
• Recruitment of nonaerated lung units (collapsed
  alveoli)- caudal and dependent lung regions in
  patients lying supine
• Maneuvers short-lasting increases in
  intrathoracic pressures
• Intermittent increase of PEEP
• On AC mode or through ambu bag with PEEP valve
• Continuous positive airway pressure (CPAP)
• Cahnge back up rate and apnea alarm
• Increasing the ventilatory pressures 50 cm H2O
  for 1-2 minutes
• Intermittent sighs or Extended sighs
• Can cause Hypotension, pneumothorax, Needs
  Experience

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Management of Our patient

• Initial ABG
• pH 7.19 Po2 60 Pco2 48, sat 84
• At this time Ventilator setting
• AC/ TV-400/ RR-28 /FiO2 100/PAP-36/PLP-30/
• peep 10 sat 84
• Initial changes made
• AC/ TV-400/ RR-35 /FiO2 100/PAP-36/PLP-30/ peep-
  17 sat 94
• Recruitment Needed

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Management continued

• After transfer to MICU, episodes of hypoxia
  despite maximal mechanical ventilation
• Improved with recruitment maneuvers
• Next 48 hours Vt decreased to 370 then 320,
  PEEP increased to 20 then 22, plateau pressures
  34-37 on 100 FiO2
• Even such Low Vt, unable to maintain plateau
  pressures below 30
• Permissive Hypercapnia

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Management continued

• Severe sepsis? septic shock, apache 38
• Aggressive hydration, Vasopressor (Levophed) to
  maintain MAPgt65, fixed dose vasopressin,
  hydrocortisone and xigris ( Activated Protein C)
  given
• Lactate remained high, SvO2 70-77
• BC Strep pneumonia-

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Hospital Course

• During entire 25 day course Fio2 requirements
  could not be lowered to less than 80, the least
  PEEP was 14
• Peak and plateau pressure remained high
• Septic shock? MSOF? death

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Alternative strategies

• Prone Positioning- recruitment of posterior lung
  fields
• High frequency oscillatory ventilation (HFOV)-
  low tial volumes at high frequences
• Nitric oxide- selective vasodilator of vessels
  that perfuse well ventilated lung zones
• Extracorporeal membrane oxygenation
  (ECMO)-Veno-arterial bypass which supports gas
  exchange and oxygenation

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Summary of Recommendations

• Limited VT 6 mL/kg PBW to avoid alveolar
  distension
• End-inspiratory plateau pressure lt 30 cm H2O
• Adequate end expiratory lung volumes utilizing
  PEEP and higher mean airway pressures to minimize
  atelectrauma and improve oxygenation
• Consider recruitment maneuvers