Obese patients undergoing cardiac surgery have been shown to have a high risk of developing postoperative complications, specifically: increased length of hospital stay, readmission to intensive care unit, acute renal failure, deep sternal wound infections and new onset of atrial fibrillation

A Parolari

Anna Winfield

C-H Yap

E De Stefano

Federico Bizzarri

GJ Myers

GS Murphy

H Edmunds

KG Shann

M Ranucci

N Curtis

N Sohn

Patrizio Sartini

R Issit

S Perrotta

SB Scinde

Y Durandy

English

PubMed

Abstract Obese patients undergoing cardiac surgery have been shown to have a high risk of developing postoperative complications, specifically: increased length of hospital stay, readmission to intensive care unit, acute renal failure, deep sternal wound infections and new onset of atrial fibrillation. A custom-made circuit was created to allow the use of Mini Extra Corporeal Circulation (MECC) but permitting the switch to a closed siphon drainage system in the case of difficulties. To limit artificial surface contact a small oxygenating device (Admiral, Eurosets) was employed in spite of the patients size. This adapted circuit permits a feasible and safer approach to using MECC. This report suggests that smaller oxygenators could be integrated into clinical practice in an adult MECC configuration, even for more obese patients, limiting artificial surface contact.</p

Sartini Patrizio

Winfield Anna

Bizzarri Federico

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Journal of Cardiothoracic Surgery

The successful introduction of an adapted form of the mini extra corporeal circulation used for cardiac surgery in an obese patient

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CASE REPORT Open Access
The successful introduction of an adapted form
of the mini extra corporeal circulation used for
cardiac surgery in an obese patient
Patrizio Sartini1, Anna Winfield2 and Federico Bizzarri1,2*
Abstract
Obese patients undergoing cardiac surgery have been shown to have a high risk of developing postoperative
complications, specifically: increased length of hospital stay, readmission to intensive care unit, acute renal failure,
deep sternal wound infections and new onset of atrial fibrillation.
A custom-made circuit was created to allow the use of Mini Extra Corporeal Circulation (MECC) but permitting the
switch to a closed siphon drainage system in the case of difficulties.
To limit artificial surface contact a small oxygenating device (Admiral, Eurosets) was employed in spite of the
patients size. This adapted circuit permits a feasible and safer approach to using MECC. This report suggests that
smaller oxygenators could be integrated into clinical practice in an adult MECC configuration, even for more obese
patients, limiting artificial surface contact.
Keywords: Cardiopulmonary bypass, Obese patients, Aortic valve replacement, Mini extra corporeal circulation
Background
Obese patients undergoing cardiac surgery have an
increased risk of developing specific postoperative compli-
cations. Obesity (defined as BMI > 30) is associated with
prolonged mechanical ventilation, readmission to intensive
care unit, increased rates of deep sternal wound infection
and a length of stay greater than 14 days. Both obesity and
morbid obesity, especially when other risk factors such as
diabetes mellitus and hypertension are present, may
increase the rate of onset of acute renal failure. Neverthe-
less, an increased BMI does not increase the risk of early
postoperative death or the risk of postoperative cerebro-
vascular accidents and the rates of postoperative bleeding
in obese patients are significantly lower [1]. The profile of
patients undergoing cardiac surgery has changed in recent
times, as rates of obesity increase, the proportion of obese
patients requiring cardiac surgery has increased also.
The aim of this article is to propose a progressive
approach to MECC, demonstrating its successful use in
an obese patient.
Case presentation
A 73 year-old man was admitted to our unit with severe
aortic stenosis requiring aortic valve replacement. The
patient had numerous risk factors for cardiovascular dis-
ease including obesity (BMI = 40; BSA = 2,46), hypercho-
lesterolemia, hypertriglyceridemia, Type II Diabetes
Mellitus and being a cigarette smoker. The procedure was
performed through a J-shaped mini-sternotomy [2] with
routine ascending aorta and right atrial cannulation. After
opening the aorta, we carefully removed all the debris on
the valvular annulus that extended to the mitro-aortic
junction. A tissue valve was then implanted. The operation
was completed routinely and without incident. The patient
was discharged from the Intensive Care Unit on post-
operative day two. There were no major complications.
Method
Cardio Pulmonary Bypass (CPB) was performed using a
closed custom-made circuit designed to perform Mini-
extracorporeal circulation (MECC). The circuit was
* Correspondence: federico.bizzarri@uniroma1.it
1Department of Medical Surgical Sciences and Biotechnologies, Cardiac
Surgery Unit, Polo Pontino, Universita’ degli Studi di Roma “Sapienza”, Latina,
Italy
Full list of author information is available at the end of the article
Sartini et al. Journal of Cardiothoracic Surgery 2012, 7:20
http://www.cardiothoracicsurgery.org/content/7/1/20
© 2012 Sartini et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
designed such that the system could switch to a conven-
tional closed siphon drainage system if necessary.
A schematic description of our circuit can be seen in
Figure 1. The circuit consisted of a 1/2 inch venous line
(compatible for siphon drainage) and 3/8 inch arterial
line, a collapsible bag was interposed in the venous line
and was connected to it by two 3/8 inch short pipes, the
1/2 inch venous line then met a centrifugal pump (Bio-
pump Medtronic). After the venous section there was the
oxygenator (Eurosets, Mirandola, Italy), the arterial filter
and the final 3/8 inch segment of the arterial pipe.
This dual purpose circuit employed a 1/2 inch venous
pipe longer than the ones usually used in MECC and the
same pipe was selected for use as the venous cannula sui-
table for siphon drainage (24 fr Aortic cannula; 44/36 fr
right atrium cannula. DLP® Medtronic, Inc.). To minimise
artificial surface contact and improve biocompatibility we
employed the Admiral® oxygenator (Eurosets, Mirandola,
Italy), which had the smallest available membrane and
phosphorylcoline treatment of the lines and oxygenator. It
is an integrated microporous hollow-fibre oxygenator,
with a total membrane surface area of 1.35 m2, a heat
exchanger surface area of 0,08 m2 and a low prime volume
(190 ml) [3]. The oxygenator and the circuit had a superfi-
cial phosphorylcoline (Pc) coating. This coating is reported
to provide some protection against blood clot activation
[4]. The circuit was placed under the operating table to
obtain a drainage pressure of approximately -25, mmHg.
A pressure transducer monitored the negative pressure in
venous line. Retrograde Autologous Priming (RAP) was
employed to limit haemodilution [5].
Buckberg cardioplegic solution was delivered directly
into the coronary ostia and into the coronary sinus dur-
ing aortotomy. Mild hypothermia was induced. An auto-
transfusion device (Electa, Soring Group, Italy) was used
to collect, wash and store shed red blood cells, the
remaining circuit perfusate was also treated by Electra
and autologous red cell transfusion was initiated in the
post-operative period [5]. Hyperglycaemia was managed
according to the modified Portland protocol.
Oxygenator performance was evaluated by monitoring
of serial arterial blood gas measurments (pO2 150-200
mmHg). Adequacy of perfusion was monitored by Oxygen
Delivery (DO2), lactate production and the ratio between
the oxygen delivery and carbon dioxide production (DO2/
VCO2). The DO2 formula can be calculated as follows:
[pump flow × (Hb × O2Sat × 1,36) + 0,003 × PaO2 ] [6].
Blood lactate monitoring is more appropriate for detecting
the correct matching of oxygen supply and demand during
CPB [7].
Carbon dioxide production (VCO2) was calculated as
follows: VCO2 indexed (mL × min -1 × m-2): eCO2
(mmHg) × Ve (L/min) × 1000/760 × BSA (m2). Exhaled
carbon dioxide from oxygenator (CO2) and gas flow into
the oxygenator (Ve) were simultaneously recorded at
each sampling aspiration.
Figure 1 Mecc Circuit.
Sartini et al. Journal of Cardiothoracic Surgery 2012, 7:20
http://www.cardiothoracicsurgery.org/content/7/1/20
Page 2 of 5
Conduct of perfusion
Tubing clamps were placed in both A and C 3/8 inch
pipes, starting from the venous bag. The centrifugal pump
velocity was previously set to overcome the patient’s sys-
temic blood pressure avoiding back flow. At the onset of
CPB the clamp in position A was partially opened obtain-
ing drainage from the patient into a venous bag. Once the
partial release of the “A segment clamp” permitted the
venous drainage, the blood collected in the collapsible bag
began to flow from the centrifugal pump and gradually
increased with further release of the “A clamp segment”.
With this clamp configuration siphon drainage was
obtained as it occurs in conventional closed system. In few
minutes full CPB was established. At this point, in order
to switch toward MECC, the “C segment clamp” was
released and subsequently the “A segment” was clamped.
At this moment there was a transient diminution of sys-
temic perfusion due to volume collection in the collapsible
bag but this was readily corrected with light occlusion of
the “C segment” until the collapsible bag emptied return-
ing perfusate, restoring circulating volume.
Once the circulating volume correction was performed
the desired flow was obtained using MECC conduction. In
this kinetic assisted drainage configuration with a closed
circuit the monitoring of central venous pressure (CVP)
was helpful in the maintenance of desired blood flow and
avoided over-distension of the right atrium. Excessive
negative pressure and venous line chattering was over-
come by partial clamping of the 1/2 inch venous line. The
negative pressure in 1/2 inch venous line was kept to
approximately -50 mmHg.
Discussion
MECC optimizes the extracorporeal circulation, thus
resulting in a reduction in the inflammatory reaction,
blood exposure and trauma [8]. The use of MECC as
demonstrated in this study could be incorporated into
daily practice without considerable difficulty at other cen-
tres [9] as this centre has done following the experience of
others.
The use of the venous bag included in the circuit per-
mits a rapid and safe switch from MECC to a closed con-
ventional extracorporeal circulation. The oxygenator
(Eurosets, Mirandola, Italy) performed satisfactorily
throughout the procedure despite the small oxygenating
surface [10]. To our knowledge this case represents the
patient with the largest body mass index to have been
treated with this small oxygenating device.
Adequacy of perfusion was monitored by Oxygen
Delivery (DO2) [Figure 2], lactate production [Figure 3]
and the ratio between the oxygen delivery and carbon
dioxide production (DO2/VCO2) [11,12] [Figure 4]. A
DO2/VCO2 ratio of < 5 is thought to be predictor of
hyperlactatemia and although not specific, an increase
or change in lactate level during Cardiopulmonary
bypass, may be a marker of regional hypoperfusion or
increased metabolic demand [13]. In our case we ran a
lower DO2 than suggested in previous studies. Ranucci
et al. fixed a critical value of 270 ml/min/m2 suggesting
that a lower value could induce a condition of circula-
tory shock [14,15]. In our patient a low DO2 value, well
matched carbon dioxide parameters showing a value
higher than 5 as result of the thermic strategy. Since the
procedure was not normothermic we choose to pump at
a lower Ht and trigger the transfusion point according
to the oxyphoretic needs.
The intra-operative [Figure 3] lactate production
remained within a normal range throughout the proce-
dure, providing reassurance about the adopted perfusion
strategy, which permitted a prudent transfusion policy.
Figure 2 Intra-Operative Oxygen Delivery: (DO2).
Sartini et al. Journal of Cardiothoracic Surgery 2012, 7:20
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Page 3 of 5
Figure 3 Intra-Operative Lactate Production.
Figure 4 Oxygen Delivery/Carbon Dioxide Production: (DO2/VCO2).
Figure 5 Post Operative Lactate Production.
Sartini et al. Journal of Cardiothoracic Surgery 2012, 7:20
http://www.cardiothoracicsurgery.org/content/7/1/20
Page 4 of 5
The lactate production monitored up to 18 hours post
operatively [Figure 5] followed a normal course.
Conclusion
With this simple circuit the surgical team can gain the
necessary confidence in MECC and experience can be
gained safely. The integration of a smaller oxygenator
than usual in a MECC circuit, could be a positive con-
tribution in the continuous effort to increase perfusion
optimization [16-19] and manufacturing companies
could consider this for their own commercial develop-
ment. The use of MECC in this way has been shown in
this case to be successful in the obese patient.
Consent
Written informed consent was obtained from the patient
for publication of this report and any accompanying
images.
Disclosure
The authors do not receive honoraria, consultation fees
or support from cited companies.
Author details
1Department of Medical Surgical Sciences and Biotechnologies, Cardiac
Surgery Unit, Polo Pontino, Universita’ degli Studi di Roma “Sapienza”, Latina,
Italy. 2Department of Cardiac Surgery, Yorkshire Heart Centre, Leeds General
Infirmary, Great George Street, LS1 7EH Leeds, UK.
Authors’ Contributions
PS and FB conceived the new circuit and AW participated in the design of
the study. All authors read and approved the final manuscript.
Competing Interests
The authors declare that they have no competing interests.
Received: 4 January 2012 Accepted: 9 March 2012
Published: 9 March 2012
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doi:10.1186/1749-8090-7-20
Cite this article as: Sartini et al.: The successful introduction of an
adapted form of the mini extra corporeal circulation used for cardiac
surgery in an obese patient. Journal of Cardiothoracic Surgery 2012 7:20.
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Abstract
          Obese patients undergoing cardiac surgery have been shown to have a high risk of developing postoperative complications, specifically: increased length of hospital stay, readmission to intensive care unit, acute renal failure, deep sternal wound infections and new onset of atrial fibrillation.
          A custom-made circuit was created to allow the use of Mini Extra Corporeal Circulation (MECC) but permitting the switch to a closed siphon drainage system in the case of difficulties.
          To limit artificial surface contact a small oxygenating device (Admiral, Eurosets) was employed in spite of the patients size. This adapted circuit permits a feasible and safer approach to using MECC. This report suggests that smaller oxygenators could be integrated into clinical practice in an adult MECC configuration, even for more obese patients, limiting artificial surface contact.</jats:p

Crossref

Obese patients undergoing cardiac surgery have been shown to have a high risk of developing postoperative complications, specifically: increased length of hospital stay, readmission to intensive care unit, acute renal failure, deep sternal wound infections and new onset of atrial fibrillation. A custom-made circuit was created to allow the use of Mini Extra Corporeal Circulation (MECC) but permitting the switch to a closed siphon drainage system in the case of difficulties. To limit artificial surface contact a small oxygenating device (Admiral, Eurosets) was employed in spite of the patients size. This adapted circuit permits a feasible and safer approach to using MECC. This report suggests that smaller oxygenators could be integrated into clinical practice in an adult MECC configuration, even for more obese patients, limiting artificial surface contact

BIZZARRI, Federico

Archivio della ricerca- Università di Roma La Sapienza

A: Oxygen delivery during cardiopulmonary bypass and acute renal failure after coronary operation. Ann Thorac Surg

Cardiopulmonary bypass and oxygen consumption: oxygen delivery and hemodynamics. Ann Thorac Surg

Clinical evaluation of the Admiral 1,35 m2 hollow-fibre membrane oxygenator. Perfusion

Effect of obesity on early morbidity following cardiac surgery. Heart Lung Circ

Giomarelli Pierpaolo: Anaerobic Metabolism During Cardiopulmonary Bypass: Predictive Value of Carbon Dioxide Derived Parameters. Ann Thorac Surg

Groom R: Optimal perfusion during cardiopulmonary bypass: an evidente-based approach. Anesth Analg

Inflammatory response to Cardiopulmonary Bypass. Ann Thorac Surg

Laurie: The impact of different biocompatible coated cardiopulmonary bypass circuits on inflammatory response and oxidative stress. Perfusion

Lowest hematocrit on cardiopulmonary bypass impairs the outcome in coronary surgery. Tex Heart Inst J

Mankad PS: Oxygen delivery and hemoglobing concentration in cardiac surgery: When do we have Enough? In Artif Organs. Volume 32.

Ministernotomy approach for surgery of the aortic root and ascending aorta. Interact Cardiovasc Thorac Surg

ND: Blood lactate levels during cardiopulmonary bypass. Ann Card Anaesth

Ohri SK: Mini extracorporeal circuit cardiopulmonary bypass system: a review. Perfusion

Perfusionist strategies for blood conservation in pediatric cardiac surgery.

The significance of Artero-Venous Carbon Dioxide Gradient. A Review of this Guide to the Adequacy of Peripheral Tissue Perfusion. Canadian Perfusion Canadienne

TW: An evidence-based review of the practice of cardiopulmonary bypass in adults: a focus on neurological injury, glicaemic control, haemodilution, and inflammatory response. J Thorac Cardiovasc Surg

Undar A: Evolution of the extracorporeal life support circuitry.

von Segesser LK: Initial clinical experience with the Admiral oxygenator combined with separated suction. Perfusion

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The successful introduction of an adapted form of the mini extra corporeal circulation used for cardiac surgery in an obese patient

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