UTHSCSA Pediatric Resident Curriculum for the PICUUTHSCSA Pediatric Resident Curriculum for the PICU

RESPIRATORY FAILURE RESPIRATORY FAILURE

& ARDS& ARDS

RESPIRATORY FAILURERESPIRATORY FAILURE Inability of the pulmonary system to meet the metabolic Inability of the pulmonary system to meet the metabolic

demands of the body through adequate gas exchange.demands of the body through adequate gas exchange. Two types of respiratory failure:Two types of respiratory failure:

HypoxemicHypoxemic HypercarbicHypercarbic

Each can be further divided into acute and chronic.Each can be further divided into acute and chronic. Both types of respiratory failure can be present in the same Both types of respiratory failure can be present in the same

patient.patient.

CENTRAL ETIOLOGIESCENTRAL ETIOLOGIES Trauma: head injury, asphyxiation, hemorrhageTrauma: head injury, asphyxiation, hemorrhage Infection: meningitis, encephalitisInfection: meningitis, encephalitis TumorsTumors Drugs: narcotics, sedativesDrugs: narcotics, sedatives Neonatal apneaNeonatal apnea Severe hypoxemia or hypercarbiaSevere hypoxemia or hypercarbia Increased ICP from any of the above causesIncreased ICP from any of the above causes

OBSTRUCTIVE ETIOLOGIESOBSTRUCTIVE ETIOLOGIESUpper AirwayUpper Airway Anatomic: choanal atresia, Anatomic: choanal atresia,

tracheomalacia, tonsillar tracheomalacia, tonsillar hypertrophy, laryngeal web, hypertrophy, laryngeal web, vascular rings, vocal cord vascular rings, vocal cord paralysis, macroglossiaparalysis, macroglossia

Aspiration: mucus, foreign body, Aspiration: mucus, foreign body, vomitusvomitus

Infection: epiglottitis, abscesses, Infection: epiglottitis, abscesses, laryngotracheitislaryngotracheitis

Tumors: hemangioma, cystic Tumors: hemangioma, cystic hygroma, papilloma, hygroma, papilloma,

LaryngpospasmLaryngpospasm

Lower AirwayLower Airway Anatomic: bronchomalacia, Anatomic: bronchomalacia,

lobar emphysemalobar emphysema Aspiration: FB, mucus, Aspiration: FB, mucus,

meconium, vomitusmeconium, vomitus Infection: pneumonia, Infection: pneumonia,

pertussis, bronchiolitis, CFpertussis, bronchiolitis, CF Tumors: teratoma, Tumors: teratoma,

bronchogenic cystbronchogenic cyst BronchospasmBronchospasm

RESTRICTIVE ETIOLOGIESRESTRICTIVE ETIOLOGIESLung ParenchymaLung Parenchyma Anatomic: agenesis, cyst, Anatomic: agenesis, cyst,

pulmonary sequestrationpulmonary sequestration AtelectasisAtelectasis Hyaline membrane diseaseHyaline membrane disease ARDSARDS Infection: pneumonia, Infection: pneumonia,

bronchiectasis, pleural bronchiectasis, pleural effusion, effusion, Pneumocystis cariniiPneumocystis carinii

Air leak: pneumothoraxAir leak: pneumothorax Misc: hemorrhage, edema, Misc: hemorrhage, edema,

pneumonitis, fibrosispneumonitis, fibrosis

Chest WallChest Wall Muscular: diaphragmatic Muscular: diaphragmatic

hernia, myasthenia gravis, hernia, myasthenia gravis, muscular dystrophy, muscular dystrophy, botulismbotulism

Skeletal: hemivertebrae, Skeletal: hemivertebrae, absent ribs, fused ribs, absent ribs, fused ribs, scoliosisscoliosis

Misc: distended abdomen, Misc: distended abdomen, flail chest, obesityflail chest, obesity

HYPOXEMIAHYPOXEMIAV/Q mismatchV/Q mismatch

Most common reason. Blood perfuses non-ventilated lung. Seen Most common reason. Blood perfuses non-ventilated lung. Seen in atelectasis, pneumonia, bronchiectasisin atelectasis, pneumonia, bronchiectasis

Global hypoventilationGlobal hypoventilation:: apnea apnea

Right-to-left shuntRight-to-left shunt Intracardiac lesions, e.g., tetralogy of FallotIntracardiac lesions, e.g., tetralogy of Fallot

Incomplete diffusionIncomplete diffusion Oxygen must diffuse across increased distance secondary to Oxygen must diffuse across increased distance secondary to

interstitial edema, fibrosis, or hyaline membrane.interstitial edema, fibrosis, or hyaline membrane.

Low inspired FiOLow inspired FiO22: : high altitudehigh altitude

HYPERCARBIAHYPERCARBIAPump FailurePump Failure

Reduced central drive: apnea, metabolic alkalosis, drugs, Reduced central drive: apnea, metabolic alkalosis, drugs, brainstem injury, hypoxiabrainstem injury, hypoxia

Muscle fatigue: muscular dystrophyMuscle fatigue: muscular dystrophy Increased pulmonary workload: decreased compliance, Increased pulmonary workload: decreased compliance,

increased obstructionincreased obstruction

Increased COIncreased CO22 production production: : fever, seizure, malignant fever, seizure, malignant

hyperthermiahyperthermia

Increased dead spaceIncreased dead space: : V/Q mismatch (ventilation of V/Q mismatch (ventilation of non-perfused lung)non-perfused lung)

PHYSICAL EXAMPHYSICAL EXAM TachypneaTachypnea DyspneaDyspnea RetractionsRetractions Nasal flaringNasal flaring GruntingGrunting DiaphoresisDiaphoresis TachycardiaTachycardia HypertensionHypertension

Altered mental statusAltered mental status ConfusionConfusion AgitationAgitation RestlessnessRestlessness SomnolenceSomnolence

Cyanosis (need 5mg/dl Cyanosis (need 5mg/dl of unoxygenated blood)of unoxygenated blood)

CXR FINDINGSCXR FINDINGS CXR may be normal if problem is with upper airwayCXR may be normal if problem is with upper airway Can see hyperinflation, atelectasis, infiltrate, Can see hyperinflation, atelectasis, infiltrate,

cardiomegalycardiomegaly Additional studies may be needed, e.g., chest CT, Additional studies may be needed, e.g., chest CT,

barium swallow, echocardiogrambarium swallow, echocardiogram

BLOOD GASBLOOD GAS For any age patient, breathing room air, respiratory For any age patient, breathing room air, respiratory

failure is defined as arterial pCOfailure is defined as arterial pCO22 > 50mm Hg or arterial > 50mm Hg or arterial

pOpO22 < 60mm Hg. < 60mm Hg.

If the patient is hyperventilating, a normal pCOIf the patient is hyperventilating, a normal pCO22 is is

disturbing.disturbing. The above definition assumes the absence of an The above definition assumes the absence of an

anatomic shunt.anatomic shunt. Chronic hypercarbic respiratory failure will often have a Chronic hypercarbic respiratory failure will often have a

normal pH because of compensatory metabolic alkalosis.normal pH because of compensatory metabolic alkalosis.

MANAGEMENTMANAGEMENT

REMEMBER PALSREMEMBER PALSAAirwayirway

BBreathingreathing

CCirculationirculation

AIRWAYAIRWAY RepositioningRepositioning

Position of comfortPosition of comfort Jaw thrust/chin liftJaw thrust/chin lift

Oral airwayOral airway Unconscious patients onlyUnconscious patients only

Nasal trumpetNasal trumpet Nasal or mask CPAPNasal or mask CPAP Bag-mask ventilationBag-mask ventilation

Use during preparation for intubationUse during preparation for intubation

Tracheal intubationTracheal intubation

BREATHINGBREATHING Decrease respiratory workloadDecrease respiratory workload

ß-agonistsß-agonists Decadron or steroidsDecadron or steroids AntibioticsAntibiotics CPAPCPAP

Supplemental OSupplemental O22

Nasal cannulaNasal cannula Closed face maskClosed face mask Non-rebreatherNon-rebreather

Counteract drug effectsCounteract drug effects Bag-mask ventilationBag-mask ventilation Mechanical ventilationMechanical ventilation

CIRCULATIONCIRCULATION

Suppress anaerobic metabolism and acidosisSuppress anaerobic metabolism and acidosisCorrect anemia to improve oxygen deliveryCorrect anemia to improve oxygen deliveryEnsure adequate cardiac outputEnsure adequate cardiac output

Inotropes: oxygen, vasopressorsInotropes: oxygen, vasopressors Fluid bolusesFluid boluses

ARDSARDS A patient must meet all of the following: A patient must meet all of the following:

Acute onset of respiratory symptomsAcute onset of respiratory symptoms CXR with bilateral infiltratesCXR with bilateral infiltrates No evidence of left heart failureNo evidence of left heart failure PaOPaO22/FiO/FiO22 < 200mm Hg (regardless of PEEP) < 200mm Hg (regardless of PEEP)

American-European Consensus Conference on ARDS (Am J Resp Crit Care Med American-European Consensus Conference on ARDS (Am J Resp Crit Care Med 149:818, 1994)149:818, 1994)

The following are implied:The following are implied: Previously normal lungsPreviously normal lungs Decreased lung complianceDecreased lung compliance Increased shuntingIncreased shunting Hypoxemic respiratory failureHypoxemic respiratory failure

ETIOLOGYETIOLOGY ARDS represents about 3% of PICU admissions.ARDS represents about 3% of PICU admissions. Numerous precipitating events:Numerous precipitating events:

TraumaTrauma PneumoniaPneumonia BurnsBurns SepsisSepsis DrowningDrowning ShockShock

PATHOPHYSIOLOGYPATHOPHYSIOLOGY Acute InjuryAcute Injury Latent PeriodLatent Period Early Exudative PhaseEarly Exudative Phase Cellular Proliferative PhaseCellular Proliferative Phase Fibrotic Proliferative PhaseFibrotic Proliferative Phase

Royall and LevinJ Peds 112:169-180;335-347, 1988

PATHOLOGY OF ARDSPATHOLOGY OF ARDS

Green arrows point to hyaline membraneGreen arrows point to hyaline membrane

Blue arrows point to type II pneumocytes and alveolar macrophagesBlue arrows point to type II pneumocytes and alveolar macrophages

MANAGEMENTMANAGEMENT Meticulous supportive care is the mainstay of therapyMeticulous supportive care is the mainstay of therapy

Prevent secondary lung injuryPrevent secondary lung injury Ensure adequate cardiac outputEnsure adequate cardiac output Limit secondary infectionsLimit secondary infections DrugsDrugs Good nutritionGood nutrition

VENTILATOR STRATEGIESVENTILATOR STRATEGIESThe hallmark of ARDS is heterogeneous lung.The hallmark of ARDS is heterogeneous lung.

Limit BarotraumaLimit Barotrauma Keep PIP <35 cm HKeep PIP <35 cm H22OO

Use pressure-control Use pressure-control ventilationventilation

Use TV of 6-10cc/kgUse TV of 6-10cc/kg Keep rate <30 bpmKeep rate <30 bpm Permissive hypercapniaPermissive hypercapnia Use bicarb or THAM to Use bicarb or THAM to

keep pH >7.20keep pH >7.20

Limit OLimit O22 Toxicity Toxicity Give enough PEEP to Give enough PEEP to

lower FiOlower FiO22 to <60% while to <60% while

maintaining Omaintaining O22 >90%. >90%.

PEEP <15 cm HPEEP <15 cm H22O O

shouldn’t decrease shouldn’t decrease cardiac output.cardiac output.

Increase mean airway Increase mean airway pressure with inverse pressure with inverse ratio (I>E) ventilation.ratio (I>E) ventilation.

CARDIAC OUTPUTCARDIAC OUTPUT Keep cardiac output >4.5 L/min/mKeep cardiac output >4.5 L/min/m22.. Keep OKeep O22 delivery >600 ml O delivery >600 ml O22/min/m/min/m22..

Keep Hct >30%, higher if signs of heart failure.Keep Hct >30%, higher if signs of heart failure. Use inotropes to augment cardiac output.Use inotropes to augment cardiac output. Ensure adequate preload.Ensure adequate preload.

LIMIT SECONDARY INFECTIONSLIMIT SECONDARY INFECTIONS

Wash your hands.Wash your hands. Use the gut as soon as possible for nutrition and Use the gut as soon as possible for nutrition and

meds.meds. Discontinue indwelling catheters as soon as Discontinue indwelling catheters as soon as

possible.possible. Have high index of suspicion.Have high index of suspicion. Treat infections early, but tailor antibiotics to culture Treat infections early, but tailor antibiotics to culture

results.results.

DRUGSDRUGS Diuretics: a dry lung is a good lung.Diuretics: a dry lung is a good lung. InotropesInotropes Steroids: 2mg/kg/day begun after a week into the Steroids: 2mg/kg/day begun after a week into the

course may be of benefit, otherwise don’t use.course may be of benefit, otherwise don’t use. Pulmonary vasodilators (nitric oxide, prostaglandins, Pulmonary vasodilators (nitric oxide, prostaglandins,

nitroprusside): of little benefit. NO may be of benefit nitroprusside): of little benefit. NO may be of benefit in some patients.in some patients.

Surfactant replacement: probably no benefitSurfactant replacement: probably no benefit NSAIDs: no clinical benefitNSAIDs: no clinical benefit

NUTRITIONNUTRITION Ensure adequate calories as soon as possible:Ensure adequate calories as soon as possible:

50-60kcal/kg/day in infants50-60kcal/kg/day in infants 35-45kcal/kg/day in older children.35-45kcal/kg/day in older children.

After day 4, increase calories by 25-50% above After day 4, increase calories by 25-50% above baseline.baseline.

Begin enteral feeds as soon as is safe.Begin enteral feeds as soon as is safe. ““Pulmonary” formulas probably of little benefit.Pulmonary” formulas probably of little benefit.

MORTALITY/MORBIDITYMORTALITY/MORBIDITY Published mortality is 50% in children.Published mortality is 50% in children. Pulmonary failure accounts for only 15% of the Pulmonary failure accounts for only 15% of the

deaths. deaths. Lung function usually returns to normal within 18 Lung function usually returns to normal within 18

months after leaving the hospital.months after leaving the hospital.