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.

Distance stereo acuity improvement in intermittent exotropic patients following strabismus surgery.

To determine whether distance stereo acuity improved following strabismus surgery in patients with intermittent exotropia, we tested 20 patients (5 to 87 years old) preoperatively and postoperatively using the Mentor BVAT II Video acuity tester (Santa Barbara, Calif) and binocular visual system. Acuity improved in 75% as assessed by contour circles and in 45% as assessed by random dot E tests at distance. Our results suggest that surgical realignment of intermittent exotropia restores distance stereo acuity. We conclude that measuring distance stereo acuity offers valuable information in the evaluation of the intermittent exotropic patient.

Some regulatory properties of pea leaf carbamoyl phosphate synthetase.

Carbamoyl phosphate synthetase of pea shoots (Pisum sativum L.) was purified 101-fold. Its stability was greatly increased by the addition of substrates and activators. The enzyme was strongly inhibited by micromolar amounts of UMP (Ki less than 2 mum). UDP, UTP, TMP, and ADP were also inhibitory. AMP caused either slight activation (under certain conditions) or was inhibitory. Uridine nucleotides were competitive inhibitors, as was AMP, while ADP was a noncompetitive inhibitor. Enzyme activity was increased manyfold by the activator ornithine. Ornithine acted by increasing the affinity for Mg.ATP by a factor of 8 or more. Other activators were IMP, GMP, ITP, and GTP, IMP, like ornithine, increased the Michaelis constant for Mg.ATP. The activators ornithine, GMP, and IMP (but not GTP and ITP) completely reversed inhibition caused by pyrimidine nucleotides while increasing the inhibition caused by ADP and AMP.

Pea leaf glutamine synthetase: regulatory properties.

Of a variety of purine and pyrimidine nucleotides tested, only ADP and 5'AMP significantly inhibited the Mg(2+)-dependent activity of pea leaf glutamine synthetase. They were less effective inhibitors where Mn(2+) replaced Mg(2+). They were competitive inhibitors with respect to ATP, with inhibition constant (Ki) values of 1.2 and 1.8 mm, respectively. The energy charge significantly affects the activity of glutamine synthetase, especially with Mg(2+). Of a variety of amino acids tested, l-histidine and l-ornithine were the most inhibitory, but significant inhibition was seen only where Mn(2+) was present. Both amino acids appeared to compete with l-glutamate, and the Ki values were 1.9 mm for l-histidine (pH 6.2) and 7.8 mm for l-ornithine (pH 6.2). l-Alanine, glycine, and l-serine caused slight inhibition (Mn(2+)-dependent activity) and were not competitive with ATP or l-glutamate.Carbamyl phosphate was an effective inhibitor only when Mn(2+) was present, and did not compete with substrates. Inorganic phosphate and pyrophosphate caused significant inhibition of the Mg(2+)-dependent activity.

In Vitro Synthesis of Ureidohomoserine by an Enzyme from Jack Bean (Canavalia ensiformis) Leaves.

An enzyme was extensively purified from jack bean leaves (Canavalia ensiformis L.) which produced o-ureidohomoserine from l-canaline and carbamyl phosphate. The most highly purified preparations catalyzed both this reaction and citrulline synthesis from ornithine and carbamyl phosphate, and the ratio of the two activities remained nearly constant during purification. When hydrated jack bean seeds were the enzyme source, ornithine carbamyltransferase (EC 2.1.3.3) activity was high but synthesis of ureidohomoserine was barely detectable. Both ornithine carbamyltransferase and the ureidohomoserine synthesizing enzyme had similar Km values for carbamyl phosphate. The purification data suggest that one enzyme may catalyze both reactions in jack bean leaves.

Partial purification and properties of carbamoyl phosphate synthetase of Alaska pea (Pisum sativum L. cultivar Alaska).

1. Carbamoyl phosphate synthetase was purified up to 45-fold from Alaska pea seedling (Pisum sativum L. cultivar Alaska). 2. The enzyme was most active with and had the lowest K(m) for l-glutamine as compared with NH(4) (+). 3. The purest preparations utilized very poorly or not at all l-asparagine and urea as nitrogen donors. 4. At saturating concentrations of components of the reaction, the K(m) for l-glutamine was 1.2x10(-4)m, and the K(m) for ATP was approx. 3.9x10(-4)m. 5. Although the enzyme was very labile, stability was improved by glutamine, asparagine, ammonium sulphate, dithiothreitol and especially l-ornithine. 6. Free ATP was markedly inhibitory, and MgATP(2-) and Mg(2+) appeared to be the actual substrates utilized. 7. Fe(2+) and Mn(2+) were also utilized, but not as readily as Mg(2+) except at low concentrations. K(+) increased activity significantly. 8. Of the four nucleotides tested (ITP, ATP, GTP and UTP) only ATP served as an effective phosphate donor.