Postoperative Ventilation in Paediatric Cardiac Surgical Patients

Postoperative Ventilation Postoperative Ventilation in in

Paediatric cardiac Paediatric cardiac surgical patientssurgical patients

Dr Amarja Sachin Dr Amarja Sachin NagreNagre

MD, DM, FCAMD, DM, FCAwww.cardiacanaesthesia.in|Dr Amarjawww.cardiacanaesthesia.in|Dr Amarja

HFV & ECMO HFV & ECMO Revolution in paediatric Revolution in paediatric ventilation ventilation ? ?

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Know Abouts Know Abouts . . .. . . Limitations of conventional ventLimitations of conventional vent HFV : MechanismHFV : Mechanism TypesTypes Prone VentilationProne Ventilation ECMOECMO


Fast- tracking ?Fast- tracking ? Preoperative lung diseasePreoperative lung disease Alteration in lung compliance – CPB & Alteration in lung compliance – CPB &

anaesthesiaanaesthesia

Unstable postoperative hemodynamicsUnstable postoperative hemodynamics may demand prolong ventilationmay demand prolong ventilation


Conventional methodsConventional methods SIMV (vol control ) + PSSIMV (vol control ) + PS SIMV (pres control ) + PSSIMV (pres control ) + PS Pressure controlPressure control PRVCPRVC PSPS CPAPCPAP Volume supportVolume support


Advanced ModesAdvanced Modes Liquid ventilation – PPHLiquid ventilation – PPH Flow synchronization- pt triggers & Flow synchronization- pt triggers &

the ventilator changes flow to meet the ventilator changes flow to meet pt’s inspiratory needspt’s inspiratory needs

IRV , PC- IRVIRV , PC- IRV


CV ProblemsCV Problems Non-uniform inflation occuring in non-Non-uniform inflation occuring in non-

homogenous lungshomogenous lungs CMV’s with high PIPs CMV’s with high PIPs Those pressures are also transmitted to Those pressures are also transmitted to

the healthiest regions of lungsthe healthiest regions of lungs Over-distention and over-pressurization Over-distention and over-pressurization

produces volutrauma and barotraumaproduces volutrauma and barotrauma Inflammatory Cascade is triggeredInflammatory Cascade is triggered


Do we think beyond Do we think beyond

conventional conventional ventilation ventilation ??


HFOV can be used as a HFOV can be used as a bridgebridge to to ECMO in pts with intractable ECMO in pts with intractable cardiorespiratory conditionscardiorespiratory conditions


So, why consider HFV?So, why consider HFV? 3 Words: 3 Words: Small Tidal VolumesSmall Tidal Volumes Small Tidal Volumes allow gas exchange to Small Tidal Volumes allow gas exchange to

occur using extremely small volume occur using extremely small volume displacements of ventilatory gases displacements of ventilatory gases

Small Tidal Volumes < Anatomical Dead Small Tidal Volumes < Anatomical Dead SpaceSpace

Small Tidal Volumes allow safer use of Small Tidal Volumes allow safer use of Optimal PEEP minimizing the risk of Optimal PEEP minimizing the risk of atelectasis and oxygen toxicityatelectasis and oxygen toxicity

Often referred to as Lung Protective Often referred to as Lung Protective Ventilation/StrategyVentilation/Strategy


HistoryHistory

He wondered how dogs could pant indefinitely without flattering hypoxic or hypercapnic.

Henderson was intrigued by the shallow breathing of panting dogs in 1915


HFV EvolutionHFV Evolution

Evolved from studies of pulmonary Evolved from studies of pulmonary physiology using mathematics, fluid physiology using mathematics, fluid mechanics, and other engineering mechanics, and other engineering principles.principles.Facilitates gas exchange by sending a Facilitates gas exchange by sending a steady stream of very small tidal volumes steady stream of very small tidal volumes into the airways using relatively low PIPs into the airways using relatively low PIPs The further the gas goes into the airways, The further the gas goes into the airways, the lower those airway pressures are.the lower those airway pressures are.


The “Essentials” of HFVThe “Essentials” of HFV

Lungs inflation is essential to adequate the oxygenation

Maintenance of airway patency is essential to adequate the ventilation

Minimizing mechanically delivered VT is essential to prevention of lung injury

PEEP/MAP issues


CPAP with WobblesCPAP with Wobbles CPAP : sustained inflation & CPAP : sustained inflation &

recruitment of lungrecruitment of lung

Wobbles – alveolar ventilation & CO2 Wobbles – alveolar ventilation & CO2 removal – oscillating pressure removal – oscillating pressure waveform , adjustable frequency (Hz) waveform , adjustable frequency (Hz) at an adjustable amplitudeat an adjustable amplitude


How does HFV work?How does HFV work?Conventional studies indicate that smaller Conventional studies indicate that smaller tidal volumes are safer than larger tidal tidal volumes are safer than larger tidal volumes *volumes *As Tidal Volumes are pushed smaller and As Tidal Volumes are pushed smaller and smaller, two things must be raisedsmaller, two things must be raised

PEEP/MAP - to keep the lungs open PEEP/MAP - to keep the lungs open Rate - to maintain normal PaCO2Rate - to maintain normal PaCO2

*Kacmaerk RM, Chiche J-D. Resp. Care 1998;43:724-727 & Lee PC, Helemoortel CM,Cohn Sm, Fink MP. Chest 1990;97:430-434www.cardiacanaesthesia.in|Dr Amarjawww.cardiacanaesthesia.in|Dr Amarja

Airway Pressure PhobiasAirway Pressure Phobias

Monitoring and controlling HFV with Monitoring and controlling HFV with airway pressure instead of tidal airway pressure instead of tidal volumes creates problems for many volumes creates problems for many clinicianscliniciansPressure is a Pressure is a DependentDependent variable variableIt depends on gas flow, tidal volume, It depends on gas flow, tidal volume, airways resistance, and lung airways resistance, and lung compliancecompliance


MAP on HFVMAP on HFV Optimal MAP – decrease atelectasisOptimal MAP – decrease atelectasis decrease shuntsdecrease shunts better V/Q matchbetter V/Q match better oxygenationbetter oxygenation


2015105

Amplitude attenuates; PEEP stays constant, MAP declines

Paw

HFJV

P

2015105

Paw

HFOV

Amplitude attenuates;PEEP increases; MAP fixed when I:E = 1:1, less at 1:2

Trachea & Proximal Airways Distal Airways & Alveoli

Airway Pressures during HFV

P


Gas Transport and ExchangeGas Transport and Exchange

Conventional VentilationConventional VentilationAlveolar Ventilation = Rate x Tidal Alveolar Ventilation = Rate x Tidal VolumeVolume

High Frequency VentilationHigh Frequency VentilationAlveolar Ventilation = Rate x Tidal Alveolar Ventilation = Rate x Tidal Volume Volume 22


Mechanism of gas exchangeMechanism of gas exchange Theories : Theories : Bulk flow (as in CMV)Bulk flow (as in CMV) PendulluftPendulluft Asymmetric velocity profileAsymmetric velocity profile DispersionDispersion Collateral ventilationCollateral ventilation Cardiogenic mixingCardiogenic mixing Molecular diffusionMolecular diffusion


Benefits of HFVBenefits of HFV ‘‘Low stretch ‘ ventilation with continous Low stretch ‘ ventilation with continous

alveolar recruitment alveolar recruitment Adequate gas flow with small TVAdequate gas flow with small TV Preserves end exp lung volumePreserves end exp lung volume Keeps the lung openKeeps the lung open Minimizes cyclic stretchMinimizes cyclic stretch Avoids overdistension at end inspiration Avoids overdistension at end inspiration

by limiting TV & transpulm pressureby limiting TV & transpulm pressurewww.cardiacanaesthesia.in|Dr Amarjawww.cardiacanaesthesia.in|Dr Amarja

Classification of HFVClassification of HFV

TypeType

HFPPVHFPPV

HFJVHFJV

HFOVHFOV

FrequencyFrequency

1-2.5 Hz / 60-150cpm1-2.5 Hz / 60-150cpm

4-11Hz/ 240-660cpm4-11Hz/ 240-660cpm

8-30Hz/ 480-1800cpm8-30Hz/ 480-1800cpm


HFPPVHFPPV Here, TV is delivered via convective Here, TV is delivered via convective

air movement where TV exceeds the air movement where TV exceeds the dead spacedead space

Indicated – pts : hypoxemic & Indicated – pts : hypoxemic & hypercapic despite adequate & hypercapic despite adequate & appropiate conventional ventilationappropiate conventional ventilation

Fighting the ventilator is less in Fighting the ventilator is less in neonatesneonates


Contd . . . Contd . . .

In HFPPV : RR is increased to achieve In HFPPV : RR is increased to achieve MV , so the peak pressure remains lowMV , so the peak pressure remains low

As rate increases insp time decreases to As rate increases insp time decreases to allow adequate exhalation & prevent air allow adequate exhalation & prevent air trappingtrapping

MAP – may increase – barotraumaMAP – may increase – barotrauma IC bleedIC bleed cardiac compromisecardiac compromise


HFJVHFJV Rate – 240 to 660/minRate – 240 to 660/min Special adaptor is attached to ETT Special adaptor is attached to ETT Specially designed ETT – allows Specially designed ETT – allows

pulsed gas to exit inside the ETTpulsed gas to exit inside the ETT

Indications – PPHTN , restrictive lung Indications – PPHTN , restrictive lung diseases , pulmonary hypoplasia, air diseases , pulmonary hypoplasia, air leaksleaks


Contd . . .Contd . . . Jet Ventilation alongwith Jet Ventilation alongwith

conventional ventilation : conventional ventilation : 1) occasional sighs – surfactant ,1) occasional sighs – surfactant , prevent atelectasisprevent atelectasis 2) PEEP2) PEEP 3) continous gas is available at ETT3) continous gas is available at ETT for entrainment by Jetfor entrainment by Jet


HFJV Contd. . . HFJV Contd. . . Adv – equivalent ventilation at lowerAdv – equivalent ventilation at lower MAP MAP - limits effects of PPV on CV - limits effects of PPV on CV systemsystem - beneficial in pts with RV - beneficial in pts with RV dysfunction & after Fontandysfunction & after Fontan operationoperation


HFJV = Gentle VentilationHFJV = Gentle Ventilation

Time

CV = larger tidal volumes

*You must raise PEEP to maintain MAP for Stabilization / Oxygenation.

MAP

PEEP

Don’t let the MAP fall when initiating HFJV !!

MAP & HFJV

*


How does HFJV work?How does HFJV work?

HFV reduces physiologic dead space HFV reduces physiologic dead space volume by pulsing fresh gas through volume by pulsing fresh gas through the core or center of the airways & the core or center of the airways & dead space instead of pushing all the dead space instead of pushing all the dead space gas ahead of the fresh gasdead space gas ahead of the fresh gas


Flow StreamingFlow Streaming Allows HFV to use TV < anatomic dead space Allows HFV to use TV < anatomic dead space

volume because gas in the terminal airways volume because gas in the terminal airways gets replenished so rapidly that a substantial gets replenished so rapidly that a substantial Partial PressurePartial Pressure difference is established with difference is established with alveolar gas.alveolar gas.

This partial pressure difference facilitates This partial pressure difference facilitates DiffusionDiffusion, and good gas exchange results, and good gas exchange results

HFJV is especially good at creating flow HFJV is especially good at creating flow streaming because it squirts gas into the lungs streaming because it squirts gas into the lungs with a great deal of with a great deal of Velocity.Velocity.


Pressure Waveform Comparison required to reproduce similar PaCO2 and Ph

Boros, et al. Ped. Pulm. 1989;7:35-41

Time0 0.2 0.4 0.6 0.8

0

20

10

15

5

Trac

heal

Pre

ssur

es c

mH2

O


HFOVHFOV

Uses an electrically powered piston Uses an electrically powered piston oscillator to alternate positive and oscillator to alternate positive and negative pressures in the airway negative pressures in the airway which assists both inspiration & which assists both inspiration & expirationexpiration


Indications of HFOVIndications of HFOV Failing conventional ventilationFailing conventional ventilation Increasing ventilation requirementIncreasing ventilation requirement Increasing FiO2 requirement : as OI> Increasing FiO2 requirement : as OI>

10 e.g. PDA10 e.g. PDA CXR : diffuse homogeneous lung CXR : diffuse homogeneous lung

diseasedisease PHTN – iNO candidates , OI > 15PHTN – iNO candidates , OI > 15


HFOVHFOVAdvantages :Advantages :1)1)MAP is MAP is maintained at maintained at low peak low peak pressurespressures2)2)Prevents Prevents release of release of inflammatory inflammatory chemical chemical mediatorsmediators


Initial settings of HFOVInitial settings of HFOV Frequency – 6 -10 HzFrequency – 6 -10 Hz IT – 33 % IT – 33 % I:E = 1:2I:E = 1:2 Power ( amplitude ) = 2.5 to 20Power ( amplitude ) = 2.5 to 20 Check – ABG , chest vibrationsCheck – ABG , chest vibrations


Contd . . .Contd . . . Recruitment : MAP – 40cmH2O -40sRecruitment : MAP – 40cmH2O -40s MAP – 5 cmH2O above that in CV , MAP – 5 cmH2O above that in CV ,

maximum upto 45-55 cmH2Omaximum upto 45-55 cmH2O FiO2 – 1 then taperedFiO2 – 1 then tapered If SpO2 not raised , MAP is increased If SpO2 not raised , MAP is increased

by 2-3 cmH2O over 30-60-minby 2-3 cmH2O over 30-60-min


Weaning of HFOVWeaning of HFOV Decrease FiO2 before reducing MAPDecrease FiO2 before reducing MAP FiO2 < 40 % - SpO2 of 90 %FiO2 < 40 % - SpO2 of 90 % then reduce MAP – 1-2 cmH2O every 30 then reduce MAP – 1-2 cmH2O every 30

minmin With MAP – 20-24 cmH2O &With MAP – 20-24 cmH2O & FiO2 – 40 % = ConventionalFiO2 – 40 % = Conventional ventilation can be startedventilation can be started


HFJV and HFOVHFJV and HFOV

HFJVHFJV Jet squirt gas into the Jet squirt gas into the

lungs faster than lungs faster than OscillatorsOscillators

Expiration during Expiration during HFJV is passive, HFJV is passive, accomplished by the accomplished by the natural recoil of the natural recoil of the lungs. lungs.

HFOVHFOV Oscillators get the gas Oscillators get the gas

back out faster than back out faster than Jets by actively Jets by actively sucking it out sucking it out

Expiration is active, Expiration is active, driven by the active driven by the active retraction of the retraction of the oscillating diaphragm oscillating diaphragm or pistonor piston


Prone VentilationProne Ventilation

Adv :Adv : Improves oxygenationImproves oxygenation Improves resp mechanicsImproves resp mechanics Homogenises the pleural PG , Homogenises the pleural PG ,

alveolar inflation & vent distributionalveolar inflation & vent distribution Facilitates drainage of secretionsFacilitates drainage of secretions Limits VILILimits VILI


Review of literatureReview of literature Results of treatment of cardiac surg pts Results of treatment of cardiac surg pts

with postop ARDS by prone position with postop ARDS by prone position ventilationventilation

Anesteziol Reanimatol 2000 oct 5 , 42Anesteziol Reanimatol 2000 oct 5 , 42

4 – 12 hrs – less arrythmias , improved 4 – 12 hrs – less arrythmias , improved arterial oxygenation , less arterial oxygenation , less complications due to hypoxia , higher complications due to hypoxia , higher survival ratesurvival rate


HFOV with ProningHFOV with Proning

Improves Improves oxygenationoxygenation

No mortality No mortality benefitbenefit


Literature ReviewLiterature Review HFOV and adjunct therapies : iNO & HFOV and adjunct therapies : iNO &

prone positioningprone positioning Critical care med 2005 , 33,3Critical care med 2005 , 33,3

Successful use of combined HFOV, Successful use of combined HFOV, iNO & prone position in ARDS iNO & prone position in ARDS

Anaesthesiology 2001 ,05,3Anaesthesiology 2001 ,05,3


Study : Critical care 2011, Study : Critical care 2011, 15:R259 , 28 oct 201115:R259 , 28 oct 2011

HFOV with short term outcome in HFOV with short term outcome in neonates & infants undergoing neonates & infants undergoing cardiac surgerycardiac surgery

In this study , author concludes that In this study , author concludes that when commenced on the day of when commenced on the day of surgery HFOV leads to shorter length surgery HFOV leads to shorter length of mech ventilation & ICU stay than of mech ventilation & ICU stay than conventional ventilationconventional ventilation


High Frequency Ventilation in High Frequency Ventilation in PPHTNPPHTN

V/Q matching to improve V/Q matching to improve oxygenationoxygenation

Respiratory alkalosis to reduce PVRRespiratory alkalosis to reduce PVR Improved response to inhaled NOImproved response to inhaled NO ““Rescue” for air leak syndromesRescue” for air leak syndromes


HFV ChallengesHFV Challenges HFV ventilates so effectively that hypocarbia HFV ventilates so effectively that hypocarbia

can easily be induced, especially when PEEP in can easily be induced, especially when PEEP in low.low.

Inadvertent PEEP can develop when HFV rate is Inadvertent PEEP can develop when HFV rate is inappropriately high , can interfere with CO.inappropriately high , can interfere with CO.

Gas trapping can also occur when MAP is too Gas trapping can also occur when MAP is too low and airways become smaller thereby low and airways become smaller thereby increasing resistance.increasing resistance.


Ventilator induced lung injuryVentilator induced lung injury VILI - BarotraumaVILI - Barotrauma VolutraumaVolutrauma Atelectotrauma Atelectotrauma BiotraumaBiotrauma O2 toxicityO2 toxicity


1.1. Starting Starting TOOTOO late late

2.2. Weaning Weaning TOOTOO fast fast

TOO


Is ECMO an answer to this Is ECMO an answer to this ? ?

Can ECMO keep up the Can ECMO keep up the promise ?promise ?


ECMOECMO ECMO is a temporary support of ECMO is a temporary support of

heart & lung function by partial CP heart & lung function by partial CP bypassbypass

Used for pts – reversible Used for pts – reversible cardiopulmonary failure from cardiac, cardiopulmonary failure from cardiac, pulmonary or other diseases pulmonary or other diseases


ECMO DesignECMO Design


TypesTypes

VenoarterialVenoarterial Blood is drained from Blood is drained from

RA via IJV and RA via IJV and returned to aorta via returned to aorta via carotid artery carotid artery

It provides cardiac as It provides cardiac as well as pulmonary well as pulmonary supportsupport

It requires arterial It requires arterial cannulationcannulation

VenovenousVenovenous Blood is drained from Blood is drained from

RA via sideholes of a RA via sideholes of a double lumen catheter double lumen catheter & returned to RA via & returned to RA via the endhole of same the endhole of same catheter catheter

It aids mainly in It aids mainly in recovey of lungsrecovey of lungs

It requires only venous It requires only venous cannulationcannulation


VA ECMOVA ECMO Higher PaOHigher PaO22 is achieved is achieved Bypasses pulmonary Bypasses pulmonary

circulationcirculation

Provides cardiac Provides cardiac support to assist support to assist systemic circulation systemic circulation

VV ECMOVV ECMO Lower PaO2 is Lower PaO2 is

achievedachieved

Maintains PBFMaintains PBF

Does not provide Does not provide cardiac support to cardiac support to assist systemic assist systemic circulation circulation


VA ECMOVA ECMO VV ECMOVV ECMO


ECMO Neck CannulationsECMO Neck Cannulations


ECMO Chest CannulationsECMO Chest Cannulations


Indications contd. . .Indications contd. . . Low CO due to RV , LV ,Bivent failure Low CO due to RV , LV ,Bivent failure

after repair of CHDafter repair of CHD Pulm HTNsive Crisis after repair of CHD Pulm HTNsive Crisis after repair of CHD

leading to severe hypoxemia , low CO or leading to severe hypoxemia , low CO or bothboth

As a bridge to cardiac surgery in serious As a bridge to cardiac surgery in serious pts with CHDpts with CHD

As a bridge to cardiac transplantAs a bridge to cardiac transplant PPHTNPPHTN


Contd. . . Contd. . . Cardiac arrestCardiac arrest Resp causes : cong diaphragmatic Resp causes : cong diaphragmatic herniahernia : meconium aspiration : meconium aspiration syndromesyndrome : resp distress : resp distress syndromesyndrome


Management of ECMOManagement of ECMO Anticoagulation – ACT : 180 to 240 sAnticoagulation – ACT : 180 to 240 s aPTT : 60 to 90 saPTT : 60 to 90 s Heparin infusion – 15 to 60 u/kg/hrHeparin infusion – 15 to 60 u/kg/hr All blood inv including LFTs , KFTsAll blood inv including LFTs , KFTs Ventilator – Fio2 – 30 %Ventilator – Fio2 – 30 % Freq – 10/mFreq – 10/m PEEP -10cm H2OPEEP -10cm H2O IP – 20 cm H2OIP – 20 cm H2O


Literature ReviewLiterature Review VA ECMO in severe RV failure with VA ECMO in severe RV failure with

pulmonary obstructive hemodynamic pulmonary obstructive hemodynamic pattern pattern

J Invasive cardiol Aug 2011 ,J Invasive cardiol Aug 2011 , 22,365 - 36922,365 - 369


Timing of initiation of ECMO is very Timing of initiation of ECMO is very crucial in determining the patient crucial in determining the patient outcomeoutcome


In doubt let the kid make his In doubt let the kid make his own vent changesown vent changes

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Postoperative Ventilation in Paediatric Cardiac Surgical Patients

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