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ARDS-Hoover - What’s New In Pediatric ARDS Nancy G Hoover...

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Unformatted text preview: What’s New In Pediatric ARDS Nancy G. Hoover, MD Medical Director, PICU Walter Reed AMC New and Improved Acute Respiratory Distress Syndrome Ashbaugh, Lancet, 1967 Adult Respiratory Distress Syndrome To distinguish from neonatal HMD/RDS Acute Respiratory Distress Syndrome American­European Consensus conference, 1994 ARDS: New Definition ARDS: New Definition Criteria Acute onset Bilateral CXR infiltrates PA pressure < 18 mm Hg Classification Acute lung injury ­ PaO2 : F1O2 < 300 Acute respiratory distress syndrome ­ PaO2 : F1O2 < 200 1994 American-European Consensus Conference Clinical Disorders Associated with Clinical Disorders Associated with ARDS Direct Injury Common Causes Pneumonia Gastric aspiration Less Common Causes Pulmonary contusion Fat emboli Near drowning Inhalational injury Indirect Injury Common Causes Sepsis Shock after severe trauma Less Common Causes Cardiopulm. bypass Drug overdose Acute pancreatitis Massive blood transfusions The Problem: Lung Injury The Problem: Lung Injury Davis et al., J Peds 1993;123:35 Noninfectious Pneumonia 14% Infectious Pneumonia 28% Cardiac Arrest 12% Hemorrhage 5% Trauma 5% Other 4% Septic Syndrome 32% Etiology In Children ARDS ­ Pathogenesis ARDS ­ Pathogenesis Instigation Endothelial injury: increased permeability of alveolar ­ capillary barrier Epithelial injury : alveolar flood, loss of surfactant, barrier vs. infection Proinflammatory mechanisms ARDS Pathogenesis ARDS Pathogenesis Resolution Equally important Alveolar edema ­ resolved by active sodium transport Alveolar type II cells ­ re­epithelialize Neutrophil clearance needed ARDS ­ Pathophysiology ARDS ­ Pathophysiology Decreased compliance Alveolar edema Heterogenous “Baby Lungs” Phases of ARDS Phases of ARDS Acute ­ exudative, inflammatory (0 ­ 3 days) Subacute ­ proliferative (4 ­ 10 days) Chronic ­ fibrosing alveolitis ( > 10 days) Phases of ARDS Phases of ARDS ARDS ­ Outcomes ARDS ­ Outcomes Most studies ­ mortality 40% to 60% Majority of deaths sepsis or MOD rather than primary respiratory Outcomes similar for adults and children Mortality may be decreasing 53/68 % 39/36 % ARDS ­ Principles of Therapy ARDS ­ Principles of Therapy Provide adequate gas exchange Avoid secondary injury It would seem ironic that the very existence of humans is fully dependent on a gas that, in excess quantities, is toxic and lethal Lynn D. Martin Therapies for ARDS Therapies for ARDS Innovations: iNO PLV Proning Surfactant AntiInflammatory Mechanical Ventilation ARDS Gentle ventilation: Permissive hypercapnia Low tidal volume Open-lung HFOV Extrapulmonary Gas Exchange The Dangers of Overdistention The Dangers of Overdistention Repetitive shear stress inflammatory response air trapping Phasic volume swings: volutrauma Injury to normal alveoli The Dangers of Atelectasis compliance intrapulmonary shunt FiO2 WOB inflammatory response Lung Injury Zones Overdistention 20 10 “Sweet Spot” Atelectasis 0 Lung Volume (ml/kg) 13 33 Ai rw ay Pressu re (cm H 20) 38 “Mechanical” Therapies in ARDS Lower tidal volumes but avoidance of atelectasis with higher PEEP Permissive hypercapnia HFOV Prone positioning Lower Tidal Volumes for ARDS Lower Tidal Volumes for ARDS Multi­center trial, 861 adult ARDS Randomized: Tidal volume 12 cc/kg Plateau pressure < 50 cm H2O vs. Tidal volume 6 cc/kg Plateau pressure< 30 cm H2O ARDS Network, NEJM, 342: 2000 Lower Tidal Volumes for ARDS Lower Tidal Volumes for ARDS 40 22 35 de % s re a c e * Traditional Lower 30 25 Percent 20 * 15 10 5 0 * p < .001 Death Vent free days ARDS Network, NEJM, 342: 2000 Ventilator Goals Ventilator Goals Set the PEEP slightly higher than the lower inflection point Lower tidal volume (generally < 6 mL/kg) Static peak pressure <40 cm H20 Wean oxygen to <60% Permissive Hypercapnia Permissive Hypercapnia Defined: presence of hypercapnia in the setting of a mechanically ventilated patient receiving limited inspiratory pressures and reduced tidal volumes Hickling, Int Care Med, 1990 Physiologic Effects of Physiologic Effects of Hypercapnia RESP: Net effect is improvement in oxygenation by enhancing hypoxic pulmonary vasoconstriction and decreases intrapulmonary shunting Right­shift of oxygen­hemoglobin dissociation curve Physiologic Effects of Physiologic Effects of Hypercapnia CV: Net effect is often hemodynamic compromise Sympathetic stimulation with increased C.O. Increased HR and SV, decreased SVR Intracellular acidosis of cardiomyocyte is reversible when due to hypercarbia compared to metabolic acidosis When combined with high PEEP strategy, can lead to severely decreased preload and cardiovascular compromise Physiologic Effects of Physiologic Effects of Hypercapnia RENAL: Compensatory bicarb reabsorption Acidosis leads to direct renal vasoconstriction Sympathetic­meditated release of norepinephrine (NE) Indirectly, hypercapnia causes a decrease in SVR that in turn releases NE, stimulates the renin­angiotensin­aldosterone system, leading to a further decrease in renal blood flow Permissive Hypercapnia Permissive Hypercapnia Is it worth it? Early adult ARDS trial showed a reduction in expected mortality of 56% to an actual mortality of 26% Hickling, CCM, 1994 Included in adult trauma patients protocol for mechanical ventilation Nathens, J Trauma, 2005 Several pediatric studies showing benefit when used in conjunction with low TV and high PEEP Sheridan, J Trauma, 1995 Paulson, J Pediatr, 1996 Caution in patients with elevated ICP High Frequency High Oscillation: Oscillation: A Whole Lotta Whole Shakin’ Goin’ On Shakin’ It’s not absolute pressure, but volume or pressure swings that promote lung injury or atelectasis. Reese Clark High Frequency Ventilation Rapid rate Low tidal volume Maintain open lung Minimal volume swings Differences Between CMV and HFOV Rate (BPM) Tidal volume (cc/kg) Alveolar pressure swings (cmH20) End exp. lung volume CM V 0-120 4-20 5-50 HFV 120-1200 0.1-5 0.1-5 lo w high HFOV vs. CMV in Pediatric HFOV vs. CMV in Pediatric Respiratory Failure: Results Greater survival without severe lung disease Greater crossover to HFOV and improvement Failure to respond to HFOV strong predictor of death Arnold et al, CCM, 1994 40 HFOV vs. CMV in Pediatric Respiratory Failure 20 * Survival with CLD% 0 HFOV CV CV to HFOV HFOV to CV ­Arnold et al, CCM, 1994 HFOV: Outcomes of Randomized Controlled Trials Reduces cost, severity of chronic lung disease and decreases airleak in neonatal RDS Decreases need for ECMO in eligible neonates Improves survival without CLD in pediatric ARDS Indications for HFOV Severe persistent airleak Neonatal: HMD (*) Pneumonia Meconium aspiration Lung hypoplasia Acute respiratory distress syndrome Is turning the ARDS patient “prone” helpful? Prone Positioning in ARDS Prone Positioning in ARDS Theory: let gravity improve matching perfusion to well­ventilated lung Improvement is immediate Decreased shunt: improved PaO2 but variable (75%) Uncertain effect on outcome Prone Positioning in Adult ARDS Prone Positioning in Adult ARDS Randomized trial Standard therapy vs. standard + prone positioning Improved oxygenation No difference in mortality, time on ventilator No difference in complications Gattinoni et al., NEJM, 2001 Conflicting Evidence for Proning? Conflicting Evidence for Proning? Mancebo, Am J of Resp & CCM, 2006 136 adults, randomized to 20 h/day proning within 48h of intubation for severe ARDS Same ventilator treatment protocols in both groups 25 % relative reduction in ICU mortality Curley, JAMA, 2005 Shorter proning times and multiple protocols for vent mgt with lung­protective stragegy and weaning, sedation, nutrition, etc Only 8% mortality and no benefit from prone positioning Pharmacological Therapies in ARDS Pharmacological Therapies in ARDS Surfactant iNO Steroids Partial Liquid Ventilation Surfactant in ARDS Surfactant in ARDS ARDS: surfactant deficiency surfactant present is dysfunctional Surfactant replacement improves physiologic function Calf’s Lung Surfactant Extract in Acute Calf’s Lung Surfactant Extract in Acute Pediatric Respiratory Failure Multicenter trial­uncontrolled, observational Calf lung surfactant (Infasurf) ­ intratracheal Immediate improvement and weaning in 24/29 children with ARDS and 14% mortality Wilson et al, CCM, 24:1996 In several other studies, there is no evidence for sustained benefit from Surfactant administration Wilson et al, JAMA, 2005 Steroids in ARDS Steroids in ARDS Theoretical anti­inflammatory, anti­fibrotic benefit Previous randomized studies Acute use (1st 5 days) No benefit Increased 2° infection Effects of Prolonged Steroids in Effects of Prolonged Steroids in Unresolving ARDS Randomized, double­blind, placebo­ controlled trial Adult ARDS ventilated for > 7 days without improvement Randomized: Placebo Methylprednisolone 2 mg/kg/day x 4 days, tapered over 1 month Meduri et al, JAMA, 1998 Steroids in Unresolving ARDS Steroids in Unresolving ARDS By day 10, steroids improved: PaO2/FiO2 ratios Lung injury/MOD scores Static lung compliance Steroids decreased procollagen metabolites 24 patients enrolled; study stopped due to survival difference Meduri et al, JAMA, 1998 Steroids in Unresolving Steroids in Unresolving ARDS 100 90 80 70 60 50 40 30 20 10 0 Steroid Placebo * * ICU survival Hospital survival * p<.01 What about after first 28 days? What about after first 28 days? NHLBI ARDS Clinical Trials Network, NEJM, 2006 180 adult patients with ARDS >7 days No difference in mortality with steroids EXCEPT, if the patient was entered into the study after 14 days of ARDS THEN, there was an increase in 60 and 180 day mortality Inhaled Nitric Oxide in Inhaled Nitric Oxide in Respiratory Failure Neonates Beneficial in term neonates with PPHN Decreased need for ECMO Adults/Pediatrics Benefits ­ lowers PA pressures, improves gas exchange Randomized trials: No difference in mortality or days of ventilation ECMO and NO in Neonates ECMO and NO in Neonates ECMO improves survival in neonates with PPHN (UK study) iNO decreases need for ECMO in neonates with PPHN: 64% vs 38% Clark et al, NEJM, 2000 Effects of Inhaled Nitric Oxide In Effects of Inhaled Nitric Oxide In Children with AHRF Randomized, controlled, blinded multi­ center trial 108 children, median age 2.5 years Entry: OI > 15 x 2 Randomized: Inhaled NO 10 ppm vs. mechanical ventilation alone Dobyns, et al., J. Peds, 1999 Inhaled NO and HFOV In Inhaled NO and HFOV In Pediatric ARDS 80 70 71 60 50 58 40 53 58 30 20 Survival % 10 0 CMV CMV + NO HFOV HFOV + NO Dobyns et al., J Peds, 2000 Partial Liquid Ventilation Partial Liquid Ventilation Mechanisms of action oxygen reservoir recruitment of lung volume alveolar lavage redistribution of blood flow anti­inflammatory Liquid Ventilation Liquid Ventilation Pediatric trials started in 1996 Partial: FRC (15 ­ 20 cc/kg) Study halted 1999 due to lack of benefit Adult study 2001 no effect on outcome ARDS­ “Mechanical” Therapies Low tidal volumes Outcome benefit in large study Prone positioning Unproven outcome benefit Open­lung strategy HFOV ECMO Outcome benefit in small study Outcome benefit in small study Proven in neonates unproven in children Pharmacologic Approaches Pharmacologic Approaches to ARDS: Randomized Trials Steroids ­ acute no benefit ­ fibrosing alveolitis lowered mortality, small study Surfactant possible benefit in children Inhaled NO no benefit PLV no benefit “…We must discard the old “… approach and continue to search for ways to improve mechanical ventilation. In the meantime, there is no substitute for the clinician standing by the ventilator…” Martin J. Tobin, MD If you think about ECMO, it is worth a call to consider ECMO Pediatric ECMO Pediatric ECMO Potential candidates Neonate ­ 18 years Reversible disease process Severe respiratory/cardiac failure < 10 days mechanical ventilation Acute, life­threatening deterioration Impact of ECMO on Survival in Impact of ECMO on Survival in Pediatric Respiratory Failure Retrospective, multicenter cohort analysis 331 patients, 32 hospitals Use of ECMO associated with survival (p < .001) 53 diagnosis and risk­matched pairs: ECMO decreased mortality (26% vs 47%, p < .01) -Green et al, CCM, 24:1996 Impact of ECMO on Survival in Impact of ECMO on Survival in Pediatric Respiratory Failure 90 80 % Mortality 70 60 50 ECMO N on­ ECMO 40 30 20 10 0 p<0.05 < 25% 25­ 50% 50­ 75% mortality risk quartile > 75% Green et al, CCM, 1996 ...
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