Avoiding coagulopathy in vascular surgery

Application of controlled hypotension combined with autotransfusion in spinal orthomorphia

Background:

Idiopathic scoliosis is a common spinal deformity in teenagers, which is managed mainly by orthomorphia. However, due to great trauma, long operative duration and large blood loss, a great amount of blood transfusion is needed during the surgery. Allogeneic blood transfusion should be reduced in order to release blood insufficient, decline blood transfusion expense, as well as avoid transfusion diseases.

Objective:

The objective of the following study is to investigate the value of controlled hypotension combined with autotransfusion in idiopathic scoliosis orthomorphia and in order to reduce surgical bleeding and reduction in blood transfusion.

Subjects and Methods:

Intra-operative controlled hypotension was performed during posterior orthomorphia surgery on all the 46 cases of idiopathic scoliosis, 17 cases in which were served as the control group, who underwent allogeneic blood transfusion without autotransfusion, whereas the other 29 cases were served as the experimental group, who underwent autotransfusion that including reinfusion of pre-operative deposited autologous blood and intra-operative salvaged autologous blood. The blood loss volume and transfusion status in two groups were observed.

Results and Conclusion:

Blood loss volume in the control group was 400-1000 (835.3 ± 167.5) mL and that in the experimental group was 350-1400 (812.1 ± 152.7) mL, there was no marked difference between the two groups (P > 0.05). The volume of allogeneic blood transfusion in the control group was 500-1800 (855.9 ± 321.1) mL, which was greater than that in the experimental group ((0-1300 (337.9 ± 258.3) mL) (P < 0.01). The results suggested that controlled hypotension reduces intraoperative bleeding and post-operative autotransfusion minimizes the need of allogeneic blood transfusion.

Epidural cooling for the prevention of ischemic injury to the spinal cord during aortic occlusion in a rabbit model: determination of the optimal temperature

PURPOSE

This experiment was designed for the determination of the optimal epidural cooling temperature for the allowance of spinal cord protection with minimal side effects during an aortic occlusion-induced spinal cord ischemia model in rabbits.

METHODS

Spinal cord ischemia was induced in rabbits with infrarenal aortic occlusion for 40 minutes. Spinal cord cooling was effected with epidural infusion of normal saline solution at the following different temperatures: group 1, 17 degrees C (n = 6); group 2, 24 degrees C (n = 6); group 3, 32 degrees C (n = 6); and group 4, 39 degrees C (n = 3). Sham-operated rabbits without aortic occlusion were used as controls with epidural infusion at healthy body temperature (39 degrees C; n = 3). Motor function was assessed at 48 hours with Tarlov's criteria, and the animals were killed. The spinal cord was sectioned into multiple segments, and semiquantitative histologic scoring (0 to 5) was used to grade ischemic injury.

RESULTS

Cooling solution and spinal cord temperatures showed linear correlation (r = 0.95). All the rabbits in groups 1 (except one with mild weakness), 2, and 3 were neurologically intact, and all in group 4 had paraplegia develop (P < .001). One rabbit in group 1 died from increased intracranial pressure (ICP). Mean blood pressure, ICP, and body temperature were similar among the groups. Histology correlated with the clinical findings. In groups 1 and 2, minimal histologic changes were noted. Low-grade ischemic changes were present in group 3 in the low-lumbar and mid-lumbar segments. Severe ischemic injury occurred at the same segments in group 4 (P < .05).

CONCLUSION

These study results suggest that in rabbits satisfactory spinal cord protection during aortic occlusion can be achieved at moderate regional hypothermia (24 degrees C). Large volume infusion for the achievement of profound hypothermia may cause deleterious effects of increased ICP and is not warranted.

Intraoperative use of platelet-plasmapheresis in vascular surgery

STUDY OBJECTIVE

To determine, in a pilot study, whether pheresis of plasma and platelets before surgical blood loss, with reinfusion of the autologous plasma and platelets after completion of the aortic reconstruction, will result in decreased bleeding and decreased transfusion of allogenic blood components in patients undergoing elective aortic reconstruction.

DESIGN

Randomized study.

SETTING

University medical center.

INTERVENTIONS

Patients were randomized to perioperative (acute) platelet plasmapheresis (APP group) versus conventional blood component therapy (control group). In the APP group, blood was withdrawn after induction of anesthesia, to sequester approximately 300 mL of platelet rich plasma (PRP); platelet poor plasma (PPP) and red blood cells (RBC) were sequestered as well. An autotransfusion device was used to collect and re-infuse autologous RBC during the course of the operation in both groups. After completion of the aortic reconstruction, autologous PRP and PPP were re-infused in the APP group. Blood loss, volume of blood component transfusions, and preoperative and postoperative hemoglobin (Hb), hematocrit (Hct), platelet, international normalized ratio (INR), and activated partial thromboplastin time (aPTT) were recorded.

MEASUREMENTS AND MAIN RESULTS

There was no difference between groups in demographics, preoperative laboratory values, or surgical procedures, although more patients were treated for aneurysms (73% vs. 60%) and fewer for occlusive disease (20% vs. 40%) in the control versus APP group. Also, there were no differences between the control and APP groups in duration of operation, blood loss, volume of colloid infused, or volume of allogenic RBC and plasma transfused. Patients in the APP group received a greater volume of crystalloid solution (9.1 +/- 3.4 L vs. 6.8 +/- 3.0 L; p = 0.002), but fewer units of allogenic platelets than the control group (0.7 +/- 1.0 units vs. 0.2 +/- 0.4 units; p < 0.04). There were no differences in postoperative Hb, Hct, INR, aPTT, or fibrinogen. The platelet count was lower in the APP group than in the control group (123 +/- 40 x 10(3)/mm(3) vs. 182 +/- 51 x 10(3)/mm(3); p = 0.004).

CONCLUSIONS

Perioperative platelet plasmapheresis led to fewer allogenic platelet transfusions in patients undergoing elective aortic reconstruction. However, there was no decrease in blood loss and no reduction in transfusion of allogenic RBC or plasma. Perioperative platelet plasmapheresis is not recommended for routine use in elective aortic reconstruction.

Is the "salvaged-cell syndrome" myth or reality?

BACKGROUND

Intraoperative autotransfusion (IAT) has been implicated in anecdotal cases and experimental models to precipitate, aggravate, or exacerbate a coagulopathy. This study assesses this hypothesis.

METHODS

A retrospective database review of over 36,000 multispecialty cases of IAT during an 18-year experience was conducted with special reference to the occurrence of coagulopathy (disseminated intravascular coagulation [DIC]) in association with adult respiratory syndrome (ARDS).

RESULTS

The incidence of coagulopathy was low (0.05%). A total of 18 cases of DIC/ARDS were identified: 10 associated with ruptured aneurysms, 6 following massive trauma, and 2 after complex redo cardiac surgery. All 18 patients suffered shock and profound hypothermia. The mean transfusion requirement was 28 units. The mortality was 100%.

CONCLUSION

Although some degree of bleeding and clotting disorders are not uncommon in major cases, in our experience coagulopathy occurs infrequently and is a result of a complex interaction of shock, hypothermia, and multiple transfusions. It is our contention that these factors trigger the DIC, not the autotransfusor, and that the ARDS results from reperfusion injury following a profound ischemic event, associated in many cases with multiorgan failure.

Autologous fibrin glue: the last step in operative hemostasis

BACKGROUND

Fibrin glue may be the perfect hemostatic agent for operative use as it seals in minutes, has no tissue toxicity, reabsorbs, and promotes local tissue growth and repair. Use in the United States has been limited because of lack of Food and Drug Administration approval of the commercial homologous products, lack of a concentrated source of fibrinogen, and because of the potential for viral transmission, particularly hepatitis, with pooled homologous plasma and cryoprecipitate-based methods. Autologous fibrin glue (AFG) obviates these problems.

METHODS

During the past year, we obtained AFG through the same routine predonation procedure as with red blood cells before major elective surgery. Intraoperatively, we made AFG from the platelet-rich plasma derived from the Plasma-Saver. Our experience has been with 36 patients undergoing aortic, thoracoabdominal, and thoracic surgery, as well as patch graft angioplasty cases.

RESULTS

Fibrin glue formation mimics the final stage in the coagulation cascade. The AFG from predonation acts more like an epoxy glue, while the AFG made during surgery is less viscous and acts more like a sealant because of the lesser concentration of fibrinogen in platelet-rich plasma. In emergencies, however, the intraoperative method is obviously the only choice available, and it is a useful adjunct to hemostasis at the end of the procedure. The technique will be described.

CONCLUSION

This relatively new approach to hemostasis should gain popularity because it is easy and fairly inexpensive to produce, and because the patient's own blood is used.

Protecting the ischemic spinal cord during aortic clamping: the influence of selective hypothermia and spinal cord perfusion pressure

PURPOSE

We verified the hypothesis that selective deep hypothermia of the spinal cord during double thoracic aortic clamping can prevent postoperative paraplegia in dogs.

METHODS

Normal saline solution was circulated from the cisterna magna through an extracorporeal perfusion system consisting of a reservoir, a pump, and a heat exchanger, back into the subarachnoid space at the level of the medullary cone at a rate of 25 ml/min, starting 30 minutes before clamping, and ending after removal of the clamps. The thoracic aorta was cross-clamped below the left subclavian artery and above the diaphragm for a period of 45 minutes. Cerebrospinal fluid, intracranial, and central venous pressure and aortic pressure proximal, between, and distal to the clamps were continuously recorded. In five dogs, temperature of the circulating normal saline solution at the inflow level was maintained at 2 degrees +/- 1.5 degrees C (group 1), in five controls at 37 degrees +/- 0.8 degrees C (group 2). Five dogs underwent continuous cerebrospinal fluid drainage starting before clamping until sacrifice (group 3). Dogs were observed for up to 4 days, and neurologic function was graded by an independent observer with the Tarlov scale. Animals were then killed, and their spinal cords were prepared for microscopic examination.

RESULTS

Hemodynamic parameters were not significantly different between groups. All dogs in groups 2 and 3 were paraplegic with histologic evidence of spinal cord infarction. All animals in group 1 were neurologically normal without microscopic evidence of infarction (p < 0.005).

CONCLUSIONS

Selective deep hypothermia of the spinal cord prevents paraplegia after 45 minutes of double aortic clamping in dogs. Cerebrospinal fluid drainage was not effective in preventing paraplegia in this model.

Hypothermia and bleeding during abdominal aortic aneurysm repair

Patients undergoing abdominal aortic aneurysm repair routinely have a depressed core body temperature during surgery, and hypothermia is known to cause abnormalities in coagulation. This study was designed to determine whether platelet function is altered as a result of hypothermia or heparin during abdominal aortic aneurysm repair. Ten patients scheduled for abdominal aortic aneurysm surgery were prospectively studied. Bleeding times and temperature were measured every hour beginning preoperatively. Each patient was heparinized intraoperatively, and the effects reversed with protamine sulfate prior to closure. Despite efforts to keep the patients warm, all of them developed hypothermia (mean lowest core temperature 34.8 +/- 0.7 degrees C). A significant linear relationship between the change in core temperature and the change in bleeding time was demonstrated. In 7 of 10 cases the greatest change in bleeding time occurred when patients experienced the lowest mean core temperature and not when they were heparinized. These data suggest that hypothermia has a marked effect on platelet function during abdominal aortic aneurysm repair. Although heparin can cause abnormalities in platelet function, hypothermia may be a more important role in inhibiting normal platelet function. By preventing severe hypothermia (< 35 degree C), excessive bleeding associated with abdominal aortic aneurysm repair may be minimized without the concomitant risk of blood product transfusion.

Transfusion and surgery

In this survey of transfusion in surgery, we have attempted to provide the surgeon with an understanding of the problems associated with homologous transfusion and a practical knowledge of treatment strategies and alternatives designed to reduce homologous blood exposure. Such a review cannot be encyclopedic. Our hope is that it will serve the reader as a stimulus to examine his or her transfusion practices and as a guide for future self-learning.

Preoperative plateletpheresis does not reduce blood loss during cardiac surgery

Acute preoperative plateletpheresis has been reported to be effective in reducing blood loss and blood component transfusion while improving haematological profiles in patients undergoing open-heart surgery. However, in these studies, the concomitant use of cell saver techniques may have been responsible for the beneficial effects because they remove free haemoglobin and activated procoagulants and, therefore, could mask the deleterious effects of combined plateletpheresis and cardiopulmonary bypass (CPB). In the present study, 40 patients undergoing primary myocardial revascularization were randomly divided into two groups: a control group without plateletpheresis performed, and a second group in which preoperative platelet-rich plasma 10 ml.kg-1 (PRP group) was collected and later reinfused after reversal of heparin. Standardized surgery, anaesthesia and CPB without concomitant cell saver techniques were employed. In the PRP group, blood transfusion was reduced (1.5 +/- 1.3 vs 2.4 +/- 1.3 units, P < 0.05) but this was accompanied by lower postoperative haemoglobin concentrations. There were no differences in blood loss (992.6 +/- 327.4 vs 889.6 +/- 343.7 ml), fresh frozen plasma (2/19 vs 3/20 patients) or platelet requirements (1/19 vs 1/20 patients). Reinfusion of autologous PRP did not improve platelet count and function, nor tests of coagulation. Fibrinogen concentrations were lower in the PRP group on the operative day (P < 0.05), suggesting increased fibrinogen consumption; and more patients in the PRP group had low haptoglobin levels during CPB (8/19 vs 0/20 patients, P < 0.005), which indicated greater haemolysis in this group. We conclude that acute preoperative plateletpheresis offers no advantage in haemostasis during elective primary myocardial revascularization surgery.