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Department of Anesthesiology, Division of Liver Transplant Anesthesia, Tufts–New England Medical Center, Boston, Massachusetts
Address correspondence and reprint requests to Roman Schumann, MD, Tufts–New England Medical Center, Department of Anesthesiology, #298, 750 Washington St., Boston, MA 02111. Address e-mail to RSchumann{at}tufts-nemc.org
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Abstract |
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IMPLICATIONS: Currently no comprehensive data are available describing the intraoperative use of laboratory tests, personnel, infusion and perfusion equipment, monitoring technology, and veno-venous bypass by liver transplantation programs. These postal survey results provide an overview of utilization of these resources in anesthesia for liver transplantation.
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Introduction |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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Methods |
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Not permitting responder identification, the survey addressed, in a checklist format, three categories of resources that a transplantation center might routinely use during LT. These categories were personnel, laboratory testing, and technologies for rapid infusion, hemodynamic monitoring, and maintenance (veno-venous bypass (VVBP)). Respondents were asked to select choices to the questions described below. Data collection included the number of adult and pediatric LTs, as well as living-donor LTs, in all ages performed in the 12 mo preceding the survey.
The objectives of the study were to determine the nature and extent of resources used in anesthesia for LT in general, as well as the effect of an adult versus pediatric recipient population and of the annual case volume on intraoperative resource utilization patterns. Pooled responses were analyzed in aggregate, as well as in six subgroups.
Statistical analysis (SAS 8.1; SAS Institute, Cary, NC) was performed with the nonparametric Wilcoxon test for continuous variables and the two-sided Fisher’s exact test for categorical variables between subgroups. For trend analysis, the Cochran-Armitage tests with exact P values for categorical variables were used, and the nonparametric Kruskal-Wallis test was applied when groups characterized by LT frequency were simultaneously compared. All tests were two sided. A P value <0.05 was considered statistically significant.
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Results |
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The participating programs in aggregate completed 3318 LTs. This figure corresponds to 64% of LTs performed nationally in a similar time frame, on the basis of Organ Procurement and Transplantation Network (OPTN) statistics for 2001. When compared with the 2001 OPTN data, these centers performed 62.3% (n = 2895) of adult, 47.3% (n = 193) of adult living donor, 71% (n = 423) of pediatric, and 85.7% (n = 90) of the living-donor pediatric LTs. One center was identified as private, whereas another was academic with a nonacademic anesthesia department; both performed adult LTs.
LT programs were separated by their respective recipient population into adult only, pediatric only, and programs that performed both adult and pediatric LTs. No age limit to distinguish between adults and pediatrics was suggested by the survey form, and the definition remained with the responding program. Among the participating centers, 30 (48%), 13 (21%), and 19 (31%) performed adult only, pediatric only, or both adult and pediatric LTs, respectively. However, adult LTs occurred in 49 (79%) centers, and pediatric LT was performed in 32 (51.6%) programs. Figure 1A illustrates the annual frequency of pediatric LTs performed in centers that provided this procedure.
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Figure 1B shows the volume of LTs performed per year (mean ± SD) by the surveyed programs and their subgroups. There was a statistically significant difference between adult-only, pediatric-only, and mixed-age programs in the annual caseload.
Of all 49 programs performing adult LT, 28 (57%) also performed adult living-donor LTs. Among adult-only centers, 15 (50%) performed living-donor LTs, whereas 13 (68.4%) mixed-age programs performed adult living-donor LTs.
Of all 32 centers performing pediatric LT, 23 (72%) also performed living-donor pediatric LTs. Living-donor pediatric LT took place in 9 (69%) pediatric-only and 14 (73.7%) mixed-age programs. A trend for an increased proportion of adult living-donor LTs with increasing annual LT frequency did not reach statistical significance.
Coagulation variables typically monitored during the LT are summarized in Figure 2, A and B. The measurement of one or more of prothrombin time, international normalized ratio, partial thromboplastin time, fibrinogen, and D-dimer was considered as a single answer: traditional coagulation studies (TCS). Other tests surveyed were platelets (Plts), activated clotting time, thrombelastogram (TEG®), "other," and "none of the above." Two (6.5%) centers did not use any of the suggested studies. Another two programs used unspecified "other" tests. As their sole intraoperative assessment of coagulation, two centers used the TEG®, and another two used Plts. Pediatric-only programs always monitored Plts and TCS. Whereas the trend for decreased use of activated clotting time with increasing annual LT frequency was statistically significant, a similar trend for TCS use was not.
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To assess the typically available personnel within the anesthesia team and ancillary operating room personnel, excluding nurses, nine answer options were provided. The anesthesiologist, anesthesia fellow, anesthesia resident, a certified registered nurse anesthetist (CRNA), and a student registered nurse anesthetist were considered anesthesia personnel. A perfusionist, cell-saver personnel, rapid transfusion device operator, and "other" were considered ancillary personnel. Where indicated by the surveyed program, personnel providing multiple functions were counted as one person only, in the category of their highest education; i.e., a perfusionist functioning also as a cell saver and a rapid transfusion device operator would count as a perfusionist. Table 1 illustrates the type and number of personnel available during an LT. An anesthesia technician was available in 11.3% of all institutions. There was a tendency for less use of ancillary personnel in pediatric-only centers. These centers use anesthesia fellows significantly more often and use perfusionists significantly less frequently than adult-only or mixed-age centers, and they seldom use CRNAs. A trend to use more fellows and CRNAs in centers with larger caseloads was not statistically significant.
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Discussion |
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However, no data in the literature yet describe the current intraoperative use of resources in anesthesia for LT from a large cross-section of national LT programs. To lessen the respondents’ burden and to avoid probing of potentially sensitive data, whose collection might decrease the response rate, our data collection process did not ask about clinical outcomes or direct costs. A survey by Merritt in 1997 (4) correlating practice patterns and anesthesia-related costs was based on responses of only 13 LT centers. The large response rate to our survey indicates an interest in this information in the anesthesia LT community. Nevertheless, the small sample size of the subgroups prevented data and trend analysis for utilization of several resources to reach statistically significant differences between groups.
On the basis of OPTN data for 2001, proportionally more pediatric than adult LTs were captured in this survey. The volume of pediatric LTs per center in the survey was consistently small, reflecting that only approximately 10% of all LTs per year occur in this recipient population. Of all programs performing pediatric LTs, less than half were dedicated to pediatrics only. A larger number of adult and pediatric living-donor LTs occurred in centers serving both adults and children. These centers also had a significantly larger annual caseload of LTs than pediatric-only or adult-only programs. This suggests a correlation between LT frequency in general and performing living-donor LTs, which may reflect greater experience, infrastructure, referral base, and surgical aggressiveness of these centers.
Coagulopathy occurring during LT can be extremely complex and dynamic. Almost all centers use combinations of coagulation studies to guide intraoperative blood product replacement therapy. Although a variety of blood tests are available, the value of TEG® during LT as a test of whole-blood coagulation, which also permits the detection of hypercoagulability, has been established in the literature (6–8). However, TEG® was used only by a third of all programs, and only two centers relied on TEG® alone. Pediatric-only centers relied on TCS and Plts. No coagulation testing of any kind was reported by 6.5% of all programs, which is difficult to interpret. It may reflect that in these two centers such monitoring is done by others and is thus not under the respondent’s purview. Reliance on clinical monitoring alone or a respondent oversight could also explain this finding.
All LT centers routinely monitored electrolytes, blood gases, and the blood glucose levels during surgery. Citrate contained in blood products binds ionized calcium but is rapidly metabolized by the healthy liver. It is well recognized that ionized calcium may decrease precipitously during rapid intraoperative transfusion or during the anhepatic stage (9–11). Most programs and all of the pediatric-only centers routinely monitor calcium levels. Centers that do not routinely monitor calcium might instead empirically replace it, without titrating according to the ionized calcium level.
End-stage liver disease can be accompanied by baseline hypomagnesemia. Ionized magnesium behaves similar to ionized calcium during LT because of its chelation by citrate (11). Because ionized hypomagnesemia is not uncommon, it may contribute to cardiac dysrhythmias (12). Despite the literature suggesting its monitoring and supplementation if needed (12–14), only 51.6% of the programs monitored magnesium, a proportion that appeared to decrease with increasing LT caseload. Most centers, and all large-volume centers, used a satellite laboratory with a turnaround time of five minutes or less, mostly for blood gases and electrolytes. This use may reflect the need for fast and reliable metabolic monitoring during surgery, independent of a large central hospital laboratory with its possible delays.
Personnel deployed during LT are substantial in most centers (3). In this survey, the predominant mode of personnel use in LTs was that of two anesthesia providers and two ancillary personnel. The complexity of surgery and its preponderance mostly in academic centers captured in this survey may explain these results to some extent. However, there was large between-center variation in the number of personnel made available during LTs. A tendency was recognizable for use of more anesthesia providers and fewer ancillary personnel in pediatric-only centers. This observation may be explained by a reduced need for VVBP and large-volume fluid administration in this population. As can be expected, anesthesia fellows were significantly more frequently present in centers performing pediatric-only LTs. Fellows were also more frequently present in large-volume LT centers.
Routine use of high-tech, large-volume infusion equipment was common. Such technologies include the RIS, the FMS 2000, the Level 1, and perfusion equipment. All of these systems are capable of rapidly warming and delivering large fluid volumes (500–1500 mL/min, depending on the model) and do use costly disposables. The RIS, the FMS 2000, and the perfusion pump use roller pump technology for fluid propulsion, whereas the Level 1 uses inflatable pressure chambers. Pediatric-only centers have less need for rapid large-volume infusion, explaining their reduced utilization of these technologies.
The usefulness and safety of TEE for hemodynamic monitoring and management during LT has been described in the literature (15–17). Only 11.3% of all centers used TEE. This infrequent use may reflect the relative unavailability of TEE, as well as unfamiliarity with its use. The nature and distribution of specific diagnoses in the recipient population that a program might serve, as well as a center’s academic or nonacademic status, might further influence routine TEE use.
In contrast, CCO pulmonary artery catheters were used by >30% of programs. A study by Greim et al. (18) reported logistical advantages and possibly improved measurement accuracy of hemodynamic variables when CCO versus conventional cardiac output determinations was used. However, CCO use appears to decrease with increasing LT frequency.
Half of all adult LT centers and 37% of all programs routinely used VVBP. Utilization of this extracorporeal circuit decreased with increasing LT volume. Advances in surgical experience and technique, namely, the "piggy-back" method instead of complete vena cava cross-clamping when the donor liver is inserted, may decrease the future need for VVBP (19,20).
Concern about the accuracy of the radial arterial blood pressure compared with central blood pressure during hemodynamic instability (21,22), as well as the need for frequent blood sampling, may explain the relatively large number of programs that used more than one arterial line during surgery. Large-volume centers lead in the use of this resource. Interestingly, routine BIS monitoring was also increased in centers with a large LT frequency. An effect of the recipient population on its use was less clear.
When these results are interpreted, consideration should be given to the limitations of this survey. Its accuracy may be impaired because of collection and respondent factors, such as ascertainment (23) or nonresponse (24) bias. Although sent to directors of LT anesthesia or anesthesia department chairs, the anonymous nature of the responses excludes validation of the expertise of the person completing the questionnaire. Ensuring anonymity of responding programs still may not guard sufficiently against the respondents inferring an existing standard of care from the answers offered in the questionnaire itself and against distortion of the participants’ responses. The distribution of specific pathologies among the recipient population of a program and its donor and organ acceptance criteria might influence the routine use of resources, but these were not evaluated in this survey. Finally, almost all questionnaires were returned from academic LT centers, preventing a comparison between academic and nonacademic (e.g., private practice) programs. Rather than be required for routine patient care, some of the resources allocated in the former programs may be used to further education and research. Hence, these results should not be construed as defining a standard of care.
In conclusion, this study provides a broad national overview of the utilization of anesthesia and ancillary resources involved in the intraoperative care of the LT patient in academic LT centers. An adult versus pediatric recipient population and the annual case volume of an LT center significantly influence the routine resources used. Including data from more nonacademic LT programs is necessary to then relate resources to outcomes and begin to integrate these practices into an evidence-based framework for future studies.
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Acknowledgments |
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References |
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2 distribution and P = 0.06 on Fisher’s exact test). xUse of the suggested devices was significantly less in pediatric-only versus adult-only and mixed-age centers with Fisher’s exact test (P < 0.05).
