A systematic review and meta-analysis on the use of preemptive hemodynamic intervention to improve postoperative outcomes in moderate and high-risk surgical patients

Evaluation of a novel closed-loop fluid-administration system based on dynamic predictors of fluid responsiveness: an in silico simulation study

Introduction

Dynamic predictors of fluid responsiveness have made automated management of fluid resuscitation more practical. We present initial simulation data for a novel closed-loop fluid-management algorithm (LIR, Learning Intravenous Resuscitator).

Methods

The performance of the closed-loop algorithm was tested in three phases by using a patient simulator including a pulse-pressure variation output. In the first phase, LIR was tested in three different hemorrhage scenarios and compared with no management. In the second phase, we compared LIR with 20 practicing anesthesiologists for the management of a simulated hemorrhage scenario. In the third phase, LIR was tested under conditions of noise and artifact in the dynamic predictor.

Results

In the first phase, we observed a significant difference between the unmanaged and the LIR groups in moderate to large hemorrhages in heart rate (76 ± 8 versus 141 ± 29 beats/min), mean arterial pressure (91 ± 6 versus 59 ± 26 mm Hg), and cardiac output (CO; (6.4 ± 0.9 versus 3.2 ± 1.8 L/min) (P < 0.005 for all comparisons). In the second phase, LIR intervened significantly earlier than the practitioners (16.0 ± 1.3 minutes versus 21.5 ± 5.6 minutes; P < 0.05) and gave more total fluid (2,675 ± 244 ml versus 1,968 ± 644 ml; P < 0.05). The mean CO was higher in the LIR group than in the practitioner group (5.9 ± 0.2 versus 5.2 ± 0.6 L/min; P < 0.05). Finally, in the third phase, despite the addition of noise to the pulse-pressure variation value, no significant difference was found across conditions in mean, final, or minimum CO.

Conclusion

These data demonstrate that LIR is an effective volumetric resuscitator in simulated hemorrhage scenarios and improved physician management of the simulated hemorrhages.

Haemodynamic optimisation: are we dynamic enough?

Perioperative haemodynamic optimisation of high-risk surgical patients has long been documented to improve both short-term and long-term outcomes, as well as to reduce the rate of postoperative complications. Based on the evidence, cardiac output monitoring and fluid resuscitation, combined with the use of inotropes, would seem to be the gold standard of care for these difficult surgical cases. However, clinicians do not universally apply these techniques and principles in their everyday practice. By exploring the reasons why this is so, perhaps we could move forward in the standardisation of care and the application of evidence-based practice.

Clinical review: use of venous oxygen saturations as a goal - a yet unfinished puzzle

Shock is defined as global tissue hypoxia secondary to an imbalance between systemic oxygen delivery and oxygen demand. Venous oxygen saturations represent this relationship between oxygen delivery and oxygen demand and can therefore be used as an additional parameter to detect an impaired cardiorespiratory reserve. Before appropriate use of venous oxygen saturations, however, one should be aware of the physiology. Although venous oxygen saturation has been the subject of research for many years, increasing interest arose especially in the past decade for its use as a therapeutic goal in critically ill patients and during the perioperative period. Also, there has been debate on differences between mixed and central venous oxygen saturation and their interchangeability. Both mixed and central venous oxygen saturation are clinically useful but both variables should be used with insightful knowledge and caution. In general, low values warn the clinician about cardiocirculatory or metabolic impairment and should urge further diagnostics and appropriate action, whereas normal or high values do not rule out persistent tissue hypoxia. The use of venous oxygen saturations seems especially useful in the early phase of disease or injury. Whether venous oxygen saturations should be measured continuously remains unclear. Especially, continuous measurement of central venous oxygen saturation as part of the treatment protocol has been shown a valuable strategy in the emergency department and in cardiac surgery. In clinical practice, venous oxygen saturations should always be used in combination with vital signs and other relevant endpoints.

Review article: closed-loop systems in anesthesia: is there a potential for closed-loop fluid management and hemodynamic optimization?

Closed-loop (automated) controllers are encountered in all aspects of modern life in applications ranging from air-conditioning to spaceflight. Although these systems are virtually ubiquitous, they are infrequently used in anesthesiology because of the complexity of physiologic systems and the difficulty in obtaining reliable and valid feedback data from the patient. Despite these challenges, closed-loop systems are being increasingly studied and improved for medical use. Two recent developments have made fluid administration a candidate for closed-loop control. First, the further description and development of dynamic predictors of fluid responsiveness provides a strong parameter for use as a control variable to guide fluid administration. Second, rapid advances in noninvasive monitoring of cardiac output and other hemodynamic variables make goal-directed therapy applicable for a wide range of patients in a variety of clinical care settings. In this article, we review the history of closed-loop controllers in clinical care, discuss the current understanding and limitations of the dynamic predictors of fluid responsiveness, and examine how these variables might be incorporated into a closed-loop fluid administration system.

Hemodynamic monitoring and management in patients undergoing high risk surgery: a survey among North American and European anesthesiologists

Introduction

Several studies have demonstrated that perioperative hemodynamic optimization has the ability to improve postoperative outcome in high-risk surgical patients. All of these studies aimed at optimizing cardiac output and/or oxygen delivery in the perioperative period. We conducted a survey with the American Society of Anesthesiologists (ASA) and the European Society of Anaesthesiology (ESA) to assess current hemodynamic management practices in patients undergoing high-risk surgery in Europe and in the United States.

Methods

A survey including 33 specific questions was emailed to 2,500 randomly selected active members of the ASA and to active ESA members.

Results

Overall, 368 questionnaires were completed, 57.1% from ASA and 42.9% from ESA members. Cardiac output is monitored by only 34% of ASA and ESA respondents (P = 0.49) while central venous pressure is monitored by 73% of ASA respondents and 84% of ESA respondents (P < 0.01). Specifically, the pulmonary artery catheter is being used much more frequently in the US than in Europe in the setup of high-risk surgery (85.1% vs. 55.3% respectively, P < 0.001). Clinical experience, blood pressure, central venous pressure, and urine output are the most widely indicators of volume expansion. Finally, 86.5% of ASA respondents and 98.1% of ESA respondents believe that their current hemodynamic management could be improved.

Conclusions

In conclusion, these results point to a considerable gap between the accumulating evidence about the benefits of perioperative hemodynamic optimization and the available technologies that may facilitate its clinical implementation, and clinical practices in both Europe and the United States.

Recommendations for haemodynamic and neurological monitoring in repair of acute type a aortic dissection

During treatment of acute type A aortic dissection there is potential for both pre- and intra-operative malperfusion. There are a number of monitoring strategies that may allow for earlier detection of potentially catastrophic malperfusion (particularly cerebral malperfusion) phenomena available for the anaesthetist and surgeon. This review article sets out to discuss the benefits of the current standard monitoring techniques available as well as desirable/experimental techniques which may serve as adjuncts in the monitoring of these complex patients.

Epidemiology and outcome following post-surgical admission to critical care

PURPOSE

To describe the factors related to outcome in patients admitted to the intensive care unit (ICU) after major surgery at a national level (in Austria).

METHODS

Analysis of a prospectively collected database of ICU admissions over an 11-year period. Factors associated with mortality and how this changed with time were explored using logistic multilevel modelling.

RESULTS

A total of 88,504 surgical patients had a mean ICU length of stay of 6.5 days and total hospital stay of 31.3 days. They had an ICU mortality of 7.6% and a hospital mortality of 11.8%. Factors associated with hospital mortality included age (odds ratio (OR) 1.42 per 10 years of age), urgency of operation (2.02 for emergency when compared to elective), SAPS II score (OR 1.09), reason for admission being a medical cause and the specific nature of the surgery itself: thoracic (OR 1.81), cardiovascular (OR 1.25), trauma (OR 1.22) or gastrointestinal surgery (OR 1.71). In addition patients who had pre-existing chronic renal (OR 1.40), respiratory (OR 1.20) or cardiac failure (OR 1.29), cirrhosis (OR 2.50), alcoholism (OR 1.42), acute kidney injury (OR 1.88) and/or non-metastatic cancer (OR 1.20) were associated with higher hospital mortality than patients without this co-morbidity. There was a reduction in the OR for death over the whole 11-year period. This improved outcome remained valid even after adjusting for the identified risk factors for mortality (OR per year 0.96).

CONCLUSIONS

This study has shown the high level of demand for critical care for this patient group and an improving rate of survival.

Goal-directed haemodynamic therapy during elective total hip arthroplasty under regional anaesthesia

Introduction

Total hip replacement is one of the most commonly performed major orthopaedic operations. Goal-directed therapy (GDT) using haemodynamic monitoring has previously demonstrated outcome benefits in high-risk surgical patients under general anaesthesia. GDT has never been formally assessed during regional anaesthesia.

Methods

Patients undergoing total hip replacement while under regional anaesthesia were randomised to either the control group (CTRL) or the protocol group (GDT). Patients in the GDT group, in addition to standard monitoring, were connected to the FloTrac sensor/Vigileo monitor haemodynamic monitoring system, and a GDT protocol was used to maximise the stroke volume and target the oxygen delivery index to > 600 mL/minute/m².

Results

Patients randomised to the GDT group were given a greater volume of intravenous fluids during the intraoperative period (means ± standard deviation (SD): 6,032 ± 1,388 mL vs. 2,635 ± 346 mL; P < 0.0001), and more of the GDT patients received dobutamine (0 of 20 CTRL patients vs. 11 of 20 GDT patients; P < 0.0003). The GDT patients also received more blood transfused during the intraoperative period (means ± SD: 595 ± 316 mL vs. 0 ± 0 mL; P < 0.0001), although the CTRL group received greater volumes of blood replacement postoperatively (CTRL patients 658 ± 68 mL vs. GDT patients 198 ± 292 mL; P < 0.001). Overall blood consumption (intraoperatively and postoperatively) was not different between the two groups. There were an increased number of complications in the CTRL group (20 of 20 CTRL patients (100%) vs. 16 of 20 GDT patients (80%); P = 0.05). These outcomes were predominantly due to a difference in minor complications (20 of 20 CTRL patients (100%) vs. 15 of 20 GDT patients (75%); P = 0.047).

Conclusions

GDT applied during regional anaesthesia in patients undergoing elective total hip replacement changes intraoperative fluid management and may improve patient outcomes by decreasing postoperative complications. Larger trials are required to confirm our findings.

Trial registration

SRCTN11616985

Perioperative fluid and volume management: physiological basis, tools and strategies

Fluid and volume therapy is an important cornerstone of treating critically ill patients in the intensive care unit and in the operating room. New findings concerning the vascular barrier, its physiological functions, and its role regarding vascular leakage have lead to a new view of fluid and volume administration. Avoiding hypervolemia, as well as hypovolemia, plays a pivotal role when treating patients both perioperatively and in the intensive care unit. The various studies comparing restrictive vs. liberal fluid and volume management are not directly comparable, do not differ (in most instances) between colloid and crystalloid administration, and mostly do not refer to the vascular barrier's physiologic basis. In addition, very few studies have analyzed the use of advanced hemodynamic monitoring for volume management.

This article summarizes the current literature on the relevant physiology of the endothelial surface layer, discusses fluid shifting, reviews available research on fluid management strategies and the commonly used fluids, and identifies suitable variables for hemodynamic monitoring and their goal-directed use.

Surgical intensive care unit - essential for good outcome in major abdominal surgery?

PURPOSE

Surgical intensive care units (ICU) play a pivotal role in perioperative care of patients undergoing major abdominal surgery. Differences in quality of care provided by medical staff in ICUs may be linked to improved outcome. This review aims to elucidate the relationship between quality of care at various ICUs and patient outcome, with the ultimate aim of identifying key measures for achieving optimal outcome.

METHODS

We reviewed the literature in PubMed to identify current ICU structural and process concepts and variations before evaluating their respective impact on quality of care and outcome in major abdominal surgery.

RESULTS

ICU leadership, nurse and physician staffing, and provision of an intermediate care unit are important structural components that impact on patients' outcome. A "mixed ICU" model, with intensivists primarily caring for the patients in close cooperation with the primary physician, seems to be the most effective ICU model. Surgeons' involvement in intensive care is essential, and a close cooperation between surgeons and anesthesiologists is vital for good outcome. Current general process concepts include early mobilization, enteral feeding, and optimal perioperative fluid management. To decrease failure-to-rescue rates, procedure-specific intensive care processes are particularly focused on the early detection, assessment, and timely and consistent treatment of complications.

CONCLUSIONS

Several structures and processes in the ICU have an impact on outcome in major abdominal surgery. ICU structures and care processes connected with optimal outcome could be transmitted to other centers to improve outcome, independent of procedure volume.