Perfusion in pediatric patients - PowerPoint Presentation

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Perfusion in pediatric patients

Dr

Sabir

Ali Khan

Clinical

Perfusionist

J.N.Medical

College, AMU, Aligarh

PGDPT,

BSc

,

MSc,PhD

.

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THE INDIAN

SCENARio

Cardiac diseases are the most common cause of death in the world

Cardiac surgery is one of the most important methods of managing treatable heart ailments.

Ill distribution of cardiac centres in India

Very few centres in North India

UP has 15

crore

population, needs 150 centres…very few centres doing pediatric cardiac surgery

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THE INDIAN SCENARIO

India's is a young population

Highest birth rate in the world

The heart most commonly afflicted organ with defects

1,50,000-2,00,000---children with CHD born /year

Only less than 5 % undergoing surgery

huge dearth of pediatric cardiac centers

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Prevalance

of CHD in India

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CPB use for cardiac surgery

CPB has been used since 1953

there is a significant morbidity and mortality associated with CPB.

Past four decades- phenomenal growth in the field of congenital heart surgery.

FROM palliative procedures TO CORRECTIVE surgeries

Today ---neonatal and infant surgery is being done in many metro cities and some tier two cities .

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Kids are not miniature adults

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They have different

Immature Immune system

Renal

sysyem

Endocrine

sytem

Hyperactive pulmonary circuit

Sensitive myocardium

Growing CNS

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Pediatric is not a mini adult

Priming volume of smallest pediatric circuit exceeds the total blood volume of the baby

The blood of the child is exposed to 4 times more foreign surface related to adult.

New born is a fast developing organism with immature organs.

CPB represents an extreme stress to these developing organs.

Children are more prone to inflammatory response.

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PHYSIOLOGICAL EFFECTS OF CPB ON VARIOUS ORGANS

Renal function:

There is temporary renal dysfunction in neonates after CPB

Surgical stress results in decreased blood flow & GFR

This may be due to elevation of stress hormones

CPB elevates the renin angiotensin system increasing aldosterone production & fluid retention

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PHYSIOLOGICAL EFFECTS OF CPB ON VARIOUS ORGANS contd..,

Pulmonary function

Many children have abnormal respiratory mechanics before surgery

The inflammatory cells residing in lung parenchyma mediates injury seen after CPB

Hypothermia causes leukocyte degrannulation & compliment activation leading to endothelial injury.

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physiological consideration - Thermoregulation

High ratio of surface area to body mass

Prone for hypothermia

Heat generation & maintenance

Metabolic processes

Brown fat(

scapula,surrounding

deep structures)

Non-shivering thermo genesis stimulating mitochondrial respiration

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0

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OXYGENATORS

Hollow fiber oxygenators are widely used

Heparin coated & Albumin coated oxygenators are also available

Oxygenators has integrated heat exchangers and handles air effectively

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TUBINGS

Aim: to minimize prime & allow adequate flow rate

Higher line pressures induces

hemolysis

VAVD allows use of smaller tubing for venous line

Coated circuits lowers platelet loss, lactate levels & better postoperative lung function

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Prime

Prime volume is much more than total blood volume of patient

Blood prime –

Acyanotic

Bloodless – Cyanotic (prime

is advocated but practically

difficult)

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Canulae

Selection of correct sizes to prevent pressure gradients and

hemolysis

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Management of anticoagulation

> Heparin 3 IU/ML add to prime circuit

> Heparin loading dose 300 – 400 IU/kg body weight from

Anesthisia

side

>Maintain ACT > 480sec

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Initiation & management of CPB

Begin arterial flow first (prevents

exanguination

)

Open venous lines

Observe for ventricular distension

If heart distends, it should be vented

VAVD reduces priming volume

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Oxygenation strategies in Cyanotic Kids

Injury mediated by oxygen free radicals occurs when exposed to sudden oxygenation.

Causing myocardial depression & pulmonary dysfunction

Initiating CPB at room air recommended

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COOLING TECHNIQUE

During cooling the temp. gradient between the

perfusate

and the nasopharyngeal/rectal temp. should not exceed

6-8

degrees.

Perfusate

temp. should not fall below the target cooling temp.

The rate of cooling should be around 0.6-0.8 degrees/min

Simultaneously

the water blanket temp. should be set at the target temp.

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Importance of HYPOTHERMIA

Allows decrease in pump flow rate

Facilitates surgical exposure

Decreases rate of myocardial

rewarming

Decreases the amt of blood returning to the heart in patients with significant

aorto

-pulmonary collaterals

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Adequacy of perfusion

Flow

BP

ABGLactates

Mixed venous Saturation

Hematocrit

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Historically

1960’s- blood

colour

1990’s- SvO2, ABG

2000’s- lactate, NIRS, oxygenator effluent gas monitoring.

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Arterial Flow Rates

Body Weight-150-200ml/kg

BSA-2.0-3.2Lt/m

2

ABG

Mix Venous Saturation.

PCO

2

Lactate Levels.

Temperature

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Arterial Pressures

The arterial pressures are a very important determinant of adequacy of perfusion during cardiopulmonary bypass.

The

optimal perfusion

pressures in pediatric patients is 40-50 mmHg.

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ABG

PO2 – 120-150mm Hg

PCo2 – 35-40mm Hg

Blood sugar – normal range

Electrolytes

Bicarbonate

Lactates

Hematocrit

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Hematocrit

Maintaining

Hematocrit

around 30% provide adequate oxygen supply in infant.

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Lactate

Serum

Lactate a good marker of adequacy of

perfusion.

Tissue

hypoperfusion

with lactic acidosis during CPB may occur despite normal blood gas concentrations.

Extreme

hemodilution

, hypothermia, low-flow CPB, and excessive

neurohormonal

activation have also been linked to lactic acidosis during CPB

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Lactate Management

Dilate the patient.

Increase flow.

Add blood

Do CUF.

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MIXED VENOUS OXYGEN LEVELS

SvO2 should be 65-75

%

If low SvO2 is present then:

1. BFR should be increased

2. Blood should be added if

Hct

is low

3. Depth of anesthesia should be increased

If the SvO2 is too high then one should rule out peripheral

hypoperfusion with consequent A-V shunting

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Cardioplegia Delivery

The temperature of

cardioplegia

is controlled with the integrated heater/cooler unit-it is set at 4

ºC for cold

cardioplegia

delivery;the

heater portion is set at 39ºC for warm induction/reperfusion techniques

Cold induction

cardioplegia

is delivered at a pressure less than 150 mmHg (ideally around 100 mmHg) over a 2-4 min. period

The total dose is 20-30ml/kg

The target myocardial temp. is 10-15

ºC if it is being monitored

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Special issues - PAH management

Patients of congenital heart disease with pulmonary artery hypertension constitute a difficult substrate .

Because the immature lung is more vulnerable to CPB,

postbypass

lung injury is usually more common and serious in infants with congenital heart disease, especially those with pulmonary hypertension (PH).

During total CPB the lungs are

perfused

by bronchial artery alone, putting the lungs at risk for an ischemic insult and reperfusion injury when normal

antegrade

flow is reestablished through the pulmonary artery.

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Special issues - PAH management

Moreover , CPB induces systemic inflammatory response syndrome (SIRS) leading to post operative pulmonary dysfunction.

Several studies have demonstrated the role of

antegrade

pulmonary perfusion in alleviating the ischemia-reperfusion injury and inflammatory response.

--

Takaaki

Suzuki et al, J

Thorac

Cardiovasc

Surg

2001;122:242-248.

--

Serraf

et

aL

, J

Thorac

Cardiovasc

Surg

1997;114, Number 6:1061-69

.

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MGT of PAH contd..

After going on bypass,

antegrade

pulmonary perfusion is given for 10 minutes before cross clamping and stopped momentarily at the time of cross clamping and

cardiolplegia

delievery

.

It is again restarted at 10-20ml/Kg/minute and continued till removal of cross clamp, after which it was continued till the patient is fully

rewarmed

.

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Modification of CPB circuit for antegrade

perfusion

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Pre - operative Pulmonary Artery Pressure

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Modification of CPB circuit for antegrade

perfusion

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Post - operative Pulmonary Artery Pressure

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Rewarming

06-08 deg temperature gradient

Possibility of gas emboli if gradient is exceeded

Temperature monitored at different sites

–tympanic, nasopharyngeal or

oesophageal

(cerebral temperature)

- rectal or bladder(core temperature

)

The gradient between nasal & rectal not > 2deg c

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Weaning off CPB

Before weaning

Ensure satisfactory HR & rhythm

Rewarm fully

Lungs are ventilated adequately

Optimise electrolytes & acid-base status

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POST CPB EDEMA

Can lead to neurological injury due to cerebral edema

Can lead to impaired myocardial function due to myocardial edema

Pulmonary dysfunction arises due to increased interstitial water leading to impaired gas exchange

Renal dysfunction can also result due to interstitial edema

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STRATEGIES for POST-CPB EDEMA

Prime

hemofiltration

(maintain

Hct

, remove inflammatory mediators, excess potassium)

Avoid over-

hemodilution

during CPB and ensure

Hct around 30%

at completion of rewarming Ultrafiltration and modified ultrafiltration

Mannitol

and diuretics like

furosemide

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ULTRAFILTRATION

Neonates & infants often develop excessive fluid accumulation due to CPB

Oedema develops in vital organs like brain, heart, intestine & lungs

MUF performed after completion of CPB

MUF filters the patient’s extra cellular volume as well as residual circuit volume

MUF improves pulmonary compliance & LV function

More than 20ml/kg/min during MUF can cause transient reduction in cerebral perfusion”stealing”

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Diagnosis

No of Cases

Outcome (%)

ASD

10

100

ASD with PAPVC

1

100

CMV

3

100

VSD with Severe PAH

11

88

VSD with Aortic Valve Repair

4

100

MVR

1

100

MVR with TV Repair

1

100

DVR

1

100

TOF

23

94

DORV VSD PS

2

100

BD Glenn

4

100

Total cases

done -61

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Age distribution

Age group

No of cases

0-6 months

3

6-12 months

4

1-5 years

23

> 5 years

31

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Total cases -61

Weight distribution

No of cases

<5

kg

4

5-10 kg

18

10-15 kg

9

> 15 kg

30

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CONCLUSION

Adequacy

of perfusion in infant is research driven & evidence based

.

While

certainly conduct of CPB has become safer over the years but still there is room for improvement

Attention

to detail and constant vigilance and communication between the

perfusionist

, anesthesiologist and surgeon is essential to the safe conduct of CPB

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THANKS FOR YOUR PATIENCE

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