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Year : 2011  |  Volume : 14  |  Issue : 1  |  Page : 45-47
Utility of intra-operative capnogram to detect branch pulmonary artery obstruction following total correction of tetralogy of fallot

Department of cardiac anesthesia and cardiac surgery, Narayana Hrudayalaya Institute of Medical Sciences, Anekal Taluk, Bangalore, India

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Date of Submission12-Mar-2010
Date of Acceptance28-Aug-2010
Date of Web Publication31-Dec-2010


Branch pulmonary artery obstruction is one of the prime reasons for re-operation in patients who have undergone repair for tetralogy of Fallot. Branch pulmonary artery obstruction may develop over a period of time due to dilation of right ventricular outflow tract or it may be caused by residual stenosis after inadequate repair. This may lead to differential lung perfusion causing morbidity. Intra-operative capnogram monitoring reveals ventilation−perfusion relationship. We report two cases where the capnogram helped the diagnosis and management of branch pulmonary artery obstruction. We found a redundant patch in the first and an extra length of the homograft in second case which led to the obstruction. However, but for the changes in the intraoperative capnogram, this condition may by far remain undiagnosed considering the fact that it does not produce hemodynamic changes but can lead to postoperative morbidity.

Keywords: Capnogram, intraoperative, pulmonary artery, tetralogy of Fallot

How to cite this article:
Garg R, Murthy K, Rao S, John C. Utility of intra-operative capnogram to detect branch pulmonary artery obstruction following total correction of tetralogy of fallot. Ann Card Anaesth 2011;14:45-7

How to cite this URL:
Garg R, Murthy K, Rao S, John C. Utility of intra-operative capnogram to detect branch pulmonary artery obstruction following total correction of tetralogy of fallot. Ann Card Anaesth [serial online] 2011 [cited 2022 May 27];14:45-7. Available from:

   Introduction Top

Branch pulmonary arterial obstruction is not uncommon after surgical correction of tetralogy of Fallot (TOF). [1],[2],[3] It causes differential lung perfusion which may result in postoperative morbidity. Capnogram is a reflection of relationship between ventilation and perfusion. Any change in either of these will be reflected in capnogram. We report two such cases where capnogram helped detection of branch pulmonary artery obstruction.

   Case Report Top

Case 1

A 2-year-old child diagnosed to have TOF with confluent pulmonary arteries and left pulmonary artery (LPA) origin stenosis underwent total correction with trans-annular patch repair with extension of the patch to the LPA origin. After completing the intracardiac repair, the patient was weaned from cardiopulmonary bypass (CPB) with stable hemodynamics. It was observed that capnogram trace was showing varying plateau phase (C-D in [Figure 1]a), which suggested alveolar ventilation−perfusion abnormalities and differential lung perfusion. Intraoperative transesophageal echocardiography (TEE) was performed to assess the surgical repair which revealed intact ventricular septal defect patch, good right ventricular outflow tract (RVOT) without significant gradient across RVOT but there was turbulence at the origin of the LPA. Direct pressure measurements in the main pulmonary artery (MPA) and LPA revealed gradient of 20 mmHg between them. Patient was hemodynamically stable but the capnogram trace continued to show varying plateau phase. There was gradient of 15−20 mmHg between partial pressure of carbon dioxide in arterial blood and end tidal carbon dioxide (PaCO 2−ETCO 2 ). We transferred the patient for angiogram. Angiogram revealed good flow in right pulmonary artery (RPA) and sluggish flow in the LPA [Figure 2]. The patient was reoperated and RVOT patch was revised. In the operating room, to ascertain the site of kink at LPA origin, trans-annular patch was retracted caudad to see the LPA origin. At this point, the plateau phase in the capnogram trace became normal [Figure 1]b and it remained normal till the patch was kept retracted and it turned abnormal on releasing the patch. It was realized that there was an extra length of the trans-annular patch which was redundant and causing the kink at LPA origin. Under CPB, patch was shortened. There were no problems after this. The gradient between PaCO 2−ETCO 2 came down to a normal range of 5−10 mmHg. We reassessed the surgical repair using TEE and found no turbulence at LPA origin. Direct pressure measurement revealed no gradient between MPA and LPA. The patient was transferred to the postoperative intensive care unit (ICU) with stable hemodynamics.
Figure 1 :Capnogram (a) showing varying plateau phase (C−D) of expiration which is a reflection of differential alveolar perfusion (b) normal capnogram

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Figure 2 :Postoperative angiogram showing good flow in the RPA and scanty flow in the LPA

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Case 2

A 4-year-old child with TOF and pulmonary atresia underwent total correction and right ventricle to pulmonary artery valved homograft conduit repair under CPB. Patient was weaned from CPB with reasonable hemodynamics but capnogram trace revealed waveforms similar to that observed in the first case report. TEE was performed to assess the adequacy of the surgical repair; it revealed intact VSD patch, absence of turbulence at the take off point of conduit from right ventricle with good antegrade flow. However, there was turbulence at the distal anastomotic point where the conduit was anastomosed to the pulmonary artery. Keeping in mind the experience from earlier case, the homograft was shortened. There were no problems after this.

   Discussion Top

Capnography trace helps in detecting changes in ventilation and perfusion during different phases of ventilation. It may be an important tool to diagnose abnormalities in ventilation during inspiration, expiration and alveolar phase of ventilation as well as its correlation with ventilation.

One of the mechanism [4] of LPA kinking and obstruction after TOF repair is that the pulmonary regurgitation and right ventricular dilatation after trans-annular patch repair results in dilatation and elongation of pulmonary outflow tract which moves towards the cranial dirction and rotates to the left resulting in kinking of LPA. Although LPA obstruction may be of little hemodynamic significance in immediate postoperative period, it is one of the most frequent indications for reoperation in patients undergoing early TOF repair. In both the cases, shortening of the patch or homograft helped relieving the kink; it is the standard approach in patients undergoing reoperation for branch pulmonary artery obstruction. [4]

This phenomenon described above is observed only in patients who are cyanotic and have decreased pulmonary blood flow preoperatively. These patients are known to have ventilation perfusion mismatch because of low pulmonary blood flow. After the surgery when pulmonary blood flow is increased but the increase is more in one lung due to obstruction in the other, there is differential washout of CO 2 , which manifests as varying ETCO 2 in capnogram. Both the cases reported here demonstrate the role of capnogram in diagnosing differential lung perfusion which can be investigated to find out the cause.

   Summary Top

Capnogram is an important monitoring tool which can detect differential lung perfusion. [5]

   References Top

1.Hennein HA, Mosca RS, Urcelay G, Crowley DC, Bove EL. Intermediate results after complete repair of tetralogy of Fallot in neonates. J Thorac Cardiovasc Surg 1995;109:332-44.  Back to cited text no. 1
2.Uretzky G, Puga FJ, Danielson GK, Hagler DJ, McGoon DC. Reoperation after correction of tetralogy of Fallot. Circulation 1982;66:202-8.  Back to cited text no. 2
3.Zhao HX, Miller DC, Reitz BA, Shumway NE. Surgical repair of tetralogy of Fallot: Long-term follow-up with particular emphasis on late death and reoperation. J Thorac Cardiovasc Surg 1985;89:204-20.   Back to cited text no. 3
4.McElhinney DB, Parry AJ, Reddy VM, Hanley FL, Stanger P. Left pulmonary artery kinking caused by outflow tract dilatation after transannular patch repair of tetralogy of Fallot. Ann Thorac Surg 1998;65:1120-6.  Back to cited text no. 4
5.Shankar KB, Russell R, Aklog L, Mushlin PS. Dual capnography facilitates detection of a critical perfusion defect in an individual lung. Anesthesiology 1999;90:302-4.  Back to cited text no. 5

Correspondence Address:
Rajnish Garg
Narayana Hrudayalaya Institute of Medical Sciences, 258/A, Bommasandra Industrial Area, Anekal Taluk, Bangalore 560 099
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0971-9784.74399

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  [Figure 1], [Figure 2]


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