Patients
Sixty patients who underwent cardiac surgery using CPB from October to May 2020 were enrolled in this study. This study was approved by the ethical monitoring committee of Hamamatsu medical university (Ethical committee approval No.19–109)
Anesthesia and monitoring
Standardized inhalation anesthetic and propofol/remifentanil-based anesthetic protocol was carried out in all patients and monitored using Masimo SedLine Patient State Index® (PSi) (Masimo Corp., Irvine, CA) (PSi of the anesthetized patients maintained with in the rage of 25–50). Other monitoring like Non-invasive Blood Pressure (BP), pulse, Invasive Blood Pressure (IBP), Central Venous Pressure (CVP), pulmonary artery pressure, oximetry, electrocardiogram, arterial pressure monitoring was apllied to patients undergoing surgery. Body and blood temperature were also monitored during surgery and cardiopulmonary bypass pump process.
Hemoglobin concentration measurements
Before the start of general anesthesia, arterial catheter was placed on right Radical Artery. SpHb was measured using Root® with Radical-7® (Masimo Corp. Irvine, CA, USA) with disposable adhesive SpHb sensor (RD rainbow SET Adt, Rev.O). The sensor was applied right-hand ring finger covered with opaque shield to protect interference with ambient light. SpHb continuously monitored from anesthetic induction until the surgical process ends. Perfusion Index (Pi), the ratio of pulsatile blood flow to non-pulsatile blood, was measured to check peripheral perfusion with SpHb. These data collected every two second via MICT, data downloading software (Masimo Corp., Irvine, CA, USA) and recorded at same time of blood drawing.
Hemoglobin analysis with the automated ABL-90 analyzer (tHb) was executed with standard clinical practice for critical cardiac surgery. Blood analysis was drawn via arterial catheter and analyzed immediately after collection. The timing of blood drawing is right after completion of anesthesia induction, before and after the CPB and at surgical events based on anesthesiologist requirements.
Blood transfusion
Hemoglobin concentration thresholds for the blood transfusion were recommended commonly by world standard groups were 6–8 g dl− 1 during surgical process with either autologous blood or heterologous blood depending on the patient’s state. Blood transfusion was decided from the laboratory analysis data (tHb) and anesthesiologists’ judgements. On the other hand, in this study SpHb values were not used for blood transfusion decision making.
Statistical analysis
Patients’ demographic and clinical data were collected and reported in Table 1. Patients’ demographic details were expressed as mean value ± standard deviation (SD) and 60-day mortality was found to be nil in this study. The concordance between two methods was examined using linear regression and Bland and Altman analysis, by determining the bias, precision, agreement between tHb and SpHb hemoglobin analysis. Limits of agreement (LoA) were calculated as the mean bias ± 1.96 SD. SpHb values are not able to be evaluated when the low perfusion index happened due to the usage of cardiopulmonary bypass devices.[23] Trending ability was assessed in in addition to regression analysis using the four-quadrant plot and Critchley polar plot to test the change in the directionality of Hb concentration. As per the specification we exclude the zones of 1.0 (g/dL) to minimize the interference of analysis. In terms of Critchley polar plot, concordance rate was defined within ± 30°.[8]
Table 1
Characteristics |
Average age (years) | 69.62 ± 12.58 |
Gender (Male/Female) | 21/39 |
Average height (cm) | 159.64 ± 9.73 |
Average weight (Kg) | 58.57 ± 12.28 |
BMI | 22.90 ± 3.80 |
Blood loss (mL) | 1137.93 ± 860.91 |
Blood transfusion (mL) | 1044.78 ± 528.15 |
Surgery Coronary artery bypass grafting (CABG) Valve replacement surgery CAPBG with Valve replacement surgery Thoracic vascular surgery | 15 (with CPB) 4 (without CPB not included in statistics) 23 8 11 |
Anesthesia time(hh:mm) | 8:18 ± 2:29 |
Pump time (hh:mm) | 3:28 ± 1:16 |
Surgery time (hh:mm) | 6:36 ± 2:21 |
60 day mortality | 0 |
Statistical analyses were performed using SPSS v 25 for Macintosh (IBM Corp, Armonk, NY) and R 4.0.1 statistical software (R Foundation for Statistical Computing, Vienna, Austria).