Resp - ARDS

Question 1

Berlin definision of ARDS

Answer 1

Acute, diffuse inflammatory lung injuryLeads to increased vascular permeability Increased lung weight and loss or aerated tissueCausing hypoxaemia bilateral radiographic opacitiesAssociated with: Increased venous admixture Increased physiological dead space Decreased lung compliance

Question 2

What as the problem with former definitions

Answer 2

No clarity of what ACUTE meantNo inclusion of risk factors for ARDSVariability of CXR interpretationLess PCWP being used (initially they wanted <18mmHg not due to LVF)No PEEP given in the definition

Question 3

Oygenation criteria for ARDS

Answer 3

PF ratio:Mild 200-300 (26.7 to 40 kPa)Mode 100-200 (13.3 to 26.7)Severe < 100 ( <13.3 kPa)All with at least PEEP/CPAP 5cmH2O

Question 4

Diagnostic criteria

Answer 4

TIMING - develops in 1 week of insult/resp symptomsRADIOLOGY - bilateral opacities not explained by effusion, collapse or nodulesResp failure - not explained by LVF or fluid overloadOxygenation (PF)Has to be ventilated (invasive or non-invasive with PEEP > 5)

Question 5

Causes of ARDS

Answer 5

Pulmonary and Extra PulmonaryPulm Extra-pulm Pneumonia Sepsis Pulm Contusion Burns Aspiration pneumonitis Major trauma Inhalational injury TRALI Pulm vasculitis Severe acute panc Drowning Cario bypass (pump lung)

Question 6

Pathophysiology of ARDS

Answer 6

Three phases - Exudate, Proliferative, Fibrotic

Exudative - 2-4 days   Inflammation to epithelium  Leak protein rich fluid in alveoli and interstitium  Destroy pulm vascular bed  Microthrombus formation

VQ mismatch, hypoxia Reduced lung complianceProliferative (4-7) Type II pneumocytes and fibroblasts Alveolar fibrin deposition Exudate turns to scar formationFibrotic stage )7-14 Fibrosis and underlying structural damage

Question 7

Additional tests in ARDS

Answer 7

Bloods - FBC, U&E, LFT, CRP, Coag, Amylase/Lipase, CulturesABG - quantify PF CXR/CT chestEcho if no known risk factors for ARDS

Question 8

Name the mechanisms by which ventilator induced lung injury occurs

Answer 8

Volutrauma (overdistend alveloi)Barotrauama (high pressure injury)Atelectotrauma (shearing from collapse and re-expansion)Biotrauma (inflammation from high volumes)

Question 9

List the various ventilatory strategies

Answer 9

Lung protective ventilationNeuromuscular blocking agentsRecruitment manoeuvresDecremental PEEPProneECMOOscilator(Steroids and Nitric Oxide)

Question 10

Describe Lung protective vent

Answer 10

Low Tv - 5-7 ml/kg of IBWHigh resp rate but less than 35/minPermissive hypercapnoea - higher PaCO2 so long as pH >7.2 (except in TBI)Aim SaO2 88-95%Consider prolonged I:E or inverse ration ventilationPEEP > 5cm Find optimum PEEP - point of best compliance Use FiO2/PEEP increments from tablesMaintain plateau pressure below 30cm455445

Question 11

Evidence for NMBD in ARDS

Answer 11

ACURASYS TrialCisatracurium versus placeboImproved 90 day mortality when PF ratio<120Increased vent free days

Question 12

Evidence for recruitment/decrimental peep

Answer 12

2016In moderate-severe ARDS, recruitment improved oxygenation and lung mechanicsNo mort benefit

Question 13

Evidence for proning

Answer 13

PROSEVA trial50% reduction in mortality ventilated and proned for 16 hours a dayNNT = 6

Question 14

Evidence for oscilators

Answer 14

OSCAR - no mortality benefityOSCILLATE - evidence of harm

Question 15

Evidence for steroids

Answer 15

Meta analysis 1995 - increased harms no benefitsSteinberg 2006 - methylpred - increased vent free days BUT no difference in 60 day mortIncreased myopathy2007 - methylpred infusion - improved organ dysfunction, LOS, BUT many more vasopressor dependent patients in the placeboADRENAL trial - shocl resolved and less time on vent but NO difference in mortality

Question 16

Components of the Murrary Score

Answer 16

PF ratioPEEPComplianceCXR (quadrants affected)

Question 17

What Murray score should prompt ECMO

Answer 17

Greater than or equal to 3

Question 18

Evidence for ECMO

Answer 18

CESAR trial - improved mortality| Many patients moved to tertiary centre didnt get ecmom

Question 19

Types of ECMO

Answer 19

V-V - facilitaties gas exchange, no haem supportV-A haem support and gas exchangeA-V - rare - uses own system as pumpECCO2R removes CO2 whilst o2 is provided by ventilation

Question 20

Indications for ECMO VA

Answer 20

Cardiogenic shock of almost any cause        Myocarditis        Intractilbe arrhytmia        Overdose with cardiac depression (LAs)        PE        Anaphylaxis

Weaning from CPBBridge to transplantPrimary graft failureChronic cardiomyopathyPulmonary hypertension AFTER endarterctomyECLS

Question 21

Indications for VV ECMO

Answer 21

Any REVERSIBLE cause of resp failureARDS with bacterial/viral pneumoniaLung transplnt Bridge Primary graft failure Intra-opLung rest Contusion (trauma) Smoke ObstructionPulm HaemorrhageStatus asthmaticus

Question 22

Contraindications to ECMO

Answer 22

Absolute - irreversible organ damage, failure, not a transplant candidateAdvanced malignancyChronic severe pulmonary hypertensionRelative: Age over 75 Polytrauam with many bleeding sites CPR >60minutesVA - Aortic regurg severe Aortic dissectionVV - Unsupoortable cardiac failure Severe pulm hypertension Cardiac arrest

Question 23

Complications of ECMO

Answer 23

Cannula, Antocoag, Equipment

Cannula    PTx    Vascular disruption    Infection    Emboli    Bleed

Anticoag - heparin, haemrrhaheHITEquipment - pump and oxygenation failureExsanguination

Question 24

Equipment for ECMO

Answer 24

CannulaeTubing with heparin (systemic)Pump - external pump with centrifuge or rollerMembrane oxygenatorHeat exchangerGas blender