Platelet inhibitors and hydroxyethyl starch: safe and cost-effective interventions in coronary artery surgery

The Safety of Continuing Antiplatelet Medication Among Elderly Patients Undergoing Urgent Hip Fracture Surgery

Elderly patients with hip fractures who are receiving antiplatelet therapy are commonly encountered in clinical practice. This study sought to elucidate the safety of urgent hip surgery without termination of antiplatelet medication among patients taking a combination of aspirin and dipyridamole, aspirin alone, or dipyridamole alone. This retrospective cohort study included 176 patients 55 years or older who had uncomplicated hip fractures and underwent surgery within 48 hours after admission. On the basis of the preoperative medication regimen, the patients were divided into the following 4 groups: those receiving aspirin and dipyridamole combined (n=29); those receiving aspirin alone (n=63); those receiving dipyridamole alone (n=28); and those not receiving antiplatelet medication (n=56). Main outcomes, including total blood loss, transfusion rate, and 1-year mortality, were analyzed. There was no significant difference in total blood loss, transfusion rate, or 1-year mortality among the 4 groups. The group receiving aspirin and dipyridamole combined preoperatively had increased intraoperative blood loss (mean, 309.14±189.15 mL) compared with the group not receiving antiplatelet medication (mean, 214.64±119.21 mL; P=.005). There was no significant difference in the hazard ratio (P>.05) for 1-year mortality among the 4 groups after adjusting for confounding covariates, including age, sex, Charlson Comorbidity Index, and duration of hospital stay. Patients receiving antiplatelet medication, including aspirin, dipyridamole, or both, who have uncomplicated hip fractures may undergo urgent surgery without a significant difference in total blood loss, transfusion rate, or 1-year mortality compared with patients not receiving anti-platelet medication. [Orthopedics. 2019; 42(5):268-274.].

Influence of different volume therapies on platelet function in the critically ill

OBJECTIVE

Both albumin and synthetic colloids such as hydroxyethyl starch (HES) solution are used to optimize hemodynamics in the critically ill. The influence of different long-term infusion regimes on platelet function was studied.

DESIGN

Prospective, randomized study.

SETTING

Clinical investigation on a university hospital surgical intensive care unit.

PATIENTS

Twenty-eight consecutive trauma patients (injury severity score > 15 points) and 28 consecutive nontraumatized surgical patients with sepsis.

INTERVENTIONS

The patients received either 20% human albumin (HA trauma, n = 14; HA sepsis, n = 14) or 10% low-molecular-weight HES solution HES 200/0.5 (HES trauma, n = 14; HES sepsis; n = 14) for 5 days to maintain central venous pressure and/or pulmonary capillary wedge pressure between 12 and 16 mmHg.

MEASUREMENTS AND RESULTS

Platelet function was assessed by aggregometry (= turbidimetric technique) using adenosine diphosphate 2.0 mumol/l, collagen 4 microliters/ml, and epinephrine 25 mumol/l as inductors. Arterial blood was sampled on the day of admission or the day of diagnosis of sepsis (= baseline value) and over the next 5 days. Standard coagulation parameters (antithrombin III, fibrinogen, partial thromboplastin time) were also measured. Total use of HES by the 5th day totalled 4870 +/- 990 ml in the trauma and 3260 +/- 790 ml in the sepsis patients (HA trauma: 1850 +/- 380 ml; HA sepsis: 1790 +/- 400 ml). Maximum platelet aggregation decreased significantly during the first 2-3 days after baseline in all groups. At the end of the investigation period, platelet aggregation variables had recovered and reached (or even exceeded) baseline values. Within the entire investigation period, the course of platelet aggregation variables did not differ significantly between HA and HES-treated patients irrespective of whether they were trauma or sepsis patients.

CONCLUSIONS

Alterations in hemostasis may occur for several reasons in the critically ill. Human albumin is the preferred first-line volume therapy in patients at risk for coagulation disorders. With respect to platelet function, volume replacement with (lower-priced) low-molecular-weight HES solutions can be recommended in this situation without any risk.

The use of hetastarch as adjunct therapy in 26 dogs with hypoalbuminemia: a phase two clinical trial

The purpose of this study was to evaluate the safety and efficacy of the synthetic colloid hetastarch in dogs with hypoalbuminemia. Individual doses of hetastarch ranged from 9 to 27 mL/kg, and multiple doses were used frequently. Total doses ranged from 9 to 59 mL/kg. Colloid oncotic pressure was measured in 13 dogs before and after treatment. Mean colloid oncotic pressure +/- SD was 9.32 +/- 2.35 mm Hg before treatment and 16.41 +/- 1.61 mm Hg in 8 healthy pet dogs used as controls. The difference in these values was significant (P < .001). There was a significant increase in mean colloid oncotic pressure after the first dose of hetastarch, but there was no relationship between the dose of hetastarch and the magnitude of increase in colloid oncotic pressure. Peripheral edema or body cavity transudates resolved or decreased in 83% of the dogs despite concurrent use of crystalloid fluid therapy. There was also no relationship between the dose of hetastarch and resolution of edema. Worsening of the results from coagulograms occurred in 5 of 18 dogs, and included increased prothrombin time (n = 1), increased partial thromboplastin time (n = 5), and decreased platelet count (n = 3). Bleeding that occurred in 3 dogs could not be directly attributed to the hetastarch. There was no relationship between the dose of hetastarch and worsening of the values in the coagulograms.

A cluster of severe postoperative bleeding following open heart surgery

OBJECTIVE

To investigate a cluster of postoperative bleeding following open heart surgery.

DESIGN

A cohort and case/control study.

SETTING

Palo Alto Veterans Administration Medical Center, Palo Alto, California.

PARTICIPANTS

Six (21.4%) of 28 patients undergoing open heart surgery who developed severe, nonsurgical, postoperative bleeding from July 1 through August 30, 1988 (outbreak period). All case-patients had chest tube drainage of greater than or equal to 1000 ml within 4 hours of surgery but did not have identifiable bleeding vessel(s) on exploration.

RESULTS

Upon comparison of the pre-outbreak (January 1986 through June 1988) and the outbreak period, a significant increase was found in the incidence of postoperative nonsurgical bleeding (5/440 versus 6/28, p = .0006), but not of postoperative surgical bleeding (8/440 versus 0/28, p = 1.0). Of all patients undergoing open heart surgery during the outbreak period, case patients were found to be older (67.8 versus 60.6, p = .02) and to have received a larger volume of hetastarch (HES), a synthetic colloidal plasma-volume expander (mean = 19.4 ml/kg versus 14.1 ml/kg, p = .02).

CONCLUSIONS

We conclude that the use of large volumes of HES during surgery in the elderly open heart surgery patient may increase the risk for severe, nonsurgical postoperative bleeding, probably caused by alterations of the coagulation system. As the incidence of open heart surgery increases among the elderly, surgeons and anesthesiologists should be alert to possible adverse reactions from exposures not associated with adverse reactions in younger patients.

Low-dose aspirin versus anticoagulants for prevention of coronary graft occlusion

The prevention of graft occlusion by aspirin (100 mg/day) or heparin followed by phenprocoumon was investigated in a randomized trial in 235 patients after aortocoronary bypass operation. Aspirin treatment started 24 hours before, and heparin 6 hours and phenprocoumon 2 days after surgery. The results of the vein graft angiography and the clinical outcome 3 months postoperatively did not differ: 22% of 218 vein graft distal anastomoses in the aspirin group and 20% of 272 in the anticoagulant group were occluded. At least 1 occluded distal anastomosis was present in 38% of 74 patients in the aspirin-treated group and in 39% of 86 in the anticoagulant group. Worst-case analysis of all randomized patients showed graft occlusions, cardiovascular complications or lost to follow-up in 42% of 122 aspirin-treated patients compared with 41% of 113 patients treated with anticoagulants. For grafts with endarterectomy the occlusion rate was lower in the aspirin (12% of 49) than in the anticoagulant (22% of 41) group (p less than or equal to 0.05). Increased perioperative blood loss in the aspirin group (1,211 +/- 814 ml in the first 48 hours vs 874 +/- 818 ml in the anticoagulant group [p less than or equal to 0.001]) without a higher reoperation rate indicates effective platelet inhibition with low-dose aspirin. Because occlusion rates were equal but high in these patients with advanced stage of coronary artery disease, a combination of low-dose aspirin and anticoagulation should be investigated to reduce graft occlusion rates further.

Blood-product usage in cardiac surgery

Many patients undergo cardiac surgery with preexisting congenital and acquired coagulation defects. Almost all of these can be recognized and corrected preoperatively. CPB itself induces a variety of abnormalities of coagulation, affecting plasma proteins, platelets, and the fibrinolytic system. These abnormalities do not always cause clinically significant bleeding. When they do, logical laboratory assessment and blood-component usage can usually correct the defect. The use of blood products is associated with allergic, viral, and hemolytic risks. Exciting advances have been made in the use of synthetic alternatives to blood products. Both DDAVP and aprotinin seem promising in this respect, but more investigation is needed into the mechanisms of action and possible thrombotic complications of these drugs. In the future, anesthesiologists and surgeons may look forward to more safe and effective therapy of bleeding in cardiac surgical patients.

Effects of hetastarch and albumin on coagulation in patients with septic shock

The effect of 6% hydroxyethyl starch (hetastarch) and 5% human serum albumin (albumin) infusion on coagulation in 12 patients with septic shock was evaluated. Patients were randomly assigned to receive either albumin (N = 6) or hetastarch (N = 6) infusion over a 24-hour study interval. The prothrombin time (PT), partial thromboplastin time (PTT), and quantitative platelet count (PC) were obtained prior to and following 24 hours of fluid infusion. Hetastarch patients received 4934 +/- 1354 mL and albumin patients received 3067 +/- 256 mL over the study interval. After hetastarch infusion, the PT increased 2.2 +/- 0.7 seconds, PTT increased 20.0 +/- 4.1 seconds (P less than .01), and PC decreased 158 +/- 36 X 10(3)/mm3 (P less than .02). After albumin administration, the PT decreased 1.2 +/- 1.7 seconds, PTT increased 20.5 +/- 10.6 seconds and PC decreased 100 +/- 34 X 10(3)/mm3. There were no significant differences in the changes in PT, PTT, or PC between the groups. The authors conclude that hetastarch infusion does not result in increased bleeding in patients with septic shock compared with albumin infusion, despite moderate effects on the hemostatic coagulation profile.