Postoperative volume balance: does stroke volume increase in Trendelenburg's position?

Mid‐regional plasma pro‐atrial natriuretic peptide and stroke volume responsiveness for detecting deviations in central blood volume following major abdominal surgery

Background

A reduced central blood volume is reflected by a decrease in mid‐regional plasma pro‐atrial natriuretic peptide (MR‐proANP), a stable precursor of ANP, and a volume deficit may also be assessed by the stroke volume (SV) response to head‐down tilt (HDT). We determined plasma MR‐proANP during major abdominal procedures and evaluated whether the patients were volume responsive by the end of the surgery, taking the fluid balance and the crystalloid/colloid ratio into account.

Methods

Patients undergoing pancreatic (n = 25), liver (n = 25), or gastroesophageal (n = 38) surgery were included prospectively. Plasma MR‐proANP was determined before and after surgery, and the fluid response was assessed by the SV response to 10^° HDT after the procedure. The fluid strategy was based mainly on lactated Ringer's solution for gastroesophageal procedures, while for pancreas and liver surgery, more human albumin 5% was administered.

Results

Plasma MR‐proANP decreased for patients undergoing gastroesophageal surgery (−9% [95% CI −3.2 to −15.3], p = .004) and 10 patients were fluid responsive by the end of surgery (∆SV > 10% during HDT) with an administered crystalloid/colloid ratio of 3.3 (fluid balance +1389 ± 452 ml). Furthermore, plasma MR‐proANP and fluid balance were correlated (r = .352 [95% CI 0.031–0.674], p < .001). In contrast, plasma MR‐proANP did not change significantly during pancreatic and liver surgery during which the crystalloid/colloid ratio was 1.0 (fluid balance +385 ± 478 ml) and 1.9 (fluid balance +513 ± 381 ml), respectively. For these patients, there was no correlation between plasma MR‐proANP and fluid balance, and no patient was fluid responsive.

Conclusion

Plasma MR‐proANP was reduced in fluid responsive patients by the end of surgery for the patients for whom the fluid strategy was based on more lactated Ringer's solution than human albumin 5%.

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.

Trendelenburg maneuver predicts fluid responsiveness in patients on veno-arterial extracorporeal membrane oxygenation

BACKGROUND

Evaluation of fluid responsiveness during veno-arterial extracorporeal membrane oxygenation (VA-ECMO) support is crucial. The aim of this study was to investigate whether changes in left ventricular outflow tract velocity-time integral (ΔVTI), induced by a Trendelenburg maneuver, could predict fluid responsiveness during VA-ECMO.

METHODS

This prospective study was conducted in patients with VA-ECMO support. The protocol included four sequential steps: (1) baseline-1, a supine position with a 15° upward bed angulation; (2) Trendelenburg maneuver, 15° downward bed angulation; (3) baseline-2, the same position as baseline-1, and (4) fluid challenge, administration of 500 mL gelatin over 15 min without postural change. Hemodynamic parameters were recorded at each step. Fluid responsiveness was defined as ΔVTI of 15% or more, after volume expansion.

RESULTS

From June 2018 to December 2019, 22 patients with VA-ECMO were included, and a total of 39 measurements were performed. Of these, 22 measurements (56%) met fluid responsiveness. The R² of the linear regression was 0.76, between ΔVTIs induced by Trendelenburg maneuver and the fluid challenge. The area under the receiver operating characteristic curve of ΔVTI induced by Trendelenburg maneuver to predict fluid responsiveness was 0.93 [95% confidence interval (CI) 0.81-0.98], with a sensitivity of 82% (95% CI 60-95%), and specificity of 88% (95% CI 64-99%), at a best threshold of 10% (95% CI 6-12%).

CONCLUSIONS

Changes in VTI induced by the Trendelenburg maneuver could effectively predict fluid responsiveness in VA-ECMO patients. Trial registration ClinicalTrials.gov, NCT03553459 (the TEMPLE study). Registered on May 30, 2018.

The effect of passive leg-raising maneuver on hemodynamic stability during anesthesia induction for adult cardiac surgery

Introduction

Some cardiac patients do not tolerate the intravenous fluid load commonly administered before anesthesia induction. This study investigated preinduction passive leg-raising maneuver (PLRM) as an alternative method to fluid loading before cardiac anesthesia.

Methods and materials

During a 6-month period, 120 adult elective heart surgery patients were enrolled in this study and allocated into 2 groups: PLRM group vs control group (n=60). Anesthesia was induced using midazolam, fentanyl, and cisatracurium. Initially, 250 mL of fluid was administrated intravenously in all of patients before anesthesia induction. Then in the PLRM group, PLRM was performed starting 2 minutes before anesthesia induction and continued for 20 minutes after tracheal intubation. In the control group, anesthesia was induced in a simple supine position. Heart rate, invasive mean arterial blood pressure (MAP), and central venous pressure (CVP) were recorded before PLRM, before anesthetic induction, before laryngoscopy, and at 5, 10, and 20 minutes after tracheal intubation. The hypotension episode rate (MAP <70 mmHg) and CVP changes were compared between the 2 groups. The predictive value of the ≥3 mmHg increase in CVP value in response to PLRM for hypotension prevention was defined.

Results

Hypotension rates were lower in the PLRM group (63.3% vs 81.6%; P-value 0.04), and MAP was higher among PLRM patients immediately before anesthetic injection, before laryngoscopy, and 20 minutes after intubation, compared to the control group. PLRM increased CVP by 3.57±4.9 mmHg (from 7.50±2.94 to 11.05±3.55 mmHg), which required several minutes to reach peak value, returning to baseline after 15 minutes. This change did not correlate to subsequent MAP changes; an increase in the CVP value ≥3 mmHg decreased the postinduction hypotension rate by 62.50%.

Conclusion

Preinduction PLRM can provide a more stable hemodynamic status in adult cardiac surgery patients and decreases anesthesia-induced hypotension rates by 62.50%. Rate of the changes in the CVP value caused by PLRM is not predictive of subsequent MAP changes.

Can a central blood volume deficit be detected by systolic pressure variation during spontaneous breathing?

BACKGROUND

Whether during spontaneous breathing arterial pressure variations (APV) can detect a volume deficit is not established. We hypothesized that amplification of intra-thoracic pressure oscillations by breathing through resistors would enhance APV to allow identification of a reduced cardiac output (CO). This study tested that hypothesis in healthy volunteers exposed to central hypovolemia by head-up tilt.

METHODS

Thirteen healthy volunteers were exposed to central hypovolemia by 45° head-up tilt while breathing through a facemask with 7.5 cmH2O inspiratory and/or expiratory resistors. A brachial arterial catheter was used to measure blood pressure and thus systolic pressure variation (SPV), pulse pressure variation and stroke volume variation . Pulse contour analysis determined stroke volume (SV) and CO and we evaluated whether APV could detect a 10 % decrease in CO.

RESULTS

During head-up tilt SV decreased form 91 (±46) to 55 (±24) mL (mean ± SD) and CO from 5.8 (±2.9) to 4.0 (±1.8) L/min (p < 0.05), while heart rate increased (65 (±11) to 75 (±13) bpm; P < 0.05). Systolic pressure decreased from 127 (±14) to 121 (±13) mmHg during head-up tilt, while SPV tended to increase (from 21 (±15)% to 30 (±13)%). Yet during head-up tilt, a SPV ≥ 37 % predicted a decrease in CO ≥ 10 % with a sensitivity and specificity of 78 % and 100 %, respectively.

CONCLUSION

In spontaneously breathing healthy volunteers combined inspiratory and expiratory resistors enhance SPV during head-up tilted induced central hypovolemia and allow identifying a 10 % reduction in CO. Applying inspiratory and expiratory resistors might detect a fluid deficit in spontaneously breathing patients.

TRIAL REGISTRATION

ClinicalTrials.gov number NCT02549482 Registered September 10(th) 2015.