ANAESTHESIA FOR BEATING HEART SURGERY - PowerPoint Presentation

Slide1

ANAESTHESIA FOR BEATING HEART SURGERY

MODERATOR- Dr Ajay

Sood

PRESENTED BY- Dr

AnupamSlide2

INTRODUCTION –

OPCAB – performed first in

1964

CABG with CPB

The revival of OPCAB technique occurred in 1980 with two different approaches:

MIDCAB- anastomozing the LIMA to LAD through small ant left thoracotomy.

The second approach is multivessel grafting without CPB performed through a standard median sternotomy, which gives access to all coronary vessels, and allows standard techniques of mammary artery harvesting.Slide3

The challenge in beating heart CABG surgery is that it can

be difficult to suture or "sew" on a beating heart

. The surgeon must use a "stabilization" system to keep the heart steady.

The stabilization system consists of a heart

positioner

/surgical maneuvers to position heart and a tissue stabilizer. The

heart

positioner

guides and holds the heart in a position that provides the best access to the blocked arteries. The

tissue stabilizer

holds a small area of the heart ,its placed on

epicardium

over the

arteriotomy

site to provide regional

immobilisation

, while rest of the heart is beating normally.

The Octopus

®

 Tissue Stabilizer. Hs 2 flanged

suction devices

with cups

under the

flanges which lift & stabilize the myocardium. Its attached to vacuum of 400-600 mm hg..adv- it lifts than to compress heart.Slide4
Slide5

SURGICAL ASPECT:-

midline sternotomy…. the left internal mammary artery is harvested. At the time of harvesting, few surgeons wish to administer half dose of heparin (1mg.kg-1) to the patient. Prior to commencement of grafting i.e. before the placement of

ts

stabilizers, ‘full

heparinization

’ is achieved by administering 2-3mg.kg-1 of heparin intravenously.

ACT >240

secs

is considered adequate. Repeat

evry

30 min n repeat dose of heparin if required.

The ascending aorta is exposed. A partial cross clamp is applied onto the aorta and a hole measuring 4 mm is punched in the ascending aorta; the ‘proximal end’ of the proposed conduit is

anastomosed

to aorta on this punched hole. Followed by distal anastomosis to coronary artery distal to blockade.Slide6

Heart

is‘positioned

’ by placing a few ‘mops’ underneath it.

Then,target

artery is ‘stabilized’ by placing the

epicardial

stabilization devices Commonly used are Octopus & starfish.

Stabilizing the heart to expose LAD artery and other anterior coronary arteries does not cause serious

haemodynamic

problems; however, positioning for viewing the lateral vessels (obtuse

marginals

) may cause

haemodynamic

changes.

After completion of grafting, residual

heparinization

is reversed using protamine sulfate (1 mg for every mg of heparin).

Pericardium & sternum closed closure.

Keep the

perfusionist

and CPB machine ready before.Slide7

ADVANTAGES OF OPCAB OVER CONVENTIONAL CABG:-

Decreased

ventilatory

support & ICU stay, so economically better.

Decrsd mortality from 2.9% to 2.3% in OPCAB

Decrsd complication rate from 12% to 8%

Decreased rate of blood transfusion

Decreased

coagulopathy

& renal

dysfxn

decreased neurological complications

Its of more benefit in high risk patients.

C/I in presence of

–

intracavitary

thrombi

-malignant vent

arrythmias

-deep

intramyocardial

vessels

- procedure combined with valve replacement / ventricular

aneurysmectomySlide8

PROCEDURES PERFORMED ON BEATING HEART

:-

Coronary artery bypass graft surgery

 (including 

ThoraCAB

,

a minimally invasive option performed without cutting the breastbone, as well as 

open-chest, beating-heart bypass

)

Surgery for

atrial

fibrillation

Treatment of some 

congenital heart defects

, such as closure of

atrial

septal

defect

Valve repair

 (mitral, pulmonary, or tricuspid)

Valve replacement

 (mitral or tricuspid)

Ventricular reconstructionSlide9

PROBLEMS ASSOC WITH OPCAB:-

surgeon faces two main problems:

First, to obtain an adequate exposure of anastomosis site with restrained cardiac motion; and second, to protect the myocardium from ischemia during coronary artery flow interruption.

For this purpose, he must displace the heart, compress the ventricular wall, and if possible use a technique to allow coronary perfusion while performing the anastomosis.

the anaesthetist must be prepared to handle severe hemodynamic alterations, transient deterioration of cardiac pump function, and acute intra-operative myocardial ischemia.

The team must be prepared for conversion to CPB in case of sustained ventricular fibrillation or cardiovascular collapseSlide10

GOALS OF ANESTHETIC MANAGEMENT

Provision of safe anesthesia using a technique that offers max cardiac protection and stability.

Maintaining

hemodynamics

through out intra-operative period.

Allowing early extubation, ambulation.

Providing adequate pain relief.Slide11

MONITORING:

ECG:

most imp monitoring. Stick ECG leads on the back of the pt thus decreasing the dislodgement of them in midst of surgery, as well as disturbance during handling of chest.

must ensure well visualized P & QRS complexes b4 start of d surgery.

its common to notice sudden

disappearence

of QRS in the midst of surgery due 2 change in cardiac axis caused by positioning of heart.

hrt

manipulations modify the positional relationship btwn the heart and surface electrodes thus shape of it is altered as well as amplitude is reduced..

Impiaring

its diagnostic accuracy.

On monitors …Use diagnostic mode with ST segment trending ..filtering off done.

Pulse oximetery & capnography : -

decrease in ETCO2 during heart

manpulation

is early sign of decrease in COSlide12

Intra arterial access-

rt

femoral preferred-coz 1

st,

it permits access to the central tree(less

suceptible

to

abnrml

values during alterations in BP/hypotension)..2ndly quick access to insertion of intra-aortic balloon pump.

Rt

radial

preffered

over left..after

allen’s

test…coz with left internal mammary artery harvesting left radial

ar

pulsations affected.

After artery access- take

ABG & ACT samples

Venous access & CVP-

although

rt

atrial

pressures and PCWP may b distorted

wid

d

verticalization

of heart.

SvO2 < 50% assoc with bowel

ischaemia

.Slide13

Indications 4 PAC insertion-

-LVEF <40%

-significant LV wall motion

abn

- LVEDP > 18 mmHg at rest

-recent MI & UA

- post MI complications like VSD, LV

aneurysm,MR

, CCF

- emergency surgery

-combined procedure

-

reoperation

BIS for awareness

monitoring.( <60 indicates adequate depth)

TEE

-

dcrsd

accuracy bt still interpretable..

causes of difficulty are….

as

AIR

around

hrt

,

SWABS

near esophagus &

displacement

of heart.

uses

- early

MI

detection, to assess

LV

dysfxn

, assessing improvement in myocardial fxn

after completion

of revascularization.

beware

-

Akinesia

due to tissue stabilization shud

nt

b

mistakn

for myocardial

dysfxn

.

Temp monitoring –

rectal, nasopharyngeal

U.O.

Blood loss-

trigger for transfusion 8 gm%Slide14

How to Avoid hypothermia :-

warm blanket covers in pre-op period,

keep OT warm,

Put warm blankets under patient,

The time taken for sterile preparation of the patient by painting the patient with antiseptic solution and draping by sterile sheets should be kept to the minimum.

avoid spillage of cold fluids on patient by draping with water proof sheets,

use warm

i

/v fluids,

low FGF with CO2 re-absorption circuits.Slide15

Changes in anesthetic techniques that have emerged in patient undergoing OPCABG:-

Reduction in dosage of

opioids

.

Use of shorter acting

opioids

.

Administration of

opioids

in terms of infusion.

Maintainence

with inhalational agents/

propofol

.

Use of TEA /

intrathecal

opioids

Intensive monitoring &

maintainence

of

hemodynamics

.

Early extubation.

Intensive pain management in the post-op period.Slide16

Induction & maintenance:

Disadv

of High dose morphine-

-

Vasodilation

4m histamine release

- no amnesia

- prolonged

resp

depression

Preferred

opioids

fentanyl

,

alfenta,sufent

.

- no hemodynamic

unstability

- bradycardia desired in CAD

- post op analgesia

Disadv

-

amnesia not

gauranteed

, incision can cause

incrs

HR & BPSlide17

opioids

should form the base for induction & hypnotics and BZDP shud supplement it

Induction alone

wid

HYPNOTICS

like

thiopentone

&

propofol

unsuitable as it results in……….peripheral vasodilatation & myocardial depression.

Alone

wid

BDZP

(

midaz

0.2mg/kg ) not suitable as……. doesn’t abolish surgical or intubation stimulation.

Also ……..dose and speed of induction vary

wid

every pt.

Risk of hypotension

whn

used along

wid

opioids

in induction,

give them b4 intubation to ensure amnesia… and 2 obtund response to stimulation

opioids

r used.Slide18

In pts

wid

gud

LV

fxn-

hv

strong

sympth

response to

inense

surgical

stimuluslike

incrsd HR ,BP.

Requiring large dose of

anesthetics,BB,vasodilators

or both.

high dose

opioids

(

fenta

25-50 mcg/ kg &

sulfenta

5-10 mcg/kg bolus dose

) plus BZDP

thn

followd

by MR bolus.

if TACHYCARDIA

wid

HTN use B-blockers (

metoprolol

1mg incremental dose )

..Small bolus of

thiopentone

2control if only HTN.

After induction put invasive lines

in pts

wid

Poor LV

fxn…results in hypotension with anesthetics coz of

reducton

in CO/

vasodilation

. thus may require

vasopressors

/

ionotropes

./both

…

BDZP given only if after intubation HTN response

seen.

Reduce doses

of induction agent & give

incremental

doses to obtund

hyperdynamic

response in stressful stimulations.

Put invasive lines first followed by induction

..Slide19

Muscle relaxants :

Sch

- 1-1.5 mg/kg

Atra

- 0.5- 1 mg/kg

Vecu

- 0.08-0.2 mg/kg

Pancu

- 0.08-0.15 mg/kg

Rocu

- 0.6 mg/kg

Pipecuronium

&

doxacurium

longer acting and provides stable

hemodynamics

thn

pancuronium

.

MAINTAINENCE-

opioids,MR,inhalational

Opioids

infusion ….

fenta

0.1-0.5 mcg/kg/min

Or

small top ups of

fentanyl

50mcg every 30 min….

Inhalational agents- isoflurane & sevoflurane.

Use gases to control HTN response in pts

wid

good LV fxn.Slide20

Intra-operative challenges :-

Haemodynamic

changes related to heart position:

to visualize the coronary arteries surgeon may lift the heart (

enucleation

by pericardial stitches)or place cotton mops or use tissue stabilizers (rocking tech).The anesthetist shud anticipate these steps and treat the resultant

haemodynamic

problems.

For grafting of RCA & obtuse marginal branches “

verticalization

” of the heart (posterior pericardial stitches and a gentle retracting socket) is required.

During grafting of RCA territory there can be bradycardia. Treatment includes use of atropine and

atrial

pacing if required.Slide21

During anastomosis / grafting of the

circumflex

Ar

& obtuse marginal artery

heart positioning may result in kinking or partial obstruction in the venous return & right ventricle out flow obstruction, thus causing hemodynamic compromise. Here,

RV assist pump devices can be used..to maintain

hemodynamics

.Slide22

Fig 4 The heart position using the technique of ‘rocking’ with a tissue stabilizer device.

Chassot

P et al. Br. J.

Anaesth

. 2004;92:400-413

The Board of Management and Trustees of the British Journal of AnaesthesiaSlide23

Hemodynamic alterations with cardiac manipulation results from :-

In Vertical position the

atrias

are situated below the corresponding ventricles, and the blood must flow up into the ventricular cavities.

Pressure exerted by retractor on ventricular wall, restricts local wall motion and decreases ventricular dimensions.

Vertical position of heart distorts the mitral & tricuspid valves, thus significant regurgitation may occur.

Surgical techniques-

enucleation

, heart rocking.

Intraoperative hypotension

shud b managed with

Fluid therapy, leg elevation/

trendelenberg

positioning.

Vasopressor

/

Ionotropic

support(maintain MAP > 70 mmHg )

ask surgeon to reposition cotton packs/

epicardial

stabilizers

Intra aortic balloon pump support

Look for

arrythmias

and its causes & treat themSlide24

Fig 3 Modification of mitral shape with heart manipulation reconstructed in its three‐dimensional aspect, as viewed from above (from reference 49, with permission).

Chassot

P et al. Br. J.

Anaesth

. 2004;92:400-413

The Board of Management and Trustees of the British Journal of AnaesthesiaSlide25

Intra-operative MI :-

SIGNS

: increase in PCWP or appearance of new “v’ waves .( less sensitive)

:SWMA on TEE

This can be

avoided by :

Maintaining MAP of at least 70mmHg.A mixed venous oxygen saturation of at least 60% or more is suggestive of adequate tissue perfusion.

Reduction in myocardial oxygen consumption: by avoiding tachycardia using intraoperative beta-blockers, TEA or calcium channel blockers.

Bradycardia may decrease cardiac output. It may be easier and faster to correct bradycardia by electrically pacing the patient.

A certain degree of ischemia will occur during distal anastomosis and can be prevented by using intraluminal coronary shunts.Slide26

PRECONDITIONING- volatile anesthetics such as isoflurane or sevoflurane protect the myocardium against ischemia by activation of a preconditioning- like mechanism when administered at 2 minimum alveolar concentration (MAC) at least 30 min before the ischemic insult.

intraop

Arrhythmias-

cardiac displacement increases the risk..especially reperfusion arrhythmias…maintain potassium>4.5 , magnesium given after induction.Slide27

INDICATIONS FOR CONVERSION TO CPB :-

Persistence of the followings for >15 min despite aggressive therapy:  

Cardiac index <1.5

litre

min

–1

 m

–2

Sv

O2

 <60%  

MAP <50 mm Hg  

ST‐segment elevation >2 mV  

Large new wall motion abnormalities or collapse of LV function assessed by TOE  

Sustained malignant arrhythmiasSlide28

Fast track anesthesia:-

Tracheal extubation with in 8 hours, early mobilization and early discharge from hospital.

Pts not suitable for fast tracking:- bleeding, dysrhythmias, hemodynamic instability.

Benefits- economical, early regaining of cough reflex thus lowers incidence of atelectasis, pneumonia.

To achieve early

extubation,post

op pain relief is an imp

consideraton

.Slide29

Methods of post-op pain relief:

i

/v

opioids

Patient controlled analgesia

Intercostal

nerve block

TEA

Intrathecal

opioids

Intrapleural

local anaesthesia.Slide30

THANKS