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review article return to april 2001 table of contents article de revue total parenteral nutrition in the surgical patient a meta analysis daren k heyland md msc max montalvo md ...

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        Review Article                          Return to April 2001 Table of Contents
        Article de revue
       Total parenteral nutrition in the surgical patient: 
       a meta-analysis
       Daren K. Heyland, MD, MSc;* Max Montalvo, MD;† Shaun MacDonald, MD;* Laurie Keefe, RD;‡ 
       Xiang Yao Su; John W. Drover, MD‡ 
              Objective: To examine the relationship between total parenteral nutrition(TPN) and complication and
              death rates in surgical patients. Data sources: A computer search of published research on MEDLINE,
              personal files and a review of relevant reference lists. Study selection: A review of 237 titles, abstracts or
              papers. Primary studies were included if they were randomized clinical trials of surgical patients that
              evaluated the effect of TPN (compared to no TPN or standard care) on complication and death rates.
              Studies comparing TPN to enteral nutrition (EN) were excluded. Data extraction: Relevant data were
              abstracted on the methodology and outcomes of primary studies. Data were independently abstracted in
              duplicate. Data synthesis: There were 27 randomized trials in surgical patients that compared the use
              of TPN to standard care (usual oral diet plus intravenous dextrose). When the results of these trials were
              aggregated, there was no effect on mortality (risk ratio = 0.97, 95% confidence intervals, 0.76 to 1.24).
              There were fewer major complications in patients who received TPN, although there was significant
              heterogeneity in the overall estimate (risk ratio = 0.81, 95% CI, 0.65 to 1.01). Because of this signifi-
              cant heterogeneity, several a priori hypotheses were examined. Studies that included only malnourished
              patients demonstrated a trend to a reduction in complication rates but no difference in death rate when
              compared with studies of patients who were not malnourished. Studies published in 1988 or earlier and
              studies with a lower methods score were associated with a significant reduction in complication rates
              and a trend to a reduction in death rate when compared with studies published after 1988 and studies
              with a higher methods score. There was no difference in studies that provided lipids as a component of
              TPN when compared with studies that did not. Studies that initiated TPN preoperatively demonstrated
              a trend to a reduction in complication rates but no difference in death rate when compared with studies
              that initiated TPN postoperatively. Conclusions: TPN does not influence the death rate of surgical 
              patients. It may reduce the complication rate, especially in malnourished patients, but study results are
              influenced by methodologic quality and year of publication.
              Objectif : Examiner le lien entre la nutrition parentérale totale (NPT) et les taux de complication et de
              mortalité chez les patients en chirurgie. Sources de données : Recherche informatique dans des
              recherches publiées sur MEDLINE et dans des dossiers personnels, et examen de listes de documents de
              référence pertinents. Sélection d’études : Revue de 237 titres, abrégés ou communications. On a inclus
              des études principales s’il s’agissait d’études cliniques randomisées portant sur des patients en chirurgie
              et qui ont évalué l’effet de la NPT (comparativement à l’absence de NPT ou aux soins normaux) sur les
              taux de complication et de mortalité. On a exclu les études de comparaison de la NPT à l’entéronutri-
              tion. Extraction des données : On a abrégé les données pertinentes sur la méthodologie et les résultats
              des études principales. Les données ont été abrégées de façon indépendante et en double. Synthèse des
              données : Il y avait 27 études randomisées portant sur des patients en chirurgie au cours desquelles on a
              comparé l’utilisation de la NPT aux soins normaux (alimentation orale habituelle et dextrose par voie
              intraveineuse). L’agrégation des résultats de ces études n’a révélé aucun effet sur la mortalité (risque 
              relatif = 0,97; intervalles de confiance à 95 %, 0,76 à 1,24). Il y avait moins de complications majeures
              chez les patients alimentés par NPT, même si l’on a constaté une hétérogénéité importante dans l’esti-
       From the *Department of Medicine and †Department of Surgery, Queen’s University, Kingston, Ont., and ‡Nutritional Services,
       Kingston General Hospital, Kingston, Ont.
       Dr. Heyland is a Career Scientist of the Ontario Ministry of Health.
       Accepted for publication Apr. 3, 2000.
       Correspondence to: Dr. Daren K. Heyland, Angada 3, Kingston General Hospital, 76 Stuart St., Kingston ON  K7L 2V7; fax 613 548-
       2577, dkh2@post.queensu.ca 
       © 2001 Canadian Medical Association
      102 Journal canadien de chirurgie, Vol. 44, No2, avril 2001
                                                                                                                                                             Parenteral nutrition in the surgical patient
                                              mation globale (RR = 0,81; IC à 95 %, 0,65 à 1,01). À cause de cette hétérogénéité importante, on a
                                              examiné plusieurs hypothèses a priori. Des études qui ont porté uniquement sur des patients sous-
                                              alimentés ont démontré une tendance à la réduction des taux de complication, mais aucune différence
                                              au niveau du taux de mortalité comparativement aux études portant sur des patients qui n’étaient pas
                                              sous-alimentés. Par rapport aux études publiées après 1988 et ayant obtenu un résultat méthodologique
                                              plus élevé, les études publiées en 1988 ou antérieurement et les études ayant obtenu un résultat
                                              méthodologique moins élevé affichaient une réduction importante des taux de complication ainsi
                                              qu’une tendance à une réduction du taux de mortalité. On n’a constaté aucune différence dans les
                                              études qui comportaient l’administration de lipides par NPT comparativement aux études qui n’en com-
                                              portaient pas. Les études où on a entrepris la NPT avant l’intervention ont révélé une tendance à la ré-
                                              duction des taux de complication, mais aucune différence au niveau du taux de mortalité comparative-
                                              ment aux études où on a commencé à administrer la NPT après l’intervention. Conclusions : La NPT
                                              n’a pas d’effet sur le taux de mortalité chez les patients en chirurgie. Elle peut réduire le taux de compli-
                                              cation, particulièrement chez les patients sous-alimentés. Les résultats des études varient cependant en
                                              fonction de la qualité de la méthodologie et de l’année de publication.
                                he consequences of major                                                  may be associated with a lower rate                                                • intervention — any form of TPN
                      Tsurgery can lead to hypermetab-                                                    of postoperative complications. Be-                                                       (protein, carbohydrates with or
                       olism and subsequent malnutrition.1,2                                              cause a number of trials have been                                                        without lipids) compared to no
                       The patient’s previous nutritional sta-                                            published subsequent to the meta-                                                         TPN
                       tus, the concomitant or underlying                                                 analysis, we decided to conduct an-                                                • outcome — complications, length
                       disease, and the degree and duration                                               other meta-analysis to summarize the                                                      of hospital stay and mortality.
                       of other stresses can contribute to the                                            current literature.                                                                      We elected to include only ran-
                       risk of malnutrition.3 Malnutrition                                                                                                                                   domized trials in this review because
                       can lead to depletion of body mass,                                                Methods                                                                            studies in which treatment is allocated
                       impaired tissue and organ function,                                                                                                                                   by any other method than randomiza-
                       compromised immunity and poor                                                      Search strategy                                                                    tion tend to show larger (and fre-
                       wound healing. A strong association                                                                                                                                   quently false-positive) treatment ef-
                                                                                                                                                                                                                                                           10
                       exists between malnutrition and in-                                                      We conducted a computerized                                                  fects than do randomized trials.                                 Since
                       creased postoperative morbidity and                                                bibliographic search of MEDLINE                                                    the scope of our review was defined by
                       mortality in surgical patients.4,5                                                 (including pre-MEDLINE) from                                                       our research question, we also ex-
                            The administration of total par-                                              1980 to May 1999 to locate all rele-                                               cluded studies that compared TPN to
                       enteral nutrition (TPN) can clearly                                                vant articles. The terms “randomized                                               enteral nutrition or other forms of
                       prevent the effects of starvation in                                               controlled trial,” “double blind                                                   TPN. Finally, studies that only evalu-
                       patients with a nonfunctioning gas-                                                method,” “clinical trial,” “placebo”                                               ated the impact of TPN on nutritional
                       trointestinal tract. However, it is un-                                            and “comparative study” were com-                                                  outcomes (i.e., nitrogen balance,
                       clear whether TPN can modulate the                                                 bined with “parenteral nutrition, to-                                              amino acid profile) were excluded. Al-
                       catabolic response to surgical stress                                              tal.” Citations were limited to Eng-                                               though these end points may explain
                       and reduce complications associated                                                lish studies reporting on adult                                                    underlying pathophysiology, we con-
                                                                       5                                                                                                                                                                                              11
                       with hypercatabolism. Put differ-                                                  patients. We also searched reference                                               sidered them as surrogate end points,
                       ently, the perioperative administra-                                               lists of relevant review articles and                                              and we only included papers that 
                       tion of TPN may result in significant                                              personal files.                                                                    reported on clinically important out-
                       improvement in weight, nitrogen                                                                                                                                       comes (morbidity and mortality).
                       balance, prealbumin levels and other                                               Selection criteria
                       nutritional end points, but the effect                                                                                                                                Methodologic quality of primary
                       on clinically important end points,                                                      Initially, 2 investigators screened                                          studies
                       such as mortality and complications,                                               all citations and classified them into
                       is less certain. The purpose of this                                               primary studies, review articles or                                                      We assessed the methodologic
                       paper is to systematically review, crit-                                           others. We then retrieved and inde-                                                quality of all selected articles indepen-
                       ically appraise and statistically aggre-                                           pendently reviewed all primary stud-                                               dently in duplicate, according to the
                       gate all studies evaluating the effect                                             ies. They were included in this                                                    scoring system shown in Table 1.
                       of TPN on complication and death                                                   overview if they met the following                                                 Even in randomized trials, failure to
                       rates in surgical patients.                                                        criteria:                                                                          prevent foreknowledge of treatment
                            A number of clinical trials6–8 and a                                          • research design — randomized                                                     assignment can lead to an overestima-
                                                   9                                                                                                                                                                                        12
                       meta-analysis have suggested that                                                         clinical trial                                                              tion of treatment effect.                          Accordingly,
                       preoperative administration of TPN                                                 • population — adult surgical                                                      we scored higher those studies that 
                       in severely malnourished patients                                                         subjects                                                                    reported that their randomization
                                                                                                                                                   Canadian Journal of SurgeryCanadian Journal of Surgery, Vol. 44, No, Vol. 44, No.. 2, April 20012, April 2001       103103
                     Heyland et al
                    schema was concealed. Given the diffi-                                   the apparent effect of the interven-                                            ologic quality of 7 and greater to
                    culties of blinding the administration                                   tions across studies) is often found.                                           those with a score of less than 7
                    of TPN, we only awarded points for                                       When present, heterogeneity weakens                                             (median score = 7).
                    studies that blinded the adjudication                                    any inferences that can be made from                                     • Since the practice of providing
                    of study end points. We also evaluated                                   the results. The possible sources of                                            nutritional support and the man-
                    the extent to which consecutive, eligi-                                  variation include the role of chance or                                         agement of surgical patients has
                    ble patients were enrolled in the trial,                                 differences across studies in popula-                                           evolved over time, we divided the
                    whether groups were equal at baseline,                                   tion, intervention, outcome and                                                 studies into groups comparing
                    if cointerventions were adequately de-                                   methods. A priori, we developed sev-                                            studies published in 1988 or ear-
                    scribed, whether objective definitions                                   eral hypotheses that might explain                                              lier with studies published since
                    of infectious outcomes were employed                                     heterogeneity of study results.                                                 1989 (halfway point of this study
                    and whether all patients were properly                                   • We considered that the premor-                                                period).
                    accounted for in the analysis (inten-                                           bid nutritional status of study                                   • There are several randomized trials
                    tion-to-treat analysis) (Table 1).                                              patients was a possible cause of                                         of surgical patients that examine
                                                                                                    variation in results. Whenever                                           the effect of amino acid infusion
                    Data extraction                                                                 possible we grouped the results                                          alone or in combination with a
                                                                                                    of studies that included only pa-                                        carbohydrate source of calories
                         Two investigators extracted data for                                       tients who were malnourished                                             (without the addition of lipids) 
                    analysis and assessed the methodologic                                          and compared them to the results                                         on clinical outcomes. We hypothe-
                    quality; we resolved disagreement by                                            of studies that included patients                                        sized that there may be some ad-
                    consensus. Not all studies reported                                             who were not malnourished at                                             verse effects from the use of
                    complication rates. Some reported to-                                           the time of entry into the study.                                        lipids.13,14 Accordingly, we sepa-
                    tal complications per group not per                                             When possible, we used the defi-                                         rated trials into those that included
                    patient. When data were missing, un-                                            nition of malnourished provided                                          lipids and those that did not.
                    clear or not reported on a per patient                                          in each individual study. If no de-                               • We speculated that differences in
                    basis, we attempted to contact the pri-                                         finition was provided, we as-                                            the timing of the intervention
                    mary investigators to provide further                                           sumed patients who had greater                                           may account for different results.
                    information if the paper had been                                               than 10% weight loss to be mal-                                          To test this hypothesis we
                    published in the last 5 years.                                                  nourished.                                                               planned a separate analysis com-
                                                                                             • We hypothesized that study                                                    paring studies that initiated TPN
                    Prior hypotheses regarding sources                                              results may be related to the                                            preoperatively to studies that
                    of heterogeneity                                                                methodologic quality of the                                              started TPN postoperatively.
                                                                                                    study. We planned a separate
                         When conducting a meta-analysis,                                           analysis comparing the effect of                                  Analysis
                    heterogeneity (major differences in                                             studies with an overall method-
                                                                                                                                                                           The primary outcome was periop-
                         Table 1                                                                                                                                      erative death (death within 30 days
                                                                                                                                                                      of operation) or death in hospital.
                         Criteria Used to Assess Methodologic Quality                                                                                                 The secondary outcome was major
                                                                                                            Score                                                     complications. We defined major
                         Criterion                                             0                              1                                2                      complications as pneumonia, intra-
                         Randomization                                                          Not concealed or                 Concealed                            abdominal abscess, sepsis,catheter-
                                                                                                not sure                                                              related infection, myocardial infarc-
                         Blinding                                Not blinded                                                     Adjudicators                         tion, pulmonary embolism, heart fail-
                                                                                                                                 blinded                              ure, stroke, renal failure, liver failure
                         Analysis                                Other                                                           Intention-to-treat                   and anastomotic leak. Minor compli-
                         Patient selection                       Selected patients              Consecutive eligible
                                                                 or cannot tell                 patients                                                              cations were defined as wound infec-
                         Comparability of groups                 No or not sure                 Yes                                                                   tion, phlebitis, urinary tract infection
                         at baseline                                                                                                                                  and atelectasis. In 5 studies, the data
                         Extent of follow-up                     <100%                          100%                                                                  were not portrayed in a fashion that
                         Treatment protocol                      Poorly described               Reproducibly
                                                                                                described                                                             allowed us to report major complica-
                         Cointerventions*                        Not described                  Described but not                Well described and                   tion rates so we reported total com-
                                                                                                equal or not sure                all equal                            plications8,15,16 and total infectious
                         Outcomes                                Not described                  Partially described              Objectively defined
                         *The extent to which antibiotics, enteral nutrition, ventilation, oxygen and transfusions were applied equally across groups. For            complications.17,18 There were some
                         questions 1 to 3 and 8 and 9, possible score 0, 1 or 2. For questions 4 to 7, possible score 0 or 1. Total possible score is 14.             studies in which their reporting
               104          Journal canadien de chirurgie, Vol. 44, No2, avril 2001
                                                                                               Parenteral nutrition in the surgical patient
              methods did not allow us to disag-                these potentially eligible papers, 27              malnourished patients, TPN was as-
              gregate infectious from noninfec-                 met the inclusion criteria.6-8,15–21,27–43         sociated with a significant reduction
              tious complications. One study ran-                    There was 100% agreement on                   in complication rates (RR = 0.52,
              domized patients to 3 groups                      the inclusion of articles for this over-           95% CI, 0.30 to 0.91). The RR of
              (control versus standard TPN versus               view. Reasons for excluding relevant               major complications in studies of 
              TPN with branched-chain amino                     randomized studies included studies                patients who were not malnourished
                      19                                                                                  44–46
              acids).   We only included data from              evaluating different kinds of TPN,                 was 0.95 (95% CI, 0.75 to 1.21).
              the control group and the standard                pseudorandomized studies,47–52 dupli-              When we compared the complica-
              TPN group. Two other studies ran-                 cate publications,53,54 studies not re-            tion rates associated with TPN in
              domized patients to 3 groups (con-                porting clinically important out-                  studies of patients who were not
              trol versus TPN without lipids versus             comes,55–57     a study available in               malnourished with the rate in studies
                                                                                       58
              TPN with lipids) and we included                  abstract form only        and a study that         of malnourished patients, the differ-
              both experimental groups in the                   also randomized patients to anabolic               ences were just short of statistical 
                        7,20,21                                            59
              analysis.       We also reported on the           steroids.                                          significance (p = 0.066).
              duration of hospital stay, although                                                                     We compared trials with a meth-
              these data were not aggregated ow-                Impact of total parenteral nutrition               ods score of less than 7 to trials with
              ing to infrequent and variable report-            on death and complication rates                    a score of 7 or better (Fig. 3). Trials
              ing methods. Agreement between                                                                       with the higher methods score
              reviewers on the inclusion of articles                The 27 randomized trials, involv-              demonstrated no effect of TPN on
              was measured by weighted kappa.                   ing 2907 patients, compared the use                mortality (RR = 1.08, 95% CI, 0.81
                 We combined data from all studies              of TPN to standard care (usual oral                to 1.43), whereas trials with a score
              to estimate the common relative risk              diet plus dextrose given intra-                    of 7 or less suggested a trend toward
              of death and complications and asso-              venously) in patients who underwent                a reduction in mortality associated
              ciated 95% confidence intervals (CIs).            surgery.6–8,15–21 The details of each              with the use of TPN (RR = 0.75,
              We summarized the treatment effect                study are described in Table                       95% CI, 0.47 to 1.19). The test for
                                                                   6–8,15–21,27–43
              using risk ratios (RRs). To avoid the             2.             When the results of these           heterogeneity across subgroups was
              problem with bias and instability as-             trials were aggregated, there was no               not significant (p = 0.21). With re-
              sociated with RR estimation in sparse             effect on mortality (RR = 0.97, 95%                spect to complication rates, in studies
                                                          22
              data, we added one-half to each cell.             CI, 0.76 to 1.24) (Fig. 1). The test               with a higher methods score there
              In the meta-analysis, we used maxi-               for heterogeneity was not significant              was no effect of TPN on major com-
              mum likelihood methods of combin-                 although a visual inspection suggests              plications (RR = 1.07, 95% CI, 0.86
              ing RRs across all trials and examined            that the treatment effect of some of               to 1.32). In studies with a lower
              the data for evidence of heterogeneity            the studies was significantly different            methods score, there was a significant
              within groups.23           The Mantel–            from other studies. Twenty-two                     reduction in complication rates (RR
              Haenzel method was used to test the               studies reported major complica-                   = 0.50, 95% CI, 0.32 to 0.76). The
                                                     24
              significance of treatment effect.         We      tions. When these results were aggre-              test for heterogeneity across sub-
              used a random effects model to esti-              gated, TPN was associated with a re-               groups was significant (p = 0.005).
              mate the overall RR.25,26 For the test            duction in complication rates (RR =                   We next compared trials pub-
              of heterogeneity across subgroups,                0.81, 95% CI, 0.65 to 1.01, p =                    lished in 1988 or earlier with studies
              the t-test for the difference between             0.06) (Fig. 2). The test for hetero-               published since 1989 (see Fig. 3).
              the 2 subgroups was used. We con-                 geneity was significant (p = 0.01).                Trials published in 1988 or earlier
              sidered a p value of less than 0.05 to                Given that we found significant                were associated with a trend toward
              be statistically significant.                     heterogeneity and in an attempt to                 a decrease in death rates associated
                                                                better explain our findings, we exam-              with the use of TPN (RR = 0.68,
              Results                                           ined our a priori hypotheses. We                   95% CI, 0.43 to 1.10). Trials pub-
                                                                compared those trials that included                lished since 1989 were consistent
              Study identification and selection                only malnourished patients with                    with no treatment effect associated
                                                                other trials. TPN was not associated               with TPN (RR = 1.11, 95% CI, 0.83
                 In all 187 citations were identified           with any difference in mortality  to 1.48). The test for heterogeneity
              from the MEDLINE databases. Our                   (Fig. 3) in studies of malnourished                across subgroups was short of con-
              personal files and review of reference            patients (RR = 1.13, 95% CI, 0.75 to               ventional levels of significance (p =
              lists yielded 57 additional articles for          1.71) or in studies of normally nour-              0.10). With respect to complication
              consideration. Initial eligibility                ished patients (RR = 0.90, 95% CI,                 rates, in studies published in 1988 or
              screening resulted in 47 articles se-             0.66 to 1.21, p = 0.38 for differences             earlier there was a significant reduc-
              lected for further evaluation. Of                 between subgroups). In studies of                  tion in major complications associ-
                                                                                         Canadian Journal of Surgery, Vol. 44, No.2, April 2001                 105
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...Review article return to april table of contents de revue total parenteral nutrition in the surgical patient a meta analysis daren k heyland md msc max montalvo shaun macdonald laurie keefe rd xiang yao su john w drover objective examine relationship between tpn and complication death rates patients data sources computer search published research on medline personal files relevant reference lists study selection titles abstracts or papers primary studies were included if they randomized clinical trials that evaluated effect compared no standard care comparing enteral en excluded extraction abstracted methodology outcomes independently duplicate synthesis there use usual oral diet plus intravenous dextrose when results these aggregated was mortality risk ratio confidence intervals fewer major complications who received although significant heterogeneity overall estimate ci because this signifi cant several priori hypotheses examined only malnourished demonstrated trend reduction but dif...

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