Introduction

Open heart surgery is any surgery where the chest is opened and surgery is done on the heart muscle, valves, arteries, or other parts of the heart (such as the aorta). The term "open" means that the chest is "cut" open.

The definition of open heart surgery has become confusing because new procedures are being done on the heart through smaller cuts. Some new procedures are being done with the heart still beating(off pump).

Conditions commonly treated with open heart surgery include• Heart valve surgery• Atrial septal defect • Cardiac transplant• Coarctation of the aorta • Congenital heart defect corrective surgery• Heart bypass surgery (coronary artery bypass graft - CABG)• Mitral valve surgery • Tetralogy of Fallot • Ventricular septal defect (VSD)

indication• Congenital defect repair,

• Coronary artery bypass graft (CABG), commonly called heart bypass surgery. CABG provides a new route around diseased coronary arteries with healthy vessels taken from other places of body. This is the most common heart surgery in adults.

• Heart transplant to remove a severely damaged heart and replace it with a donor heart

• Heart valve repair or replacement when a heart valve does not function

properly. Heart valves control the flow of blood into and out of the heart.

Conti…• Implantation of medical devices to help control heartbeat or support

proper heart function

• Transmyocardial laser revascularization when coronary artery bypass is not an option.

• The surgeon uses lasers to make channels directly in the heart muscle to supply it with blood.

• Maze procedure, which is the creation of scar tissue to block irregular electrical signals through the heart.

• The Maze procedure is used to treat atrial fibrillation or an irregular heartbeat that is not amenable to medications or less invasive methods.

Types of open heart surgery

• The types of open heart surgery procedures include:• On-pump surgery uses a heart-lung machine (cardiopulmonary bypass). This

machine temporarily takes over the heart’s job of pumping oxygen-rich blood to the organs and tissues. This is the traditional type of open heart surgery. It allows surgeon to operate on a heart that is not beating and has no blood travelling through it.

• Beating heart or off-pump surgery does not use a heart-lung machine and surgeon operates on an actively beating heart. However, surgeon will slow heart rate with medication or a device. This type of open heart surgery is limited to a few specific procedures.

• Robot-assisted surgery allows surgeon to use a special computer to control robotic arms that perform the surgery. The surgeon sees a three-dimensional view of the surgery on the computer. This type of surgery is very precise. However, it also is limited to a few specific procedures.

Pre-operative assessment• Before cardiac surgery, the patient’s history should be taken n carefully

examination for factors that might predispose to complications, such as the following:

Cardiac Risk Index Criteria :

• History of myocardial infarction • History of current angina

• Use of sublingual nitroglycerine

• Positive exercise test results Q waves on electrocardiogram

Conti…• Patients who have undergone percutaneous transluminal coronary angioplasty

or coronary artery bypass graft surgery and who have chest pain presumed to be

of ischemic origin

• History of transient ischemic attack

• History of cerebrovascular accident

• Diabetes mellitus requiring insulin therapy

• Chronic renal insufficiency, defined as a baseline creatinine level of at least 2.0 mg/dL .

Routine preoperative investigations

• Full blood count (abnormalities corrected)• Clotting screen• Creatinine and electrolytes • Liver function tests• Screening for methicillin-resistant Staphylococcus aureus• Chest radiography• ECG• Echocardiography or ventriculography (to assess LV function)• Coronary angiography (to define the extent and location of CAD)

Monitoring

In addition to the standard anesthetic monitoring (ECG, pulse oximetry, nasopharyngeal temperature, urine output, gas analysis),

Specific monitoring requirements for cardiac surgery include the following: • Invasive blood pressure

• Central venous access

• Transesophageal echocardiography (TEE)

Arterial line

• An arterial line is a fine plastic tube, called a cannula, which is inserted into the patients’ artery. The cannula is attached to a transducer and infusion line (drip).

There are two main purposes of an arterial line. • Firstly when patients are very sick an arterial line is inserted to provide constant

monitoring and recording of the patient’s blood pressure.

• Secondly some patients require frequent blood tests and the arterial line provides easy access to a patient’s blood.

• Thus reducing the number of times a blood vessel will be accessed with a needle and reducing patient pain.

• Arterial blood gases (ABG) are important blood tests that assist in monitoring the patient’s oxygen status. An ABG can only be taken from an artery.

Pulmonary Artery Catheter

• Invented in 1970 by Swan, Ganz and colleagues for hemodynamic assessment of patients with acute myocardial infarction.

• Standard PAC is 7.0, 7.5 or 8.0 French in circumference and 110 cm in length divided in 10 cm intervals

Pulmonary Artery Catheter

• PAC has 4-5 lumens:– Temperature thermistor located

proximal to balloon to measure pulmonary artery blood temperature

– Proximal port located 30 cm from tip for CVP monitoring, fluid and drug administration

– Distal port at catheter tip for PAP monitoring

– +/- Variable infusion port (VIP) for fluid and drug administration

– Balloon at catheter tip

Indications• Diagnostic assessment of shock states (cardiogenic, distributive, hypovolemic) and assessment

of response to treatment Using cardiac output, stroke volume, systemic vascular resistance • LV preload and LV performance, pulmonary vasomotor tone, intravascular volume status,

especially in the context of acute lung injury • Right heart pressures Using right atrial pressure, pulmonary artery pressure • Intracardiac shunt• Assess volume status• Assess RV or LV failure• Assess Pulmonary Hypertension• Assess Valvular disease• Cardiac Surgery

• Sites • IJV, subclavian, femoral also possible

Pulmonary Artery Catheterization

Hemodynamic Parameters

Premedication

• The aims of premedication are to minimize myocardial oxygen demands by reducing heart rate and systemic arterial pressure and to improve myocardial blood flow with vasodilators. Drugs that should be continued up to the time of surgery are as follows:

• Beta-blockers, calcium channel blockers, and nitrates

• Agents given are as follows:• Temazepam immediately preoperatively• Midazolam, a small IV dose in the operating room before arterial line insertion• Each patient should be cross-matched with blood , fresh frozen plasma, and platelets .

Tranexamic acid (bolus 1 g before surgical incision followed by an infusion of 400 mg/hr during surgery) may be considered to reduce postoperative mediastinal bleeding and blood product (ie, red blood cell and fresh frozen plasma) use

induction

• Monitoring equipment is attached and peripheral venous access achieved but before the arterial line is inserted, the midazolam dose is administered. Before placement of the arterial line, it should be ensured that a radial artery graft will not be used for CABG.

• Cardiac surgery makes use 2 forms of neuraxial blockade:• Intrathecal opioid infusion

• Thoracic epidural anesthesia (generally a low-dose local anesthetic/opioid infusion)

• During induction and tracheal intubation, it is important to maintain a steady heart rate and blood pressure.

• Patients should be preoxygenated. • Induction of anesthesia is accomplished by using high doses of opioid (usually fentanyl 20-

40 microgrm/kg or remifentanil) to minimize the dose of propofol, etomidate0.3mg/kg, or thiopental 2.5-4.5mg/kg and thereby maximize cardiovascular stability.

• Although etomidate usually minimal myocardial depression then propofol and thiopental.

Conti…A number of agents may be used for muscle relaxation

Intubating dose of muscle relaxant:

• Succinylcholine 1mg/kg duration 5-10min.• Pancuronium 0.08-0.12mg/kg duration 60-120min.• Vecuronium 0.15-0.2mg/kg/ duration 45-90min.• Rocuronium 0.6-1mg/kg duration 35-75min.• Atracurium0.5-0.6mg/kg duration 30-45min

Conti…• However, they each have their own associated complications, as follows:

Succinylcholine is depolariser and lead to cardiac arrhythmias and bradycardia.• Pancuronium Increases myocardial oxygen demand by increasing HR, CO and BP. Vagal effect produse by anaesthesia and surgical stimuli that concealed by

vagolytic effect of Pancuronium

• Vecuronium may cause bradycardia in association with opioids

• Rocuronium can cause tachycardia, and also decrease PAP.

• Atracurium (which is not considered suitable for operations of long duration) can cause hypotension secondary to histamine release.

conti…• Votatile anaesthetic agent• Halothane decrease BP due to decrease SV and CO.• It sensitises the myocradium to catecholamines n lead to development of arrhythmias.

• Isoflurane • It causes dose dependent decrease in BP, by decreasing SVR• It dose not destablise the heart rhythm even in presence of Adr.

• Enflurane• It also sensitises the myocradium to catecholamines • It produse coronary vasodilatation lead to decrease coronary perfusion pressure.• It produse fluoride ions which may toxic to kidney.

• Sevoflurane• Most common use in cardiac surgery due to favorable haemodynamic effect and

cardioprotective property.• It decrease SVR arterial BP and CO in dose dependent fashion with tendency to lower HR.

Conti…• The trachea should be intubated orally because nasal intubation may cause significant

bleeding once heparin is administered.

• A double-lumen endotracheal tube is required if CABG is being performed via a left thoracotomy.

•

• Central venous access should be obtained. It is not uncommon for the patient to become hypotensive. To ensure that there is sufficient diastolic pressure to maintain coronary perfusion, hypotension should be treated with IV fluids or with an alpha agonist if LV function is depressed.

• Typically, maintenance of anesthesia is accomplished with an opioid infusion (fentanyl,

alfentanil, sufentanil, or remifentanil) combined with either a propofol infusion (total IV anesthesia) or a volatile agent. Volatile agents are generally carried in an air-oxygen mixture because the use of nitrous oxide as a carrier is controversial. Isoflurane may have a myocardial protective effect and therefore is especially useful in off-pump surgery.

Cardiopulmonary bypass machines

• The CPB machine has five basic components: Venous reservoir, an oxygenator, a heat exchanger, a main pump, and an arterial filter.

• Venous reservoir • The reservoir of the CPB machine receives blood from the patient via one or two

venous cannulas in the right atrium or the superior and inferior vena cava. • Blood flows to the reservoir by gravity drainage. Because venous pressure is

normally low,

• Oxygenator• Blood is drained by gravity from the bottom of the venous reservoir into the

oxygenator, which contains a blood–gas interface that allows blood to equilibrate with the gas mixture (primarily oxygen).

Conti…• Heat Exchanger• Blood from the oxygenator enters the heat exchanger. • The blood is then either cooled or warmed, depending on the temperature of the

water flowing through the exchanger (4–42°C); heat transfer occurs by conduction. • Main Pump• Modern CPB machines use either an electrically driven double-arm roller (positive

displacement) or a centrifugal pump to propel blood through the CPB circuit.

• Arterial Filter• Particulate matter (eg, thrombi, fat globules, calcium, tissue debris) enters the CPB

circuit with alarming regularity. • Although filters are often used at other locations, a final, in-line, arterial filter is

mandatory to prevent systemic embolism. .• The filter is also designed to trap air,

Management of CPB machine Step-by-Step

Priming - HemodilutionHeparinization Hypothermia - Aortic Clamping - Myocardial protection → Total CPBIntra-CPB monitingRewarming - Weaning from CPB

Priming - Hemodilutionfilling the CPB circuit with blood or blood substitutesresult in hemodilution

Priming Solutions:-Crystalloid

• Isotonic Saline, Ringer’s solution, Lactated Ringer’s, Dextrose solutionsColloid primes

• Albumin 5~25%, , 5% plasma protein fraction, 6% hydroxyethyl starch, FFPBlood components: pRBC, (autologus) Whole bloodOther additives

• Mannitol, Heparin, Corticosteroids, Calcium

Conti…Advantages:• Reduce transfusion and transfusion complications• Lower blood viscosity, improve organ perfusion• Decrease the mechanical destruction of blood cells at extracoporeal circuit• Lower immune and Inflammatory response• Coagulability ↓, reduce emboli formation

Heparinization• Typically a loading dose of 200-300 u/kg of heparin is given and then heparin activity

is monitored by measuring ACT ,( binds with antithrombin III )

• Check to see if ACT is 450-480 sec. then administer supplemental heparin based on subsequent ACT levels :

• Method: give directly into a central vein or right atrium, verification ACT in 3~5 mins• Target: Activated Coagulation Time (ACT) > 480 secs, don’t begain CPB if ACT is less than

300secs

Conti..• Hypothermia• Advantages: This protection occour because of a decrease metabolic rate and oxygen

consumption.

The metabolic rate is determined by enzymatic activity which is depend on temprature.

This also decrease rate of degradative reactions, increase tolerance to ischemia reduces K+ necessary for cardiac arrest

It also inhibits intracellular Ca2+ accumulation

Conti…

• Monitoring:

Core temperature: nasopharyngeal or tympanic membrane probes reflect brain temperature

Shell temperature: rectal probe or skeletal muscle needle sensor Mild to moderate (24~28 ) systemic hypothermia is preferred for its ℃protective effectscontrol cooling speed, evenly .

Conti…

Aortic cross-clampingAfter adequate cooling, reduce perfusion speed and cross-clamp the ascending aortaestablish total CPB

Myocardial protectionThe term myocardial protection refer to strategies and mathadologies used either to attenuate or to prevent post ischemic myocardial disfunction that occours during and after heart surgery.

Reduction of metabolic activity by hypothermia.Therapeutic arrest of contractile appearatus and all electrical activity of myocite by administating cardioplagic solution(eg. Depolarizing of membrane potential by high potassium blood cardioplagia

Maintenance of normal cellular integrity and function during CPB depends on reducing energy expenditure and preserving the availability of high-energy phosphate.

This is accomplished by systemic and topical cardiac hypothermia(Ice flushing, about 4 ) and ℃the use of potassium cardiplegiaAvoid ventricular fibrillation and distention(LV venting)

Conti…CardioplegiaFollowing initiation of CPB, induction of hypothermia, and aortic clamping, The coronary circulation is infused intermittently with cold cardioplegiaextracellular K+↑ → transmembrane potential↓ → inactivate Na+ channel → cardiac arrest

Repeated about every 30 minutes

Cardioplegic solutions

Constituent Concentration Effects

K+ 10~40mEq/L maintain cardiac arrest

Na+ <140mEq/L

Ca2+ 0.7~1.2mmol/Lmaintain cellular

integrity

Mg2+ 1.5~15mmol/L control excessive calcium influx

Buffers (bicarbonate or THAM) pH 7.5~7.6

buffer acid metabolites, improve myocardial

preservation

Hypertonic agents (Mannitol) control cellular edema

Glucose, glutamate, asparate energy substrates

Blood Hct 20~30% provide oxygen

Conti…

Intra CBP Monitoring• Flow rate• Blood pressure(MAP,CVP, PAP)• Hematocrit• SaO2, SvO2

• Temperature• Anticoagulation(ACT)• Blood gas• Electrolytes• Urine output

Conti…

Blood pressureMAP: in mild to moderate hypothermia

• normal adult: > 50mmHg• adult with HTN, CAD, DM, and old age: > 60mmHg• infants: > 30mmHg

Management:• maintain adequate blood volume, α-receptor agonist, ephedrine,

norepinephrine, fentanyl.

Conti…

ElectrolytesCa2+ :

• maintain between 0.6~1.0 mmol/L, to avoid rapid accumulation of intracellular calcium during reperfusionK+ :

• excessive cardioplegia, severe hemolysis, and acidosis lead to hyperkalemia

• Management: Ca2+ supplement, bicarbonate, ultrafiltration, glucose & insulin administration

Off CPB: (Weaning)

Preparation: Rewarming

Target: Core Temperature > 37 , Shell Temperature > 34℃ ℃

Rewarming Evenly!!: use vasodilatorHypothermia induce ventricullar fibrillation

• Spontaneous myocardial activity• ABG, electrolyte , Hct, to be optimized• Ventilation started• Trendlenburg position to remove intra cardiac air.• Beating heart examined by visually TEE

Conti…• Poor contraction- give inotrops• Decrease SVR give vasopressore

• As pt.meets criteria for sepration from CPB

• Perfusionist gradually clamps venous tubing so decrease blood flow to reservoir and increase venouse return to heart.

• Arterial pump head is slowed cause gradually filling the heart.• Appropriate preload is established• Pulsatile arterial wave achieved and CBP terminated.

Morbidity Associated With open heart Surgery

Neurological Events• Neurological impairment after open heart surgery may be attributable to hypoxia,

emboli, hemorrhage, and/or metabolic abnormalities.

• Postoperative neurological deficits have been divided into 2 types:

• Type 1, associated with major, focal neurological deficits, stupor, or coma;

• Type 2, in which deterioration in intellectual function is evident. Mediastinitis• Deep sternal wound infection occurs in 1% to 4% of patients after bypass surgery

and carries a mortality of ≈25%.

• Predictors of this complication include obesity, reoperation, use of both internal mammary arteries at surgery, duration and complexity of surgery, and diabetes.

Conti…Renal Dysfunction

• Postoperative renal dysfunction occurs in as many as 8% of patients.

• Among patients who develop postoperative renal dysfunction (defined as a postoperative serum creatinine level >2.0 mg/dL ), 18% require dialysis.

• Overall mortality among patients who develop postoperative renal dysfunction is 19% and approaches two thirds among patients requiring dialysis.

• Predictors of renal dysfunction include advanced age, a history of moderate or severe congestive heart failure, prior bypass surgery, type 1 diabetes, and prior renal disease.

• Patients with advanced preoperative renal dysfunction who undergo CABG surgery have an extraordinarily high rate of requiring postoperative dialysis.

• Among patients with a preoperative creatinine level >2.5 mg/dL, 40% to 50% require hemodialysis.

Conti…Long-Term Outcomes

• Predictors of poor long-term survival after bypass surgery include advanced age, poor LVEF, diabetes, number of diseased vessels, and female sex.

• In some studies, additional predictors include angina , hypertension, prior MI, renal dysfunction, and clinical congestive heart failure.

• Predictors of the recurrence of angina, late MI, or any cardiac event also include obesity , as well as those factors identified above. Of these events, the return of angina is the most common and is primarily related to late vein-graft

atherosclerosis and occlusion.

Venous thromboembolism

• Venous thromboembolism (VTE), which includes deep venous thrombosis (DVT) and pulmonary embolism (PE), are quite common causes of morbidity and mortality that are largely preventable in the postoperative patient.

• Surgical patients in particular have significantly increased risks for VTE due to advanced age, multiple medical comorbidities, and prolonged procedure times, in addition to the hypercoagulable state of surgery and immobility. Thus, clinicians must consider VTE risk and risk-reduction strategies in all patients undergoing surgery.

• Patient-related risk factors for VTE include age older than 40 years, malignancy, immobilization, varicose veins, severe cardiopulmonary disease (prior MI, congestive heart failure, chronic obstructive pulmonary disease), prior stroke, paralysis or spinal cord injury, prior VTE events, hyperviscosity syndromes (polycythemia vera or malignancy related), and major vascular injury.

Conti…• prevent VTE events are categorized into nonpharmacologic and pharmacologic means.

• Nonpharmacologic methods include:• early ambulation, • graduated compression stockings, • intermittent pneumatic compression devices.

• Pharmacologic methods routinely evaluated include:• aspirin,• low-dose unfractionated heparin (LDUH)• low-molecular-weight heparin (LMWH)• warfarin, and• factor Xa inhibitors such as fondaparinux.

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