Pulse Pressure Variation Research Articles

Dynamic parameters for fluid responsiveness in mechanically ventilated children: A systematic review.

Fluid administration is the initial step of treatment of unstable pediatric patients. Evaluation of fluid responsiveness is crucial in mechanically ventilated children to avoid fluid overload, which increases mortality. We aim to review and compare the diagnostic performance of dynamically hemodynamic parameters for predicting fluid responsiveness in mechanically ventilated children. A systematic review was performed using four electronic databases, including PubMed, EMBASE, Scopus, and Central, for published articles from 1 January 2010 to 31 December 2020. Studies were included if they described diagnostic performance of dynamic parameters after fluid challenge was performed in mechanically ventilated children. Pediatric intensive and cardiac intensive care unit, and operative room. Children aged 1 month to 18 years old who were under mechanical ventilation and required an intravenous fluid challenge. Twenty-seven studies were included in the systematic review, which included 1,005 participants and 1,138 fluid challenges. Respiratory variation in aortic peak velocity was reliable among dynamic parameters for predicting fluid responsiveness in mechanically ventilated children. All studies of respiratory variation in aortic peak velocity showed that the area under the receiver operating characteristic curve ranged from 0.71 to 1.00, and the cutoff value for determining fluid responsiveness ranged from 7% to 20%. Dynamic parameters based on arterial blood pressure (pulse pressure variation and stroke volume variation) were also used in children undergoing congenital heart surgery. The plethysmography variability index was used in children undergoing neurological and general surgery, including the pediatric intensive care patients. The respiratory variation in aortic peak velocity exhibited a promising diagnostic performance across all populations in predicting fluid responsiveness in mechanically ventilated children. High sensitivity is advantageous in non-cardiac surgical patients and the pediatric intensive care unit because early fluid resuscitation improves survival in these patients. Furthermore, high specificity is beneficial in congenital heart surgery because fluid overload is particularly detrimental in this group of patients. https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=206400.

Research progress of goal-directed fluid therapy in prone position surgery.

Goal-directed fluid therapy (GDFT) is currently recognized as a scientific and reasonable method of perioperative capacity management. However, most of the studies on GDFT are carried out in the supine position, while there are few studies on applying GDFT in the prone position. This article introduces the target parameters of GDFT, the influence of prone position on target parameters, and the clinical application of GDFT in the prone position. Many studies have shown that the cut-off values of target parameters such as stroke volume variation (SVV) and pulse pressure variation (PPV) change in the prone position, but the ability to predict fluid responsiveness remains unchanged, which are still helpful indicators for guiding fluid therapy in the prone position. Although it is controversial whether the GDFT strategy can improve the clinical outcome of patients undergoing prone position surgery, it is still the mainstream choice of fluid therapy. In the future, we need to explore further the method of predicting the fluid responsiveness of patients in the prone position, improve the GDFT strategy, and guide the perioperative fluid therapy of patients in the prone position.

A new noninvasive finger sensor (NICCI system) for continuous blood pressure and pulse pressure variation monitoring: A method comparison study in patients having neurosurgery.

The NICCI system (Getinge, Gothenburg, Sweden) is a new noninvasive haemodynamic monitoring system using a finger sensor. We aimed to investigate the performance of the NICCI system to measure blood pressure and pulse pressure variation compared with intra-arterial measurements. A prospective method comparison study. University Medical Center Hamburg-Eppendorf, Hamburg, Germany. Forty-seven neurosurgery patients. We performed a method comparison study in 47 neurosurgery patients to compare NICCI blood pressure measurements (BP NICCI ) with intra-arterial blood pressure measurements (BP ART ) (Bland-Altman analysis, four-quadrant plot, error grid analysis) and NICCI pulse pressure variation measurements (PPV NICCI ) with pulse pressure variation calculated manually from the intra-arterial blood pressure waveform (PPV ART ) (Bland-Altman analysis, predictive agreement, Cohen's kappa). The mean of the differences ± standard deviation (95% limits of agreement) between BP NICCI and BP ART was 11 ± 10 mmHg (-8 to 30 mmHg) for mean blood pressure (MBP), 3 ± 12 mmHg (-21 to 26 mmHg) for systolic blood pressure (SBP) and 12 ± 10 mmHg (-8 to 31 mmHg) for diastolic blood pressure (DBP). In error grid analysis, 54% of BP NICCI and BP ART MBP measurement pairs were classified as 'no risk', 43% as 'low risk', 3% as 'moderate risk' and 0% as 'significant risk' or 'dangerous risk'. The mean of the differences between PPV NICCI and PPV ART was 1 ± 3% (-4 to 6%). The predictive agreement between PPV NICCI and PPV ART was 80% and Cohen's kappa was 0.55. The absolute agreement between BP NICCI and BP ART was not clinically acceptable. We recommend not using the current version of the NICCI system for blood pressure monitoring during surgery. The absolute agreement between PPV NICCI and PPV ART was clinically acceptable with moderate predictive agreement regarding pulse pressure variation categories. The NICCI system needs to be further developed and re-evaluated when an improved version is available. The study was registered in the German Clinical Trials Register (DRKS00023188) on 2 October 2020.

Corrected flow time and respirophasic variation in blood flow peak velocity of radial artery predict fluid responsiveness in gynecological surgical patients with mechanical ventilation

BackgroundRecent evidence suggests that ultrasound measurements of carotid and brachial artery corrected flow time (FTc) and respirophasic variation in blood flow peak velocity (ΔVpeak) are valuable for predicting fluid responsiveness in mechanical ventilated patients. We performed the study to reveal the performance of ultrasonic measurements of radial artery FTc and ΔVpeak for predicting fluid responsiveness in mechanical ventilated patients undergoing gynecological surgery.MethodsA total of eighty mechanical ventilated patients were enrolled. Radial artery FTc and ΔVpeak, and non-invasive pulse pressure variation (PPV) were measured before and after fluid challenge. Fluid responsiveness was defined as an increase in stroke volume index (SVI) of 15% or more after the fluid challenge. Multivariate logistic regression analyses and receiver operating characteristic (ROC) curve were used to screen multivariate predictors of fluid responsiveness and identify the predictive abilitie of non-invasive PPV, ΔVpeak and FTc on fluid responsiveness.ResultsForty-four (55%) patients were fluid responders. Multivariate logistic regression analysis showed that radial artery FTc, ΔVpeak, and non-invasive PPV were the independent predictors of fluid responsiveness, with odds ratios of 1.152 [95% confidence interval (CI) 1.045 to 1.270], 0.581 (95% CI 0.403 to 0.839), and 0.361 (95% CI, 0.193 to 0.676), respectively. The area under the ROC curve of fluid responsiveness predicted by FTC was 0.802 (95% CI, 0.706–0.898), and ΔVpeak was 0.812 (95% CI, 0.091–0.286), which were comparable with non-invasive PPV (0.846, 95%CI, 0.070–0.238). The optimal cut-off values of FTc for fluid responsiveness was 336.6 ms (sensitivity of 75.3%; specificity of 75.9%), ΔVpeak was 14.2% (sensitivity of 88.2%; specificity of 67.9%). The grey zone for FTc was 313.5–336.6 ms and included 40 (50%) of the patients, ΔVpeak was 12.2–16.5% and included 37(46%) of the patients.ConclusionsUltrasound measurement of radial artery FTc and ΔVpeak are the feasible and reliable methods for predicting fluid responsiveness in mechanically ventilated patients.Trial registrationThe trial was registered at the Chinese Clinical Trial Registry (ChiCTR)(www.chictr.org), registration number ChiCTR2000040941.

Dynamic changes of pulse pressure but not of pulse pressure variation during passive leg raising predict preload responsiveness in critically ill patients with spontaneous breathing activity

PurposeTo evaluate whether the changes in arterial pulse pressure (PP) and/or pulse pressure variation (PPV) during passive leg raising (PLR) can be used to evaluate preload responsiveness in patients with spontaneous breathing activity. Materials and methodsPatients ventilated with pressure support mode or totally spontaneously breathing were prospectively included. The values of PP and PPV were recorded before and at the end of PLR. The changes in cardiac index (CI) or the velocity-time integral (VTI) of the left ventricular outflow tract during PLR were tracked by the pulse contour analysis or transthoracic echocardiography. Patients exhibiting an increase in CI ≥ 10% or VTI ≥ 12% during PLR were defined as preload responders. ResultsAmong 33 patients included, 28 (80%) received norepinephrine and 14 were preload responders. The increase in PP > 2 mmHg in absolute value (4% in percentage) during PLR (PLRPP) predicted preload responsiveness with an area under the receiver operating characteristic (AUROC) of 0.76 ± 0.09 (p = 0.003 vs. AUROC of 0.5). The changes in PPV during PLR, however, failed to predict preload responsiveness (p = 0.82 vs. AUROC of 0.5). ConclusionIn patients with full spontaneous breathing activity, PLR-induced changes in PP had a fair ability to assess preload responsiveness even when norepinephrine was administered.Registration number:ClinicalTrials.gov (NCT04369027).

Reducing Risk for Acute Kidney Injury After Living Donor Hepatectomy by Protocolized Fluid Restriction: Single-Center Experience

BackgroundAcute kidney injury (AKI) is a potential complication after restricted fluid therapy for major surgery. The aim of this study was to evaluate the incidence of AKI for living liver donor hepatectomy in which applied intraoperative protocolized fluid restriction was used targeting a low central venous pressure (CVP) level with high pulse pressure variation (PPV) and systolic pressure variation (SPV). Material and MethodsLiving liver donors were admitted for this retrospective observational study. Low CVP <5 mm Hg with high PPV<20% and SPV<15% were the targets of the clinical protocol to reduce intraoperative blood loss via protocolized fluid management until the end of the hepatic parenchymal division. KDIGO criteria were used for AKI definition. The SPSS version 11.5 program was used for statistical analysis. ResultsThe study included 130 patients, 79 (60.8%) men and 51 (39.2%) women, with from 18 to 58 years of age. Donors underwent right and left lobe hepatectomies (116 and 14, respectively). The baseline CVP, the lowest CVP of hepatectomy, and the highest CVP measured after hepatectomy were 7.45 ± 2.41, 4.28 ± 1.12, 7.67 ± 2.09 mm Hg, respectively. Only 4 patients with right lobe hepatectomy developed AKI stage I (3.1%) in the first 24 hours. The 4 patients were recovered at 48 hours postoperatively. ConclusionThis study demonstrated that a CVP target of <5 mm Hg and high PPV/SPV via a simple fluid management modality with protocolized-fluid restriction until the procurement may not cause AKI in living liver donors in a closed follow-up anesthesia approach.

A Pilot Study Assessing a Closed-Loop System for Goal-Directed Fluid Therapy in Abdominal Surgery Patients.

Background: This prospective multicentre pilot study of patients scheduled for elective major abdominal surgery aimed to validate the fluid challenge (FC) proposed by the closed-loop (CL) system via anaesthesiologist assessment. Methods: This was a phase II trial consisting of two inclusion stages (SIMON method). Each FC (250 mL saline solution for 10 min) proposed by the CL was systematically validated by the anaesthesiologist who could either confirm or refuse the FC or give FC without the CL system. A ≥ 95% agreement between the CL and the anaesthesiologist was considered acceptable. Results: The study was interrupted after interim analysis of the first 19 patients (10 men, median age = 61 years, median body mass index = 26 kg/m2). The anaesthesiologists accepted 165/205 (80%) of fluid boluses proposed by the CL. Median cardiac index (CI) was 2.9 (interquartile: IQ (2.7; 3.4) L/min/m2) and the median coefficient of variation (CV) for CI was 13% (10; 17). Fifteen out of nineteen patients (79%) had a mean CI > 2.5 L/min/m2 or spent > 85% surgery time with pulse pressure variation < 13%. No adverse events related to the CL were reported. Conclusion: In this study of patients scheduled for elective major abdominal surgery, the agreement between CL and anaesthesiologist for giving fluid challenge was 80%, suggesting that CL cannot replace the physician but could help in decision making.

Variations of pulse pressure and central venous pressure may predict fluid responsiveness in mechanically ventilated patients during lung recruitment manoeuvre: an ancillary study

BackgroundMaintaining a constant driving pressure during a prolonged sigh breath lung recruitment manoeuvre (LRM) from 20 to 45 cmH20 peak inspiratory pressure in mechanically ventilated patients has been shown to be a functional test to predict fluid responsiveness (FR) when using a linear regression model of hemodynamic parameters, such as central venous pressure (CVP) and pulse pressure (PP). However, two important limitations have been raised, the use of high ventilation pressures and a regression slope calculation that is difficult to apply at bedside. This ancillary study aimed to reanalyse absolute variations of CVP (ΔCVP) and PP (ΔPP) values at lower stages of the LRM, (40, 35, and 30 cm H20 of peak inspiratory pressure) for their ability to predict fluid responsiveness.MethodsRetrospective analysis of a prospective study data set in 18 mechanically ventilated patients, in an intensive care unit. CVP, systemic arterial pressure parameters and stroke volume (SV) were recorded during prolonged LRM followed by a 500 mL crystalloid volume expansion. Patients were considered as fluid responders if SV increased more than 10%. Receiver-operating curves (ROC) analysis with the corresponding grey zone approach were performed.ResultsAreas under the ROC to predict fluid responsiveness for ΔCVP and ΔPP were not different between the successive stepwise increase of inspiratory pressures [0.88 and 0.89 for ΔCVP at 45 and 30 cm H20 (P = 0.89), respectively, and 0.92 and 0.95 for ΔPP at 45 and 30 cm H20, respectively (P = 0.51)]. Using a maximum of 30 cmH2O inspiratory pressure during the LRM, ΔCVP and ΔPP had a threshold value to predict fluid responsiveness of 2 mmHg and 4 mmHg, with sensitivities of 89% and 89% and specificities of 67% and 89%, respectively. Combining ΔPP and ΔCVP decreased the proportion of the patients in the grey zone from 28 to 11% and showed a sensitivity of 88% and a specificity of 83%.ConclusionsA stepwise PEEP elevation recruitment manoeuvre of up to 30 cm H20 may predict fluid responsiveness as well as 45 cm H20. The combination of ΔPP and ΔCVP optimizes the categorization of responder and non-responder patients.

Femoral Pulse Pressure Variation Is Not Interchangeable with Radial Pulse Pressure Variation during Living Donor Liver Transplantation.

The radial artery is commonly used as the site measuring pulse pressure variation (PPV) during surgery. Accurate measurement of circulating blood volume and timely interventions to maintain optimal circulating blood volume is important to deliver sufficient oxygen to tissues and organs. It has not rather than never studied in patients undergoing liver transplantation whether PPV measured at peripheral sites, such as the radial artery, do represent central PPV for evaluating blood volume. In this retrospective study, 51 liver transplant recipients were enrolled. The two PPVs had been automatically recorded every minute in electrical medical records. A total 1878 pairs of the two PPVs were collected. The interchangeability of PPV measured at the radial and the femoral artery was analyzed by using the Bland–Altman plot, four-quadrant plot, Cohen’s kappa (k), and receiver operating curve. The bias and limits of agreement of the two PPVs were −1.3% and −8.8% to 6.2%, respectively. The percentage error was 75%. The concordance rate was 65%. The Kappa of PPV-radial determining whether PPV-femoral was >13% or ≤13% was 0.64. We found that PPV-radial is not interchangeable with PPV-femoral during liver transplantation. Additionally, PPV-radial failed to reliably track changes of PPV-femoral. Lastly, the clinical decision regarding blood volume status (depletion or not) is significantly different between the two PPVs. Therefore, PPV-femoral may help maintain blood volume circulating to major organs including the newly transplanted liver graft for liver transplant recipients.

Respiratory variation of central vein diameter in upper body as a surrogate of pulse pressure variation

Background: Cyclical change in central vein diameter during respiratory cycle can be used for fluid-responsiveness assessment. The purpose of this study is to assess variations in the diameter of central veins in upper body region, specifically internal jugular vein (IJV), subclavian vein (SCV), and brachiocephalic vein (BCV), in mechanically ventilated patients. We hypothesized that variations in the diameter of these veins caused by passive ventilation would be strongly concordant with pulse pressure variation (PPV). Methods: The study was conducted in mechanically ventilated, critically ill surgical and medical patients. The PPV values were automatically calculated and were recorded. The diameters of the study veins such as the IJV, SCV, and BCV were measured bedside using the ultrasound. Then respiratory variations of venous diameter were calculated into distensibility index, collapsibility index and variability index. The relationships between PPV and ultrasound-derived parameters were assessed. Patients were separated into two groups according to their PPV values (&gt;13 and &lt;10). The test performance and proper cut-off values of ultrasound-derived parameters to distinguish between these two groups were generated by receiver operating characteristic (ROC) curves. Results: A total of 44 patients were assessed. There were substantial correlations between PPV and ultrasound parameter namely IJV-DI (r=0.652, p&lt;0.001), IJV-VI (r=0.655, p&lt;0.001), SCV-CI (r=0.618, p&lt;0.001), and SCV-VI (r=0.626, p&lt;0.001). While PPV and BCV-CI show moderate correlation (r=0.531, p=0.008). The IJV-DI, IJV-VI, SCV-CI, SCV-VI and BCV-VI values were significantly greater in PPV&gt;13 group than PPV&lt;10 group. All these parameters were effective in distinguishing between PPV&gt;13 from PPV&lt;10 group with AUC 0.983, 0.983, 0.928, 0.928 and 0.826, respectively. The IJV-DI, IJV-VI, SCV-CI, SCV-VI and BCV-VI analysis demonstrated appropriate cut-off values for separating patients with PPV&gt;13 from those with PPV&lt;10 as 16.19% (sensitivity 92%, specificity 96%), 14.98 % (sensitivity 92%, specificity 96%), 9.74% (sensitivity of 93%, specificity of 91%), 12.33% (sensitivity of 87%, specificity of 100%) and 13.71% (sensitivity of 73%, specificity of 100%), respectively. Conclusions: In critically ill patients, all ultrasound-derived measures such as IJV-DI, IJV-VI, SCV-CI, SCV-VI, and BCV-VI revealed significant correlation with PPV value.

Tidal volume challenge to predict preload responsiveness in patients with acute respiratory distress syndrome under prone position

BackgroundProne position is frequently used in patients with acute respiratory distress syndrome (ARDS), especially during the Coronavirus disease 2019 pandemic. Our study investigated the ability of pulse pressure variation (PPV) and its changes during a tidal volume challenge (TVC) to assess preload responsiveness in ARDS patients under prone position.MethodsThis was a prospective study conducted in a 25-bed intensive care unit at a university hospital. We included patients with ARDS under prone position, ventilated with 6 mL/kg tidal volume and monitored by a transpulmonary thermodilution device. We measured PPV and its changes during a TVC (ΔPPV TVC6–8) after increasing the tidal volume from 6 to 8 mL/kg for one minute. Changes in cardiac index (CI) during a Trendelenburg maneuver (ΔCITREND) and during end-expiratory occlusion (EEO) at 8 mL/kg tidal volume (ΔCI EEO8) were recorded. Preload responsiveness was defined by both ΔCITREND ≥ 8% and ΔCI EEO8 ≥ 5%. Preload unresponsiveness was defined by both ΔCITREND < 8% and ΔCI EEO8 < 5%.ResultsEighty-four sets of measurements were analyzed in 58 patients. Before prone positioning, the ratio of partial pressure of arterial oxygen to fraction of inspired oxygen was 104 ± 27 mmHg. At the inclusion time, patients were under prone position for 11 (2–14) hours. Norepinephrine was administered in 83% of cases with a dose of 0.25 (0.15–0.42) µg/kg/min. The positive end-expiratory pressure was 14 (11–16) cmH2O. The driving pressure was 12 (10–17) cmH2O, and the respiratory system compliance was 32 (22–40) mL/cmH2O. Preload responsiveness was detected in 42 cases. An absolute change in PPV ≥ 3.5% during a TVC assessed preload responsiveness with an area under the receiver operating characteristics (AUROC) curve of 0.94 ± 0.03 (sensitivity: 98%, specificity: 86%) better than that of baseline PPV (0.85 ± 0.05; p = 0.047). In the 56 cases where baseline PPV was inconclusive (≥ 4% and < 11%), ΔPPV TVC6–8 ≥ 3.5% still enabled to reliably assess preload responsiveness (AUROC: 0.91 ± 0.05, sensitivity: 97%, specificity: 81%; p < 0.01 vs. baseline PPV).ConclusionIn patients with ARDS under low tidal volume ventilation during prone position, the changes in PPV during a TVC can reliably assess preload responsiveness without the need for cardiac output measurements.Trial registration: ClinicalTrials.gov (NCT04457739). Registered 30 June 2020 —Retrospectively registered, https://clinicaltrials.gov/ct2/show/record/NCT04457739

Passive leg raising-induced changes in pulse pressure variation to assess fluid responsiveness in mechanically ventilated patients: a multicentre prospective observational study

BackgroundPassive leg raising-induced changes in cardiac index can be used to predict fluid responsiveness. We investigated whether passive leg raising-induced changes in pulse pressure variation (ΔPPVPLR) can also predict fluid responsiveness in mechanically ventilated patients. MethodsIn this multicentre prospective observational study, we included 270 critically ill patients on mechanical ventilation in whom volume expansion was indicated because of acute circulatory failure. We did not include patients with cardiac arrythmias. Cardiac index and PPV were measured before/during a passive leg raising test and before/after volume expansion. A volume expansion-induced increase in cardiac index of >15% defined fluid responsiveness. To investigate whether ΔPPVPLR can predict fluid responsiveness, we determined areas under the receiver operating characteristic curves (AUROCs) and grey zones for relative and absolute ΔPPVPLR. ResultsOf the 270 patients, 238 (88%) were on controlled mechanical ventilation with no spontaneous breathing activity and 32 (12%) were on pressure support ventilation. The median tidal volume was 7.1 (inter-quartile range [IQR], 6.6–7.6) ml kg−1 ideal body weight. One hundred sixty-four patients (61%) were fluid responders. Relative and absolute ΔPPVPLR predicted fluid responsiveness with an AUROC of 0.92 (95% confidence interval [95% CI], 0.88–0.95; P<0.001) each. The grey zone for relative and absolute ΔPPVPLR included 4.8% and 22.6% of patients, respectively. These results were not affected by ventilatory mode and baseline characteristics (type of shock, centre, vasoactive treatment). ConclusionsPassive leg raising-induced changes in pulse pressure variation accurately predict fluid responsiveness with a small grey zone in critically ill patients on mechanical ventilation. Clinical trial registrationNCT 03225378.

Effect of alveolar recruitment maneuver on pulse pressure variation: a case report

Effect of alveolar recruitment maneuver on pulse pressure variation: a case report

The Potential of Arterial Pulse Wave Analysis in Burn Resuscitation: A Pilot In Vivo Study.

While urinary output (UOP) remains the primary endpoint for titration of intravenous fluid resuscitation, it is an insufficient indicator of fluid responsiveness. Although advanced hemodynamic monitoring (including arterial pulse wave analysis [PWA]) is of recent interest, the validity of PWA-derived indices in burn resuscitation extremes has not been established. The goal of this paper is to test the hypothesis that PWA-derived cardiac output (CO) and stroke volume (SV) indices as well as pulse pressure variation (PPV) and systolic pressure variation (SPV) can play a complementary role to UOP in burn resuscitation. Swine were instrumented with a Swan-Ganz catheter for reference CO and underwent a 40% TBSA burns with varying resuscitation paradigms, and were monitored for 24 hours in an ICU setting under mechanical ventilation. The longitudinal changes in PWA-derived indices were investigated, and resuscitation adequacy was compared as determined by UOP vs PWA indices. The results indicated that PWA-derived indices exhibited trends consistent with reference CO and SV measurements: CO and SV indices were proportional to reference CO and SV, respectively (CO: postcalibration limits of agreement [LoA] = ±24.7 [ml/min/kg], SV: postcalibration LoA = ±0.30 [ml/kg]) while PPV and SPV were inversely proportional to reference SV (PPV: postcalibration LoA = ±0.32 [ml/kg], SPV: postcalibration LoA = ±0.31 [ml/kg]). The results also indicated that PWA-derived indices exhibited notable discrepancies from UOP in determining adequate burn resuscitation. Hence, it was concluded that the PWA-derived indices may have complementary value to UOP in assessing and guiding burn resuscitation.

Effect of norepinephrine on blood volume, cardiac output, and systemic filling pressure in patients undergoing liver transplantation

Patients with liver cirrhosis develop symptoms comparable to those of patients with sepsis, who have increased total vascular compliance, which may cause blood pooling in the venous pool. No previous studies have evaluated the effect of using norepinephrine on the intravascular blood volume. We investigated the norepinephrine infusion's effect on the mean systemic filling pressure, venous return, and cardiac preload in patients undergoing liver transplantation. Overall, 33 patients who underwent living donor liver transplantation were included in this study. Cardiac output (CO) was measured using a PiCCO device (Pulsion Medical Systems, Munich, Germany). The mean systemic filling pressure was calculated using the inspiratory hold maneuver at four time intervals - at baseline, 10 min after the norepinephrine infusion, 5 min after norepinephrine discontinuation, and after infusion of 500 cc of 5% albumin. Other hemodynamic parameters, including the mean arterial pressure (MAP), pulse pressure variation, stroke volume variation, global end-diastolic volume, and mitral inflow velocity (E wave), were also evaluated. The norepinephrine infusion increased MAP and systemic vascular resistance in all patients. Moreover, it increased CO, mean systemic filling pressure, and global end-diastolic volume in 20 patients (60%), whereas there were no changes in these variables in 13 patients (40%). In all patients, norepinephrine infusion discontinuation caused a significant decrease in MAP, CO, resistance to venous return, and mean systemic filling pressure. Infusion of 500 cc colloid increased CO; however, interestingly, it was associated with a significant decrease in systemic vascular resistance; hence, MAP and mean systemic filling pressure showed no changes. The norepinephrine infusion at 0.1 µg-1 kg-1 min-1 was associated with an increase in CO in patients with liver cirrhosis undergoing liver transplantation. Norepinephrine's effect on CO was primarily attributable to an increase in venous return due to an increase in mean systemic filling pressure.

Assessing Hemorrhagic Shock Severity Using the Second Heart Sound Determined from Phonocardiogram: A Novel Approach.

Introduction: Hemorrhagic shock (HS) is a severe medical emergency. Early diagnosis of HS is important for clinical treatment. In this paper, we report a flexible material-based heart sound monitoring device which can evaluate the degree of HS through a phonocardiogram (PCG) change. Methods: Progressive hemorrhage treatments (H1, H2, and H3 stage) were used in swine to build animal models. The PCG sensor was mounted on the chest of the swine. Routine monitoring was used at the same time. Results: This study showed that arterial blood pressure decreased significantly from the H1 phase, while second heart sound amplitude (S2A) and energy (S2E) decreased significantly from the H2 phase. Both S2A and S2E correlated well with BP (p < 0.001). The heart rate, pulse pressure variation and serum hemoglobin level significantly changed in the H3 stage (p < 0.05). Discussion: The change of second heart sound (S2) was at the H2 stage and was earlier than routine monitoring methods. Therefore, PCG change may be a new indicator for the early detection of HS severity.

Using generalized additive models to decompose time series and waveforms, and dissect heart–lung interaction physiology

Common physiological time series and waveforms are composed of repeating cardiac and respiratory cycles. Often, the cardiac effect is the primary interest, but for, e.g., fluid responsiveness prediction, the respiratory effect on arterial blood pressure also convey important information. In either case, it is relevant to disentangle the two effects. Generalized additive models (GAMs) allow estimating the effect of predictors as nonlinear, smooth functions. These smooth functions can represent the cardiac and respiratory cycles’ effects on a physiological signal. We demonstrate how GAMs allow a decomposition of physiological signals from mechanically ventilated subjects into separate effects of the cardiac and respiratory cycles. Two examples are presented. The first is a model of the respiratory variation in pulse pressure. The second demonstrates how a central venous pressure waveform can be decomposed into a cardiac effect, a respiratory effect and the interaction between the two cycles. Generalized additive models provide an intuitive and flexible approach to modelling the repeating, smooth, patterns common in medical monitoring data.

Influence of intraoperative fluid replacement on ampicillin serum levels and surgical site infections

BackgroundSurgical site infections (SSI) occur despite antimicrobial prophylaxis and increase postoperative morbidity and mortality. This could be caused by an intraoperative decrease in antibiotic serum concentrations such as ampicillin after major abdominal surgery due to blood loss and fluid therapy, which possibly promotes SSI. This hypothesis was tested in the present study. MethodsThis pilot study was performed as a prospective observational trial between March 2018 and May 2019. Ampicillin/sulbactam was administered intravenously during anesthesia induction. Fluid replacement was guided based on hemodynamic variables, including analysis of pulse pressure variation. The primary outcome was ampicillin serum level (ASL), measured after administration and hourly within 4 hours. The incidence of SSI at hospital discharge was the secondary outcome. Linear mixed and logistic regression models were used for statistical analyses. ResultsAfter screening of 133 adult patients, 129 were enrolled, and 102 completed the study protocol. No correlation was found between the volume of intraoperative fluids and ASL, nor was any association found between ASL and SSI. Based on 5 SSI cases, SSI were associated with higher intraoperative fluid volume. ASL was sufficient to provide intraoperative coverage for all potential bacterial strains. ConclusionIntraoperative fluid replacement had no effect on ASL up to 4 hours after ampicillin/sulbactam administration. SSI were within an acceptable range, indicating adequate antimicrobial prophylaxis, so intraoperative control of ASL does not seem necessary. In conclusion, contrary to our initial hypothesis, ASL is not influenced by volume turnover or blood loss during major surgery and therefore does not affect SSI.

Efficacy of using tidal volume challenge to improve the reliability of pulse pressure variation reduced in low tidal volume ventilated critically ill patients with decreased respiratory system compliance

BackgroundThe prediction accuracy of pulse pressure variation (PPV) for fluid responsiveness was proposed to be unreliable in low tidal volume (Vt) ventilation. It was suggested that changes in PPV obtained by transiently increasing Vt to 8 ml/kg accurately predicted fluid responsiveness even in subjects receiving low Vt. We assessed whether the changes in PPV induced by a Vt challenge predicted fluid responsiveness in our critically ill subjects ventilated with low Vt 6 ml/kg.MethodsThis study is a prospective single-center study. PPV and other parameters were measured at a Vt of 6 mL/kg, 8 mL/kg, and after volume expansion. The prediction accuracy of PPV and other parameters for fluid responsiveness before and after tidal volume challenge was also analyzed using receiver operating characteristic (ROC) curves.ResultsThirty-one of the 76 subjects enrolled in the study were responders (41%). Respiratory system compliance of all subjects decreased significantly (26 ± 4.3). The PPV values were significantly higher in the responder group than the non-responder group before (8.8 ± 2.7 vs 6.8 ± 3.1) or after (13.0 ± 1.7 vs 8.5 ± 3.0) Vt challenge. In the receiver operating characteristic curve (ROC) analysis, PPV6 showed unsatisfactory predictive capability with an area under the curve (AUC) of 0.69 (95%CI, 0.57–0.79, p = 0.002) at a Vt of 6 mL/kg. PPV8 andΔPPV6–8 showed good predictive capability with an AUC of 0.90 (95% CI, 0.81–0.96, p < 0.001) and 0.90 (95% CI, 0.80–0.95, P < 0.001) respectively. The corresponding cutoff values were 11% for PPV8 and 2% for ΔPPV6–8.ConclusionsPPV shows a poor operative performance as a predictor of fluid responsiveness in critically ill subjects ventilated with a tidal volume of 6 mL/ kg. Vt challenge could improve the predictive accuracy of PPV to a good but not excellent extent when respiratory system compliance decreased significantly.

Specifics of daily blood pressure monitoring in patients with systemic hypertension and obstructive sleep apnoea: a case-control study

Background. The comorbidity of arterial hypertension (AH) and obstructive sleep apnea syndrome (OSA) is becoming increasingly common in clinical practice. However, the priority strategy for selecting antihypertensive therapy in such patients is yet to be defined. 24-hour blood pressure monitoring is important for determining an approach to controlling hypertension.Objectives. To study specific features of 24-hour blood pressure monitoring in comorbid AH– OSA patients.Methods. A total of 130 AH patients were surveyed. The main cohort (1) included AH–OSA patients (n = 90, mean age 54.93 ± 1.04 years), control cohort (2) — non-OSA AH patients (n = 40, mean age 57.92 ± 1.29 years). All patients had a general clinical examination with 24-hour blood pressure monitoring. OSA was verified in overnight respiratory polygraphy using an Alice PDx diagnostic appliance (USA).Results. The following specific features of 24-hour blood pressure monitoring were identified in the comorbid patients: a statistically significant growth of mean 24-hour systolic and average BP, as well as mean nocturnal systolic, diastolic and average BP; a statistically significant growth of mean 24-hour systolic, diastolic and average BP load indices. In addition, the AH-OSA patients had the statistically higher pulse pressure, systolic and average BP variability, as well as morning BP surge rate. The 24-hour BP dynamics in OSA patients had predominant morbid profiles and higher non-dipper and night-peaker rates compared to the control cohort.Conclusion. The identified specific features reflect a high risk of adverse cardiovascular events in AH–OSA comorbid patients, an earlier damage of target organs and negative prognosis of comorbidity, which warrants a further analysis of AH-specific clinical picture and personalisation of blood pressure control measures in such patients.