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PEDIATRIC ANESTHESIA

Intraoperative Transesophageal Echocardiography in Pediatric Congenital Cardiac Surgery: A Two-Center Observational Study

Dominique A. Bettex, MD^*, Daniel Schmidlin, MD^*, Marc-André Bernath, MD, René Prêtre, MD, Michel Hurni, MD, Rolf Jenni, MD MSEE^||, Pierre-Guy Chassot, MD, and Edith R. Schmid, MD^*

*Division of Cardiovascular Anesthesia, University Hospital of Zurich, Switzerland; Department of Anesthesia, University Hospital of Lausanne, Switzerland; Department of Cardiovascular Surgery, University Hospital of Zurich, Switzerland; Department of Cardiovascular Surgery, University Hospital of Lausanne, Switzerland; ||Department of Cardiology, University Hospital of Zurich, Switzerland

Address correspondence and reprint requests to Dominique A. Bettex, MD, Division of Cardiovascular Anesthesia, USZ-Raemistrasse 100, CH-8091 Zurich, Switzerland. Address email to dominique.bettex{at}ifa.usz.ch

	Abstract

Top Abstract Introduction Methods Results Discussion Conclusion References

 
Transesophageal echocardiography (TEE) is a monitoring and diagnostic tool for the care of children undergoing cardiac surgery. We analyzed reports from 865 routine TEE examinations performed between January 1994 and March 2002 in patients younger than 17-yr-old who were undergoing surgery for congenital heart disease. Patients’ median age was 36 mo (range, 1 day–16 yr). The primary end-point of the study was the incidence of surgical and medical management decisions changed as a result of TEE findings; secondary end-points were diagnostic impact (diagnostic exclusions and new diagnoses) and surgical outcome. Fifty percent of the examinations were performed by anesthesiologists with an advanced level of training in perioperative TEE; all of the examiners had an experience of 500 TEE examinations. Supervision by an anesthesiologist with an advanced level of training was requested in 36.7% of cases; supervision by a cardiologist was requested in 3.8%. Surgical alterations of management were reported in 12.7% of cases and included the need for a repeat bypass run in 7.3%; medical alterations of management were required in 19.4% of cases. We observed a diagnostic impact of TEE in 18.5% of cases and a suboptimal but acceptable surgical outcome in 27.6%; TEE findings predicted postoperative difficulties in 4.0%. Our results confirm the utility of routine TEE to assess repair of congenital heart defects. Furthermore, this service was competently performed by a regular team of cardiac anesthesiologists appropriately trained in TEE.

IMPLICATIONS: Transesophageal echocardiography (TEE) is an essential monitoring and diagnostic device for the care of children undergoing cardiac surgery. The surgical and medical impact of TEE is demonstrated in a large series of patients. This service can be performed by appropriately trained cardiac anesthesiologists.

	Introduction

Top Abstract Introduction Methods Results Discussion Conclusion References

 
Since the advent of small pediatric probes in the 1990s, transesophageal echocardiography (TEE) has become an important monitoring and diagnostic tool in the care of children undergoing surgery for congenital heart disease. According to the practice guidelines for perioperative TEE established by the Society of Cardiovascular Anesthesiologists and the American Society of Anesthesiologists (1), there is strong evidence for the usefulness of TEE in surgery for congenital heart disease because it significantly improves the clinical outcome of these patients. Although it is now common practice for anesthesiologists to be primarily responsible for the interpretation of intraoperative TEE during adult cardiac surgery, their role in TEE during congenital cardiac surgery is still being debated (2,3). The purpose of this observational study was to delineate the impact of TEE on patient management during pediatric cardiac surgery for congenital heart disease in two university hospitals in Switzerland. Our expectations were that TEE performed during congenital heart surgery by appropriately trained anesthesiologists would result in changes in surgical and medical management in a significant number of cases irrespective of the pediatric population studied.

	Methods

Top Abstract Introduction Methods Results Discussion Conclusion References

 
Between January 1994 and March 2002, standardized reports were obtained from TEE examinations in patients younger than 17-yr-old who were undergoing congenital heart surgery in two university hospitals in Switzerland. In the absence of formal contraindications, every patient weighing >3.5 kg had a routine TEE examination. For patients weighing <3.5 kg, insertion of the probe (9.1 mm x 8.8 mm) was attempted for any complex defect or after surgical indications. Our weight limit was established according to the manufacturer’s recommendations.

We designed a simplified classification of surgical procedures based on an anatomophysiological approach and adapted from the classification of Gallivan et al. (4). Three categories of risks of surgical procedures were distinguished as follows:

1) low risk; e.g., atrial septal defect (ASD), ventricular septal defect (VSD), valve replacement, extracardiac procedures.

2) moderate risk; e.g., atrioventricular (AV) canal, combined ASD and VSD or combined VSD and pulmonary stenosis, valve reconstruction, subaortic stenosis (SAS) resection.

3) high risk; e.g., reoperation and neonatal surgery, Fontan procedure, Fallot’s tetralogy, Ebstein anomaly.

Before induction of anesthesia, all patients were monitored with a five-lead, two-channel electrocardiograph, pulse oximeter, noninvasive blood pressure measurement, and precordial stethoscope. General anesthesia was induced with halothane; later in the series, sevoflurane was used. The administration of fentanyl and pancuronium followed the insertion of a peripheral line. Patients were nasotracheally intubated and mechanically ventilated. Invasive monitoring was performed (via radial or femoral arterial line, internal jugular or femoral central venous catheter), and a nasogastric tube, a Foley catheter, and a rectal temperature probe were inserted. The previously lubricated TEE probe was inserted blindly with or without a jaw thrust of the mandible or under direct laryngoscopic visualization. A pediatric probe (biplane probe with 64 elements per transducer and dimensions of 9.1 mm x 8.8 mm; 7.5/5.5 MHz) was used for patients who weighed <20 kg. For patients weighing >20 kg, a pediatric biplane probe or an adult-sized multiplane probe (14 mm; 5 MHz) was used, at the anesthesiologist’s discretion. TEE examinations were performed using Philips Sonos 1000, 1500, or 5500 echocardiography machines (Philips, Andover, MA) equipped with pulsed, continuous wave, and color Doppler capabilities. All TEE examinations were conducted in the presence of a second anesthesiologist who was responsible for the care of the patient.

Complete TEE examinations were conducted before cardiopulmonary bypass (CPB) to confirm or modify the interpretation of preoperative examinations. In case of relevant modifications of the preoperative diagnosis, the pre-CPB TEE findings were displayed and discussed with the surgical team. After the initial examination, the probe was advanced into the stomach and left in an unlocked position during the procedure; the ultrasound emission was turned off during bypass. During weaning from CPB, the postrepair examination was performed. If significant residual abnormalities were found, intraoperative invasive confirmation was attempted (invasive measurement of pressures or gradients and oxygen saturations). In case of persistent doubt, an experienced cardiologist echocardiographer was consulted, and the decision to return to bypass was taken as a team approach. We classified the indications for a second bypass run into two groups:

1) clear-cut indications: intractable hemodynamic instability or new or residual defects that would, with high probability, modify the postoperative course of the patient (e.g., misplacement of a patch, significant residual shunt, significant residual valve regurgitation, or severe residual gradient).

2) accessory indications: second bypass runs done for the sake of a perfect surgical result (e.g., residual patent foramen ovale or residual small atrial or ventricular septal defect). The probe was left in place until the end of the procedure for hemodynamic management.

Examinations were performed by staff cardiac anesthesiologists exclusively dedicated to intraoperative TEE for the duration of the procedure. Examiners had different levels of training: "advanced level" was defined according to guidelines of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists Task Force (5). All examiners had performed 500 TEE examinations. It was the decision of the anesthesiologist in charge to ask for supervision when needed. The anesthesiologist who performed the TEE prospectively completed a standardized data sheet on which was recorded surgical alteration of management, need for repeat bypass runs, medical alteration of management (defined as changing inotropes, adding vasodilators or vasopressors, volume expansion), new diagnosis such as new postoperative ventricular dysfunction, diagnostic exclusions (defined as diagnoses expected by the surgeon that were not found in postbypass examination, e.g., residual valve regurgitation, residual shunt, or residual gradient), residual abnormalities, and expected postoperative difficulties.

The primary end-point of our study was the incidence of alterations in surgical management (including the need for repeat bypass run) and medical management supported by TEE findings. As secondary end-points we considered the incidence of a new diagnosis, diagnostic exclusions, and surgical outcome. Surgical outcome was categorized according to the presence of residual abnormalities and their expected postoperative significance: 1) excellent (no more than mild residual abnormality); 2) suboptimal but acceptable; or 3) significant postoperative difficulties or outcome, with limited hope or expected death.

For statistical analysis we used Stat View 5.01 (SAS Institute Inc., Cary, NC) and SPSS 11.0 (SPSS Inc, Chicago, IL). Descriptive statistics are presented as total and percent unless otherwise specified. Univariate analysis was done by means of the Mann-Whitney U-test for continuous variables and Pearson’s ² test for nominal variables. The surgical impact of TEE was analyzed with a logistic model:

where P is the probability of a positive surgical impact and is a constant value. Age is coded 0 if age is 1 mo, and 1 otherwise; is the corresponding regression coefficient. P values of < 0.05 were considered significant.

	Results

Top Abstract Introduction Methods Results Discussion Conclusion References

 
The reports of 865 consecutive TEE examinations performed in two university hospitals (centers A and B) were analyzed. Patient characteristics and operation categories are listed in Table 1. Note that the number of infants and children is different between the two centers. Additional procedures were sometimes performed in conjunction with the primary procedure. Therefore, the total number of specific procedures exceeds the total number of patients.

Although we did not record new preoperative diagnoses that had no surgical relevance, we reported the alterations in surgical plan after unsuspected preoperative TEE findings, which occurred in 18 patients (2.1%). The unsuspected findings and the modified procedures are described in Table 2, and an example of an unsuspected preoperative finding with significant impact (thrombus in the stump of a divided pulmonary artery) is shown in Figure 1.

View larger version (116K): [in this window] [in a new window]   Figure 1. Thrombus in the stump of a divided pulmonary artery. LA = left atrium; RA = right atrium; RV = right ventricle; Ao = aorta; PA = pulmonary artery; Th = thrombus.

View larger version (109K): [in this window] [in a new window]   Figure 2. The patch used to cover an atrial septal defect was misplaced between the atrial septum and the tricuspid annulus. LA = left atrium; RA = right atrium; LV = left ventricle; RV = right ventricle; MV = mitral valve; TV = tricuspid valve; <<<< = patch.

Finally, we observed a biphasic incidence of second bypass runs over time (Fig. 3) with an initial rate of 1.7% in 1994, a maximum of 13.8% in 1998, and a minimum of 2.2% in 2001.

View larger version (32K): [in this window] [in a new window]   Figure 3. Incidence of second bypass runs over time.

TEE assisted medical management in 168 (19.4%) patients. It was used to optimize cardiac filling in 33 (3.8%) patients and led to adaptation of pharmacological therapy in 135 (15.6%) patients. There was no significant difference between centers A and B regarding the medical impact (Table 3).

We recorded 42 (4.9%) diagnostic exclusions. Residual abnormalities not requiring further surgery were detected by post-CPB TEE examination in 236 (27.3%) patients; among those were 47 minimal residual shunts, 33 unexpected cases of mild valve regurgitation, 22 small residual gradients, 118 cases of new ventricular dysfunction (48 in the systemic ventricle, 46 in the pulmonary ventricle, and 24 in both ventricles), and 16 other abnormalities; 118 (13.6%) of these residual defects led to medical adjustment of therapy. Thirty-five residual abnormalities (4.0%) were expected to significantly aggravate postoperative outcome, but further surgery was deemed impossible or not indicated. Seven of these patients died in the OR and 12 required mechanical assistance with the use of an extracorporeal membranous oxygenator (ECMO). Five of the latter patients died later in the intensive care unit. Two other patients with a good echocardiographic result died in the OR of uncontrollable hemorrhage.

Of the 60 patients who required a second or third bypass run, 28 (46.7%) had a perfect result, 18 (30%) had an acceptable result, and 14 (23.3%) maintained significant abnormalities with expected postoperative problems; 6 of the latter required an ECMO, and 3 died in the OR. The surgical outcome of the entire series and the differences between the two centers are shown in Table 3.

During long-term follow-up, we recorded 50 (5.8%) reoperations. Sixteen defects (1.8%) leading to reoperations might have been missed during intraoperative examination, although none of them required immediate surgery after the routine postoperative cardiologic transthoracic echocardiography examination. The defects included residual infundibular stenosis in 6 patients and residual VSD in 3 patients after Fallot correction, mitral regurgitation after AV canal correction or mitral valve repair in 4 patients, antero-apical aneurysm after VSD closure in 1 patient, residual left ventricular outflow tract obstruction and mitral regurgitation after hypertrophic obstructive cardiomyopathy surgery in 1 patient, and residual postoperative superior vena cava stenosis in 1 patient.

	Discussion

Top Abstract Introduction Methods Results Discussion Conclusion References

 
Our results confirm the potential benefit of echocardiography during congenital heart surgery to identify problems that need immediate surgical intervention and to assist intraoperative medical management. The perioperative impact of TEE in patients with congenital heart disease has been studied by several groups (6–12). Most of these studies were led by cardiologists. The present investigation is one of the first large reports of anesthesiologists’ experience for congenital heart surgery. Here we report the significant impact on medical and surgical therapy for intraoperative TEE in 32% of our patients, with an additional impact on diagnosis of 18.5%.

An alteration in preoperative diagnosis resulting in a modification of surgical therapy or strategy occurred in 2.1% of the cases. This percentage is in agreement with the published literature (11,13). In one study (11), minor variance in diagnosis was found in 6% of cases, and major variance was found in 0.5%. This incidence is obviously highly dependent on the quality of preoperative echocardiography analysis and the timing of the last preoperative examination. Some patients had a poor acoustic window, others came to operation based on cardiac catheterization findings only, and others had their last echocardiographic examination several months before operation.

Our multivariate analysis did not allow us to select one or more relevant preoperative factors to help us detect patients at risk for incomplete surgical correction. This is in agreement with previous studies, which showed that preoperative diagnosis, hemodynamic alterations, and surgical considerations are not sensitive enough to distinguish patients at risk for incomplete surgical correction (8,10,14). Before routine use of TEE in pediatric cardiac surgery, most of the residual defects were found after uneventful weaning from bypass. We chose early on (in 1994 in center A and 1996 in center B) to use TEE routinely for congenital cardiac surgery. Pre-CPB examination is usually the first TEE examination ever performed on a child; this examination is therefore expected to have a significant diagnostic impact.

The incidence of second bypass runs resulting from TEE findings alone or in association with clinical signs was 7.3%. This rate is also in agreement with previous findings (2,15) and is dependent not only on the seriousness of the residual defect found but also on the surgeon. The highest surgical impact of our intraoperative TEE was found in patients undergoing Ross procedure, SAS resection, and surgery for AV canal and arterial switch, followed by Fallot’s tetralogy surgery and VSD and ASD closure.

Multivariate analysis determined three significant factors likely to influence the surgical impact of TEE: the examiners, the age of the patients, and the type of operation. The age of the patient lost its significance as soon as we excluded the neonatal patients: there was no difference between infants and children. Because our weight restriction for TEE examination was 3.5 kg, our neonatal group was very small and cannot be considered representative. The significant role of examiners on the surgical impact might imply the need for a higher level of training. However, we could not find any correlation between the level of training of the examiners and TEE impact. The surgical impact of TEE also depended, at least in part, on the complexity of the surgery.

Although one previous series demonstrated a reduction in the need for repeat bypass runs over time (16), in others the rate remained fixed (7). We observed a biphasic evolution of second bypass runs as a result of TEE, with a small incidence at the beginning, a maximum after 4 years, and a clear reduction during the last years in both centers. This evolution is probably multifactorial but might in part be explained by an initial distrust of this new tool by surgeons, followed by acceptance of the new technology and the search for a perfect echo-result, and now by more reasonable expectations. The overzealous attempt to achieve perfect echo-results with each repair is often unnecessary and not always in the patient’s best interest. The difficulty is in differentiating between relevant residual abnormalities requiring further surgery and trivial residual defects. An increase and then a decrease in the incidence of second bypass runs, however, reflects a learning curve among the members of the intraoperative team in their interpretation of postrepair TEE.

TEE played an essential role with regard to changes in medical management in almost 20% of cases. TEE can provide information that is useful in confirming or modifying the anesthetic plan. Optimal preload and afterload or inotropic need as well as their effectiveness can be easily evaluated, but for hemodynamic assessment, TEE is most useful for the adaptation of preload (17). In all cases, anesthesiologists should select some or all of the TEE inputs and combine them with invasive pressure measurements to choose optimal hemodynamic management.

Exclusion of conditions is important for adjusting proper treatment but is a somewhat understated impact of TEE. In our series, TEE helped exclude a diagnosis or surgical complication in 4.9% of cases. This impact was probably underestimated by the way in which data were reported. The exclusion of residual shunts, valve regurgitations, or stenoses suspected by the surgeon was generally not reported because the data sheets allowed the examiners to state only the most relevant impact of TEE for each patient.

The TEE diagnosis leading to surgical revision was confirmed in all patients. A perfect or hemodynamically acceptable result was obtained in close to 80% of cases. These results are in agreement with those of previous studies (7). The decision to return to bypass is not always simple and clear-cut, especially after a complex repair with long ischemic times. In these instances we recommend direct invasive pressure or oximetry measurements. A minority of patients were left with a significant residual defect because new surgical intervention was not considered feasible. Among the 28 patients who left the OR with a significant residual defect, 15 died early postoperatively (6 died after several days of ventricular assistance) and 6 survived after several days under ECMO. Unfortunately, we did no long-term follow-up of those patients with less severe residual defects.

Although we are far from denying the advantage of having an additional echocardiographic specialist exclusively devoted to intraoperative TEE (2,3), such a service appears elusive because of the economic and staff restrictions in most European hospitals. However, in light of the results reported in the literature, including ours, we feel it is essential to offer an echocardiographic service for congenital cardiac surgery. Proper training, a good relationship with an in-house cardiologist experienced in pediatric echocardiography, and full availability of the examiner during the time of TEE examination are the main criteria for maintaining an effective intraoperative TEE service (3). For this last purpose, we think that a second anesthesiologist not involved in the direct care of the patient should be present to perform and interpret the pre- and postoperative TEE studies (2).

The use of TEE in the neonatal population remained small in both centers because we generally maintained a limit of 3.5 kg for routine TEE according to the manufacturer’s recommendations. Our series represents the experience of two moderately busy congenital heart disease programs over the initial years of a pediatric TEE service, and the population in each center is somewhat different: center A recruits a fair number of older children, typically >2 years of age, through a humanitarian organization. Our conclusions should be applied with caution to hospitals with a different patient population and different extent of surgical program. The impact of TEE is highly dependent on the quality of preoperative examinations, the quality of the surgical team, the patient population, and the qualifications of the examiners. Another limitation of our study might be the procedure for data collection. The standardized report forms that were used allowed the examiner to state only the main impact of TEE. We cannot exclude the possibility that some minor impacts and some diagnoses were not reported. However, the incidence of repeat bypass runs was not significantly different between the two centers, demonstrating a consensus. The same is true for the clear-cut third surgical outcome category (expected postoperative difficulties): there were no significant differences between centers or between examiners. Moreover, there is considerable consistency in the reports of TEE surgical impact in the literature as well as in our series despite great differences between center populations and between examiners.

The impact of persistent residual defects has not yet been established; a follow-up study is needed to determine the true TEE-related outcome of congenital heart surgery. The only long-term follow-up variable evaluated in our series was the incidence of reoperation during the time of the study. This affected 5.8% of the patient population; one-third (1.8%) demonstrated defects that might possibly have been diagnosed by TEE during the initial surgery. None of these defects, however, was considered serious enough to require an immediate reoperation in the initial postoperative transthoracic echocardiography examination routinely done by cardiologists. Accordingly, we have no evidence that these reoperations could have been avoided. We should reemphasize that the TEE examiner was in charge exclusively of performing and interpreting the pre- and postoperative TEE studies to avoid diversion from patient care.

	Conclusion

Top Abstract Introduction Methods Results Discussion Conclusion References

 
TEE has a considerable impact in pediatric congenital heart surgery. TEE allows the detection or exclusion of residual defects thought to complicate the postoperative course and long-term follow-up. The need for secondary correction seems to affect over 7% of patients, with a global surgical impact close to 13% and a medical impact of almost 20%. This study establishes that properly trained anesthesiologists can perform these examinations with competence.

	Acknowledgments

 
We thank Hans Rudolf Roth, professor of statistics, from the Swiss Federal Institute of Technology, Zurich, Switzerland, for his invaluable contribution to the statistical analysis.

	Footnotes

 
Presented, in part, at the 24th Annual Meeting of the Society of Cardiovascular Anesthesiologists, April 20–24, 2002, in New York, New York.

	References

Top Abstract Introduction Methods Results Discussion Conclusion References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Bettex, D. A. Articles by Schmid, E. R. Search for Related Content PubMed PubMed Citation Articles by Bettex, D. A. Articles by Schmid, E. R.

Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999