Influence of passive leg elevation on the right ventricular function in anaesthetized coronary patients

The importance of assessing and correcting hydration status prior to right heart catheterisation: a pilot study

We evaluated whether fluid status could be accurately assessed (and corrected if necessary) prior to right heart catheterisation (RHC), to diagnose accurately post-capillary pulmonary hypertension (PHT) in patients with left heart disease risk factors. A non-invasive measure of fluid status prior to RHC identified fluid-depleted patients. Baseline RHC measurements were performed, and a novel provocation technique (passive leg raise) was compared to a 'one-dose-fits-all' fluid challenge and found to be equivalent.

Hemodynamic Responses to Provocative Maneuvers during Right Heart Catheterization

Rationale: Current guidelines recognize the utility of provocative maneuvers during right heart catheterization to aid the diagnosis of pulmonary hypertension. Few studies have compared the performance of different provocation maneuvers. Objectives: To assess the hemodynamic correlation among three provocative maneuvers, including their effect on pulmonary hypertension classification. Methods: This prospective trial was conducted between October 2016 and May 2018. Adult patients underwent three provocative maneuvers during right heart catheterization: passive leg raise (PLR), load-targeted supine bicycle exercise, and rapid crystalloid fluid infusion. Patients were classified as follows: no pulmonary hypertension, precapillary pulmonary hypertension, isolated postcapillary pulmonary hypertension, combined pre- and postcapillary pulmonary hypertension, and uncategorized pulmonary hypertension. We assessed the hemodynamic changes associated with each maneuver. We also assessed whether provocative maneuvers led to hemodynamic reclassification of the patient to either postcapillary pulmonary hypertension with provocation or exercise pulmonary hypertension. Results: Eighty-five patients (mean age 62 ± 12 years, 53% women) were included. Correlation between exercise and fluid challenge was moderate to strong (0.49-0.82; P < 0.001) for changes in right atrial pressure, mean pulmonary arterial pressure, pulmonary arterial wedge pressure, and cardiac index from baseline. Correlation between PLR and exercise (0.4-0.65; P < 0.001) and between PLR and fluid challenge (0.45-0.6; P < 0.001) was moderate for changes in right atrial pressure, mean pulmonary arterial pressure, pulmonary arterial wedge pressure, pulmonary vascular resistance, and cardiac index. Hemodynamic correlation between other provocative maneuvers was poor. Depending on provocative maneuver and classification criteria, there was significant variation in the number of patients reclassified as having exercise pulmonary hypertension (3-50%) or postcapillary pulmonary hypertension with provocation (11-48%). Conclusions: Hemodynamic determinations during exercise and fluid challenge showed moderate to strong hemodynamic correlation. Moderate hemodynamic correlation was seen between PLR and exercise or fluid challenge. Although some provocative maneuvers demonstrate good hemodynamic correlation, there is inconsistency when using these maneuvers to identify patients with postcapillary or exercise pulmonary hypertension.

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.

Fluid responsiveness to passive leg raising in patients with and without coronary artery disease: A prospective observational study

Introduction:

Hemodynamic stability and fluid responsiveness (FR) assume importance in perioperative management of patients undergoing major surgery. Passive leg raising (PLR) is validated in assessing FR in intensive care unit patients. Very few studies have examined FR to PLR in intraoperative scenario. We prospectively studied FR to PLR using transesophageal echocardiography (TEE), in patients with no coronary artery disease (CAD) undergoing major neurosurgery and those with CAD undergoing coronary artery bypass grafting (CABG).

Methods:

We enrolled 29 adult consenting patients undergoing major neurosurgery with TEE monitoring and 25 patients undergoing CABG. After induction of anesthesia, baseline hemodynamic parameters were obtained which was followed by PLR using automated adjustment of the operating table. Clinical and TEE-derived hemodynamic parameters were recorded at 1 and 10 min after PLR following which patients were returned to supine position.

Results:

A total of 162 TEE and clinical examinations were done across baseline, 1 and 10 min after PLR; and paired comparison was done at data intervals of baseline versus 1 min PLR, baseline versus 10 min PLR, and 1 min versus 10 min PLR. There was no significant change in hemodynamic variables at any of the paired comparison intervals in patients undergoing neurosurgery. CABG cases had significant hemodynamic improvement 1 min after PLR, partially sustained at 10 min.

Conclusion:

Patients undergoing CABG had significant hemodynamic response to PLR, whereas non-CAD patients undergoing neurosurgery did not. A blood pressure–left ventricular end-diastolic volume combination represented strong correlation in response prediction (Pearson's coefficient 0.641; P < 0.01).

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

Fluid boluses are often administered with the aim of improving tissue hypoperfusion in shock. However, only approximately 50% of patients respond to fluid administration with a clinically significant increase in stroke volume. Fluid overload can exacerbate pulmonary edema, precipitate respiratory failure, and prolong mechanical ventilation. Therefore, it is important to predict which hemodynamically unstable patients will increase their stroke volume in response to fluid administration, thereby avoiding deleterious effects. Passive leg-raising (lowering the head and upper torso from a 45° angle to lying supine [flat] while simultaneously raising the legs to a 45° angle) is a transient, reversible autotransfusion that simulates a fluid bolus and is performed to predict a response to fluid administration. The article reviews the accuracy, physiological effects, and factors affecting the response to passive-leg raising to predict fluid responsiveness in critically ill patients.

Pulmonary Hypertensive Crisis on Induction of Anesthesia

Anesthesia for lung transplantation remains one of the highest risk surgeries in the domain of the cardiothoracic anesthesiologist. End-stage lung disease, pulmonary hypertension, and right heart dysfunction as well as other comorbid disease factors predispose the patient to cardiovascular, respiratory and metabolic dysfunction during general anesthesia. Perhaps the highest risk phase of surgery in the patient with severe pulmonary hypertension is during the induction of anesthesia when the removal of intrinsic sympathetic tone and onset of positive pressure ventilation can decompensate a severely compromised cardiovascular system. Severe hypotension, cardiac arrest, and death have been reported previously. Here we present 2 high-risk patients for lung transplantation, their anesthetic induction course, and outcomes. We offer suggestions for the safe management of anesthetic induction to mitigate against hemodynamic and respiratory complications.

Passive Leg Raising Correlates with Future Exercise Capacity after Coronary Revascularization

Hemodynamic properties affected by the passive leg raise test (PLRT) reflect cardiac pumping efficiency. In the present study, we aimed to further explore whether PLRT predicts exercise intolerance/capacity following coronary revascularization. Following coronary bypass/percutaneous coronary intervention, 120 inpatients underwent a PLRT and a cardiopulmonary exercise test (CPET) 2–12 days during post-surgery hospitalization and 3–5 weeks after hospital discharge. The PLRT included head-up, leg raise, and supine rest postures. The end point of the first CPET during admission was the supra-ventilatory anaerobic threshold, whereas that during the second CPET in the outpatient stage was maximal performance. Bio-reactance-based non-invasive cardiac output monitoring was employed during PLRT to measure real-time stroke volume and cardiac output. A correlation matrix showed that stroke volume during leg raise (SV_LR) during the first PLRT was positively correlated (R = 0.653) with the anaerobic threshold during the first CPET. When exercise intolerance was defined as an anaerobic threshold < 3 metabolic equivalents, SV_LR / body weight had an area under curve value of 0.822, with sensitivity of 0.954, specificity of 0.593, and cut-off value of 1504·10^-3mL/kg (positive predictive value 0.72; negative predictive value 0.92). Additionally, cardiac output during leg raise (CO_LR) during the first PLRT was related to peak oxygen consumption during the second CPET (R = 0.678). When poor aerobic fitness was defined as peak oxygen consumption < 5 metabolic equivalents, CO_LR / body weight had an area under curve value of 0.814, with sensitivity of 0.781, specificity of 0.773, and a cut-off value of 68.3 mL/min/kg (positive predictive value 0.83; negative predictive value 0.71). Therefore, we conclude that PLRT during hospitalization has a good screening and predictive power for exercise intolerance/capacity in inpatients and early outpatients following coronary revascularization, which has clinical significance.

Hemodynamic effect of full flexion of the hips and knees in the supine position: a comparison with straight leg raising

Background

Straight raising of the legs in the supine position or Trendelenburg positioning has been used to treat hypotension or shock, but the advantages of these positions are not clear and under debate. We performed a crossover study to evaluate the circulatory effect of full flexion of the hips and knees in the supine position (exaggerated lithotomy), and compare it with straight leg raising.

Methods

This study was a prospective randomized crossover study from the tertiary care unit at our university hospital. Twenty-two patients scheduled for off-pump coronary artery bypass surgery were enrolled. Induction and maintenance of anesthesia were standardized. Exaggerated lithotomy position or straight leg raising were randomly selected in the supine position. Hemodynamic variables were measured in the following sequence: 10 min after induction, 1, 5, and 10 min following the designated position, and 1 and 5 min after returning to the supine position. Ten min later, the other position was applied to measure the same hemodynamic variables.

Results

During the exaggerated lithotomy position, cerebral and coronary perfusion pressure increased significantly (P < 0.01) without a change in cardiac output. During straight leg raising, cardiac output increased at 5 min (P < 0.05) and cerebral and coronary perfusion pressures did not increase except for cerebral perfusion pressure at 1 min. However, the difference between the two groups at each time point in terms of cerebral perfusion pressure was clinically insignificant.

Conclusions

Full flexion of the hips and knees in the supine position did not increase cardiac output but may be more beneficial than straight leg raising in terms of coronary perfusion pressure.

The role of passive leg raising to predict fluid responsiveness in pediatric intensive care unit patients

OBJECTIVE

Fluid challenge is often used to predict fluid responsiveness in critically ill patients. Inappropriate fluid expansion can lead to some unwanted side effects; therefore, we need a noninvasive predictive parameter to assess fluid responsiveness. We want to assess the hemodynamic parameter changes after passive leg raising, which can mimic fluid expansion, to predict fluid responsiveness in pediatric intensive care unit patients and to get a cutoff value of cardiac index in predicting fluid responsiveness in pediatric patients.

DESIGN

Nonrandomized experimental study.

SETTING

Tertiary academic pediatric intensive care.

PATIENTS

Children admitted to pediatric intensive care.

INTERVENTION

Hemodynamic parameters were assessed at baseline, after passive leg raising, at second baseline, and after volume expansion (10 mL/kg normal saline infusion over 15 mins).

MEASUREMENTS AND MAIN RESULTS

We measured the heart rate, systolic blood pressure, and stroke volume and cardiac index using Doppler echocardiography. The hemodynamic parameter changes induced by passive leg raising were monitored. Among 40 patients included in the study, 20 patients had a cardiac index increase of ≥10% after volume expansion (responders). Changes in heart rate, systolic blood pressure, and stroke volume after passive leg raising did not significantly relate to the response to volume expansion. There was significant relation between changes in cardiac index to predict fluid responsiveness (p = .012, r(2) = .22, 95% confidence interval 1.529 to 31.37). A cardiac index increase by ≥10% induced by passive leg raising predicted preload-dependent status with sensitivity of 55% and specificity of 85% (area under the curve 0.71 ± 0.084, 95% confidence interval 0.546-0.874).

CONCLUSION

The concomitant measurements in cardiac index changes after the passive leg raising maneuver can be helpful in predicting who might have an increase in cardiac index with subsequent fluid resuscitation.

Passive leg raising induced brachial artery dilation: is an old technique a simpler method to measure endothelial function?

OBJECTIVES

Passive leg raising (PLR) is a diagnostic maneuver that has been shown to cause brachial artery dilation (BAD). The objectives of this study were to compare BAD induced by PLR with flow mediated dilation (FMD), and to investigate the mechanism of PLR-BAD. We studied a total of 75 subjects with and without cardiovascular risk factors/disease in order to provide a wide range of FMD responses.

METHODS

Using ultrasound, PLR-BAD and FMD induced by release of arterial cuff occlusion were measured.

RESULTS

BA diameter increased from 0.33+0.06 at baseline to 0.35+/-0.06 cm (p<.001) (4.8% increase) upon PLR and from 0.33+/-0.06 to 0.37+/-0.06 (11.8%) upon hyperemia. PLR induced BAD was significantly correlated with FMD (r=.82, p<.001). On receiver operating characteristic analysis of the two techniques, the area under the curve was 0.86 (95% CI 0.79-0.94, p<.001). Heart rate variability measures remained unchanged upon PLR indicating minimal contributions from changes in autonomic activity. The combination of FMD and PLR did not result in greater BAD than did FMD alone consistent with a common underlying mechanism. Mean blood flow velocity increased prior to BAD suggesting that shear stress increases prior to BAD.

CONCLUSIONS

BAD occurs in response to PLR and is proportional to FMD, although the magnitude of PLR-BAD is less than half that of FMD. It appears to occur by the same endothelial dependent mechanism as FMD. PLR-BAD may be used as a surrogate measure of FMD to evaluate vascular function, and has the advantage of being simpler to perform.

The effects of passive leg raising on arterial wave reflection in healthy adults

BACKGROUND

Passive leg raising (PLR) produces hemodynamic and physiological changes related to centralizing blood volume and baroreceptor activation.

METHODS/RESULTS

To evaluate the effects of PLR on central hemodynamics, we prospectively studied 50 healthy participants (80% male, age 37 +/- 12 years). Central aortic blood pressures (CA-BPs) and reflected wave properties were evaluated using applanation tonometry at baseline and upon 1 min of PLR. Heart rate (HR) was unchanged. Brachial artery (BA)-systolic BP, BA-diastolic BP, and BA-pulse pressure (PP) all decreased from baseline to PLR. Changes in BA-PP were significantly greater than changes in CA-PP. Reflected wave augmentation pressure (P(s)-P(i)), HR corrected augmentation index (AIx@75), and augmentation index decreased significantly [(P(s)-P(i)): 5 +/- 6 vs. 4 +/-5, P < 0.001; AIx@75%: 10 +/- 13 vs. 7 +/- 12, P = 0.004; AI%: 14 +/- 12 vs. 12 +/- 12, P = 0.014, respectively]. HR corrected ejection duration (ED(c)), round trip travel time (deltat(p)), and reflected wave systolic duration (deltat(r)) all increased upon PLR [ED(c): 433 +/- 15 vs. 444 +/- 17, P < 0.001; deltat(p): 149 +/- 18 vs. 156 +/- 20, P = 0.003; deltat(r): 174 +/- 33 vs. 179 +/- 32, P = 0.046, respectively]. Indices of left ventricular (LV) workload including wasted LV energy and tension-time index decreased upon PLR.

CONCLUSION

PLR decreases the amplitude and delays the onset of the reflected aortic pressure wave. This decreases wasted LV pressure energy and workload.

Passive leg raising

OBJECTIVE

To assess whether the passive leg raising test can help in predicting fluid responsiveness.

DESIGN

Nonsystematic review of the literature.

RESULTS

Passive leg raising has been used as an endogenous fluid challenge and tested for predicting the hemodynamic response to fluid in patients with acute circulatory failure. This is now easy to perform at the bedside using methods that allow a real time measurement of systolic blood flow. A passive leg raising induced increase in descending aortic blood flow of at least 10% or in echocardiographic subaortic flow of at least 12% has been shown to predict fluid responsiveness. Importantly, this prediction remains very valuable in patients with cardiac arrhythmias or spontaneous breathing activity.

CONCLUSIONS

Passive leg raising allows reliable prediction of fluid responsiveness even in patients with spontaneous breathing activity or arrhythmias. This test may come to be used increasingly at the bedside since it is easy to perform and effective, provided that its effects are assessed by a real-time measurement of cardiac output.

The Influence of Passive Leg Elevation on the Cross-Sectional Area of the Internal Jugular Vein and the Subclavian Vein in Awake Adults

The aim of this study was to evaluate the influence of passive leg elevation and Trendelenburg position on the cross-sectional area (CSA) of the internal jugular (IJ) and subclavian veins (SCV). Ultrasound imaging was used for the following measurements of both the IJV and SCV: baseline in the supine position (control); Trendelenburg position 15°; reverse Trendelenburg position 15° and passive leg elevation 50°. Twenty healthy male volunteers were studied. Mean CSA of the IJV was 1.12±0.57 cm2 in control, 1.66±0.67 cm2 in the Trendelenburg position (P <0.0001 vs. control), 0.38±0.23 cm2 in the reverse Trendelenburg position (P <0.0001 vs. control), and 1.40±0.64 cm2 during passive leg elevation (P <0.0001 vs. control). Mean CSA of the SCV was 0.92±0.23 cm2 in control, 0.98±0.17 cm2 in the Trendelenburg position, 0.86±0.21 cm2 in the reverse Trendelenburg position and 0.93±0.18 cm2 during passive leg elevation. The results indicate that passive leg elevation increases the CSA of the IJV but has little effect on the SCV. The CSA of the IJV appears to be influenced more by gravitational factors than the SCV.

Inferior vena cava diameter and central venous pressure correlation during cardiac surgery

OBJECTIVE

The purpose of this study was to determine whether a relationship exists between the inferior vena cava diameter (IVCD) or the superior vena cava diameter (SVCD) measured at the point of entry into the right atrium using transesophageal echocardiography (TEE) and the central venous pressure (CVP) under different experimental conditions.

DESIGN

Prospective study.

SETTING

University hospital, single institution.

PARTICIPANTS

Seventy patients undergoing elective cardiac surgery.

INTERVENTIONS

CVP, IVCD, and SVCD were measured in a 2-dimensional, long-axis midesophageal bicaval view at end-diastole with electrocardiographic synchronization. Data were recorded during suspended ventilation, before and after leg elevation, and at different levels of positive end-expiratory pressure (0, 5, and 10 cmH(2)O).

MEASUREMENTS AND MAIN RESULTS

The relationship between IVCD and CVP had 2 portions: A first (CVP <or=11 mmHg) in which the IVCD showed a strong correlation with the CVP (R = 0.801, p < 0.001; CVP = 2.009 + [0.312 * IVCD]) and a second (CVP >11 mmHg) in which the correlation was poor (R = 0.272, p = 0.065). No correlation between SVCD and CVP was observed.

CONCLUSION

A strong correlation between TEE-derived IVCD measured at the point of entry into the right atrium and CVP was observed in cardiac surgical patients when CVP was <or=11 mmHg.

[Echocardiography during acute hemodynamic instability]

In light of the growing proportion of illness in the general population, the complexity of modern surgery requires precise perioperative hemodynamic monitoring. Echocardiography has emerged over the past 15 years as an especially valuable diagnostic instrument for intensive medicine. No other monitoring technique provides in such a short time, with so little invasiveness, so much additional anatomic information for determining the cause of acute hemodynamic instability. There is of course the possibility of proceeding transthoracally at first, with poor imaging quality but noninvasively, or transesophageally. However, perioperative hemodynamic monitoring allows even less experienced operators to detect the various differential diagnoses of acute hemodynamic instability with an easily managed number of standard images. Starting from the first standard settings, depending on pathology the imaging should continue selectively with transthoracal echocardiography in the short parasternal axis or transesophageal echocardiography in the transgastral short midpapillary axis.