Coronary Artery Bypass Graft

CABGAziza Alamri..

:Outlines Definition of CABG Review of Coronary Arteries Purposes Indications for CABG Contraindications for CABG Procedure Respiratory management Complications References

Definition Is a surgical procedure performed to

relieve angina and reduce the risk of death from coronary artery disease.

Arteries or veins from elsewhere in the patient's body are grafted (internal thoracic arteries, radial arteries and saphenous) to the coronary arteries to bypass atherosclerotic narrowing's and improve the blood supply to the coronary circulation supplying the myocardium (heart muscle). This surgery is usually performed with the heart stopped .

What does (single, double, triple, quadruple and

quintuple) bypass refer to?

They refer to the number of coronary arteries bypassed in the procedure.

In other words : Double bypass means two coronary

arteries are bypassed (e.g. the left anterior descending (LAD) coronary artery and right coronary artery (RCA)

Triple bypass means three arteries are bypassed (e.g. LAD, RCA, left circumflex artery (LCX)

Quadruple bypass means four vessels are bypassed (e.g. LAD, RCA, LCX, first diagonal artery of the LAD)

Bypass of more than four coronary arteries is uncommon.

Review Of Coronary Arteries

Purposes

Restore blood flow to the heart Relieves chest pain and ischemia Improves the patient's quality of life Enable the patient to resume a

normal lifestyle Lower the risk of a heart attack

Indications Patients with blockages in coronary

arteries Patients with angina Patients who cannot tolerate PTCA

(Percutaneous transluminal coronary angioplasty ) and do not respond well to drug therapy

Acute myocardial infarction Sever coronary artery disease

Contraindications Aneurysms Valvular diseases Congenital diseases diseases of blood

Procedure An endotracheal tube is inserted

and secured and mechanical ventilation is started. General anesthesia is maintained by a continuous very slow injection of Propofol .

The chest is opened via a median sternotomy and the heart is examined by the surgeon involves creating a 6-8 inch incision in the chest .

 The heart is cooled with iced salt water, while a preservative solution is injected into the heart arteries. This process minimizes damage caused by reduced blood flow during surgery and is referred to as "cardioplegia."

The most commonly used grafts for the bypass are the internal thoracic arteries, radial arteries and saphenous veins.

When the wanted vessels are harvested , the patient is given heparin to prevent the blood from clotting.

 Before bypass surgery can take place, a cardiopulmonary bypass must be established. Plastic tubes are placed in the right atrium to channel venous blood out of the body for passage through a plastic sheeting (membrane oxygenator) in the heart lung machine

Do you think that Cardiopulmonary bypass

and ECMO are the same?

The differences between ECMO and cardiopulmonary bypass are as follows:

ECMO is frequently instituted using only cervical cannulation, which can be performed under local anesthesia; standard cardiopulmonary bypass is usually instituted by transthoracic cannulation under general anesthesia

Cardiopulmonary bypass, which is used for short-term support measured in hours, ECMO is used for longer-term support ranging from 3-10 days

Cont..

The oxygenated blood is then returned to the body. Once Cardiopulmonary Bypass is established, the surgeon places the aortic cross-clamp across the aorta and instructs the perfusionist to deliver cardioplegia to stop the heart and slow its metabolism.

One end of each graft is sewn on to the coronary arteries beyond the blockages and the other end is attached to the aorta.

Chest tubes are placed in the mediastinal and pleural space to drain blood from around the heart and lungs.

The sternum is wired together and the incisions are sutured closed.

The patient is moved to the (ICU) to recover.

Ones the patient is in the ICU he/she should be monitored .

After awakening and stabilizing in the ICU (approximately one day), the person is transferred to the cardiac surgery ward until ready to go home (approximately four days).

Respiratory management

A study was done by the Saudi journal of anesthesia in 2011 about a Comparison of two ventilation modes in post-cardiac surgical patients ..

They were saying that The cardiopulmonary bypass (CPB)-associated atelectasis accounted for most of the marked post-CABG, increase in shunt and hypoxemia.

They hypothesized that (PRVC) modes having a distinct theoretical advantage over (PCV) by providing the target tidal volume at the minimum pressure may prove advantageous while ventilating these atelactic lungs.

36 post-cardiac surgical patients with a PaO2/FiO2 < 300 after arrival to ICU .

They were randomized to receive either PRVC or PCV .

 (Paw) and (ABG) were measured at four time points :

• T1: After induction of anesthesia.• T2: after CPB (in the ICU).• T3: 1 h after intervention mode.• T4: 1 h after T3

Oxygenation index was calculated for each set of data and used as an indirect estimation for intrapulmonary shunt.

)OI = (

[PaO2/ {FiO2 × mean airway pressure (Pmean)}]

Result:There is a steady and significant

improvement in OI in both the groups at first hour and second hour of ventilation.

However, the improvement in OI was more marked in PRVC at second hour of ventilation owing to significant low mean air way pressure compared to the PCV group

They Concluded that PRVC may be useful in a certain group of patients to reduce intrapulmonary shunt and improve oxygenation after cardiopulmonary bypass-induced perfusion mismatch.

Weaning

Pre-Weaning CriteriaWeaning Criteria

Pre-Weaning CriteriaNo acute ischemiaHemodynamically stable.Absence of new arrhythmia Blood loss < 2cc/kg/ hourUrine output > 1cc/kg/hour Demonstrating signs of awakening

from anesthesia Core temp 97.0 or greater

Weaning CriteriaPatient is awake and cooperative

( follows commands )Able to lift head off pillow PO2 > 80 mmHg with FIO2 < .40 with

PEEP 5 cmH2O or less and PS 5cmH2O or less

Spontaneous tidal volumes > 5cc/kg Respiratory rate < 30

Assess patient for placement on CPAP 5 cmH2O with PS 5 cmH2O.

After PS of 5cmH2O for 20 to 30 minutes, obtain an ABG.

CPAP should not exceed one hour.

If ABG obtained in CPAP trial meets the following criteria: pH > 7.35 , PCO2 < 45 , PO2 >80 with an FIO2 ≤ 40% . (Considered Extubation)

Criteria assessed before extubation..

NIF >30 cmH2O Vt > 5 cc/kg VC > 12 cc/kg

After Extubation..

After physician approval , the patient will be extubated to 40% aerosol mask.

After 4 hours on the aerosol mask, the patient can be placed on a 5 LPM humidified nasal cannula if pulse oximeter readings are consistently above 95%. The oxygen can be weaned as long as the pulse oximeter is consistently above 95%.

Post Extubation Treatments

IPPB treatments* should be started within 2 hours of extubation. If the patient is unable to cooperate with a mouthpiece, IPPB with a mask should be attempted.

*IPPB treatment with racemic epinephrine will reduces glottic edema and the swelling caused by the tube and its removal

Patients with a history of smoking and have not quit within one year prior to the surgery will receive a unit dose of albuterol with each treatment.

Other patients will receive normal saline with each treatment.

When patient is alert incentive spirometry will be used .

ComplicationsBleedingHeart attackHeart failureArrhythmiaStrokePleural effusionsWound infectionRenal failureDeath

References Medscape

http://emedicine.medscape.com/article/1893992-overview

AHA http://my.americanheart.org/professional/General/2011-ACCFAHA-Guideline-for-Coronary-Artery-Bypass-Graft-Surgery

Textbook Brunner and Siddhartha's Textbook of Medical-Surgical Nursing , 12th edition, Brunner and Siddhartha's Textbook of Medical-Surgical Nursing 2012

CABG Clinical Pathway Steering Committee Saudi J anasthesia

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3139311/

EXTUBATION: GUIDELINES http://www.rcecs.com/myce/pdfdocs/course/v7020.pdf

Thank You For Listening