Transesophageal Echocardiographic Measurements of the Superior Vena Cava for Predicting Fluid Responsiveness in Patients Undergoing Invasive Positive Pressure Ventilation

Impact of transesophageal echocardiography dynamic monitoring of left ventricular preload on postoperative gastrointestinal function in colorectal cancer patients undergoing radical surgery

Background

Patients undergoing intestinal tumour surgery are fasted preoperatively for a series of bowel preparations, which makes it difficult to assess the patients' volume, posing a challenge to intraoperative fluid replacement. Besides, inappropriate fluid therapy can cause organ damage and affect the prognosis of patients, and it increases the burden of patients and has a certain impact on patients and families.

Material and methods

The authors designed a single-centre, prospective, single-blinded, randomized, parallel-controlled trial. Fifty-four patients undergoing elective radical resection of colorectal cancer were selected and divided into two groups according to whether transesophageal echocardiography (TEE) was used or not during the operation, that is the goal-directed fluid therapy (GDFT) group (group T) guided by TEE and the restrictive fluid therapy group (group C). Fluid replacement was guided according to left ventricular end-diastolic volume index (LVEDVI) in group T and according to restrictive fluid replacement regimen in group C.

Results

The first postoperative exhaust time and defecation time in group T [(45±21), (53±24) h] were significantly shorter (P<0.05) than those in group C [(63±26), (77±30) h]. There were no significant differences (P>0.05) in liquid intake time and postoperative nausea and vomiting incidences between the two groups. The total intraoperative fluid volume in group T was significantly higher (P<0.05) than that in group C. There was no significant difference (P>0.05) in urine volume between the two groups. There were no significant differences (P>0.05) in lactate content, mean arterial pressure, and heart rate at various time points between the two groups. The length of hospital stay in group C [(18±4) days] was significantly longer (P<0.05) than that in group T [(15±4) days].

Conclusions

For patients undergoing colorectal cancer surgery, fluid therapy by monitoring LVEDVI resulted in faster recovery of gastrointestinal function and shorter hospital stay.

Evaluation of fluid responsiveness with dynamic superior vena cava collapsibility index in mechanically ventilated patients

BACKGROUND

This study aimed to evaluate the predictive accuracy of the superior vena cava collapsibility index measured by transesophageal echocardiography and compare the index with stroke volume variation measured by FloTrac™/Vigileo™ in mechanically ventilated patients.

METHODS

In the prospective study, a total of 60 patients were enrolled for elective general surgery under mechanical ventilation, where all patients received 10 ml/kg of Ringer's lactate. Five kinds of related data were recorded before and after the fluid challenge, including the superior vena cava collapsibility index (SVC-CI), the ratio of E/e', cardiac index (CI), stroke volume variation (SVV), and central venous pressure (CVP). Based on the collected data after the fluid challenge, we classified the patients as responders (FR group) if their CI increased by at least 15% and the rest were non-responders (NR).

RESULTS

Twenty-five of 52 (48%) of the patients were responders, and 27 were non-responders (52%). The SVC-CI was higher in the responders (41.90 ± 11.48 vs 28.92 ± 9.05%, P < 0.01). SVC-CI was significantly correlated with △CI _FloTrac (r = 0.568, P < 0.01). The area under the ROC curve (AUROC) of SVC-CI was 0.838 (95% CI 0.728 ~ 0.947, P < 0.01) with the optimal cutoff value of 39.4% (sensitivity 64%, specificity 92.6%). And there was no significant difference in E/e' between the two groups (P > 0.05). The best cutoff value for SVV was 12.5% (sensitivity 40%, specificity 89%) with the AUROC of 0.68 (95% CI 0.53 ~ 0.826, P < 0.05).

CONCLUSIONS

The SVC-CI and SVV can predict fluid responsiveness effectively in mechanically ventilated patients. And SVC-CI is superior in predicting fluid responsiveness compared with SVV. The E/e' ratio and CVP cannot predict FR effectively.

TRIAL REGISTRATION

Chinese clinical trial registry (ChiCTR2000034940).

Ultrasound Imaging of the Superior Vena Cava: A State-of-the-Art Review

Greater interest in imaging the superior vena cava (SVC) in recent years has arisen because of increased focus on disorders of the right heart; the growing use of transvenous access lines, dialysis catheters, and device leads; and the emergence of right ventricular mechanical circulatory support systems via the transcatheter approach. As a low-pressure venous conduit in the right upper mediastinum, the SVC is prone to compression by various pathologic processes, to invasion by malignancies originating in nearby structures, and to complications arising from intraluminal device leads and indwelling catheters. Computed tomography and magnetic resonance venography are the modalities of choice for structural imaging of the SVC. Ultrasound allows a reasonable, yet less detailed anatomic assessment of this venous conduit. Spectral and color Doppler imaging by ultrasound are the most valuable noninvasive tools for the interrogation of SVC blood flow, a marker of the filling pattern of the right heart. Analysis of the velocity, duration, and direction of the Doppler waveforms and their phasic response to respiration makes it possible to distinguish normal from abnormal flow patterns and offers diagnostic insights into disorders that affect right heart function. The aims of this review are to demonstrate the added value SVC imaging provides during transthoracic and transesophageal echocardiographic studies, to outline its usefulness for the detection and evaluation of structural abnormalities, and to detail the role of spectral Doppler imaging in aiding the diagnosis of various disorders that affect the right heart.

Comparison of superior and inferior vena cava diameter variation measured with transthoracic echocardiography to predict fluid responsiveness in mechanically ventilated patients after abdominal surgery

Background

The volume status of patients after major abdominal surgery constantly varies owing to postoperative diverse issues comprising fluid loss or capillary leakage secondary to systemic inflammatory reaction syndrome, et.al, the precise fluid responsiveness assessment is crucial for those patients. The purpose of this study is to validate the transthoracic ultrasonographic measurement of superior and inferior vena cava variation in predicting fluid responsiveness of mechanically ventilated patients after surgery.

Methods

A total of 70 patients undergoing the scheduled major abdominal surgeries in the anesthesia ICU ward were included. The superior vena cava (SVC) collapsibility index (SVCCI), the inferior vena cava distensibility index (dIVC), SVC variation over the cardiac cycle (SVCV), and cardiac output (CO) were measured by transthoracic ultrasonography were recorded before and after fluid challenge test of 5 ml/kg crystalloid within 15 min. The responders were defined as a 15% or more increment in CO.

Results

Thirty patients (42.9%) responded to fluid challenge, while the remnant forty patients (57.1%) did not. The areas under the ROC curve (AUC) of SVCCI, dIVC and SVCV were 0.885 (95% CI, 0.786–0.949; P < 0.0001) and 0.727 (95% CI, 0.608–0.827; P < 0.001) and 0.751 (95% CI, 0.633–0.847; P < 0.0001), respectively. AUC_dIVC and AUC_SVCV were significantly lower when compared with AUC_SVCCI (P < 0.05). The optimal cutoff values were 19% for SVCCI, 14% for dIVC, and 15% for SVCV. The gray zone for SVCCI was 20%-25% and included 15.7% of patients, while 7%-27% for dIVC including 62.9% of patients and 9%-21% for SVCV including 50% of patients.

Conclusion

Superior vena cava-related parameters measured by transthoracic ultrasound are reliable indices to predict fluid responsiveness. The accuracy of SVCCI in mechanically ventilated patients after abdominal surgery is better than that of dIVC and SVCV.

Trial registration

ChiCTR-INR-17013093. The initial registration date was 24/10/2017.

The clinical effect and safety of new preoperative fasting time guidelines for elective surgery: a systematic review and meta-analysis

BACKGROUND

Traditional fasting and no drinking schemes (fasting for 8-12 hours and no drinking for 4-6 hours) affect the metabolism of the body. The new guidelines put forward by the American Association of Anesthesiologists (fasting for 6 hours, no drinking for 2 hours) obviously reduce the time of fasting and no drinking, but the clinical efficacy and safety need to be further confirmed. In this study, a meta-analysis of randomized controlled trials (RCTs) using the new guidelines and traditional protocols was conducted to provide an evidence-based foundation for elective surgery.

METHODS

The articles were searched in PubMed, EBSCO, MEDLINE, Science Direct, Cochrane Library, CNKI, China Biomedical Resources Database, Wanfang Database, Weipu, and Western Biomedical Journal Literature Database. RCTs related to fasting before surgery during the screening period were selected. Chinese and English search keywords included elective surgery, preoperative, fasting and no drinking, patient comfort, thirst, hunger, collapse, hypoglycemia, preoperative gastric volume, preoperative gastric juice pH, and intraoperative gastric volume. The RevMan 5.3 software provided by Cochrane collaboration network was used to evaluate the quality of included documents. Two professionals independently screened the literature, extracted data, and assessed the risk of bias.

RESULTS

A total of 6 studies were included. The incidence of hunger in patients undergoing elective surgery in the experimental group and control group was significantly different [Z=3.90; relative risk (RR) =0.58; 95% confidence interval (CI): 0.44, 0.76; P<0.0001]. The incidence of thirst was significantly different between the experimental group and control group (Z=7.22; RR =0.21; 95% CI: 0.13, 0.32; P<0.00001).

DISCUSSION

Meta-analysis results confirmed that the new guidelines can significantly reduce the hunger and thirst of patients, improve their satisfaction after surgery, and can be applied clinically.