Ped Cardiac Anesthesia Notes

8/9/2019 Ped Cardiac Anesthesia Notes

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PEDIATRIC CARDIAC ANESTHESIA

INTRODUCTION (by Jamil Elmawieh)

Congenital heart dz divided into 4 categories:

shunts, Lt to right shunt (3Ds) -> CHF, volume overload

Rt to Lt shunt -> cyanosis, pressure overload

mixing lesions (TGV,TAVR),

flow obstruction (CoA),

regurgitation valves (Ebstein)

IV induction Inhalational induction

Rt to Lt shunt(TOF, TGV, TA..)

Increases rate of IVinduction (blood

bypasses lung and go

directly to brain)

Slows rate

Lt to Rt shunt

(ASD, VSD, PDA)

Slows IV induction

(bcz IV agent is diluted)

It speeds inhalational

induction only if it

results in decreased

cardiac output

Increasing SVR:

Worsens Left to Right shunt

Ameliorates Right to Left sunt here OK for ketamine

In TOF: Ketamine is great.

Ductal patency is maintained by PGE1.


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Clin Perinatol. 1988 Sep;15(3):681-97.

Closed heart surgery for congenital heart disease in infancy.

Closed heart surgery in congenital heart disease can be palliative or corrective. Palliative surgery

aims at improving the physiologic deficit rather than the anatomic defect of the heart. Palliative

procedures aim to increase pulmonary blood flow in cyanotic children with decreased pulmonary

blood flow (Blalock-Taussig shunt), decrease pulmonary blood flow when there is unrestricted flow(pulmonary artery banding), or improve venous mixing in cyanotic children that require pulmonary

and systemic venous mixing for survival (atrial septectomy). The indications for palliation over

corrective surgery have changed over time. Now we reserve palliation for children that require low

pulmonary vascular resistance for correction, a conduit that will require replacement as the child

grows, or where the risk of the corrective procedure decreases rapidly with age.

For palliation with systemic to pulmonary artery shunts, we prefer to perform a Blalock-Taussig

subclavian to pulmonary artery shunt using a synthetic (PTFE) tube graft in infants. The operative

mortality is higher in infants under 1 month of age but is not affected by weight or diagnosis.

Palliative surgery to decrease pulmonary blood flow is restricted primarily to infants with large left-to-

right shunts where the risk of correction in infancy is high (multiple VSDs) or not feasible(univentricular heart). The operative risk for pulmonary artery banding is affected mostly by the

complexity of the cardiac defect and the clinical state of the infant (severe congestive failure) at the

time of surgery. A trial septectomy to improve venous mixing is used mostly in infants with

univentricular heart in whom a balloon septostomy was ineffective.

Section 4: Subspecialty ManagementChapter 50: Anesthesia for Pediatric Cardiac Surgery

ANESTHESIA FOR CLOSED HEART OPERATIONS

Palliative - target:

To increase PBF shunt: Blalock Taussig (extracardiac)

To decrease PBF PA banding, PDA ligation

To increase mixing atrial septostomy

Early corrective repair in infancy has significantly reduced the number of

noncorrective, palliative closed heart operations.

Corrective closed heart procedures include PDA ligation and repair of coarctationof the aorta.

Noncorrective closed heart operations include pulmonary artery bandingand extracardiac shunts such as the Blalock-Taussig shunt. These

http://www.ncbi.nlm.nih.gov/pubmed/2465112http://www.ncbi.nlm.nih.gov/pubmed/2465112http://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/v04/040000r00.htmhttp://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/v04/040000r00.htmhttp://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/v04/040047r00.htmhttp://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/v04/040047r00.htmhttp://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/v04/040047r00.htmhttp://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/v04/040000r00.htmhttp://www.ncbi.nlm.nih.gov/pubmed/2465112


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procedures are performed without cardiopulmonary bypass. Therefore, venousaccess and intra-arterial monitoring are important in evaluating and supportingthese patients. A pulse oximeter remains an invaluable monitor duringintraoperative management.

Ligation of PDA is typically performed through a left thoracotomy, although video-

assisted thoracoscopic techniques are increasingly common. Physiologicmanagement is that of a left-to-right shunt producing volume overload. Patientswith a large PDA and low PVR generally present with excessive pulmonary bloodflow and congestive heart failure. Neonates and premature infants also run therisk of having substantial diastolic runoff to the pulmonary artery, potentiallyimpairing coronary perfusion. Thus patients range from an asymptomatic healthyyoung child to the sick ventilator-dependent premature infant on inotropic support.The former patient allows for a wide variety of anesthetic techniques culminatingin extubation in the operating room. The latter patient requires a carefullycontrolled anesthetic and fluid management plan. Generally a trial of medicalmanagement with indomethacin and fluid restriction is attempted in the prematureinfant prior to surgical correction. In the premature infant, transport to theoperating room can be especially difficult and potentially hazardous, requiringgreat vigilance to avoid extubation, excessive patient cooling, or venous accessdisruption. For these reasons, many centers are now performing ligation in theneonatal ICU. Intraoperatively, retractors may interfere with cardiac filling andventilatory management so that hypotension, hypoxemia, and hypercarbia occur.Complications include inadvertent ligation of the left pulmonary artery ordescending aorta, recurrent laryngeal nerve damage, and excessive bleeding dueto inadvertent PDA disruption. After ductal ligation in premature infants, worseningpulmonary compliance can precipitate a need for increased ventilatory support,

and manifestations of an acute increase in LV afterload should be anticipated,especially if LV dysfunction has developed preoperatively. More recently, PDAligation has been performed in infants and children using thoracoscopic surgicaltechniques. This approach has the advantage of limited incisions at thoracoscopicsites, promoting less postoperative pain and discharge from the hospital the sameday of surgery.

Coarctation of the aorta is a narrowing of the descending aorta near the insertionof the ductus arteriosus. Obstruction to aortic flow is the result and this may rangefrom severe obstruction with compromised distal systemic perfusion to mild upper

extremity hypertension as the only manifestation. Associated anomalies of boththe mitral and aortic valves can occur. In the neonate with severe coarctation,systemic perfusion is dependent on right-to-left shunting across the PDA. In thesecircumstances, LV dysfunction is very common and prostaglandin E1 is necessaryto preserve sufficient systemic perfusion. Generally, a peripheral intravenous lineand an indwelling arterial catheter, preferably in the right arm, are recommendedfor intraoperative and postoperative management. In patients with LV dysfunction,


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a central venous catheter may be desirable for pressure monitoring and inotropicsupport. The surgical approach is through a left thoracotomy, whereby the aorta iscross-clamped and the coarctation repaired with an onlay prosthetic patch, asubclavian artery flap, or resection of the coarctation with an end-to-endanastomosis. During cross-clamp, we usually allow significant proximalhypertension (20 –25% increase over baseline), based on evidence that

vasodilator therapy may jeopardize distal perfusion and promote spinal cordischemia. 253

Intravascular volume loading with 10 to 20 mL/kg of crystalloid isgiven just before removal of the clamp. The anesthetic concentration isdecreased, and additional blood volume support is given until the blood pressurerises. Post-repair rebound hypertension due to heightened baroreceptor reactivityis common and often requires medical therapy. After cross-clamp, aortic wallstress due to systemic hypertension is most effectively lowered by institution ofbeta blockade with esmolol or alpha/beta-blockade with labetalol.

254 Propranolol

is useful in older patients but can cause severe bradycardia in infants and youngchildren. Although it actually increases calculated aortic wall stress in the absenceof beta blockade by accelerating dP/dT, the addition of sodium nitroprusside maybecome necessary to control refractory hypertension. Captopril or an alternativeantihypertensive regimen is begun in the convalescent stage of recovery in thosepatients with persistent hypertension.

The management of infants undergoing placement of extracardiac shunts withoutcardiopulmonary bypass centers around goals similar to those of other shuntlesions: balancing pulmonary and systemic blood flow by altering PaCO2, PaO2,and ventilatory dynamics. Central shunts are usually performed through a mediansternotomy, while Blalock-Taussig shunts may be performed through athoracotomy or sternotomy. In patients in whom pulmonary blood flow is critically

low, partial cross-clamping of the pulmonary artery required for the distalanastomosis causes further reduction of pulmonary blood flow and desaturation,necessitating meticulous monitoring of pulse oximetry. Careful application of thecross-clamp to avoid pulmonary artery distortion will help maintain pulmonaryblood flow. Under circumstances in which severe desaturation and bradycardiaoccur with cross-clamping, CPB will be required for the procedure. Intraoperativecomplications include bleeding and severe systemic oxygen desaturation duringchest closure, usually indicating a change in the relationship of the intrathoraciccontents that results in distortion of the pulmonary arteries or kink in the shunt.Pulmonary edema may develop in the early postoperative period in response to

the acute volume overload that accompanies the creation of a large surgicalshunt. Measures directed at increasing PVR, such as lowering inspired O2 toroom air, allowing the PaCO2 to rise, and adding positive end-expiratory pressureare helpful maneuvers to decrease pulmonary blood flow until the pulmonarycirculation can adjust. Decongestive therapy such as diuretics and digoxin mayalleviate the manifestations of congestive heart failure. Under suchcircumstances, early extubation is inadvisable.

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Pulmonary artery banding is used to restrict pulmonary blood flow in infantswhose defects are deemed uncorrectable for either anatomic or physiologicreasons. These patients are generally in congestive heart failure with reducedsystemic perfusion and excessive pulmonary blood flow. The surgeon places arestrictive band around the main pulmonary artery to reduce pulmonary bloodflow. Band placement is very imprecise and requires careful assistance from the

anesthesia team to accomplish successfully. Many approaches have beensuggested. We place the patient on 21 percent inspired oxygen concentration andmaintain the PaCO2 at 40 mm Hg, to simulate the postoperative state. Dependingon the malformation, a pulmonary artery band is tightened to achievehemodynamic (e.g., distal pulmonary artery pressure 50 –25% systemic pressure)or physiologic (e.g., Qp:Qs approaching 1) goals. Should the attainment of theseobjectives produce unacceptable hypoxemia, the band is loosened.

Blalock-Hanlon atrial septectomy is now an uncommon procedure for enlarging anintra-atrial connection. This procedure is done by occluding caval flow andcreating an intra-atrial communication through the atrial septum. In patients withhypoplastic left heart syndrome with an intact atrial septum, this procedure is life-saving and must be performed within hours of birth. Balloon atrial septostomies(Rashkind procedure) and blade septectomies performed in the cardiaccatheterization laboratory have replaced surgical intervention, except when leftatrial size is very small or the atrial septum is thickened. Improved safety of CPBhas led to the virtual elimination of such intracardiac procedures using inflowocclusion. Surgical septectomies, because they are currently confined to the mostdifficult subset, are rarely performed without benefit of CPB.


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One more word: Blalock Taussig..


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Blalock-Taussig Shunt (BTS) Aris Sophocles,

Mark Twite

Risk

• Indicated for infants with congenital heart lesions resulting in either severely reducedpulm blood flow (PBF) (e.g., tetralogy of Fallot, pulm and tricuspid atresia) or as the

first stage of single ventricle palliation (e.g., hypoplastic left heart syndrome [HLHS])Perioperative Risks

• Fewer BT shunts are performed now compared to previous decades and operativemortality has fallen despite a higher percentage of pts with single ventriclephysiology

• Periop complications incl Horner's syndrome, chylothorax, phrenic nerve damageand acute arm ischemia with classic BTS.

Worry About

• BTS for decreased PBF keep PVR as low as possible (high FIO2, avoid hypercarbia

and acidosis)

• BTS for single ventricle staged palliation essential to balance SVR and PVR (oftenrequires FIO2 0.17 - 0.21 and normocarbia)

Overview

• One of multiple types of systemic to pulm shunts to increased PBF

• Familiarity with underlying anatomy and physiology is essential to …

Preoperative Preparation

• Pts often already intubated, consider placing a nasal ETT for infants under 12 mo(tube more stable and makes placement of TEE probe easier)

• Arterial line: For cardiac lesions with ↓ PBF place A-line in contralateral radial arteryfrom BTS or in the femoral artery. For single ventricle lesions place an A-line in rightradial artery if low flow cerebral perfusion technique to be used for Stage 1 Norwoodand/or in the umbilical or femoral artery.

• Central venous line: All cases for inotropes. Consider co-oximetry central venouscatheter.

Intraoperative Period

• May use inhalation induction. Single ventricle pts often have IV access.

• Infants with tetralogy of Fallot may have tet spells due to worsening RVOTobstruction.

• Lateral thoracotomy classic approach: Anticipate worsened hypoxia with PAclamping, blood product transfusion usually not required

• Sternotomy and CPB for complex and single …

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