Perioperative Management of Acute Respiratory Distress Syndrome

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Perioperative Management of Acute Respiratory
Distress Syndrome

• R3 ???

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ARDS

• distinct pattern of diffuse lung injury
• clinical and laboratory characteristics
• bedside finding of tachypnea, dyspnea, and
  crackles.
• diminished lung compliance lt (40ml/cm water)
• impaired gas exchange
• diffuse air space infiltrate on chest radiograph
• exclusion of high-pressure pulmonary edema

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Perioperative behavior

• Anticipating three important element
• - differ from ventilator and hemodynamic
  strategies
• - anticipating the behavior of patient with
  ARDS in the OR
• - understanding and overcoming technical
  concerns in ventilating

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Preoperative Issues

• Modern ICU ventilator strategies for ARDS
• Volume Status and Hematocrit Concentration
• Pressure control ventilation
• and endotracheal patency

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Modern ICU ventilator strategies for ARDS

• positive-pressure ventilator with large TV
• - exacerbrate or perpetuate lung injury
• low TV and high PEEP ventilator
• - alveolar overinflation, microscopic lung
  injury, prolonging the ARDS
• Two ICU ventilator strategies
• permissive hypercapnia
• open lung ventilation

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Permissive hypercapnia

• reducing TV
• peak inflation pressure lt 50 cm water
• reducing RR
• PCO2 increase 15-40 mmHg from base line
• hypercapnea, resperatory acidosis
• tolerated

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The open lung ventilation

• limit alveolar closure
• setting end-expiratory volume
• PEEP 12-15 cm water
• limit alveolar overdistension
• limit end-inspiratory volume
• PIP 35-40mm water
• TV 350-400 ml

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Anesthetic concern

• two problem
• - generating and monitoring PEEP level greater
  than 10cm water
• technically difficult during transport or
  anesthesia-type ventilator
• - ventilation to normocapnea impossible
• Additional metabolic acidosis
• perfusion abnormality , large vol of
  crystalloid administration

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Anesthetic concern

• Manipulate pH
• By increasing ventilation
• greater benefit than lung protective ventilator
  strategy

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Another ventilator strategy

• Prone positioning
• dramatically improved oxygenation
• ventilation in atelectatic region, better
  ventilation-perfusion matching
• Arterial desaturation
• during transport and OR positioning

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Two other ICU management strategy

• Volume status
• Hematocrit concentration

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Volume status

• Aggressive volume depletion
• cornerstone of ICU management
• targeting the lowest IV vol adaquate CO
• - mininized interstital and alveolar
  pul.edema
• anesthetic induction
• hemodynamic lability
• preserving end-organ perfusion
• highest priority
• assessed by urine output, generation of
  lactic acidosis

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Hematocrit concentration

• Direct management of oxygen delivery
• Increasing oxygen delivery in the ICU
• increasing Hct
• Anesthesia perspective
• maintain the Hct at preoperative level
• - prevent fluctuation oxygenation

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Pressure control ventilation

• Variable gas flow, constant airway pressure
• Potential advantage in ICU setting
• - promoting recruitment of collapsed aveoli
  throughout the inspiratory cycle
• - possible alveolar ventilation in low PIP
• Protect against barotrauma

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Endotracheal patency

• Use of pressure control ventilaiton Prevent early
  detection ETT occlusion
• Volume control mode
• detection at only 50 or 60
• Pressure control mode
• indistinguishable from worsening intrinsic
  lung compliance
• detection at higher degree of occlusion

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Anesthetic implication

• Conventional ventilator failed patient
• difficulty in ventilation during transport or
  in the OR
• verified tolerate transport ventilation and
  OR ventilator
• Fixes inspiratory pressure
• prevent the early diagnosis of ETT occlusion
• carefully evaluated progressive ETT narrowing

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Intraoperative issue

• Transport
• Anesthesia machine ventilator failure

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Transport

• Specific manual ventilation system
• - Mapelson D circuit
• maintain delivery of high FiO2
• carbon dioxide rebreathing
• - Ambu-bag
• delivered FiO2 varies with the balance
  between MV and fresh gas flowprevent
  rebreathing carbon dioxide

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Anesthesia machine ventilator failure

• OR and ICU ventilator
• differ in performance characteristics
• - less powerful
• - semiclosed system, recirculating exhaled gas
  back into the inspiratory limb
• - resistance and compliance charatersistcs of
  the CO2 absorver
• impede delivery of TV at high RR and high
  gas flow

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Indication for critical care type ventilator

• Preoperative use of PCV
• High airway pressure and high inspiratory flow
• High preoperative PEEP or increased A-a oxygen
  gradient
• Coexisting expiratory obstruction
• Expectation of large fluid shift

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Using nitric oxide in the OR

• Nitric oxide
• selectively vasodilate pulmonary capillaries
• diverting blood flow away from nonventilated
  area
• Interruption NO
• acute hypoxemia or right heart failure
• Administer NO continuously
• during transport and in the OR

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Conclusion(1)

• Preoperative attention
• - ICU mechanical ventilation
• - volume status
• - ETT patency
• - hematocrit concentration

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Conclusion(2)

• Transport
• - manual ventilation system
• matched to the patients need

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Conclusion(3)

• Operation
• - possibility of anesthesia ventilator failure
• manual ventilation or ICU ventilator
• - NO continued