Eur J Cardiothorac Surg 2007;32:751-755. doi:10.1016/j.ejcts.2007.08.014
Copyright © 2007, European Association for Cardio-thoracic Surgery. Published by Elsevier. All rights reserved.
Is unilateral brain regional perfusion neurologically safe during congenital aortic arch surgery?
Jae Gun Kwaka,
Woong-Han Kima,*,
Ah Young Ohb,
Tae Gyoon Yoonb,
Hee-Soo Kimb,
Jong Hee Chaec,
Soo Yeon Parkc
a Department of Thoracic and Cardiovascular Surgery, Seoul National University Children's Hospital, Seoul, Republic of Korea
b Department of Anesthesiology, Seoul National University Children's Hospital, Seoul, Republic of Korea
c Department of Pediatrics, Seoul National University Children's Hospital, Seoul, Republic of Korea
Received 27 May 2007;
received in revised form 15 July 2007;
accepted 6 August 2007.
* Corresponding author. Address: Department of Thoracic & Cardiovascular Surgery, Seoul National University, College of Medicine, Seoul National University Children's Hospital, 28 Yongon-Dong, Jongno-Gu, Seoul 110-744, Republic of Korea. Tel.: +82 2 2072 3637; fax: +82 2 3672 3637. (Email: woonghan{at}snu.ac.kr).
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Abstract
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Objective: This study was conducted to demonstrate that unilateral brain regional perfusion during congenital aortic arch anomaly surgery is neurologically safe. Methods: Fifteen patients who were diagnosed with congenital aortic arch anomaly between June 2004 and May 2006 were enrolled in this study. The mean age and body weight of the enrolled patients were 40.3 ± 35.9 days and 3.7 ± 1.0 kg, respectively. Underlying diseases included coarctation of the aorta (12) and an interrupted aortic arch (3). The pre- and postoperative neurological state of each patient was evaluated by a neurologist using an electroencephalogram and brain SPECT. During the operation, unilateral brain regional perfusion was performed using innominate arterial cannulation. Near-infrared spectroscopy (NIRS) and transcranial Doppler ultrasonographic evaluation of the cerebral artery was used to monitor the cerebral perfusion state during surgery. After being discharged a neurologist conducted regular follow-up evaluations of the patients to monitor their neurological development. Results: There were no operative mortalities. Based on NIRS data, there were no significant differences between left and right oxygen saturation during regional perfusion (left:right = 66.0 ± 10.4%:69.8 ± 1.0%, p
= 0.72) or between the pre-regional and regional perfusion period (1. left side pre-regional perfusion:regional perfusion = 66.9 ± 11.8%:66.0 ± 10.4%, p
= 0.92, 2. right side pre-regional perfusion:regional perfusion = 70.2 ± 11.1%:69.8 ± 10.0%, p
= 0.96). Additionally, there were no differences between pre- and postoperative findings in EEG and brain SPECT. For 17.5 ± 9.0 months of follow-up duration, no patients showed abnormal neurological finding and development. Conclusions: Unilateral brain regional perfusion in neonates and children may be a useful technique with no significant neurological deficit.
Key Words: CHD • Great vessel anomalies • Aortic arch • Neurocognitive deficits
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1. Introduction
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Until the introduction of the regional perfusion technique, the use of deep hypothermia and circulatory arrest in children and neonates who have undergone complex aortic arch reconstruction was considered unavoidable. Due to the decreasing mortality rate in congenital cardiac surgery, neurological morbidity is now the primary concern after surgery.
In neonates it is technically difficult to cannulate both carotid arteries for selective cerebral perfusion during aortic arch surgery, therefore, innominate arterial cannulation is frequently used (unilateral brain regional perfusion). This study was conducted to confirm the neurological safety of unilateral brain regional perfusion based on analysis of pre- and postoperative neurological examination and analysis of near-infrared spectroscopic (NIRS, INVOS® cerebral oximeter, SOMANETICS®) data during the operation and evaluation of neurological development after discharge.
This study tested the following hypotheses: 1. No differences exist between right and left cerebral perfusion during unilateral brain perfusion. 2. No differences exist between the pre-regional and regional perfusion periods during cerebral perfusion. 3. Unilateral brain perfusion conducted using innominate artery cannulation is neurologically safe.
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2. Materials and methods
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Between June 2004 and May 2006, 15 neonates who underwent aortic arch surgery using unilateral brain perfusion were enrolled. The mean age and body weight of the subjects was 40.3 ± 35.9 days (range 3–115 days) and 3.7 ± 1.0 kg (2.9–6.1 kg), respectively. The underlying diseases included coarctation of the aorta (CoA) with VSD (11), CoA with an anomalous origin of the right pulmonary artery from the aorta (1), interrupted aortic arch (IAA) with VSD (2), and IAA with truncus arteriosus (1). The university ethics committee reviewed and approved this study (study approval number H-0504-146-004), and full informed consent regarding pre- and postoperative neurologic study and evaluation, intraoperative neurophysiologic monitoring and data collection with analysis were obtained from all parents who participated in the study.
2.1 Methods of evaluation
In general, the neurological and brain perfusion status of patients were evaluated preoperatively using electroencephalography (EEG) and brain single photon emission computed tomography (SPECT), however these examinations were not performed in cases that required emergent operation. For emergent cases, bedside brain ultrasonography was used. Blood pressure was monitored at the right radial artery. Brain perfusion status was monitored by NIRS from beginning of surgery in every 30 s (Fig. 1
) during operation and NIRS monitoring was maintained for 1 or 2 days after surgery.
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Fig. 1. Brain saturation monitoring using near-infrared spectroscopy (NIRS, INVOS® cerebral oximeter, SOMANETICS®) in some patients during the operation and postoperative period, solid line: right side; dotted line: left side; SrO2: regional saturation of brain.
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Transcranial Doppler ultrasonography was used for direct measurement of blood flow velocity of middle cerebral arteries in the last 4 cases. Differences between left and right saturation during the regional perfusion procedure as well as differences between the pre-regional and regional perfusion periods were analyzed using a paired t-test, and these results are expressed as medians and ranges or as means ± standard deviation. Results were considered statistically significant when p was <0.05.
Before discharge, EEG and brain SPECT were checked again and a neurologist evaluated their neurological status. Neurological evaluation was continued until a neurologist deemed it was no longer necessary.
2.2 Surgical technique
Six Fr (2.0 mm) or 8 Fr (2.7 mm) of arterial cannula (RMI®, Edwards Lifesciences LLC, Irvine, CA) was inserted directly through the innominate artery and standard bicaval cannulation was instituted. In the case of the IAA, 8 Fr of another flexible arterial cannula (DLP®, Medtronic DLP, Grand Rapids, MI) was introduced at the proximal PDA and advanced into the descending aorta. These two arterial cannulae were then Y-connected and cardiopulmonary bypass (CPB) started. When appropriate, a left ventricular vent (10 Fr, DLP®, Medtronic Inc., Minneapolis, MN) was introduced through the right upper pulmonary vein or left atrial appendage. The pH-stat strategy was used exclusively for acid–base management, and enough time was allowed for the desired core temperature (28 °C) to be attained. During cooling, distal pulmonary arteries up to the second branch level, arch vessels, and descending aorta were extensively mobilized to relieve tension following anastomosis. When the desired rectal temperature was attained, the proximal innominate artery, left common carotid artery, and left subclavian artery were snared down to initiate the regional cerebral perfusion. The innominate arterial cannula and aortic root cannula were T-connected to maintain simultaneous myocardial perfusion (Fig. 2
) and the ascending aorta immediately distal to the root cannula was clamped to produce isolated myocardial perfusion. Flow rate, mean blood pressure of the right radial artery, and mean hematocrit were maintained at approximately 50–100 ml/kg/min, 50–60 mmHg, and 30%, respectively. The technical details of the arch repair have been previously described [1]. Following the aortic arch repair, snares of the arch vessels and the descending aortic clamp were removed, with subsequent restoration of flow rate. Myocardial perfusion was stopped and cardioplegic solution was applied for intracardiac repair, if necessary.
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Fig. 2. Illustrations showing the operative technique. Circuitry for isolated cerebral and myocardial perfusion.
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Patients were managed in the intensive care unit and general ward in a fashion similar to other postoperative cardiac patients.
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3. Results
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Cardiac anomalies, including aortic arch anomaly, were entirely corrected in one stage in all patients. CPB time was 148 ± 54 min and regional perfusion time was 25.7 ± 7.3 min. There were no surgical mortalities or complications. The operation needed to be repeated in two patients due to a left ventricular outflow tract obstruction (LVOTO), one of them caused by subaortic fibrous membrane and the other by natural progression of bicuspid aortic valve stenosis. The former LVOTO was treated by resection of the subaortic membrane and the latter was corrected by Ross-Konno procedures. One additional patient required a second operation to change right ventricle to pulmonary artery conduit because of conduit stenosis. No additional operations were necessary for the arch anomalies repair.
Abnormal postoperative EEG (as compared to preoperative EEG results) was found in one patient who exhibited partial seizure. However, this patient showed no clinical abnormality or deficit with normal neurological development upon out-patient clinic (OPD) follow-up. Another patient, who could not be evaluated by EEG due to an urgent surgery, also showed abnormal EEG findings in the form of a partial seizure postoperatively, however this patient showed no clinical abnormalities or deficit during the postoperative period and OPD follow-up. The remainder of the patients had normal postoperative EEGs.
Postoperative brain SPECT results indicated two patients exhibited ‘mild perfusion decrease’. One of these patients exhibited a mild decrease in perfusion in right frontal lobe; the other exhibited a mild decrease in perfusion on the border of the right parietal lobe and the right frontal lobe, in the right cerebellum. All remaining patients exhibited no decrease in perfusion or differences between pre- and postoperative brain SPECT findings. And no clinically problematic findings were observed in above two patients whose brain SPECT indicated ‘mild perfusion decrease’.
During the operation we used NIRS to evaluate two aspects of brain perfusion status. First, we compared full flow status with unilateral flow status. This is to demonstrate the adequacy of unilateral brain regional perfusion itself by comparing the saturation between the period of pre-regional perfusion (full flow on CPB) and on-regional perfusion (partial flow on CPB). Second, we attempted to verify that right innominate arterial cannulation alone could supply adequate blood flow to both the left and right hemispheres by comparing right hemisphere saturation with left hemisphere saturation.
Regarding the adequacy of the regional perfusion, brain perfusion resulted in no saturation difference between the pre- and on-regional perfusion period. Before regional perfusion, during full flow state of the CPB, left side oxygen saturation was 66.9 ± 11.8%, whereas during regional perfusion left side oxygen saturation was 66.0 ± 10.4% (p
= 0.92). The right side oxygen saturation was 70.2 ± 11.1% prior to regional perfusion and 69.8 ± 10.0% (p
= 0.96) during regional perfusion. There was no oxygen saturation difference between the pre-regional perfusion and on-regional perfusion state in both sides. Regarding the use of the right innominate arterial cannulation, difference between left and right cerebral oxygen saturation was 6.3 ± 4.4% prior to regional perfusion and 6.5 ± 5.4% (p
= 0.72) during the regional perfusion, and this indicates that no significant difference between the right and left hemisphere existed during unilateral brain perfusion. A transcranial Doppler ultrasonographic evaluation was used to evaluate the middle cerebral arterial flow in the four recent patients, and the results showed that blood flow of the contralateral middle cerebral artery was similar to that of the ipsilateral middle cerebral artery (Table 1
, Fig. 3
).
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Fig. 3. Transcranial Doppler ultrasonographic flow evaluation of the middle cerebral artery during the regional perfusion procedure in patient #1. Upper panel shows the Doppler flow rate of the right middle cerebral artery and lower panel shows that of the left middle cerebral artery (mean flow rate 24 cm/s in right, 21 cm/s in left).
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All patients underwent follow-up evaluation in OPD. Among them, one patient exhibited hydrocephalus, but this condition existed before surgery and was determined to be of no clinical significance by a neurologist. All other patients exhibited normal developmental status throughout the follow-up period (mean follow-up duration = 17.5 ± 9.0 months).
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4. Discussion
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We have conducted aortic arch surgery under deep hypothermic status with total circulatory arrest. Regional brain perfusion was introduced to avoid the neurological complications associated with circulatory arrest method [2–7].
Although in some cases postoperative EEG and brain SPECT showed slightly abnormal results, neurological development of the patients in this study was normal, therefore we thought that these observed abnormal findings had no clinical significance. The brain SPECT revealed a slight decrease of perfusion in two patients. This slight perfusion decrease was located on the right side, and this side was directly perfused by right innominate arterial cannulation. Considering the locations of these decreases in perfusion, left side perfusion through the right innominate artery perfusion was not the cause of this presentation. There was no decrease of perfusion observed on left side, which demonstrates that regional perfusion through the right innominate artery alone supplied enough flow to the contralateral side of brain.
It is important to note that we maintained the regional flow rate at 50–100 ml/kg min during regional perfusion state, which is relatively high. However this high flow rate was necessary because we also performed regional perfusion on the coronary artery in addition to the brain to maintain the heart rate, and we could not exactly predict blood flow distribution or ratio between brain and coronary artery system during the procedure. In addition to ensuring adequate blood flow to coronary arterial system during the procedure, blood flow rate is needed to be maintained highly because brain perfusion is dependent upon actual blood pressure rather than the perfusion rate [8].
The value of NIRS for evaluation of brain perfusion status during operation has been reported previously [9–11], therefore we used NIRS to evaluate the perfusion status during the unilateral brain regional perfusion procedure and confirmed that there were no differences between left and right brain perfusion. Additionally, NIRS confirmed that there were no differences between the pre- and on-regional perfusion periods. We added transcranial Doppler ultrasonographic flow measurement as an evaluation tool for direct confirmation for middle cerebral arterial blood flow in four most recent cases. We measured flow rate of left and right middle cerebral arteries at the beginning of the surgery as a baseline, during CPB and regional perfusion, and at the end point of the regional perfusion. And we found no difference in flow rate between left and right middle cerebral arteries.
It should be noted, however, that this study is limited by a small number of patients as well as a lack of comparison with patients who were operated on under total circulatory arrest while in a state of deep hypothermia. The study was also limited because we did not evaluate the anatomy of the circle of Willis preoperatively. Brain circulation in neonates and infants is different from that of adults in that it shows characteristic features of fetal brain circulation, including well developed collateral vessels and instant angiogenesis for acute decreased blood flow states, such as right common carotid artery ligation for extracorporeal membrane oxygenation support [12,13]. We have already performed unilateral regional brain perfusion on 69 patients who were diagnosed with an aortic arch anomaly and fortunately, there have been no abnormal neurological complications or developmental disturbances observed during mid- and long-term follow-up [1]. Of course, it is difficult to routinely evaluate the anatomy of the intracranial vessels of every patient through brain MR angiography or brain CT angiography prior to operation. However, using a simple tool like color Doppler imaging could be helpful in evaluating the circle of Willis preoperatively [12]. Additionally, we had intended to change our method from regional perfusion to total circulatory arrest if real-time spectroscopy or Doppler of middle cerebral arterial findings revealed a significant saturation difference between the right and left hemispheres or a difference between blood velocity in the operating room, however no such cases occurred in this study.
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5. Conclusions
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In conclusion, our protocol of brain regional perfusion during aortic arch surgery seems likely to supply adequate and even perfusion flow to both the left and right brain in neonates and children. Additionally, based on the data obtained from pre- and postoperative EEG and brain SPECT, we demonstrated that this method results in no significant neurological deficits.
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Acknowledgments
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The authors are grateful to the Medical Research Collaborating Center of Seoul National University Hospital for providing a statistical review of this study.
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Footnotes
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\#9734; This work was supported by a Korean Research Foundation Grant funded by the Korean Government (MOEHRD, Basic Research Promotion Fund) (KRF-2005-003-E00166).
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Abstract
1. Introduction
