Prophylactic intraoperative antithrombotics in open infrainguinal arterial bypass surgery: a systematic review

Unfractionated heparin (UFH) is used intraoperatively as antithrombotic by most vascular surgeons worldwide during infrainguinal bypass surgery (IABS) to reduce the risk of peroperative and early graft thrombosis. To reduce the harmful side effects of UFH (bleeding complications, HIT) and to reduce peroperative and early graft failure, other pharmaceuticals have been suggested for IABS. A systematic review was performed using MEDLINE, EMBASE and Cochrane databases. Only 9 studies on IABS and intraoperative antithrombotic use were eligible for review. Between studies heterogeneity was high and investigated study populations were often of small size. No study was retrieved comparing UFH to no-UFH. Dextran, human antithrombin and iloprost showed no beneficial effect compared to UFH alone for patency, mortality and morbidity. Low molecular weight heparin (LMWH) has potential benefits compared to UFH, but a statistically significant effect could not be demonstrated from the current review. The use of UFH during IABS to prevent intraoperative graft thrombosis has not been proven in randomized clinical trials. Dextran, human antithrombin and iloprost showed to be of no added beneficial effect for the patient compared to UFH alone. Data on the use of LMWH instead of UFH are promising, but no statistically significant benefit could be reproduced from literature. Results from a recent Cochrane review were favourable for LMWH, but it appeared that included data were not complete in that review. Randomized controlled trials are required for intra-operative use of antithrombotics and to improve peroperative and early patency after IABS.

Perioperative prophylactic antithrombotic strategies in vascular surgery: current practice in the Netherlands

AIM

The aim of this study was to evaluate the current practice of the use of perioperative antithrombotic drugs to prevent arterial thrombo-embolic complications during arterial vascular surgery by Dutch vascular surgeons. Aim was also to compare the results with the literature and to evaluate the effect of guidelines.

METHODS

A comprehensive questionnaire was sent to all Dutch vascular surgeons performing arterial reconstructive surgery.

RESULTS

The response rate was 84%. Acetylsalicylic acid (ASA) was continued perioperatively by most surgeons (91%). Clopidogrel was discontinued by the majority of respondents (65%). During operation 97% of surgeons administered unfractionated heparin (UFH) before arterial clamping. A minority (11%) measures peroperatively anticoagulant activity in patients' blood. After infrainguinal venous bypass most surgeons (81%) preferred monotherapy with vitamin K antagonists (VKA), in agreement with the Dutch guideline in this respect. Before the introduction of the guideline in 2005, a survey was performed in 2004. Results of our 2011 survey showed more respondents (6% to 11%) prescribed ASA or VKA according to these guidelines.

CONCLUSION

This survey showed a recognizable pattern of variation for perioperative arterial thrombosis prophylaxis amongst Dutch vascular surgeons, in agreement with reports from other countries over the past 20 years. Although a higher percentage of surgeons complied in 2011 with existing guidelines than in 2004, guidelines were not completely met. Possibly because current guidelines are not fully supported by evidence and do not cover all aspects of perioperative arterial thrombosis prophylaxis. Clearly there is need for (more) convincing data based on RCT's concerning the various aspects of perioperative arterial thrombosis prophylaxis.

Severe nasal clefting and abnormal embryonic apoptosis in Alx3/Alx4 double mutant mice

A group of mouse aristaless-related genes has been implicated in functions in the development of the craniofacial skeleton. We have generated an Alx3 mutant allele in which the lacZ coding sequence is inserted in-frame in the Alx3 gene and the sequences encoding the conserved protein domains are deleted. Mice homozygous for this null allele are indistinguishable from wild-type mice. Compound mutants of Alx3 and Alx4, however, show severe craniofacial abnormalities that are absent in Alx4 single mutants. Alx3/Alx4 double mutant newborn mice have cleft nasal regions. Most facial bones and many other neural crest derived skull elements are malformed, truncated or even absent. The craniofacial defects in Alx3/Alx4 double mutant embryos become anatomically manifest around embryonic day 10.5, when the nasal processes appear to be abnormally positioned. This most probably leads to a failure of the medial nasal processes to fuse in the facial midline and subsequently to the split face phenotype. We detected a significant increase in apoptosis localised in the outgrowing frontonasal process in embryonic day 10.0 double mutant embryos, which we propose to be the underlying cause of the subsequent malformations.

Targeted inactivation of Hoxb8 affects survival of a spinal ganglion and causes aberrant limb reflexes

Hoxb8 mutant mice were generated by inserting the lacZ coding sequence in frame with the first exon of Hoxb8. These mice express a fusion protein with a functional beta-galactosidase activity instead of Hoxb8. Mutant embryos were analyzed for anatomical changes. The results indicate that Hoxb8 is not an indispensable regulator of A-P patterning in the forelimb, unlike suggested by our Hoxb8 gain of function experiments (Charité J, DeGraaff W, Shen S, Deschamps J. Cell 1994;78:589-601). The null mutant phenotypic traits include degeneration of the second spinal ganglion (C2), an abnormality opposite to the alteration in the gain of function transgenic mice. Subtle changes in the thoracic part of the vertebral column were observed as well. Adult homozygous mutants exhibit an abnormal clasping reflex of the limbs.

Transient effects of microgravity on early embryos of Xenopus laevis

In order to study the role of gravity on the early development of the clawed toad Xenopus laevis, we performed an experiment on the Maser-6 sounding rocket launched from Kiruna (Sweden) on 4 Nov 1993. The aim was to find out whether a short period of microgravity during fertilization and the first few minutes of development does indeed result in abnormal axis formation as was suggested by a pilot experiment on the Maser 3 in 1989. On the Maser 6 we used two new technical additions in the Fokker CIS unit, viz. a 1-g control centrifuge and a video recording unit which both worked successfully. The 1-g control centrifuge was used to discriminate between the influences of flight perturbations and microgravity. After fertilization shortly before launch, one of the first indications of successful egg activation, the cortical contraction, was registered in microgravity and on earth. Analysis of the video tapes revealed that the cortical contraction in microgravity starts earlier than at 1 g on earth. After recovery of the eggs fertilized in microgravity and culture of the embryos on earth, the morphology of the blastocoel has some consistent differences from blastulae from eggs fertilized in the 1-g centrifuge of the rocket. However from the gastrula stage onward, the microgravity embryos apparently recover and resume normal development: the XBra gene is normally expressed, and histological examination shows normal axis formation.

Xenopus laevis embryos can establish their spatial bilateral symmetrical body pattern without gravity

One assumes that gravity cooperates with the sperm in the establishment of bilateral symmetry in the embryo, particularly in species with yolky eggs. However, only experiments under genuine microgravity can prove this. May 2nd 1988 on the TEXUS-17 Sounding Rocket, eggs of Xenopus laevis became the first vertebrate eggs ever successfully fertilized in Space. Fertilization was done in fully automated hardware; the experiment was successfully repeated and extended in 1989. Here we report a "Space First" from the IML-1 Space Shuttle mission (January 1992): In similar hardware and under microgravity, artificially fertilized Xenopus eggs started embryonic development. Histological fixation was pre-programmed at the time gastrulation would occur on Earth and indeed, gastrulae were fixed. Thus after fertilization in near weightlessness Xenopus embryos do develop bilaterally symmetrically, very probably cued by the sperm alone.