Myth: the Trendelenburg position improves circulation in cases of shock

Change in left ventricular velocity time integral during Trendelenburg maneuver predicts fluid responsiveness in cardiac surgical patients in the operating room

BACKGROUND

Fluid responsiveness is an important topic for clinicians. We investigated whether changes in left ventricular outflow tract (LVOT) velocity time integral (VTI) during a Trendelenburg position (TP) maneuver can predict fluid responsiveness as a non-invasive marker in coronary artery bypass graft (CABG) surgery patients in the operating room.

METHODS

This prospective, single-center observational study, performed in the operating room, enrolled 65 elective CABG patients. Hemodynamic data coupled with transesophageal echocardiography monitoring of the LVOT VTI and the peak velocity were collected at each step [baseline 1, TP, baseline 2 and fluid challenge (FC)]. Patients whose VTI increased ≥15% after FC (500 mL of Gelofusine infusion within 30 min) were considered responders.

RESULTS

Twenty-eight (43.1%) patients were responders to fluid administration. VTI changes during the TP maneuver predicted fluid responsiveness with an area under the receiver operating characteristic curve (AUC) of 0.90 (95% CI, 0.79-0.96), with a sensitivity of 100%, and a specificity of 70% at a threshold of 10% (gray zone, 8-15%). The increase in VTI during the TP was correlated with the VTI changes induced by FC (r=0.61, P<0.0001). Changes in peak velocity and pulse pressure during the TP were poorly predictive of fluid responsiveness, with an AUC of 0.72 (95% CI: 0.60-0.82) and 0.66 (95% CI: 0.53-0.77), respectively.

CONCLUSIONS

An increase in VTI induced by the TP could predict fluid responsiveness in CABG patients in the operating room. However, changes in peak velocity and pulse pressure stimulated by the TP could not reliably predict fluid responsiveness.

Cerebral oxygenation in 45-degree trendelenburg position for robot-assisted radical prostatectomy: a single-center, open, controlled pilot study

BACKGROUND

Within the last decade, robotically-assisted laparoscopic prostatectomy (RALP) has become the standard for treating localized prostate cancer, causing a revival of the 45° Trendelenburg position. In this pilot study we investigated effects of Trendelenburg position on hemodynamics and cerebral oxygenation in patients undergoing RALP.

METHODS

We enrolled 58 patients undergoing RALP and 22 patients undergoing robot-assisted partial nephrectomy (RAPN) (control group) in our study. Demographic patient data and intraoperative parameters including cerebral oxygenation and cerebral hemodynamics were recorded for all patients. Cerebral function was also assessed pre- and postoperatively via the Mini Mental Status (MMS) exam. Changes in parameters during surgery were modelled by a mixed effects model; changes in the MMS result were evaluated using the Wilcoxon signed rank test.

RESULTS

Preoperative assessment of patient characteristics, standard blood values and vital parameters revealed no difference between the two groups.

CONCLUSIONS

Applying a 45° Trendelenburg position causes no difference in postoperative brain function, and does not alter cerebral oxygenation during a surgical procedure lasting up to 5 h. Further studies in larger patient cohorts will have to confirm these findings.

TRIAL REGISTRATION

German Clinical Trial Registry; DRKS00005094; Registered 12th December 2013-Retrospectively registered; https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00005094 .

Avaliação do fluxo de saída do ventrículo esquerdo em gatos anestesiados submetidos ao pneumoperitônio e à posição deTrendelenburg

RESUMO Objetivou-se avaliar os efeitos do pneumoperitônio e da posição de Trendelenburg sobre o fluxo de saída do ventrículo esquerdo em gatos anestesiados. Quatorze gatos foram alocados aleatoriamente em dois grupos, ambos submetidos ao pneumoperitônio com 10mmHg de dióxido de carbono (CO2). No grupo controle (GC n=7), os animais foram submetidos apenas ao pneumoperitônio e, no grupo Trendelenburg (GTREN n=7), os animais foram colocados em cefalodeclive 20° após o pneumoperitônio. A indução anestésica foi realizada com isoflurano, utilizando-se caixa de indução. Posteriormente, os animais foram mantidos sob anestesia inalatória com o mesmo fármaco. Foram avaliados a velocidade do fluxo de saída do ventrículo esquerdo (VFSVE), os gradientes máximo (GmáxSVE) e médio (GmédSVE) de pressão e a integral velocidade-tempo (IVT). Os parâmetros foram mensurados nos momentos T0 (basal), antes da insuflação; T5 (cinco), T15 (quinze) e T30 (trinta) minutos após a insuflação. Os resultados mostraram um aumento da VFSVE no GC, em T15 e T30 (P=0,024), e um aumento do GmáxSVE no GC, em T30 (P=0,045). As variáveis não se alteraram significativamente em nenhum momento no GTREN. Dessa forma, conclui-se que a posição de Trendelenburg favoreceu o sistema cardiovascular, preservando os índices de fluxo sanguíneo na saída do ventrículo esquerdo.

Passive leg raising during cardiopulmonary resuscitation results in improved neurological outcome in a swine model of prolonged ventricular fibrillation

OBJECTIVE

The objective was to evaluate whether passive leg raising during cardiopulmonary resuscitation in a porcine model of prolonged ventricular fibrillation improves hemodynamics, return of spontaneous circulation, 24-hour survival, and neurological outcome.

METHODS

Ventricular fibrillation was induced in 20 healthy Landrace/Large White piglets, which were subsequently left untreated for 8 minutes. Ten animals were randomly assigned into the control group and were resuscitated according to the 2005 European Resuscitation Council guidelines, and 10 piglets were assigned into the passive leg raising group and were resuscitated with the legs passively raised at 45° with the aid of a special purpose-made metallic device. End points were either return of spontaneous circulation or asystole.

RESULTS

Return of spontaneous circulation was observed in 6 and 9 animals from the control and the passive leg raising group, respectively (P = .121; odds ratio = 0.16; 95% confidence interval, 0.01-1.87). Just prior to the first defibrillation attempt, coronary perfusion pressure was significantly higher in the passive leg raising group (22.8 ± 9.5 vs 10.6 ± 6.5 mm Hg, P < .004); but no subsequent significant differences were observed. Although all animals that restored spontaneous circulation survived for 24 hours, neurologic alertness score was significantly better in the animals treated with passive leg raising (90 ± 10 vs 76.6 ± 12.1, P = .037).

CONCLUSIONS

Passive leg raising during cardiopulmonary resuscitation significantly increased coronary perfusion pressure in the minute prior to the first shock. Return of spontaneous circulation and 24-hour survival rate were comparable between groups. However, the animals in the passive leg raising group exhibited significantly higher neurological scores.

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 influence of the Trendelenburg position on haemodynamics: comparison of anaesthetized patients with ischaemic heart disease and healthy volunteers

This study compared the influence of the Trendelenburg position on haemodynamics in non-anaesthetized spontaneously breathing healthy volunteers and anaesthetized, mechanically ventilated patients with ischaemic heart disease scheduled for coronary artery bypass graft (CABG) surgery. Placing the anaesthetized patients scheduled for CABG surgery in the Trendelenburg position resulted in a significant increase in cardiac output and mean arterial pressure and a non-significant decrease in heart rate. In contrast, in the non-anaesthetized healthy volunteers, heart rate increased significantly but both cardiac output and mean arterial pressure changed non-significantly. Further studies will be needed to evaluate the haemodynamics of the Trendelenburg position.

Ten rules to assess and manage the acutely deteriorating patient: a practical mnemonic

The acutely deteriorating patient is a challenge to even the most seasoned provider. The ability to diagnosis the underlying condition quickly and accurately is vital to a successful outcome. We present a review of 10 critical aspects in the management of the crashing patient, based on up-to-date guidelines and organized as an easily remembered mnemonic. The A-A-B-B-C-C-D-D-E-E's of the deteriorating patient address many key pearls and current recommendations to give physicians an added advantage in the moment of crisis.

Influence of body position on hemodynamics in patients with ischemic heart disease undergoing cardiac surgery

INTRODUCTION

The cardiovascular response to decreased or increased preload in high-risk patients with ischemic heart disease enables us to understand the physiologic response to hemorrhage and its treatment. Although numerous studies have failed to show its effectiveness, the head-down position is still widely used to treat patients with hypotension and shock. The aim of our study was to evaluate the influence of body position on hemodynamics in high-risk patients undergoing coronary artery bypass graft surgery.

METHODS

In 16 patients with ischemic hearth disease and poor left ventricular function undergoing coronary artery bypass graft surgery, we measured cardiac output with thermodilution, arterial pressure, central venous pressure (CVP), pulmonary artery wedge pressure (PAWP) and heart rate in three different body positions: the horizontal position, 20 degrees head-up position, 20 degrees head-down position and back in the horizontal position. The measurements were made before and after cardiac surgery.

RESULTS

Before skin incision the change from horizontal to 20 degrees head-up position led to a nonsignificant decrease in cardiac output and a significant decrease in mean arterial pressure, CVP and PAWP. The change from 20 degrees head-up to 20 degrees head-down position led to a significant increase in cardiac output, mean arterial pressure, CVP and PAWP. After skin closure the change from horizontal to 20 degrees head-up position led to a nonsignificant decrease in cardiac output and mean arterial pressure and a significant decrease CVP and PAWP. The change from 20 degrees head-up to 20 degrees head-down position led to a nonsignificant increase in cardiac output and a significant increase in mean arterial pressure, CVP and PAWP. There were no significant changes in heart rate during the changes in position before or after surgery.

CONCLUSIONS

The results of our study showed a hemodynamic response similar to hemorrhage after placing the patients in a 20 degrees head-up position and improving hemodynamics in the head-down position in mechanically ventilated patients undergoing coronary artery bypass graft surgery.

Does patient position influence Doppler signal quality from the USCOM ultrasonic cardiac output monitor?

BACKGROUND

The USCOM1A continuous wave cardiac output monitor (USCOM Pty Ltd., Sydney, NSW, Australia) is a novel Doppler-based device used to measure cardiac output noninvasively. The proper alignment of the transducer, and hence the ultrasound beam to the aortic or pulmonary outflow tracts, is essential to acquire accurate measurements and often much time is spent on transducer and/or patient positioning. In this prospective, observational, crossover study, we investigated the effect of patient positioning on the acquisition of cardiac output measurement with USCOM1A.

METHODS

We measured cardiac output using USCOM1A in 30 healthy adult volunteers, each in five different positions: sitting, supine, Trendelenburg (20 degrees), left lateral tilt (20 degrees), and right lateral tilt (20 degrees) and compared the time required to obtain acceptable measurements. We also compared the quality of the Doppler signal obtained in these positions using a scoring system designed for this study.

RESULTS

There was a higher rate of failed measurement, the mean time to obtain the first acceptable measurement was prolonged and the optimal measurement obtained within a 5-min period was of a lower quality in the sitting position compared with the other four positions.

CONCLUSIONS

Our results suggested the sitting position is the least suitable and least reliable position in which to perform cardiac output measurements using USCOM1A compared with the supine, Trendelenburg (20 degrees), left lateral tilt (20 degrees), and right lateral tilt (20 degrees) positions.