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Flashcards in 33 Acute Respiratory Distress Syndrome Deck (29):
1

ARDS

  • The pathophysiology involves...
  • Complications of patient management
  • The injury of the lung parenchyma is associated with...
  • The pathophysiologic process leads to...
  • The pathophysiologic process appears to have...

  • The pathophysiology involves...
    • An inflammatory process within the lung parenchyma leading to alveolar capillary injury
  • Complications of patient management
    • Include ventilator management and infection
    • Can extend the alveolar capillary injury
  • The injury of the lung parenchyma is associated with...
    • Permeability lung edema
    • Loss of normal surfactant in the airspace of the lung
    • Capillary thrombi formation
  • The pathophysiologic process leads to...
    • Marked hypoxemia secondary to shunt physiology
    • Loss of lung compliance with restrictive physiology
    • The development of pulmonary hypertension
  • The pathophysiologic process appears to have...
    • A common clinical and pathologic progression regardless of the inciting predisposing condition

2

ARDS time course

  • ARDS has a recognized time course characterized by...
  • The patient transitions across these pathophysiologic states over...

  • ARDS has a recognized time course characterized by two distinct clinical phases
    • The exudative phase
    • The proliferative phase
  • The patient transitions across these pathophysiologic states over a typical 2-week hospitalization, although the actual timing is highly variable from patient to patient

3

ARDS time course:
Exudative phase

  • General
  • Characterized by...
  • This stage typically lasts...
  • This period clinically is characterized by...
  • Pathologically this stage corresponds to the term...

  • The early phase of ARDS
  • Characterized by...
    • Epithelial injury consisting of cellular swelling
    • Denudation of type I epithelial cells
    • Hyaline membrane formation
    • Fibrin deposition
    • Interstitial neutrophilic infiltrates
  • This stage typically lasts over a 3-7 day period, but the duration is actually highly variable
  • This period clinically is characterized by...
    • Diffuse bilateral alveolar pulmonary infiltrates
    • Marked oxygenation difficulty due to the associated intrapulmonary shunt
  • Pathologically this stage corresponds to the term diffuse alveolar damage (DAD) which is characteristic of ARDS

4

ARDS time course:
Proliferative phase

  • General
  • Characterized by...
  • Characteristic changes include...
  • Time interval
  • This period clinically is characterized by...

  • The second or "proliferative" phase
  • Characterized by organization of the alveolar and interstitial infiltrates
  • Characteristic changes include...
    • Fibroblast proliferation
    • Type II cell hyperplasia with lymphocyte infiltration
  • At a variable time interval following the exudative stage, the patient enters this fibrotic phase characterized by extensive collagen deposition
  • This period clinically is characterized by...
    • Diffuse interstitial pulmonary infiltrates
    • Ventilator dependence secondary to high ventilatory impedance
    • Elevated deadspace ventilation

5

Pathophysiology of ARDS

  • Shunt physiology
  • Pulmonary edema is recognized to occur in two forms
    • Hydrostatic pulmonary edema
    • ARDS 

  • Shunt physiology
    • The hypoxemia of ARDS occurs from shunt physiology resulting from the alveolar edema due to abnormal fluid movement at the alveolar-capillary membrane
  • Pulmonary edema is recognized to occur in two forms
    • Hydrostatic pulmonary edema
      • Results from an imbalance of the forces normally responsible for fluid flux at the alveolar capillary membrane, specifically an elevation in left ventricular end-diastolic pressure and secondary elevation of pulmonary microvascular hydrostatic pressure
    • ARDS
      • A form of non-cardiogenic pulmonary edema or permeability edema that occurs in the absence of elevated pulmonary microvascular hydrostatic pressures

6

Pathophysiology of ARDS:
The inflammation and repair process in the injured alveolus

  • Both neutrophils and macrophages 
    • Participate in an active inflammatory process in the alveolar space
    • Lead to loss of alveolar Type 1 cell function and disruption of surfactant
  • Redundant inflammatory signaling pathways
    • Recognized from both epithelial and endothelial injury
    • Have complicated the development of effective drug therapy specific for patients with ARDS

7

Signs and symptoms

  • The clinical signs and symptoms in the patient with acute respiratory failure and ARDS include...
  • Physical findings are nonspecific
  • The clinical presentation
  • The parenchymal lung disease results in...
  • Early findings of progressive mechanical respiratory failure include...
  • More progressive signs of abnormal respiratory muscle activation that follow these early signs

  • The clinical signs and symptoms in the patient with acute respiratory failure and ARDS include...
    • Dyspnea with acute hypoxemia
    • Possibly hypercapnia
  • Physical findings are nonspecific
    • Tachycardia
    • Tachypnea
    • Elevation of the blood pressure
  • The clinical presentation
    • Will vary depending on the underlying condition producing the syndrome
  • The parenchymal lung disease results in...
    • An augmentation of the mechanical workload of the respiratory muscles
  • Early findings of progressive mechanical respiratory failure include...
    • Tachycardia
    • Tachypnea
    • A reduction in the resting tidal volume
  • More progressive signs of abnormal respiratory muscle activation that follow these early signs
    • Accessory muscle use
    • Asynchronous respiratory muscle activity
    • Frank abdominal paradox

8

Distinguishing between hydrostatic (CHF) and permeability (ARDS) edema

  • Careful history and detailed physical examination with attention to...
  • Non-invasive techniques such as echocardiography can demonstrate evidence for...
  • Radiographic findings reported to favor a cardiac etiology for respiratory failure include...
  • Despite the careful use of history, physical exam, and radiographic studies, clinicians often struggle to distinguish...
  • In a small fraction of patients,...

  • Careful history and detailed physical examination with attention to...
    • The presence of abnormal cardiac auscultatory findings including extra heart sounds and murmurs
    • Review of body weight and fluid balance changes as well as electrocardiographic findings can support a cardiac etiology
  • Non-invasive techniques such as echocardiography can demonstrate evidence for...
    • Cardiac dysfunction including wall motion abnormalities or ventricular dilatation
  • Radiographic findings reported to favor a cardiac etiology for respiratory failure include...
    • Cephalization of venous blood flow in an erect patient
    • A homogeneous, principally basal and perihilar edema distribution
    • A normal or enlarged vascular pedicle
  • Despite the careful use of history, physical exam, and radiographic studies, clinicians often struggle to distinguish...
    • Ccardiogenic from non-cardiogenic pulmonary edema in certain critically ill patients
  • In a small fraction of patients,...
    • A right heart catheterization is required as a diagnostic tool to distinguish these two forms of pulmonary edema

9

AECC definition:
Four recognized clinical features

  • An acute onset of respiratory symptoms
  • Bilateral airspace pulmonary infiltrates (reflecting alveolar edema) on a frontal chest radiograph
  • The absence of clinical evidence for elevated pulmonary microvascular hydrostatic pressures (non-cardiogenic edema) by clinical criteria or a measured pulmonary artery occlusion pressure (PAOP ) < 18 mm Hg
  • The presence of significant hypoxemia as measured by a reduction in the arterial blood gas relative to the inspired oxygen concentration or the PaO2/FiO2 (P/F) ratio

10

AECC definition

  • Variable severity of the syndrome leads to classification of ARDS patients into two overlapping groups
  • ARDS 
  • The AECC definition of ARDS 
  • Patients that meet all the AECC criteria for ARDS, yet lack a specific predisposing condition, demonstrate...

  • Variable severity of the syndrome leads to classification of ARDS patients into two overlapping groups
    • Acute lung injury (ALI)
      • A milder form of the syndrome with a P/F ratio < 300
    • ARDS
      • The more severe form of the disorder with a P/F ratio < 200.
  • ARDS
    • The prototype lung disease characterized by non-cardiogenic, alveolar (air-space) edema
  • The AECC definition of ARDS
    • Is not specific and can describe a broad range of clinical conditions
    • Each component of the definition is recognized to lack precision, which creates a heterogeneous patient population particularly from the perspective of clinical research studies
  • Patients that meet all the AECC criteria for ARDS, yet lack a specific predisposing condition, demonstrate...
    • The pathologic equivalent of ARDS called diffuse alveolar damage at lung biopsy in only ~ 50% of the cases
    • These data illustrate the non-specific nature of the clinical parameters used to identify the ARDS syndrome

11

Limitations to the AECC definition

  • The AECC definition does not specify...
  • Investigators have demonstrated that variable PEEP and FiO2 settings, in the same patient, can produce...
  • The distinction between ALI and ARDS
  • The AECC radiographic criteria for ARDS 

  • The AECC definition does not specify...
    • The inspired oxygen concentration (FiO2)
    • The positive end-expiratory pressure (PEEP) level required to obtain the PaO2/FiO2 ratio
  • Investigators have demonstrated that variable PEEP and FiO2 settings, in the same patient, can produce...
    • Different PaO2/FiO2 ratios
    • This could change a patient’s disease classification from normal to ALI to ARDS
  • The distinction between ALI and ARDS
    • Becomes dependent on the ventilator settings rather than the patient characteristics
    • The distinction by gas exchange criteria does not appear to define an increased severity of disease or mortality risk
  • The AECC radiographic criteria for ARDS
    • Describe bilateral pulmonary infiltrates
    • Although very simple in description, radiologists do not always agree if a patient has bilateral pulmonary infiltrates
    • Further, bilateral pulmonary infiltrates can be homogeneously distributed (= in distribution) or heterogeneously distributed
    • This distribution may actually reflect different phenotypes of the ARDS syndrome

12

Limitations to the AECC definition

  • The AECC definition also characterizes ARDS...
  • PAOP in the patients that were thought to have ARDS and received a pulmonary artery catheter
  • To address the existing limitations in the AECC ARDS definition, ARDS investigators have modified the definition to a revised of parameters called...

  • The AECC definition also characterizes ARDS...
    • By the absence of hydrostatic edema
    • Based either upon clinical criteria or alternatively by measurement of the pulmonary capillary occlusion pressure (PAOP) as < 18 mm Hg
  • PAOP in the patients that were thought to have ARDS and received a pulmonary artery catheter
    • 18% of patients had a PAOP > 18 mm Hg
  • To address the existing limitations in the AECC ARDS definition, ARDS investigators have modified the definition to a revised of parameters called...
    • The Berlin criteria for ARDS

13

Berlin definition

  • Timing 
  • Chest imaging 
  • Origin of edema 
  • Oxygenation
    • Mild
    • Moderate
    • Severe
  • Although the Berlin criteria reflect an improvement in the description of the specific parameters of ARDS, they still represent...

  • Timing
    • Onset within one week of a known clinical insult or worsening respiratory symptoms
  • Chest imaging
    • Bilateral opacities not fully explained by effusions, lobar/lung collapse, or nodules
  • Origin of edema
    • Respiratory failure not fully explained by cardiac failure or fluid overload. Need an objective assessment (eg. echocardiography) to exclude hydrostatic edema if a risk factor is not present
  • Oxygenation
    • Mild
      • 200 < P/F ratio < 300 with PEEP or CPAP > 5 cm H20
    • Moderate
      • 100 < P/F ratio < 200 with PEEP > 5 cm H20
    • Severe
      • P/F ratio < 100 with PEEP > 5 cm H20
  • Although the Berlin criteria reflect an improvement in the description of the specific parameters of ARDS, they still represent...
    • Non-specific findings
    • Their specificity for identifying the pathologic finding of diffuse alveolar damage remains to be determined

14

Risk factors and predisposing conditions

  • Predisposing conditions 
    • Include...
    • Develpoment of ARDS
  • Modifying factors
    • Include...
    • Development of ARDS

  • Predisposing conditions
    • Include...
      • Sepsis
      • Pneumonia
      • Aspiration pneumonia
      • Trauma
      • Emergency surgery
    • Only ~4% of patients with a given predisposing condition develop the ARDS syndrome
  • Modifying factors
    • Other factors, both genetic and clinical
      • Hypoalbuminemia
      • Treatment with chemotherapy
      • Alcohol use (one of the strongest modifying risk factors)
    • Must be present to increase the patient’s risk of developing ARDS

15

ARDS outcome

  • Physiologic and biochemical variables examined in the ARDS patient population to predict patient outcome
  • Better severity adjusted outcome
  • Worse severity adjusted outcome
  • ARDS is a disorder of...
  • The transpulmonary gradient (TPG) 
  • The development of an elevated TPG in patients with ARDS is associated with...

  • Physiologic and biochemical variables examined in the ARDS patient population to predict patient outcome
    • Traditionally recognized as a disease of severe hypoxemia
      • However, the severity of the hypoxemia is not predictive of outcome in the early phases of ARDS
    • In contrast, a marker of ventilation efficiency, the physiologic deadspace, is an accurate predictive marker
  • Better severity adjusted outcome
    • Trauma as the inciting agent as compared to patients with sepsis as the predisposing condition
  • Worse severity adjusted outcome
    • African-American and Hispanic patients
  • ARDS is a disorder of...
    • The alveolus with edema and hyaline membrane formation
    • A pulmonary vascular disease
  • The transpulmonary gradient (TPG)
    • A measure of the pulmonary vascular resistance
  • The development of an elevated TPG in patients with ARDS is associated with...
    • A significant increase in mortality
    • Illustrates the importance of ARDS as both an epithelial (alveolus) and endothelial (pulmonary vascular) disorder

16

ARDS outcome

  • Inflammatory biomarkers 
  • These biomarkers come from a broad range of classes including...
  • The level of these biomarkers has been linked to...
  • Risk models that incorporate both the clinical characteristics of ARDS and these biochemical mediators are being explored to better characterize...

  • Inflammatory biomarkers
    • Have been described in the blood of ARDS patients
    • Appear be associated with mortality risk and/or time on mechanical ventilation
  • These biomarkers come from a broad range of classes including...
    • Pro-inflammatory biomarkers (IL-6, IL-8, TNF-a)
    • Markers of endothelial injury (plasma surfactant protein D)
    • Markers of coagulation and fibrinolysis (plasma protein C)
  • The level of these biomarkers has been linked to...
    • Prognosis for the disorder either in terms of mortality risk or time on mechanical ventilation
  • Risk models that incorporate both the clinical characteristics of ARDS and these biochemical mediators are being explored to better characterize...
    • Patients at risk for ALI/ARDS
    • The mortality risk once patients develop the disorder

17

Clinical management of ARDS:
Mechanical ventilation and tidal volume

  • The majority of patients with ARDS will require...
  • Patients with ARDS present a special challenge for ventilator management
    • Elevated deadspace ventilation
    • Hypoxemia 
  • The necessary ventilator support to manage ARDS must be accomplished without...

  • The majority of patients with ARDS will require...
    • Support with mechanical ventilation due to significant hypoxemia with an increased work of breathing
  • Patients with ARDS present a special challenge for ventilator management
    • Elevated deadspace ventilation
      • Augments ventilation requirements
      • Combines with high respiratory inflation impedance to place significant demands on the mechanical support
    • Hypoxemia
      • Due to shunt physiology 
      • Does not respond simply to an increase in the inspired oxygen concentration (characteristic of a shunt)
      • Correction of hypoxemia in ARDS often requires the application of positive end-expiratory pressure to recruit or “keep open” collapsed alveoli to reduce the shunt physiology
  • The necessary ventilator support to manage ARDS must be accomplished without...
    • Aggravating a lung that is already injured

18

Clinical management of ARDS:
Mechanical ventilation and tidal volume

  • Early in the use of ventilator support for the acute respiratory distress syndrome,...
  • Early animal models demonstrated that inflation of normal lung tissue at increasing peak inspiratory pressures...
  • These animal studies first raised the possibility that forcing the lung to inflate to high tidal volumes...
  • Investigators next studied the range of tidal volumes or breath size used by clinicians for the management of ARDS patients

  • Early in the use of ventilator support for the acute respiratory distress syndrome,...
    • Lungs inflated with high inspiratory pressures have a propensity to develop extra-alveolar air leaks (termed barotrauma)
  • Early animal models demonstrated that inflation of normal lung tissue at increasing peak inspiratory pressures...
    • Was associated with the development of lung water
    • If the increase in airway pressure was repeated with the animal’s chest casted, so no volume increase occurred, the injury pattern was not seen
  • These animal studies first raised the possibility that forcing the lung to inflate to high tidal volumes...
    • Might be bad for the patient
    • This injury to the lung secondary to overinflation was given the term volutrauma.
  • Investigators next studied the range of tidal volumes or breath size used by clinicians for the management of ARDS patients
    • ARDS patients showed no consistency using a broad range of tidal breaths

19

Clinical management of ARDS:
Mechanical ventilation and tidal volume

  • The group with a reduced tidal volume also demonstrated...
  • The type of ventilator management influences...
  • The results of this study have led clinicians to use...

  • The group with a reduced tidal volume also demonstrated...
    • A reduced level of blood inflammatory mediators compared to the higher tidal volume group
  • The type of ventilator management influences...
    • The magnitude of the host inflammatory response
  • The results of this study have led clinicians to use...
    • Smaller breath sizes (tidal volume ~ 6ml/kg ideal body weight) to manage patients with ARDS as well as other clinical conditions

20

Clinical management of ARDS:
Mechanical ventilation and tidal volume:
This important clinical research in ARDS has introduced three new terms to describe the types of injury the patient can suffer when they are managed on a mechanical ventilator

  • Barotrauma
  • Volutrauma 
  • Biotrauma 

  • Barotrauma
    • Extra-alveolar air leaks (ie pneumothorax, pneumomediastinum) that occur in association with high airway inflation pressures
  • Volutrauma
    • Lung injury produced by overinflation of alveolar units generally in association with the use of high tidal volume ventilation
  • Biotrauma
    • The release of inflammatory mediators from the lung in response to over distention
    • These inflammatory mediators, released systemically, have the potential to cause generalized inflammation and organ failures remote from the lung

21

Clinical management of ARDS:
Mechanicalventilation and positive end-expiratory pressure (PEEP)

  • The primary clinical manifestation of ARDS 
  • To address the severe hypoxemia the clinician can...
  • The lack of alveolar ventilation in perfused regions produces...
  • The clinician can then use...
  • The term PEEP or positive end-expiratory pressure 
  • CPAP (continuous positive airway pressure) 
  • Maintaining positive airway pressure at the end of a breath serves to...

  • The primary clinical manifestation of ARDS
    • Severe hypoxemia
  • To address the severe hypoxemia the clinician can...
    • Increase the inspired oxygen concentration (FiO2) on the ventilator
    • This will be helpful, but will not be effective in collapsed or flooded alveoli
  • The lack of alveolar ventilation in perfused regions produces...
    • A shunt that is not compensated for by the increased alveolar oxygen concentration in well-ventilated regions
  • The clinician can then use...
    • Positive airway pressure to open or "recruit" the collapsed lung
    • This will restore ventilation in these poorly ventilated regions and therefore reduce shunt and improve oxygenation
  • The term PEEP or positive end-expiratory pressure
    • Airway pressure maintained > atmospheric pressure during machine-assisted breaths
  • CPAP (continuous positive airway pressure)
    • Positive end-expiratory pressure during spontaneous breathing
  • Maintaining positive airway pressure at the end of a breath serves to...
    • Maintain alveolar volume, reduce the shunt component, and improve gas exchange

22

Clinical management of ARDS:
Mechanicalventilation and positive end-expiratory pressure (PEEP)

  • Once you have selected a low tidal volume to manage your patient with ARDS, you will be faced with the selection of...
  • Many different approaches have been used to pick the best combination of...
  • High inspired oxygen concentration is believed to cause...
  • PEEP is associated with...
  • Currently, clinicians titrate...

  • Once you have selected a low tidal volume to manage your patient with ARDS, you will be faced with the selection of...
    • A combination of inspired oxygen concentration (FiO2) and positive end-expiratory pressure (PEEP) to manage your patient’s hypoxemia
  • Many different approaches have been used to pick the best combination of...
    • PEEP and FiO2 to achieve the target goals for oxygenation
  • High inspired oxygen concentration is believed to cause...
    • Lung injury from oxygen toxicity
    • This knowledge favors the use of lower oxygen concentrations and higher levels of PEEP
  • PEEP is associated with...
    • A reduction in cardiac output and higher airway pressures
    • This knowledge favors the use of lower PEEP and higher FiO2
  • Currently, clinicians titrate...
    • The FiO2/PEEP strategy to achieve optimal oxygenation using their best clinical judgement

23

Clinical management of ARDS:
Mechanicalventilation and positive end-expiratory pressure (PEEP)

  • The main challenge to ventilator management in ARDS 
  • Normal areas of lung provide...
  • Excessive alveolar distention with large tidal volume in these regions can...
  • Other areas of the injured ARDS lung
  • Opening and closing of these regions with each ventilatory cycle has...
  • The best titration of PEEP for these regions 
  • Some areas of ALI/ARDS injury are densely consolidated and...
  • No single ventilation strategy can be used without any risk in the patient with...

  • The main challenge to ventilator management in ARDS
    • The heterogeneous nature of the lung injury
  • Normal areas of lung provide...
    • Effective oxygenation and ventilation
  • Excessive alveolar distention with large tidal volume in these regions can...
    • Extend lung injury (volutrauma)
  • Other areas of the injured ARDS lung
    • Have collapse from alveolar inflammation
    • Have loss of surfactant
    • Are recruitable with the correct application of PEEP
  • Opening and closing of these regions with each ventilatory cycle has...
    • An adverse effect on the lung (atelectrauma) but prevention of this process is complicated
  • The best titration of PEEP for these regions
    • Is complex
    • Can lead to overinflation of normal regions if excessive
  • Some areas of ALI/ARDS injury are densely consolidated and...
    • Will not respond to tidal inflation or to changes in PEEP
  • No single ventilation strategy can be used without any risk in the patient with...
    • Heterogenous lung inflammation in ARDS

24

Clinical management of ARDS:
Treatment for hypoxemia when PEEP and FiO2 titration are not effective

  • A number of "salvage" strategies for the management of hypoxemic respiratory failure refractory to high inspired oxygen concentrations or PEEP have been described, including...
  • These techniques all attempt to...
  • Survival benefit for patients that receive...
  • The mechanism underlying the mortality improvement with patient paralysis for only 48 hours in an illness that typically last 2 weeks may reflect...

  • A number of "salvage" strategies for the management of hypoxemic respiratory failure refractory to high inspired oxygen concentrations or PEEP have been described, including...
    • Muscle paralysis
    • Prone ventilation
    • Extracorporeal membrane oxygenation (ECMO)
  • These techniques all attempt to...
    • Improve oxygenation while minimizing the high pressure or tidal volume associated with conventional mechanical ventilation
  • Survival benefit for patients that receive...
    • A paralytic agent (cisatracurium) during the initial 48 hours of ventilator management
    • The mortality benefit was impressive
  • The mechanism underlying the mortality improvement with patient paralysis for only 48 hours in an illness that typically last 2 weeks may reflect...
    • Better matching of the patient to the ventilator (called synchrony) during the early phases of ARDS

25

Clinical management of ARDS:
Treatment for hypoxemia when PEEP and FiO2 titration are not effective:
Patients with ARDS are often characterized by dependent lung consolidation

  • The ICU management of this patient population in the supine position favors...
  • Managing ARDS patients face down (prone position) could...
  • Extracorporeal membrane oxygenation (ECMO)
  • Early trials of ECMO in ARDS patients were complicated by...
  • Newer extracorporeal systems are able to use...
  • The patients referred to the ECMO treatment center had...

  • The ICU management of this patient population in the supine position favors...
    • Vascular flow to the dependent regions creating a region of low V/Q or shunt
  • Managing ARDS patients face down (prone position) could...
    • Improve the severe hypoxemia as blood flow would be redistributed by gravity to more normal lung regions
  • Extracorporeal membrane oxygenation (ECMO)
    • Provides blood oxygenation and carbon dioxide removal by passing the blood through an external system
    • ECMO should, in theory, provides the most efficient method to minimize ventilator induced lung injury in the ARDS patients
  • Early trials of ECMO in ARDS patients were complicated by...
    • A high bleeding rate and infectious complications
  • Newer extracorporeal systems are able to use...
    • Veno-venous or single cannula connections which have improved the safety of this form of treatment
  • The patients referred to the ECMO treatment center had...
    • A better outcome, although a significant fraction of these patients did not receive ECMO

26

Clinical management of ARDS:
Fluid management in ARDS

  • The capillary leak
  • ARDS often occurs in the setting of...
  • Cardiac function in these conditions requires...
  • This requires the clinician to resuscitate the patient with...
  • This paradox is the challenge of...
  • Yet fluid resuscitation can aggravate...
  • Patients in the ICU normally accumulate...
  • A “conservative” or “dry” fluid management strategy...

  • The capillary leak
    • Characteristic of ARDS
    • Leads to the development of greater pulmonary edema for any given level of left ventricular pressure elevation (ie LVEDP as reflected by the PAOP pressure)
  • ARDS often occurs in the setting of...
    • Sepsis or pneumonia and the heart has undergone a shift of the Starling curve to the right
  • Cardiac function in these conditions requires...
    • A higher filling pressure to maintain cardiac output leading
  • This requires the clinician to resuscitate the patient with...
    • Large volumes of IV fluid
    • This fluid-loading requirement can lead to greater lung water and worsening of the ARDS condition
  • This paradox is the challenge of...
    • Fluid management in the patient with ARDS
    • The conditions that produce ARDS require fluid resuscitation to maintain organ flow and blood pressure
  • Yet fluid resuscitation can aggravate...
    • The severe hypoxemia, which characterizes the disease
  • Patients in the ICU normally accumulate...
    • About 7 liters of intravenous fluid over the first 7 days of their ARDS illness
  • A “conservative” or “dry” fluid management strategy...
    • Reduced the time patients spent on mechanical ventilation although no improvement in mortality was recognized

27

Clinical management of ARDS:
ICU care in ARDS

  • The previously recognized mortality rate of ARDS in the 1980’s 
  • In the more recent series
  • The specific factors which have contributed to this improvement 

  • The previously recognized mortality rate of ARDS in the 1980’s
    • ~50-70%
  • In the more recent series
    • This has been reduced in the more recent series to a mortality rate of ~25-30%.
  • The specific factors which have contributed to this improvement 
    • Multifactorial
    • Likely relate to better patient support to minimize complications associated with a long ICU illness

28

Clinical management of ARDS:
ICU care in ARDS

  • The majority of ARDS survivors...
  • However, even at one year, these ARDS survivors still...
  • The reduction in physical function characteristic of ARDS survivors has been attributed to...
  • This finding has placed a recent focus in ICU’s on limiting...

  • The majority of ARDS survivors...
    • Recover their lung function by 3 months following the lung injury insult
  • However, even at one year, these ARDS survivors still...
    • Demonstrate ignificant reductions in their walking distance, quality of life parameters,
    • Often suffer from neuropsychiatric syndromes suggestive of post traumatic stress
  • The reduction in physical function characteristic of ARDS survivors has been attributed to...
    • Prolonged periods of immobility during the period of mechanical ventilation
  • This finding has placed a recent focus in ICU’s on limiting...
    • Sedation use during the illness and focusing on early mobility of the patient

29

Summary

  • ARDS 
  • The syndrome is characterized by...
  • Disease management focuses on...
  • Patient survival 

  • ARDS
    • A clinical syndrome in the lung precipitated by a number of predisposing conditions and disease modifiers
    • Diffuse alveolar filling disorders with a recognized pathologic evolution characterized by inflammatory lung injury and subsequent repair
  • The syndrome is characterized by...
    • Severe hypoxemia due to non-hydrostatic pulmonary edema
  • Disease management focuses on...
    • Support by mechanical ventilation with strategies to minimize ventilator associated lung injury
  • Patient survival
    • Has improved significantly over the recent years despite the lack of a new specific pharmacologic intervention

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