Management of intraoperative fluid balance and blood conservation techniques in adult cardiac surgery

The importance of autologous blood transfusion in lung transplantation and cardiovascular surgeries

Background

In this study, we aimed to investigate the effect of using autologous blood recovery systems on transfusion-related complications in patients undergoing lung transplantation and cardiovascular surgeries.

Methods

Between May 2016 and May 2019, a total of 104 patients (90 males, 14 females; mean age: 59.3±16.4 years; range, 12 to 89 years) in whom cell-saver and autologous blood recovery systems were used during lung transplantation or cardiovascular surgeries were retrospectively analyzed. The patients were divided into two groups as Group 1 (n=61) consisting of patients who received autologous blood transfusion and as Group 2 (n=43) consisting of patients who did not. Data including demographic and clinical characteristics of the patients, operation data, and postoperative complications were recorded.

Results

The total amount of transfused blood/blood product was found to be significantly higher in Group 1 (p=0.018). However, transfusionrelated complications were found to be higher in Group 2 (p=0.0261). There was no significant difference in the length of hospital stay between the groups.

Conclusion

Autologous blood transfusion may prevent the development of transfusion-related complications by reducing the amount of allogenic transfusion in major surgical procedures. In our study, the autologous blood transfusion was used in critical patients with major bleeding and, therefore, the total amount of transfused blood/blood product was higher in these patients. Nevertheless, lower complication rates in this patient group emphasize the importance of autologous blood transfusion.

Conventional hemofiltration during cardiopulmonary bypass increases the serum lactate level in adult cardiac surgery

OBJECTIVE

To evaluate the effect of hemofiltration during cardiopulmonary bypass on lactate level in adult patients who underwent cardiac surgery.

DESIGN

An observational study.

SETTING

Prince Sultan cardiac center, Riyadh, Saudi Arabia.

PARTICIPANTS

The study included 283 patients classified into two groups: Hemofiltration group (n=138), hemofiltration was done during CPB. Control group (n = 145), patients without hemofiltration.

INTERVENTIONS

Hemofiltration during cardiopulmonary bypass.

MEASUREMENTS AND MAIN RESULTS

Monitors included hematocrit, lactate levels, mixed venous oxygen saturation, amount of fluid removal during hemofiltration and urine output. The lactate elevated in group H than group C (P < 0.05), and the PH showed metabolic acidosis in group H (P < 0.05). The mixed venous oxygen saturation decreased in group H than group C (P < 0.05). The number of transfused packed red blood cells was lower in group H than group C (P < 0.05). The hematocrit was higher in group H than group C (P < 0.05). The urine output was lower in group H than group C (P < 0.05).

CONCLUSIONS

Hemofiltration during cardiopulmonary bypass leads to hemoconcentration, elevated lactate level and increased inotropic support. There are some recommendations for hemofiltration: First; Hemofiltration should be limited for patients with impaired renal function, positive fluid balance, reduced response to diuretics or prolonged bypass time more than 2 hours. Second; Minimal amount of fluids should be administered to maintain adequate cardiac output and reduction of priming volumes is preferable to maintain controlled hemodilution. Third; it should be done before weaning of or after cardiopulmonary bypass and not during the whole time of cardiopulmonary bypass.

Cerebral oximetry in cardiac anesthesia

Cerebral oximetry based on near-infrared spectroscopy (NIRS) is increasingly used during the perioperative period of cardiovascular operations. It is a noninvasive technology that can monitor the regional oxygen saturation of the frontal cortex. Current literature indicates that it can stratify patients preoperatively according their risk. Intraoperatively, it provides continuous information about brain oxygenation and allows the use of brain as sentinel organ indexing overall organ perfusion and injury. This review focuses on the clinical validity and applicability of this monitor for cardiac surgical patients.

Monitoring of brain oxygen saturation (INVOS) in a protocol to direct blood transfusions during cardiac surgery: a prospective randomized clinical trial

Background

Blood transfusions are common in cardiac surgery, but have been associated with increased morbidity and long-term mortality. Efforts to reduce blood product use during cardiac surgery include fluid restriction to minimize hemodilution, and protocols to guide transfusion decisions. INVOS is a modality that monitors brain tissue oxygen saturation, and could be useful in guiding decisions to transfuse. However, the role of INVOS (brain tissue oxygen saturation) as part of an algorithm to direct blood transfusions during cardiac surgery has not been evaluated. This study was conducted to investigate the value of INVOS as part of a protocol for blood transfusions during cardiac surgery.

Methods

Prospective, randomized, blinded clinical trial, on 150 (75 per group) elective cardiac surgery patients. The study was approved by the Institution Ethics committee and all patients gave written informed consent. Data were initially analyzed based on “intention to treat”, but subsequently were also analyzed “per protocol”.

Results

When protocol was strictly followed (“per protocol analysis”), compared to the control group, significantly fewer patients monitored with INVOS received any blood transfusions (46 of 70 patients in INVOS group vs. 55 of 67 patients in the control group, p = 0.029). Similarly, patients monitored with INVOS received significantly fewer units of red blood cell transfusions intraoperatively (0.20 ± 0.50 vs. 0.52 ± 0.88, p = 0.008) and overall during hospital stay (1.31 ± 1.20 vs. 1.82 ± 1.46, p = 0.024). When data from all patients (including patient with protocol violation) were analyzed together (“intention to treat analysis”), the observed reduction of blood transfusions in the INVOS group was still significant (51 of 75 patients transfused in the INVOS group vs. 63 of 75 patients transfused in the control group, p = 0.021), but the overall number of units transfused per patient did not differ significantly between the groups (1.55 ± 1.97 vs. 1.84 ± 1.41, p = 0.288).

Conclusions

Our data suggest that INVOS could be a useful tool as part of an algorithm to guide decisions for blood transfusion in cardiac surgery. Additional data from rigorous, well designed studies are needed to further evaluate the role of INVOS in guiding blood transfusions in cardiac surgery, and circumvent the limitations of this study.

Trial registration

ClinicalTrials.gov: NCT00879463

Sizing gaseous emboli using Doppler embolic signal intensity

Extension of transcranial Doppler embolus detection to estimation of bubble size has historically been hindered by difficulties in applying scattering theory to the interpretation of clinical data. This article presents a simplified approach to the sizing of air emboli based on analysis of Doppler embolic signal intensity, by using an approximation to the full scattering theory that can be solved to estimate embolus size. Tests using simulated emboli show that our algorithm is theoretically capable of sizing 90% of "emboli" to within 10% of their true radius. In vitro tests show that 69% of emboli can be sized to within 20% of their true value under ideal conditions, which reduces to 30% of emboli if the beam and vessel are severely misaligned. Our results demonstrate that estimation of bubble size during clinical monitoring could be used to distinguish benign microbubbles from potentially harmful macrobubbles during intraoperative clinical monitoring.