==== Front Ann Card AnaesthAnn Card AnaesthACAAnnals of Cardiac Anaesthesia0971-97840974-5181Medknow Publications & Media Pvt Ltd India 30052211ACA-21-25510.4103/aca.ACA_183_17Original ArticleProspective, Randomized Clinical Trial Comparing use of Intraoperative Transesophageal Echocardiography to Standard Care during Radical Cystectomy Dhawan Richa Shahul Sajid Roberts Joseph Devin Smith Norm D 1Steinberg Gary D 1Chaney Mark A Department of Anesthesia and Critical Care, University of Chicago Medical Center, Chicago, IL, USA1 Department of Surgery/Section of Urology, University of Chicago Medical Center, Chicago, IL, USAAddress for correspondence: Dr. Richa Dhawan, Department of Anesthesia and Critical Care, University of Chicago Medical Center, 5841 South Maryland Ave., MC 4028, Chicago 60637, IL, USA. E-mail: rdhawan@dacc.uchicago.eduJul-Sep 2018 21 3 255 261 Copyright: © 2018 Annals of Cardiac Anaesthesia2018This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.Purpose: Our prospective, randomized clinical study aims to evaluate the utility of intraoperative transesophageal echocardiography (TEE) in patients undergoing radical cystectomy. Materials and Methods: Eighty patients were randomized to a standard of care group or the intervention group that received continuous intraoperative TEE. Data are presented as means ± standard deviations, median (25th percentile, 75th percentile), or numbers and percentages. Characteristics were compared between groups using independent sample t-tests, Wilcoxon–Mann–Whitney tests or Chi-square tests, as appropriate. All tests were two-sided and P < 0.05 was considered to indicate statistical significance. Results: Both groups had similar preoperative demographic characteristics. There was a significant difference between central line insertion with all insertions in the control group (15%, 6 vs. 0%, 0; P < 0.003). Of all the perioperative complications, 80% occurred in the control group versus 20% in the TEE group, with 21% of controls experiencing a cardiac or pulmonary complication compared to 5% in the TEE group (8 vs. 2, P < 0.04). The control group patients were more likely to have adverse cardiac complications than the TEE group (15%, 6 vs. 3%, 1; P < 0.040). Postoperative cardiac arrhythmia was observed only in the control group (13%, 5 vs. 0%, 0; P <.007). Prolonged intubation was only observed in the control group (10%, 4 vs. 0%, 0; P < 0.017). Conclusion: TEE can be a useful monitoring tool in patients undergoing radical cystectomy, limiting the use of central line insertion and potentially translating into earlier extubation and decreased postoperative cardiac morbidities. Echocardiographyfluid therapyradical cystectomytransesophageal ==== Body Introduction Open radical cystectomy represents the most effective treatment for patients with muscle-invasive bladder cancer and is also a viable option for patients with high-grade, nonmuscle invasive disease. Open radical cystectomy can be a very challenging procedure, with published morbidity rates from experienced centers at 27%–45% and perioperative mortality rates at 3%.[12] A major challenge in managing patients undergoing open radical cystectomy is maintaining intraoperative hemodynamic stability. A wide variety of factors contribute, including large blood loss, fluid shifts, inability to accurately assess urine output, and patient factors (preoperative cardiovascular disease/medications, diabetes, hypertension, obesity, and lung disease). Essentially, all patients receive invasive blood pressure monitoring and a substantial percentage of patients undergo central venous pressure (CVP) monitoring to aid intraoperative hemodynamic assessment. Even with such invasive monitoring, maintaining intraoperative hemodynamic stability is challenging and may lead to an increase in perioperative morbidity and mortality.[1] Over the past 20 years, intraoperative transesophageal echocardiography (TEE) has revolutionized the perioperative care of patients undergoing cardiac surgery.[3] It allows direct, accurate assessment of intravascular volume and myocardial contractility, is considered useful in improving clinical outcomes, and the information obtained is better than that obtained from CVP monitoring.[45] At present, no clinical study exists assessing the potential clinical benefits of intraoperative TEE in patients undergoing open radical cystectomy. Our prospective, randomized clinical study aims to evaluate the utility of intraoperative TEE in patients undergoing open radical cystectomy. We hypothesize that when compared to patients without TEE, patients randomized to receive this intraoperative monitoring will exhibit decreased use of invasive venous pressure monitoring, improved intraoperative fluid management, and decreased requirements for intravenous vasoactive medications, which may translate into decreased perioperative complications. Materials and Methods This clinical trial was approved by the institutional review board at our institution and registered at ClinicalTrials.gov (NCT03058250). Patients were enrolled into the study between 2012 and 2014. Written informed consent was obtained by the attending anesthesiologist on the morning of surgery from 80 patients undergoing elective radical cystectomy for invasive bladder cancer and patients were prospectively randomized into one of two groups, control and TEE. Previous clinical investigations have demonstrated that this number of patients will yield statistically significant differences between groups regarding important postoperative complications.[6] Patients were randomized by the statistician using a software program for computer generation of a simple random allocation sequence. Inclusion criteria were all adult (age >18), hemodynamically stable patients undergoing elective radical cystectomy. Exclusion criteria were patient refusal, emergent surgery, preoperative mechanical ventilation, preoperative hemodynamic instability, and esophageal or gastric pathology contraindicating insertion of the TEE probe. If inclusion criteria were met, patients were consented on the day of surgery. All patients, in both the control and TEE group, received a standardized general anesthetic with radial artery blood pressure monitoring, with the goal of tracheal extubation in the operating room immediately following surgery. Anesthetic technique in both groups was standardized to intravenous midazolam, fentanyl, propofol, hydromorphone, vecuronium, and inhaled desflurane in amounts appropriate for intraoperative tracheal extubation. Hemodynamic support for hypotension was standardized to intravenous ephedrine or phenylephrine as first-line agents, at the discretion of the anesthesiologist, followed by other vasopressors (vasopressin and epinephrine) if necessary. In the control group, the attending anesthesiologist was a general anesthesiologist. While TEE was not routinely used in this group, it was allowed if requested by the general anesthesiologist during the intraoperative period in a “rescue” role to evaluate life-threatening hemodynamic instability. Patients in the TEE group had TEE used throughout the intraoperative period to assist with fluid and hemodynamic management. The probe was removed before extubation. The attending anesthesiologist in this group was a cardiac anesthesiologist who had passed the National Board of Echocardiography's Examination of Special Competence in Perioperative TEE. Primary endpoints were intraoperative fluid balance and vasoactive medication use. Secondary endpoints were central line insertion, return of bowel function, tracheal extubation time, postoperative morbidities (pulmonary and cardiac), Intensive Care Unit (ICU) admission, hospital length of stay, and mortality. Statistical analysis We calculated the minimum number of participants required to achieve 80% power at a Bonferroni-adjusted 0.05 significance level using data from a similar study by Pillai et al.[6] All analyses were performed using JMP, version 13, (SAS Institute, Cary, NC, USA). Data are presented as means ± standard deviations, median (25th percentile, 75th percentile) or numbers, and percentages depending on the variable type and distribution. Characteristics were compared between groups using independent sample t-tests, Wilcoxon–Mann–Whitney tests, or Chi-square tests, as appropriate. All tests were two-sided and P < 0.05 was considered to indicate statistical significance. Results Of the 80 patients consented and randomized for the study, 77 had complete data acquisition in the control group (39) and TEE group (38). One patient was lost in the control group due to inadequate intraoperative data collection and inability to insert an arterial line. Two patients were lost in TEE group due to inability to insert a TEE probe and inadequate intraoperative data collection. There were no significant differences in preoperative demographic factors and comorbid conditions between the two groups [Table 1] except more frequent use of statin medications in the TEE group (31%, 12 vs. 58%, 22; P < 0.016). Cardiac, pulmonary, and renal diseases were similarly represented between the two groups. The revised cardiac risk index score was assessed to predict major cardiac complications following elective noncardiac surgery in this population, and it was similar in both groups [Appendix A]. All patients received a minimum score of 1 due to high-risk surgery. Table 1 Patient characteristics Control (n=39) (%) TEE (n=38) (%) P Age (year) 68±10 66±9 0.242 Sex  Male 28 (72) 30 (77) 0.598  Female 11 (28) 8 (21) BMI (kg/m2) 30±12 29±5 0.402 ASA 3 3 >0.999 Revised cardiac risk index score 1.6±0.9 1.7±0.7 0.823 History of smoking 34 (87) 31 (82) 0.497 Hypertension 29 (74) 23 (61) 0.193 Diabetes 12 (31) 13 (34) 0.747 Coronary artery disease 10 (26) 10 (26) 0.946 CHF 4 (10) 8 (21) 0.188 COPD 12 (31) 10 (26) 0.665 Β-blocker 15 (38) 11 (29) 0.376 Calcium channel blocker 12 (31) 8 (21) 0.329 ACE inhibitor 11 (28) 17 (44) 0.130 Diuretics 12 (31) 7 (18) 0.206 Statins 12 (31) 22 (58) 0.016* Nitrates 2 (5) 1 (3) 0.567 Oral hypoglycemic 6 (16) 8 (21) 0.553 Insulin 3 (8) 3 (8) >0.999 Bronchodilator 6 (15) 5 (13) 0.780 Preoperative serum creatinine (mg/dl) 1.3 1.1 0.219 *<0.05 is significant. Data are presented as mean±SD, or absolute value (%). Diabetes defined as treatment with oral hypoglycemic or insulin. TEE: Transesophageal echocardiography, BMI: Body mass index, ASA: American society of anesthesiologists, ACE: Angiotensin-converting enzyme, COPD: Chronic obstructive pulmonary disease, SD: Standard deviation, CHF: Congestive heart failure In both groups, experience of the secondary provider assigned to the case did not differ significantly [Table 2] with residents and nurse anesthetists equally represented between the two groups. Operating room time and length of surgery were similar between the two groups. There was a significant difference between central line insertion for CVP monitoring, with all central line insertions in the control group and none in the TEE group (15%, 6 vs. 0%, 0; P < 0.003). All central line insertions were planned and placed before start of surgery and inserted for the purposes of extra monitoring. There were no statistical differences in intraoperative total blood loss, total intraoperative fluid administration, and transfusion. There were no significant differences with regard to intraoperative vasopressor use in either group. Table 2 Intraoperative data Control (n=39) (%) TEE (n=38) (%) P Provider for case  CRNA 6 (15) 5 (13) 0.927  CA1 20 (51) 21 (55)  CA2 9 (23) 7 (18)  CA3 4 (10) 5 (13) Operating room time (min) 305±101 299±63 0.761 Surgery time (min) 240±83 226±56 0.462 Central venous line insertion (n) 6 (15) 0 0.003* EBL (ml) 1116±951 987±433 0.447 Intraoperative fluids administered (ml)  Crystalloid 4147±1595 3732±1080 0.185  Colloid 615±640 638±437 0.855 Intraoperative transfusion (units)  PRBC 1.8±3.4 0.7±0.9 0.082  FFP/platelets 0.5±1.9 0.05±0.3 0.096 Vasopressor administered (n)  Ephedrine 32 (82) 30 (79) 0.730  Phenylephrine 25 (64) 26 (68) 0.688  Other 7 (18) 3 (8) 0.183 *<0.05 is significant. Data are presented as mean±SD, or absolute value (%). Other vasopressors used were vasopressin and epinephrine. SD: Standard deviation, TEE: Transesophageal echocardiography, CRNA: Certified registered nurse anesthetist, CA1: Clinical anesthesia 1st year, CA2: Clinical anesthesia 2nd year, CA3: Clinical anesthesia 3rd year, EBL: Estimated blood loss, PRBC: Packed red blood cell, FFP: Fresh frozen plasma Myocardial ischemia, new-onset cardiac arrhythmia, respiratory failure, and respiratory distress resulting in reintubation or pulmonary edema that occurred intraoperatively or postoperatively during the hospital stay were all considered to be adverse perioperative events. Of all perioperative complications, 80% occurred in the control group versus 20% in the TEE group, with 21% of controls experiencing a cardiac or pulmonary complication compared to 5% in the TEE group (8 vs. 2, P < 0.04) [Table 3]. Stratifying perioperative complications revealed that the control group patients were more likely to have adverse cardiac complications than the TEE group (15%, 6 vs. 3%, 1; P < 0.040). The incidence of myocardial ischemia was the same in both groups (1 patient in each group), but postoperative cardiac arrhythmia was observed only in the control group (13%, 5 vs. 0%, 0; P <.007). No difference was observed among respiratory complications (8%, 3 vs. 3%, 1; P < 0.30). Table 3 Postoperative outcomes Control (n=39) (%) TEE (n=38) (%) P Perioperative complications 8 (21)Ħ 2 (5) 0.040*  Cardiac 6 (15) 1 (3) 0.041*  Myocardial ischemia 1 (3) 1 (3) 0.985  Cardiac arrhythmia 5 (13) 0 0.007*  Pulmonary 3 (8) 1 (3)ŧ 0.306  Re-intubation 1 (3) 1 (3) 0.985  Pulmonary edema 2 (5) 1 (3) 0.567 Prolonged intubation 4 (10) 0 0.017* ICU admission 7 (18) 3 (8) 0.183 Initial PO intake (POD) 4±2 5±2 0.448 Return of bowel function (POD) 4±2 4±2 0.890 Length of hospital stay (days) 10±8 8±4 0.128 Death (n) 1 (3) Acute kidney failure requiring hemodialysis, respiratory failure and sepsis 0 0.241 *<0.05 is significant. Data are presented as mean±SD or absolute value (%). Data reported as mean±SD was compared using the unpaired t-test, and data reported as number of patients (%) were compared using Pearson Chi-square test. Myocardial ischemia defined by new ST changes and elevated cardiac markers of injury. Cardiac arrhythmia defined as new onset atrial/ventricular arrhythmia documented on EKG, requiring medication/cardiology intervention. Pulmonary edema defined as new onset edema resulting in clinical symptoms (desaturation, labored breathing) documented on CXR requiring medication and/or supportive care. Prolonged intubation defined as the number of patients that remained intubated after the completion of surgery. ĦOne patient had both cardiac and pulmonary complications and is listed in both groups, ŧThis patient had pulmonary edema and was re-intubated and is listed in both groups. SD: Standard deviation, TEE: Transesophageal echocardiography, ICU: Intensive Care Unit, POD: Postoperative day, EKG: Electrocardiogram, CXR: Chest X-ray Prolonged intubation was defined as remaining intubated after the completion of surgery. Prolonged intubation was only observed in the control group (10%, 4 vs. 0%, 0; P < 0.017). Although patients in the control group had more ICU admissions, this did not reach statistical significance (18%, 7 vs. 8%, 3; P < 0.183). There were no differences in the mean number of postoperative days until initial oral intake (4 vs. 5; P < 0.448), return of bowel function (4 vs. 4; P < 0.890), and duration of hospital stay (10 vs. 8; P < 0.128) between the two groups. There was one death in the control group (1 vs. 0; P < 0.241). The patient had 4 l of surgical blood loss, was transfused 15 units of packed red blood cells (PRBCs), had postoperative kidney and respiratory failure, and died on the postoperative day 19. Discussion This prospective, randomized clinical trial found that intraoperative TEE, when compared to the standard of care, was significantly associated with decreased central line insertion, decreased prolonged intubation, and decreased perioperative cardiac arrhythmia. Perioperative complications ranged from pulmonary edema causing respiratory distress to non-ST elevated myocardial infarction requiring coronary artery stent placement. Of all the perioperative complications, 80% occurred in the control group. Postoperative cardiac arrhythmias were only observed in the control group. Four patients had atrial fibrillation with rapid ventricular rate and one patient experienced bradycardia with first-degree atrioventricular block. New-onset cardiac arrhythmias affect about 7% of patients after noncardiac surgery, with atrial fibrillation being the most common.[7] Attenuation of the stress response during surgery may decrease postoperative cardiac irritability. Perioperative fluid management remains challenging and is an abundantly represented topic in the anesthesia and surgery literature.[8910111213141516] Goal-directed treatment (GDT) may lead to fewer complications versus liberal administration of fluid. The term GDT encompasses several varying hemodynamic parameters with an underlying theme of patient specificity to optimize forward flow and perfusion. There is no unifying monitoring modality used in these studies, which range from pulmonary artery catheters to esophageal Doppler (EDM). Although TEE has not been utilized for the purpose of GDT, it provides patient-specific flow directed information such as preload, contractility, and cardiac output. Although there was no difference in total fluids between the two groups, volume administration for cardiac output optimization occurs throughout the surgical case, and total numbers do not reflect variability in administration. Similarly, Goepfert et al. did not find a difference in overall fluid balance or transfusion requirement but found a decrease in postoperative complications in a randomized controlled trial on cardiac surgery patients.[17] The authors concluded that therapeutic intervention based on the cardiac index and end-diastolic volume index is associated with improved end-organ function. In the absence of significant differences in total volume of administered fluid between the treatment and control group, other studies have also found a decrease in postoperative complications with the use of EDM.[1819] Intraoperative EDM-guided fluid therapy has been shown to increase stroke volume, cardiac output, and oxygen delivery when compared to CVP, resulting in a decrease in postoperative complications.[20] In a meta-analysis, Hamilton et al. demonstrated that preemptive hemodynamic monitoring and targeted therapy reduced postoperative morbidity and mortality.[21] The use of intraoperative TEE correlates with these findings, in that better intraoperative monitoring allows targeted intervention throughout the case, likely attenuating large hemodynamic fluctuations. TEE may allow quicker identification of volume depletion and changes in contractility, resulting in immediate management. Ghaferi et al., using data from the American College of Surgeons National Surgical Quality Improvement Program from 2005 to 2007, concluded that complication rates decrease with early recognition and treatment.[22] The noted difference in cardiac complications can likely be attributed to utilization of TEE for timely volume optimization. A meta-analysis of randomized controlled studies by Kern and Shoemaker addressed clinical outcomes in critically ill patients after resuscitation.[23] They reviewed 21 trials and concluded decreased mortality in patients who received early treatment and therapy aimed at optimizing oxygen delivery. Especially, they stated that monitoring aimed at increasing the cardiac index improved outcomes. Interpretation of continuous volumetric and functional data provided by TEE assists with intraoperative optimization of cardiac output. Several large studies have discredited CVP monitoring as useful for clinical decision making for fluid administration.[2425262728] Right atrial pressure does not correlate with volume responsiveness or cardiac output. Despite the abundance of evidence against static CVP monitoring, many clinicians continue to use it to guide therapy.[29] Pulse pressure variation has gained traction since 2000 as a reliable measure of fluid responsiveness; however, it is accurate only in patients on mechanical ventilation with large tidal volumes (>8 ml/kg) and without arrhythmia and does not improve patient outcome.[303132] Venous access for volume resuscitation and monitoring of volume status were the reasons cited by providers for central line insertion in the control group, although all patients had standard peripheral intravenous access. Providers in the intraoperative TEE group were able to rely on echocardiography for monitoring of volume status and were not compelled to place a central line for additional venous access. There is a multitude of immediate and delayed complications associated with central venous access ranging from 4% to 7%.[33] Hemorrhage, stroke, and life-threatening complications have been reported with inadvertent arterial puncture and trauma to surrounding tissues. Ultrasound guidance decreases but does not eliminate the risk of mechanical injury.[34] Alternatively, TEE probe insertion and examination is associated with a very low risk of complications (0.2%–0.5%).[35] Minimal skill is required for probe insertion and knowledge on performing a basic TEE examination can be readily achieved by any provider. Volume assessment and myocardial contractility assessment can be achieved in the mid-esophageal four-chamber view and transgastric short-axis view. In this study, TEE provided a good alternative to central line insertion for monitoring of volume status. Previous studies have indicated that fluid optimization using EDM improved return of gastrointestinal function, decreased length of stay, and improved oral intake.[6] Improvements in postoperative markers of gastrointestinal function were directly correlated to increased fluid administration. Our study did not find a significant difference in postoperative gastrointestinal outcomes, which may be due to no differences between the two groups with regard to mean intraoperative fluid administration. Three out of the four patients with prolonged intubation had 4000 ml of blood loss and received 10, 15, and 12 units of PRBC's, respectively, and were taken to the ICU intubated. The fourth patient had 2000 ml of blood loss but received 10.5 L of intraoperative crystalloid and colloid and was subsequently taken to the ICU intubated. Although there was no statistical significance between mean blood loss between the TEE and control group, no patients in the TEE group had blood loss over 1850 ml. Thus, the increase in prolonged intubation in the control group can likely be attributed to large fluid shifts in 3 out the 4 patients due to blood loss. The fourth patient received fluids in excess of fluid loss and may have benefited from the intraoperative assessment of volume through TEE, which may have led to better optimization of administered fluid. One of the limitations of this study is that only cardiac anesthesiologists certified in TEE were attending physicians for patients in the TEE group. Results of the study may have been effected by choice of anesthesiologist, with cardiac anesthesiologists potentially having increased expertise in managing complex patients.[36] However, given that intraoperative fluid management and vasopressor use was similar between the two groups it is unlikely that patient management styles varied greatly between cardiac and noncardiac anesthesiologists. Rather intraoperative decision-making about timing of fluids and vasopressors based on TEE monitoring, resulted in reduced fluctuations and extremes of hemodynamics, and translated into better outcomes for patients.[37] There was no difference between the control and TEE group among the secondary anesthesia providers. Basic TEE skills to ascertain information on preload and contractility can be attained with minimal training and do not require advanced fellowship training.[38] In addition, providers experienced in TEE can train others in the practice group on basic skills.[39] Conclusion TEE can be a useful monitoring tool in patients with multiple comorbidities undergoing complex surgical procedures with anticipated large blood loss, primarily serving to limit the use of central line insertion and potentially translating into decreased postoperative cardiac morbidities. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. Appendix Appendix A Revised cardiac risk index score History of MI? Yes No MI <6 months? Yes No Current angina? Yes No History of ischemia evaluation? Yes No Current nitroglycerine use? Yes No History of CHF? Yes No History of pulmonary edema? Yes No History of valvular heart disease? Yes No History of cerebrovascular disease? Yes No Use of insulin? Yes No Preoperative rales/S3? Yes No Preoperative abnormal EKG rhythm? Yes No Preoperative Q waves? Yes No Preoperative CXR cardiomegaly? Yes No Serum creatinine >2.0 mg/dl? Yes No Poor general medical status Yes No Ischemic heart disease? Yes No CHF? Yes No MI: Myocardial infarction, CHF: Congestive heart failure, CXR: Chest X-ray, EKG: Electrocardiogram ==== Refs 1 Lowrance WT Rumohr JA Chang SS Clark PE Smith JA Jr Cookson MS Contemporary open radical cystectomy: Analysis of perioperative outcomes J Urol 2008 179 1313 8 18289578 2 Novotny V Hakenberg OW Wiessner D Heberling U Litz RJ Oehlschlaeger S Perioperative complications of radical cystectomy in a contemporary series Eur Urol 2007 51 397 401 16905242 3 Minhaj M Patel K Muzic D Tung A Jeevanandam V Raman J The effect of routine intraoperative transesophageal echocardiography on surgical management J Cardiothorac Vasc Anesth 2007 21 800 4 18068055 4 Memtsoudis SG Rosenberger P Loffler M Eltzschig HK Mizuguchi A Shernan SK The usefulness of transesophageal echocardiography during intraoperative cardiac arrest in noncardiac surgery Anesth Analg 2006 102 1653 7 16717302 5 Practice guidelines for perioperative transesophageal echocardiography. A report by the American Society of Anesthesiologists and the Society of Cardiovascular Anesthesiologists Task Force on Transesophageal Echocardiography Anesthesiology 1996 84 986 1006 8638856 6 Pillai P McEleavy I Gaughan M Snowden C Nesbitt I Durkan G A double-blind randomized controlled clinical trial to assess the effect of Doppler optimized intraoperative fluid management on outcome following radical cystectomy J Urol 2011 186 2201 6 22014804 7 Walsh SR Tang T Wijewardena C Yarham SI Boyle JR Gaunt ME Postoperative arrhythmias in general surgical patients Ann R Coll Surg Engl 2007 89 91 5 17346395 8 VandeHei MS Papageorge CM Murphy MM Kennedy GD The effect of perioperative fluid management on postoperative ileus in rectal cancer patients Surgery 2017 161 1628 32 28139242 9 Chappell D Jacob M Hofmann-Kiefer K Conzen P Rehm M A rational approach to perioperative fluid management Anesthesiology 2008 109 723 40 18813052 10 Grocott MP Mythen MG Gan TJ Perioperative fluid management and clinical outcomes in adults Anesth Analg 2005 100 1093 106 15781528 11 Corcoran T Rhodes JE Clarke S Myles PS Ho KM Perioperative fluid management strategies in major surgery: A stratified meta-analysis Anesth Analg 2012 114 640 51 22253274 12 Jacob M Chappell D Rehm M Clinical update: Perioperative fluid management Lancet 2007 369 1984 6 17574081 13 Brandstrup B Tønnesen H Beier-Holgersen R Hjortsø E Ørding H Lindorff-Larsen K Effects of intravenous fluid restriction on postoperative complications: Comparison of two perioperative fluid regimens: A randomized assessor-blinded multicenter trial Ann Surg 2003 238 641 8 14578723 14 Kehlet H Bundgaard-Nielsen M Goal-directed perioperative fluid management: Why, when, and how? Anesthesiology 2009 110 453 5 19212257 15 Bundgaard-Nielsen M Holte K Secher NH Kehlet H Monitoring of peri-operative fluid administration by individualized goal-directed therapy Acta Anaesthesiol Scand 2007 51 331 40 17390421 16 Abbas SM Hill AG Systematic review of the literature for the use of oesophageal Doppler monitor for fluid replacement in major abdominal surgery Anaesthesia 2008 63 44 51 18086070 17 Goepfert MS Richter HP Zu Eulenburg C Gruetzmacher J Rafflenbeul E Roeher K Individually optimized hemodynamic therapy reduces complications and length of stay in the Intensive Care Unit: A prospective, randomized controlled trial Anesthesiology 2013 119 824 36 23732173 18 Noblett SE Snowden CP Shenton BK Horgan AF Randomized clinical trial assessing the effect of Doppler-optimized fluid management on outcome after elective colorectal resection Br J Surg 2006 93 1069 76 16888706 19 Gan TJ Soppitt A Maroof M el-Moalem H Robertson KM Moretti E Goal-directed intraoperative fluid administration reduces length of hospital stay after major surgery Anesthesiology 2002 97 820 6 12357146 20 Wakeling HG McFall MR Jenkins CS Woods WG Miles WF Barclay GR Intraoperative oesophageal doppler guided fluid management shortens postoperative hospital stay after major bowel surgery Br J Anaesth 2005 95 634 42 16155038 21 Hamilton MA Cecconi M Rhodes A A systematic review and meta-analysis on the use of preemptive hemodynamic intervention to improve postoperative outcomes in moderate and high-risk surgical patients Anesth Analg 2011 112 1392 402 20966436 22 Ghaferi AA Birkmeyer JD Dimick JB Variation in hospital mortality associated with inpatient surgery N Engl J Med 2009 361 1368 75 19797283 23 Kern JW Shoemaker WC Meta-analysis of hemodynamic optimization in high-risk patients Crit Care Med 2002 30 1686 92 12163777 24 Marik PE Cavallazzi R Does the central venous pressure predict fluid responsiveness? An updated meta-analysis and a plea for some common sense Crit Care Med 2013 41 1774 81 23774337 25 Marik PE Baram M Vahid B Does central venous pressure predict fluid responsiveness. A systematic review of the literature and the tale of seven mares? Chest 2008 134 172 8 18628220 26 Osman D Ridel C Ray P Monnet X Anguel N Richard C Cardiac filling pressures are not appropriate to predict hemodynamic response to volume challenge Crit Care Med 2007 35 64 8 17080001 27 Monnet X Marik PE Teboul JL Prediction of fluid responsiveness: An update Ann Intensive Care 2016 6 111 27858374 28 Bentzer P Griesdale DE Boyd J MacLean K Sirounis D Ayas NT Will this hemodynamically unstable patient respond to a bolus of intravenous fluids? JAMA 2016 316 1298 309 27673307 29 Cannesson M Pestel G Ricks C Hoeft A Perel A Hemodynamic monitoring and management in patients undergoing high risk surgery: A survey among North American and European anesthesiologists Crit Care 2011 15 R197 21843353 30 Michard F Boussat S Chemla D Anguel N Mercat A Lecarpentier Y Relation between respiratory changes in arterial pulse pressure and fluid responsiveness in septic patients with acute circulatory failure Am J Respir Crit Care Med 2000 162 134 8 10903232 31 Yang X Du B Does pulse pressure variation predict fluid responsiveness in critically ill patients? A systematic review and meta-analysis Crit Care 2014 18 650 25427970 32 Bendjelid K Romand JA Fluid responsiveness in mechanically ventilated patients: A review of indices used in intensive care Intensive Care Med 2003 29 352 60 12536268 33 Kornbau C Lee KC Hughes GD Firstenberg MS Central line complications Int J Crit Illn Inj Sci 2015 5 170 8 26557487 34 Randolph AG Cook DJ Gonzales CA Pribble CG Ultrasound guidance for placement of central venous catheters: A meta-analysis of the literature Crit Care Med 1996 24 2053 8 8968276 35 Kallmeyer IJ Collard CD Fox JA Body SC Shernan SK The safety of intraoperative transesophageal echocardiography: A case series of 7200 cardiac surgical patients Anesth Analg 2001 92 1126 30 11323333 36 Slogoff S Keats AS Does perioperative myocardial ischemia lead to postoperative myocardial infarction? Anesthesiology 1985 62 107 14 3970360 37 Walsh M Devereaux PJ Garg AX Kurz A Turan A Rodseth RN Relationship between intraoperative mean arterial pressure and clinical outcomes after noncardiac surgery: Toward an empirical definition of hypotension Anesthesiology 2013 119 507 15 23835589 38 Jelacic S Bowdle A Togashi K VonHomeyer P The use of TEE simulation in teaching basic echocardiography skills to senior anesthesiology residents J Cardiothorac Vasc Anesth 2013 27 670 5 23849523 39 Savage RM Licina MG Koch CG Hearn CJ Thomas JD Starr NJ Educational program for intraoperative transesophageal echocardiography Anesth Analg 1995 81 399 403 7618735