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\begin{document}

\title{Repeated cardiac arrests in a child due to severe aortic flow
obstruction by Aortic cannula: A fatal complication}



\author[1]{Vishnu Datt}%
\author[1]{Suman Keshav}%
\author[1]{Rachna Wadhwa}%
\author[1]{Sayyed Naqvi}%
\author[1]{Saket Agarwal}%
\author[1]{* Nikhil}%
\affil[1]{Govind Ballabh Pant Hospital}%


\vspace{-1em}



  
  \date{May 19, 2024}


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\selectlanguage{english}
\begin{abstract}
In neonates and children the blood vessels are small in calibre and the
correct choice of arterial and venous cannulas together with accurate
placement are crucial to avoid obstructing vascular branches,and
misdirecting flow or impairing venous drainage.Normally in children, to
establish the cardiopulmonary bypass (CPB)one arterial cannula is
inserted inthe ascending aorta,and single stagevenous cannulae, where
two cannulae inserted into the superior and inferior vena cava and
joined by the Y-pieceare used in the most open-heartsurgeries to
facilitate the circulatory, respiratory support along with the
temperature management. Rarely aortic cannulation can lead to aortic
dissection, aortic posterior wall rupture leading to trauma to the
esophagus, dislodgement of the aortic atheroma, fatal bleeding leading
even to cardiac arrest. In addition, SVC and IVC syndrome can also occur
due displacement or obstruction by the venous cannulae. However,
repeated cardiac arrestsin childrenafter successful weaning from
CPB,even with the use of an appropriate size aortic cannula has not been
reported in the literature to date. We wish to discuss this fatal
complicationafter weaning from CPB, due to aortic flow obstruction due
to aortic cannula in a one-year-old, 5.5 kg child following
successfulventricular septal defect(VSD) repair. The international
review board approval or waiver and clinical trial registrations are not
applicable for this case report publication%
\end{abstract}%



\sloppy


\textbf{Introduction:}

CPB circuits are frequently necessary in the repair of congenital heart
defects in neonates and children.Single stage cannulae are used during
most open-heart surgeries, where two Cannulae are inserted in SVCand IVC
and connected by Y-piece to establish CPB to divert the deoxygenated
venous blood to the heart-lung machine for oxygenation and then back via
the arterial cannula intothe ascending aorta. Displacement of the venous
cannulae can obstruct venous blood flow andmay result with SVC and IVC
syndrome. {[}1{]}Conversely, the aortic cannulation can cause
complications like aortic dissection, aortic rupture, profuse
bleeding,and dislodgement of aortic atheroma resulting in systemic
embolization.{[}2{]}we report a rarer consequence of aortic cannulation
asa severe aortic blood flow obstructionresulting in repeated cardiac
arrests in a child after successful VSDrepair under CPB.

\textbf{Key words} : congenital heart disease, CPB, aortic cannulation,
aortic obstruction, cardiac arrest, TEE

\textbf{Case report:}

A one -year- old, 5.5 Kg,with a BSA of 0.33 m2,male child presented
withhurried breathing since birth, and recurrentupper respiratorytract
infection and easy fatiguability with decreased activity since three
months of age.There was no history of cyanotic spells. On auscultation,
a pansystolic murmur was present at the left fourth intercostal space.
Chest X- ray showed pulmonary artery enlargement, cardiomegaly and
increased pulmonary vascularity. Echocardiography revealed a large
doubly committed VSD of 8.8 mm with moderate PAH,dilated RA,RV, and
pulmonary artery(2.6 cm), and normal biventricular functions with LVEF
of 60\%, and TAPSE of 21mm.He was puton oraldigitalis, enalapril,
sildenafil and furosemide,and after obtaining informed consent from the
parents, he was taken up forVSD patchclosure under cardiopulmonary
bypass (CPB).He was premedicated with oral midazolam(3mg) two hours
before surgery. In OR, standard ASAmonitoring was started. His baseline
heart rate was 140 bpm and arterial saturation was 99\%. General
anaesthesia was induced with fentanyl (50mc), thiopentone sodium (5mg),
midazolam( 0.5mg), and vecuronium bromide(1mg) was used to facilitate
the endotracheal intubation with 4.5 mm cuff tube.After
inductionofanaesthesia, 20GLeadercath was inserted in the left femoral
artery for continuous BP monitoring and intermittent ABG analysis. A 4.5
Fr triple lumen catheter was inserted via right internal jugular vein
for CVP monitoring and administration of anaesthetic drugs and
inodilators.His baseline BP and CVP were 85/ 50mmHgand 6
mmHgrespectively, and ABG revealed a pH 7.40, PO2-176 mmHg,PCO2 -35mmhg,
Hb-11gm\%, HCO3- 25mmol/l, SaO2- 99.8\%. Anaesthesia was maintained with
intermittent fentanyl, midazolam, vecuronium bromide, and
sevoflurane(1-2\%) and oxygen in air with fraction of inspired oxygen
(FiO2) of 0.5--1.Anticoagulation with heparin(300U/kg)was used to
achieve an ACT of \textgreater{}480 Sec. Aortic cannulation was done
using 12 Fr straight Styletted cannula (Medtronic), Venous drainage was
done using single stage 14 Fr angled DLP cannula for SVC and 16 Fr
angled DLP cannula for IVC. VSD was closed with Gore- Texpatch under
standard moderate hypothermic CPB, and potassium enriched
(Den-Lido)cardiopegic myocardial protection.Weaning from CPB was easy
with the use of infusion of milrinone (0.5mc/kg/min), dobutamine(5
mc/kg/min) and NTG (1mc/kg/min). On direct needle insertion, PA
pressures were 22/7(10) mmHg,at cardioplegia line was 70/ 40 mmHgand
atside port of the aortic cannula were 35/18mmHg, as compared to femoral
artery pressure of 30/17 mmHg. However, on visual assessment, the LV
contractility deteriorated and progressed to distension and cardiac
arrest andnecessitatedtoreinstitute CPB. Patient had similar repeated
three episodes of cardiac arrest on each successful weaning from CPB,
and LV contractility and hemodynamicscould not be maintained even with
the use of very high doses of inotropes.But we noted an unusual BP
difference at proximal to aortic cannulationmeasured by direct needle
insertion (90/ 40 mmHg)and femoral artery(30/17mmHg). Therefore, it was
decided to insert the TEE probe to rule out coarctation of aorta and
other cardiac anomalies, and to assess the VSD patch closure and
hemodynamics.TEE confirmedadequate VSD closure, and absence of
Coartation of aorta and any other cardiac anomalies, andgood LV
contractilitywhile patient was on CPB support.Therefore, one more
attempt for weaning off CPB was made under the TEE guidance.However,
still there was a big difference between FA pressure and aortic pressure
proximal to cannulation. Once again, the LVgot distendedand became
almost akinetic. Consequently,the patientalso developed severe mitral
regurgitation with 2-3 MR jets and hemodynamic deterioration. {[}Fig.1,
Video 1{]}Finally in a desperate scenario, it was decided to remove the
aortic cannula even in severehemodynamic instability (BP 31/17 mmHg),
realizing that the aortic cannula might be the culpritfor
thedeterioration of the LV function by obstructing the aortic blood
flow.Following aortic decannulation, the LV contractility and
hemodynamicsimproved gradually and maintainedevenwith minimum infusion
of dobutamine, milrinone. {[}Fig. 2, Video.2{]} {[}Fig.3, video. 3a,
3b{]}Utmost important to mention here that the similar sudden fall in
blood pressure was also noted following aortic cannulation, however,
that was managed as usual byvolume administration through aortic cannula
andpromptlyinstitution of CPB.Heparin was neutralized with
protamine(1:1.3 ratio). Total CPBtimes were188min, 15min,22min, 40 min,
and ischemia time was 140 min. Chest was closed after achieving proper
haemostasis.His Blood pressureand CVP before shifting to ICU were 90/45
mmHg and 7 mmHgrespectively, and ABG showed a Ph-7.47, HB- 8.8 gm\%,
PCO2- 27, PaO2-244 mmHg, and SaO2- 99\%.Tracheal extubation was done on
2\textsuperscript{nd} postoperative dayandinodilatorstapered slowly.
Post -extubation, child was fully alert without any neurocognitive
dysfunctions. Rest of the course was uneventful, and patient was
discharged on 10\textsuperscript{th} postoperative day.

\textbf{Discussion:}

CPB is a standard procedure in paediatric cardiac surgery.{[}3{]}The
general principles of CPB are same for neonates and adults. It requires
aortic and bicaval cannulations, andsome modifications are necessary to
accommodate the multiple anatomical variations that may be encountered
in congenital defects i.e. two aortic and three cava cannulas in
associated interrupted aortic arch and a persistent left superior vena
cava (LSVC) for adequate drainage during the CPB.{[}4{]} The aortic
cannulation is primarily done at the distal ascending aorta, positioning
the cannula close to the origin of the brachiocephalic trunk.{[}5{]}The
appropriate arterial cannula size depends upon the required CPB flow,
calculated using the formula ;CPB blood flow rate (litre/~min)=Body
surface area (BSA)(m2)\selectlanguage{ngerman}×Cardiac index (CI),(L~m\selectlanguage{english}-2/min). Flows of 1.8 to
2.5 L/min/m\textsuperscript{2}~are commonly used for infants, children,
and adults during mildtomoderate systemic hypothermia.The pump flow for
this patient was calculated as Weight in KG x 150 ml/min= 750ml/min and
accordinglyrecommended aortic cannula of 12 Fr for 700 ml -- 1000 ml
flow was used.If a cannula is too large, it can obstruct native heart
output, particularly in the ascending aortic position as this output is
critical during cannulation and the initiation and weaning phases of
bypass, also too large of a cannula may require an aortotomy that is
difficult to close in a standard fashion.~Therefore, aortic cannula size
should be selected in conjunction with the perfusionist team to utilize
the appropriate cannula for adequate flow during CPB.Table below shows
general sizes of cannulas used for initiating CPB.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

An arterial cannula that is too small, in addition to limiting flow,can
causehigh pressuresgradient, cavitation, increased jet of flow
velocities, jetting against the arterial wall and can increase the
likelihood of dissection, and high shear forces which may damage the
formed elements of the blood. However, diffusion-tip cannulas are
available which provide multidirectional flow to reduce jets.{[}5{]}The
tip of the cannula may be straight, tapered, or angled, as well as made
from metal or plastic. Various tip modifications, such as flanges or
adjustable rings, are available to prevent the cannula from being
inserted too far into the aorta and impeding flow to the head
vessels.{[}6{]} The inappropriately aortic cannulation can be associated
with complications like bleeding, aortic dissection, malposition of
cannula tip, atheroma dislodgement causing systemic embolism, accidental
decannulation, aortic posterior wall puncture causing fatal bleeding and
esophagealdamage. {[}7,8{]}

Our patient developed repeated LV distensions and cardiac arrests, even
after repeated successful weaning from the CPB. Trans
-esophagealechocardiography (TEE) was used to confirm any unnoticed
congenital anomalies like PDA, ASD, coartation of the aorta, extra VSD,
and VSD patch closure. After exclusion of the other possible causes of
LV dysfunction and cardiac arrest,finally we reached to the decision
that the repeated episodes of cardiac arrests were related tothe rarer
complication i.e. the aortic blood flow obstruction by the use of large
aortic cannula. The LV dysfunction and cardiac arrests were even
refractory to the very high doses of inotropes, inodilators and standard
CPR, but at last LV dysfunctions and hemodynamic graduallyimproved only
after aortic decannulation. This complication of aortic cannulation has
been hypothesized but not reported in the existing literature till date.

\textbf{Conclusion:}

Aortic Cannula size should be selected in conjunction with the
perfusionist team to utilize the appropriate cannula for adequate flow
during CPB. It is imperative to finally decide the aortic cannula size
after observing the ascending aorta size after opening the chest. Use of
an inappropriately large aortic cannula particularly in neonates and
children can obstruct the aortic blood flow before and after CPB and
patient may develop refractory LV distension and cardiac arrest.

\textbf{Financial support and sponsorship}

Nil.

\textbf{Conflicts of interest}

There are no conflicts of interest.

\textbf{References:}

\begin{enumerate}
\tightlist
\item
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\item
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\item
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\item
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\item
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\end{enumerate}\selectlanguage{english}
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\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Fig/Fig}

\end{center}
\end{figure}\selectlanguage{english}
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\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Figure-2/Figure-2}

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