Morphological Findings in Pancreatectomized Dogs with an Implanted Insulin Dosing Device: Tissue Reaction to the Pump Housing and to the Vascular Catheter

Summary

The foreign-body reaction to the pump housing and to the catheter in four pancreatectomized dogs in which a SIEMENS AG “DFA 1” type remote-controlled insulin dosing device had been implanted for between 4 to 8 months was examined in some detail.

The pump housing, made of titanium and the size of a cigarette packet, had been secured laterally to the 7th or 8th rib with two plastic strips. The insulin catheter (I.D. 0.3 mm, O.D. 0.7 mm) ran through a subcutaneous tunnel into the jugular vein. This 600-mm polyethylene catheter was encased in a 450-mm long silicone sheath (I.D. 0.5 mm, O.D. 1.0 mm) to prevent it from kinking. The final 150-160 mm of the catheter were not sheathed. A nylon flap was fitted 40-50 mm from the distal end of the silicone sheath. The catheter was inserted up to this flap in the jugular vein and was fastened securely by means of a modified purse-string suture.

In all animals, the intravascular silicone-sheathed part of the catheter and in one animal, a short portion of the unsheathed polyethylene part had become embedded into the vascular wall. In two animals, the remaining portion of the unsheathed polyethylene catheter was also adhering in places to the vascular wall. Again in two animals, old thrombi from lentil to bean-size were found at the sites of adhesion. In three dogs, the catheter tip was floating freely in the right artrium. The endocardium of the artrium and the cranial side of the tricuspid valves in some animals were covered with brownish deposits up to lentil-size corresponding histologically to a fibrosis of the endocard. In all animals, the lumen of the vein was open to the passage of blood. The subcutaneous portion of the catheter was unremarkable. A connective tissue capsule showing no signs of irritation but containing about 1 ml of sero-mucous transudate had formed around the pump housing.

The present findings corroborate the results obtained with indwelling catheters in the subclavian vein in intensive care patients. In view of the risk of thrombo-embolism, intraperitoneal administration of insulin would at present seem to be safer. However, we have meanwhile implanted the same type of pump subcutaneously without a catheter, the insulin being delivered into the connective-tissue capsule around the pump housing. Metabolic control with the catheterless pump is good.

Key-Words:

Implantable Insulin Device - Central Venous Catheter - Morphological Findings