Portal Vein Pulsatility as a Dynamic Marker of Venous Congestion Following Cardiac Surgery: An Interventional Study Using Positive End-Expiratory Pressure

We aimed to assess variations in the portal vein pulsatility index (PI) during mechanical ventilation following cardiac surgery. Method. After ethical approval, we conducted a prospective monocentric study at Amiens University Hospital. Patients under mechanical ventilation following cardiac surgery were enrolled. Doppler evaluation of the portal vein (PV) was performed by transthoracic echography. The maximum velocity (VMAX) and minimum velocity (VMIN) of the PV were measured in pulsed Doppler mode. The PI was calculated using the following formula (VMAX − VMIN)/(VMax). A positive end-expiratory pressure (PEEP) incremental trial was performed from 0 to 15 cmH₂O, with increments of 5 cmH₂O. The PI (%) was assessed at baseline and PEEP 5, 10, and 15 cmH₂O. Echocardiographic and hemodynamic parameters were recorded. Results. In total, 144 patients were screened from February 2018 to March 2019 and 29 were enrolled. Central venous pressure significantly increased for each PEEP increment. Stroke volumes were significantly lower after PEEP incrementation, with 52 mL (50–55) at PEEP 0 cmH₂O and 30 mL (25–45) at PEEP 15 cmH₂O, (p < 0.0001). The PI significantly increased with PEEP incrementation, from 9% (5–15) at PEEP 0 cmH₂O to 15% (5–22) at PEEP 5 cmH₂O, 34% (23–44) at PEEP 10 cmH₂O, and 45% (25–49) at PEEP 15 cmH₂O (p < 0.001). Conclusion. In the present study, PI appears to be a dynamic marker of the interaction between mechanical ventilation and right heart pressure after cardiac surgery. The PI could be a useful noninvasive tool to monitor venous congestion associated with mechanical ventilation.

Almitrine for COVID-19 critically ill patients – a vascular therapy for a pulmonary vascular disease: Three case reports

BACKGROUND

Several reports with clinical, histological and imaging data have observed the involvement of lung vascular function to explain the severe hypoxemia in coronavirus disease 2019 (COVID-19) patients. It has been hypothesized that an increased pulmonary blood flow associated with an impairment of hypoxic pulmonary vasoconstriction is responsible for an intrapulmonary shunt. COVID-19 may lead to refractory hypoxemia (PaO₂/FiO₂ ratio below 100 mmHg) despite mechanical ventilation and prone positioning. We hypothesized that the use of a pulmonary vasoconstrictor may help decrease the shunt and thus enhance oxygenation.

CASE SUMMARY

We report our experience with three patients with refractory hypoxemia treated with almitrine to enhance oxygenation. Low dose almitrine (Vectarion^®; Servier, Suresnes, France) was started at an infusion rate of 4 μg × kg/min on a central line. The PaO₂/FiO₂ ratio and total respiratory system compliance during almitrine infusion were measured. For the three patients, the PaO₂/FiO₂ ratio time-course showed a dramatic increase whereas total respiratory system compliance was unchanged. The three patients were discharged from the intensive care unit. The intensive care unit length of stay for patient 1, patient 2 and patient 3 was 30 d, 32 d and 31 d, respectively. Weaning from mechanical ventilation was performed 13 d, 18 d and 15 d after almitrine infusion for patient 1, 2 and 3, respectively. We found no deleterious effects on the right ventricular function, which was similar to previous studies on almitrine safety.

CONCLUSION

Almitrine may be effective and safe to enhance oxygenation in coronavirus disease 2019 patients. Further controlled studies are required.

Burnout syndrome in critical care team members: A monocentric cross sectional survey

INTRODUCTION

There has been a growing interest in evaluating the occurrence of burnout syndrome (BOS) among intensive care units (ICU) team over recent years. The aims of this study were to determine the prevalence of BOS among staff working in the Amiens University Hospital and to assess associated factors.

PATIENTS AND METHODS

Prospective observational study based on self-administered questionnaires filled in by physicians and non-physicians working in 3 ICUs. Demographic data, well-being assessment, work relationships, level of BOS and depressive symptoms were investigated. Logistic regression analysis was performed to identify variables independently associated with BOS.

RESULTS

One hundred and sixty-one questionnaires were analysed. Participation rate was 90%. Thirty-two respondents were physicians and 129 were non-physicians. The prevalence of BOS was 51% and was not significantly different between physicians and non-physicians (56% versus 50%; P=0.501). Respondents who reported BOS less frequently had regular leisure activities (54 [66%] versus 70 [87%], P=0.001). In the BOS group, well-being was significantly lower (4.8±2.5/10 versus 6±2/10, P=0.001), a desire to leave the job was more frequently expressed (50 [61%] versus 32 [40%], P=0.009) and depressive symptoms were significantly more frequent (41 [50%] versus 21 [27%], P=0.002). Factors independently associated with BOS were regular leisure activities (OR 0.24 [0.1-0.59]; P=0.002), the presence of depressive symptoms (OR 2.71 [1.26-5.84]; P=0.011) and a well-being visual analogue scale≥5 (OR 0.40 [0.18-0.89]; P=0.024).

CONCLUSIONS

BOS affects all ICU workers and is determined by multiple factors. Leisure activities and measures designed to improve well-being should be promoted.

Respiratory Effects of Sarafotoxins from the Venom of Different Atractaspis Genus Snake Species

Sarafotoxins (SRTX) are endothelin-like peptides extracted from the venom of snakes belonging to the Atractaspididae family. A recent in vivo study on anesthetized and ventilated animals showed that sarafotoxin-b (SRTX-b), extracted from the venom of Atractaspis engaddensis, decreases cardiac output by inducing left ventricular dysfunction while sarafotoxin-m (SRTX-m), extracted from the venom of Atractaspis microlepidota microlepidota, induces right ventricular dysfunction with increased airway pressure. The aim of the present experimental study was to compare the respiratory effects of SRTX-m and SRTX-b. Male Wistar rats were anesthetized, tracheotomized and mechanically ventilated. They received either a 1 LD₅₀ IV bolus of SRTX-b (n = 5) or 1 LD₅₀ of SRTX-m (n = 5). The low-frequency forced oscillation technique was used to measure respiratory impedance. Airway resistance (Raw), parenchymal damping (G) and elastance (H) were determined from impedance data, before and 5 min after SRTX injection. SRTX-m and SRTX-b injections induced acute hypoxia and metabolic acidosis with an increased anion gap. Both toxins markedly increased Raw, G and H, but with a much greater effect of SRTX-b on H, which may have been due to pulmonary edema in addition to bronchoconstriction. Therefore, despite their structural analogy, these two toxins exert different effects on respiratory function. These results emphasize the role of the C-terminal extension in the in vivo effect of these toxins.

Does inferior vena cava respiratory variability predict fluid responsiveness in spontaneously breathing patients?

INTRODUCTION

We have almost no information concerning the value of inferior vena cava (IVC) respiratory variations in spontaneously breathing ICU patients (SBP) to predict fluid responsiveness.

METHODS

SBP with clinical fluid need were included prospectively in the study. Echocardiography and Doppler ultrasound were used to record the aortic velocity-time integral (VTI), stroke volume (SV), cardiac output (CO) and IVC collapsibility index (cIVC) ((maximum diameter (IVCmax)- minimum diameter (IVCmin))/ IVCmax) at baseline, after a passive leg-raising maneuver (PLR) and after 500 ml of saline infusion.

RESULTS

Fifty-nine patients (30 males and 29 females; 57 ± 18 years-old) were included in the study. Of these, 29 (49 %) were considered to be responders (≥10 % increase in CO after fluid infusion). There were no significant differences between responders and nonresponders at baseline, except for a higher aortic VTI in nonresponders (16 cm vs. 19 cm, p = 0.03). Responders had a lower baseline IVCmin than nonresponders (11 ± 5 mm vs. 14 ± 5 mm, p = 0.04) and more marked IVC variations (cIVC: 35 ± 16 vs. 27 ± 10 %, p = 0.04). Prediction of fluid-responsiveness using cIVC and IVCmax was low (area under the curve for cIVC at baseline 0.62 ± 0.07; 95 %, CI 0.49-0.74 and for IVCmax at baseline 0.62 ± 0.07; 95 % CI 0.49-0.75). In contrast, IVC respiratory variations >42 % in SBP demonstrated a high specificity (97 %) and a positive predictive value (90 %) to predict an increase in CO after fluid infusion.

CONCLUSIONS

In SBP with suspected hypovolemia, vena cava size and respiratory variability do not predict fluid responsiveness. In contrast, a cIVC >42 % may predict an increase in CO after fluid infusion.

Short- versus Long-Sarafotoxins: Two Structurally Related Snake Toxins with Very Different in vivo Haemodynamic Effects

Sarafotoxin-m (24 amino acids) from the venom of Atractaspis microlepidota microlepidota was the first long-sarafotoxin to be identified, while sarafotoxin-b (21 aa) is a short-sarafotoxin from Atractaspis engaddensis. Despite the presence of three additional C-terminus residues in sarafotoxin-m, these two peptides display a high sequence homology and share similar three-dimensional structures. However, unlike sarafotoxin-b, sarafotoxin-m shows a very low in vitro affinity for endothelin receptors, but still has a very high in vivo toxicity in mammals, similar to that of sarafotoxin-b. We have previously demonstrated, in vitro, the crucial role of the C-terminus extension in terms of pharmacological profiles and receptor affinities of long- versus short-sarafotoxins. One possible hypothesis to explain the high in vivo toxicity of sarafotoxin-m could be that its C-terminus extension is processed in vivo, resulting in short-like sarafotoxin. To address this possibility, we investigated, in the present study, the in vivo cardiovascular effects of sarafotoxin-b, sarafotoxin-m and sarafotoxin-m−Cter (sarafotoxin-m without the C -terminus extension). Male Wistar rats were anaesthetised and mechanically ventilated. Invasive haemodynamic measurements and echocardiographic measurements of left and right ventricular function were performed. The rats were divided into four groups that respectively received intravenous injections of: saline, sarafotoxin-b (one LD₅₀), sarafotoxin-m (one LD₅₀) or sarafotoxin-m−Cter (one LD₅₀). All measurements were performed at baseline, at 1 minute (+1) and at 6 minutes (+6) after injection. Results: Sarafotoxin-b and sarafotoxin-m-Cter decreased cardiac output and impaired left ventricle systolic and diastolic function, whilst sarafotoxin-m decreased cardiac output, increased airway pressures and led to acute right ventricular dilatation associated with a decreased tricuspid annulus peak systolic velocity. Sarafotoxin-b and sarafotoxin-m−Cter appear to exert toxic effects via impairment of left ventricular function, whilst sarafotoxin-m increases airway pressures and impairs right ventricular function. These results do not support the hypothesis of an in vivo processing of long sarafotoxins.

Assessment of an uncalibrated pressure waveform device's ability to track cardiac output changes due to norepinephrine dose adjustments in patients with septic shock: a comparison with Doppler echocardiography

OBJECTIVES

The FloTrac Vigileo (FTV) estimates cardiac output (CO) on the basis of an uncalibrated arterial pressure waveform. To assess the ability of the third-generation of FTV (v.3.02) to track changes in CO following norepinephrine dose adjustment in patients with septic shock, we performed a comparative study using Doppler echocardiography (DE).

STUDY DESIGN

Prospective observational study.

PATIENTS

We prospectively included 20 mechanically ventilated patients receiving norepinephrine and monitored with the FTV. Five minutes after each change in norepinephrine dose (decided by the attending physician), CO was measured simultaneously with the FTV (CO(FTV)) and DE (CO(DE)). The changes in CO were compared. ROC curves were built to assess the ability of FTV to detect significant changes in CO(DE) of at least 15%.

RESULTS

Ninety pairs of CO variations measurements were made. The intertechnique correlation coefficient for changes in CO of at least 15% was r=0.59; P=0.0009. The AUC of a ROC curve built to test the FTV's ability to detect a CO(DE) increase of 15% or more was 0.783 (±0.083) (P=0.005). A CO(FTV) threshold value of 15% had a sensitivity of 54% (25-81) and a specificity of 87% (77-94). For a CO(DE) decrease of 15% or more, the ROC curve had an AUC of 0.616 (±0.075) (P=0.12) and a CO(FTV) threshold value of 13% yielded a sensitivity of 53% (27-79) and a specificity of 72% (60-82).

CONCLUSIONS

The FTV was unable to accurately track changes in CO following norepinephrine dose adjustments in critically ill patients with septic shock.

The passive leg-raising maneuver cannot accurately predict fluid responsiveness in patients with intra-abdominal hypertension

OBJECTIVES

The passive leg-raising maneuver is a reversible fluid-loading procedure used to predict fluid responsiveness in mechanically ventilated patients. The aim of the present study was to determine whether intra-abdominal hypertension (which impairs venous return) reduces the ability of passive leg raising to detect fluid responsiveness in critically ill ventilated patients.

DESIGN

A prospective study.

SETTING

The medical and surgical intensive care unit of a university medical center.

PATIENTS

Forty-one mechanically ventilated patients with a pulse pressure variation of >12%.

INTERVENTIONS

Stroke volume was continuously monitored by esophageal Doppler. Intra-abdominal pressure was measured via bladder pressure. After a passive leg-raising maneuver and a return to baseline, fluid loading with 500 mL of saline was performed. Hemodynamic parameters were recorded at each step. Nonresponders to volume loading were not analyzed (10 patients). Thirty-one patients were classified into two groups according to their response to passive leg raising: responders to passive leg raising (at least a 12% increase in stroke volume) and nonresponders to passive leg raising.

MEASUREMENTS AND MAIN RESULTS

Sixteen patients (52%) were responders to passive leg raising, and 15 (48%) were nonresponders to passive leg raising (i.e., false negatives). At baseline, the median intra-abdominal pressure was significantly higher in the nonresponders to passive leg raising than in the responders to passive leg raising (20 [6.5] vs. 11.5 [5.5], respectively; p < .0001). The area under the receiver-operating characteristic curve was 0.969 +/- 0.033. An intra-abdominal pressure cutoff value of 16 mm Hg discriminated between responders to passive leg raising and nonresponders to passive leg raising with a sensitivity of 100% (confidence interval, 78-100) and a specificity of 87.5% (confidence interval, 61.6-98.1). An intra-abdominal pressure of > or =16 mm Hg was the only independent predictor of nonresponse to passive leg raising in a multivariate analysis (odds ratio, 2.6 [confidence interval, 1.1-6.6]; p = .04).

CONCLUSIONS

An intra-abdominal pressure of > or =16 mm Hg seems to be responsible for false negatives to passive leg raising. Hence, the intra-abdominal pressure should be measured in critically ill ventilated patients, especially before performing passive leg raising.

Assessing fluid responsiveness in critically ill patients: False-positive pulse pressure variation is detected by Doppler echocardiographic evaluation of the right ventricle

OBJECTIVES

To determine whether peak systolic velocity of tricuspid annular motion assessed by tissue Doppler echocardiography (Sta), a right ventricular function parameter, can discriminate patients with true- and false-positive pulse pressure variation. Pulse pressure variation is used to predict fluid responsiveness in mechanically ventilated patients. However, this parameter has been reported to be falsely positive, especially in patients with right ventricular dysfunction.

DESIGN

A prospective study.

SETTING

Medical and surgical intensive care unit of a university hospital.

PATIENTS

Thirty- five mechanically ventilated patients hospitalized for >24 hrs with a pulse pressure variation of >12%.

INTERVENTIONS

Doppler echocardiography (including measurement of Sta and stroke volume) was performed before and after infusion of 500 mL of colloid solution. Patients were classified into two groups according to their response to fluid infusion: responders (at least 15% increase in stroke volume) and nonresponders.

MEASUREMENTS AND MAIN RESULTS

Twenty-three patients (66%) were responders (true-positive group) and 12 (34%) were nonresponders (false-positive group). Before volume expansion, Sta was statistically lower in the nonresponder group (0.13 [0.04] vs. 0.20 [0.05], p = .0004). The area under the curve of the receiver operating characteristic curve was 0.87 (95% confidence interval, 0.74-1). In patients with pulse pressure variation of >12%, a Sta cutoff value of 0.15 m/s discriminated between responders and nonresponders with a sensitivity of 91% (80-100) and a specificity of 83% (62-100).

CONCLUSIONS

A Sta value of <0.15 m/s seems to be an accurate parameter to detect false-positive pulse pressure variation. Echocardiography should therefore be performed before fluid infusion in patients with pulse pressure variation of >12%.