Case discussion Acute severe asthma during pregnancy J.G. van der Hoeven
Case (1) 32-year-old female - gravida 3 - para 2 Previous medical history - asthma Pregnant (33 w) Acute onset fever with wheezing and progressive dyspnea despite appropriate therapy (antibiotics, oral prednisone and β2-mimetics)
Case (2) At arrival in the ED - almost unable to speak, silent chest, HR 145, RR 180/100, AVPU Chest X-ray: small infiltrate RLL SpO2 (5 L O2) 87% What would you do? ph 7.13 - PaCO2 78 mmhg - PaO2 84 mmhg
Normal pregnancy?
Short trial of NIV After 30 minutes: ph 7.08 - PaCO2 89 mmhg - PaO2 81 mmhg Was this a good idea?
Non-Invasive Ventilation Alternative to intubation Objectives of NIV NIV could be tried Prevent ARF Alert Stable HD Able to protect A Prevent intubation Severe gas exchange problems Profound respiratory acidosis Pump-failure Life-threatening complications Forget NIV!! Bronchodilation Severity of asthma attack Remember two phenotypes Scala R. Respiratory Care 2010;55:630-637
When using NIV... Look for patient-ventilator asynchrony Sputum retention may increase High flow rate and airway dryness may increase bronchial hyper-reactivity Monitor carefully in an ICU environment and have intubation equipment ready So - what is the next step?
Case (3) Successfully intubated Initially paralysed Motivate your ventilator settings What is the effect of acidosis on uterine BF?
Why do patients die from severe asthma? CPR before admission or during ET intubation (frequent) Severe bilateral barotrauma (past: frequent, now: rare) Severe persistent hypoperfusion (past: frequent, now: rare) Reason: avoidance of excessive dynamic hyperinflation
Avoiding excessive DH means TEXP Low tidal volume (± 6-8 ml/kg IBW) Low RR (6-10/min) High inspiratory flow rate Avoidance of PEEP (during CMV) NIV X X X Monitoring excessive DH is essential How?
Measures for DH End-inspiratory volume above FRC > 20 ml/kg the best predictor for barotrauma and hypotension End-inspiratory alveolar pressure Codependent on lung- and chest wall compliance Intrinsic PEEP very weak relation with barotrauma and hypotension Pplat tidal volume Pplat - PEEPi NIV X X X
Ventilator STOP Lung volume } V e i FRC Vei should be < 20 ml/kg
Paradoxal Bifasic Classic
Uterine BF Probably not much influenced by moderate hypercapnia but severe hypercapnia induces vasoconstriction (animal experiments)
Case (4) Tv 7 ml/kg, PEEP 0, RR 10, FiO2 60%, I:E 1:6 VEI 26 ml/kg - Pplat 34 cm H2O ph 6.99 - PaCO2 98 mmhg - PaO2 91 mmhg Low dose NE necessary to maintain BP Any good ideas?
Case (5) Fetal monitoring: normal heart rate, decreased variability and no accelerations or decelerations
Case (6) Improve ventilator settings? Spontaneous breathing - assisted ventilation? Delivery? Bicarbonate infusion? Extracorporeal CO2 removal?
CO2 production Glucose + O2 Energy + CO2 ± 200 ml/min AVCO2 difference = 40 ml per liter blood CO of ± 5L/min necessary to remove CO2 load
Mixed venous blood contains 52 ml CO2 / 100 ml
Therefore... We only need to clear 400 ml of blood of the complete CO2 content to balance VCO2 Because in contrast to alveoli the sweep gas contains no CO2, the gradient is sufficient to remove all CO2 in a single pass
General principle Sweep gas = airflow Blood with CO2 removed CO2 Internal Jugular vein Determinants of gas exchange Diffusion gradient Membrane-blood contact time Membrane diffusion characteristics Femoral vein Membrane lung Pump Blood containing CO2
Potential indications Treatment of unacceptable hypercapnia during lung protective ventilation (ARDS and acute severe asthma) Avoiding invasive mechanical ventilation Bridge to lung transplant
Beneficial effects of CO2 Improves tissue oxygenation Improves lung compliance by increasing surfactant production and dilates small airways May reduce the risk of VILI
Case (7) After extensive discussion: ECCO2R Canulation of right IJV Intensive fetal monitoring - no delivery Rapid decrease in PaCO2
ECCO2R
Case (8) Slow recovery Assisted ventilation without major dyssynchrony Normal delivery (healthy boy) at 38 weeks