Oliver Hunsicker

Oesophageal Doppler and calibrated pulse contour analysis are not interchangeable within a goal-directed haemodynamic algorithm in major gynaecological surgery

BACKGROUND Evidence for the benefit of an intraoperative use of a goal-directed haemodynamic management has grown. We compared the oesophageal Doppler monitor (ODM, CardioQ-ODM™) with a calibrated pulse contour analysis (PCA, PiCCO2™) with regard to assessment of stroke volume (SV) changes after volume administration within a goal-directed haemodynamic algorithm during non-cardiac surgery. METHODS The data were obtained prospectively in patients with metastatic ovarian carcinoma undergoing cytoreductive surgery. During surgery, fluid challenges were performed as indicated by the goal-directed haemodynamic algorithm guided by the ODM. Monitors were compared regarding precision and trending. Clinical characteristics associated with trending were studied by extended regression analysis. RESULTS A total of 762 fluid challenges were performed in 41 patients resulting in 1524 paired measurements. The precision of ODM and PCA was 5.7% and 6.0% (P=0.80), respectively. Polar plot analysis revealed a poor trending between ODM and PCA with an angular bias of -7.1°, radial limits of agreement of -58.1° to 43.8°, and an angular concordance rate of 67.8%. Dose of norepinephrine (NE) (scaled 0.1 µg kg(-1) min(-1)) [adjusted odds ratio (OR) 0.606 (95% confidence interval, CI: 0.404-0.910); P=0.016] and changes in mean arterial pressure (MAP) to a fluid challenge (scaled 10%) [adjusted OR 0.733 (95% CI: 0.635-0.845); P<0.001] were associated with trending between ODM and PCA, whereas there was no relation to type of i.v. solution. CONCLUSIONS Despite a similar precision, ODM and PCA were not interchangeable with regard to measuring SV changes within a goal-directed haemodynamic algorithm. A decrease in interchangeability coincided with increasing NE levels and greater changes of MAP to a fluid challenge.

Assessment of agreement and trending between haemodynamic monitors is still challenging

Dear Editor, We read with interest the article by Petzoldt et al. [1] who evaluated agreement and trending between three less invasive methods and transoesophageal echocardiography (TEE) in terms of stroke volume in patients with aortic valve dysfunctions. The authors found a coefficient of error (CE) of 3.6 ± 3.0 % for their reference method TEE, resulting in a precision of 7.2 % (2 9 CE). Bland– Altman analysis revealed percentage errors (PE) for the transpulmonary thermodilution (TPTD) of 14.9 % in the TPTD as a valid method in severe PE’s of 26.3 and 26.2 % in aortic stenosis and insufficiency, respectively. The authors concluded that there was a tolerable agreement between TEE and TPTD as the PE fell in a range of ±30 % [2] and therefore stated that the TPTD is a valid method in severe aortic stenosis (AS) and valvulopasty-induced aortic insufficiency (AI). The benchmark at ±30 % (±28.3 % to be more precise) refers to the assumption that intermittent thermodilution (ITD) by the pulmonary artery catheter has a precision of ±20 % and means that if PE lies within a range of ±30 %, methods are interchangeable with ITD as they show a comparable individual error. In this study, TEE showed a superior precision (7.2 %) than ITD and, consequently, redetermining the range of an acceptable PE could be considered [3]. Claiming the new methods to have at least the same individual error as the TEE would result in an acceptable PE of ±10.2 %. Applying this cut-off to the data, none of the three less-invasive techniques would be valid in comparison with the reference method TEE in terms of normal prosthetic valve function, as well as in AS and valvulopasty-induced AI. Petzoldt and colleagues also evaluated trending of the less-invasive methods in comparison to TEE using the polar plot analysis [4]. In this analysis, paired data of the changes displayed by the monitors are converted to polar coordinates where agreement is shown by the angle with the polar axis (0 or 180 , respectively) and the magnitude of the change in stroke volume by the distance from the origin. To analyse and visualize good and acceptable trending, Petzoldt et al. [1] additionally drew horizontal lines at ±10 and ±20 % of the change of stroke volume within the polar plot and calculated the percentage of values lying within the horizontal 10 % limits. This analytical approach revealed a high percentage of values lying within these predefined limits for all three less-invasive methods (72–100 %) in comparison with TEE. This result led the authors to conclude that all of the test methods showed an acceptable ability to detect changes in stroke volume in patients with aortic valve dysfunction. Most strikingly, their polar plot analysis between TEE and TPTD in AS on the one side and between TEE and uncalibrated pulse contour analysis in AI on the other side showed the same percentage rate of 89 %, suggesting a comparable acceptable trending ability of both methods. As the polar plot analysis is based on the conversion of the haemodynamic change to a radial vector, we would like to raise the issue if a horizontal line for the limits of agreement might be appropriate.

Duration of storage influences the hemoglobin rising effect of red blood cells in patients undergoing major abdominal surgery: EFFICACY OF SENESCENT RBCs DURING SURGERY

After transfusion of senescent red blood cells (RBCs) a considerable fraction is rapidly cleared from the recipients’ circulation. Thus, transfusion of senescent RBCs may be less effective in terms of increasing hemoglobin concentration (cHb) after transfusion.

Diagnostic value of plasma NGAL and intraoperative diuresis for AKI after major gynecological surgery in patients treated within an intraoperative goal-directed hemodynamic algorithm: A substudy of a randomized controlled trial

Abstract Data on early markers for acute kidney injury (AKI) after noncardiovascular surgery are still limited. This study aimed to determine the diagnostic value of plasma neutrophil-gelatinase-associated lipocalin (pNGAL) and intraoperative diuresis for AKI in patients undergoing major abdominal surgery treated within a goal-directed hemodynamic algorithm. This study is a post-hoc analysis of a randomized controlled pilot trial comparing intravenous solutions within a hemodynamic goal-directed algorithm based on the esophageal Doppler in patients undergoing epithelial ovarian cancer surgery. The diagnostic value of plasma NGAL obtained at ICU admission and intraoperative diuresis was determined with respect to patients already meeting AKI criteria 6 hours after surgery (AKI6h) and to all patients meeting AKI criteria at least once during the postoperative course (AKItotal). AKI was diagnosed by the definition of the Kidney Disease Improving Global Outcome (KDIGO) group creatinine criteria and was screened up to postoperative day 3. Receiver operating characteristic curves including a gray zone approach were performed. A total of 48 patients were analyzed. None of the patients had increased creatinine levels before surgery and 14 patients (29.2%) developed AKI after surgery. Plasma NGAL was predictive for AKI6h (AUCAKI6h 0.832 (95% confidence interval [CI], 0.629–0.976), P = .001) and AKItotal (AUCAKItotal 0.710 (CI 0.511–0.878), P = .023). The gray zones of pNGAL calculated for AKI6h and AKItotal were 210 to 245 and 207 to 274 ng mL−1, respectively. The lower cutoffs of the gray zone at 207 and 210 ng mL−1 had a negative predictive value (NPV) (i.e., no AKI during the postoperative course) of 96.8% (CI 90–100) and 87.1% (CI 78–97), respectively. Intraoperative diuresis was also predictive for AKI6h (AUCAKI6h 0.742 (CI 0.581–0.871), P = .019) with a gray zone of 0.5 to 2.0 mL kg−1 h−1. At the lower cutoff of the gray zone at 0.5 mL kg−1 h−1, corresponding to the oliguric threshold, the NPV was 84.2% (78–92). This study indicates that pNGAL can be used as an early marker to rule out AKI occurring within 3 days after major abdominal surgery. Intraoperative diuresis can be used to rule out AKI occurring up to 6 hours after surgery. Trial Registration: ISRCTN 53154834.

Correlation of arterial blood pressure to synchronous piezo, impedance and photoplethysmographic signal features

Abstract In this paper we investigate which pulse wave pick-up technologies are well suited for blood pressure trend estimation. We use custom built hardware to acquire electrocardiographic, applanation-tonometric, photo- and impedance-plethysmographic signals during low intensity workouts. Beat-to-beat features and pulse wave runtimes are correlated to the reference arterial blood pressure. Temporal lag adjustment is performed to determine the latency of feature response. Best results are obtained for systolic arterial blood pressure. These suggest that every subject has a range of well-performing features, but it is not consistent among all. Spearman Rho values reach in excess of 0.8, with their significance being validated by p-values lower than 0.01.

In-ear photoplethysmography for central pulse waveform analysis in non-invasive hemodynamic monitoring

Abstract In recent years, the analysis of the photoplethys-mographic (PPG) pulse waveforms has attracted much research focus. However, the considered signals are primarily recorded at the fingertips, which suffer from reduced peripheral perfusion in situations like hypovolemia or sepsis, rendering waveform analysis infeasible. The ear canal is not affected by cardiovascular centralization and could thus prove to be an ideal alternate measurement site for pulse waveform analysis. Therefore, we developed a novel system that allows for highly accurate photoplethysmographic measurements in the ear canal. We conducted a measurement study in order to assess the signal-to-noise ratio of our developed system Hereby, we achieved a mean SNR of 40.65 dB. Hence, we could show that our system allows for highly accurate PPG recordings in the ear canal facilitating sophisticated pulse waveform analysis. Furthermore, we demonstrated that the pulse decomposition analysis is also applicable to in-ear PPG recordings.

Classification of morphologic changes in photoplethysmographic waveforms

Abstract An ever increasing number of research is examining the question to what extent physiological information beyond the blood oxygen saturation could be drawn from the photoplethysmogram. One important approach to elicit that information from the photoplethysmogram is the analysis of its waveform. One prominent example for the value of photoplethysmographic waveform analysis in cardiovascular monitoring that has emerged is hemodynamic compensation assessment in the peri-operative setting or trauma situations, as digital pulse waveform dynamically changes with alterations in vascular tone or pulse wave velocity. In this work, we present an algorithm based on modern machine learning techniques that automatically finds individual digital volume pulses in photoplethysmographic signals and sorts them into one of the pulse classes defined by Dawber et al. We evaluate our approach based on two major datasets – a measurement study that we conducted ourselves as well as data from the PhysioNet MIMIC II database. As the results are satisfying we could demonstrate the capabilities of classification algorithms in the automated assessment of the digital volume pulse waveform measured by photoplethysmographic devices.

Association of Sodium Homeostasis with Blood Transfusions During Liver Transplantation.

To the Editor We read with interest the article by Hudcova et al.1 who retrospectively investigated the relation of intraoperative serum sodium changes (∆Na) with anesthesia management and short-term postoperative outcomes in patients undergoing liver transplantation. They observed that the increase of sodium was significantly related to the amount of red blood cells (RBCs) and fresh frozen plasma (FFP) transfused during surgery. Liver transplantation often requires the need for frequent blood transfusion. Although data on the impact of RBC and FFP administration on electrolytes are limited, the correlation of increasing sodium levels with RBC administration stands in contrast to available data on sodium content of packed RBCs. It has been consistently shown that sodium concentration in RBC units decreases steadily during storage, resulting in a sodium concentration of approximately 120 to 125 mmol L−1 after 14 days.2,3 One of the contributing mechanisms to the decrease in sodium concentration in RBCs during storage is an inoperative membrane sodium–potassium pump at the storage temperature of 4°C, and subsequently potassium and sodium ions equilibrate through the semipermeable cell membrane.4,5 In this context, it takes up to 24 hours to restore the physiologic intracellular and extracellular sodium concentrations of RBC after transfusion.5,6 In contrast, FFP has been shown to contain an unphysiologic high sodium concentration with up to 172 ± 7 mmol L−1 because of the added preservative solution containing a high load of sodium citrate.7 In this context, from a rational view and in case of a causal relationship, transfusion of FFP might be a more important determinant to the observed increase in sodium in the study by Hudcova et al. than transfusion of RBCs. The contrasting findings by Hudcova et al. might be due to the study design comparing only preoperative and postoperative sodium values disregarding the relationship of ∆Na with the variables of interest at different time points during surgery. Furthermore, according to their article, it is unknown whether the classical Spearman rank correlation coefficient without extension or with partial rank correlation was used to assess the relationship of ∆Na with the variables of interest. The latter would have allowed removing the effect of other contributing variables. In our opinion, the association of ∆Na with RBCs and FFP during surgery can only be assessed appropriately if multiple blood gas samples are obtained during the course of surgery and regression analysis for longitudinal data with adjustment for multiple measurements per patient is performed.

Haemodynamic Optimization by Oesophageal Doppler and Pulse Power Wave Analysis in Liver Surgery: A Randomised Controlled Trial

Liver surgery is still associated with a high rate of morbidity and mortality. We aimed to compare different haemodynamic treatments in liver surgery. In a prospective, blinded, randomised, controlled pilot trial patients undergoing liver resection were randomised to receive haemodynamic management guided by conventional haemodynamic parameters or by oesophageal Doppler monitor (ODM, CardioQ-ODM) or by pulse power wave analysis (PPA, LiDCOrapid) within a goal-directed algorithm adapted for liver surgery. The primary endpoint was stroke volume index before intra-operative start of liver resection. Secondary endpoints were the haemodynamic course during surgery and postoperative pain levels. Due to an unbalance in the extension of the surgical procedures with a high rate of only minor procedures the conventional group was dropped from the analysis. Eleven patients in the ODM group and 10 patients in the PPA group were eligible for statistical analysis. Stroke volume index before start of liver resection was 49 (37; 53) ml/m2 and 48 (41; 56) ml/m2 in the ODM and PPA group, respectively (p=0.397). The ODM guided group was haemodynamically stable as shown by ODM and PPA measurements. However, the PPA guided group showed a significant increase of pulse-pressure-variability (p=0.002) that was not accompanied by a decline of stroke volume index displayed by the PPA (p=0.556) but indicated by a decline of stroke volume index by the ODM (p<0.001). The PPA group had significantly higher postoperative pain levels than the ODM group (p=0.036). In conclusion, goal-directed optimization by ODM and PPA showed differences in intraoperative cardiovascular parameters indicating that haemodynamic optimization is not consistent between the two monitors. Trial Registration ISRCTN.com ISRCTN64578872

Hemodynamic Consequences of Malignant Ascites in Epithelial Ovarian Cancer Surgery*: A Prospective Substudy of a Randomized Controlled Trial.

AbstractMalignant ascites (MA) is most commonly observed in patients scheduled for epithelial ovarian cancer (EOC) surgery and is supposed as a major risk factor promoting perioperative hemodynamic deterioration. We aimed to assess the hemodynamic consequences of MA on systemic circulation in patients undergoing cytoreductive EOC surgery.This study is a predefined post-hoc analysis of a randomized controlled pilot trial comparing intravenous solutions within a goal-directed algorithm to optimize hemodynamic therapy in patients undergoing cytoreductive EOC surgery. Ascites was used to stratify the EOC patients prior to randomization in the main study. We analyzed 2 groups according to the amount of ascites (NLAS: none or low ascites [<500 mL] vs HAS: high ascites group [>500 mL]). Differences in hemodynamic variables with respect to time were analyzed using nonparametric analysis for longitudinal data and multivariate generalized estimating equation adjusting the analysis for the randomized study groups of the main study.A total of 31 patients in the NLAS and 16 patients in the HAS group were analyzed. Although cardiac output was not different between groups suggesting a similar circulatory blood flow, the HAS group revealed higher heart rates and lower stroke volumes during surgery. There were no differences in pressure-based hemodynamic variables. In the HAS group, fluid demands, reflected by the time to reindication of a fluid challenge after preload optimization, increased steadily, whereas stroke volume could not be maintained at baseline resulting in hemodynamic instability after 1.5 h of surgery. In contrast, in the NLAS group fluid demands were stable and stroke volume could be maintained during surgery. Clinically relevant associations of the type of fluid replacement with hemodynamic consequences were particularly observed in the HAS group, in which transfusion of fresh frozen plasma (FFP) was associated to an improved circulatory flow and reduced vasopressor and fluid demands, whereas the administration of artificial infusion solutions was related to opposite effects.Malignant ascites >500 mL implies increased fluid demands and substantial alterations in circulatory blood flow during cancer surgery. Fresh frozen plasma transfusion promotes recovering hemodynamic stability in patients with malignant ascites >500 mL, in whom artificial infusion solutions could not prevent from hemodynamic deterioration.