Oxygen delivery is an important predictor of outcome in patients with ruptured abdominal aortic aneurysms

Personalizing patient risk of a life-altering event: An application of machine learning to hemiarch surgery

OBJECTIVE

The study objective was to assess a machine learning model's ability to predict the occurrence of life-altering events in hemiarch surgery and determine contributing patient characteristics and intraoperative factors.

METHODS

In total, 602 patients who underwent hemiarch replacement at a high-volume aortic center from 2009 to 2022 were included. Patients were randomly divided into training (80%) and testing (20%) sets with various eXtreme gradient boosting candidate models constructed to predict the risk of experiencing life-altering events, including stroke, mortality, or new renal replacement therapy requirement. A total of 64 input parameters from the index hospitalization were identified, including 24 demographic characteristics as well as 8 preoperative and 32 intraoperative variables. A SHapley Additive exPlanation beeswarm plot was generated to identify and interpret the impact of individual features on the predictions of the final model.

RESULTS

A life-altering event was noted in 15% (90/602) of patients who underwent hemiarch replacement, including urgent/emergency cases and dissections. The final eXtreme Gradient Boosting model demonstrated a cross-validation accuracy of 88% on the testing set and was well calibrated as evidenced by a low Brier score of 0.12. The best performing model achieved an area under the receiver operating characteristic curve of 0.76 and an area under the precision recall curve of 0.55. The SHapley Additive exPlanation beeswarm plot provided insights into key features that significantly influenced model prediction.

CONCLUSIONS

Machine learning demonstrated superior accuracy in predicting hemiarch patients who would experience a life-altering event. This model may help to guide patients and clinicians in stratifying risk on an individual basis, which may in turn influence clinical decision-making.

Proteomic signatures for perioperative oxygen delivery in skin after major elective surgery: mechanistic sub-study of a randomised controlled trial

BACKGROUND

Maintaining adequate oxygen delivery (DO₂) after major surgery is associated with minimising organ dysfunction. Skin is particularly vulnerable to reduced DO₂. We tested the hypothesis that reduced perioperative DO₂ fuels inflammation in metabolically compromised skin after major surgery.

METHODS

Participants undergoing elective oesophagectomy were randomised immediately after surgery to standard of care or haemodynamic therapy to achieve their individualised preoperative DO₂. Abdominal punch skin biopsies were snap-frozen before and 48 h after surgery. On-line two-dimensional liquid chromatography and ultra-high-definition label-free mass spectrometry was used to characterise the skin proteome. The primary outcome was proteomic changes compared between normal (≥preoperative value before induction of anaesthesia) and low DO₂ (<preoperative value before induction of anaesthesia) after surgery. Secondary outcomes were functional enrichment analysis of up/down-regulated proteins (Ingenuity pathway analysis; STRING Protein-Protein Interaction Networks). Immunohistochemistry and immunoblotting confirmed selected proteomic findings in skin biopsies obtained from patients after hepatic resection.

RESULTS

Paired punch skin biopsies were obtained from 35 participants (mean age: 68 yr; 31% female), of whom 17 underwent oesophagectomy. There were 14/2096 proteins associated with normal (n=10) vs low (n=7) DO₂ after oesophagectomy. Failure to maintain preoperative DO₂ was associated with upregulation of proteins counteracting oxidative stress. Normal DO₂ after surgery was associated with pathways involving leucocyte recruitment and upregulation of an antimicrobial peptidoglycan recognition protein. Immunohistochemistry (n=6 patients) and immunoblots after liver resection (n=12 patients) supported the proteomic findings.

CONCLUSIONS

Proteomic profiles in serial skin biopsies identified organ-protective mechanisms associated with normal DO₂ after major surgery.

CLINICAL TRIAL REGISTRATION

ISRCTN76894700.

Changes in the sublingual microcirculation following aortic surgery under balanced or total intravenous anaesthesia: a prospective observational study

Background

In vascular surgery with aortic cross-clamping, ischemia/reperfusion injury induces systemic haemodynamic and microcirculatory disturbances. Different anaesthetic regimens may have a varying impact on tissue perfusion. The aim of this study was to explore changes in microvascular perfusion in patients undergoing elective open abdominal aortic aneurysm repair under balanced or total intravenous anaesthesia.

Methods

Prospective observational study. Patients undergoing elective open infrarenal abdominal aortic aneurysm repair received balanced (desflurane + remifentanil, n = 20) or total intravenous anaesthesia (TIVA, propofol + remifentanil using target-controlled infusion, n = 20) according to the clinician’s decision. A goal-directed haemodynamic management was applied in all patients. Measurements were obtained before anaesthesia induction (baseline) and at end-surgery and included haemodynamics, arterial/venous blood gases, sublingual microvascular flow and density (incident dark field illumination imaging), peripheral muscle tissue oxygenation and microcirculatory reactivity (thenar near infrared spectroscopy with a vascular occlusion test).

Results

The two groups did not differ for baseline characteristics, mean aortic-clamping time and requirement of vasoactive agents during surgery. Changes in mean arterial pressure, systemic vascular resistance index, haemoglobin and blood lactate levels were similar between the two groups, while the cardiac index increased at end-surgery in patients undergoing balanced anaesthesia. The sublingual microcirculation was globally unaltered in the TIVA group at end-surgery, while patients undergoing balanced anaesthesia showed an increase in the total and perfused small vessel densities (from 16.6 ± 4.2 to 19.1 ± 5.4 mm/mm², p < 0.05). Changes in microvascular density were negatively correlated with changes in the systemic vascular resistance index. The area of reactive hyperaemia during the VOT increased in the balanced anaesthesia group (from 14.8 ± 8.1 to 25.6 ± 14.8%*min, p < 0.05). At end-surgery, the tissue haemoglobin index in the TIVA group was lower than that in the balanced anaesthesia group.

Conclusions

In patients undergoing elective open abdominal aortic aneurysm repair with a goal-directed hemodynamic management, indices of sublingual or peripheral microvascular perfusion/oxygenation were globally preserved with both balanced anaesthesia and TIVA. Patients undergoing balanced anaesthesia showed microvascular recruitment at end-surgery.

Trial registration

NCT03510793, https://www.clinicaltrials.gov, date of registration April 27th 2018, retrospectively registered.

Low values of central venous oxygen saturation (ScvO2) during surgery and anastomotic leak of abdominal trauma patients

Background

There is a well known relationship between hypoperfusion and postoperative complications like anastomotic leak. No studies have been done addressing this relationship in the context of abdominal trauma surgery. Central venous oxygen saturation is an important hypoperfusion marker of potential use in abdominal trauma surgery for identifying the risk of anastomotic leak development. The purpose of this study was to identify the relationship between low values of central venous oxygen saturation and anastomotic leak of gastrointestinal sutures in the postoperative period in abdominal trauma surgery.

Methods

A cross-sectional prospective study was performed. Patients over 14 years old who required surgical gastrointestinal repair secondary to abdominal trauma were included. Anastomotic leak diagnosis was confirmed through clinical manifestations and diagnostic images or secondary surgery when needed. Central venous oxygen blood saturation was measured at the beginning of surgery through a central catheter. Demographic data, trauma mechanism, anatomic site of trauma, hemoglobin levels, abdominal trauma index, and comorbidities were assessed as secondary variables.

Results

Patients who developed anastomotic leak showed lower mean central venous oxygen saturation levels (60.0% ± 2.94%) than those who did not (69.89% ± 7.21%) (p = 0.010).

Conclusions

Central venous oxygen saturation <65% was associated with the development of gastrointestinal leak during postoperative time of patients who underwent surgery secondary to abdominal trauma.

The UK Cardiac and Vascular Surgery Interventional Anaemia Response (CAVIAR) Study: protocol for an observational cohort study to determine the impact and effect of preoperative anaemia management in cardiac and vascular surgical patients

INTRODUCTION

Preoperative anaemia is linked to poor postsurgical outcome, longer hospital stays, greater risk of complications and mortality. Currently in the UK, some sites have developed anaemia clinics or pathways that use intravenous iron to correct iron deficiency anaemia prior to surgery as their standard of care. Although intravenous iron has been observed to be effective in a variety of patient settings, there is insufficient evidence in its use in cardiac and vascular patients. The aim of this study is to observe the impact and effect of anaemia and its management in patients undergoing cardiac and vascular surgery. In addition, the UK Cardiac and Vascular Surgery Interventional Anaemia Response (CAVIAR) Study is also a feasibility study with the aim to establish anaemia management pathways in the preoperative setting to inform the design of future randomised controlled trials.

METHODS AND ANALYSIS

The UK CAVIAR Study is a multicentre, stepped, observational study, in patients awaiting major cardiac or vascular surgery. We will be examining different haematological variables (especially hepcidin), functional capacity and patient outcome. Patients will be compared based on their anaemia status, whether they received intravenous iron in accordance to their hospital's preoperative pathway, and their disease group. The primary outcomes are the change in haemoglobin levels from baseline (before treatment) to before surgery; and the number of successful patients recruited and consented (feasibility). The secondary outcomes will include changes in biomarkers of iron deficiency, length of stay, quality of life and postoperative recovery.

ETHICS AND DISSEMINATION

The study protocol was approved by the London-Westminster Research Ethics Committee (15/LO/1569, 27 November 2015). NHS approval was also obtained with each hospital trust. The findings of the study will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

Clinical Trials registry (NCT02637102) and the ISRCTN registry (ISRCTN55032357).

Preoperative Anemia in Hindfoot and Ankle Arthrodesis

This is a retrospective study (n = 39) evaluating the postoperative outcomes of patients with mild to moderate preoperative anemia who underwent a hindfoot and/or ankle arthrodesis. In the study, 32 patients did not have preoperative anemia, and 7 had preoperative anemia. Mortality, length of hospital stay, blood transfusions, deep-vein thrombosis, infection, time to union, malunion, delayed union, nonunion, and ulceration were of particular interest. Comparative analyses between patients with preoperative anemia and those without were performed utilizing the independent samples t-test or by the nonparametric Mann-Whitney U-test. The Fisher exact test was used to analyze categorical data. The Shapiro-Wilk test was utilized to check normality. Statistical significance was defined at a 2-sided level of P <.05. Delayed union, nonunion, and malunion were all significantly increased in patients with preoperative anemia (P = .032, P = .004, and P = .028, respectively). Accordingly, the median total number of noninfectious complications (delayed union + nonunion + malunion) in patients with preoperative anemia (0.86 ± 0.38) was significantly higher than in patients without preoperative anemia (0.063 ± 0.25; P < .001). Patients with preoperative anemia had a significantly longer length of hospital stay in days (4.14 ± 2.61). Total infection was also significantly associated with preoperative anemia (P = .001). This study clearly demonstrated that infectious complications, noninfectious complications, and length of hospital stay in hindfoot and/or ankle arthrodesis was significantly affected by preoperative anemia. Thus, consideration should be given to addressing preoperative anemia prior to hindfoot and/or ankle arthrodesis.

LEVELS OF EVIDENCE

Level II Study.

Pre-operative anaemia

Pre-operative anaemia is a relatively common finding, affecting a third of patients undergoing elective surgery. Traditionally associated with chronic disease, management has historically focused on the use of blood transfusion as a solution for anaemia in the peri-operative period. Data from large series now suggest that anaemia is an independent risk associated with poor outcome in both cardiac and non-cardiac surgery. Furthermore, blood transfusion does not appear to ameliorate this risk, and in fact may increase the risk of postoperative complications and hospital length of stay. Consequently, there is a need to identify, diagnose and manage pre-operative anaemia to reduce surgical risk. Discoveries in the pathways of iron metabolism have found that chronic disease can cause a state of functional iron deficiency leading to anaemia. The key iron regulatory protein hepcidin, activated in response to inflammation, inhibits absorption of iron from the gastrointestinal tract and further reduces bioavailability of iron stores for red cell production. Consequently, although iron stores (predominantly ferritin) may be normal, the transport of iron either from the gastrointestinal tract or iron stores to the bone marrow is inhibited, leading to a state of 'functional' iron deficiency and subsequent anaemia. Since absorption from the gastrointestinal tract is blocked, increasing oral iron intake is ineffective, and studies are now looking at the role of intravenous iron to treat anaemia in the surgical setting. In this article, we review the incidence and impact of anaemia on the pre-operative patient. We explain how anaemia may be caused by functional iron deficiency, and how iron deficiency anaemia may be diagnosed and treated.

Influence of early goal-directed therapy using arterial waveform analysis on major complications after high-risk abdominal surgery: study protocol for a multicenter randomized controlled superiority trial

Background

Early goal-directed therapy refers to the use of predefined hemodynamic goals to optimize tissue oxygen delivery in critically ill patients. Its application in high-risk abdominal surgery is, however, hindered by safety concerns and practical limitations of perioperative hemodynamic monitoring. Arterial waveform analysis provides an easy, minimally invasive alternative to conventional monitoring techniques, and could be valuable in early goal-directed strategies. We therefore investigate the effects of early goal-directed therapy using arterial waveform analysis on complications, quality of life and healthcare costs after high-risk abdominal surgery.

Methods/Design

In this multicenter, randomized, controlled superiority trial, 542 patients scheduled for elective, high-risk abdominal surgery will be included. Patients are allocated to standard care (control group) or early goal-directed therapy (intervention group) using a randomization procedure stratified by center and type of surgery. In the control group, standard perioperative hemodynamic monitoring is applied. In the intervention group, early goal-directed therapy is added to standard care, based on continuous monitoring of cardiac output with arterial waveform analysis. A treatment algorithm is used as guidance for fluid and inotropic therapy to maintain cardiac output above a preset, age-dependent target value. The primary outcome measure is a combined endpoint of major complications in the first 30 days after the operation, including mortality. Secondary endpoints are length of stay in the hospital, length of stay in the intensive care or post-anesthesia care unit, the number of minor complications, quality of life, cost-effectiveness and one-year mortality and morbidity.

Discussion

Before the start of the study, hemodynamic optimization by early goal-directed therapy with arterial waveform analysis had only been investigated in small, single-center studies, including minor complications as primary endpoint. Moreover, these studies did not include quality of life, healthcare costs, and long-term outcome in their analysis. As a result, the definitive role of arterial waveform analysis in the perioperative hemodynamic assessment and care for high-risk surgical patients is unknown, which gave rise to the present trial. Patient inclusion started in May 2012 and is expected to end in 2016.

Trial registration

This trial was registered in the Dutch Trial Register (registration number NTR3380) on 3 April 2012.

Electronic supplementary material

The online version of this article (doi:10.1186/1745-6215-15-360) contains supplementary material, which is available to authorized users.

Haemoglobin concentration and mass as determinants of exercise performance and of surgical outcome

The ability of the cardiorespiratory system (heart, lungs, blood) to deliver oxygen to exercising skeletal muscle constrains maximum oxygen consumption V˙O2max, with cardiac output and the concentration of oxygen-carrying haemoglobin ([Hb]) being key limiting parameters. Total blood volume (BV) is the sum of the plasma volume (PV) and the total red cell volume. The measured [Hb] is dependent upon the total circulating mass of haemoglobin (tHb-mass) and plasma volume (PV). While the proportion of oxygen carried in plasma is trivial (0.3 mL of oxygen per 100 mL of plasma), each gram of Hb, contained in red blood cells, binds 1.39 mL of oxygen. As a result, the relationship between V˙O2max and tHb-mass is stronger than that observed between V˙O2max and [Hb] or BV. The glycoprotein hormone erythropoietin drives red cell synthesis and, like simple transfusion of packed red blood cells, can increase tHb-mass. An iron-containing haem group lies at the centre of the Hb molecule and, in situations of actual or functional iron deficiency, tHb-mass will also rise following iron administration. However achieved, an increase in tHb-mass also increases circulating oxygen-carrying capacity, and thus the capacity for aerobic phosphorylation. It is for such reasons that alterations in V˙O2max and exercise performance are proportional to those in arterial oxygen content and systemic oxygen transport, a change in tHb-mass of 1 g being associated with a 4 mL · min-1 change in V˙O2max. Similarly, V˙O2max increases by approximately 1% for each 3 g · L-1 increase in [Hb] over the [Hb] range (120 to 170 g · L-1). Surgery, like exercise, places substantial metabolic demands on the patient. Whilst subject to debate, oxygen supply at a rate inadequate to prevent muscle anaerobiosis may underpin the occurrence of the anaerobic threshold (AT), an important submaximal marker of cardiorespiratory fitness. Preoperatively, cardiopulmonary exercise testing (CPET) can be used to determine AT and peak exertional oxygen uptake (V˙O2 peak) as measures of ability to meet increasing oxygen demands. The degree of surgical insult and the ability to meet the resulting additional postoperative oxygen demand appear to be fundamental determinants of surgical outcome: individuals in whom such ability is impaired (and thus those with reduced V˙O2 peak and AT) are at greater risk of adverse surgical outcome. This review provides an overview of the relationships between [Hb], tHb-mass, exercise capacity, and surgical outcome and discusses the potential value of assessing tHb-mass over [Hb].

Perioperative increase in global blood flow to explicit defined goals and outcomes after surgery: a Cochrane Systematic Review

This systematic review and meta-analysis summarizes the clinical effects of increasing perioperative blood flow using fluids with or without inotropes/vasoactive drugs to explicit defined goals in adults. We included randomized controlled trials of adult patients (aged 16 years or older) undergoing surgery. We included 31 studies of 5292 participants. There was no difference in mortality at the longest follow-up: 282/2615 (10.8%) died in the control group and 238/2677 (8.9%) in the treatment group, RR of 0.89 (95% CI: 0.76-1.05; P=0.18). However, the results were sensitive to analytical methods and withdrawal of studies with methodological limitations. The intervention reduced the rate of three morbidities (renal failure, respiratory failure, and wound infections) but not the rates of arrhythmia, myocardial infarction, congestive cardiac failure, venous thrombosis, and other types of infections. The number of patients with complications was also reduced by the intervention. Hospital length of stay was reduced in the treatment group by 1.16 days. There was no difference in critical care length of stay. The primary analysis of this review showed no difference between groups but this result was sensitive to the method of analysis, withdrawal of studies with methodological limitations, and was dominated by a single large study. Patients receiving this intervention stayed in hospital 1 day less with fewer complications. It is unlikely that the intervention causes harm. The balance of current evidence does not support widespread implementation of this approach to reduce mortality but does suggest that complications and duration of hospital stay are reduced.

Perioperative increase in global blood flow to explicit defined goals and outcomes following surgery

BACKGROUND

Studies have suggested that increasing whole body blood flow and oxygen delivery around the time of surgery reduces mortality, morbidity and the expense of major operations.

OBJECTIVES

To describe the effects of increasing perioperative blood flow using fluids with or without inotropes or vasoactive drugs. Outcomes were mortality, morbidity, resource utilization and health status.

SEARCH METHODS

We searched CENTRAL (The Cochrane Library 2012, Issue 1), MEDLINE (1966 to March 2012) and EMBASE (1982 to March 2012). We manually searched the proceedings of major conferences and personal reference databases up to December 2011. We contacted experts in the field and pharmaceutical companies for published and unpublished data.

SELECTION CRITERIA

We included randomized controlled trials with or without blinding. We included studies involving adult patients (aged 16 years or older) undergoing surgery (patients having a procedure in an operating room). The intervention met the following criteria. 'Perioperative' was defined as starting up to 24 hours before surgery and stopping up to six hours after surgery. 'Targeted to increase global blood flow' was defined by explicit measured goals that were greater than in controls, specifically one or more of cardiac index, oxygen delivery, oxygen consumption, stroke volume (and the respective derived indices), mixed venous oxygen saturation (SVO(2)), oxygen extraction ratio (0(2)ER) or lactate.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data. We contacted study authors for additional data. We used Review Manager software.

MAIN RESULTS

We included 31 studies of 5292 participants. There was no difference in mortality: 282/2615 (10.8%) died in the control group and 238/2677 (8.9%) in the treatment group, RR of 0.89 (95% CI 0.76 to 1.05, P = 0.18). However, the results were sensitive to analytical methods and the intervention was better than control when inverse variance or Mantel-Haenszel random-effects models were used, RR of 0.72 (95% CI 0.55 to 0.95, P = 0.02). The results were also sensitive to withdrawal of studies with methodological limitations. The rates of three morbidities were reduced by increasing global blood flow: renal failure, RR of 0.71 (95% CI 0.57 to 0.90); respiratory failure, RR of 0.51 (95% CI 0.28 to 0.93); and wound infections, RR of 0.65 (95% CI 0.51 to 0.84). There were no differences in the rates of nine other morbidities: arrhythmia, pneumonia, sepsis, abdominal infection, urinary tract infection, myocardial infarction, congestive cardiac failure or pulmonary oedema, or venous thrombosis. The number of patients with complications was reduced by the intervention, RR of 0.68 (95% CI 0.58 to 0.80). Hospital length of stay was reduced in the treatment group by a mean of 1.16 days (95% CI 0.43 to 1.89, P = 0.002). There was no difference in critical care length of stay. There were insufficient data to comment on quality of life and cost effectiveness.

AUTHORS' CONCLUSIONS

It remains uncertain whether increasing blood flow using fluids, with or without inotropes or vasoactive drugs, reduces mortality in adults undergoing surgery. The primary analysis in this review (mortality at longest follow-up) showed no difference between the intervention and control, but this result was sensitive to the method of analysis, the withdrawal of studies with methodological limitations, and is dominated by a single large RCT. Overall, for every 100 patients in whom blood flow is increased perioperatively to defined goals, one can expect 13 in 100 patients (from 40/100 to 27/100) to avoid a complication, 2/100 to avoid renal impairment (from 8/100 to 6/100), 5/100 to avoid respiratory failure (from 10/100 to 5/100), and 4/100 to avoid postoperative wound infection (from 10/100 to 6/100). On average, patients receiving the intervention stay in hospital one day less. It is unlikely that the intervention causes harm. The balance of current evidence does not support widespread implementation of this approach to reduce mortality but does suggest that complications and duration of hospital stay are reduced.

The use of early intervention to prevent postoperative complications

PURPOSE OF REVIEW

The incidence of complications following major surgery is surprisingly high. Patients who develop complications suffer a reduction in long-term survival. This review aims to explore recent advances in the management of surgical patients aimed at preventing postoperative complications.

RECENT FINDINGS

Identifying patients prior to surgery who are at risk of a poor outcome remains challenging. There are a number of scoring systems to assist clinical risk assessment. Recent work has investigated the use of plasma biomarkers for perioperative risk prediction. Therapies aimed at reducing complication rates by attempting to improve tissue oxygen delivery include goal-directed haemodynamic therapy and postoperative noninvasive ventilation. The role of perioperative beta-adrenoceptor antagonists remains unclear. Other important measures include the use of a surgical safety checklist and thromboprophylaxis.

SUMMARY

Current systems for the identification and treatment of high-risk surgical patients are inadequate. Further research is required to establish the optimal approach to the identification and management of the high-risk surgical patient.

Association between Cardiac Index and Mortality in Patients Assessed on the Ward by a Nurse-Led Critical Care Outreach Team

Derangements in cardiac output are associated with mortality in various patient groups but the relationship between cardiac output and mortality in critically ill patients on standard hospital wards has not been investigated. In this single-centre observational study, cardiac output was measured using a non-invasive supra-sternal Doppler technique in patients referred to a critical care outreach team. Data were collected at baseline and four hours later in 113 patients, of whom 28 died (24.8%) and 37 were admitted to critical care (32.7%). During this period, there was a significant decrease in mean cardiac index (2.74 L/min/m2 [95% confidence intervals 1.78–4.35] to 2.18 L/min/m2 [95% CI 1.54–3.21]; p=0.049) and stroke volume index (24 mL/m2 [95% CI 16–36] to 20 mL/m2 [95% CI 15–31]; p=0.02) in non-survivors, whilst in survivors these variables remained unchanged. There were no changes in heart rate or mean arterial pressure in either survivors or non-survivors. For 216 patients in whom only baseline data were available, only age, heart rate, arterial pressure, respiratory rate and temperature were independently associated with mortality. In conclusion, in the four hours following assessment on the ward by a critical care outreach team, cardiac index and stroke volume index were maintained in survivors, but decreased significantly in non-survivors. At baseline, neither variable was associated with mortality.

Transfusion-related immunomodulation (TRIM): an update

Allogeneic blood transfusion (ABT)-related immunomodulation (TRIM) encompasses the laboratory immune aberrations that occur after ABT and their established or purported clinical effects. TRIM is a real biologic phenomenon resulting in at least one established beneficial clinical effect in humans, but the existence of deleterious clinical TRIM effects has not yet been confirmed. Initially, TRIM encompassed effects attributable to ABT by immunomodulatory mechanisms (e.g., cancer recurrence, postoperative infection, or virus activation). More recently, TRIM has also included effects attributable to ABT by pro-inflammatory mechanisms (e.g., multiple-organ failure or mortality). TRIM effects may be mediated by: (1) allogeneic mononuclear cells; (2) white-blood-cell (WBC)-derived soluble mediators; and/or (3) soluble HLA peptides circulating in allogeneic plasma. This review categorizes the available randomized controlled trials based on the inference(s) that they permit about possible mediator(s) of TRIM, and examines the strength of the evidence available for relying on WBC reduction or autologous transfusion to prevent TRIM effects.

Multicentre study on peri- and postoperative central venous oxygen saturation in high-risk surgical patients

Introduction

Low central venous oxygen saturation (ScvO₂) has been associated with increased risk of postoperative complications in high-risk surgery. Whether this association is centre-specific or more generalisable is not known. The aim of this study was to assess the association between peri- and postoperative ScvO₂ and outcome in high-risk surgical patients in a multicentre setting.

Methods

Three large European university hospitals (two in Finland, one in Switzerland) participated. In 60 patients with intra-abdominal surgery lasting more than 90 minutes, the presence of at least two of Shoemaker's criteria, and ASA (American Society of Anesthesiologists) class greater than 2, ScvO₂ was determined preoperatively and at two hour intervals during the operation until 12 hours postoperatively. Hospital length of stay (LOS) mortality, and predefined postoperative complications were recorded.

Results

The age of the patients was 72 ± 10 years (mean ± standard deviation), and simplified acute physiology score (SAPS II) was 32 ± 12. Hospital LOS was 10.5 (8 to 14) days, and 28-day hospital mortality was 10.0%. Preoperative ScvO₂ decreased from 77% ± 10% to 70% ± 11% (p < 0.001) immediately after surgery and remained unchanged 12 hours later. A total of 67 postoperative complications were recorded in 32 patients. After multivariate analysis, mean ScvO₂ value (odds ratio [OR] 1.23 [95% confidence interval (CI) 1.01 to 1.50], p = 0.037), hospital LOS (OR 0.75 [95% CI 0.59 to 0.94], p = 0.012), and SAPS II (OR 0.90 [95% CI 0.82 to 0.99], p = 0.029) were independently associated with postoperative complications. The optimal value of mean ScvO₂ to discriminate between patients who did or did not develop complications was 73% (sensitivity 72%, specificity 61%).

Conclusion

Low ScvO₂ perioperatively is related to increased risk of postoperative complications in high-risk surgery. This warrants trials with goal-directed therapy using ScvO₂ as a target in high-risk surgery patients.

Perioperative blood transfusion and outcome

PURPOSE OF REVIEW

As a result of advances in pathogen testing and transfusion standards over the last decade, the risk of disease transmission through allogeneic blood transfusions has decreased markedly. The effects of allogeneic blood transfusions on the immune system, however, have received more attention, as they appear to influence outcome. The following review summarizes the effects of allogeneic blood transfusions on selected outcome parameters and the influence of white blood cell reduction on these parameters.

RECENT FINDINGS

Adverse effects of allogeneic blood transfusions on outcome variables such as postoperative infection, cancer recurrence, pulmonary function, length of stay, and mortality have been shown in multiple trials, but most were not randomized or blinded. One proposed approach to reduce unwanted side-effects is to reduce the donor's white blood cell count before transfusion. This can be done either by individual bedside filtration or by pre-storage (or post-storage) universal white blood cell reduction. Studies investigating this approach have yielded conflicting results.

SUMMARY

Although the results of a number of studies suggest a negative impact of allogeneic blood transfusions on immune function and consequently outcome parameters, this has not been proven in rigorously controlled randomized trial, or in meta-analyses. Reduction of white blood cells might be beneficial in selected patient populations, but at this time does not appear warranted in the general surgical population. As universal white blood cell reduction is a very costly process, it probably should not be implemented until such a benefit is proven.

What would Karl Landsteiner do? The ABO blood group and stem cell transplantation

ABO blood group antigens, of great importance in transplantation and transfusion, are present on virtually all cells, as well as in soluble form in plasma and body fluids. Naturally occurring plasma IgM and IgG antibodies against these antigens are ubiquitous. Nonetheless, the ABO blood group system is widely ignored by many transfusion services, except for purposes of red cell transfusion. We implemented a policy of transfusing only ABO identical platelets and red cells in patients undergoing stem cell transplantation or treatment for hematologic malignancies. Major bleeding episodes have occurred in about 5% of patients undergoing induction therapy for acute leukemia as compared with 15-20% in the literature. Overall survival times appear to be superior to that in historical cohorts. In 2002-2004, treatment-related mortality at 100 days in our Blood and Marrow Transplant Unit was 0.7% for autologous transplants (n=148), 13% for sibling allogeneic transplants (n=110), and 24% (n=62) for matched unrelated allogeneic transplants, suggesting that our approach is safe. We speculate that more rigorous efforts on the part of transfusion services to provide ABO identical blood components, and to remove incompatible supernatant plasma, when necessary, might yield reduced morbidity and mortality in patients undergoing stem cell transplantation.

Changes in central venous saturation after major surgery, and association with outcome

INTRODUCTION

Despite recent interest in measurement of central venous oxygen saturation (ScvO2), there are no published data describing the pattern of ScvO2 changes after major general surgery or any relationship with outcome.

METHODS

ScvO2 and other biochemical, physiological and demographic data were prospectively measured for 8 hours after major surgery. Complications and deaths occurring within 28 days of enrollment were included in the data analysis. Independent predictors of complications were identified with the use of logistic regression analysis. Optimum cutoffs for ScvO2 were identified by receiver operator characteristic analysis.

RESULTS

Data from 118 patients was analysed; 123 morbidity episodes occurred in 64 these patients. There were 12 deaths (10.2%). The mean +/- SD age was 66.8 +/- 11.4 years. Twenty patients (17%) underwent emergency surgery and 77 patients (66%) were male. The mean +/- SD P-POSSUM (Portsmouth Physiologic and Operative Severity Score for the enUmeration of Mortality and morbidity) score was 38.6 +/- 7.7, with a predicted mortality of 16.7 +/- 17.6%. After multivariate analysis, the lowest cardiac index value (odds ratio (OR) 0.58 (95% confidence intervals 0.37 to 0.9); p = 0.018), lowest ScvO2 value (OR 0.94 (0.89 to 0.98); p = 0.007) and P-POSSUM score (OR 1.09 (1.02 to 1.15); p = 0.008) were independently associated with post-operative complications. The optimal ScvO2 cutoff value for morbidity prediction was 64.4%. In the first hour after surgery, significant reductions in ScvO2 were observed, but there were no significant changes in CI or oxygen delivery index during the same period.

CONCLUSION

Significant fluctuations in ScvO2 occur in the immediate post-operative period. These fluctuations are not always associated with changes in oxygen delivery, suggesting that oxygen consumption is also an important determinant of ScvO2. Reductions in ScvO2 are independently associated with post-operative complications.

WBC-containing allogeneic blood transfusion and mortality: a meta-analysis of randomized controlled trials

BACKGROUND

An association between allogeneic blood transfusion (ABT) and mortality was reported by one team of investigators from randomized controlled trials (RCTs) comparing recipients of non-WBC-reduced versus WBC-reduced RBCs in open-heart surgery. A meta-analysis was undertaken to examine whether this finding can be generalized across clinical settings and/or transfused RBC components.

STUDY DESIGN AND METHODS

RCTs reporting on adverse immunomodulatory effects of ABT between January 1992 and August 2002 were retrieved. Fourteen studies had recorded mortality as a primary or secondary outcome and met all other criteria for meta-analysis. Summary ORs of mortality in a treatment arm receiving WBC-containing allogeneic RBCs versus a control arm receiving autologous or WBC-reduced allogeneic RBCs were calculated across studies, for groups of studies in which the hypothesis of homogeneity was not rejected.

RESULTS

There was no association between ABT and mortality across 14 RCTs reporting on short-term mortality (summary OR, 1.20; 95% CI, 0.87-1.65) or across 3 RCTs reporting on long-term mortality (summary OR, 0.87; 95% CI, 0.64-1.19). In subgroup analyses, RCTs using autologous blood or conducted in abdominal or vascular surgery showed no difference in mortality, but short-term mortality differed across 3 RCTs conducted in open-heart surgery (summary OR, 2.26; 95% CI, 1.31-3.90; p < 0.05) and 7 RCTs comparing recipients of non-WBC-reduced versus WBC-reduced allogeneic RBCs filtered before storage (summary OR, 1.45; 95% CI, 1.00-2.11; p >/= 0.05).

CONCLUSIONS

An association between ABT and either short-term or long-term mortality was not detected across clinical settings and transfused RBC components, but subgroup analyses suggest that an association between WBC-containing ABT and short-term mortality may exist in open-heart surgery and in settings where WBC-reduced allogeneic RBCs filtered before storage are administered.

Factors associated with mortality in patients with penetrating abdominal vascular trauma

OBJECTIVE

Prehospital transport, resuscitation, and operative intervention are all critical to the care of the penetrating trauma victim. We determined which factors most affected mortality in patients with penetrating abdominal vascular injuries.

METHODS

Consecutive patients with penetrating abdominal vascular injuries from an urban Level I trauma center from January 1993 to December 1998 were identified from the trauma registry and their charts reviewed. All patients who died prior to operative intervention were excluded. Data collected included mortality, age, scene time (ST), EMS transport time (TT), time in the emergency department (ED), initial systolic blood pressure in the ED (BP), operating time, intraoperative estimated blood loss (EBL), and worst base deficit in the first 24 h (BD). These variables were compared between nonsurvivors and survivors by univariate ANOVA. Multivariate ANOVA (MANOVA) determined independent effects on mortality.

RESULTS

Forty-six penetrating abdominal vascular injuries were identified in 31 patients, 11 of whom died (38.7%). Examining prehospital parameters, mean ST averaged 16.5 +/- 3.6 min, while TT was 31.8 +/- 7.1 min. For ED parameters, initial BP was 94.8 +/- 6.4 mm Hg and initial heart rate was 109 +/- 7 beats per minute. Mean operative EBL for all patients was 3518 +/- 433 ml. The mean BD for all patients was -12.9 +/- 1.8. Significant differences were noted in the univariate analysis between survivors and nonsurvivors for BD (P < 0.0001), BP (P = 0.0062) and EBL (P = 0.0002). MANOVA revealed that only base deficit (P < 0.0001) had an independent effect on mortality.

CONCLUSIONS

In patients with penetrating abdominal vascular injuries who survive their ED stay, adverse physiologic parameters reflecting the adequacy of resuscitation are more predictive of mortality than identifiable prehospital parameters.

Allogeneic blood transfusion and postoperative duration of mechanical ventilation: effects of red cell supernatant, platelet supernatant, plasma components and total transfused fluid

BACKGROUND AND OBJECTIVES

In patients undergoing open-heart surgery, allogeneic blood transfusion (ABT) may be related to an enhanced inflammatory response and impaired pulmonary function, resulting in a need for prolonged mechanical ventilation. Transfused red blood cell (RBC) supernatant, platelet supernatant or plasma components, may exercise varying effects on pulmonary function, because these fluids differ in their content of soluble biological-response modifiers.

MATERIALS AND METHODS

The records of 416 patients undergoing coronary artery bypass graft operations at the Massachusetts General Hospital were reviewed. Possible predictors and the number of days of postoperative ventilation, as well as the number of all transfused blood components, were recorded. The association between mechanical ventilation past the day of operation and the volume of transfused RBC supernatant, platelet supernatant, or plasma components, was calculated by logistic regression analyses.

RESULTS

The volume of each transfused fluid differed (P < 0.0001) among patients ventilated for 0, 1, 2, 3, or > or = 4 days after the day of the operation. After adjusting for the effects of confounding factors, the volume of administered RBC supernatant was associated (P = 0.0312) with the likelihood of postoperative ventilation past the day of operation, but the volume of platelet supernatant, plasma components, or total transfused fluid was not (P = 0.1528, P = 0.1847, and P = 0.0504, respectively).

CONCLUSIONS

These results are congruent with the hypotheses that ABT may impair postoperative pulmonary function and that any such adverse effect of ABT is probably mediated by the supernatant fluid of stored RBCs. Both hypotheses should be examined further, in future studies of the outcomes of ABT.

Early abdominal closure with mesh reduces multiple organ failure after ruptured abdominal aortic aneurysm repair: guidelines from a 10-year case-control study

OBJECTIVE

The objectives of this study were the comparison of patients who needed mesh closure of the abdomen with patients who underwent standard abdominal closure after ruptured abdominal aortic aneurysm repair and the determination of the impact of timing of mesh closure on multiple organ failure (MOF) and mortality.

METHODS

We performed a case-control study of patients who needed mesh-based abdominal closure (n = 45) as compared with patients who underwent primary closure (n = 90) after ruptured abdominal aortic aneurysm repair.

RESULTS

Before surgery, the patients who needed mesh abdominal closure had more blood loss (8 g versus 12 g of hemoglobin; P <.05), had prolonged hypotension (18 minutes versus 3 minutes; P <.01), and more frequently needed cardiopulmonary resuscitation (31% versus 2%; P <.01) than did the patients who underwent primary closure. During surgery, the patients who needed mesh closure also had more severe acidosis (base deficit, 14 versus 7; P <.01), had profound hypothermia (32 degrees C versus 35 degrees C; P <.01), and needed more fluid resuscitation (4.0 L/h versus 2.7 L/h; P <.01). With this adverse clinical profile, the patients who needed mesh closure had a higher mortality rate than did the patients who underwent primary closure (56% versus 9%; P <.01). However, the patients who underwent mesh closure at the initial operation (n = 35) had lower MOF scores (P <.05), a lower mortality rate (51% versus 70%), and were less likely to die from MOF (11% versus 70%; P <.05) than the patients who underwent mesh closure after a second operation in the postoperative period for abdominal compartment syndrome (n = 10).

CONCLUSION

This study reports the largest experience of mesh-based abdominal closure after ruptured abdominal aortic aneurysm repair and defines clinical predictors for patients who need to undergo this technique. Recognition of these predictors and initial use of mesh closure minimize abdominal compartment syndrome and reduce the rate of mortality as the result of MOF.

Allogeneic blood transfusion and postoperative duration of mechanical ventilation

BACKGROUND

In patients having open heart surgery, allogeneic blood transfusion (ABT) may be related to an enhanced inflammatory response and impaired pulmonary function, resulting in the need for prolonged mechanical ventilation.

STUDY DESIGN AND METHODS

The records of 416 consecutive patients undergoing coronary artery bypass graft surgery at Massachusetts General Hospital were reviewed. Possible predictors and the number of days of postoperative ventilation, as well as the number of RBC units transfused and the length of their storage, were recorded. The association between mechanical ventilation after the day of operation and the number of RBC units transfused was calculated by logistic regression analysis.

RESULTS

The number of RBC units transfused, but not the length of their storage, differed (p<0.0001) among patients ventilated for 0, 1, 2, 3, or 4 or more days after the day of operation. Patients taken off ventilation on the day of operation received (mean +/- SE) 2.01 +/- 0.14 RBC units; patients kept on ventilation for 4 or more days received 9.45 +/- 1.83 units. After adjusting for the effects of 18 confounding factors, the number of RBC units transfused was not a significant predictor of ventilation past the day of operation. There was, however, a trend suggesting that the likelihood of such ventilation might increase by 26 percent per RBC unit transfused (p = 0.0628).

CONCLUSIONS

Future studies of the outcomes of ABT should examine further the possibility of a relationship between the number of transfused RBCs and the likelihood of postoperative ventilation after the day of operation.

Treatment of ruptured abdominal aortic aneurysm, a permanent challenge or a waste of resources? Prediction of outcome using a multi-organ-dysfunction score

OBJECTIVES

in a retrospective study, attempts have been made to identify individual organ-dysfunction risk profiles influencing the outcome after surgery for ruptured abdominal aortic aneurysms.

METHODS

out of 235 patients undergoing graft replacement for abdominal aortic aneurysms, 57 (53 men, four women, mean age 72 years [s.d. 8.8]) were treated for ruptured aneurysms in a 3-year period. Forty-eight preoperative, 13 intraoperative and 34 postoperative variables were evaluated statistically. A simple multi-organ dysfunction (MOD) score was adopted.

RESULTS

the perioperative mortality was 32%. Three patients died intraoperatively, four within 48 h and 11 died later. A significant influence for pre-existing risk factors was identified only for cardiovascular diseases. Multiple linear-regression analysis indicated that a haemoglobin <90 g/l, systolic blood pressure <80 mmHg and ECG signs of ischaemia at admission were highly significant risk factors. The cause of death for patients, who died more than 48 h postoperatively, was mainly MOD. All patients with a MOD score >/=4 died (n=7). These patients required 27% of the intensive-care unit (ICU) days of all patients and 72% of the ICU days of the non-survivors.

CONCLUSION

patients with ruptured aortic aneurysms from treatment should not be excluded. However, a physiological scoring system after 48 h appears justifiable in order to decide on the appropriateness of continual ICU support.