Intraoperative fluid optimization using stroke volume variation in high risk surgical patients: results of prospective randomized study

Multiparameter Predictor of Fluid Responsiveness in Cardiac Surgical Patients Receiving Tidal Volumes Less Than 10 mL/kg

Introduction We hypothesize that respiratory variation in the pulmonary artery tracing predicts fluid responsiveness (primary hypothesis) and that inclusion of multiple physiologic waveforms as well as ventilator settings in a predictive model of fluid responsiveness would lead to improvements in the clinical utility of this class of metrics (secondary hypothesis). Methods Blood pressure tracings were prospectively recorded in 35 patients immediately following cardiac surgery. Fluid bolus administration data, ventilator settings, and cardiac output were recorded prospectively before and after fluid boluses given at the discretion of the treating physician. Results We observed statistically significant but limited relationships between pulmonic (r(2) = .26, P = .0052) and systemic (r(2) = .13, P = .011) pulse pressure variation and changes in cardiac index. A multiparameter estimate of fluid responsiveness, which included respiratory variation in central venous pressure and pulmonary artery pressure, indexed tidal volumes, positive end-expiratory pressure, and mean airway pressure, was also correlated with change in cardiac index (r(2) = .42, P = .0056). Using the area under the curve (AUC) technique to compare specificity and sensitivity, dynamic indicators (AUC = 0.74, 0.67, and 0.81 for systemic arterial respiratory [pulse pressure] variation, pulmonic arterial respiratory [pulse pressure] variation, and the multiparameter estimate, respectively) outperformed static estimates (0.49 and 0.48 for central venous pressure and pulmonary artery diastolic pressure, respectively). Conclusion While integration of multiple physiologic waveforms as well as ventilator parameters improves the predictability of fluid responsive metrics in the setting of lung-protective ventilation, the composite index may still be of limited predictive value.

Respiratory variation of systolic and diastolic time intervals within radial arterial waveform: a comparison with dynamic preload index

BACKGROUND

A blood pressure (BP) waveform contains various pieces of information related to respiratory variation. Systolic time interval (STI) reflects myocardial performance, and diastolic time interval (DTI) represents diastolic filling. This study examined whether respiratory variations of STI and DTI within radial arterial waveform are comparable to dynamic indices.

METHODS

During liver transplantation, digitally recorded BP waveform and stroke volume variation (SVV) were retrospectively analyzed. Beat-to-beat STI and DTI were extracted within each BP waveform, which were separated by dicrotic notch. Systolic time variation (STV) was calculated by the average of 3 consecutive respiratory cycles: [(STImax- STImin)/STImean]. Similar formula was used for diastolic time variation (DTV) and pulse pressure variation (PPV). Receiver operating characteristic analysis with area under the curve (AUC) was used to assess thresholds predictive of SVV ≥12% and PPV ≥12%.

RESULTS

STV and DTV showed significant correlations with SVV (r= 0.78 and r= 0.67, respectively) and PPV (r= 0.69 and r= 0.69, respectively). Receiver operating characteristic curves demonstrated that STV ≥11% identified to predict SVV ≥12% with 85.7% sensitivity and 89.3% specificity (AUC = 0.935; P< .001). DTV ≥11% identified to predict SVV ≥12% with 71.4% sensitivity and 85.7% specificity (AUC = 0.829; P< .001). STV ≥12% and DTV ≥11% identified to predict PPV ≥12% with an AUC of 0.881 and 0.885, respectively.

CONCLUSION

Respiratory variations of STI and DTI derived from radial arterial contour have a potential to predict hemodynamic response as a surrogate for SVV or PPV.

Intraoperative Goal-directed Fluid Therapy in Elective Major Abdominal Surgery: A Meta-analysis of Randomized Controlled Trials

Objectives:

To compare the effects of intraoperative goal-directed fluid therapy (GDFT) with conventional fluid therapy, and determine whether there was a difference in outcome between studies that did and did not use Enhanced Recovery After Surgery (ERAS) protocols.

Methods:

Meta-analysis of randomized controlled trials of adult patients undergoing elective major abdominal surgery comparing intraoperative GDFT versus conventional fluid therapy. The outcome measures were postoperative morbidity, length of stay, gastrointestinal function and 30-day mortality.

Results:

A total of 23 studies were included with 2099 patients: 1040 who underwent GDFT and 1059 who received conventional fluid therapy. GDFT was associated with a significant reduction in morbidity (risk ratio [RR] 0.76, 95% confidence interval [CI] 0.66–0.89, P = 0.0007), hospital length of stay (LOS; mean difference −1.55 days, 95% CI −2.73 to −0.36, P = 0.01), intensive care LOS (mean difference −0.63 days, 95% CI −1.18 to −0.09, P = 0.02), and time to passage of feces (mean difference −0.90 days, 95% CI −1.48 to −0.32 days, P = 0.002). However, no difference was seen in mortality, return of flatus, or risk of paralytic ileus. If patients were managed in an ERAS pathway, the only significant reductions were in intensive care LOS (mean difference −0.63 days, 95% CI −0.94 to −0.32, P < 0.0001) and time to passage of feces (mean difference −1.09 days, 95% CI −2.03 to −0.15, P = 0.02). If managed in a traditional care setting, a significant reduction was seen in both overall morbidity (RR 0.69, 95% CI 0.57 to −0.84, P = 0.0002) and total hospital LOS (mean difference −2.14, 95% CI −4.15 to −0.13, P = 0.04).

Conclusions:

GDFT may not be of benefit to all elective patients undergoing major abdominal surgery, particularly those managed in an ERAS setting.

Monitoring high-risk patients: minimally invasive and non-invasive possibilities

Over the past decades, there has been considerable progress in the field of less invasive haemodynamic monitoring technologies. Substantial evidence has accumulated, which supports the continuous measurement and optimization of flow-based variables such as stroke volume, that is, cardiac output, in order to prevent occult hypoperfusion and consequently to improve patients' outcome in the perioperative setting. However, there is a striking gap between the developments in haemodynamic monitoring and the increasing evidence to implement defined treatment protocols based on the measured variables, and daily clinical routine. Recent trials have shown that perioperative morbidity and mortality is higher than anticipated. This emphasizes the need for the anaesthesia community to address this issue and promotes the implementation of proven concepts into clinical practice in order to improve patients' outcome, especially in high-risk patients. The advances in minimally invasive and non-invasive monitoring techniques can be seen as a driving force in this respect, as the degree of invasiveness of any monitoring tool determines the frequency of its application, especially in the operating room (OR). From this point of view, we are very confident that some of these minimally invasive and non-invasive haemodynamic monitoring technologies will become an inherent part of our monitoring armamentarium in the OR and in the intensive care unit (ICU).

Minimally Invasive Cardiac Output Monitoring: Agreement of Oesophageal Doppler, LiDCOrapid™ and Vigileo FloTrac™ Monitors in Non-Cardiac Surgery

There is lack of data about the agreement of minimally invasive cardiac output monitors, which make it impossible to determine if they are interchangeable or differ objectively in tracking physiological trends. We studied three commonly used devices: the oesophageal Doppler and two arterial pressure–based devices, the Vigileo FloTrac™ and LiDCOrapid™. The aim of this study was to compare the agreement of these three monitors in adult patients undergoing elective non-cardiac surgery. Measurements were taken at baseline and after predefined clinical interventions of fluid, metaraminol or ephedrine bolus. From 24 patients, 131 events, averaging 5.2 events per patient, were analysed. The cardiac index of LiDCOrapid versus FloTrac had a mean bias of −6.0% (limits of agreement from −51% to 39%) and concordance of over 80% to the three clinical interventions. The cardiac index of Doppler versus LiDCOrapid and Doppler versus FloTrac, had an increasing negative bias at higher mean cardiac outputs and there was significantly poorer concordance to all interventions. Of the preload-responsive parameters, Doppler stroke volume index, Doppler systolic flow time and FloTrac stroke volume variation were fair at predicting fluid responsiveness while other parameters were poor. While there is reasonable agreement between the two arterial pressure–derived cardiac output devices (LiDCOrapid and Vigileo FloTrac), these two devices differ significantly to the oesophageal Doppler technology in response to common clinical intraoperative interventions, representing a limitation to how interchangeable these technologies are in measuring cardiac output.

Intra-Operative Fluid Management in Adult Neurosurgical Patients Undergoing Intracranial Tumour Surgery: Randomised Control Trial Comparing Pulse Pressure Variance (PPV) and Central Venous Pressure (CVP)

INTRODUCTION

Fluid management in neurosurgery presents specific challenges to the anaesthesiologist. Dynamic para-meters like Pulse Pressure Variation (PPV) have been used successfully to guide fluid management.

AIM

To compare PPV against Central Venous Pressure (CVP) in neurosurgical patients to assess hemodynamic stability and perfusion status.

MATERIALS AND METHODS

This was a single centre prospective randomised control trial at a tertiary care centre. A total of 60 patients undergoing intracranial tumour excision in supine and lateral positions were randomised to two groups (Group 1, CVP n=30), (Group 2, PPV n=30). Intra-operative fluid management was titrated to maintain baseline CVP in Group 1(5-10cm of water) and in Group 2 fluids were given to maintain PPV less than 13%. Acid base status, vital signs and blood loss were monitored.

RESULTS

Although intra-operative hypotension and acid base changes were comparable between the groups, the patients in the CVP group had more episodes of hypotension requiring fluid boluses in the first 24 hours post surgery. {CVP group median (25, 75) 2400ml (1850, 3110) versus PPV group 2100ml (1350, 2200) p=0.03} The patients in the PPV group received more fluids than the CVP group which was clinically significant. {2250 ml (1500, 3000) versus 1500ml (1200, 2000) median (25, 75) (p=0.002)}. The blood loss was not significantly different between the groups The median blood loss in the CVP group was 600ml and in the PPV group was 850 ml; p value 0.09.

CONCLUSION

PPV can be used as a reliable index to guide fluid management in neurosurgical patients undergoing tumour excision surgery in supine and lateral positions and can effectively augment CVP as a guide to fluid management. Patients in PPV group had better hemodynamic stability and less post operative fluid requirement.

Targeting Oliguria Reversal in Goal-Directed Hemodynamic Management Does Not Reduce Renal Dysfunction in Perioperative and Critically Ill Patients: A Systematic Review and Meta-Analysis

BACKGROUND

We investigated whether resuscitation protocols to achieve and maintain urine output above a predefined threshold-including oliguria reversal as a target--prevent acute renal failure (ARF).

METHODS

We performed a systematic review and meta-analysis using studies found by searching MEDLINE, EMBASE, and references in relevant reviews and articles. We included all studies that compared "conventional fluid management" (CFM) with "goal-directed therapy" (GDT) using cardiac output, urine output, or oxygen delivery parameters and reported the occurrence of ARF in critically ill or surgical patients. We divided studies into groups with and without oliguria reversal as a target for hemodynamic optimization. We calculated the combined odds ratio (OR) and 95% confidence intervals (CIs) using random-effects meta-analysis.

RESULTS

We based our analyses on 28 studies. In the overall analysis, GDT resulted in less ARF than CFM (OR, 0.58; 95% CI, 0.44-0.76; P < 0.001; I = 34.3%; n = 28). GDT without oliguria reversal as a target resulted in less ARF (OR, 0.45; 95% CI, 0.34-0.61; P < 0.001; I = 7.1%; n = 7) when compared with CFM with oliguria reversal as a target. The studies comparing GDT with CFM in which the reversal of oliguria was targeted in both or in neither group did not provide enough evidence to conclude a superiority of GDT (targeting oliguria reversal in both protocols: OR, 0.63; 95% CI, 0.36-1.10; P = 0.09; I = 48.6%; n = 9, and in neither protocol: OR, 0.66; 95% CI, 0.37-1.16; P = 0.14; I = 20.2%; n = 12).

CONCLUSIONS

Current literature favors targeting circulatory optimization by GDT without targeting oliguria reversal to prevent ARF. Future studies are needed to investigate the hypothesis that targeting oliguria reversal does not prevent ARF in critically ill and surgical patients.

Fluid therapy in the perioperative setting-a clinical review

BACKGROUND

Perioperative hypovolemia and fluid overload have effects on both complications following surgery and on patient survival. Therefore, the administration of intravenous fluids before, during, and after surgery at the right time and in the right amounts is of great importance. This review aims to analyze the literature concerning perioperative fluid therapy in abdominal surgery and to provide evidence-based recommendations for clinical practice.

RESULTS

Preoperative oral or intravenous administration of carbohydrate containing fluids has been shown to improve postoperative well-being and muscular strength and to reduce insulin resistance. Hence, the intake of fluid (preferably containing carbohydrates) should be encouraged up to 2 h prior to surgery in order to avoid dehydration. Excessive intravenous fluid administration adds to tissue inflammation and edema formation, thereby compromising tissue healing. During major abdominal surgery a "zero-balance" intraoperative fluid strategy aims at avoiding fluid overload (and comparable to the so-called restrictive approach) as well as goal-directed fluid therapy (GDT). Both proved to significantly reduce postoperative complications when compared to "standard fluid therapy". Trials comparing "restrictive" or zero-balance and GDT have shown equal results, as long as fluid overload is avoided in the GDT group as well (categorized as "zero-balance GDT"). It is possible that high-risk surgical patients, such as those undergoing acute surgery, may benefit from the continuous monitoring of circulatory status that the GDT provides. Data on this group of patients is not available at present, but trials are ongoing.

CONCLUSION

In elective surgery, the zero-balance approach has shown to reduce postoperative complications and is easily applied for most patients. It is less expensive and simpler than the zero-balance GDT approach and therefore recommended in this review. In outpatient surgery, 1-2 L of balanced crystalloids reduces postoperative nausea and vomiting and improves well-being.

Algorithm-guided goal-directed haemodynamic therapy does not improve renal function after major abdominal surgery compared to good standard clinical care: a prospective randomised trial

BACKGROUND

Acute kidney injury is a common complication after major surgery. In this study, we investigated whether an algorithm-guided goal-directed haemodynamic therapy (GDT) can improve renal outcome compared to good standard clinical care.

METHODS

A total of 180 patients undergoing major abdominal surgery were prospectively and randomly assigned to one of two groups: in the GDT group, patients were treated with a GDT algorithm using transpulmonary thermodilution while standard care was applied to the control patients. Change in creatinine was studied as the primary end point, postoperative complications as well as 1-year mortality as secondary outcomes. Haemodynamics in GDT and control patients were compared calculating goal-achievement rates.

RESULTS

Postoperative change in creatinine (18 ± 39 μmol/l (control) vs. 16 ± 42 μmol/l (GDT); mean difference (95 % confidence interval) 1.6 μmol/l (-10 to 13 μmol/l)) was comparable between the GDT and the control group. Postoperative complications and mortality during hospital stay and after 1 year were not influenced by the use of a GDT algorithm. Achievement rates of haemodynamic goals were not higher in the GDT group compared to the already high (>80 %) rates in the control group. Multivariate regression analysis revealed intraoperative hypotension (MAP < 70 mmHg) and postoperative hypovolaemia (GEDI < 640 ml/m(2)) as risk factors for postoperative renal impairment.

CONCLUSIONS

In this study, GDT was not superior to standard clinical care in order to avoid renal failure after major abdominal surgery. The reason for this finding is most likely the high achievement rate of haemodynamic goals in the control group, which cannot be improved by the GDT algorithm.

TRIAL REGISTRATION

Clinicaltrials.gov; NCT01035541; registered 17 December 2009.

Enhanced Recovery After Surgery (ERAS) for gastrointestinal surgery, part 2: consensus statement for anaesthesia practice

Background

The present interdisciplinary consensus review proposes clinical considerations and recommendations for anaesthetic practice in patients undergoing gastrointestinal surgery with an Enhanced Recovery after Surgery (ERAS) programme.

Methods

Studies were selected with particular attention being paid to meta‐analyses, randomized controlled trials and large prospective cohort studies. For each item of the perioperative treatment pathway, available English‐language literature was examined and reviewed. The group reached a consensus recommendation after critical appraisal of the literature.

Results

This consensus statement demonstrates that anaesthesiologists control several preoperative, intraoperative and postoperative ERAS elements. Further research is needed to verify the strength of these recommendations.

Conclusions

Based on the evidence available for each element of perioperative care pathways, the Enhanced Recovery After Surgery (ERAS ^®) Society presents a comprehensive consensus review, clinical considerations and recommendations for anaesthesia care in patients undergoing gastrointestinal surgery within an ERAS programme. This unified protocol facilitates involvement of anaesthesiologists in the implementation of the ERAS programmes and allows for comparison between centres and it eventually might facilitate the design of multi‐institutional prospective and adequately powered randomized trials.

Physiological Effects of the Open Lung Approach in Patients with Early, Mild, Diffuse Acute Respiratory Distress Syndrome: An Electrical Impedance Tomography Study

BACKGROUND

To test the hypothesis that in early, mild, acute respiratory distress syndrome (ARDS) patients with diffuse loss of aeration, the application of the open lung approach (OLA) would improve homogeneity in lung aeration and lung mechanics, without affecting hemodynamics.

METHODS

Patients were ventilated according to the ARDS Network protocol at baseline (pre-OLA). OLA consisted in a recruitment maneuver followed by a decremental positive end-expiratory pressure trial. Respiratory mechanics, gas exchange, electrical impedance tomography (EIT), cardiac index, and stroke volume variation were measured at baseline and 20 min after OLA implementation (post-OLA). Esophageal pressure was used for lung and chest wall elastance partitioning. The tomographic lung image obtained at the fifth intercostal space by EIT was divided in two ventral and two dorsal regions of interest (ROIventral and ROIDorsal).

RESULTS

Fifteen consecutive patients were studied. The OLA increased arterial oxygen partial pressure/inspired oxygen fraction from 216 ± 13 to 311 ± 19 mmHg (P < 0.001) and decreased elastance of the respiratory system from 29.4 ± 3 cm H2O/l to 23.6 ± 1.7 cm H2O/l (P < 0.01). The driving pressure (airway opening plateau pressure - total positive end-expiratory pressure) decreased from 17.9 ± 1.5 cm H2O pre-OLA to 15.4 ± 2.1 post-OLA (P < 0.05). The tidal volume fraction reaching the dorsal ROIs increased, and consequently the ROIVentral/Dorsal impedance tidal variation decreased from 2.01 ± 0.36 to 1.19 ± 0.1 (P < 0.01).

CONCLUSIONS

The OLA decreases the driving pressure and improves the oxygenation and lung mechanics in patients with early, mild, diffuse ARDS. EIT is useful to assess the impact of OLA on regional tidal volume distribution.

Intraoperative goal-directed hemodynamic management in free tissue transfer for head and neck cancer

BACKGROUND

The purpose of this study was to determine the effect of algorithmic physiologic management on patients undergoing head and neck free tissue transfer and reconstruction.

METHODS

Ninety-four adult patients were randomized to treatment and control groups. The blood pressure of the control group was managed consistent with contemporary standards. The treatment group was managed using an algorithm based on blood pressure and calculated physiologic values derived from arterial waveform analysis. Primary outcome was intensive care unit (ICU) length of stay.

RESULTS

ICU length of stay was decreased in the treatment group (33.7 vs 58.3 hours; p = .026). The complication rate was not increased in the treatment group.

CONCLUSION

The goal-directed hemodynamic management algorithm decreased the ICU length of stay. Judicious use of vasoactive drugs and goal-directed fluid administration has a role in improving perioperative outcomes for patients undergoing head and neck free tissue transfer. © 2016 Wiley Periodicals, Inc. Head Neck 38: E1974-E1980, 2016.

Intravenous fluids: should we go with the flow?

Sensitive monitoring should be used when prescribing intravenous fluids for volume resuscitation. The extent and duration of tissue hypoperfusion determine the severity of cellular damage, which should be kept to a minimum with timely volume substitution. Optimizing the filling status to normovolaemia may boost the resuscitation success. Macrocirculatory pressure values are not sensitive in this indication. While the Surviving Sepsis Campaign guidelines focus on these conventional pressure parameters, the guidelines from the European Society of Anaesthesiology (ESA) on perioperative bleeding management recommend individualized care by monitoring the actual volume status and correcting hypovolaemia promptly if present. The motto is: 'give what is missing'. The credo of the ESA guidelines is to use management algorithms with predefined intervention triggers. Stop signals should help in avoiding hyper-resuscitation. The high-quality evidence-based S3 guidelines on volume therapy in adults have recently been prepared by 14 German scientific societies. Statements include, for example, repeated clinical inspection including turgor of the skin and mucosa. Adjunctive laboratory parameters such as central venous oxygen saturation, lactate, base excess and haematocrit should be considered. The S3 guidelines propose the use of flow-based and/or dynamic preload parameters for guiding volume therapy. Fluid challenges and/or the leg-raising test (autotransfusion) should be performed. The statement from the Co-ordination group for Mutual Recognition and Decentralized Procedures--Human informs healthcare professionals to consider applying individualized medicine and using sensitive monitoring to assess hypovolaemia. The authorities encourage a personalized goal-directed volume resuscitation technique.

Anesthesia for colorectal surgery

Anesthesiologists play a pivotal role in facilitating recovery of patients undergoing colorectal surgery, as many Enhanced Recovery After Surgery (ERAS) elements are under their direct control. Successful implementation of ERAS programs requires that anesthesiologists become more involved in perioperative care and more aware of the impact of anesthetic techniques on surgical outcomes and recovery. Key to achieving success is strict adherence to the principle of aggregation of marginal gains. This article reviews anesthetic and analgesic care of patients undergoing elective colorectal surgery in the context of an ERAS program, and also discusses anesthesia considerations for emergency colorectal surgery.

Automated stroke volume and pulse pressure variations predict fluid responsiveness in mechanically ventilated patients with obstructive jaundice

BACKGROUND AND OBJECTIVES

Stroke volume variation (SVV) and the pulse pressure variation (PPV) have been found to be effective in prediction fluid responsiveness especially in high risk operations. The objective of this study is to validate the ability of SVV obtained by FloTrac/Vigileo system and PPV obtained by IntelliVue MP System to predict fluid responsiveness in patients with obstructive jaundice during mechanical ventilation.

METHODS

Twentyfive patients with obstructive jaundice (mean serum total bilirubin 175.0 ± 120.8 μmol/L), who accepted volume expansion and were hemodynamically stable after induction of anesthesia, were included in the study. SVV and PPV were recorded simultaneously before and after an intravascular volume expansion. Patients with a stroke volume index (SVI) increase of more than 10% after volume expansion were considered as responders.

RESULTS

The agreement (mean bias ± SD) between SVV and PPV was -0.2% ± 1.56%. Before volume expansion, SVV and PPV were significantly higher in responders compared to non-responders (P<0.001, P<0.001). Significant correlation was observed between the baseline value of SVV and PPV and the percent change in SVI after fluid expansion (r=0.654, P<0.001; r=0.592, P=0.002). Area under the receiver operating characteristic curves of SVV (0.955) and PPV (0.875) were comparable (P=0.09). The optimal threshold values in predicting fluid responsiveness were 10% for SVV and 8% for PPV.

CONCLUSION

In conclusion, SVV obtained by FloTrac/Vigileo system and PPV obtained by IntelliVue MP System was able to predict fluid responsiveness in patients with obstructive jaundice.

Potential return on investment for implementation of perioperative goal-directed fluid therapy in major surgery: a nationwide database study

Background

Preventable postsurgical complications are increasingly recognized as a major clinical and economic burden. A recent meta-analysis showed a 17–29 % decrease in postoperative morbidity with goal-directed fluid therapy. Our objective was to estimate the potential economic impact of perioperative goal-directed fluid therapy.

Methods

We studied 204,680 adult patients from 541 US hospitals who had a major non-cardiac surgical procedure between January 2011 and June 2013. Hospital costs (including 30-day readmission costs) in patients with and without complications were extracted from the Premier Inc. research database, and potential cost-savings associated with a 17–29 % decrease in postoperative morbidity were estimated.

Results

A total of 76,807 patients developed one or more postsurgical complications (morbidity rate 37.5 %). In patients with and without complications, hospital costs were US$27,607 ± 32,788 and US$15,783 ± 12,282 (p < 0.0001), respectively. Morbidity rate was anticipated to decrease to 26.6–31.1 % with goal-directed fluid therapy, yielding potential gross cost-savings of US$153–263 million for the study period, US$61–105 million per year, or US$754–1286 per patient. Potential savings per patient were highly variable from one surgical procedure to the other, ranging from US$354–604 for femur and hip-fracture repair to US$3515–5996 for esophagectomies. When taking into account the volume of procedures, the total potential savings per year were the most significant (US$32–55 million) for colectomies.

Conclusions

Postsurgical complications occurred in more than one third of our study population and had a dramatic impact on hospital costs. With goal-directed fluid therapy, potential cost-savings per patient were US$754–1286. The highest cost-savings per year were observed for colectomies. These projections should help hospitals estimate the return on investment when considering the implementation of goal-directed fluid therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13741-015-0021-0) contains supplementary material, which is available to authorized users.

Fluid management guided by a continuous non-invasive arterial pressure device is associated with decreased postoperative morbidity after total knee and hip replacement

Background

The use of goal directed fluid protocols in intermediate risk patients undergoing hip or knee replacement was studied in few trials using invasive monitoring. For this reason we have implemented two different fluid management protocols, both based on a novel totally non-invasive arterial pressure monitoring device and compared them to the standard (no-protocol) treatment applied before the transition in our academic institution.

Methods

Three treatment groups were compared in this prospective study: the observational (CONTROL, N = 40) group before adoption of fluid protocols and two randomized groups after the transition to protocol fluid management with the use of the continuous non-invasive blood pressure monitoring (CNAP®) device. In the PRESSURE group (N = 40) standard variables were used for restrictive fluid therapy. Goal directed fluid therapy using pulse pressure variation was used in the GDFT arm (N = 40). The influence on the rate of postoperative complications, on the hospital length of stay and other parameters was assessed.

Results

Both protocols were associated with decreased fluid administration and maintained hemodynamic stability. Reduced rate of postoperative infection and organ complications (22 (55 %) vs. 33 (83 %) patients; p = 0.016; relative risk 0.67 (0.49–0.91)) was observed in the GDFT group compared to CONTROL. Lower number of patients receiving transfusion (4 (10 %) in GDFT vs. 17 (43 %) in CONTROL; p = 0.005) might contribute to this observation. No significant differences were observed in other end-points.

Conclusion

In our study, the use of the fluid protocol based on pulse pressure variation assessed using continuous non-invasive arterial pressure measurement seems to be associated with a reduction in postoperative complications and transfusion needs as compared to standard no-protocol treatment.

Trial registration

ACTRN12612001014842

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-015-0131-8) contains supplementary material, which is available to authorized users.

Goal-Directed Resuscitation Aiming Cardiac Index Masks Residual Hypovolemia: An Animal Experiment

The aim of this study was to compare stroke volume (SVI) to cardiac index (CI) guided resuscitation in a bleeding-resuscitation experiment. Twenty six pigs were randomized and bled in both groups till baseline SVI (T_bsl) dropped by 50% (T₀), followed by resuscitation with crystalloid solution until initial SVI or CI was reached (T₄). Similar amount of blood was shed but animals received significantly less fluid in the CI-group as in the SVI-group: median = 900 (interquartile range: 850–1780) versus 1965 (1584–2165) mL, p = 0.02, respectively. In the SVI-group all variables returned to their baseline values, but in the CI-group animals remained underresuscitated as indicated by SVI, heart rate (HR) and stroke volume variation (SVV), and central venous oxygen saturation (S_cvO₂) at T₄ as compared to T_bsl: SVI = 23.8 ± 5.9 versus 31.4 ± 4.7 mL, HR: 117 ± 35 versus 89 ± 11/min SVV: 17.4 ± 7.6 versus 11.5 ± 5.3%, and S_cvO₂: 64.1 ± 11.6 versus 79.2 ± 8.1%, p < 0.05, respectively. Our results indicate that CI-based goal-directed resuscitation may result in residual hypovolaemia, as bleeding caused stress induced tachycardia “normalizes” CI, without restoring adequate SVI. As the SVI-guided approach normalized most hemodynamic variables, we recommend using SVI instead of CI as the primary goal of resuscitation during acute bleeding.

Effect of fluid loading with normal saline and 6% hydroxyethyl starch on stroke volume variability and left ventricular volume

Purpose

The aim of this clinical trial was to investigate changes in stroke volume variability (SVV) and left ventricular end-diastolic volume (LVEDV) after a fluid bolus of crystalloid or colloid using real-time three-dimensional transesophageal echocardiography (3D-TEE) and the Vigileo-FloTrac™ system.

Materials and methods

After obtaining Institutional Review Board approval, and informed consent from the research participants, 22 patients undergoing scheduled peripheral vascular bypass surgery were enrolled in the study. The patients were randomly assigned to receive 500 mL of hydroxyethyl starch (HES; HES group, n=11) or normal saline (Saline group, n=11) for fluid replacement therapy. SVV was measured using the Vigileo-FloTrac system. LVEDV, stroke volume, and cardiac output were measured by 3D-TEE. The measurements were performed over 30 minutes before and after the fluid bolus in both groups.

Results

SVV significantly decreased after fluid bolus in both groups (HES group, 14.7%±2.6% to 6.9%±2.7%, P<0.001; Saline group, 14.3%±3.9% to 8.8%±3.1%, P<0.001). LVEDV significantly increased after fluid loading in the HES group (87.1±24.0 mL to 99.9±27.2 mL, P<0.001), whereas no significant change was detected in the Saline group (88.8±17.3 mL to 91.4±17.6 mL, P>0.05). Stroke volume significantly increased after infusion in the HES group (50.6±12.5 mL to 61.6±19.1 mL, P<0.01) but not in the Saline group (51.6±13.4 mL to 54.1±12.8 mL, P>0.05). Cardiac output measured by 3D-TEE significantly increased in the HES group (3.5±1.1 L/min to 3.9±1.3 L/min, P<0.05), whereas no significant change was seen in the Saline group (3.4±1.1 L/min to 3.3±1.0 L/min, P>0.05).

Conclusion

Administration of colloid and crystalloid induced similar responses in SVV. A higher plasma-expanding effect of HES compared to normal saline was demonstrated by the significant increase in LVEDV.

Advances in photoplethysmography: beyond arterial oxygen saturation

PURPOSE

Photoplethysmography permits continuous measurement of heart rate and peripheral oxygen saturation and has been widely used to inform clinical decisions. Recently, a myriad of noninvasive hemodynamic monitoring devices using this same technology have been increasingly available. This narrative review aims to summarize the principles that form the basis for the function of these devices as well as to comment on trials evaluating their accuracy and clinical application.

PRINCIPAL FINDINGS

Advanced monitoring devices extend photoplethysmography technology beyond measuring oxygen concentration and heart rate. Quantification of respiratory variation of the photoplethysmographic waveform reflects respiratory variation of the arterial pressure waveform and can be used to gauge volume responsiveness. Both the volume-clamp and physiocal techniques are extensions of conventional photoplethysmography and permit continuous measurement of finger arterial blood pressure. Finger arterial pressure waveforms can subsequently inform estimations of cardiac output.

CONCLUSIONS

Although respiratory variations of the plethysmographic waveform correlate only modestly with the arterial blood pressure waveform, fluid responsiveness can be relatively consistently assessed using both approaches. Continuous blood pressure measurements obtained using the volume-clamp technique may be as accurate as conventional brachial noninvasive blood pressure measurements. Most importantly, clinical comparative effectiveness studies are still needed in order to determine if these technologies can be translated into improvement of relevant patient outcomes.

Crystalloid administration among patients undergoing liver surgery: Defining patient- and provider-level variation

BACKGROUND

Fluid administration among patients undergoing liver resection is a key aspect of perioperative care. We sought to examine practice patterns of crystalloid administration, as well as potential factors associated with receipt of crystalloid fluids.

METHOD

Patients who underwent liver resection between 2010 and 2014 were identified. Data on clinicopathologic variables, operative details, and perioperative fluid administration were collected and analyzed using univariable and multivariable analyses; variation in practice of crystalloid administration was presented as coefficient of variation (COV).

RESULTS

Among 487 patients, median crystalloid administered at the time of surgery was 4,000 mL. After adjusting for body size and operative duration, median corrected crystalloid was 30.0 mL kg(-1) m(2) h(-1), corresponding with a COV of 35%. Patients who received <30 mL kg(-1) m(2) h(-1) crystalloids were more likely to be younger (58 vs 60 years), white (79% vs 74%), and have a higher body mass index (BMI; 28.2 vs 25.4 kg/m(2); all P < .001). On multivariable analysis, increasing Charlson comorbidity index, BMI, estimated blood loss, and each additional hour of surgery were all associated with increased crystalloid administration (all P < .05). Corrected crystalloid administration varied among providers with a corrected COV ranging from 14% to 61%. When overall variation in crystalloid administration was assessed, 80% of the variation occurred at the patient level, and 20% occurred at the provider level (surgeon, 3% vs anesthesiologist, 17%).

CONCLUSION

There was wide variability in crystalloid administration among patients undergoing liver resection. Although the majority of variation was attributable to patient factors, a large amount of residual variation was attributable to provider-level differences.

Using what you get: dynamic physiologic signatures of critical illness

The development and resolution of cardiopulmonary instability take time to become clinically apparent, and the treatments provided take time to have an impact. The characterization of dynamic changes in hemodynamic and metabolic variables is implicit in physiologic signatures. When primary variables are collected with high enough frequency to derive new variables, this data hierarchy can be used to develop physiologic signatures. The creation of physiologic signatures requires no new information; additional knowledge is extracted from data that already exist. It is possible to create physiologic signatures for each stage in the process of clinical decompensation and recovery to improve outcomes.

Minimally invasive monitoring

Although use of the classic pulmonary artery catheter has declined, several techniques have emerged to estimate cardiac output. Arterial pressure waveform analysis computes cardiac output from the arterial pressure curve. The method of estimating cardiac output for these devices depends on whether they need to be calibrated by an independent measure of cardiac output. Some newer devices have been developed to estimate cardiac output from an arterial curve obtained noninvasively with photoplethysmography, allowing a noninvasive beat-by-beat estimation of cardiac output. This article describes the different devices that perform pressure waveform analysis.

Defining goals of resuscitation in the critically ill patient

There is still no "universal" consensus on an optimal endpoint for goal directed therapy (GDT) in the critically ill patient. As in other areas of medicine, this should help providers to focus on a more "individualized approach" rather than a protocolized approach to ensure proper patient care. Hemodynamic optimization needs more than simply blood pressure, heart rate, central venous pressure and urine output monitoring. It is essential to also monitor flow variables (cardiac output/stroke volume) and dynamic parameters of fluid responsiveness whenever available. This article will provide a review of current and trending approaches of the goals of resuscitation in the critically ill patient.

Stroke volume variation to guide fluid therapy: is it suitable for high-risk surgical patients? A terminated randomized controlled trial

Background

Perioperative goal-directed fluid therapy (GDFT) may improve outcome after high-risk surgery. Minimal invasive measurement of stroke volume variation (SVV) has been recommended to guide fluid therapy. We intended to study how perioperative GDFT with arterial-based continuous SVV monitoring influences postoperative complications in a high-risk surgical population.

Methods

From February 1st 2012, all ASA 3 and 4 patients undergoing abdominal surgery in two university hospitals were assessed for randomization into a control group or GDFT group. An arterial-line cardiac output monitor was used to measure SVV, and fluid was given after an algorithm in the intervention group. Restrictions of the method excluded patients undergoing laparoscopic surgery, patients with atrial fibrillation and patients with severe mitral/aortal stenosis. To detect a decrease in number of complication from 40 % in the control group to 20 % in the GDFT group, n = 164 patients were needed (power 80 %, alpha 0.05, two-sided test). To include the needed amount of patients, the study was estimated to last for 2 years.

Results

After 1 year, 30 patients were included and the study was halted due to slow inclusion rate. Of 732 high-risk patients scheduled for abdominal surgery, 391 were screened for randomization. Of those, n = 249 (64 %) were excluded because a laparoscopic technique was preferred and n = 95 (24 %) due to atrial fibrillation.

Conclusions

Our study was stopped due to a slow inclusion rate. Methodological restrictions of the arterial-line cardiac output monitor excluded the majority of patients. This leaves the question if this method is appropriate to guide fluid therapy in high-risk surgical patients.

Trial registration

ClinicalTrials.gov: NCT01473446.

Electronic supplementary material

The online version of this article (doi:10.1186/s13741-015-0016-x) contains supplementary material, which is available to authorized users.

Goal-Directed Fluid Therapy Guided by Cardiac Monitoring During High-Risk Abdominal Surgery in Adult Patients: Cost-Effectiveness Analysis of Esophageal Doppler and Arterial Pulse Pressure Waveform Analysis

BACKGROUND

Several minimally invasive techniques for cardiac output monitoring such as the esophageal Doppler (ED) and arterial pulse pressure waveform analysis (APPWA) have been shown to improve surgical outcomes compared with conventional clinical assessment (CCA).

OBJECTIVE

To evaluate the cost-effectiveness of these techniques in high-risk abdominal surgery from the perspective of the French public health insurance fund.

METHODS

An analytical decision model was constructed to compare the cost-effectiveness of ED, APPWA, and CCA. Effectiveness data were defined from meta-analyses of randomized clinical trials. The clinical end points were avoidance of hospital mortality and avoidance of major complications. Hospital costs were estimated by the cost of corresponding diagnosis-related groups.

RESULTS

Both goal-directed therapy strategies evaluated were more effective and less costly than CCA. Perioperative mortality and the rate of major complications were reduced by the use of ED and APPWA. Cost reduction was mainly due to the decrease in the rate of major complications. APPWA was dominant compared with ED in 71.6% and 27.6% and dominated in 23.8% and 20.8% of the cases when the end point considered was "major complications avoided" and "death avoided," respectively. Regarding cost per death avoided, APPWA was more likely to be cost-effective than ED in a wide range of willingness to pay.

CONCLUSIONS

Cardiac output monitoring during high-risk abdominal surgery is cost-effective and is associated with a reduced rate of hospital mortality and major complications, whatever the device used. The two devices evaluated had negligible costs compared with the observed reduction in hospital costs. Our comparative studies suggest a larger effect with APPWA that needs to be confirmed by further studies.

[Optimization of infusion therapy in large abdominal operations]

Volume and consist of infusion therapy determine in many respects postoperative period in patients who underwent large abdominal operations. Purposeful infusion therapy controlled according to monitoring of stroke volume variability is perspective. It was proved that evaluation of this parameter allows to optimize consist and volume of transfused solutions intraoperatively. Use of purposeful infusion therapy was accompanied by decreasing of number of postoperative complications and duration of intensive care unit stay after large abdominal operations.

Colloids versus crystalloids in objective-guided fluid therapy, systematic review and meta-analysis. Too early or too late to draw conclusions

INTRODUCTION

Several clinical trials on Goal directed fluid therapy (GDFT) were carried out, many of those using colloids in order to optimize the preload. After the decision of European Medicines Agency, there is such controversy regarding its use, benefits, and possible contribution to renal failure. The objective of this systematic review and meta-analysis is to compare the use of last-generation colloids, derived from corn, with crystalloids in GDFT to determine associated complications and mortality.

METHODS

A bibliographic research was carried out in MEDLINE PubMed, EMBASE and Cochrane Library, corroborating randomized clinical trials where crystalloids are compared to colloids in GDFT for major non-cardiac surgery in adults.

RESULTS

One hundred thirty references were found and among those 38 were selected and 29 analyzed; of these, six were included for systematic review and meta-analysis, including 390 patients. It was observed that the use of colloids is not associated with the increase of complications, but rather with a tendency to a higher mortality (RR [95% CI] 3.87 [1.121-13.38]; I(2)=0.0%; p=0.635).

CONCLUSIONS

Because of the limitations of this meta-analysis due to the small number of randomized clinical trials and patients included, the results should be taken cautiously, and the performance of new randomized clinical trials is proposed, with enough statistical power, comparing balanced and unbalanced colloids to balanced and unbalanced crystalloids, following the protocols of GDFT, considering current guidelines and suggestions made by groups of experts.

Perioperative fluid therapy: a statement from the international Fluid Optimization Group

BACKGROUND

Perioperative fluid therapy remains a highly debated topic. Its purpose is to maintain or restore effective circulating blood volume during the immediate perioperative period. Maintaining effective circulating blood volume and pressure are key components of assuring adequate organ perfusion while avoiding the risks associated with either organ hypo- or hyperperfusion. Relative to perioperative fluid therapy, three inescapable conclusions exist: overhydration is bad, underhydration is bad, and what we assume about the fluid status of our patients may be incorrect. There is wide variability of practice, both between individuals and institutions. The aims of this paper are to clearly define the risks and benefits of fluid choices within the perioperative space, to describe current evidence-based methodologies for their administration, and ultimately to reduce the variability with which perioperative fluids are administered.

METHODS

Based on the abovementioned acknowledgements, a group of 72 researchers, well known within the field of fluid resuscitation, were invited, via email, to attend a meeting that was held in Chicago in 2011 to discuss perioperative fluid therapy. From the 72 invitees, 14 researchers representing 7 countries attended, and thus, the international Fluid Optimization Group (FOG) came into existence. These researches, working collaboratively, have reviewed the data from 162 different fluid resuscitation papers including both operative and intensive care unit populations. This manuscript is the result of 3 years of evidence-based, discussions, analysis, and synthesis of the currently known risks and benefits of individual fluids and the best methods for administering them.

RESULTS

The results of this review paper provide an overview of the components of an effective perioperative fluid administration plan and address both the physiologic principles and outcomes of fluid administration.

CONCLUSIONS

We recommend that both perioperative fluid choice and therapy be individualized. Patients should receive fluid therapy guided by predefined physiologic targets. Specifically, fluids should be administered when patients require augmentation of their perfusion and are also volume responsive. This paper provides a general approach to fluid therapy and practical recommendations.

A randomized trial of goal directed vs. standard fluid therapy in cytoreductive surgery with hyperthermic intraperitoneal chemotherapy

The use of adequate fluid therapy during cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) remains controversial. The aim of the study was to assess whether the use of fluid therapy protocol combined with goal-directed therapy (GDT) is associated with a significant change in morbidity, length of hospital stay, and mortality compared to standard fluid therapy. Patients American Society of Anesthesiologists (ASA) II-III undergoing CRS and HIPEC were randomized into two groups. The GDT group (N = 38) received fluid therapy according to a protocol guided by monitored hemodynamic parameters. The control group (N = 42) received standard fluid therapy. We evaluated incidence of major complications, total length of hospital stay, total amount of fluids administered, and mortality rate. The incidence of major abdominal complications was 10.5% in GDT group and 38.1% in the control group (P = 0.005). The median duration of hospitalization was 19 days in GDT group and 29 days in the control group (P < 0.0001). The mortality rate was zero in GDT group vs. 9.5% in the control group (P = 0.12). GDT group received a significantly (P < 0.0001) lower amount of fluid (5812 ± 1244 ml) than the control group (8269 ± 1452 ml), with a significantly (P < 0.0001) lower volume of crystalloids (3884 ± 1003 vs. 68,528 ± 1413 ml). In CRS and HIPEC, the use of a GDT improves outcome in terms of incidence of major abdominal and systemic postoperative complications and length of hospital stay, compared to standard fluid therapy protocol.

Meta-analysis of the effect of goal-directed therapy on bowel function after abdominal surgery

Background

Intraoperative goal-directed therapy (GDT) was introduced to titrate intravenous fluids, with or without inotropic drugs, based on objective measures of hypovolaemia and cardiac output measurements to improve organ perfusion. This meta-analysis aimed to determine the effect of GDT on the recovery of bowel function after abdominal surgery.

Methods

MEDLINE, Embase, the Cochrane Library and PubMed databases were searched for randomized clinical trials and cohort studies, from January 1989 to June 2013, that compared patients who did, or did not, receive intraoperative GDT, and reported outcomes on the recovery of bowel function. Time to first flatus and first bowel motion, time to tolerate oral diet, postoperative nausea and vomiting, and primary postoperative ileus were included.

Results

Thirteen trials with 1399 patients were included in the analysis. GDT shortened the time to the first bowel motion (weighted mean difference (WMD −0·67, 95 per cent c.i. −1·23 to −0·11; P = 0·020) and time to tolerate oral intake (WMD −0·95, −1·81 to −0·10; P = 0·030), and reduced postoperative nausea and vomiting (risk difference −0·15, −0·26 to −0·03; P = 0·010). When only high-quality studies were included, GDT reduced only the time to tolerate oral intake (WMD −1·18, −2·03 to −0·33; P = 0·006). GDT was more effective outside enhanced recovery programmes and in patients undergoing colorectal surgery.

Conclusion

GDT facilitated the recovery of bowel function, particularly in patients not treated within enhanced recovery programmes and in those undergoing colorectal operations.

Anesthesia for esophagectomy

Esophagectomy is a high-risk operation with significant perioperative morbidity and mortality. Attention to detail in many areas of perioperative management should lead to an aggregation of marginal gains and improvement in postoperative outcome. This review addresses preoperative assessment and patient selection, perioperative care (focusing on pulmonary prehabilitation, ventilation strategies, goal-directed fluid therapy, analgesia, and cardiovascular complications), minimally invasive surgery, and current evidence for enhanced recovery in esophagectomy.

Preload dependence indices to titrate volume expansion during septic shock: a randomized controlled trial

INTRODUCTION

In septic shock, pulse pressure or cardiac output variation during passive leg raising are preload dependence indices reliable at predicting fluid responsiveness. Therefore, they may help to identify those patients who need intravascular volume expansion, while avoiding unnecessary fluid administration in the other patients. However, whether their use improves septic shock prognosis remains unknown. The aim of this study was to assess the clinical benefits of using preload dependence indices to titrate intravascular fluids during septic shock.

METHODS

In a single-center randomized controlled trial, 60 septic shock patients were allocated to preload dependence indices-guided (preload dependence group) or central venous pressure-guided (control group) intravascular volume expansion with 30 patients in each group. The primary end point was time to shock resolution, defined by vasopressor weaning.

RESULTS

There was no significant difference in time to shock resolution between groups (median (interquartile range) 2.0 (1.2 to 3.1) versus 2.3 (1.4 to 5.6) days in control and preload dependence groups, respectively). The daily amount of fluids administered for intravascular volume expansion was higher in the control than in the preload dependence group (917 (639 to 1,511) versus 383 (211 to 604) mL, P = 0.01), and the same held true for red cell transfusions (178 (82 to 304) versus 103 (0 to 183) mL, P = 0.04). Physiologic variable values did not change over time between groups, except for plasma lactate (time over group interaction, P <0.01). Mortality was not significantly different between groups (23% in the preload dependence group versus 47% in the control group, P = 0.10). Intravascular volume expansion was lower in the preload dependence group for patients with lower simplified acute physiology score II (SAPS II), and the opposite was found for patients in the upper two SAPS II quartiles. The amount of intravascular volume expansion did not change across the quartiles of severity in the control group, but steadily increased with severity in the preload dependence group.

CONCLUSIONS

In patients with septic shock, titrating intravascular volume expansion with preload dependence indices did not change time to shock resolution, but resulted in less daily fluids intake, including red blood cells, without worsening patient outcome.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01972828. Registered 11 October 2013.

Endpoints of resuscitation

Despite the multiple causes of the shock state, all causes possess the common abnormality of oxygen supply not meeting tissue metabolic demands. Compensatory mechanisms may mask the severity of hypoxemia and hypoperfusion, since catecholamines and extracellular fluid shifts initially compensate for the physiologic derangements associated with patients in shock. Despite the achievement of normal physiologic parameters after resuscitation, significant metabolic acidosis may continue to be present in the tissues, as evidenced by increased lactate levels and metabolic acidosis. This review discusses the major endpoints of resuscitation in clinical use.

New tools for optimizing fluid resuscitation in acute pancreatitis

Acute pancreatitis (AP) is a frequent disease with degrees of increasing severity responsible for high morbidity. Despite continuous improvement in care, mortality remains significant. Because hypovolemia, together with microcirculatory dysfunction lead to poor outcome, fluid therapy remains a cornerstone of the supportive treatment. However, poor clinical evidence actually support the aggressive fluid therapy recommended in recent guidelines since available data are controversial. Fluid management remains unclear and leads to current heterogeneous practice. Different strategies may help to improve fluid resuscitation in AP. On one hand, integration of fluid therapy in a global hemodynamic resuscitation has been demonstrated to improve outcome in surgical or septic patients. Tailored fluid administration after early identification of patients with high-risk of poor outcome presenting inadequate tissue oxygenation is a major part of this strategy. On the other hand, new decision parameters have been developed recently to improve safety and efficiency of fluid therapy in critically ill patients. In this review, we propose a personalized strategy integrating these new concepts in the early fluid management of AP. This new approach paves the way to a wide range of clinical studies in the field of AP.

Bayesian methodology for the design and interpretation of clinical trials in critical care medicine: a primer for clinicians

OBJECTIVES

To review Bayesian methodology and its utility to clinical decision making and research in the critical care field.

DATA SOURCE AND STUDY SELECTION

Clinical, epidemiological, and biostatistical studies on Bayesian methods in PubMed and Embase from their inception to December 2013.

DATA SYNTHESIS

Bayesian methods have been extensively used by a wide range of scientific fields, including astronomy, engineering, chemistry, genetics, physics, geology, paleontology, climatology, cryptography, linguistics, ecology, and computational sciences. The application of medical knowledge in clinical research is analogous to the application of medical knowledge in clinical practice. Bedside physicians have to make most diagnostic and treatment decisions on critically ill patients every day without clear-cut evidence-based medicine (more subjective than objective evidence). Similarly, clinical researchers have to make most decisions about trial design with limited available data. Bayesian methodology allows both subjective and objective aspects of knowledge to be formally measured and transparently incorporated into the design, execution, and interpretation of clinical trials. In addition, various degrees of knowledge and several hypotheses can be tested at the same time in a single clinical trial without the risk of multiplicity. Notably, the Bayesian technology is naturally suited for the interpretation of clinical trial findings for the individualized care of critically ill patients and for the optimization of public health policies.

CONCLUSIONS

We propose that the application of the versatile Bayesian methodology in conjunction with the conventional statistical methods is not only ripe for actual use in critical care clinical research but it is also a necessary step to maximize the performance of clinical trials and its translation to the practice of critical care medicine.

Inter-device differences in monitoring for goal-directed fluid therapy

PURPOSE

Goal-directed fluid therapy is an integral component of many Enhanced Recovery After Surgery (ERAS) protocols currently in use. The perioperative clinician is faced with a myriad of devices promising to deliver relevant physiologic data to better guide fluid therapy. The goal of this review is to provide concise information to enable the clinician to make an informed decision when choosing a device to guide goal-directed fluid therapy.

PRINCIPAL FINDINGS

The focus of many devices used for advanced hemodynamic monitoring is on providing measurements of cardiac output, while other, more recent, devices include estimates of fluid responsiveness based on dynamic indices that better predict an individual's response to a fluid bolus. Currently available technologies include the pulmonary artery catheter, esophageal Doppler, arterial waveform analysis, photoplethysmography, venous oxygen saturation, as well as bioimpedance and bioreactance. The underlying mechanistic principles for each device are presented as well as their performance in clinical trials relevant for goal-directed therapy in ERAS.

CONCLUSIONS

The ERAS protocols typically involve a multipronged regimen to facilitate early recovery after surgery. Optimizing perioperative fluid therapy is a key component of these efforts. While no technology is without limitations, the majority of the currently available literature suggests esophageal Doppler and arterial waveform analysis to be the most desirable choices to guide fluid administration. Their performance is dependent, in part, on the interpretation of dynamic changes resulting from intrathoracic pressure fluctuations encountered during mechanical ventilation. Evolving practice patterns, such as low tidal volume ventilation as well as the necessity to guide fluid therapy in spontaneously breathing patients, will require further investigation.

The effects of goal-directed fluid therapy based on dynamic parameters on post-surgical outcome: a meta-analysis of randomized controlled trials

Introduction

Dynamic predictors of fluid responsiveness, namely systolic pressure variation, pulse pressure variation, stroke volume variation and pleth variability index have been shown to be useful to identify in advance patients who will respond to a fluid load by a significant increase in stroke volume and cardiac output. As a result, they are increasingly used to guide fluid therapy. Several randomized controlled trials have tested the ability of goal-directed fluid therapy (GDFT) based on dynamic parameters (GDFTdyn) to improve post-surgical outcome. These studies have yielded conflicting results. Therefore, we performed this meta-analysis to investigate whether the use of GDFTdyn is associated with a decrease in post-surgical morbidity.

Methods

A systematic literature review, using MEDLINE, EMBASE, and The Cochrane Library databases through September 2013 was conducted. Data synthesis was obtained by using odds ratio (OR) and weighted mean difference (WMD) with 95% confidence interval (CI) by random-effects model.

Results

In total, 14 studies met the inclusion criteria (961 participants). Post-operative morbidity was reduced by GDFTdyn (OR 0.51; CI 0.34 to 0.75; P <0.001). This effect was related to a significant reduction in infectious (OR 0.45; CI 0.27 to 0.74; P = 0.002), cardiovascular (OR 0.55; CI 0.36 to 0.82; P = 0.004) and abdominal (OR 0.56; CI 0.37 to 0.86; P = 0.008) complications. It was associated with a significant decrease in ICU length of stay (WMD −0.75 days; CI −1.37 to −0.12; P = 0.02).

Conclusions

In surgical patients, we found that GDFTdyn decreased post-surgical morbidity and ICU length of stay. Because of the heterogeneity of studies analyzed, large prospective clinical trials would be useful to confirm our findings.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0584-z) contains supplementary material, which is available to authorized users.