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Eur J Cardiothorac Surg 2005;27:644-648
© 2005 Elsevier Science NL

Malposition of selective cerebral perfusion catheter is not a rare event

Division of Cardiovascular Surgery, Hiroshima University Hospital, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8551, Japan

Received 1 October 2004; received in revised form 23 December 2004; accepted 27 December 2004.

^* Corresponding author. Tel.: +81 82 257 5216; fax: +81 82 257 5219. (E-mail: orichan{at}hiroshima-u.ac.jp).

	Abstract

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion References

 
Objective: Although malposition of a catheter for selective cerebral perfusion can lead to postoperative neurologic complications, the clinical relevance or even an incidence of this event is not clear because there have been no measures to diagnose it. The purpose of this study is to report the results of intraoperative diagnosis of catheter malposition by means of near-infrared spectroscopy, orbital ultrasound, and transesophageal echocardiography. Methods: The 35 consecutive patients of aortic arch aneurysm undergoing total arch replacement (13 patients) or transaortic stent graft implantation (22 patients) were examined. The regional oxygen saturation in the frontal lobe was continuously monitored with near-infrared spectroscopy. When cerebral malperfusion was suspected with saturation drop and reduced blood flow in orbital ultrasound, blood flow in the cervical branches and catheter position were examined with transesophageal echocardiography. Results: Catheter malposition was detected in 4 of 35 cases (11.4%). The echo findings included: (1) reduced or absent flow and/or collapsed lumen in the common carotid artery despite an adequate perfusion rate; and (2) the balloon of catheter blocking the inflow to the common carotid artery. There was no unusual changes in parameters of other conventional monitors. After the catheter was withdrawn (three cases) or replaced (one case) based on the above diagnosis, cerebral perfusion was restored, confirmed by these three modalities. An accidental entry of catheter into the right common carotid artery was detected by transesophageal echocardiography in one case, in which there was no abnormal finding of oxygen saturation or orbital blood flow. Conclusions: Catheter malposition on the right side is not a rare event during selective cerebral perfusion. The catheter can migrate into the right subclavian artery or common carotid artery. Pressure monitoring cannot reliably detect an occurrence of catheter migration into the right subclavian artery. Combined use of near-infrared spectroscopy, orbital ultrasound, and transesophageal echocardiography can be useful for detecting this event and making an appropriate decision without delay to prevent irreversible brain damage.

Key Words: Selective cerebral malperfusion • Aortic arch aneurysm • Transesophageal echocardiography • Malperfusion • Near-infrared spectroscopy

	1. Introduction

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion References

 
Neurological complications, which considerably deteriorate quality of life after surgery or make postoperative management troublesome, are caused mainly by cerebral arterial embolism or sustained malperfusion of the brain. While embolism can be avoided only by prevention, malperfusion of the brain can be corrected if it is detected early and the cause of malperfusion is identified and reversed without delay.

Although selective cerebral perfusion (SCP) is a well-established and commonly performed procedure in aortic surgery, there are a number of pitfalls with the potential to cause malperfusion of the brain. Unfortunately, complete elimination of neurological complications related to SCP has not been achieved. Although monitoring of pressure and perfusion-rate has been employed, such extracranial information does not necessarily reflect intracranial events. Conversely, transcranial Doppler is a potent monitoring modality that provides intracranial information by assessing the blood flow in the middle cerebral artery. However, the signal is hardly detectable during SCP when the perfusion pressure is low. Therefore, since 1998, we have introduced near-infrared spectroscopy (NIRS) [1–5], orbital ultrasound [6,7], and transesophageal echocardiography (TEE) [8,9] into our routine monitoring protocol during aortic surgery.

Malposition of SCP catheter (Fig. 1) is a potential cause of cerebral ischemia. However, even an incidence of this event is not clear because there have been no measures to diagnose it. We have applied the above three modalities to detecting and making diagnosis of SCP catheter malposition and have recognized that this event is not uncommon. The purpose of this study is to report the results of intraoperative diagnosis of catheter malposition by means of NIRS, orbital ultrasound, and TEE.

View larger version (25K): [in this window] [in a new window]   Fig. 1. Schematic illustration showing obstruction of right common carotid artery (CCA) by the balloon of catheter (CATH) for selective cerebral perfusion. The catheter tip is in the right subclavian artery (SCA). IA, innominate artery.

	2. Materials and methods

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion References

The tissue oxygen saturation (rSO2) in the bilateral frontal lobes was continuously monitored throughout the surgery by means of an NIRS system, TOS-96 (TOSTEC Co. Ltd, Japan) with a pair of sensors placed on the patient's forehead. When the rSO2 dropped below 60% or the perfusion pressure was unusually low despite an adequate perfusion rate, the blood flow was examined by means of orbital ultrasound. The central retinal artery was visualized with a 7.5MHz echocardiographic probe that was part of the TEE system. The probe was placed on the eyelid, which was covered with an adhesive patch [6,7]. In order to minimize ocular tissue damage, the duration of exposure of the eye to ultrasound was less than 30s. When the blood flow in the central retinal artery became undetectable and remained so after increasing the perfusion rate, malperfusion of the common carotid artery was suggested; the common carotid artery was then explored by means of 5MHz biplane TEE (EUB-555, Hitachi Co. Inc., Japan). In addition to the routine monitoring of cardiac performance during surgery by cardiovascular anesthesiologists, the arch branch arteries were visualized and the blood flow in these arteries was examined (as previously reported [8,9]) before, during, and after cardiopulmonary bypass, and whenever TEE assessment was considered to be necessary.

After SCP was established, the perfusion catheter was depicted in the innominate artery as highly echogenic with acoustic shadow. The balloon near the catheter tip was depicted as a highly echogenic arc with reverberations or acoustic shadow behind it. In color Doppler mode, turbulent flow was seen in the right common carotid and subclavian arteries. When the catheter itself could not be depicted, the presence of turbulent flow indicated that the catheter tip was situated proximal to the visualized portion of the artery.

The TEE findings as well as the data from NIRS and orbital ultrasound was provided to the surgeon whenever it was necessary to discuss the significance of these findings and to determine the strategy for solving the problem.

	3. Results

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion References

 
There was one operative mortality (case #35) due to cardiac failure and one late death at 7 months after surgery (case #4): 5.7% mortality at one year postoperatively (Table 1). Two cases (#6 and #10) had cerebral infarction postoperatively. It was possible to obtain the rSO2 data throughout the surgical procedure in every case. No complications related to the TEE examination or orbital ultrasound were encountered despite repeated probe manipulations and visualization attempts. In 4 of 35 cases (11.4%), malperfusion of the right common carotid artery was suspected, based on NIRS and/or orbital ultrasound monitoring, and the blood flows in the branch arteries were examined with TEE.

Case #34 was a 72-year-old male patient who underwent transaortic stent-graft implantation. Before cardiopulmonary bypass, blood flow was detected in the bilateral central retinal arteries with orbital ultrasound and in the right common carotid artery with TEE. After SCP was started, orbital ultrasound showed that blood flow in the right central retinal artery was undetectable (while it was detectable on the left side), despite acceptable perfusion pressure. TEE revealed that blood flow was hardly detectable in the right common carotid artery. The flow signal was apparently higher in the right internal jugular vein than in the common carotid artery (Fig. 2: left). The tip of the SCP catheter was found in the right subclavian artery (Fig. 3: left). As the surgeon withdrew the catheter by a few centimeters, the catheter tip moved proximally (Fig. 3: center, right). The blood flow in the right common carotid artery then became clearly detectable (Fig. 2: right).

View larger version (80K): [in this window] [in a new window]   Fig. 2. Transesophageal echocardiogram showing the short-axis view of right common carotid artery (CCA) and jugular vein (transverse scan) in case #34. Left: malperfusion of right CCA due to catheter malposition. The flow signal is absent in the CCA, while it is detected in the vein. Right: after correction of malposition. The flow in the CCA is detected and its velocity is higher than that of jugular vein.

View larger version (69K): [in this window] [in a new window]   Fig. 3. Transesophageal echocardiogram showing retreat of catheter in the subclavian artery (SCA) to the innominate artery (IA) in case #34 (transverse scan). Left: the balloon situated at the bifurcation and turbulent flow is seen at the catheter tip. Center: the catheter tip moved proximally (rightward in the view). Right: the catheter is already out of view.

View larger version (110K): [in this window] [in a new window]   Fig. 4. Transesophageal echocardiogram showing the long-axis view of right common carotid artery (CCA) and the balloon at the bifurcation, obstructing the orifice of CCA in case #29 (longitudinal scan). IA, innominate artery.

Case #3 was a 66-year-old male patient who underwent total arch replacement. When SCP was started, the perfusion pressure was 30mmHg on both sides and the bilateral rSO2 dropped below 60%. As a vasoconstrictor was administered and the perfusion pressure was elevated to 39mmHg, the blood flow in the central retinal artery became narrowly detectable on both sides. However, the right central retinal arterial flow became undetectable again and the right rSO2 dropped to 55%, while the left rSO2 remained over 60%. TEE revealed that the blood flow in the right common carotid artery had a to-and-fro pattern and that the antegrade flow component was small (Fig. 5A). The balloon of the SCP catheter was found just at the bifurcation of the common carotid artery and the subclavian artery. Although the surgeon tried to withdraw the catheter, the position of the balloon remained unchanged. Therefore, the perfusion catheter was replaced with another type (14F cannula, Medtronic DLP, Chase Medical Inc., USA). The blood flow in the right common carotid artery was then clearly detected with a dominant antegrade component (Fig. 5B). The right rSO2 was also restored to above 60%.

View larger version (64K): [in this window] [in a new window]   Fig. 5. Transesophageal echocardiogram showing the change of flow pattern in the right common carotid artery (CCA) in case #3. (A) to-and-fro flow in the right CCA (longitudinal scan) due to catheter malposition. The flow velocity is as low as 3–4cm/s. (B) an improved antegrade flow in the right CCA (longitudinal scan) after replacement of catheter. The flow velocity is over 30cm/s.

Besides the above four cases, we experienced one case of accidental entry of SCP catheter into the common carotid artery. Case #5 was a 65-year-old male patient who underwent total arch replacement for ruptured aortic arch aneurysm. TEE revealed that the tip of the SCP catheter was in the right common carotid artery. There was some blood flow detected around the balloon toward the right subclavian artery. There was no significant abnormality or change in the perfusion pressure on the right side.

	4. Discussion

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion References

 
It may be argued that this kind of study is unnecessary since it appears: (1) that malposition of an SCP catheter rarely occurs (and has not been reported in the literature); (2) that in the event of catheter malposition, the catheter would enter the right common carotid artery and that this event can be easily detected by the decrease in the right radial arterial pressure; (3) that even if the catheter happens to enter the right subclavian artery, a functioning circle of Willis would compensate for cerebral malperfusion; and (4) that catheter malposition cannot, therefore, be a serious problem.

However, our findings will come as a disappointment to those who hold the foregoing views; namely: (1) the occurrence of malposition of an SCP catheter placed in the innominate artery is not uncommon (11.4% in our series); (2) the catheter can migrate into the right subclavian artery as well as into the common carotid artery; (3) pressure monitoring cannot always detect the occurrence of catheter migration into the right subclavian artery; (4) the function of the circle of Willis can be inadequate as suspected by the rSO2 drop in the cases of SCP catheter malposition in our series; (5) malposition of SCP catheter can, therefore, occur and can lead to cerebral ischemia, which is potentially responsible for neurological symptoms (including cognitive disorders).

Two factors may be responsible for occurrence of malposition: variation in length of the innominate artery among the patient population, and accidental migration of the catheter tip. The latter mechanism is likely to have been responsible for the events in cases #4, #29, and #34 because malposition was corrected by withdrawing the catheter. In case #3 the innominate artery may have been short because withdrawal of the catheter did not solve the problem—despite the catheter having been inserted from the origin of the innominate artery.

Because an occurrence of catheter malposition cannot be predicted and is invisible within the surgical field, methods for detecting this event are needed. The NIRS, which provides intracranial information noninvasively and continuously, is advantageous for detecting an occurrence of malperfusion. However, the rSO2 drop can be caused by several mechanisms. Reduced arterial blood flow in the carotid artery is likely to be the major mechanism of sudden rSO2 drop during aortic surgery, and can be confirmed by means of TCD or orbital ultrasound. Surgeon can readily withdraw the SCP catheter and this procedure solved the problem in three of four cases but not in all cases. The cause of malperfusion needs to be searched for in the proximal portion of the common carotid artery, the perfusion catheter, or the SCP circuit.

Malposition of the catheter tip can be examined noninvasively by TEE without interrupting the surgical procedures. The TEE findings that indicate catheter malposition are summarized as follows: (1) the catheter tip is depicted in the right subclavian artery; (2) the balloon is located at the bifurcation and occludes the orifice of the common carotid artery; (3) the lumen of the right common carotid artery is collapsed, the flow signal in it is weaker than that in the adjacent jugular vein, or the blood flow in the right common carotid artery is undetectable, weakly detectable, or has a to-and-fro pattern when examined in the long-axis view of the right common carotid artery. The accuracy of TEE diagnosis can be confirmed by the improvement of the above findings after the malposition is corrected—usually by withdrawing the catheter proximally or occasionally by replacing the catheter. These findings are often followed by improved rSO2 or better detection of central retinal artery flow in orbital ultrasound.

It is not clear, however, whether the catheter malposition detected by TEE in these four cases would have caused clinically significant brain damage had it not been corrected. In each case, we corrected the malposition immediately because the TEE finding was accompanied by an inadequate central retinal arterial blood flow, in orbital ultrasound, or by a significant rSO2 drop, by NIRS monitoring—both of which have been shown to be related to an occurrence of neurological dysfunction [5,7]. However, this could be a limitation in terms of a clinical investigation.

Recently, axillary arterial perfusion has been gaining popularity in aortic arch surgery. In this procedure, cannula malposition may cease to be a problem. However, this artery is occasionally small for an adequate perfusion rate through a catheter of an appropriate size. The remnant of vascular prosthesis used for perfusion may limit a future use of subclavian vein for central venous route because of a risk of infection.

The catheter malposition may be visualized by using epiaortic echo manipulated by the surgeon. However, the common carotid artery and bifurcation are often difficult to visualize from the operating field and manipulating the epiaortic echo takes time and elongates the SCP time.

In conclusion, the incidence of malposition of SCP catheter is found to be not low and it occurred on the right side. It can occur in any case and is unpredictable. Combined use of NIRS, orbital ultrasound, and TEE is helpful for detecting this event intraoperatively and enabling to solve cerebral malperfusion before irreversible brain damage develops.

	References

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion References

 

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