Huaiwu He

The peripheral perfusion index and transcutaneous oxygen challenge test are predictive of mortality in septic patients after resuscitation.

IntroductionThe peripheral perfusion index (PI) is a noninvasive numerical value of peripheral perfusion, and the transcutaneous oxygen challenge test (OCT) is defined as the degree of transcutaneous partial pressure of oxygen (PtcO2) response to 1.0 FiO2. The value of noninvasive monitoring peripheral perfusion to predict outcome remains to be established in septic patients after resuscitation. Moreover, the prognostic value of PI has not been investigated in septic patients.MethodsForty-six septic patients, who were receiving PiCCO-Plus cardiac output monitoring, were included in the study group. Twenty stable postoperative patients were studied as a control group. All the patients inspired 1.0 of FiO2 for 10 minutes during the OCT. Global hemodynamic variables, traditional metabolic variables, PI and OCT related-variables were measured simultaneously at 24 hours after PiCCO catheter insertion. We obtained the 10min-OCT ((PtcO2 after 10 minutes on inspired 1.0 oxygen) - (baseline PtcO2)), and the oxygen challenge index ((10min-OCT)/(PaO2 on inspired 1.0 oxygen - baseline PaO2)) during the OCT.ResultsThe PI was significantly correlated with baseline PtcO2, 10min-OCT and oxygen challenge index (OCI) in all the patients. The control group had a higher baseline PtcO2, 10min-OCT and PI than the septic shock group. In the sepsis group, the macro hemodynamic parameters and ScvO2 showed no differences between survivors and nonsurvivors. The nonsurvivors had a significantly lower PI, 10min-OCT and OCI, and higher arterial lactate level. The PI, 10min-OCT and OCI predicted the ICU mortality with an accuracy that was similar to arterial lactate level. A PI <0.2 and a 10min-OCT <66mmHg were related to poor outcome after resuscitation.ConclusionsThe PI and OCT are predictive of mortality for septic patients after resuscitation. Further investigations are required to determine whether the correction of an impaired level of peripheral perfusion may improve the outcome of septic shock patients.

Passive Leg Raising in Intensive Care Medicine.

IntrodUctIon Fluid challenge is a common diagnostic method to help the physician determine fluid responsiveness, which is an important component of fluid management in critically ill patients.[1] Raising legs of a patient induces the transfer of a variable amount of blood (approximately 200–300 ml) contained in the venous reservoir from the limb to central venous compartment. According to Franck‐Starling curve, this transient increase of preload might lead to an increase in cardiac output (CO) in future responders resulting from their preload‐reserve status. Many clinical studies have validated passive leg raising (PLR), and the advantage of PLR is attractive in Intensive Care Unit (ICU). Recently, PLR has been suggested as a simple and potential method to predict fluid responsiveness, which is similar to an “auto-fluid challenge” without a drop of fluid.[2] However, one study revealed poor application of PLR in the real world.[3] We acknowledged that the lack of education on PLR would result in the current practice. On the other hand, the application of PLR might be not simple in clinical practice, and the holy grail of fluid responsiveness still needs to be discovered.[4] The standard of PLR has not been established, and some questions of PLR merit discussion.

High central venous-to-arterial CO2 difference/arterial-central venous O2 difference ratio is associated with poor lactate clearance in septic patients after resuscitation

OBJECTIVE Recently, the central venoarterial carbon dioxide difference/arterial-central venous oxygen difference (P(v-a)CO2/C(a-v)O2) ratio has been suggested as an additional indicator of anaerobic metabolism. We investigated the relationship between the P(v-a)CO2/C(a-v)O2 ratio and 8-hour lactate clearance (LC) in septic patients after resuscitation. METHODS AND RESULTS We prospectively obtained 168 sets of measurements from 84 septic patients. The arterial and central venous blood gases were measured simultaneously at enrollment and 8 hours after resuscitation. The P(v-a)CO2/C(a-v)O2 (r = -0.24, P = .028) at T8 was negatively correlated with 8-hour LC after resuscitation in all patients. The patients with 8-hour LC ≥ 10% exhibited significantly lower P(v-a)CO2/C(a-v)O2 ratios and intensive care unit mortality after resuscitation than the patients with 8-hour LC < 10%. The area under the receiver operating characteristic curve of the P(v-a)CO2/C(a-v)O2 ratio for the detection of LC ≥ 10% was the greatest and was significantly better than that of the central venous oxygen saturation and similar to that of the P(v-a)CO2. Moreover, a P(v-a)CO2/C(a-v)O2 < 1.23 at T8 is related to poor 8-hour LC rate (LC ≥ 10%) in the patients with normalized central venous oxygen saturation values (≥70%) after resuscitation. CONCLUSIONS The high P(v-a)CO2/C(a-v)O2 ratio is associated with poor LC after resuscitation. The P(v-a)CO2/C(a-v)O2 ratio may provide useful information for assessing the LC potential and optimizing the LC rate.

The transcutaneous oxygen challenge test: a noninvasive method for detecting low cardiac output in septic patients.

ABSTRACT The transcutaneous partial pressure of oxygen (PtcO2) index has been used to detect low-flow state in circulatory failure, but the value of the transcutaneous oxygen challenge test (OCT) to estimate low cardiac output has not been thoroughly evaluated. The prospective observational study examined 62 septic patients requiring PiCCO-Plus for cardiac output monitoring. Simultaneous basal blood gases from the arterial, central venous catheters were obtained. Cardiac indices were measured by the transpulmonary thermodilution technique at the same time, then the 10-min inspired 1.0 fractional inspired oxygen concentration (FIO2) defined as the OCT was performed. Transcutaneous partial pressure of oxygen was measured continuously by using a noninvasive transcutaneous monitor throughout the test. The values for arterial pressure of oxygen (PaO2) were examined on inspired of 1.0 FIO2. We calculated the PtcO2 index = (baseline PtcO2/baseline PaO2), 10-min OCT (10 OCT) = (PtcO2 after 10 min on inspired 1.0 O2) − (baseline PtcO2), and the oxygen challenge index = (10 OCT) / (PaO2 on inspired 1.0 O2 − baseline PaO2). Patients were divided into two groups: a normal cardiac index (CI) group with CI of greater than 3 L/min per m2 (n = 41) and a low CI group with CI of 3 L/min per m2 or less (n = 21). The 10 OCT and the oxygen challenge index predicted a low CI (⩽3 L/min per m2) with an accuracy that was similar to central venous oxygen saturation, which was significantly better than the PtcO2 index. For a 10 OCT value of 53 mmHg, sensitivity was 0.83; specificity, 0.86; a positive predictive value, 0.92; and a negative predictive value, 0.72 for detecting CI of 3 L/min per m2 or less. We propose that the OCT substituted for the PtcO2 index as an accurate alternative method of PtcO2 for revealing low CI in septic patients.

Using Critical Care Chest Ultrasonic Examination in Emergency Consultation: A Pilot Study

The purpose of this study was to investigate the effects of critical care chest ultrasonic examination (CCUE) by intensivist on the diagnosis and treatment decisions in emergent consultation for patients who may have a problem-need transfer to an intensive care unit (ICU). A total of 130 patients who required emergent consultation in the ordinary wards were included in this study. Patients were randomly divided into conventional group (n = 63) and CCUE group (n = 67, added CCUE). The two groups showed no significant differences in general clinical information or final diagnosis (p > 0.05). The CCUE group had a shorter time to preliminary diagnosis, final diagnosis, treatment response and X-ray/computed tomography examination; a delay in ICU transfer and ICU stay days (3.9 ± 1.2 vs. 5.4 ± 1.9 d, p < 0.05) and a higher diagnostic accuracy than the conventional group (p < 0.001). In conclusion, CCUE could help early diagnosis and therapy for the patient who may need to transfer to the ICU and reduce the ICU stay for in-hospital patients in emergent consultation.

Positive End-expiratory Pressure Titration after Alveolar Recruitment Directed by Electrical Impedance Tomography

Background:Electrical impedance tomography (EIT) is a real-time bedside monitoring tool, which can reflect dynamic regional lung ventilation. The aim of the present study was to monitor regional gas distribution in patients with acute respiratory distress syndrome (ARDS) during positive-end-expiratory pressure (PEEP) titration using EIT. Methods:Eighteen ARDS patients under mechanical ventilation in Department of Critical Care Medicine of Peking Union Medical College Hospital from January to April in 2014 were included in this prospective observational study. After recruitment maneuvers (RMs), decremental PEEP titration was performed from 20 cmH2O to 5 cmH2O in steps of 3 cmH2O every 5–10 min. Regional over-distension and recruitment were monitored with EIT. Results:After RMs, patient with arterial blood oxygen partial pressure (PaO2) + carbon dioxide partial pressure (PaCO2) >400 mmHg with 100% of fractional inspired oxygen concentration were defined as RM responders. Thirteen ARDS patients was diagnosed as responders whose PaO2 + PaCO2 were higher than nonresponders (419 ± 44 mmHg vs. 170 ± 73 mmHg, P < 0.0001). In responders, PEEP mainly increased recruited pixels in dependent regions and over-distended pixels in nondependent regions. PEEP alleviated global inhomogeneity of tidal volume and end-expiratory lung volume. PEEP levels without significant alveolar derecruitment and over-distension were identified individually. Conclusions:After RMs, PEEP titration significantly affected regional gas distribution in lung, which could be monitored with EIT. EIT has the potential to optimize PEEP titration.

The Prognostic Value of Central Venous-to-Arterial CO2 Difference/Arterial-Central Venous O2 Difference Ratio in Septic Shock Patients with Central Venous O2 Saturation ≥80%:

Background: It is a great challenge for physician to assess the relationship between O2 delivery and O2 consumption in septic shock patients with high ScvO2. Recently, the venous-to-arterial CO2 difference/arterial-central venous O2 difference ratio (P(v-a)CO2/C(a-v)O2) has shown potential for reflecting anaerobic metabolism. Therefore, we evaluated the value of using the P(v-a)CO2/C(a-v)O2 ratio to predict mortality and assess anaerobic metabolism in septic shock patients with high ScvO2 (≥ 80%). Methods: This was a clinical investigation of septic shock patients on the P(v-a)CO2/C(a-v)O2 ratio in the intensive care unit (ICU) department. The patients’ arterial and central venous blood gas levels were measured simultaneously at enrollment (T0) and 24 h (T24) after resuscitation. Results: A total of 61 patients with high ScvO2 at T24 after resuscitation were selected for analysis. The ICU mortality rate in the septic shock patients was 20% (12/61). The nonsurvivors had a significantly higher P(v-a)CO2, P(v-a)CO2/C(a-v) O2 ratio, arterial lactate level and lower lactate clearance at T24 after resuscitation. The P(v-a)CO2/C(a-v)O2 ratio had the biggest the areas under the receiver operating characteristic (AUC) for predicting ICU mortality. For predicting ICU mortality, a threshold of P(v-a)CO2/C(a-v)O2 ratio ≥1.6 was associated with a sensitivity of 83% and a specificity of 63%. Multivariate analysis showed P(v-a)CO2/C(a-v)O2 ratio at both T0 (RR 5.597, P = 0.024) and T24 (RR 5.812, P = 0.031) was an independent predictor of ICU mortality. Including the ratio into the regression model showed a bigger AUC than without the ratio (0.886 vs. 0.833). Conclusions: The P(v-a)CO2/C(a-v)O2 ratio is an independent predictor of ICU mortality in septic shock patients with high ScvO2 after resuscitation. It is worthy of consideration to recruit microcirculation to correct the high ratio in high ScvO2 case.

Assessment of Lung Recruitment by Electrical Impedance Tomography and Oxygenation in ARDS Patients

AbstractWe hypothesized that not all patients with appreciably recruited lung tissue during a recruitment maneuver (RM) show significant improvement of oxygenation. In the present study, we combined electrical impedance tomography (EIT) with oxygenation measurements to examine the discrepancies of lung ventilation and perfusion versus oxygenation after RM.A 2-minute RM (20 cm H2O positive end-expiratory pressure [PEEP] + 20 cm H2O pressure control) was prospectively conducted in 20 acute respiratory distress syndrome patients from January 2014 to December 2014. A decremental PEEP trial was performed to select the PEEP level after RM. A positive response to RM was identified as PaO2 + PaCO2 ≥400 mm Hg. Relative differences in the distribution of ventilation and perfusion in the most dependent region of interest (ROI4) were monitored with EIT and denoted as the ventilation-perfusion index.Ten patients were found to be responders and 10 patients to be nonresponders. No significant difference in baseline PaO2/FiO2 was observed between nonresponders and responders. A significantly higher PaO2/FiO2 ratio during RM and higher PEEP set after PEEP titration were recorded in responders. In both responders and nonresponders, the proportion of ventilation distributed in ROI4 compared with the global value was lower than the cardiac-related activity before RM, but this situation was reversed after RM (P < 0.01 in each group). Six out of 10 nonresponders exhibited a remarkable increase in ventilation in ROI4. A significant difference in the relative ventilation-perfusion index was found between the patients with remarkable and insufficient lung tissue reopening in the nonresponder group (P < 0.01).A discrepancy between lung tissue reopening and oxygenation improvement after RM was observed. EIT has the potential to evaluate the efficacy of RM by combining oxygenation measurements.

The relationship between arterial transducer level and pulse contour waveform-derived measurements

For hemodynamic monitoring, the pressure transducer is suggested to be fixed at the level of the phlebostatic axis in critically ill patients [1,2]. The correction and adjustment of pressure transducer are emphasized in central venous pressure monitoring in clinical practice. The exact position of the transducer is relatively easy to be ignored for invasive arterial blood pressure monitoring [3,4]. Improper position of the transducer may cause inaccurate value and shape of the arterial blood pressure wave, which would result in an invalid PiCCO (Pulsion Medical Systems AG, Munich, Germany) algorithm for pulse contour waveform-derived measurements. This study was conducted as a prospective quantitative evaluation of the relationship between arterial transducer level and pulse contour waveform-derived measurements. In total, 22 patients were enrolled in the 28-bed department of critical care medicine of a university hospital. All of the patients had a femoral artery catheter for PiCCO hemodynamic monitoring. The site of the phlebostatic axis was defined as the zero level (reference level). We moved the arterial pressure transducer up and down at eight different levels (� 5c m,�10 cm, �15 cm, �20 cm, 5 cm, 10 cm, 15 cm, 20 cm). At each level, continuous cardiac index (CCI), rate of left ventricular pressure rise during systole (dP/dtmax), and systemic vascular resistance index (SVRI) were simultaneously recorded.

Mind the influence of arterial oxygen tension on central venous oxygen saturation

No abstract