Passive Leg-Raising and Prediction of Fluid Responsiveness: Systematic Review

Performance of four cardiac output monitoring techniques vs. intermittent pulmonary artery thermodilution during a modified passive leg raise maneuver in isoflurane-anesthetized dogs

Objective

This study investigated the performance among four cardiac output (CO) monitoring techniques in comparison with the reference method intermittent pulmonary artery thermodilution (iPATD) and their ability to diagnose fluid responsiveness (FR) during a modified passive leg raise (PLRM) maneuver in isoflurane-anesthetized dogs undergoing acute blood volume manipulations. The study also examined the simultaneous effect of performing the PLRM on dynamic variables such as stroke distance variation (SDV), peak velocity variation (PVV), and stroke volume variation (SVV).

Study design

Prospective, nonrandomized, crossover design.

Study animals

Six healthy male Beagle dogs.

Methods

The dogs were anesthetized with propofol and isoflurane and mechanically ventilated under neuromuscular blockade. After instrumentation, they underwent a series of sequential, nonrandomized steps: Step 1: baseline data collection; Step 2: removal of 33 mL kg-1 of circulating blood volume; Step 3: blood re-transfusion; and Step 4: infusion of 20 mL kg-1 colloid solution. Following a 10-min stabilization period after each step, CO measurements were recorded using esophageal Doppler (EDCO), transesophageal echocardiography (TEECO), arterial pressure waveform analysis (APWACO), and electrical cardiometry (ECCO). Additionally, SDV, PVV, and SVV were recorded. Intermittent pulmonary artery thermodilution (iPATDCO) measurements were also recorded before, during, and after the PLRM maneuver. A successful FR diagnosis made using a specific test indicated that CO increased by more than 15% during the PLRM maneuver. Statistical analysis was performed using one-way analysis of variance for repeated measures with post hoc Tukey test, linear regression, Lin's concordance correlation coefficient (ρc), and Bland-Altman analysis. Statistical significance was set at p < 0.05.

Results

All techniques detected a reduction in CO (p < 0.001) during hemorrhage and an increase in CO after blood re-transfusion and colloid infusion (p < 0.001) compared with baseline. During hemorrhage, CO increases with the PLRM maneuver were as follows: 33% for iPATD (p < 0.001), 19% for EC (p = 0.03), 7% for APWA (p = 0.97), 39% for TEE (p < 0.001), and 17% for ED (p = 0.02). Concurrently, decreases in SVV, SDV, and PVV values (p < 0.001) were also observed. The percentage error for TEE, ED, and EC was less than 30% but exceeded 55% for APWA. While TEECO and ECCO slightly underestimated iPATDCO values, EDCO and APWACO significantly overestimated iPATDCO values. TEE and EC exhibited good and acceptable agreement with iPATD. However, CO measurements using all four techniques and iPATD did not differ before, during, and after PLRM at baseline, blood re-transfusion, and colloid infusion.

Conclusion and clinical relevance

iPATD, EC, TEE, and ED effectively assessed FR in hypovolemic dogs during the PLRM maneuver, while the performance of APWA was unacceptable and not recommended. SVV, SDV, and PVV could be used to monitor CO changes during PLRM and acute blood volume manipulations, suggesting their potential clinical utility.

Volumetric evaluation of fluid responsiveness using a modified passive leg raise maneuver during experimental induction and correction of hypovolemia in anesthetized dogs

OBJECTIVE

To demonstrate if modified passive leg raise (PLR_M) maneuver can be used for volumetric evaluation of fluid responsiveness (FR) by inducing cardiac output (CO) changes during experimental induction and correction of hypovolemia in healthy anesthetized dogs. The effects of PLR_M on plethysmographic variability index (PVI) and pulse pressure variation (PPV) were also investigated.

STUDY DESIGN

Prospective, crossover study.

ANIMALS

A total of six healthy anesthetized Beagle dogs.

METHODS

Dogs were anesthetized with propofol and isoflurane. They were mechanically ventilated under neuromuscular blockade, and normothermia was maintained. After instrumentation, all dogs were subjected to four stages: 1, baseline; 2, removal of 27 mL kg^-1 circulating blood volume; 3, after blood re-transfusion; and 4, after 20 mL kg^-1 hetastarch infusion over 20 minutes. A 10 minute stabilization period was allowed after induction of each stage and before data collection. At each stage, CO via pulmonary artery thermodilution, PVI, PPV and cardiopulmonary variables were measured before, during and after the PLR_M maneuver. Stages were sequential, not randomized. Statistical analysis included repeated measures anova and Tukey's post hoc test, considering p < 0.05 as significant.

RESULTS

During stage 2, PLR_M at a 30° angle significantly increased CO (mean ± standard deviation, 1.0 ± 0.1 to 1.3 ± 0.1 L minute^-1; p < 0.001), with a simultaneous significant reduction in PVI (38 ± 4% to 21 ± 4%; p < 0.001) and PPV (27 ± 2% to 18 ± 2%; p < 0.001). The PLR_M did not affect CO, PPV and PVI during stages 1, 3 and 4.

CONCLUSIONS AND CLINICAL RELEVANCE

In anesthetized dogs, PLR_M at a 30° angle successfully detected FR during hypovolemia, and identified fluid nonresponsiveness during normovolemia and hypervolemia. Also, in hypovolemic dogs, significant decreases in PVI and PPV occurred in response to PLR_M maneuver.

Prediction of fluid responsiveness. What’s new?

Although the administration of fluid is the first treatment considered in almost all cases of circulatory failure, this therapeutic option poses two essential problems: the increase in cardiac output induced by a bolus of fluid is inconstant, and the deleterious effects of fluid overload are now clearly demonstrated. This is why many tests and indices have been developed to detect preload dependence and predict fluid responsiveness. In this review, we take stock of the data published in the field over the past three years. Regarding the passive leg raising test, we detail the different stroke volume surrogates that have recently been described to measure its effects using minimally invasive and easily accessible methods. We review the limits of the test, especially in patients with intra-abdominal hypertension. Regarding the end-expiratory occlusion test, we also present recent investigations that have sought to measure its effects without an invasive measurement of cardiac output. Although the limits of interpretation of the respiratory variation of pulse pressure and of the diameter of the vena cava during mechanical ventilation are now well known, several recent studies have shown how changes in pulse pressure variation itself during other tests reflect simultaneous changes in cardiac output, allowing these tests to be carried out without its direct measurement. This is particularly the case during the tidal volume challenge, a relatively recent test whose reliability is increasingly well established. The mini-fluid challenge has the advantage of being easy to perform, but it requires direct measurement of cardiac output, like the classic fluid challenge. Initially described with echocardiography, recent studies have investigated other means of judging its effects. We highlight the problem of their precision, which is necessary to evidence small changes in cardiac output. Finally, we point out other tests that have appeared more recently, such as the Trendelenburg manoeuvre, a potentially interesting alternative for patients in the prone position.

Assessment of Volume Status and Fluid Responsiveness in Small Animals

Intravenous fluids are an essential component of shock management in human and veterinary emergency and critical care to increase cardiac output and improve tissue perfusion. Unfortunately, there are very few evidence-based guidelines to help direct fluid therapy in the clinical setting. Giving insufficient fluids and/or administering fluids too slowly to hypotensive patients with hypovolemia can contribute to continued hypoperfusion and increased morbidity and mortality. Similarly, giving excessive fluids to a volume unresponsive patient can contribute to volume overload and can equally increase morbidity and mortality. Therefore, assessing a patient's volume status and fluid responsiveness, and monitoring patient's response to fluid administration is critical in maintaining the balance between meeting a patient's fluid needs vs. contributing to complications of volume overload. This article will focus on the physiology behind fluid responsiveness and the methodologies used to estimate volume status and fluid responsiveness in the clinical setting.

The clinical value of passive leg raising plus ultrasound to predict fluid responsiveness in children after cardiac surgery

Background

There are few non-invasive monitoring methods that can reliably predict fluid responsiveness (FR) in children. Here, we interrogate the value of doppler ultrasound evaluation of passive leg raising (PLR)-induced changes in stroke volume (SV) and cardiac output (CO) as a predictor of FR in children with mechanical ventilation after congenital cardiac surgery.

Methods

A total of 40 children with mechanical ventilation following congenital cardiac surgery, who required volume expansion (VE) were included in this study. Hemodynamic parameters such as heart rate (HR), mean arterial pressure (MAP), SV, and central venous pressure (CVP) were monitored before and after PLR and VE. Besides, we assessed changes in SV and CO by bedside ultrasound. Patients showing > 10 % increase in SV in response to VE were considered to be responders (26 patients), while the rest (14 patients) were defined as non-responders.

Results

Our data demonstrated that ΔSV-PLR and ΔCO- PLR were positively correlated with ΔSV-VE (r = 0.683, p < 0.001 and r = 0.374, p = 0.017, respectively), and the area under the ROC curve (AUC) of ΔSV-PLR was 0.879 (95 % CI [0.745 1.000], p < 0.001). The best cut-off value for ΔSV-PLR in predicting FR was 13 %, with its sensitivity and specificity were 81.8 and 86.3 %, respectively. ΔCVP, ΔHR, and ΔMAP were weak predictors of FR in the children.

Conclusions

Our study demonstrated that SV changes, as evaluated by noninvasive ultrasound combined with PLR, could effectively evaluate FR in children under mechanical ventilation after congenital cardiac surgery.