Photopheresis

Photopheresis is another variation of apheresis in which the white cell component is exposed to ultraviolet radiation ex vivo. In this technique, a photoactive dye such as psoralen (8-methoxypsoralen or 8 MOP) is taken by mouth. Several hours later, the apheresis procedure is performed. Ex vivo, the white cell component is separated and exposed to ultraviolet radiation causing drug activation. Although the precise mechanism of action is not understood, it is considered that the photochemical reaction causes both a cell membrane and a nucleic acid effect. The only clearly accepted indication for photopheresis is in the treatment of cutaneous T-cell lymphoma (CTCL) where dramatic remissions in skin lesions are often observed. There have been enthusiastic claims for the benefits of photopheresis in scleroderma, although a clear indication is uncertain at this time. Photopheresis has also been used in the prophylactic management of acute graft rejection in patients with cardiac transplantation, with recent evidence of benefit.

For all apheresis procedures, it is important to ensure good vascular access. Patients should be evaluated with regard to their fluid and hemodynamic status and level of hematocrit, as there may be a substantial extracorporeal volume depending on the devices used. Vascular access is a critical aspect and one which is often neglected by the requesting physician. If vascular access by peripheral veins cannot be assured, insertion of a large lumen intravenous line into the subclavian or femoral vein is best performed as soon as possible. This is particularly important in patients who will require repeated procedures such as in TTP, myasthenia gravis, or acute Guillain-Barre syndrome, etc. Despite the removal of large volumes of fluids and the ex vivo processing, therapeutic apheresis is usually well tolerated. Side effects are often limited to hypotensive episodes, easily managed by fluid infusion of 250-500 ml saline or episodes of nausea or chills. Allergic reactions occur with the plasma infusion in TTP and are a particular problematic in patients treated with staph protein A columns. These latter patients should not be taking angiotensin converting enzyme (ACE) inhibitors, as profound hypotension linked to bradykinin has been implicated. Allergic reactions are best managed with antihistamine given intravenously.

Table 40.3. Indications for photopheresis

(a) Cutaneous T-cell lymphoma (CTCL)

(b) Possibly, scleroderma

(c) Possibly, prophylaxis or treatment of allograft refection in patients postcardiac transplantation

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