Balancing the Heart & Lungs in Cardiac Shunt Lesions

Beyra RossouwIntensive Care Unit

Red Cross War Memorial Children’s Hospital Red Cross War Memorial Children’s Hospital University of Cape Town

Scope of talk

• Cardiac symptoms of cardiac shunts

• Pathophysiology of lung disease

• Treatment principles

LA & LV ENLARGEMENT

VSD Flow across VSD depends on:

•VSD size

•Pulmonary pressures

RIGHT ATRIUM

LEFT ATRIUM

ENLARGEMENT

↑Pulmonary vascular

resistanceSmall: PSMMedium: PSM & MDMLarge: ESM & MDM & loud P2

RIGHT VENTRICLE

LEFT VENTRICLE

Adapted from pediatric cardiology 5th edition, M Park

LA & LV ENLARGEMENT

LATE VSD

RV HYPERTROPHY

RIGHT ATRIUM

LEFT

ATRIUM

RIGHT

VENTRICLE

LEFT

VENTRICLE

↑↑↑↑ ↑↑↑↑ PULMONARY VASCULAR

RESISTANCE

HYPERTROPHY

CYANOSIS

Eisenmenger

RV heave

Very loud P2

Murmurs softer

VENTRICLE VENTRICLE

Adapted from pediatric cardiology 5th edition M Park

VSD pathophysiology

Reduced stroke volume to systemic circulation

Exposed to systemicpressures

Systemic circulationPulmonary circulation

Exposed to excess flow

Neuro -humeral compensation Q= SV X HR

Volume loading of left heart

Myocardial contractility failure

Pulmonary hypertension

ASD

RV

RA ENLARGEMENT

RV ENLARGEMENT

Fixed split S2PS murmurTS murmur

Adapted from pediatric cardiology 5th edition, M Park

LA & LV ENLARGEMENT

AVSD Flow across VSD depends on:

•AVSD size

•Pulmonary pressures

RIGHT ATRIUM

LEFT ATRIUM

RA & RV

ENLARGEMENT ENLARGEMENT

↑Pulmonary vascular

resistance

RIGHT VENTRICLE

LEFT VENTRICLE

ESM & MDM & loud P2

ENLARGEMENT

Adapted from pediatric cardiology 5th edition, M Park

PDA

LV

LA ENLARGEMENT

Flow across PDA depends on:

•PDA size

•Pulmonary pressures

RA LA

RV LVLV ENLARGEMENT

Continuous murmur

Lungs

↑Pulmonary vascular

resistance

RV LV

Adapted from pediatric cardiology 5th edition, M Park

“Cardiac failure”a misnomer in shunt lesions

Myocardial contraction function preserved till end stage BUT ………

A large % of stoke volume is pumped away

through shunt to RV

instead of aorta

Cardiac failure symptoms

• Neuro- endocrine compensation for low cardiac output– ↑Sympathetic discharge

• Tachycardia • Vasoconstriction • Sweaty• Sweaty

– ↑ Renin-angiotensin: • Na & H2O retention • Vasoconstriction

• Chamber dilatation• Flooding the lungs

– Increase flow

Respiratory effect of cardiac shunts

• Pulmonary edema

• ↑ Airway resistance

• V/Q mismatching• V/Q mismatching

• Atelectasis

• Pulmonary hypertension↑Work of breathing

Pulmonary edema↑ Hydrostatic pressure & ↓lymphatic clearance

• ↑Pulmonary arterial flow – Left to right shunts

• Pulmonary capillary leak– LRTI, sepsis, shock– LRTI, sepsis, shock

• Pulmonary vein congestion – ↑ Left heart pressure

• L heart obstructions

• LV failure

Alveolar capillaries

Consequence of pulmonary edema↑Work of breathing

• Interstitial edema– ↓ Lung compliance

– Compress small airways

Alveolar edema

Bronchus

Vessels

• Alveolar edema– Hypoxia

– Atelectasis

– ↓Lung compliance

Effect of edema on airway resistance

Normal infant

Normal adult

1 mm Edema

4 mm

8 mm

Resistance: ↑16xCross sectional area:↓ 75%

Resistance: ↑3xCross sectional area:↓ 44%adult

Resistance = 1radius 4

Cross sectional area:↓ 44%

Atelectasis• Pulmonary edema

– Destroy surfactant

• External airway compression– Dilated PA’s, LA, PDA– Bronchomalacia– Bronchomalacia

• Recurrent LRTI– Secretions

• Hepatomegaly & ascitis– Splint diaphragm

O2

Venous Arterial

Sats

Sats 80%Sats 70%Sats 100%

V/Q mismatch

Sats70%

Pulmonary hypertension

• ↑ Pulmonary flow & pressure

• Hypoxic vasoconstriction

• Recurrent LRTI → ↑inflammation in pulmonary vesselspulmonary vessels

S. Haworth Progress in Pediatric Cardiology 12(2001)

Pulmonary hypertension

IVS flattening in Pulmonary hypertension

D- shape LV Crescent shape LV

Normal

LVRV

D- shape LV Crescent shape LV

•LV D- shape in diastole = volume loaded RV•LV D- shape in systole & diastole = pressure loaded RV

LV LVRV RV

Aspiration / GORD

• Feeding difficulty

• Aerophogia

• Esophagus compression

• Syndromes, VACTREL• Syndromes, VACTREL

Poor growth & muscle mass

• ↓ Caloric intake

• ↑Caloric demand– ↑Work of breathing

Maintain cardiac output– Maintain cardiac output

• ↑Muscle fatigue

• ↓ Secretion clearing

• Poor cough →hypoxic

Treatment

Goal: Optimize O2 Delivery to tissues

↓↓↓↓O2 Demand↑O2 Delivery

Oxygen Delivery to Tissues

Ventilation

Gas exchange

O2 Delivery

Alveoli

O2 Delivery

O2 extraction

ATPCell

LVRV

Treating the lungs

• Lasix for the lungs– Improve lung compliance– Watch elects

• Exclude / prevent aspirationExclude / prevent aspiration

• CPAP/ PEEP – Recruit atelectasis– ↓Alveolar edema– ↓Oxygen demand– ↓LV afterload

Aims of ventilation• Adjust goals

– Sats in low 90’s

– Use Ph & PaCo2 to manipulate PVR

• Do not damage lungs– Maintain normal lung volumes– Maintain normal lung volumes

– Tidal volumes 6-8ml/kg, PEEP to recruit

• Pulmonary hypertensive – Comfortable, avoid hypoxia & stress

– Keep Mg+ high

Ventilate to manipulate pulmonary blood flow

Overinflated lungs & capillary compression

Pulmonary vascular resistance vs lung volumes

Hypoxic vasoconstriction

West , Pulmonary pathophysiology: the essentials. 6th edition

Oxygen damage: FiO2 > 0.6

• O2 toxicity →free radicals – Cell injury & DNA damage

• Worsen V/Q mismatch– ↓Hypoxic pulmonary vasoconstriction– ↓Hypoxic pulmonary vasoconstriction

• Pulmonary vasodilator

↓PVR:→ ↑L to R shunt

– ↑flooding lungs

– steel blood from systemic circulation

• Nitrogen wash out→ atelectasis

Treating the heartOptimize O2 Delivery to tissues

• Hb: > 10-12g/dl

• ↑Stroke volume – Afterload reduction

• Myocardial contraction• Myocardial contraction– Optimize K+, Ca 2+, Mg+ & Glucose

– Low dose inotropes if ↑ lactate

• Do not ↑ myocardial O2 demand– Limit tachycardia,

– Keep comfortable

↑ Contraction will ↑ L to R shunt

NORADRENALINE

ADRENALINE

αADRENALINE

β1 & β2

Inotropes ↑Stroke volume, ↑ HRVasoconstriction

ADRENALINE

DOPAMINE

DOBUTAMINE

NORADRENALINE

DOPAMINE

Pediatric Cardiac Intensive Care . Chang & Wernovsky

Optimize nutrition

• Optimize caloric intake, vitamins & trace elements

• Do not restrict volume of fluids unless ventilatedventilated

• NGT fed if very tachypnea

• NJ fed if GORD suspected

• Educate parents

General treatment

• Immunizations

• Dental care & education

• Surgery for large shunts– VSD ideal before 18 months– VSD ideal before 18 months

– AVSD ideal before 6 months

– Primum ASD at 2-4jr

Take home message• In high pulmonary flow

– Diurese the flooded lungs– Maintain normal lung volumes– Limit lung damage

• In low cardiac output state• In low cardiac output state– Decrease cardiac work

• ↓ respiratory effort• ↓ afterload

• Attention to nutrition• Infection prevention

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