A minimal priming technique that allows for a higher circulating hemoglobin on cardiopulmonary bypass

The effectiveness of acute normolvolemic hemodilution and autologous prime on intraoperative blood management during cardiac surgery

Objective:

Intraoperative blood management during cardiac surgery is a multifaceted process incorporating various interventions directed at optimizing oxygen delivery and enhancing hemostasis. The purpose of this study was to evaluate the effects of acute normovolemic hemodilution (ANH) and autologous priming (AP) on preserving the hematocrit during cardiopulmonary bypass (CPB).

Method:

Case records from a national registry of adult patients who underwent cardiac surgery between January and October 2016 were reviewed. Groups were determined as follows: ANH, AP, ANH+AP or Neither. Primary endpoint was first the hematocrit on CPB with secondary endpoints of hematocrit drift and red blood cell (RBC) transfusion rate.

Results:

Eighteen thousand and twenty-four (18,024) consecutive patients were reviewed. The first CPB hematocrit was lowest in the ANH group (26.5%±4.4%) and highest in ANH+AP patients (27.5%±4.8%) (p<0.001). The change in hematocrit was greatest in the ANH group (8.3%±3.9%) compared to both the AP (6.4%±3.8%) and ANH+AP (6.9%±4.1%) groups (p<0.001). Intraoperative RBC transfusions were as follows: ANH 26 (7.8%), AP 2,531 (20.0%), ANH+AP 287 (10.3%) and Neither 592 (26.7%) (p<0.001).

Conclusions:

Regression results show that the use of ANH will result in the greatest decline in hematocrit values. When combined with AP, higher hematocrits and lower transfusions were seen.

Prospective study on cardiopulmonary bypass prime reduction and its effect on intraoperative blood product and hemoconcentrator use

Purpose: Evaluate the feasibility and clinical significance of crystalloid prime reduction during the initiation of cardiopulmonary bypass (CPB) using a modified bridge on the cardioplegia delivery system.

Methods: Prospective trial of crystalloid prime reduction using a standard Duraflow®-coated CPB circuit and Vanguard® 2:1 cardio plegia delivery system. Standard prime volume was 1500 cc of Plasmalyte. Prime was reduced via the bridge in the cardioplegia system during initiation of CPB. Packed red blood cells (PRBC) were transfused for hematocrit (Hct) less than 24% while rewarming. A hemoconcentrator was used if the patient’s circulating blood volume exceeded 150% of calculated. All data were prospectively collected.

Results: Two hundred and twenty-two consecutive patients undergoing cardiac surgery utilizing CPB were evaluated. There were 107 patients with normal prime volume (NPV) and 115 patients with reduced prime volume (RPV). There was no significant difference in sex, mean age, weight, body surface area (BSA), pre-op Hct, procedure time or procedure between the two groups. There was no difference in total crystalloids infused by the anesthetists (average NPV 1205 cc versus RPV 1148 cc). The average RPV was 622 cc (range 400 - 1100 cc) or a 59% reduction. Post-op Hct revealed no difference (NPV 28% versus RPV 29%). There was a 24% reduction in patients requiring PRBC (NPV n=23 versus RPV n=18). The use of hemoconcentrators was reduced by 49% (NPV n=18 versus RPV n=11). The average urine output for both groups exceeded 100 cc/hour while on CPB.

Conclusion: Using a modified cardioplegia delivery system is a safe and effective method of CPB prime reduction. A RPV resulted in fewer patients requiring PRBC transfusions and fewer hemoconcentrators used. Based on our experience, we would recommend attempting to reduce prime volume in all patients undergoing CPB.

Efficacy of a miniature centrifugal rotary pump (TinyPump) for transfusion-free cardiopulmonary bypass in neonatal piglets

We have developed a miniaturized semiclosed cardiopulmonary bypass (CPB) circuit incorporating a centrifugal blood pump (TinyPump) with a volume of 5 ml. The current study was undertaken to evaluate the hemolytic performance of the TinyPump in comparison with the BioPump and to investigate the impact of different CPB circuit volumes on hemodilution, coagulation, and the inflammatory response. Twelve 1-week-old piglets (3.4 +/- 0.2 kg) were used. The circuit comprised a centrifugal pump, a membrane oxygenator, and a cardiotomy reservoir. Cardiopulmonary bypass was conducted with mild hypothermia at 150 ml/kg/min for 3 hours. Transfusion was not performed. Priming volume was 68 ml for the circuit with the TinyPump and 111 ml for the circuit with the BioPump. Although the TinyPump required higher speed, plasma free hemoglobin levels after CPB were not different between the groups. After CPB, the TinyPump group had a significantly higher hematocrit (27% +/- 3% vs. 23% +/- 3%) and lower platelet reduction rate, lower thrombin-antithrombin complex levels, and lower interleukin-6 levels. Better lung compliance with less water content was observed in the TinyPump group. The TinyPump maintained CPB with acceptable hemolysis and lower inflammatory responses. This miniaturized CPB circuit may make transfusion-free open heart surgery feasible in neonates and would help to prevent postoperative organ dysfunction.

A clinically relevant large-animal model for evaluation of tissue-engineered cardiac surgical patch materials

Extracellular matrix (ECM) scaffolds may be useful as a tissue engineering approach toward myocardial regeneration in the infarcted heart. An appropriate large-animal model for testing the utility of biologically derived ECM in this application is needed. The purpose of this study was to develop such a model for optimal procedural success during and after patch implantation surgery. Myocardial infarction (MI) was created by embolization of the diagonal artery (DA) branch of the left anterior descending coronary artery with collagen suspension. After 4 to 6 weeks, 14 pigs received patch implant (ECM or expanded polytetrafluoroethylene). Six pigs were infarcted in the first DA and seven pigs in the second DA. Electrophysiology study was performed within 3 days before surgery. During surgery, the size and location of the infarct were measured. Infarcted myocardium (1.5-cm diameter) was transmurally excised under partial cardiopulmonary bypass. Patches (3-cm diameter) were sutured to the endomyocardial defect. Four pigs died postoperatively. After 1 month, 10 pigs were euthanized and the locations of patches were examined. Success rate of patch implant in the second DA (85.7%) was higher than the first DA (50%) group. Infarct size in the second DA was smaller than in the first DA (4.6+/-1.2 vs. 10.8+/-2.4 cm(2), P<.05). The second DA was more anteriorly positioned, which enabled easier access from the midsternal thoracotomy. However, the first DA was more laterally located requiring more manipulation of the heart during surgery. Electrophysiology revealed no ventricular tachyarrhythmia in the second DA but 33.3% in the first DA group (P<.05). At necropsy, the endocardial position of the first DA-infarct patches was anteroapical, whereas the second DA-infarct patches were more basolateral and often involved the anterior papillary muscle. The success rate of patch implant was associated with infarction size and location, and may be related to arrhythmic substrate. Experimental MI created by the second DA embolization is a feasible model for investigation of tissue-engineered cardiac patch implantation. This large-animal model is also suitable for study of cell therapy via endocardial catheter-based approaches or open surgical methods.

Retrograde autologous priming of the cardiopulmonary bypass circuit reduces blood transfusion after coronary artery surgery

BACKGROUND

Hemodilution occurring with cardiopulmonary bypass imposes a risk for blood transfusion. Autologous priming of the cardiopulmonary bypass circuit at the initiation of bypass partially replaces the priming solution with autologous blood. We examined the efficacy of autologous priming of the circuit in reducing blood transfusion.

METHODS

One hundred and four patients were entered into a prospective, randomized, controlled study. Initiation of cardiopulmonary bypass was with or without autologous priming.

RESULTS

With autologous priming, a mean volume of 808.8 +/- 159.3 mL of priming solution was replaced with autologous blood. This allowed a higher hematocrit value on admission to the intensive care unit and at discharge from hospital. In all, 49% of the control group required a blood transfusion compared with 17% from the autologous priming group (p = 0.0007). The mean volume of blood transfused was 277.6 +/- 363.8 mL in the control group compared with 70.1 +/- 173.5 mL in the autologous priming group (p = 0.0005).

CONCLUSIONS

Retrograde autologous priming of the bypass circuit reduces homologous blood transfusion owing to the reduction in bypass circuit priming volume.

Autotransfusion in cardiac surgery

There are a number of problems with allogeneic blood transfusion. Some of these problems are defined and can be quantified, such as the problem of rising cost or the risk of viral infection, but some of the problems are not well defined and it is only outcome data that point to allogeneic blood transfusion contributing to patient mortality and morbidity. Autotransfusion includes any technique in which the patient's own blood is collected, processed and stored, followed by reinfusion when circumstances dictate. In the perioperative period of cardiac surgery, a number of techniques are recognized as useful in this context. Preoperative autologous donation, with or without erythropoietin supplementation, intraoperative acute normovolaemic haemodilution, intraoperative cell salvage, postoperative cell salvage (reinfusion of shed mediastinal blood) and platelet rich plasmapheresis are all techniques which are used with more or less enthusiasm to reduce the need for an allogeneic blood transfusion. Modification of the priming technique of the cardiopulmonary bypass circuit using an autologous blood prime is included in this review even though it does not fall strictly within the definition of autotransfusion. Although autotransfusion is not the answer to every problem, there is no doubt that it should play a significant part in the strategy of blood conservation.

Vacuum-assisted venous return in pediatric cardiopulmonary bypass

Vacuum-assisted venous return (VAVR) has been reported to offer benefits for adults undergoing cardiopulmonary bypass (CPB), such as improved venous return, lowering priming volume (by eliminating the need to prime the venous line), and the use of smaller venous cannulae. All these benefits would be of particular value in pediatric perfusion because of the unique challenges of these smaller patients and the relatively large components of the CPB circuit. We have been using VAVR in children since the early summer of 1998 after we became comfortable with the technique and convinced of its efficacy in adults. Ours is a medium-sized pediatric caseload of slightly more than 100 CPB cases per year. With that caseload, it is most effective for us to minimize the inventory of different sizes of disposables used. We have opted for an oxygenator/reservoir that has a maximum flow of 4 liters with a priming volume of about 1 liter. We have been unhappy with the large prime volume in infants and earlier, in 1997-1998, were using a smaller prime oxygenator/reservoir until it was recalled. Faced again with a larger priming volume in the infants, we decided to try vacuum to decrease hemodilution and to evaluate other possible benefits. Through the use of VAVR, we have been able to decrease our priming volume, use smaller venous cannulae, and have more consistent return while experiencing no adverse effects of VAVR in our pediatric cardiac surgery patients.

Impact of a remote pump head on neonatal priming volumes

Reduction of priming volumes of the cardiopulmonary bypass (CPB) circuit in neonatal cardiac surgery to decrease haemodilution and blood transfusion requirements can be achieved with the use of neonatal low prime oxygenators and smaller diameter tubing. We have further reduced our prime volume with the use of a custom-designed arm allowing for remote positioning of a double-headed roller pump. This arm enables the double pump to be placed alongside the main heart-lung machine close to the operating table, and to position the pump inlet and outlet tubing immediately at the reservoir outlet and oxygenator inlet, respectively, therefore reducing tubing lengths. Priming volumes of four cases using this configuration were compared to four cases using our standard neonatal bypass setup. Results showed a 29% decrease in priming volume and a 58% reduction in blood utilization during CPB. This reduction in priming volume is clinically significant as it lowers the ratio of priming volume to patient blood volume and reduces homologous blood requirements.