Stroke Volume and Arterial Pressure Fluid Responsiveness in Patients With Elevated Stroke Volume Variation Undergoing Major Vascular Surgery: A Prospective Intervention Study.

OBJECTIVES: The identification of potential hemodynamic indicators to increase the predictive power of stroke-volume variation (SVV) for mean arterial pressure (MAP) and stroke volume (SV) fluid responsiveness. DESIGN: A prospective intervention study. SETTING: At a single-center university hospital. PARTICIPANTS: Nineteen patients during major vascular surgery with 125 fluid interventions. INTERVENTIONS: When SVV ≥13% occurred for >30 seconds, 250 mL of Ringer's lactate were given within 2 minutes. MEASUREMENTS AND MAIN RESULTS: Hemodynamic variables, such as pulse-pressure variation (PPV) and dynamic arterial elastance (Edyn), were measured by pulse power-wave analysis. The outcomes were MAP and SV responsiveness, defined as an increase of at least 10% of MAP and SV within 5 minutes of the fluid intervention. Of the fluid interventions, 48% were MAP-responsive, and 66% were SV-responsive. The addition of PPV and Edyn cut-off values to the SVV cut-off decreased sensitivity from 1-to-0.66 to-0.82, and concomitantly increased specificity from 0-to- 0.65-to-0.93 for the prediction of MAP and SV responsiveness in the authors' study setting. The areas under the receiver operating characteristic curves of PPV and Edyn for the prediction of MAP responsiveness were 0.79 and 0.75, respectively. The areas under the receiver operating characteristic curves for PPV and Edyn to predict SV responsiveness were 0.85 and 0.77, respectively. CONCLUSIONS: The PPV and Edyn showed good accuracy for the prediction of MAP and SV responsiveness in patients with elevated SVV during vascular surgery. Either PPV or Edyn may be used in conjunction with SVV to better predict MAP and SV fluid responsiveness in patients undergoing vascular surgery.

Characteristics of Interleukin-6 Signaling in Elective Cardiac Surgery-A Prospective Cohort Study.

Interleukin-6 (IL-6) can cause pro- and anti-inflammatory effects via different signaling pathways. This prospective study investigated the perioperative kinetics of IL-6, soluble IL-6 receptor (sIL-6R), and soluble glycoprotein 130 (sgp130) in elective patients undergoing cardiopulmonary bypass (CPB). IL-6, sIL-6R, and sgp130 were measured simultaneously and consecutively at 19 timepoints until the 10th postoperative day (POD). The proportion of pro- and anti-inflammatory pathways were determined by calculating sIL-6R/IL-6 and sIL-6R/sgp130 ratios. We analyzed 93 patients. IL-6 increased during surgery with reaching a plateau two hours after CPB and peaking on POD 1 (188.5 pg mL-1 (IQR, 126.6; 309.2)). sIL-6R decreased at the beginning of the surgical procedure, reaching a nadir level on POD 2 (26,311 pg mL-1 (IQR, 22,222; 33,606)). sgp130 dropped immediately after CPB initiation (0.13 ng mL-1 (IQR, 0.12; 0.15)), followed by a continuous recovery until POD10. The sIL-6R/IL-6 ratio decreased substantially at the beginning of the procedure, reaching a nadir on POD 1 (149.7 (IQR, 82.4; 237.4)), while the sIL-6R/sgp130 ratio increased simultaneously until 6 h post CPB (0.219 (IQR 0.18; 0.27)). In conclusion, IL-6 exhibited high inter-individual variability reflecting an inhomogeneous inflammatory response. Pro-inflammatory effects and overwhelming inflammation were rare and predominantly anti-inflammatory effects were found.

The effect of acute ventilation-perfusion mismatch on respiratory heat exchange in a porcine model.

BACKGROUND: Respiratory heat exchange is an important physiological process occurring in the upper and lower respiratory tract and is usually completed when inspired gases reach the alveoli. Animal and human studies demonstrated that heat exchange can be modulated by altering pulmonary ventilation and perfusion. The purpose of this study was to examine the effect of acute ventilation-perfusion (V/Q) mismatch on respiratory heat exchange. In clinical practice, monitoring respiratory heat exchange might offer the possibility of real-time tracking of acute V/Q-mismatch. METHODS: In 11 anesthetized, mechanically ventilated pigs, V/Q-mismatch was established by means of four interventions: single lung ventilation, high cardiac output, occlusion of the left pulmonary artery and repeated whole-lung lavage. V/Q-distributions were determined by the multiple inert gas elimination technique (MIGET). Respiratory heat exchange was measured as respiratory enthalpy using the novel, pre-commercial VQm™ monitor (development stage, Rostrum Medical Innovations, Vancouver, CA). According to MIGET, shunt perfusion of low V/Q compartments increased during single lung ventilation, high cardiac output and whole-lung lavage, whereas dead space and ventilation of high V/Q compartments increased during occlusion of the left pulmonary artery and whole-lung lavage. RESULTS: Bohr dead space increased after pulmonary artery occlusion and whole-lung lavage, venous admixture increased during single lung ventilation and whole-lung lavage, PaO2/FiO2 was decreased during all interventions. MIGET confirmed acute V/Q-mismatch. Respiratory enthalpy did not change significantly despite significant acute V/Q-mismatch. CONCLUSION: Clinically relevant V/Q-mismatch does not impair respiratory heat exchange in the absence of additional thermal stressors and may not have clinical utility in the detection of acute changes.

Urinary neprilysin for early detection of acute kidney injury after cardiac surgery: A prospective observational study.

BACKGROUND: Acute kidney injury (AKI) predicts adverse outcomes after cardiac surgery. The accuracy of using changes in serum creatinine for diagnosis and grading of AKI is limited in the peri-operative cardiac surgical setting and AKI may be underdiagnosed due to haemodilution from cardiopulmonary bypass priming and the need for intra-operative and postoperative volume resuscitation. OBJECTIVES: To determine whether the urinary biomarker neprilysin can be used as a marker for the early detection of AKI after cardiac surgery. DESIGN: Prospective, observational cohort study. SETTING: Austrian tertiary referral centre. PATIENTS: 96 Patients undergoing elective cardiac surgery with cardiopulmonary bypass. MAIN OUTCOME MEASURES: Differences and discriminatory power of neprilysin levels early after cardiac surgery and on postoperative day 1 between patients with or without AKI, as defined by the Kidney Disease Improving Global Outcomes Group. RESULTS: AKI was found in 27% (n=26). The median neprilysin levels on postoperative day 1 were significantly higher in the AKI than in the non-AKI group, 4.0 [interquartile range (IQR): 2 to 6.25] vs. 2.0 ng ml [IQR: 1.0 to 4.5], P = 0.0246, respectively. In addition, the median neprilysin levels at the end of surgery were significantly different between both groups, 5.0 [IQR: 2.0 to 9.0] vs. 2.0 ng ml [IQR: 1.0 to 4.0], P = 0.0055, respectively. The discriminatory power of neprilysin for detecting early AKI corresponded to an area under the curve of 0.77 (95% confidence interval, 0.65 to 0.90). CONCLUSION: Urinary neprilysin has potential as a biomarker for the early detection of AKI after cardiac surgery and has comparable discriminatory power to recently studied AKI biomarkers. TRIAL REGISTRATION: The trial was registered at ClinicalTrials.gov (NCT03854825, https://clinicaltrials.gov/ct2/show/NCT03854825).

Percutaneous cannulation for extracorporeal membrane oxygenation (ECMO): A method for pig experimental models.

Pigs are often used for experimental models of cardiogenic shock, cardiac arrest or acute lung injury with veno-arterial (VA) or veno-venous (VV) extracorporeal membrane oxygenation (ECMO) implementation. Percutaneous (as opposed to surgical) cannulation in experimental models has potential advantages, including, less surgical trauma or stressful stimuli and less bleeding complications when compared to open chest cannulation. However, pig anatomy can also be a challenge because of the deep location and angled anatomy of the femoral artery. The Seldinger technique and the use of a percutaneous cannulation kit is feasible in pigs. Summarized here we present (Graphical Abstract):•Percutaneous ECMO cannulation method for non-cardiac surgeon.•Establishment of this simple and rapid methods for pig experimental models.•Predictable complications of this method.

Early Antibiotic Prophylaxis Prior to Bypass Surgery Improves Tissue Penetration.

BACKGROUND: We previously identified preparation of the internal mammary artery as a risk factor significantly impairing antibiotic tissue penetration into the presternal subcutaneous tissue. We, therefore, adapted our dosing schema regarding preoperative timing to overcome this risk factor. METHODS: Eight patients who underwent coronary artery bypass grafting with a left internal mammary artery and vein grafts were included in this clinical trial. Cefazolin (4 g) was administered twice (3 hours and 1 hour) prior to skin incision and once during skin closure (2 g). Antibiotic concentrations were measured with subcutaneous microdialysis probes on both sternal sides. Results were directly compared with the previously published patient cohort receiving the standard schema (4 g cefazolin prior to skin incision and 2 g during closure). RESULTS: All patients (7 male, 1 female, 69 ± 7 years, 26.3 ± 3.9 kg/m2) survived the perioperative period. Mean area under the curve on the right and left sternal side was 117.0 ± 92.5 µg/mL and 114.5 ± 83.2 µg/mL, respectively (p = 0.95). This was well above the previously measured mean peak tissue concentrations without early preoperative antibiotic administration on the side of mammary artery harvesting (52.4 ± 48.5 µg/mL vs. 13.1 ± 5.8 µg/mL; p = 0.039). The %fT > minimal inhibitory concentration (MIC) for Staphylococcus epidermidis and Staphylococcus aureus during the first 10 hours in presternal tissue was ≥ 70% but did not differ compared with standard schema. CONCLUSIONS: Early, additional preoperative administration of cefazolin was able to significantly increase peak tissue concentrations during surgery compared with the standard protocol. No difference, however, could be achieved in the percentage of time during which the concentration exceeded the MIC.

Carotid artery blood flow velocities during open-heart surgery and its association with delirium: A prospective, observational pilot study.

The aim of this prospective observational single-centre pilot study was to evaluate the association between alterations in carotid artery blood flow velocities during cardiac surgery and postoperative delirium.Carotid artery blood flow velocity was determined perioperatively at 5 different timepoints by duplex sonography in 36 adult cardiac surgical patients. Delirium was assessed using the Confusion Assessment Method for the ICU and the Intensive Care Delirium Screening Checklist. Additionally, blood flow velocities in the middle cerebral arteries, differences in regional cerebral tissue oxygenation and quantity and quality of microemboli were measured.Delirium was detected in 7 of 36 patients. After cardiopulmonary bypass carotid artery blood flow velocities increased by +23 cm/second (95% confidence interval (CI) 9-36 cm/second) in non-delirious patients compared to preoperative values (P = .002), but not in delirious patients (+3 cm/second [95% CI -25 to 32 cm/second], P = .5781). Middle cerebral artery blood flow velocities were higher at aortic de-cannulation in non-delirious patients (29 cm/second [inter-quartile range (IQR), 24-36 cm/second] vs 12 cm/second [IQR, 10-19 cm/second]; P = .017). Furthermore, brain tissue oxygenation was higher in non-delirious patients during surgery.Our results suggest that higher cerebral blood flow velocities after aortic de-clamping and probably also improved brain oxygenation might be beneficial to prevent postoperative delirium.

Evaluation of an active decision support system for hemodynamic optimization during elective major vascular surgery.

BACKGROUND: Active decision support systems implementing goal directed therapy may be an approach to reduce disparities in outcome between different health care providers. We assessed feasibility of and adherence to an active decision support system (ADSS) comprising fluids, vasopressors, and dobutamine to optimize hemodynamics during high-risk vascular surgery. METHODS: In this prospective observational trial a closed-loop goal-directed therapy protocol, employing the minimally-invasive LiDCOrapid device, was used to actively provide advice to the anesthesiologist during surgery. All given suggestions and all interventions were recorded. Every intervention without or against the given advice had to be justified. The primary outcome parameters were the number of interventions done according to the ADSS and its duration of use. Reasons for non-compliance served to describe its limitations. RESULTS: The active decision support system was employed in 32 patients for 137 hours. Median (IQR) use of the ADSS as percentage of surgery time was 100% (94-100%) with 743 interventions being executed. 634 interventions were done according to ADSS proposals. Reasons to act against or without advice were: hemodynamic instability (6%), foreseeing a surgical event (2%), medical reasons (2%), awaiting hemodynamic improvement (1%) and orders by senior physician or surgeons (1%). In five patients the anesthesiologist decided to modify intervention thresholds of the underlying protocol. CONCLUSIONS: High rates of compliance underline clinical acceptability and feasibility of this ADSS during vascular surgery. It may therefore facilitate the work of anesthesiologists and reduce disparities in patient outcomes due to different healthcare providers. Particularly, rapidly developing hemodynamic perturbances as well as co-factors the ADSS as of now does not anticipate are current limitations. These findings may serve to further improve this stand-alone real-time ADSS.

Postoperative management of patients undergoing cardiac surgery in Austria : A national survey on current clinical practice in hemodynamic monitoring and postoperative management.

BACKGROUND: No data are currently available regarding the current clinical practice in postoperative care of cardiac surgical patients in Austria. OBJECTIVE: The study investigated the current intensive care management concerning hemodynamic monitoring and strategies to treat common perioperative disorders of patients after cardiac surgery in Austria. METHODS: A survey consisting of 31 questions was sent to intensivists at all 9 hospitals offering cardiac surgery in Austria. RESULTS: The response rate was 100%. The mean number of procedures on cardiopulmonary bypass per centre was 722 ± 223. In the majority of cases postoperative critical care is performed by anesthesiologists. Blood gas analysis, pulse oximetry, electrocardiogram, temperature, central venous pressure, arterial pressure and hourly urine output are de facto standard monitoring in all centers. Transesophageal echocardiography is available in all centers and is frequently used. Crystalloids are the first choice for volume replacement, whereas levosimendan and adrenaline are employed for the treatment of low cardiac output syndrome. CONCLUSIONS: This study provides insights into the current state of postoperative management of cardiac surgical patients in Austria. Standard monitoring as proposed by international guidelines is well established in Austrian intensive care units. Echocardiography is widely seen as a very important tool in the postoperative care of cardiac surgical patients. Knowledge about the status quo of postoperative intensive care management of cardiac surgical patients enables further development of patient care.