Functional intravascular volume deficit in patients before surgery

Prevention of hypotension after induction of general anesthesia using point-of-care ultrasound to guide fluid management: a randomized controlled trial

PURPOSE

Hypotension after induction of general anesthesia (GAIH) is common and is associated with postoperative complications including increased mortality. Collapsibility of the inferior vena cava (IVC) has good performance in predicting GAIH; however, there is limited evidence whether a preoperative fluid bolus in patients with a collapsible IVC can prevent this drop in blood pressure.

METHODS

We conducted a single-centre randomized controlled trial with adult patients scheduled to undergo elective noncardiac surgery under general anesthesia (GA). Patients underwent a preoperative point-of-care ultrasound scan (POCUS) to identify those with a collapsible IVC (IVC collapsibility index ≥ 43%). Individuals with a collapsible IVC were randomized to receive a preoperative 500 mL fluid bolus or routine care (control group). Surgical and anesthesia teams were blinded to the results of the scan and group allocation. Hypotension after induction of GA was defined as the use of vasopressors/inotropes or a decrease in mean arterial pressure < 65 mm Hg or > 25% from baseline within 20 min of induction of GA.

RESULTS

Forty patients (20 in each group) were included. The rate of hypotension after induction of GA was significantly reduced in those receiving preoperative fluids (9/20, 45% vs 17/20, 85%; relative risk, 0.53; 95% confidence interval, 0.32 to 0.89; P = 0.02). The mean (standard deviation) time to complete POCUS was 4 (2) min, and the duration of fluid bolus administration was 14 (5) min. Neither surgical delays nor adverse events occurred as a result of the study intervention.

CONCLUSION

A preoperative fluid bolus in patients with a collapsible IVC reduced the incidence of GAIH without associated adverse effects.

STUDY REGISTRATION

ClinicalTrials.gov (NCT05424510); first submitted 15 June 2022.

Feasibility of Goal-Directed Fluid Therapy in Patients with Transcatheter Aortic Valve Replacement - An Ambispective Analysis

INTRODUCTION

Goal-directed fluid therapy (GDFT) has been shown to reduce postoperative complications. The feasibility of GDFT in transcatheter aortic valve replacement (TAVR) patients under general anesthesia has not yet been demonstrated. We examined whether GDFT could be applied in patients undergoing TAVR in general anesthesia and its impact on outcomes.

METHODS

Forty consecutive TAVR patients in the prospective intervention group with GDFT were compared to 40 retrospective TAVR patients without GDFT. Inclusion criteria were age ≥ 18 years, elective TAVR in general anesthesia, no participation in another interventional study. Exclusion criteria were lack of ability to consent study participation, pregnant or nursing patients, emergency procedures, preinterventional decubitus, tissue and/or extremity ischemia, peripheral arterial occlusive disease grade IV, atrial fibrillation or other severe heart rhythm disorder, necessity of usage of intra-aortic balloon pump. Stroke volume and stroke volume variation were determined with uncalibrated pulse contour analysis and optimized according to a predefined algorithm using 250 ml of hydroxyethyl starch.

RESULTS

Stroke volume could be increased by applying GDFT. The intervention group received more colloids and fewer crystalloids than control group. Total volume replacement did not differ. The incidence of overall complications as well as intensive care unit and hospital length of stay were comparable between both groups. GDFT was associated with a reduced incidence of delirium. Duration of anesthesia was shorter in the intervention group. Duration of the interventional procedure did not differ.

CONCLUSION

GDFT in the intervention group was associated with a reduced incidence of postinterventional delirium.

Differences in Hemodynamic Response to Passive Leg Raising Tests during the Day in Healthy Individuals: The Question of Normovolemia

BACKGROUND

The passive leg-raising (PLR) test was developed to predict fluid responsiveness and reduce fluid overload. However, the hemodynamic response of healthy individuals to the PLR test and how it changes during the day, between the morning and evening, after individuals have consumed food and fluids, has not been profoundly explored. This study aimed to compare the systemic hemodynamic changes in healthy individuals between morning and evening PLR tests.

METHODS

In this study, the PLR test was performed twice a day. The first PLR test was performed between 08h00 and 09h00 in the morning, while the second PLR test was performed between 20h00 and 21h00 in the evening. Hemodynamic parameters were measured using an impedance cardiography monitor, and a cutoff value of a 10% increase in stroke volume (SV) during the PLR test was used to differentiate between preload responders and non-responders.

RESULTS

We included 50 healthy volunteers in this study. When comparing the morning and evening PLR test results, we found no PLR-induced differences in heart rate (-3 [-8-2] vs. -2 [-8-4] beats/min, p = 0.870), SV (11 [5-22] vs. 12 [4-20] mL, p = 0.853) or cardiac output (0.7 [0.2-1.3] vs. 0.8 [0.1-1.4] L/min, p = 0.639). We also observed no differences in the proportion of preload responders during the PLR test between the morning and evening (64% vs. 66%, p = 0.99). However, there was a moderate agreement between the two PLR tests (morning and evening) (kappa = 0.429, p = 0.012). There was a moderate correlation between the changes in SV between the two PLR tests (r_s = 0.50, p < 0.001).

CONCLUSION

In young, healthy individuals, we observed no change in the systemic hemodynamic responsiveness to the PLR test between the morning and evening, without restriction of fluid and food intake.

Impact of bedside ultrasound to reduce the incidence of acute renal injury in high-risk surgical patients: a randomized clinical trial

PURPOSE

This study aimed to determine whether performing bedside ultrasound impacts the occurrence of acute kidney injury (AKI) in the immediate postoperative period (POP) of high-risk surgery patients.

METHODS

POP patients were randomly assigned to two groups: (i) ultrasound (US) group, in which hemodynamic management was guided with clinical parameters supplemented with the bedside US findings; (ii) control group, hemodynamic management based solely on clinical parameters. Two exams were performed in the first 24 h of admission.

RESULTS

Fifty-one patients were randomized to the US group and 60 to the control group. There was no significant difference for incidence of AKI in both groups assessed 12 h (31.4% vs 35.0%, P = 0.84), 24 h (27.5% vs 23.3%, P = 0.66), or 7 days (17.6 vs 8.3%, P = 0.16) after surgery. No difference was found in the amounts of volume administered over the first 12 h (1000 [500-2000] vs. 1000 [500-1500], P = 0.72) and 24 h (1000 [0-1500] vs. 1000 [0-1500], P = 0.95) between the groups. Patients without AKI in the control group received higher amounts of volume during the ICU stay.

CONCLUSION

The use of bedside US in the immediate postoperative period of high-risk surgery did not show benefits in reducing AKI incidence.

To identify normovolemia in humans: The stroke volume response to passive leg raising vs. head-down tilt

Volume responsiveness can be evaluated by tilting maneuvers such as head-down tilt (HDT) and passive leg raising (PLR), but the two procedures use different references (HDT the supine position; PLR the semi-recumbent position). We tested whether the two procedures identify "normovolemia" by evaluating the stroke volume (SV) and cardiac output (CO) responses and whether the peripheral perfusion index (PPI) derived from pulse oximetry provides similar information. In randomized order, 10 healthy men were exposed to both HDT and PLR, and evaluations were made also when the subjects fasted. Central cardiovascular variables were derived by pulse contour analysis and changes in central blood volume assessed by thoracic electrical admittance (TEA). During HDT, SV remained stable (fasted 110 ± 16 vs. 109 ± 16 ml; control 113 ± 16 vs. 111 ± 16 ml, p > 0.05) with no change in CO, TEA, PPI, or SV variation (SVV). In contrast during PLR, SV increased (fasted 108 ± 17 vs. 117 ± 17 ml; control 108 ± 18 vs. 117 ± 18 ml, p < 0.05) followed by an increase in TEA (p < 0.05) and CO increased when subjects fasted (6.7 ± 1.5 vs. 7.1 ± 1.5, p = 0.007) with no change in PPI or SVV. In conclusion, SV has a maximal value for rest in supine men, while PLR restores SV as CBV is reduced in a semi-recumbent position and the procedure thereby makes healthy volunteers seem fluid responsive.

Different preoperative fluids do not affect the hemodynamic status but gastric volume: results of a randomized crossover pilot study

Background and objective

Inferior vena cava (IVC) examination has been reported as a noninvasive method for evaluating the hemodynamic state. We conducted this crossover pilot study to investigate the effects of the administration of water and high-carbohydrate-containing fluids on the hemodynamic status of volunteers through collapsibility index of IVC (IVCCI) measurement.

Methods

Twenty volunteers were randomly assigned to a water or high-carbohydrate group according to computer-generated random numbers in a 1:1 ratio. In the water group, volunteers received water (5 mL/kg), and in the high-carbohydrate group, patients received carbohydrate drinks (5 mL/kg). Respiratory variations in the IVC diameter, gastric volume, and blood pressure and heart rates in erect and supine positions were measured at admission (T1), 1 h (T2), 2 h (T3), 3 h (T4), and 4 h (T5).

Results

When considering participants with an IVCCI of more than 42%, there were no significant differences between the water and carbohydrate drink groups at each time point (all p > 0.05). At T2, more participants had an empty stomach in water group than in carbohydrate drink group (p < 0.001). At T3, 30% of the participants could not empty their stomachs in carbohydrate drink group. However, with regard to the number of volunteers with empty stomach at T3, there was no significant difference between water and carbohydrate drink group. Repeated measures data analysis demonstrated that IVCCI showed no significant differences over time (p = 0.063 for T1-T5). There were no differences between water and carbohydrate drinks (p = 0.867).

Conclusion

Our results suggested that neither water nor carbohydrate drinking affected the hemodynamic status through IVCCI measurement over time, up to 4 h after drinking. Furthermore, carbohydrate drinking might delay gastric emptying at 1 h, but not 2 h after drinking, in comparison with water.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01697-3.

Intraoperative Assessment of Fluid Responsiveness in Normotensive Dogs under Isoflurane Anaesthesia

The aim of this study was to evaluate the incidence of fluid responsiveness (FR) to a fluid challenge (FC) in normotensive dogs under anaesthesia. The accuracy of pulse pressure variation (PPV), systolic pressure variation (SPV), stroke volume variation (SVV), and plethysmographic variability index (PVI) for predicting FR was also evaluated. Dogs were anaesthetised with methadone, propofol, and inhaled isoflurane in oxygen, under volume-controlled mechanical ventilation. FC was performed by the administration of 5 mL/kg of Ringer's lactate within 5 min. Cardiac index (CI; L/min/m²), PPV, (%), SVV (%), SPV (%), and PVI (%) were registered before and after FC. Data were analysed with ANOVA and ROC tests (p < 0.05). Fluid responsiveness was defined as 15% increase in CI. Eighty dogs completed the study. Fifty (62.5%) were responders and 30 (37.5%) were nonresponders. The PPV, PVI, SPV, and SVV cut-off values (AUC, p) for discriminating responders from nonresponders were PPV >13.8% (0.979, <0.001), PVI >14% (0.956, <0.001), SPV >4.1% (0.793, <0.001), and SVV >14.7% (0.729, <0.001), respectively. Up to 62.5% of normotensive dogs under inhalant anaesthesia may be fluid responders. PPV and PVI have better diagnostic accuracy to predict FR, compared to SPV and SVV.

Non-invasive haemodynamic monitoring with Clearsight in patients undergoing spinal anaesthesia for total hip replacement. A prospective observational cohort study

BACKGROUND

Patients undergoing elective primary total hip replacement and spinal anesthesia may encounter significant hemodynamic instability Objective: The study is aimed at observing the haemodynamic modifications after spinal anaesthesia during total hip replacement in patients managed to "preload independence" with goal directed fluid therapy (GDFT) and monitored non-invasively with Clearsight.

METHODS

Thirty patients, aged 50-80 years, with an American Society of Anaesthesiologists' (ASA) score II-III, undergoing elective primary total hip replacement and spinal anaesthesia were enrolled. Patients were monitored with the EV1000 platform and the Clearsight finger-cuff and managed with a goal directed fluid therapy.

RESULTS

The 79% of the population showed preload independence at baseline. After spinal, the 93% did not show a significant mean arterial pressure reduction. In our population, 79% reported a decrease >10% of the stroke volume during surgery, while 66% in the Recovery Room. Patients showed an improvement in mean arterial pressure, systemic vascular resistances indexed (SVRI), stroke volume (SV) and stroke volume indexed (SVI) at spinal resolution compared to baseline.

CONCLUSIONS

Our cohort population showed hemodynamic stability throughout the study period, with increased SV and decreased SVRI at spinal resolution compared to basal values. Further randomized prospective studies are advocated in the same setting.

[Perioperative fluid management]

An appropriate perioperative infusion management is pivotal for the perioperative outcome of the patient. Optimization of the perioperative fluid treatment often results in enhanced postoperative outcome, reduced perioperative complications and shortened hospitalization. Hypovolemia as well as hypervolemia can lead to an increased rate of perioperative complications. The main goal is to maintain perioperative euvolemia by goal-directed therapy (GDT), a combination of fluid management and inotropic medication, to optimize perfusion conditions in the perioperative period; however, perioperative fluid management should also include the preoperative and postoperative periods. This encompasses the preoperative administration of carbohydrate-rich drinks up to 2 h before surgery. In the postoperative period, patients should be encouraged to start per os hydration early and excessive i.v. fluid administration should be avoided. Implementation of a comprehensive multimodal, goal-directed fluid management within an enhanced recovery after surgery (ERAS) protocol is efficient but the exact status of indovodual items remains unclear at present.

The impact of fluid optimisation before induction of anaesthesia on hypotension after induction

Intra-operative hypotension is a known predictor of adverse events and poor outcomes following major surgery. Hypotension often occurs on induction of anaesthesia, typically attributed to hypovolaemia and the haemodynamic effects of anaesthetic agents. We assessed the efficacy of fluid optimisation for reducing the incidence of hypotension on induction of anaesthesia. This prospective trial enrolled 283 patients undergoing radical cystectomy and randomly allocated them to goal-directed fluid therapy (n = 142) or standard fluid therapy (n = 141). Goal-directed fluid therapy patients received fluid optimisation based on stroke volume response to passive leg raise before induction; those with positive passive leg raise received intravenous crystalloid fluid boluses until stroke volume was optimised. Baseline mean arterial pressure was measured on the morning of surgery and on arriving in the operating theatre. This post-hoc analysis defined haemodynamic instability as either a > 30% relative drop in mean arterial pressure compared with baseline or absolute mean arterial pressure < 55 mmHg, within 15 min of induction. Forty-two (30%) goal-directed fluid therapy patients underwent fluid optimisation after finding an intravascular fluid deficit via passive leg raise testing; 106 (75%) goal-directed fluid therapy and 112 (79%) standard fluid therapy patients met criteria for haemodynamic instability. There was no significant difference in the incidence of haemodynamic instability between the goal-directed fluid therapy and standard fluid therapy groups using absolute mean arterial pressure drop below 55 mmHg (p = 0.58) or using pre-surgical testing or pre-surgical mean arterial pressure values as baseline (p = 0.21, p = 0.89, respectively); however, the difference in the incidence of haemodynamic instability was significant using the operating theatre baseline mean arterial pressure (p = 0.004). We conclude that fluid optimisation before induction of general anaesthesia did not significantly impact haemodynamic instability.

Lack of impact of nil-per-os (NPO) time on goal-directed fluid delivery in first case versus afternoon case starts: a retrospective cohort study

Background

Goal Directed Fluid Therapy (GDFT) represents an objective fluid replacement algorithm. The effect of provider variability remains a confounder. Overhydration worsens perioperative morbidity and mortality; therefore, the impact of the calculated NPO deficit prior to the operating room may reach harm.

Methods

A retrospective single-institution study analyzed patients at UC Irvine Medical Center main operating rooms from September 1, 2013 through September 1, 2015 receiving GDFT. The primary study question asked if GDFT suggested different fluid delivery after different NPO periods, while reducing inter-provider variability. We created two patient groups distinguished by 0715 surgical start time or start time after 1200. We analyzed fluid administration totals with either a 1:1 crystalloid to colloid ratio or a 3:1 ratio. We performed direct group-wise testing on total administered volume expressed as total ml, total ml/hr., and total ml/kg/hr. between the first case start (AM) and afternoon case (PM) groups. A linear regression model included all baseline covariates that differed between groups as well as plausible confounding factors for differing fluid needs. Finally, we combined all patients from both groups, and created NPO time to total administered fluid scatterplots to assess the effect of patient-reported NPO time on fluid administration.

Results

Whether reported by total administered volume or net fluid volume, and whether we expressed the sum as ml, ml/hr., or ml/kg/hr., the AM group received more fluid on average than the PM group in all cases. In the general linear models, for all significant independent variables evaluated, AM vs PM case start did not reach significance in both cases at p = 0.64 and p = 0.19, respectively. In scatterplots of NPO time to fluid volumes, absolute adjusted and unadjusted R2 values are < 0.01 for each plot, indicating virtually non-existent correlations between uncorrected NPO time and fluid volumes measured.

Conclusions

This study showed NPO periods do not influence a patient’s volume status just prior to presentation to the operating room for surgical intervention. We hope this data will influence the practice of providers routinely replacing calculated NPO period volume deficit; particularly with those presenting with later surgical case start times.

Effect of preoperative fluid therapy on hemodynamic stability during anesthesia induction, a randomized study

BACKGROUND

Preserving perfusion pressure during anesthesia induction is crucial. Standardized anesthesia methods, alert fluid therapy and vasoactive drugs may help maintain adequate hemodynamic conditions throughout the induction procedure. In this randomized study, we hypothesized that a pre-operative volume bolus based on lean body weight would decrease the incidence of significant blood pressure drops (BPD) after induction with target-controlled infusion (TCI) or rapid sequence induction (RSI).

METHODS

Eighty individuals scheduled for non-cardiac surgery were randomized to either a pre-operative colloid fluid bolus of 6 ml kg^-1 lean body weight or no bolus, and then anesthetized by means of TCI or RSI. The main outcome measure was blood pressure drops below the mean arterial pressure 65 mm Hg during the first 20 minutes after anesthesia induction. ClinicalTrials.com Identifier: NCT03394833.

RESULTS

Pre-operative fluid therapy decreased the incidence of BPDs fivefold, from 23 of 40 (57.5%) individuals without fluids to 5 of 40 (12.5%) with fluid management, P < .001. The mean BPD was greater in the groups without pre-operative fluids compared to the groups with fluid management; 53 ± 18 mm Hg vs 43 ± 14 mm Hg, P = .007. The overall mean volume of pre-operative fluid bolus infused was 387 ± 52 ml. There was no difference in hemodynamic stability between TCI and RSI. No correlation was shown between incidence of BPDs and increasing age, medication, hypertension, diabetes, renal failure, or low physical capacity.

CONCLUSIONS

Pre-operative fluid bolus decreased the incidence of significant blood pressure drops during TCI and RSI induction of general anesthesia.

The haemodynamic effects of crystalloid and colloid volume resuscitation on primary, derived and efficiency variables in post-CABG patients

Background

Recent studies in haemodynamic management have focused on fluid management and assessed its effects in terms of increase in cardiac output based on fluid challenges or variations in pulse pressure caused by cyclical positive pressure ventilation. The theoretical scope may be characterised as Starling-oriented. This approach ignores the actual events of right-sided excitation and left-sided response which is consistently described in a Guyton-oriented model of the cardiovascular system.

Aim

Based on data from a previous study, we aim to elucidate the primary response to crystalloid and colloid fluids in terms of cardiac output, mean blood pressure and right atrial pressure as well as derived and efficiency variables defined in terms of Guyton venous return physiology.

Method

Re-analyses of previously published data.

Results

Cardiac output invariably increased on infusion of crystalloid and colloid solutions, whereas static and dynamic efficiency measures declined in spite of increasing pressure gradient for venous return.

Discussion

We argue that primary as well as derived and efficiency measures should be reported and discussed when haemodynamic studies are reported involving fluid administrations.

Pre-operative fluid bolus for improved haemodynamic stability during minor surgery: A prospectively randomized clinical trial

BACKGROUND

Haemodynamic instability during the induction of anaesthesia and surgery is common and may be related to hypovolaemia caused by pre-operative fasting or chronic diuretic therapy. The aim of our prospective, controlled, randomized study was to test the hypothesis that a predefined fluid bolus given prior to general anaesthesia for minor surgery would increase haemodynamic stability during anaesthetic induction.

METHODS

Two hundred and nineteen fairly healthy adult patients requiring minor surgery were enrolled. All received standard treatment, including a pulse contour analysing device for non-invasive measurement of cardiac index. Infusion therapy was started in all patients at induction. The intervention group (106 patients) was randomized to receive an additional fluid bolus of 8 mL/kg Ringer's acetate solution before the induction of anaesthesia. The primary endpoint was the incidence of haemodynamic instability, defined as a significant reduction of blood pressure or cardiac index during induction of anaesthesia.

RESULTS

The interventional group had a lesser incidence of haemodynamic instability during induction (41.5% vs 56.6%, P = .025). This group also had higher cardiac index, stroke volume index, systolic and mean blood pressure and a greater left ventricular end-diastolic area.

CONCLUSIONS

A fluid bolus prior to anaesthesia reduced the incidence of haemodynamic instability during induction of general anaesthesia. The total fluid volume was slightly greater in the intervention group compared to the control group (1370 ± 439 mL vs 1219 ± 483 mL, P = .007). We conclude that a defined fluid bolus can help stabilizing haemodynamics in patients undergoing general anaesthesia.

Preoperative and Postoperative Assessment of Ultrasonographic Measurement of Inferior Vena Cava: A Prospective, Observational Study

Background: Ultrasound measurement of dynamic changes in inferior vena cava (IVC) diameter and collapsibility index (CI) are used to estimate the fluid responsiveness and intravascular volume status. We conducted an analysis to quantify the sonographic measurement of IVC diameter changes in adult patients at the preoperative and postoperative periods. Methods: Ultrasonography was performed on 72 patients scheduled for surgery with American Society of Anesthesiologists physical status I to III. Quantitative assessments of the end-expiration (D_min), end-inspiration (D_max), and CI at preoperative and postoperative period were compared in a prospective, observational study. The patients received intravenous fluid according to standard protocol regimes peroperatively. Results: Ultrasonography of IVC measurement was unsuccessful in 12.5% of patients and 63 patients remained for analyses. The mean age was 43.29 ± 17.22 (range 18–86) years. The average diameter of the D_min, D_max, and dIVC preoperative and postoperative were 1.99 ± 0.31 vs. 2.05 ± 0.29 cm, 1.72 ± 0.33 vs. 1.74 ± 0.32 cm, 14.0 ± 9.60% vs. 15.14 ± 11.18%, respectively (p > 0.05). CI was positively associated preoperatively and postoperatively (regression coefficient = 0.438, p < 0.01). Conclusion: The diameter of the IVC did not change preoperatively and postoperatively in adult patients with standard fluid regimens. The parameters of the IVC diameter increased postoperatively according to the preoperative period.

Anesthesia-Associated Relative Hypovolemia: Mechanisms, Monitoring, and Treatment Considerations

Although the utility and benefits of anesthesia and analgesia are irrefutable, their practice is not void of risks. Almost all drugs that produce anesthesia endanger cardiovascular stability by producing dose-dependent impairment of cardiac function, vascular reactivity, and compensatory autoregulatory responses. Whereas anesthesia-related depression of cardiac performance and arterial vasodilation are well recognized adverse effects contributing to anesthetic risk, far less emphasis has been placed on effects impacting venous physiology and venous return. The venous circulation, containing about 65–70% of the total blood volume, is a pivotal contributor to stroke volume and cardiac output. Vasodilation, particularly venodilation, is the primary cause of relative hypovolemia produced by anesthetic drugs and is often associated with increased venous compliance, decreased venous return, and reduced response to vasoactive substances. Depending on factors such as patient status and monitoring, a state of relative hypovolemia may remain clinically undetected, with impending consequences owing to impaired oxygen delivery and tissue perfusion. Concurrent processes related to comorbidities, hypothermia, inflammation, trauma, sepsis, or other causes of hemodynamic or metabolic compromise, may further exacerbate the condition. Despite scientific and technological advances, clinical monitoring and treatment of relative hypovolemia still pose relevant challenges to the anesthesiologist. This short perspective seeks to define relative hypovolemia, describe the venous system’s role in supporting normal cardiovascular function, characterize effects of anesthetic drugs on venous physiology, and address current considerations and challenges for monitoring and treatment of relative hypovolemia, with focus on insights for future therapies.

Doppler-guided goal-directed fluid therapy does not affect intestinal cell damage but increases global gastrointestinal perfusion in colorectal surgery: a randomized controlled trial

AIM

Individualized, goal-directed fluid therapy (GDFT), based on Doppler measurements of stroke volume, has been proposed as a treatment strategy in terms of reducing complications, mortality and length of hospital stay in major bowel surgery. We studied the effect of Doppler-guided GDFT on intestinal damage as compared with standard postoperative fluid replacement.

METHOD

Patients undergoing elective colorectal resection for malignancy were randomized either to standard intra- and postoperative fluid therapy or to standard fluid therapy with additional Doppler-guided GDFT. The primary outcome was intestinal epithelial cell damage measured by plasma levels of intestinal fatty acid-binding protein (I-FABP). Global gastrointestinal perfusion was measured by gastric tonometry, expressed as regional (gastric) minus arterial CO₂ -gap (P_r-a CO₂ -gap).

RESULTS

I-FABP levels were not significantly different between the intervention group and the control group (respectively, 440.8 (251.6) pg/ml and 522.4 (759.9) pg/ml, P = 0.67). Mean areas under the curve (AUCs) of intra-operative P_r-a CO₂ -gaps were significantly lower in the intervention group than in the control group (P = 0.01), indicating better global gastrointestinal perfusion in the intervention group. Moreover, the mean intra-operative P_r-a CO₂ -gap peak in the intervention group was 0.5 (1.0) kPa, which was significantly lower than the mean peak in the control group, of 1.4 (1.4) kPa (P = 0.03).

CONCLUSION

Doppler-guided GDFT during and in the first hours after elective colorectal surgery for malignancy increases global gastrointestinal perfusion, as measured by P_r-a CO₂ -gap.

A pragmatic multi-center trial of goal-directed fluid management based on pulse pressure variation monitoring during high-risk surgery

Background

Intraoperative fluid therapy guided by mechanical ventilation-induced pulse-pressure variation (PPV) may improve outcomes after major surgery. We tested this hypothesis in a multi-center study.

Methods

The patients were included in two periods: a first control period (control group; n = 147) in which intraoperative fluids were given according to clinical judgment. After a training period, intraoperative fluid management was titrated to maintain PPV < 10% in 109 surgical patients (PPV group). We performed 1:1 propensity score matching to ensure the groups were comparable with regard to age, weight, duration of surgery, and type of operation. The primary endpoint was postoperative hospital length of stay.

Results

After matching, 84 patients remained in each group. Baseline characteristics, surgical procedure duration and physiological parameters evaluated at the start of surgery were similar between the groups. The volume of crystalloids (4500 mL [3200-6500 mL] versus 5000 mL [3750-8862 mL]; P = 0.01), the number of blood units infused during the surgery (1.7 U [0.9-2.0 U] versus 2.0 U [1.7-2.6 U]; P = 0.01), the fraction of patients transfused (13.1% versus 32.1%; P = 0.003) and the number of patients receiving mechanical ventilation at 24 h (3.2% versus 9.7%; P = 0.027) were smaller postoperatively in PPV group. Intraoperative PPV-based improved the composite outcome of postoperative complications OR 0.59 [95% CI 0.35-0.99] and reduced the postoperative hospital length of stay (8 days [6-14 days] versus 11 days [7-18 days]; P = 0.01).

Conclusions

In high-risk surgeries, PPV-directed volume loading improved postoperative outcomes and decreased the postoperative hospital length of stay.

Trial Registration

ClinicalTrials.gov Identifier; retrospectively registered- NCT03128190

A mesenteric traction syndrome affects near-infrared spectroscopy evaluated cerebral oxygenation because skin blood flow increases

During abdominal surgery manipulation of internal organs may induce a "mesenteric traction syndrome" (MTS) including a triad of flushing, hypotension, and tachycardia that lasts for about 30 min. We evaluated whether MTS affects near-infrared spectroscopy (NIRS) assessed frontal lobe oxygenation (S_cO₂) by an increase in forehead skin blood flow (SkBF). The study intended to include 10 patients who developed MTS during pancreaticoduodenectomy and 22 patients were enrolled (age 61 ± 8 years; mean ± SD). NIRS determined ScO₂, laser Doppler flowmetry determined SkBF, cardiac output (CO) was evaluated by pulse-contour analysis (Modelflow), and transcranial Doppler assessed middle cerebral artery mean flow velocity (MCA V_mean). MTS was identified by flushing within 60 min after start of surgery. MTS developed 20 min (12-24; median with range) after the start of surgery and heart rate (78 ± 16 vs. 68 ± 17 bpm; P = 0.0032), CO (6.2 ± 1.4 vs. 5.3 ± 1.1 L min^-1; P = 0.0086), SkBF (98 ± 35 vs. 80 ± 23 PU; P = 0.0271), and S_cO₂ (71 ± 6 vs. 67 ± 8%; P < 0.0001), but not MCA V_mean (32 ± 8 vs. 32 ± 7; P = 0.1881) were largest in the patients who developed MTS. In some patients undergoing abdominal surgery NIRS-determined S_cO₂ is at least temporarily affected by an increase in extra-cranial perfusion independent of cerebral blood flow as indicated by MCA V_mean. Thus, NIRS evaluation of S_cO₂ may overestimate cerebral oxygenation if patients flush during surgery.

Plasma pro-atrial natriuretic peptide to estimate fluid balance during open and robot-assisted esophagectomy: a prospective observational study

Background

It remains debated how much fluid should be administered during surgery. The atrial natriuretic peptide precursor proANP is released by atrial distension and deviations in plasma proANP are reported associated with perioperative fluid balance. We hypothesized that plasma proANP would decrease when the central blood volume is compromised during the abdominal part of robot-assisted hybrid (RE) esophagectomy and that a positive fluid balance would be required to maintain plasma proANP.

Methods

Patients undergoing RE (n = 25) or open (OE; n = 25) esophagectomy for gastroesophageal cancer were included consecutively in this prospective observational study. Plasma proANP was determined repetitively during esophagectomy to allow for distinction between the abdominal and thoracic part of the procedure. The RE group was 15° head up tilted during the abdominal procedure.

Results

The blood loss was 250 (150–375) (RE) and 600 ml (390–855) (OE) (p = 0.01), but the two groups of patients were provided with a similar positive fluid balance: 1705 (1390–1983) vs. 1528 ml (1316–1834) (p = 0.4). However, plasma proANP decreased by 21% (p < 0.01) during the abdominal part of RE carried out during moderate head-up tilt, but only by 11% (p = 0.01) during OE where the patients were supine. Plasma proANP and fluid balance were correlated in the RE-group (r = 0.5 (0.073–0.840), p = 0.02) and tended to correlate in the OE group (r = 0.4 (−0.045–0.833), p = 0.08).

Conclusion

The results support that plasma proANP decreases when the central blood volume is compromised and suggest that an about 2200 ml surplus administration of crystalloid is required to maintain plasma proANP during esophagectomy.

Trial registration

Clinicaltrials.gov (NCT02077673). Registered retrospectively February 12^th 2014.

Efficacy of different fluids preload on propofol injection pain: A randomized, controlled, double-blinded study

Injection pain of propofol remains a common clinical problem. Previous studies demonstrated that propofol injection pain was alleviated by applying nitroglycerin ointment to the skin of injection site, which inspires us to test whether venous vasodilation induced by fluid preload could alleviate the pain. Different types or volumes of fluid preload were compared. 200 ASA I-II adult patients were randomly assigned to five groups of 40 each. A 20 G cannula was established on the dorsum or wrist of the hand. When fluid preload given with Plasma-Lyte A 100 mL (P100 group), 250 mL (P250 group), 500 mL (P500 group), 0.9% saline 500 mL (N500 group) or Gelofusine 500 mL (G500 group) was completed within 30 min, respectively, Propofol (0.5 mg/kg, 1%) was injected at a rate of 0.5 mL/s. A blind investigator assessed the pain using a four-point scale. Incidence of pain in P100, P250, and P500 groups was 87.5%, 57.5% and 35%, respectively (P<0.05). The median pain intensity score was significantly lower in P500 group than that in P250 and P100 groups (P<0.05 and P<0.01, respectively). Comparison of the effect of different types of solution preload indicated that the highest incidence of pain was in N500 group (62.5%) (N500 vs. P500, P=0.014; N500 vs. G500, P=0.007). The median pain intensity score in N500 group was higher than that in P500 group (P<0.05) and G500 group (P<0.05). There was no significant difference between P500 and G500 groups. It is suggested that Plasma-Lyte A or Gelofusine preload with 500 mL before propofol injection is effective in alleviating propofol-induced pain.

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.

Impact of Albumin on Coagulation Competence and Hemorrhage During Major Surgery: A Randomized Controlled Trial

For patients exposed to a massive blood loss during surgery, maintained coagulation competence is important. It is less obvious whether coagulation competence influences bleeding during elective surgery where patients are exposed to infusion of a crystalloid or a colloid. This randomized controlled trial evaluates whether administration of 5% human albumin (HA) or lactated Ringer solution (LR) affects coagulation competence and in turn blood loss during cystectomy due to bladder cancer. Forty patients undergoing radical cystectomy were included to receive either 5% HA (n = 20) or LR (n = 20). Nineteen patients were analyzed in the HA group and 20 patients in the lactated Ringer group. Blinded determination of the blood loss was similar in the 2 groups of patients: 1658 (800-3300) mL with the use of HA and 1472 (700-4330) mL in the lactated Ringer group (P = 0.45). Yet, by thrombelastography (TEG) evaluated coagulation competence, albumin affected clot growth (TEG-angle 69 ± 5 vs 74° ± 3°, P < 0.01) and strength (TEG-MA: 59 ± 6 vs 67 ± 6 mm, P < 0.001) more than LR. Furthermore, by multivariate linear regression analyses reduced TEG-MA was independently associated with the blood loss (P = 0.042) while administration of albumin was related to the changes in TEG-MA (P = 0.029), aPPT (P < 0.022), and INR (P < 0.033). This randomized controlled trial demonstrates that administration of HA does not affect the blood loss as compared to infusion of LR. Also the use of HA did not affect the need for blood transfusion, the incidence of postoperative complications, or the hospital in-stay. Yet, albumin decreases coagulation competence during major surgery and the blood loss is related to TEG-MA rather than to plasma coagulation variables.

Plasma pro-atrial natriuretic peptide to indicate fluid balance during cystectomy: a prospective observational study

OBJECTIVES

During surgery the volume of administered fluid is debated. Pro-atrial natriuretic peptide (proANP) is released by atrial distension, and we evaluated the relationship between changes in proANP associated with perioperative fluid balance.

DESIGN

Prospective observational study.

SETTING

One university/tertiary centre.

PARTICIPANTS

The study included patients who underwent radical cystectomy. Plasma for determination of proANP was obtained before surgery, after resection of the bladder, and at the end of surgery for 20 robotic-assisted radical cystectomy (RARC) and 20 open radical cystectomy (ORC) procedures.

RESULTS

The blood loss was 1871 (95% CI 1267 to 2475) vs 589 mL (378 to 801) in the ORC and RARC groups (p=0.001), respectively, and fluid balance was positive by 1518 mL (1215 to 1821) during ORC, and by 1858 mL (1461 to 2255) during RARC (p=0.163). Yet, at the end of ORC, plasma proANP was reduced by 23% (14% to 32%, p=0.001), while plasma proANP did not change significantly during RARC. Thus, plasma proANP was associated both with the perioperative blood loss (r= -0.475 (0.632 to -0.101), p=0.002), and with fluid balance (r=0.561 (0.302 to 0.740), p=0.001), indicating that a stable plasma proANP required a fluid surplus by 2.4 L (2.0 to 2.7).

CONCLUSIONS

There was a correlation between intraoperative haemorrhage and a decrease in plasma proANP and, taking plasma proANP to indicate filling of the heart, about 2.5 L surplus volume of lactated Ringer's solution appears to maintain cardiac preload during cystectomy.

TRIAL REGISTRATION NUMBER

EudraCT (2012-005040-20), Results.

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.

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.

Choices in fluid type and volume during resuscitation: impact on patient outcomes

We summarize the emerging new literature regarding the pathophysiological principles underlying the beneficial and deleterious effects of fluid administration during resuscitation, as well as current recommendations and recent clinical evidence regarding specific colloids and crystalloids. This systematic review allows us to conclude that there is no clear benefit associated with the use of colloids compared to crystalloids and no evidence to support the unique benefit of albumin as a resuscitation fluid. Hydroxyethyl starch use has been associated with increased acute kidney injury (AKI) and use of renal replacement therapy. Other synthetic colloids (dextran and gelatins) though not well studied do not appear superior to crystalloids. Normal saline (NS) use is associated with hyperchloremic metabolic acidosis and increased risk of AKI. This risk is decreased when balanced salt solutions are used. Balanced crystalloid solutions have shown no harmful effects, and there is evidence for benefit over NS. Finally, fluid resuscitation should be applied in a goal-directed manner and targeted to physiologic needs of individual patients. The evidence supports use of fluids in volume-responsive patients whose end-organ perfusion parameters have not been met.

Preoperative fasting does not affect haemodynamic status: a prospective, non-inferiority, echocardiography study

BACKGROUND

The link between preoperative fasting and hypovolaemia remains unclear. We tested the hypothesis that preoperative fasting does not significantly increase the proportion of patients with hypovolaemia according to transthoracic echocardiography (TTE) criteria.

METHODS

Patients of ASA status I-III and without bowel preparation were included in a non-inferiority, prospective, single-centre trial. Patients underwent passive leg raising (PLR) test and TTE at admission (Day 0) and after 8 h fasting (Day 1). The primary hypothesis was that an 8 h preoperative fasting does not increase the proportion (margin=5%) of patients with a positive PLR test ('functional approach'). The secondary hypothesis was that echocardiographic filling pressures or stroke volume (margin 10%) are not affected by preoperative fasting ('static approach').

RESULTS

One hundred patients were included and 98 analysed. After an 8 h fasting, the change in the proportion of responders to PLR was -6.1% [95% confidence interval (CI)=-16.0 to 3.8] of responders to PLR test on Day 0 when compared with Day 1. Because 95% CI was strictly inferior to 5%, there was no significant increase in the proportion of PLR responders on Day 1 when compared with Day 0. The 95% CI changes of static variables were always fewer than 10%, meaning that preoperative fasting induced significantly no relevant changes in static variables.

CONCLUSION

Preoperative fasting did not alter TTE dynamic and static preload indices in ASA I-III adult patients. These results suggest that preoperative fasting does not induce significant hypovolaemia. Clinical trial registration NCT 01258361.

Dehydration, hemodynamics and fluid volume optimization after induction of general anesthesia

OBJECTIVES

Fluid volume optimization guided by stroke volume measurements reduces complications of colorectal and high-risk surgeries. We studied whether dehydration or a strong hemodynamic response to general anesthesia increases the probability of fluid responsiveness before surgery begins.

METHODS

Cardiac output, stroke volume, central venous pressure and arterial pressures were measured in 111 patients before general anesthesia (baseline), after induction and stepwise after three bolus infusions of 3 ml/kg of 6% hydroxyethyl starch 130/0.4 (n=86) or Ringer's lactate (n=25). A subgroup of 30 patients who received starch were preloaded with 500 ml of Ringer's lactate. Blood volume changes were estimated from the hemoglobin concentration and dehydration was estimated from evidence of renal water conservation in urine samples.

RESULTS

Induction of anesthesia decreased the stroke volume to 62% of baseline (mean); administration of fluids restored this value to 84% (starch) and 68% (Ringer's). The optimized stroke volume index was clustered around 35-40 ml/m2/beat. Additional fluid boluses increased the stroke volume by ≥10% (a sign of fluid responsiveness) in patients with dehydration, as suggested by a low cardiac index and central venous pressure at baseline and by high urinary osmolality, creatinine concentration and specific gravity. Preloading and the hemodynamic response to induction did not correlate with fluid responsiveness. The blood volume expanded 2.3 (starch) and 1.8 (Ringer's) times over the infused volume.

CONCLUSIONS

Fluid volume optimization did not induce a hyperkinetic state but ameliorated the decrease in stroke volume caused by anesthesia. Dehydration, but not the hemodynamic response to the induction, was correlated with fluid responsiveness.

Pavane for a pulse pressure variation defunct

Hemodynamic management of critically ill patients in the ICU or high-risk patients in the operating room has paradoxically shown progress in terms of outcome after the systematic application of volume responsiveness/flow optimization based on pulse pressure variation and/or stroke volume variation during controlled, positive-pressure ventilation in patients without spontaneous respiratory efforts. This assessment of circulatory optimization should ideally be based on an exhaustive, predictive and coherent physiological understanding of the cardiovascular system model. This paper sketches the extremely complex physiological background of the concept of volume responsiveness, concluding that it is not a reliable means of guiding hemodynamic optimization because it is based on a nonexhaustive, nonpredictive and incoherent physiological model.

Does Goal-directed Fluid Therapy Affect Postoperative Orthostatic Intolerance?

Background:

Early mobilization is important for postoperative recovery but is limited by orthostatic intolerance (OI) with a prevalence of 50% 6 h after major surgery. The pathophysiology of postoperative OI is assumed to include hypovolemia besides dysregulation of vasomotor tone. Stroke volume–guided fluid therapy, so-called goal-directed therapy (GDT), corrects functional hypovolemia, and the authors hypothesized that GDT reduces the prevalence of OI after major surgery and assessed this in a prospective, double-blinded trial.

Methods:

Forty-two patients scheduled for open radical prostatectomy were randomized into standard fluid therapy (control group) or GDT groups. Both groups received a fixed-volume crystalloid regimen supplemented with 1:1 replacement of blood loss with colloid, and in addition, the GDT group received colloid to obtain a maximal stroke volume (esophageal Doppler). The primary outcome was the prevalence of OI assessed with a standardized mobilization protocol before and 6 h after surgery. Hemodynamic and hormonal orthostatic responses were evaluated.

Results:

Twelve (57%) versus 15 (71%) patients in the control and GDT groups (P = 0.33), respectively, demonstrated OI after surgery, group difference 14% (CI, −18 to 45%). Patients in the GDT group received more colloid during surgery (1,758 vs. 1,057 ml; P = 0.001) and reached a higher stroke volume (102 vs. 89 ml; P = 0.04). OI patients had an increased length of hospital stay (3 vs. 2 days; P = 0.02) and impaired hemodynamic and norepinephrine responses on mobilization.

Conclusion:

GDT did not reduce the prevalence of OI, and patients with OI demonstrated impaired cardiovascular and hormonal responses to mobilization.

Stroke volume optimization in elective bowel surgery: a comparison between pulse power wave analysis (LiDCOrapid) and oesophageal Doppler (CardioQ)

BACKGROUND

Goal-directed fluid therapy improves outcome in major surgery. We evaluated a new device (LiDCOrapid) against our standard oesophageal Doppler method (ODM) for stroke volume (SV) optimization during colorectal surgery.

METHODS

This was an observational study in 20 patients undergoing major colorectal surgery within a fast-track protocol. We compared SV values measured simultaneously by LiDCOrapid and ODM before and after 86 fluid challenges. We also evaluated the LiDCOrapid dynamic indices SV variation (SVV) and pulse pressure variation (PPV) as predictors for volume responsiveness, defined as an increase in SV ≥ 10% after 200 ml of colloid.

RESULTS

SV increased ≥ 10% after 27 out of 86 fluid challenges. For 172 paired SV values, the overall correlation was r=0.39, and bias (limits of agreement) -28 (-91-35) ml, percentage error 70%. The ability of LiDCOrapid to track changes in SV was weak with a concordance rate of 80%, and a sensitivity and specificity of 48% and 81%, respectively, to detect a positive fluid challenge. The area under the curve values (with 95% confidence intervals) for SVV and PPV were 0.72 (0.60-0.83) and 0.66 (0.52-0.79), respectively, indicating low predictive capacity in these setting.

CONCLUSIONS

LiDCOrapid and ODM devices are not interchangeable. We cannot recommend that the LiDCOrapid replace the standard Doppler method until further device-specific outcome studies on volume optimization are available. The dynamic indices SVV and PPV add little value to a fluid optimization protocol, and should not replace SV measurements with a validated technique.

[Do anesthetic techniques influence postoperative outcomes? Part II]

The knowledge of the influence of anesthetic techniques in postoperative outcomes has opened a large field of research in recent years. In this second part, we review some of the major controversies arising from the literature on the impact of anesthetic techniques on postoperative outcomes in 6 areas: postoperative cognitive dysfunction, chronic postoperative pain, cancer recurrence, postoperative nausea/vomiting, surgical outcomes, and resources utilization. The development of protective and preventive anesthetic strategies against short and long-term postoperative complications will probably occupy an important role in our daily anesthetic practice. Dynamic postoperative pain control has been confirmed as one of the basic requirements of accelerated postoperative recovery programs ("fast-track surgery"), and it is also a preventive factor for development of chronic postoperative pain. The weight of anesthetic technique on postoperative immunosuppression is to be defined. The potential influence of anesthesia on cancer recurrence, is a highly controversial area of research. The classic pattern of perioperative fluid therapy may increase postoperative complications. On the other hand, the maintenance of normoglycemia and normothermia was associated with a decreased postoperative morbidity. The high volume of surgical procedures means that the adequacy of human, organizational and technological resources have a major impact on overall costs.

Detection of dehydration by using volume kinetics

BACKGROUND

Patients admitted to surgery may be dehydrated, which is difficult to diagnose except when it is severe (>5% Gl116 of the body weight). We hypothesized that modest dehydration can be detected by kinetic analysis of the blood hemoglobin concentration after a bolus infusion of crystalloid fluid.

METHODS

Four series of experiments were performed on 10 conscious, healthy male volunteers. Separated by at least 2 days, they received 5 or 10 mL/kg acetated Ringer's solution over 15 minutes. Before starting half of the IV infusions, volume depletion amounting to 1.5 to 2.0 L (approximately 2% of body weight) was induced with furosemide. The elimination clearance and the half-life of the infused fluid were calculated based on blood hemoglobin over 120 minutes. The perfusion index and the pleth variability index were monitored by pulse oximetry after a change of body position.

RESULTS

Dehydration decreased the elimination clearance of acetated Ringer's solution [median (25th-75th percentile)] from 1.84 (1.23-2.57) to 0.53 (0.41-0.79) mL/kg/min (Wilcoxon matched-pair test P < 0.001) and increased the half-life from 23 (12-37) to 76 (57-101) minutes (P < 0.001). The smaller infusion, 5 mL/kg, fully discriminated between experiments performed in the euhydrated and dehydrated states, whereas the urinary excretion provided a less-reliable indication of hydration status. Dehydration decreased the perfusion index but did not affect the pleth variability index.

CONCLUSION

Dehydration amounting to 2% of the body weight could be detected from the elimination clearance and the half-life of an infusion of 5 mL/kg Ringer's solution.

The intravascular volume effect of Ringer's lactate is below 20%: a prospective study in humans

Introduction

Isotonic crystalloids play a central role in perioperative fluid management. Isooncotic preparations of colloids (for example, human albumin or hydroxyethyl starch) remain nearly completely intravascular when infused to compensate for acute blood losses. Recent data were interpreted to indicate a comparable intravascular volume effect for crystalloids, challenging the occasionally suggested advantage of using colloids to treat hypovolemia. General physiological knowledge and clinical experience, however, suggest otherwise.

Methods

In a prospective study, double-tracer blood volume measurements were performed before and after intended normovolemic hemodilution in ten female adults, simultaneously substituting the three-fold amount of withdrawn blood with Ringer's lactate. Any originated deficits were substituted with half the volume of 20% human albumin, followed by a further assessment of blood volume. To assess significance between the measurements, repeated measures analysis of variance (ANOVA) according to Fisher were performed. If significant results were shown, paired t tests (according to Student) for the singular measurements were taken. P < 0.05 was considered to be significant.

Results

A total of 1,097 ± 285 ml of whole blood were withdrawn (641 ± 155 ml/m² body surface area) and simultaneously replaced by 3,430 ± 806 ml of Ringer's lactate. All patients showed a significant decrease in blood volume after hemodilution (-459 ± 185 ml; P < 0.05) that did not involve relevant hemodynamical changes, and a significant increase in interstitial water content (+2,157 ± 606 ml; P < 0.05). The volume effect of Ringer's lactate was 17 ± 10%. The infusion of 245 ± 64 ml of 20% human albumin in this situation restored blood volume back to baseline values, the volume effect being 184 ± 63%.

Conclusions

Substitution of isolated intravascular deficits in cardiopulmonary healthy adults with the three-fold amount of Ringer's lactate impedes maintenance of intravascular normovolemia. The main side effect was an impressive interstitial fluid accumulation, which was partly restored by the intravenous infusion of 20% human albumin. We recommend to substitute the five-fold amount of crystalloids or to use an isooncotic preparation in the face of acute bleeding in patients where edema prevention might be advantageous.