CARDIAC ANAESTHESIA

Andy McDonaldConsultant 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

Minimal access surgery• MIDCAB• Mini mitral• Mini AVR

• Becoming increasingly popular• MAVIC trial

Coronary Artery Disease

• Coronary Blood Flow• 80 ml / 100 g / min• Flow occurs 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• 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

Cardiothoracic Investigations

-­Haematology = FBC / Platelets= INR if on Warfarin, Clotting screen if current history of bruising or bleeding easily

-­Biochemistry = U/Es, Creat, LFTs, Ca, Phosphate, Alb-­ECG -­ 12 lead-­CXR -­ in the last 6 months, unless significant chest infection or new SOB-­Cross match -­ X match only unless Hb less than 10 then 2 units PC

-­ Complex emergency Aortic surgery needs 4 units PC-­Microbiology -­ if Green Sputum -­ C+S of sputum

-­ if dysuria or recent history of UTIs -­ C+S Urine-­Check pulse oximeter on air-­Respiratory Function tests if SOB at <200 yards walking or severe COPD

Scoring systems for cardiac surgery• Many different scoring systems (apache II, P-­possum)• Most aren’t validated for cardiac surgery

Coronary Angiography

MRI and CT

• MRI provides better images but is limited in patient selection• 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.

C.A.D. -­ Anaesthetic• No proven IDEAL anaesthetic-­-­-­-­ Skill of the anaesthetist• Regional -­ Dense blockade of afferent and efferent nerves • with Sympathetic block• Opiates -­ No myocardial depression• -­ Stable CVS -­ tendency to reduce HR.• -­ Suppress intubation and stress response• Volatile agents -­ Myocardial depression is dose related• . -­ Prevents awareness• Combinations of Opiates, Muscle relaxants and Volatile agents or iv Hypnotic drugs•

Pre-­bypass period• Maintain anaesthesia and haemodynamic stability while surgeon prepares conduits and cannulates for bypass

• Heparin at surgical request

• Check ACT after 2 minutes: ACT > 400s (may differ between centres)

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

De-­airing• For open heart procedures• Surgeon may use CO2• Prior to taking x clamp off, surgeon will ask for blood in the heart and “blows on the lungs”• This forces blood through left atrium to LV and aorta, where aortic vent allows air out• Echo to confirm air acceptable then x-­clamp removed

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

Difficult wean from bypass • May be predictable -­ use TOE • Ensure good ventilation and biochemistry • Pacing• Appropriate volume• Inotropes / inodilators / vasopressors• Consider intra-­aortic balloon pump • Wean slowly;; if the heart is failing, go back on and increase support, consider additional surgery• Can become a vicious spiral

Intensive care problems• Bleeding • Cardiac failure, rhythm problems• Respiratory• Neurological• Kidneys• Gut• Infection

CARDIOPULMONARY BYPASS

Cardiopulmonary bypassWhy do we need it?

Cardiopulmonary bypass (CPB) allows cardiacsurgery to be performed in a motionless, bloodlesssurgical 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 CBPCPB 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 propulsiondevice

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 loadImproved outcome has not yet been provedLoad 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 CBPTubing: 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

Acid-­Base RegulationpH-­stat management is temperature-­corrected aims for a pCO2 of 40 and pH of 7.40 at the patient’s body temperature leads to higher pCO2, respiratory acidosis and increased cerebral blood flow

Alpha-­stat acid-­base management is not temperature-­correctedas the patient’s temperature falls, the partial pressure of CO2 decreases which will manifest as a relative respiratory alkalosis coupled with decreased cerebral blood flow During alpha-­stat CBF is related to metabolic needs (CMRO2) and not to cerebral perfusion pressure. The major concern with pH stat is the potential for increasing the cerebral embolic load.

Myocardial protectionCardioplegia

Cold, hyperkalemia, procaine

Stops heart in diastole, decrease metabolic rate

Protection for 2-­3 hrs

Cardioplegia solutions

Autologous red cell salvageCell saver separates RBCs from plasma and debris by washing and differential centrifugation,

Blood is aspirated from the pericardium and heparin delivered at the tip of the suction cannula to minimize activation of coagulation

During processing, the red cells are retained but plasma, platelets, heparin, free haemoglobin, and inflammatory mediators are discarded

RBCS are resuspended in saline at haematocrit of 50–70%

Allows conservation of RBCs while reducing the retransfusion of fat microemboli, activated coagulation, and inflammatorymarkers

Hematocrit on bypassWhat should we be aiming for and why?

Off pump surgeryWhat 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 • Thrombin inhibitors -­ dabigatran• FACTOR xa INHIBITORS – apixaban, rivaroxabin

Antiplatelet drugs• Aspirin • Dipyridamole/ cilostazol• Clopidogrel, Ticlodipine, Prasugel, Ticragelor, Cangrelor (iv drug)• Apciximab, tirofiban• Vorapaxar, atopaxar

TEG• Integrated platelet function and plasma coagulation, plus fibrinolysis• Kaolin• Rapid teg• Heparinase• Platelet mapping• Functional fibrinogen

TEG• Baseline• Rewarm• Post protamine• Packs available in theatre with bottles. Results on computer in real time

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

TEG• R TIME – coag factor activity-­ FFP• MA – maximum amplitude -­platelets• EPL – Tranexamic acid• a ANGLE – depressed, FFP

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

BleedingPost-­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

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 ©

Resuscitationpost-­op cardiac surgical patient• Establish good BLS• Initiate full Cardiac Surgery Arrest Protocol• 3 shocks• Delaying CPR for shocks• Do not give adrenaline• Reopen after 3rd shock• In PEA/Asystole reopen within 5 mins

Inotropes and Vasopressors• What’s the difference?

Adrenoreceptor family

They are all very similar

JPR 18/07/2007

InotropesAdrenalineDobutamineIsoprenaline

VasopressorsNoradrenalineVasopressin

InodilatorsMilrinoneEnoximone

Calcium channel sensitisersLevosemandan

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

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

Appropriate inflation point

Appropriate deflation point

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 VV ECMO• Respiratory failure• ALI• Pneumonia• Exclude chronic lung disease and irreversible pathologies, or if ventilated with high peak inspiratory pressure (>30cmH2O) of high FiO2 for more than 7 days

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

P A Catheter

Indications PA catheterINDICATIONS

•Cardiogenic shock •Discordant right and left ventricular failure•Severe chronic heart failure•Suspected “pseudosepsis”•reversible systolic heart failure• fulminant myocarditis• peripartum cardiomyopathy

•differential diagnosis and treatment of pulmonary hypertension•Cardiac / lung transplantation

CONTRAINDICATIONS

•Tricuspid or pulmonary valve prosthesis

•Tricuspid or pulmonary valve vegetations

•Endocarditis

•Right heart mass (tumour or clot)

Information generated

Continuous Thermodilution

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.

Vigileo• Better if brachial or femoral artery used• Poor for Tachyarrhythmia like AF• Not for patients with IABP• Rapid changes in vascular tone lead to inaccuracy• Software upgrades with algorithms which allow for more exceptions to the rule

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

Oesophageal Doppler

• Parameters :-­• CO (cardiac output)SV (stroke volume)FTc (corrected f low time)PV (peak velocity)MD (minute distance) HR (heart rate )

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?