LOW CARDIAC OUTPUT

SYNDROM IN CHILDREN AFTER

CARDIAC SURGERYHala EL-Mohamady, professor of anaesthesia,

Ain Shams University

Low cardiac output syndrome

(LCOS) is a clinical

syndrome seen commonly (25%) after pediatric

cardiac surgery

but also occurring secondary tobut also occurring secondary toacute myocarditis and septic shockacute myocarditis and septic shock..

Regardless of aetiology, the resulting effectsRegardless of aetiology, the resulting effects

areare

shock and inadequate organ perfusionshock and inadequate organ perfusion

organ dysfunctionorgan dysfunction

Coincide With Coincide With Postoperative Postoperative decrease in cardiac index and decrease in cardiac index and

increases in SVR and PVRincreases in SVR and PVR

reducing cardiac outputreducing cardiac output

This occurs typicallyThis occurs typically 66––1818 h after h after

cardiopulmonarycardiopulmonarybypass, which is bypass, which is usually in the usually in the

middle of the nightmiddle of the night!!

Causes

of postoperative

LCOS

--Inflammatory cascade triggered by (CPB)Inflammatory cascade triggered by (CPB)

--Aortic cross-clampAortic cross-clamp

--HypothermiaHypothermia

--Reperfusion injuryReperfusion injury

--Pericardial tamponadePericardial tamponade

--Residual cardiac lesions, even when minorResidual cardiac lesions, even when minor

PREVENTIONPREVENTION

Because LCOS is common and Because LCOS is common and contributes to postoperative contributes to postoperative morbidity and mortality, morbidity and mortality, preventionprevention of this predictable of this predictable hemodynamic deterioration may hemodynamic deterioration may have significant implications for have significant implications for clinical outcomeclinical outcome

DiagnosisOF

LCOP SYNDROM

AnticipationAnticipation

is the key to the diagnosis andis the key to the diagnosis and

management of LCOSmanagement of LCOS

SoSoDiagnosis relies on anticipation, clinical Diagnosis relies on anticipation, clinical

features and investigationfeatures and investigation

CLINICAL FeaturesCLINICAL FeaturesOFOF

LOW COP SYNDROMLOW COP SYNDROM

- -tachycardiatachycardia - -oliguria (0.5 ml/kg/h)oliguria (0.5 ml/kg/h)

- -poor peripheral poor peripheral perfusionperfusion

- -low blood pressurelow blood pressure

The ability of clinicians

to assess cardiac output

from clinicalexamination alone is

poor

INVESTIGATIONS

- -Metabolic acidosisMetabolic acidosis

- -LactateLactate

- -Mixed venous Mixed venous oxygen saturationoxygen saturation

- -EchocardiographyEchocardiography

ManagementManagement

aimed at achieving the optimal balance aimed at achieving the optimal balance betweenbetween

oxygen delivery and oxygen consumptionoxygen delivery and oxygen consumption

A check list of immediately A check list of immediately treatable causes is useful, treatable causes is useful,

as is a flow diagram to lead as is a flow diagram to lead staff through a logical staff through a logical

approachapproach . .

Check list of causes

of postoperative

LCOS

--Adequate airway (tube position, size Adequate airway (tube position, size and patency) and ventilation and patency) and ventilation (atelectasis, pneumothorax)(atelectasis, pneumothorax)

--Pericardial tamponadePericardial tamponade

--Pulmonary hypertensive crisisPulmonary hypertensive crisis

--Arrhythmias (loss of AV synchrony, Arrhythmias (loss of AV synchrony, tachycardia or bradycardia)tachycardia or bradycardia)

--Significant residual lesionSignificant residual lesion

--Electrolyte abnormality (e.g. Electrolyte abnormality (e.g. hypocalcaemia)hypocalcaemia)

PreloadPreloadPreload is traditionally assessed byPreload is traditionally assessed by::

measuring measuring filling pressuresfilling pressures from right and left from right and left atrial linesatrial lines..

In addition, In addition, venous capacitancevenous capacitance also affects also affects venous return. Venodilatation often occurs on venous return. Venodilatation often occurs on rewarming and may be exacerbated by drugsrewarming and may be exacerbated by drugs

Finally, Finally, positive pressure ventilationpositive pressure ventilation (PPV) will tend (PPV) will tend to reduce RV preload by inhibiting venousto reduce RV preload by inhibiting venous

returnreturn . .

Left ventricular Left ventricular afterloadafterload

Reduction in LV afterload will Reduction in LV afterload will improve cardiac output, improve cardiac output, as as long aslong as an adequate diastolic an adequate diastolic pressure is maintained for pressure is maintained for coronary perfusioncoronary perfusion..

Left ventricular afterload

Short ActingVasodilators

NiprideGTN

Long ActingVasodilatorsPhenoxybenzaminCaptopril

PPV

Right ventricular afterload Right ventricular afterload pulmonary hypertension pulmonary hypertension

Right ventricular Failure

poor COP

Pulmonary hypertension

Preventive treatment strategies

ForPULMONARY

HYPERTENSION

--optimal sedationoptimal sedation

--neuromuscular blockadeneuromuscular blockade

--induced respiratory or metabolic induced respiratory or metabolic alkalosis alkalosis

--hyper-oxygenationhyper-oxygenation

--Avoiding or ablating stimuliAvoiding or ablating stimuli

) ) trigger pulmonary hypertensive crises(e.g. administering fentanyl trigger pulmonary hypertensive crises(e.g. administering fentanyl bolus prior to airway suction)bolus prior to airway suction)..

--Nitric oxideNitric oxide

Nitric OxideNitric Oxidea potent endogenous vasodilator that a potent endogenous vasodilator that produces vascular relaxation via produces vascular relaxation via increases in the intracellular increases in the intracellular concentration of guanosine 3,5-cyclic concentration of guanosine 3,5-cyclic monophosphatemonophosphate..

It is a specific pulmonary vasodilator It is a specific pulmonary vasodilator when delivered by inhalation (iNO)when delivered by inhalation (iNO) , ,

RV afterload is reduced, thereby RV afterload is reduced, thereby improving RV ejection fraction and improving RV ejection fraction and cardiac outputcardiac output..

Nitric Oxide

?Rebound

pulmonaryhypertension

Pharmacological treatment of systolic

anddiastolic dysfunction

It should be remembered that all of It should be remembered that all of these potent agents will increase these potent agents will increase myocardial oxygen demand, and myocardial oxygen demand, and that they should be titrated to the that they should be titrated to the minimal dose that achieves the minimal dose that achieves the desired effect. They should not desired effect. They should not be commenced or increased prior be commenced or increased prior to consideration of preload and to consideration of preload and afterloadafterload..

Terms used for cardiovascula

r drugs

TermTerm MeaningMeaning

Inotropy Inotropy Increased force of myocardial Increased force of myocardial

contraction not related to contraction not related to preload or afterload preload or afterload

Chronotropy Chronotropy Increased rate Increased rate

DromotopyDromotopy Increased speed of electrical Increased speed of electrical

conductionconduction

Lusitropy Lusitropy Increased effectiveness of Increased effectiveness of active diastolic relaxation active diastolic relaxation

AgentAgentDose Dose rangerange (mcg/kg/mi(mcg/kg/min)n)

StimulateStimulateMain effectsMain effects

DobutamineDobutamine11––1515b14b2b14b2Inotropy, Inotropy, chronotropy, chronotropy, dromotopy,VDdromotopy,VD

DopamineDopamine11––55( ( lowlow ) )

55––1515 ((highhigh ) )

B14a1B14a1

a14b1a14b1

Inotropy, Inotropy, chronotropy, chronotropy, dromotopydromotopy

Vasoconstriction Vasoconstriction inotropy, inotropy, chronotropychronotropy

NoradrenalinNoradrenalinee

0.10.1––0.50.5a1bb1a1bb1Vasoconstriction Vasoconstriction with some inotropywith some inotropy

AgentAgentDose rangeDose range (mcg/kg/min)(mcg/kg/min)

StimulatesStimulatesMain effectsMain effects

AdrenalineAdrenaline0.050.05––o.1(low)o.1(low)

0.10.1––11( ( highhigh))

a1 ¼ b1 ¼ a1 ¼ b1 ¼ b2b2

a14b14b2a14b14b2

Inotropy, Inotropy, chronotropy, chronotropy, dromotopydromotopy,,

bronchodilationbronchodilation, multiple , multiple endocrineendocrine

effects effects (increased (increased glucose, glucose, lactate)lactate)

As above plus As above plus potent potent vasoconstrictiovasoconstrictio

AgentAgentDose rangeDose range (mcg/kg/min(mcg/kg/min

StimulatesStimulatesMain Main effectseffects

MilrinoneMilrinone7575 mcg/kg mcg/kg loadload,,

0.250.25––11

InhibitsInhibits

phosphodiestphosphodiesterase IIIerase III

Inotropy, Inotropy, lusitropy and lusitropy and vasodilationvasodilation

VasopressinVasopressin0.020.02 U/min U/min (not kg)(not kg)

V1, V2V1, V2Potent Potent vasoconstrictivasoconstrictionon

LevosimendaLevosimendann

2525 mcg/kg mcg/kg load, 0.2load, 0.2

for 24 hfor 24 h

Ca2+ Ca2+ sensitivity of sensitivity of troponin Ctroponin C

Inotropy, Inotropy, lusitropy and lusitropy and vasodilationvasodilation

Thyroid hormoneThyroid hormoneThyroid hormone has an essential role in cellular Thyroid hormone has an essential role in cellular metabolism and in maintaining haemodynamic metabolism and in maintaining haemodynamic stabilitystability..

It is required for the synthesis of contractileIt is required for the synthesis of contractileproteins and to maintain normal myocardial proteins and to maintain normal myocardial contractioncontraction..

Suppression of thyroid hormone levels has beenSuppression of thyroid hormone levels has beendemonstrated in children following CPB, maximal demonstrated in children following CPB, maximal between 12 and 48 h and lasting up to 7 days between 12 and 48 h and lasting up to 7 days after CPBafter CPB..

Lack of evidence to Lack of evidence to demonstrate benefitdemonstrate benefit..

NesiritideNesiritideB-type natriuretic peptide is B-type natriuretic peptide is synthesized and excreted from the synthesized and excreted from the ventricular myocardium in response ventricular myocardium in response to myocardial stretchto myocardial stretch..

It results in natriuresis, diuresis and It results in natriuresis, diuresis and vascular smooth muscle relaxation. vascular smooth muscle relaxation. Clinically it is said to augment Clinically it is said to augment preload and reduce afterloadpreload and reduce afterload..

Non-pharmacological

treatment of

Systolic and diastolic

dysfunction

Delayed sternal closureDelayed sternal closure

The aim is to allow the heart to recover, and The aim is to allow the heart to recover, and become less oedematous without the become less oedematous without the added problem of ‘‘dry’’ tamponadeadded problem of ‘‘dry’’ tamponade..

Delayed closure is associated with an increased risk of Delayed closure is associated with an increased risk of mediastinitis (particularly with gram negative mediastinitis (particularly with gram negative organisms), and thyroid suppression from iodine organisms), and thyroid suppression from iodine absorption from iodine-based antiseptics. When the absorption from iodine-based antiseptics. When the sternum is closed, significant haemodynamic and sternum is closed, significant haemodynamic and respiratory changes can occur and should be respiratory changes can occur and should be anticipatedanticipated..

Induced hypothermiaInduced hypothermiaReducing the body temperature results in a Reducing the body temperature results in a reduction in metabolic rate, oxygen demand and reduction in metabolic rate, oxygen demand and heart rate, and may have a direct beneficial heart rate, and may have a direct beneficial effect on cardiac function. SVR is increased and effect on cardiac function. SVR is increased and stroke volume and MAP are maintainedstroke volume and MAP are maintained..

Although hypothermia is a useful rescue strategy, it is not Although hypothermia is a useful rescue strategy, it is not without risks, including sepsis, coagulation disorders without risks, including sepsis, coagulation disorders and altered pharmacokinetics. Neuromuscular paralysis and altered pharmacokinetics. Neuromuscular paralysis is usually required to prevent shivering which, if is usually required to prevent shivering which, if unopposed, will increase oxygen consumption and unopposed, will increase oxygen consumption and lactate productionlactate production

Mechanical supportMechanical support

The major benefit of mechanical circulatory The major benefit of mechanical circulatory support in the treatment of LCOS is allowing support in the treatment of LCOS is allowing time for myocardial recovery whilst preventing time for myocardial recovery whilst preventing ongoing damage to other organ systemsongoing damage to other organ systems

Veno-arterial (VA) ECMO, and LV and/or RV Veno-arterial (VA) ECMO, and LV and/or RV assist devicesassist devices are the two commonest methods of are the two commonest methods of mechanical support. Selection and assessment of mechanical support. Selection and assessment of candidates for ECLS is extremely important. Bleeding is candidates for ECLS is extremely important. Bleeding is the most common complication, particularly from the the most common complication, particularly from the wound, but intracranial haemorrhage can occur usually wound, but intracranial haemorrhage can occur usually resulting in withdrawal of therapyresulting in withdrawal of therapy..

Pacing and arrhythmia managementPacing and arrhythmia management

Arrhythmias that result in loss of AV synchrony, orArrhythmias that result in loss of AV synchrony, orsignificantly affect heart rate, are commonsignificantly affect heart rate, are common

))425%425% ( (and poorly tolerated in the setting ofand poorly tolerated in the setting ofLCOS. Tachycardia can allow inadequate time forLCOS. Tachycardia can allow inadequate time forventricular filling, especially with a poorly compliantventricular filling, especially with a poorly compliantventricle; bradycardia is also poorly toleratedventricle; bradycardia is also poorly tolerated..

AV synchrony is particularly important in LCOS as the AV synchrony is particularly important in LCOS as the effects of atrial systole (atrial kick) on ventricular effects of atrial systole (atrial kick) on ventricular preload can be significant, and contributing up to 20% preload can be significant, and contributing up to 20% of stroke volume. AV synchrony is particularly of stroke volume. AV synchrony is particularly important in LCOS as the effects of atrial systole (atrial important in LCOS as the effects of atrial systole (atrial kick) on ventricular preload can be significant, and kick) on ventricular preload can be significant, and contributing up to 20% of stroke volumecontributing up to 20% of stroke volume..

Minimizing

the consequences

of LCOS

Classically, a prolonged period of LCOS Classically, a prolonged period of LCOS can lead to acan lead to a

--ventilator-dependantventilator-dependant

--oedematous oedematous childchild--malnourishedmalnourished

--significant sedation problemssignificant sedation problems--vascular access difficultiesvascular access difficulties . .

Much can be done to minimize the Much can be done to minimize the effects of LCOS while awaiting effects of LCOS while awaiting intrinsic myocardial recoveryintrinsic myocardial recovery..

Renal failureRenal failureRenal failure and fluid retention are common due Renal failure and fluid retention are common due to poor renal perfusion and low mean blood to poor renal perfusion and low mean blood

pressurepressure . .

Diuretics are usually necessary after the first 24 Diuretics are usually necessary after the first 24 hh . .

Early peritoneal dialysis (PD) started prior to Early peritoneal dialysis (PD) started prior to significant oedema formation, can prevent significant oedema formation, can prevent excessive fluid bolus administration, ionotrope excessive fluid bolus administration, ionotrope escalation and frusemide toxicityescalation and frusemide toxicity..

Respiratory failureRespiratory failureRespiratory failure following LCOS is Respiratory failure following LCOS is usually multifactorial, resulting from usually multifactorial, resulting from fluid overload, malnutrition, muscle fluid overload, malnutrition, muscle weakness, critical illness weakness, critical illness polyneuropathy, atelectasis, upper polyneuropathy, atelectasis, upper airway oedema and intrinsic lung airway oedema and intrinsic lung disease, with significant reduction in disease, with significant reduction in FRC secondary to sternotomy. FRC secondary to sternotomy. Appropriate ventilation Appropriate ventilation strategies that optimize PEEP, strategies that optimize PEEP, minimize tidal volume (6-8 minimize tidal volume (6-8 ml/kg) and avoid paralysis are ml/kg) and avoid paralysis are optimaloptimal..

Nutrition, SedationNutrition, SedationOptimal nutrition is often difficult due to fluidOptimal nutrition is often difficult due to fluid

restriction and gut failurerestriction and gut failure..

Early Early enteral nutritionenteral nutrition and the early use of and the early use of jejunal feeding strategies are importantjejunal feeding strategies are important . .

TPNTPN is sometimes required but can often be is sometimes required but can often be avoided by jejunal feeding. It is often worth avoided by jejunal feeding. It is often worth starting starting PDPD to make space for increased caloric to make space for increased caloric intakeintake..

Optimal sedationOptimal sedation and uncomplicated venousand uncomplicated venous

access are always strived for but rarely achievedaccess are always strived for but rarely achieved..

Flow diagram to guide

management of LCOS.

Low Cardiac Output Low Cardiac Output StateState

• •Tachycardia, oliguria, Tachycardia, oliguria, poor perfusion, low BPpoor perfusion, low BP

• •Metabolic acidosisMetabolic acidosis

• •Rising lactateRising lactate

• •Low venous saturationLow venous saturation

Exclude specific problemExclude specific problem

• •Airway/ventilationAirway/ventilation

• •Pericardial tamponadePericardial tamponade

• •Pulmonary hypertensionPulmonary hypertension

• •ArrhythmiaArrhythmia

• •Residual lesionResidual lesion

• •Electrolyte abnormalityElectrolyte abnormality

Evaluate and treat specific problem • ECHO

• Atrial ECG • Surgical /medical intervention

Assess PreloadAssess Preload

clinical examclinical exam,,

CVP, LAPCVP, LAP..

• •Fluid challenge 5-10Fluid challenge 5-10ml/kg of 4% Albuminml/kg of 4% Albumin

or give blood ifor give blood if::

Hb<10-12Hb<10-12

))acyanoticacyanotic ( (or <12-14 or <12-14 (cyanotic)(cyanotic)

• •Reassess and repeatReassess and repeat

• •Consider effects ofConsider effects of

ventilation on venous ventilation on venous returnreturn

low

Left Left VentricleVentricle

afterloadafterload

Right Right VentricleVentricle

afterloadafterload

• •Short/long Short/long actingacting

vasodilatorsvasodilators

• •InodilatorsInodilators

• •Positive pressurePositive pressure

ventilationventilation

• •SedationSedation

• •High FiO2High FiO2

• •iNOiNO

• •Optimal PEEPOptimal PEEP

high

high(PHT)

Systolic Systolic functionfunction

InotropyInotropy

• •dobutaminedobutamine

• •low dose low dose adrenalineadrenaline

• •Increase preloadIncrease preload

• •Lusitopy Lusitopy (milrinone)(milrinone)

• •Atrial “kickAtrial “kick””

Diastolic function

reduced

reduced

Minimise effects Minimise effects of LCOSof LCOS

• •Diuretics/PDDiuretics/PD

• •Optimal nutritionOptimal nutrition

• •Optimal Optimal ventilationventilation

ConsiderConsider

• •Sternal Sternal reopeningreopening

• •HypothermiaHypothermia

• •Mechanical Mechanical supportsupport

not improving

CONCLUSIONLCOS is a common problem in paediatric intensive care that is often predictable and sometimes preventable .

Diagnosis relies on anticipation, clinicalfeatures and investigation .

Management is aimed at achieving the optimal balance between oxygen delivery and oxygen consumption .

Preload and afterload should be optimized prior to escalation of inotropic support. The effects of PPV and non-pharmacological strategies should not be underestimated.