Facing the concerns of BT shunt management from admission to discharge - optimising open heart surgery, anesthesia and ICU care.

How often a case has been thrown at us and we all get the jitters.

So, What do we need to do to give the best surgical result to the ICU team?

 Cardiac surgery is all about avoiding adverse events, and that starts right from case selection, Timing of intervention, Method of intervention, Anesthesia, Techniques of surgery and Choices made during ICU intervention

Need a Shunt ?

We should remember that

·     This is because of Decreased pulmonary blood flow and the child is hypoxic, needing a procedure to increase pulmonary blood flow.

·     Pulmonary perfusion depends on several factors that need to be taken care of until the definitive surgery addresses the condition.

·     Reduced oxygen reserve = Cerebral hypoxia risk.

·     There is a defect in the heart ~ Infection risk

·     There is a right to left shunt ~ Embolism risk

What are our Options to increase PBF

·     Stenting the PDA/MAPCAS

·     Balloon dilatation of the PS

·     RVOT stenting

·     Full correction

·     TAP without closing the VSD

·     BTT shunt +/- MAPCA unifocalisation

·     BDGS

 Anesthesia Critical points to be aware of

·     Well Sedated children do not have cyanotic spells, keep them comfortable.

·     De-air all lines to prevent paradoxical embolism to the coronaries or the brain.  

·     Maintain hydration to prevent hypotension or thrombosis, especially in hot cities.

·     Baseline SpO2

·     ECG - ST segment to be noted consciously

·     Baseline ABG on room air

·     ABG on 100 % FiO2

·     Bilateral air entry, no added sounds.

·     Adrenaline infusion connected and ready with all emergency drugs loaded.

·     Stable SpO2  >75% is sufficient for surgery without CPB.

 Guidelines for anesthesia

·     For TOF maintain low heart rate, this increases antegrade flow to the lungs.

·     For pulmonary atresia – maintain high blood pressure, as the lungs are being perfused by MAPCAS

·     ET CO2 will be low due to reduced PBF, nothing we can do about it now.

What are the common Indications for a BT shunt

·     TOF with reduced antegrade flow

·     TOF with pulmonary atresia

·     SV physiology with reduced pulmonary flow

·     D malposed great arteries with reduced PBF

·     As part of a Norwood operation

·     Rarely for LV training in DTGA IVS.

Which approach do I prefer for the surgery.

Sternotomy with or without CPB

Thoracotomy – choice of side – left or right?

When we do a sternotomy, it is for a

·     Small child < 3 Kg.

·     Small branch PA’s less than 3.5 mm - MPA

·     Oxygen saturation below 75% on ventilator with 100% FiO2.

·     In an unstable patient.

·     When needing bifurcation plasty of the pulmonary areteries.

·     If you feel the need to do the shunt on CPB.

we do a Thoracotomy when

·     Branch PA’s more than 3.5 mm

·     Oxygen saturation above 75% on ventilator with 100% FiO2.

·     In a stable patient.

·     When there is no bifurcation/branch origin stenosis.

·     Which side do we choose

·     The side of the smaller PA - if it is >3.5 mm.

·     The left side, if we are planning to ligate a small PDA or planning a Right BDGS later, easier to do as well.

·     The right side enables easier takedown of the shunt during the second stage.

·     The side of the arch (left) or bigger lung (right sided)

 Concerns we have about sternotomy for shunts

·     The second operation is then challenging as all structures in the chest get stuck together and that is called a  re-do operation.

·     These Adhesions obscure the coronaries and may result in injury.

·     CPB becomes essential for a re-do sternotomy, at least as a standby.

Concerns raised - Thoracotomy

·     Scoliosis can be prevented by meticulous closure of the muscles in separate layers.

·     Post op Pain – not proven in our experience especially with early mobilization.

·     Though considered Difficult, the short learning curve is evident once trained by the right team.

·     SCA (the Proximal) anastomosis may be distally placed

·     With patience, Distal anastomosis can be placed to central Pas (intra pericardial).

·     No support of CPB – we rely on robust selection criteria and a reliable anesthetist.

Complication to be avoided

1. Chylothorax,

Coagulate any tissue before cutting it.

Do not dissect excessively around the Subclavian artery.

2. Horner’s syndrome,

Identify The Ansa Subclavia that lies close to the LSCA and avoid Horner’s syndrome.

3. The recurrent laryngeal nerve supplies the vocal cords and can be easily identified.

It is a branch of the vagus and helps in locating an abnormal PDA.

4. Phrenic nerve palsy

The phrenic nerve is in Phront of the hilum on the SVC.

The vagus is Vehind to the hilum.

Advantages of Thoracotomy

·     Easy to learn

·     Dissection of SCA is easy

·     Minimal heparinisation – less bleeding, early heparin.

·     Function of pericardium is retained

·     No adhesions during re-do surgery

·     Early extubation is possible.

·     Wound infection is less troublesome.

 How to choose the size of the graft

our experience

·     <1 Month of age, if the branch PA is < 3.5 mm, 3.5 mm graft will work fine. Done through a Sternotomy.

·     For 1M -1Y, branch PA Between 3.5 mm and 5 mm, 4 mm graft will be suitable.

·     Above 1 year/ 10 Kg/ 2 ventricle repair – 5 mm shunt becomes appropriate.

·     Adult cases (only 4 cases out of 14 years) used a 6 mm or greater graft. BDGS if possible

 Where to place the distal anastomosis

·     Situs of the lung will tell us where the PA is located.

·     The PA is dissected with as much adventitia as possible on its surface.

·     MIPCAS are coagulated before heparin.

·     Where the branch PA divides, we take stay sutures on the adventitia, to put traction on it and enable dissection far into the pericardium but without opening the pericardium.

·     Adequate length of PA will enable comfortable placement of the side-biter and shunt proximal to the bifurcation.

Steps:

·     Heparin 1-2 mg per kg,

·     Wait 3 min

·     Check with team for readiness, esp anesthesia.

·     Clamp on SCA. Fix the clamp with vessel loops

·     Incision with sharpest 11 blade!

·     Take stays, then cut open with Potts.

·     Anastomosis from heel to toe 7/0 round body, 6/0 13 mm

·     Thin bites on graft.

·     Same for PA anastomosis

 How to control the flow in the graft

·     Flow depends on the size of the graft (D) R4

·     Length

·     Pressure difference – MAP and PAP ( PVR & SVR)

·     Viscosity

·     Feeding vessel, run off, competition

·     Ventilation strategy

·     Inotropes

 Bifurcation plasty

Can be done off pump, but not by the trainees.

Only through sternotomy,

How to prevent bleeding after shunt

·     Dissection should be absolutely dry with no charring - before heparin.

·     Choice of shunt – thick wall

·     Choice of suture – 7/0, 6mm for neonates with thin wall Pas

·     6/0, 13 mm for others

·     Thin bites on the shunt edge enables easy hemostasis - the adventitia of the PA.

·     Reduce Prolene and avoid adventitia within the lumen.

How to prevent thrombosis

·     Go one graft size bigger than essential for the shunt.

·     Heparinise before opening the arteries. Irrigate the graft and anastomosis with heparin saline.

·     Get perfect hemostasis with sutures, no protamine, no surgicel.

·     Do not reverse heparin.

·     Start a heparin infusion 10 IU per KG per hour for 48 hours to enable Aspirin to be started before discontinuing it.

·     Better to re-explore for bleeding than give protamine.

·     Avoid bolus diuretic. 2mg/kg/day Infusion in small children helps early extubation.

Intensive care management

·     Baseline investigations – ABG, Xray, ECG,

·     Monitor all vitals,

·     Start Frusemide infusion 1 mg/Kg/day

·     Wait for lack of bleeding and then start heparin infusion 10 i.u./kg/hour for 48 hours

·     Drop FiO2 as long as SpO2 is > 90 %

·     Inotropes to keep MAP adequate.

·     Extubate early.

How do you handle common ICU issues

Increased flow can cause a picture similar to low cardiac ouput.

Similarly, White out lung, Low Pressures and High CVP indicates low cardiac output needing optimization of Inotropes.

Low pO2 / high pCO2 is usually because of overflowing shunt or pulmonary edema.

Thrombosis can be prevented by good surgical technique and Heparin infusion.

Bleeding – reopen the chest and get control without Protamine.

 Come, let us show you how we have been doing it for the past 25 years.

 Helen Taussig & Alfred Blalock, guided by Vivien Thomas carried out the first operation on November 29, 1944 at Johns Hopkins Hospital in Baltimore, Maryland.