Association of low mixed venous oxygen saturations during early ICU stay with increased 30-day and 1-year mortality after cardiac surgery: a single-center retrospective study

Hemodynamic control during cardiopulmonary bypass and the incidence of postoperative delirium- a post hoc analysis

BACKGROUND

Delirium is a common neurological complication after cardiac surgery. The purpose of the present study was to analyze the association between hemodynamic fluctuations during cardiopulmonary bypass (CPB) and the incidence of postoperative delirium (POD) in patients undergoing cardiac surgery with CPB.

METHODS

This post hoc analysis included one-hundred-ninety-five (n = 195) patients aged ≥ 65 years of whom seventy (n = 70) patients developed POD. Intraoperative hemodynamic variables specifically related to the conduct of CPB were digitally recorded at 1-minute intervals. Variables outside the presumed safe boundaries for mean arterial pressure (MAP), systemic perfusion flow index- L/min/BSA (QBSAI), systemic venous oxygen saturation (SVO2) and arterial oxygen delivery- ml/min/BSA (DO2) were defined and analyzed with reference to indices of area under the curve (AUC) and the relative proportion of registrations related to POD. POD was diagnosed according to DSM-5 criteria based on a test battery performed preoperatively and repeated twice postoperatively. Statistical tests used to verify observations outside the predefined norm included the Mann-Whitney U test and the chi-squared test.

RESULTS

Markers of hemodynamic control during CPB showed significant associations with POD. Both DO2 (P = 0.02) and QBSAI (P < 0.001) identified POD patients outside the predefined upper and lower safety limits. SVO2 values > 84% (P < 0.001) werealso associated with the development of POD. The number of SVO2 registrations below the lower safety limit was negligible, why statistical analysis seemed not useful. No association between MAP and POD registrations was identified.

CONCLUSIONS

This study revealed a clear association between markers of hemodynamic control and POD. These associations were most pronounced for DO2 and QBSAI. The detected association between high SVO2 and POD warrants further insight.

Thromboelastometry and two activated clotting tests in detecting residual heparin after protamine in cardiac surgical patients: A prospective cohort study

BACKGROUND

After cardiac surgery, complete heparin reversal with protamine is essential. Accordingly, there is a need for an accurate and precise point-of-care device to detect possible residual heparin after protamine administration.

OBJECTIVES

To compare two different activated clotting time (ACT) tests and thromboelastometry in detecting postprotamine heparin activity after cardiac surgery.

DESIGN

A single-centre prospective, observational study.

SETTING

University Hospital from September 2021 to February 2023.

PARTICIPANTS

Fifty-five adult, elective cardiac surgical patients.

INTERVENTIONS

The ACT-LR and ACT+ tests of Hemochron Signature Elite device, and the coagulation time (CT) ratio from INTEM and HEPTEM tests of ROTEM Sigma device, were analysed after protamine administration and compared to baseline values.

MAIN OUTCOME MEASURES

Based on postprotamine antifactor Xa (anti-fXa) activity, the patients were divided into heparin (anti-fXa ≥0.2 IU ml -1 ) and no heparin (anti-fXa ≤0.1 IU ml -1 ) groups.

RESULTS

There was a mean bias of 44 [95% confidence interval (CI) 40 to 47] celite seconds between ACT-LR and ACT+ measurements. The absolute changes in ACT-LR, ACT+ and INTEM:HEPTEM CT ratio were variable and did not differ between the groups. The mean ± SD percentage changes between postprotamine and baseline ACT-LR and ACT+ values were 5.9 ± 17.5 and 5.9 ± 16.9% in the no residual heparin group, compared to 1.4 ± 8.4 and 9.9 ± 12.5% in the residual heparin group. Receiver operator characteristic curves for postprotamine INTEM:HEPTEM CT ratio and for percentage changes in ACT-LR and ACT+ to detect an anti-fXa at least 0.2 IU ml -1 had areas under the curve of 0.496 (95% CI, 0.329 to 0.663), 0.425 (95% CI, 0.260 to 0.591) and 0.583 (95% CI, 0.417 to 0.749), respectively.

CONCLUSION

Both the ACT-LR and ACT+ tests of Hemochron Signature Elite device and the INTEM:HEPTEM CT ratio of ROTEM Sigma device have poor ability to detect residual heparin shortly after protamine administration.

Mixed Venous Oxygen Saturation Has a Poor Association with Cardiac Index during Early Intensive Care Unit Stay after Cardiac Surgery

OBJECTIVES

Our aim was to assess the association between mixed venous oxygen saturation (SvO2) and cardiac index (CI) among cardiac surgical patients during the initial 4 hours in the intensive care unit (ICU).

DESIGN

A single-center retrospective observational study.

SETTING

A tertiary-level university hospital.

PARTICIPANTS

Adult cardiac surgical patients (N = 4,958) operated on during 2007 to 2020.

INTERVENTIONS

Pulmonary artery catheter (PAC) measurements of SvO2 and CI were taken at ICU admission and 4 hours later. Linear regression was used to analyze the association between these variables.

MEASUREMENTS AND MAIN RESULTS

Paired CI and SvO2 values were available from 4,958 patients. The median (interquartile range) SvO2 was 68% (63-72%) at ICU admission and 66% (61-71%) 4 hours later. CI was 2.34 L/min/m2 (2.03-2.79) at ICU admission and 2.48 L/min/m2 (2.15-2.86) 4 hours later. In the entire cohort, a 10% change of SvO2 coincided with a CI change of 0.36 L/min/m2 (95% confidence interval 0.34-0.38) at ICU admission and a change of 0.33 L/min/m2 (0.31-0.36) at 4 hours. In patients with SvO2 less than 60%, the association between CI and SvO2 weakened further.

CONCLUSIONS

Factors affecting oxygen consumption and demand weaken the association between SvO2 and CI values in the early ICU recovery phase after cardiac surgery. Therefore, SvO2 and CI values should not be relied upon in clinical decision-making as reliable predictors of one another.

Validation of the capnodynamic method to calculate mixed venous oxygen saturation in postoperative cardiac patients

BACKGROUND

Cardiac output and mixed venous oxygen saturation are key variables in monitoring adequate oxygen delivery and have typically been measured using pulmonary artery catheterisation. The capnodynamic method measures effective pulmonary blood flow utilising carbon dioxide kinetics in ventilated patients. Combined with breath-by-breath measurements of carbon dioxide elimination, a non-invasive approximation of mixed venous oxygen saturation can be calculated.

METHODS

This study primarily investigated the agreement between mixed venous oxygen saturation calculated using the capnodynamic method and blood gas analysis of mixed venous blood sampled via a pulmonary artery catheter in 47 haemodynamically stable postoperative cardiac patients. Both measurements were synchronised and performed during alveolar recruitment by stepwise changes to the level of positive end-expiratory pressure. Simultaneously, we studied the agreement between effective pulmonary blood flow and thermodilution cardiac output. The Bland-Altman method for repeated measurements and calculation of percentage error were used to examine agreement. Measurements before and after alveolar recruitment were analysed by a paired t test. The study hypothesis for agreement was a limit of difference of ten percentage points between mixed venous oxygen saturation using the capnodynamic algorithm vs. catheter blood gas analysis.

RESULTS

Capnodynamic calculation of mixed venous saturation compared to blood gas analysis showed a bias of -0.02 [95% CI - 0.96-0.91] % and limits of agreement at 8.8 [95% CI 7.7-10] % and - 8.9 [95% CI -10-- 7.8] %. The percentage error was < 20%. The effective pulmonary blood flow compared to thermodilution showed a bias of - 0.41 [95% CI - 0.55-- 0.28] l.min-1 and limits of agreement at 0.56 [95% CI 0.41-0.75] l.min-1 and - 1.38 [95% CI - 1.57--1.24] l.min-1. The percentage error was < 30%. Only effective pulmonary blood flow increased by 0.38 [95% CI 0.20-0.56] l.min-1 (p < 0.01) after alveolar recruitment.

CONCLUSIONS

In this study, minimal bias and limits of agreement < 10% between mixed venous oxygen saturation calculated by the capnodynamic method and pulmonary arterial blood gas analysis confirmed the agreement hypothesis in stable postoperative patients. The effective pulmonary blood flow agreed with thermodilution cardiac output, while influenced by pulmonary shunt flow.

Reliability of Bioreactance and Pulse-Power Analysis in Measuring Cardiac Index During Open Abdominal Aortic Surgery

OBJECTIVE

To investigate the accuracy, precision, and trending ability of noninvasive bioreactance-based Starling SV and the mini invasive pulse-power device LiDCOrapid as compared to thermodilution cardiac output (TDCO) as measured by pulmonary artery catheter when assessing cardiac index (CIx) in the setting of elective open abdominal aortic (AA) surgery.

DESIGN

A prospective method-comparison study.

SETTING

Oulu University Hospital, Finland.

PARTICIPANTS

Forty patients undergoing elective open abdominal aortic surgery.

INTERVENTIONS

Intraoperative CI measurements were obtained simultaneously with TDCO and the study monitors, resulting in 627 measurement pairs with Starling SV and 497 with LiDCOrapid.

MEASUREMENTS AND MAIN RESULTS

The Bland-Altman method was used to investigate the agreement among the devices, and four-quadrant plots with error grids were used to assess trending ability. The agreement between TDCO and Starling SV was associated with a bias of 0.18 L/min/m2 (95% confidence interval [CI] = 0.13 to 0.23), wide limits of agreement (LOA = -1.12 to 1.47 L/min/m2), and a percentage error (PE) of 63.7 (95% CI = 52.4-71.0). The agreement between TDCO and LiDCOrapid was associated with a bias of -0.15 L/min/m2 (95% CI = -0.21 to -0.09), wide LOA (-1.56 to 1.37), and a PE of 68.7 (95% CI = 54.9-79.6). The trending ability of neither device was sufficient.

CONCLUSION

The CI measurements achieved with Starling SV and LiDCOrapid were not interchangeable with TDCO, and the ability to track changes in CI was poor. These results do not support the use of either study device in monitoring CI during open AA surgery.

Unresponsive Low Mixed Venous Oxygen Saturation During Early Intensive Care Unit Stay is Associated With Increased Risk of Organ Dysfunction After Cardiac Surgery: A Single-Center Retrospective Study

OBJECTIVES

The aim of the study was to determine if unresponsive mixed venous oxygen saturation (SvO2) values during early postoperative hours are associated with postoperative organ dysfunction.

DESIGN

A single-center retrospective observational study.

SETTING

A university hospital.

PARTICIPANTS

A total of 6,282 adult patients requiring cardiac surgery who underwent surgery in a University Hospital from 2007 to 2020.

INTERVENTIONS

A pulmonary artery catheter was used to gather SvO2 samples after surgery at admission to the intensive care unit (ICU) and 4 hours later. For the analysis, patients were divided into 4 groups according to their SvO2 values. The rate of organ dysfunctions categorized according to the SOFA score was then studied among these subgroups.

MEASUREMENTS AND MAIN RESULTS

The crude mortality rate for the cohort at 1 year was 4.3%. Multiple organ dysfunction syndrome (MODS) was present in 33.0% of patients in the early postoperative phase. During the 4-hour initial treatment period, 43% of the 931 patients with low SvO2 on admission responded to goal-directed therapy to increase SvO2 >60%; whereas, in 57% of the 931 patients, the low SvO2 was sustained. According to the adjusted logistic regression analyses, the odds ratio for MODS (4.23 [95% CI 3.41-5.25]), renal- replacement therapy (4.97 [95% CI 3.28-7.52]), time on a ventilator (2.34 [95% CI 2.17-2.52]), and vasoactive-inotropic score >30 (3.62 [95% CI 2.96-4.43]) were the highest in the group with sustained low SvO2.

CONCLUSIONS

Patients with SvO2 <60% at ICU admission and 4 hours later had the greatest risk of postoperative MODS. Responsiveness to a goal-directed therapy protocol targeting maintaining or increasing SvO2 ≥60% at and after ICU admission may be beneficial.