Can Remote Ischaemic Preconditioning Reduce Contrast Induced Nephropathy in Patients Receiving Contrast for Computed Tomography?

Computated tomography (CT) is an invaluable medical resource for both physicians and surgeons. Contrast media are an aid to improve the diagnostic yield of CT. While an incredibly powerful means of imaging the human body, there are possible complications to the use of contrast including a hypersensitive response and contract induced nephropathy (CIN). The latter will typically occur 48-72 hours after administration.

One recent meta - analysis of serum creatinine levels following contrast enhanced CT found 6.4% of those undergoing this investigation developed CIN. Although typically transient, 1 % had a persisting reduced renal function, with a small minority needing renal replacement therapy (RRT). The development of CIN was influenced by co morbidities and by the amount of contrast given.

The mechanism of injury to the kidney is not definitively established, but is thought most likely due to hypoxia resulting from reduced blood flow, thereby giving rise to oxygen free radicals causing direct damage to the kidney and also direct tubular damage.

Remote conditioning ischaemia has been hypothesized to be nephroprotective, whereby induced transient ischaemia at another site could buffer the impact of the contrast medium's effects. This was first demonstrated during cardiac angiograms, with those patients whom received multiple balloon inflations in the coronary arteries were found to have a lower incidence of CIN than those with fewer balloon inflations. Thus it could be hypothesised that any ischaemia temporarily induced could be nephroprotective. This can be at a point of extremity, rather than involving central organs, such as the arm, with ischaemia induced by the use of a blood pressure cuff, inflated to above systolic blood pressure levels.

No studies have been found in the literature attempting to demonstrate this effect in relation to contrast CT studies. Consequently, a randomised control clinical trial of patients to assess the effectiveness of remote ischaemic preconditioning is proposed.

Study Hypothesis: That performing remote ischaemic preconditioning on those undergoing CTs involving IV contrast is nephroprotective.