CARDIAC ANAESTHESIA

Andy McDonald

Consultant Anaesthetist, The James Cook

University Hospital, Middlesbrough

The curriculum

ACTACC website

ACTACC website

Past questions • 2017 Off pump CABG

• 2016 Tamponade, AS/ AVR

• 2015 Neurological complications of CABG, anticoagulation for CPB

• 2014 Cardioplegia, paediatric CHD/ASD, antibiotic prophylaxis for endocarditis, ICDs and anaesthesia, obstetric mitral stenosis,

• 2013 DC cardioversion, tamponade, heart transplant and anaesthesia

• 2012 Off pump CABG

• 2011 Neurological complications of CABG

• 2010 IABP

• 2009 Aortic dissection, AF management, DC cardioversion

• 2008 Obstetric ASD

• 2007 ICDs and anaesthesia

• 2006 Cardiac risk in non-cardiac surgery, AS

• 2005 TTE

• 2004 Tamponade, endocarditis and antibiotic prophylaxis

Who gets heart surgery

• Heart surgery is for…

• Coronary artery disease

• Valvular heart disease

• Electrophysiology problems – ablation, pacing

• Thoracic aortic aneurysm and dissection

• Cardiac trauma, tamponade, pericarditis

• Cardiac tumours

• Pulmonary embolus

• Congenital heart disease

• Transplantation

Coronary Artery Disease

• Coronary Blood Flow

• 80 ml / 100 g / min

• Flow occurs primarily in Diastole

• Coronary anatomy

• Epicardial arteries

• Intramyocardial arterioles

• Collateral flow in the Subendocardial region

• Myocardial Ischaemia

Aetiology of heart valve disease

• Stenotic valves

• congenital abnormality

• degeneration through atherosclerosis

• damage from rheumatic fever

• excessive calcification in old age

• Regurgitant valves

• bacterial infection or inflammation of a valve

• excessive floppiness of the leaflets (mitral valve prolapse)

• coronary disease with ischaemia or infarct to papillary muscles

• enlargement of the heart or aorta – can affect MV, AV, TV

Pre-op Assessment

• Significant predictors • MI, Unstable angina (ACS)

• CCF, Diabetic,

• Raised BP, CVA

• Peripheral vascular disease

• Clinical History

• Respiratory Function tests if SOB at <200 yards walking or severe COPD

• ECG – 12 lead

• ECG Stress test • Exercise or Drug induced

(Dobutamine)

• Sensitivity 67% and specificity 75%, Death 1/10,000

• Angiogram • Gold standard

• Risk - Allergy, CVA, Haematoma, Arrhythmia, Angina, Death

• Radionuclide scan for myocardial perfusion • Tec or Thallium - Sensitivity 81%

and specificity 90%

• NMR scans

• ECHO

• Left or Right heart cath - pressures across valves

• Carotid Doppler scan • CVA in last 6 months

Scoring systems for cardiac surgery

• Many different scoring systems (apache II, P-

possum)

• Most aren’t validated for cardiac surgery

MRI and CT

• MRI provides better images but is limited in patient

selection

• Better modality for assessing failure

• CT quicker and easier

• Who needs it?

• Redo

• Mini mitral

• CHD

Routine cardiac anaesthesia

• Arrival in anaesthetic

room

• WHO checklist

• ECG – 5 lead

• Pulse Oximeter

• Intravenous access and

arterial line

• External defibrillation

pads (if indicated)

• Induction of

anaesthesia and

intubation

• Central venous access

• +/-pulmonary artery

catheter

• Urinary catheter

• Antibiotics & tranexamic

acid

• TOE insertion

• Temperature probe

Antibiotics

• The majority of pathogenic organisms isolated from patients with SSIs after cardiac

surgery are Gram-positive bacteria, which are followed by Gram-negative bacteria.

Only a minority of other bacteria, anaerobes, fungi and parasites have been

identified

• For systemic antibiotic prophylaxis, numerous studies have clearly shown that

antibiotic prophylaxis with first- and second generation cephalosporins can

effectively reduce the incidence of SSI and postoperative infectious complications in

patients undergoing cardiac surgery

Patient monitoring

• ACT & TEG

• Baseline & Heparin effect

• arterial blood gases

• Glucose, Na, K, Lactate, Ca

• Brain : Bispectral index = complex EEG

• Pulmonary Artery cath

• Wedge, PAP, CI, SVRI

• Anaesthetic machine

• Pressure, Volume, Rate; O2, CO2 & Volatile agent %

• TOE

• Cardiopulmonary bypass monitors

Anaesthetic for patient with C.A.D

• Goals - Optimal myocardial O2 supply-demand balance

during intense Surgical Stimulation.

• Controlled HR- maximum diastolic period - CBF

• Normal afterload – high wall tension will use more O2

• Well perfused coronaries - adequate BP

• Reduce O2 demand - Pre-med, B-blocker

• Surgical goals - Revascularise the heart.

• - Optimal ischaemic protection.

Heparin management

• Heparin resistance

• Who?

• How to manage?

• Other drugs?

Stopping the heart

• Aortic cross clamping causes ischaemia

• Cardiac protection requires cardioplegia +/- cooling to

produce asystole in diastole

• Surgeon will indicate target temperature

• Cross clamp applied for open heart procedures, distal

coronary anastomoses

• Surgeon asks perfusionist to start rewarming before

clamp comes off

Preparing to come off bypass

• Warm patient

• Check rhythm and contractility - ? pacing

• Check gases, K, glucose

• Protamine and other drugs ready

• Blood products available?

• Start ventilator at surgeon’s request

Uncomplicated wean from bypass

• Confirm beating heart and adequate ventilation

• Perfusionist partially occludes venous pipe

• RV fills and contracts

• LV will produce pulsatile trace, above the cardiac output

being generated by the pump

• When venous line is fully clamped, the heart is ‘off

bypass’

• Venous line drained into pump

Protamine

• At surgeon’s request - only start to give once pump

suction out of the chest and turned off

• Clear communication with perfusionist

• Initial dose 3 - 4 mg /kg +/- infusion

• Give slowly, watching for vasodilation - responds well to

volume and vasoconstrictors

• Protamine may cause bronchoconstriction, pulmonary

hypertension, right heart failure

Haemostasis

• Surgical responsibility (mainly)

• Higher risk patient - consider ordering blood products

before bypass

• Check TEG

• “Pump blood” contains heparin; consider washing in cell

salvage

• Consider additional protamine, TXA

• Newer blood products are becoming available

Intensive care problems

• Bleeding

• Cardiac failure, rhythm problems

• Respiratory

• Neurological

• Kidneys

• Gut

• Infection

CARDIOPULMONARY BYPASS

Cardiopulmonary bypass

Why do we need it?

Cardiopulmonary bypass (CPB) allows cardiac

surgery to be performed in a motionless, bloodless

surgical field.

Anticoagulated venous blood is drained from the heart to a reservoir via cannulae and tubing, oxygenated and returned to the arterial system using a pump and oxygenator

Complications of CBP

CPB has potential for significant morbidity due to:

Cannula placement

Contact between blood and foreign surfaces, including the blood–air interface

Pump-related injury to cells and platelets

Suction and re-transfusion of blood containing fat, aggregated platelet and leucocyte microparticles

Venous drainage

•

Venous cannula usually in right atrium or vena cavae

Blood drains via PVC tubing to reservoir: alarms, filters

Circuit is primed with crystalloid fluid plus heparin, mannitol, ?blood

Perfusionist maintains levels with volume replacement, vasopressors

Oxygenator

Membrane oxygenators allow gas exchange with blood through a polypropylene membrane

Blood flows over the fibres while gas passes through them.

Hollow-fibre oxygenators allow high surface area to blood volume ratios and optimal gas exchange

The oxygen/air mixture and fresh gas flow determines the partial pressure of carbon dioxide

Roller pump

Roller pumps are the most commonly used blood propulsion device

Intermittent occlusion of the tubing causes damage to blood elements due to mechanical shear forces

Causes haemolysis and release of inflammatory mediators

Oxygenator imposes a significant resistance to blood flow; must be placed after the blood pump

Centrifugal pump

Centrifugal pumps reduce damage to

RBCs and platelets, reduce inflammatory

load

Improved outcome has not yet been

proved

Load dependent; significant change in

resistance/ pressure at the outlet or inlet

of the pump will alter blood flow rate.

Prevents generation of excessive

pressure in the extracorporeal circuit

Additional components of CBP

Tubing: simple PVC but can be coated to reduce

inflammatory or coagulation activation

Heat exchanger (current issues?)

Filters: emboli, bubbles, leukocyctes

Monitors

Suckers and cell salvage

Blood pressure

BP decreases immediately on starting bypass

V = I x R

Non-pulsatile flow, effect on autoregulation

MAP > 50mmHg

SvO2 used as indicator of adequate perfusion

Cardioplegia solutions

Off pump surgery

What are the theoretical benefits?

What is the evidence?

Benefits

-Avoid complications of CPB:

-Reduced SIRS response

-Reduced coagulopathy :platelet dysfunction, fibrinolysis, consumption of clotting factors.

-Reduced transfusion requirement

-Reduced neurological injury

-Reduced AKI

-Economic:

-Reduced duration of ventilation, ICU LOS, hospital LOS, cost.

-Results in practice are conflicting

-Possibly more benefit in higher risk patients

The ‘evidence’

THE BLEEDING

CARDIOTHORACIC

PATIENT

CLOTTING CASCADE

Inhibitors of coagulation

• Heparin – unfractionated

• LMWH

• Warfarin

• Antiplatelet drugs • Aspirin

• Dipyridamole/ cilostazol

• Clopidogrel, Ticlodipine, Prasugel, Ticragelor, Cangrelor (iv drug)

• Apciximab, tirofiban

• Vorapaxar, atopaxar

• Thrombin inhibitors - dabigatran

• FACTOR xa INHIBITORS – apixaban, rivaroxabin

BLEEDING ON CICU

• How much?

• How long?

• Cvs stability? – Bp, hr, cvp, urine output, gases

• Procedure done - bima vs lima

• Which surgeon?

• Problems in theatre?

• Temperature

Bleeding

Post-op hours Acceptable bleeding (mls/kg/hr)

1 3

2 - 4 2

4 - 12 1

One Heart 2016 ©

No amount of bleeding is normal!

BLEEDING IN CICU

• Proline deficiency

• Protamine deficiency

• Coagulation problem

• What is the patient history – clopidogrel?

• Does the patient need reopening?

INVESTIGATION

• ACT?

• TEG?

• Coaguation screen

• ECHO – TOE

• CXR

• USS

TEG

• Integrated platelet function and plasma coagulation, plus

fibrinolysis

• Kaolin

• Rapid teg

• Heparinase

• Platelet mapping

• Functional fibrinogen

Typical TEG® and ROTEM® tracings.

Amit Srivastava, and Andrea Kelleher Contin Educ

Anaesth Crit Care Pain 2013;13:12-16

© The Author [2012]. Published by Oxford University Press on behalf of the British Journal of

Anaesthesia. All rights reserved. For Permissions, please email:

journals.permissions@oup.com

TAMPONADE

• Signs/ symptoms

• CVS status

• Extubated?

• Watch induction if it is required – will be dependant on

sympathetic drive

REOPENING

• When do you re-open?

• May have the heads up from handover

• Depends on extent of bleeding/cvs stability

• Escalating inotropes

• Increasing instability

Cardiac arrest after cardiac

surgery

One Heart 2016 ©

Inotropes and Vasopressors

• What’s the difference?

Adrenoreceptor family

Inotropes Adrenaline

Dobutamine

Isoprenaline

Vasopressors Noradrenaline

Vasopressin

Inodilators Milrinone

Enoximone

Calcium channel

sensitisers

Levosemandan

Mechanical support

•For when it’s all gone tits up

Mechanical circulatory support

• IABP

• most common form of mechanical assist device

• Usually inserted via femoral artery

• Balloon positioned in descending thoracic aorta

just distal to L subclavian artery

• Balloon catheter has 2 channels – one measures

BP and one delivers helium gas

IABP

Benefits of IABP

• Inflation in diastole provides:

• Increases coronary blood flow

• Improves myocardial O2 supply

• Deflation in systole:

• Reduces LVEDP

• Reduces myocardial O2 demand

Indications for insertion of IABP

• Ongoing chest pain post MI / unstable angina despite

maximal medical therapy

• Ischaemia induced ventricular arrhythmias

• Cardiogenic shock

• Post MI

• Acute myocarditis

• Post CPB

• Post transplant

• Post MI complications eg VSD and acute MR

Contraindications

• Moderate/severe AR

• Aortic dissection

• Severe peripheral vascular disease

• End stage heart disease

Complications

• Limb ischaemia

• Thromboembolism

• Compartment syndrome

• Dissection

• Local vascular injury

• Infection

• balloon rupture

• Thrombocytopenia

• Renal or cerebral failure due to malposition

Mechanical circulatory support

• ECMO and VAD

• Insertion limited to a few centres

• Choice of device

• Cause of heart failure

• Long term treatment plan

• Bridge to recovery

• Bridge to transplant

• Destination therapy

ECMO

• To treat potentially reversible cardiorespiratory failure or

as bridge to transplant

• Drain venous blood, oxygenate, remove CO2 and return

blood to circulation

Differences to CPB

• CPB

• Requires total venoarterial bypass

• Central cannulation sites

• Stagnation of blood in pulmonary circulation, heart and reservoir

• Need full anticoagulation

• ECMO

• Partial bypass

• No stagnation

• No large reservoir

• No direct exposure of blood to air

• Partial heparinisation

Indications for VA ECMO

• Cardiac failure

• Failure to wean from CPB

• Cardiogenic shock

• Cardiac arrest

• Failure of graft after transplant

• Acute MI

Ventricular assist devices

• Augment perfusion and relieve congestion

• Mechanical pumps either in parallel (atrial cannulation) or

series (ventricular cannulation) with native ventricle

• Preferable to cannulate ventricle as provides superior

ventricular decompression, avoids ventricular stasis and

allows higher VAD flow rates

Principles of VADs

• RVAD draws venous blood from RA or RV and returns it

to PA

• LVAD draws oxygenated blood from LA and LV and

returns it to the aorta

• Requires the other ventricle to deliver adequate blood

flow otherwise need biVAD

Types of VAD

• Short term – days or weeks in critical care

• Long term – months or years

• Implanted devices

• Can be discharged from hospital

Decision making process

• How, when, LVAD/RVAD or biVAD, which device

• Four categories:

• Group 1 – precarious

• Transplant candidates precarious haemodynamics

• Group 2 – decompensated

• Untransplantable due to end organ failure but potentially reversible

• Group 3 – failure to wean from CPB

• Group 4 – salvage

• Heart failure and cardiac arrest - young

CARDIAC OUTPUT

MONITORING

Continuous Thermodilution

Information generated

Minimally Invasive CO measurement

• Arterial pulse contour analysis

• Relationship between arterial pressure and flow .

• Pulse contour methods are available

• Vigileo, PiCCO, LiDCO, Vygon PRAM and Modelflow.

• All use an invasively measured arterial blood pressure

• most need to be calibrated.

PiCO and LiDCO

• Both use dye dilution technique to calibrate the waveform

analysis

• PiCO – Transpulmonary uses arterial thermodilution

• bolus of cold solution from CVP

• arterial cannula with thermistor (femoral, brachial) –Stewart-

Hamilton Eq

• LiDCO – 150 mmol LiCl injected peripherally

• an a-line with blood pump removal and Li detector

• Li concentration-time curve

Oesophageal Doppler

• Undergone significant technological advancement

• CO = Aortic Flow velocity x area of Descending Aorta

• Oesophageal probe is inserted to the 40 cm marker

• Ideally T5-6 vertebrae

• descending aorta adjacent and parallel to the oesophagus.

• Fixed nomogram estimates aortic cross sectional area

Transthoracic ECHO

• Depends on:-

• image quality,

• sample site,

• angle of insonation,

• profile of blood flow velocity distribution across blood flow,

• velocity signal-to-noise ratio,

• estimation of aortic valve and presence of disease

CHD

Classification

Aims

• Haemodynamic stability

• Think about where the blood is flowing

• Avoid reversals of blood flow (think PA pressures)

• Special circulations eg Fontans

Transplant surgery

• Pre transplant • Severely impaired LV

• Mechanical support

• PA pressures

• Post transplant • Denervated heart

• Variable LV function

• Mechanical support

• PA pressures

Any questions?