Investigation of possible prophylactic, renoprotective, and cardioprotective effects of thromboprophylactic drugs against ischemia-reperfusion injury

The aim of this study was to investigate whether anticoagulant and antiaggregant agents have protective effects against oxidative damage induced by peripheral ischemia-reperfusion (I/R). Groups were created as follows: control group, I/R group (sham group), I/R plus acetylsalicylic acid (Group I), I/R+clopidogrel (Group II), I/R+rivaroxaban (Group III), I/R+bemiparin sodium (Group IV), and I/R+enoxaparin sodium (Group V). In Groups I, II, III, IV, and V, drugs were administered daily for 1 week before I/R creation. Peripheral I/R was induced in the I/R groups by clamping the right femoral artery. The rats were sacrificed 1 hour after reperfusion. Nitrogen oxide levels, malondialdehyde (MDA) levels, paraoxonase-1 (PON1) activity, and prolidase activity were evaluated in both cardiac and renal tissues. There was no significant difference in nitrogen oxide levels between the groups. However, cardiac and renal MDA were significantly higher and PON1 activity was markedly lower in the I/R groups compared with the control group (p<0.05). Although elevated prolidase activity was detected in both the cardiac and renal tissue of the I/R groups, only the sham group and Group V had significantly higher renal prolidase activity (p<0.05). Group V had significantly higher cardiac MDA, PON1, prolidase levels, and renal prolidase activity compared with the sham group (p<0.05). Significant improvement in renal MDA levels was only observed in Group III, and marked improvement was observed in the cardiac MDA levels of Group II when compared with the sham group (p<0.05). Thromboprophylactic agents appear to provide partial or prominent protection against I/R injury.

Current state of medical thromboprophylaxis in Australia

BACKGROUND

Australia has two published national guidelines for general medical thromboprophylaxis (MT), but the two differ in detail and the basis for patient selection remains uncertain. Several aspects of current guidelines are controversial, as is the proposed design of a dedicated prescribing box in the National Inpatient Medication Chart.

AIM

To discuss and comment on the current standing of medical thromboprophylaxis in Australia.

METHOD

We have marshalled literature known to us from our previous published research, and have applied this knowledge to discuss shortcomings, which, in our opinion, exist in current medical thromboprophylaxis practice, and to suggest solutions.

CONCLUSION

Australian guidelines are flawed because they are based on unsuitable evidence (incidence of subclinical thrombotic disease) and define eligibility broadly, such that about 80 per cent of patients are considered eligible. They urge that prescribers should "consider" prophylaxis without supplying an adequate basis for doing so. They do not provide grounds for assessing the balance between hazard (in the form of major bleeds) and benefit (thrombotic events avoided). Other clinical factors promoting unnecessary use of medical thromboprophylaxis include the use of age as a risk factor and proposed inclusion of a new DVT prophylaxis section in the National Inpatient Medication Chart (NIMC), which implicitly discourages non-prescription of prophylaxis.

Measures of risk and their relationship to the relative size of a high-risk group: application to medical thromboprophylaxis

BACKGROUND

The aim of this study was to establish the meaning of "high-risk" when the subgroup so defined by risk factor analysis is a substantial proportion of the population. This is clinically important when patients, deemed to be at high risk as a result of risk factor analysis, become eligible for a clinical intervention to decrease the risk, especially if the intervention has adverse effects. One example in clinical practice is the assessment of eligibility for medical thromboprophylaxis.

METHODS

Equations were derived relating risk and the proportion of the population (F) deemed to be at high risk on risk factor analysis, based on the formula for weighted average. The equations were validated for the population of medical inpatients at high- or low-risk of thromobembolic events using a spreadsheet model of thrombosis risk containing known risk factors for venous thromboembolism in this population.

RESULTS

The validated equations define an upper limit of absolute and incremental risk (risk relative to the whole population) in the high-risk group that is a function of or equal to 1/F, respectively. The added risk in the high-risk group declines to zero as F tends to 1, because it must be balanced by the diminishing risk in the progressively smaller low-risk group while maintaining the population average.

CONCLUSION

The results of this study have implications for the validity of the published eligibility criteria for medical thromboprophylaxis.