Weaning and Extubation: A Pediatric Prespective

Weaning and Extubation: A Pediatric Perspective Ira M. Cheifetz, MD, FCCM, FAARC Professor of Pediatrics Chief, Pediatric Critical Care Medical Director, PICU & Peds Resp Care Duke Children’s Hospital

Weaning and Extubation ‘The separation of a patient from his ventilator is very nearly pure art.’ – Donald F. Egan, 1977 ‘Fundamentals of Respiratory Therapy’

Definitions  Weaning: transition from ventilatory support to complete spont breathing  Success: maintaining effective gas exchange with complete spont breathing  Failure: inability to sustain effective gas exchange w/o mechanical support within 48 hours of extubation

Definitions  Spontaneous breathing trial (SBT) – test of the ability to maintain complete spontaneous breathing (i.e., extubation readiness) – failure is the inability to maintain effective gas exchange with a RR within acceptable limits

Indications for Weaning  Improving underlying disease process  ‘Adequate’ gas exchange  No undue burden on respiratory muscles – cardiac insufficiency – significant hyperinflation – severe malnutrition – multiorgan system dysfunction / failure  Patient is capable of sustaining spontaneous ventilation as ventilator support is decreased.

Effort of Breathing  Respiratory rate  Spontaneous tidal volume  WOB – paradoxical breathing / retractions – esophageal manometry  Inspiratory pressure of a spont breath (Pi)  Maximal negative insp pressure (NIF)  O2 cost of breathing

Factors that Contribute to Insp WOB  ETT size / ventilator circuit deadspace  Demand valves in the circuit  Patient - ventilator dys-synchrony  Trigger: pressure vs. flow  Distal vs. proximal sensing (??)  Any additional load on resp muscles

Adequacy of Gas Exchange  Oxygenation – PaO2/FiO2 – Oxygenation index: (FiO2 x Paw) / PaO2 – alveolar-arterial O2 gradient – venous admixture; intrapulm shunt fraction  Ventilation – PaCO2 – physiological dead space – EtCO2 - PaCO2 difference – Fraction of ventilation provided by the vent

Vent Mode and Weaning Outcome  PSV decreased duration of weaning – Brochard, Am J Resp Crit Care Med, 1994  Multicenter center study in adults: – Esteban, N Engl J Med, 1995 – daily SBT led to extubation 3x faster than IMV and 2x faster than PSV – multiple daily SBTs were as successful as a daily trial

Prolonged Ventilation – ↑ nosocomial pneumonia – ↑ airway injury – ↑ VILI – ↑ LOV & LOS – ↑ cost – ↓ patient & family satisfaction

Failed Extubation – ↑ nosocomial pneumonia – ↑ airway injury – ↑ VILI – ↑ LOV & LOS – ↑ cost – ↓ patient & family satisfaction – mortality  Children requiring reintubation within 48 hrs had significantly  mortality than patients successfully extubated (20% vs. 2%, p < 0.001) Esteban, AJRCCM, 2001.

% spont breathing % spont breathing 100 0 Time of extubation Optimal Balance Weaning time 100 % ventilator support 0

Should all adult pts be gradually withdrawn from mech ventilation?  No!  Majority of adult patients who pass a SBT are extubated within 24 hours – Esteban, NEJM, 1995 – Brochard, AJRCCM, 1994

Should all peds pts be gradually withdrawn from mech ventilation?  Answer remains: No!  PALISI: 58% of pts initially tested with a minimal PS trial passed and were extubated – Randolph, JAMA 2002  77% of pts who underwent a SBT passed & were extubated without weaning – Farias, Inten Care Med, 1998

Weaning Protocols Study Date N ↓ LOV p Kollef 1997 357 1.4 d 0.029 Ely 1996 300 1.5 d 0.001 Marelich 2000 253 2.3 d 0.0001 Kollef, CCM, 1997 Ely, AJRCCM, 1996 Marelich, Chest, 2000

On the other hand….  No differences between protocol & non-protocol weaning for children.  Duration of weaning (n = 182; p=0.75) – 2.9 days in the ‘protocol’ groups (median 1.7 d) – 3.2 days in the ‘no protocol’ group (median 2.0 d)  Weaning protocols for ventilated pediatric pts with ALI do NOT shorten LOV. Randolph, JAMA, 2002.

Weaning & Sedation Randolph, JAMA, 2002.

Extubation Criteria in Adults  Respiratory frequency to tidal volume ratio – Yang, NEJM, 1991 – Tahvanainen, CCM, 1983  T-piece trials – Sahn, Chest, 1973  Negative insp effort measurements – Sahn, Chest, 1973  CROP index (compliance, rate, oxygenation, pressure) – Yang, NEJM, 1991

Extubation Criteria in Peds  No widely accepted criteria for predicting successful extubation for pediatric pts.  Successful extubation predictors:  Low Risk Value High Risk Value  Vtspont 6.5 ml/kg 3.5 ml/kg  FiO2 0.30 > 0.40  Paw < 5 cm H2O > 8.5 cm H2O  OI 1.4 > 4.5  FrVe 20% 30%  PIP 25 cm H2O 30 cm H2O  Cdyn 0.9 ml/kg/cm H2O < 0.4 ml/kg/cm H2O Khan, CCM, 1996.

Vd/Vt and Successful Extubation n=3 n=2 n=7 100% n=13 90% Hubble, CCM, 2000 80% 70% n=8 60% n=2 50% 40% n=3 30% n=4 20% 10% n=2 0% 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Vd / Vt

Vd/Vt and Extubation  Elevated physiologic dead space predicts  Elevated physiologic dead space predicts extubation failure extubation failure  Successful extubation in a heterogeneous  Successful extubation in a heterogeneous PICU population (p < 0.001) PICU population (p < 0.001) – Vd/Vt < 0.5: 24/25 (96%) – Vd/Vt < 0.5: 24/25 (96%) – Vd/Vt 0.5-0.65: 6/10 (60%) – Vd/Vt 0.5-0.65: 6/10 (60%) – Vd/Vt > 0.65: 2/10 (20%) – Vd/Vt > 0.65: 2/10 (20%) Hubble, CCM, 2000

General indications and contraindications for extubation  Indications  Contraindications – alert or easily – obtunded arousable – poor or absent cough – good cough and gag or gag – thin secretions easily – thick or copious cleared from airway secretions requiring – nl cardiac function frequent suctioning – no MOSF – cardiac insufficiency – MOSF

Causes for Extubation Failure Excessive resp effort 42% Poor resp effort 24% Inadequate gas exchange 18% Cardiovasc insufficiency 10% Neurologic 6%

SBT Recommendations  Perform a SBT when – FiO2 ≤ 0.40 PEEP ≤ 6 PIP ≤ 25 – sedation has been decreased or stopped – adequate insp drive – improvement or resolution of underlying cause – pharmacological control of bronchoconstriction – absence of significant resp acidosis

Weaning and Extubation: Conclusions  Not all patients require weaning  Extubation readiness testing decreases LOV  Ideal timing of extubation may still remain more clinical art than science – although this is changing with ERT

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Weaning and Extubation: A Pediatric Prespective

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