A cohort study of coagulation parameters and the use of blood products in surgery of the thoracic and thoracoabdominal aorta

Severe platelet transfusion refractoriness after thoracoabdominal aneurysm repair

Severe thrombocytopenia after thoracoabdominal aortic aneurysm repair poses a significant clinical risk in the immediate postoperative period. Understanding the mechanisms of refractoriness to platelet transfusion is relevant to supporting thrombocytopenic patients postoperatively. We present the case of a 76-year-old woman with refractory thrombocytopenia secondary to alloimmunization following open repair of a Crawford extent IV thoracoabdominal aneurysm. The patient provided written informed consent for the report of her case details and imaging studies.

Acute normovolemic hemodilution can aggravate neurological injury after spinal cord ischemia in rats

BACKGROUND

Acute normovolemic hemodilution (ANH) is currently performed during thoracoabdominal aortic surgery. However, the effects of ANH on spinal cord ischemic injury are currently unknown. Because hemodilution below a certain level of hematocrit (Hct) aggravates the neurological damage after cerebral ischemia, we hypothesized that ANH may increase neurological damage after spinal cord ischemia. The aim of these experiments was to determine the effects of ANH on spinal cord ischemic injury.

METHODS

Thirty male Sprague-Dawley rats were randomly assigned to 1 of the following 3 groups: no hemodilution (group C), target Hct level of 30% (group HD30), and target Hct level of 25% (group HD25). ANH was performed upon withdrawal of blood and simultaneous replacement with the same volume with hydroxyethyl starch. Spinal cord ischemia and reperfusion were induced by using a balloon-tipped catheter placed in the descending thoracic aorta, and changes in mean arterial blood pressure were recorded. Neurological function of the hindlimbs was evaluated for 7 days and recorded using a motor deficit score (MDS) (0 = normal; 5 = complete paraplegia). The number of motor neurons within the spinal cord was counted after final MDS evaluation.

RESULTS

Group HD25 developed hypotension during the latter part of the ANH procedure. Group C and group HD30 experienced 3 minutes of reperfusion hypotension, whereas 6 minutes of hypotension was observed in group HD25. Two rats in group HD25 died during the experimental period. Seven days after reperfusion, the MDS of group C, group HD30, and group HD25 was 1.0 (0.5-2.0), 1.0 (0.5-2.0), and 4.0 (2.8-4.2) (median [95% confidence interval]), respectively. Group HD25 showed significantly higher MDS compared with group C (corrected P = 0.0018; 95% CI for median difference = 1.0-3.5). Motor neuron numbers in the anterior horns of group C, group HD30, and group HD25 were 26.5 (25.0-27.5), 23.5 (22.0-26.5), and 12.5 (8.4-16.6) (median [95% CI]), respectively. Motor neuron numbers of group HD25 were significantly lower than those of group C (corrected P < 0.0001; 95% CI for median difference = 9.0-18.0).

CONCLUSION

The results of the present study indicate that intraoperative ANH to an Hct of 25%, combined with coincident hypotension, caused a delayed recovery of baseline mean arterial blood pressure during the reperfusion period and aggravated neurological outcome after spinal cord ischemia.

Peri-operative blood management in elective orthopaedic surgery. A critical review of the literature

Blood loss during orthopaedic procedures can be extensive and the need for allogeneic blood is a common requirement. However, blood transfusion conceals a number of well-recognised risks and complications and blood products have become more expensive because of their specific preparation procedure. Surgical technique, awareness of the problem and restriction of transfusion triggers are important factors affecting the management of blood loss. Several studies have additionally shown the efficacy of epoetin injections in increasing the pre-operative haemoglobin level. On the other hand, the true benefit of pre-operative autologous donation, acute normovolemic haemodilution and COX-2 selective NSAIDs remains under dispute. Regarding the role of platelet rich plasmapheresis, fibrin sealing and anti-fibinolytic drugs more data are needed. Hypotensive epidural anaesthesia seems to be an advantageous method in minimising peri-operative blood loss. However, this is not a widely performed technique in orthopaedic surgery. In addition, post-operative blood cell saving systems after total knee or hip arthroplasty have been reported to significantly minimise allogeneic blood transfusions when compared to control groups. It can be concluded that many interventions diminish more or less allogeneic blood transfusion in elective orthopaedic surgery. Nevertheless more prospective studies are needed and appropriate algorithms should be applied in peri-operative blood loss management. This review presents an overview of the available interventions which aim to diminish the use of allogeneic blood in elective orthopaedic surgery.

The Resuscitative Fluid You Choose May Potentiate Bleeding

BACKGROUND

Trauma is the leading cause of death in the younger population in the United States, frequently from the development of hemorrhagic shock. Controversy exists over the type of volume resuscitation for restoring hemodynamic stability that should be used in hemorrhagic shock. Little is known about how various resuscitative paradigms affect the coagulation cascade, which is essential to controlling hemorrhagic shock.

METHODS

We studied the effect of various resuscitative formulas on blood coagulation using a new model of whole blood in a controlled setting with corn trypsin inhibitor and a 5-pM stimulus of tissue factor. We investigated thrombin generation, fibrin formation, and platelet activation with four diluents: 0.9% NaCl (NS), lactated Ringer's solution (LR), 6% hydroxyethyl starch (HES), and 3% NaCl (HS), each from 0% to 75% blood dilution. Thrombin generation was measured periodically during a time course of 20 minutes in its complex with antithrombin III. Platelet activation and fibrinopeptide A (FPA) release were monitored in serum at a 20-minute time point. Fibrin clots were collected and weighed.

RESULTS

The coagulation markers (thrombin generation, platelet activation, and FPA release) were significantly different by dilution (p < 0.001 in all) and diluent by dilution (p < 0.001 in all). Thrombin generation, platelet activation, and FPA release decreased the least with the diluents NS and LR. LR caused the least amount of variation in thrombin generation over the dilution course. HS produced the most dramatic change in all of the markers; no coagulation was seen between 30% to 75% dilution (p < 0.05). HES produced greater decreases in thrombin generation and FPA release than NS and LR. Fibrin clot mass decreased with a 10% to 20% dilution for NS and LR, whereas stable fibrin mass did not decrease with the diluents HES and HS at 10% to 20% dilutions. At >30% dilutions, HS produced no stable clots and HES dramatically decreased clot formation by 61% and maintained this level.

CONCLUSIONS

LR and NS had the least effect on thrombin generation, clot formation, and platelet activation at various concentrations compared with HES and HS. This observational data suggests that volume expanders such as HES and HS may be detrimental in treatment of hemorrhagic shock.

Acute diastolic dysfunction in thoracoabdominal aortic aneurysm surgery

PURPOSE

To report transesophageal echocardiographic (TEE) findings consistent with intraoperative acute diastolic dysfunction in a series of patients undergoing thoracoabdominal aortic aneurysm (TAAA) repair.

METHODS

A series of nine consecutive patients underwent TAAA repair with intraoperative TEE monitoring. Surgical repair was performed with the adjunct of a left atrio-femoral bypass. Invasive arterial and venous pressures were monitored. Intraoperative TEE was utilized to assess the diastolic function before, and during aortic cross clamping. Diastolic dysfunction was defined as a mitral inflow pulsed wave Doppler (E: A ratio) < 1.

RESULTS

All patients demonstrated an E: A ratio > 1 (1.3 +/- 0.08) before aortic cross clamping. During cross clamp, the E: A ratio decreased to < 1 (0.75 +/- 0.05) in six of nine patients consistent with diastolic dysfunction. The three patients who did not develop E: A changes were receiving ss-blockers pre-operatively. Patients with diastolic dysfunction were treated with nitroglycerin infusions, which resulted in restoration of their E: A ratios > 1 (1.2 +/- 0.09). Three of the patients with intraoperative diastolic dysfunction developed postoperative myocardial infarction.

CONCLUSIONS

Chronic diastolic dysfunction is a well-known entity. This report describes acute diastolic dysfunction, which was observed frequently in patients undergoing TAAA during aortic cross clamp. Further research is required to confirm this phenomenon and determine its possible association with increased postoperative cardiac morbidity.

Coagulation Disorders and Blood Product Use in Patients Undergoing Thoracoabdominal Aortic Aneurysm Repair

Repair of thoracoabdominal aortic aneurysms (TAAA) is associated with major blood loss, often exceeding the patient's intravascular volume, and complex intraoperative and postoperative coagulopathies necessitating large-volume transfusion of blood products. Abnormalities sufficient to cause thrombocytopenia or clinically important prolongation of clotting parameters are rarely present before surgery in elective aneurysms but are more common with ruptured aneurysms. The finding of intraoperative and postoperative deficiencies of clotting factors, along with thrombin generation and activation of the thrombolytic system, is reflective of massive blood losses, visceral ischemia, and massive transfusions. An aggressive strategy of transfusion of blood products is critical to the prevention of clinically significant coagulopathy during surgery. Adjuncts to reduce blood losses and blood product use include low-dose aprotinin or epsilon -aminocaproic acid, intraoperative blood salvaging, and acute normovolemic hemodilution. In TAAA repair, an average blood loss of 5000 to 6000 mL and average transfusion of allogeneic blood products of 50 to 60 U are to be anticipated.

A mathematical model of cell salvage compared and combined with normovolemic hemodilution

BACKGROUND

Mathematical models have been used to describe the factors that affect cell salvage (CS) and normovolemic hemodilution (ANH). Here, the CS and ANH models were used to compare these two techniques alone or in combination with each other.

STUDY DESIGN AND METHODS

Variables used for a hypothetical patient included an estimated blood volume of 5000 mL, a presurgery hematocrit (Hct) of 45 percent, and a transfusion trigger of 21 percent. The model accounts for both the effect of decreasing the Hct due to blood loss and the effect of increasing Hct due to the readministration of blood in an isovolemic patient. The efficacy of CS and ANH is defined to be the maximum allowable blood loss for a fixed blood volume and a fixed transfusion trigger.

RESULTS

Comparison of CS with ANH showed that 3 units of ANH was comparable to CS when CS recovery rates ranged from 19 to 24 percent. For a patient with a blood volume of 5000 mL and a starting Hct of 40 percent, 3 units of ANH would allow for 3972 mL of blood to be lost before crossing a 21-percent transfusion trigger, whereas CS with a 125-mL bowl would allow for 7611 mL.

CONCLUSION

When comparing ANH to CS, this mathematical model would suggest that CS has the potential to offer significantly greater red blood cell avoidance than does ANH; however, the combination of ANH with CS may offer allogeneic avoidance superior to either technique alone.

Blood saving protocol in elective total knee arthroplasty

BACKGROUND

To eliminate the need for allogeneic blood transfusion in patients undergoing elective total knee arthroplasty, we established and tried a protocol of combined methods, which is characterized by effectiveness, ease in application, and safety. It is based on perioperative administration of human recombinant erythropoietin plus iron and folic acid, mild acute normovolemic hemodilution, meticulous surgical technique, postoperative blood salvage through a closed-wound drainage system, and lower transfusion triggers.

DATA SOURCES

Sixty-one patients entered the protocol, and the results were retrospectively compared with the ones obtained from 58 consecutive patients who were operated on in the past before the use of any blood saving technique.

CONCLUSIONS

Only 5 patients of those who entered the protocol finally needed allogeneic blood transfusion, receiving a total number of 7 units, which is remarkable when compared with the 50 patients before the application of the protocol who required 111 units. Consequently, the utilization of allogeneic blood was reduced by 94%, a statistically quite significant result (P <0,001). We believe the protocol should be included in orthopedic surgeons' alternatives for blood saving in elective total knee arthroplasty.

Thoracoabdominal aortic aneurysm repair: a prospective cohort study of 121 cases

Between October 1990 and June 2001, 121 patients underwent surgery for thoracoabdominal aortic aneurysm (TAAA)-99 procedures were elective and 22 were for ruptured aneurysms. Between October 1990 and September 1997, the clamp-and-go technique was used for all aneurysms (43 patients), and from October 1997, clamp-and-go was reserved for type IV TAAAs, and atriofemoral bypass (AFB) was used for types I, II, and III (78 patients). Overall hospital mortality was 21.4% (26/121)-12% for the elective group and 64% for the ruptured group. Hospital mortality was associated with age (67 years in survivors vs. 73 years in nonsurvivors, p = 0.03), FEV1<2 L (RR 4.1, p = 0.01), CSF drainage (RR 5.0, p = 0.03), type II aneurysms vs. other aneurysms (RR 3.7, p = 0.02), and relative inexperience (mean rank in the series was 52 in survivors vs. 30 in nonsurvivors, p = 0.01). The overall incidence of neurologic deficits due to spinal cord ischemia was 6.2% (paraplegia in 4.4%). Temporary dialysis was necessary in 13% of patients, and chronic dialysis in 2%. In long-term follow-up of patients undergoing elective repair, 5-year survival was 80% and median survival was 7.9 years. Mortality and neurologic deficits have improved over time as a consequence of either increased surgical experience, the adoption of a protocolized strategy for repair, or secular improvements in ICU care. Long-term survival after elective TAAA repair is excellent.