Insulin infusion pumps in the treatment of diabetes

The long-term complications of diabetes mellitus remain a serious public health problem in the Western nations. Much current research focuses on methods of insulin treatment designed to provide near-normal glycemic control throughout the day with the intention of preventing or delaying the onset of the angiopathic consequences of preventing or delaying the onset of the angiopathic consequences of diabetes. Recent work has shown that open-loop insulin infusions (that is, insulin administered by an infusion pump without feedback control) can result in near-normal blood glucose levels in juvenile-onset or Type I diabetics. The extracorporeal infusion pumps used in such studies have their won physical and psychological drawbacks, however. More recent studies have attempted similar degrees of control using totally implantable insulin infusion pumps; several such studies are being carried out in patients with adult-onset or Type II diabetes, the predominant type of diabetes afflicting the elderly.

Intraarterial infusion chemotherapy for hepatic carcinoma using a totally implantable infusion pump

Intraarterial infusion chemotherapy has several theoretical advantage over conventional therapy for the treatment of unresectable malignancies. However, the catheter problems and patient restriction to the hospital associated with its use have resulted in infrequent application and a notable lack of progress in this field of oncology. This paper describes the use of a totally implantable, percutaneously refillable infusion pump in 5 patients with primary or metastatic carcinoma of the liver. The infusion cannulae were placed into the hepatic arteries under direct vision at laparotomy, and the pumps were placed in subcutaneous pockets. Four patients received infusions of 5-fluorodeoxyuridine at rates of 0.2-0.5 mg/kg/day for periods of three to 29 weeks; the pump in the fifth patient was defective and was removed. The implanted pumps were well tolerated in these subjects, who received chemotherapy as outpatients; the only adverse effects noted were related to FUDR toxicity. This implantable infusion pump appears to be a practical means of delivering long-term intraarterial infusion chemotherapy to outpatients.

An implantable pump for long-term intravascular drug infusion

A totally implantable infusion pump has been developed that can provide chronic, continuous, low-rate drug infusions in ambulatory patients. The device relies on vapor pressure for its power source, and thus needs no recharging other than periodic drug refills. It is implanted surgically under the skin of the chest or abdomen, with the delivery cannula placed in an appropriate blood vessel. Pumps implanted in this way have delivered heparin, 5-fluorodeoxyuridine, or other drugs in patients; some outpatients have received continuous intravenous heparin infusions for more than 4 years.

Rates of triacylglycerol entry into the circulation in the lactating rat

The rate of entry of triacylglycerols into the circulation in lactating rats decreased after parturition and increased in mid-lactation. The decrease in entry rate after parturition may contribute to the disappearance of the hyperlipaemia of pregnancy. A method is described for the determination of the rate of entry in vivo of both triacylglycerols and lipid synthesized de novo.

Long-term, continuous intravenous heparin administration by an implantable infusion pump in ambulatory patients with recurrent venous thrombosis

We studied the effect of long-term intravenous heparin infusion, delivered by a self-recycling, totally implantable infusion pump developed in our laboratory, in 21 patients with recurrent thromboembolic disease. Continuous infusions were maintained in these patients from 1 to 36 months, during which pumps were refilled by percutaneous needle injection at 4- to 8-week intervals. We maintained plasma heparin levels between 0.1 and 0.3 U/ml plasma. This regimen prevented thromboembolic phenomena in all except one patient, who apparently is refractory to heparin as well as oral anticoagulant drug therapy. Marked reduction of pain and improvement of mobility were reported by several patients with vena cava ligature syndrome. No spontaneous hemorrhagic complications occurred; however, several episodes of pump site hemorrhage were associated with pump refills. Bone mineral densities measured in eight subjects after 1 year of heparin infusion [1.00 +/- 0.06 (SE) gm/cm] were not significantly (P = 0.5) different from baseline values (0.98 +/- 0.08 gm/cm); however, osteoporosis did occur in one subject. Serum calcium, phosphorus, alkaline phosphatase, cholesterol, and triglycerides also remained unchanged in these subjects. These data suggest that continuous long-term heparin infusion is a viable therapeutic alternative in subjects with refractory thromboembolic disease.

Transbrachial hepatic arterial chemotherapy using an implanted infusion pump

Two patients with hepatic metastases from colonic cancer were treated with hepatic arterial FUDR using an innovative drug infusion system. The two patients reported underwent transbrachial hepatic artery catheterization with a 5 French polyethylene catheter. This catheter was amputated just distal to its exit from the brachial artery and attached to a totally implantable, percutaneously refillable drug infusion pump placed in the infraclavicular position. The patients received FUDR at flow rates of 3--4 ml/day. The pumps were refilled weekly by percutaneous injection. One patient was treated for seven weeks, and another for ten weeks without technical difficulties. This innovative approach offers marked improvement in comfort and convenience for patients who are candidates for long-term hepatic artery chemotherapy, and avoids the morbidity of laparotomy for direct hepatic arterial catheterization.

A totally implantable drug infusion defice: laboratory and clinical experience using a model with single flow rate and new design for modulated insulin infusion

The Infusaid implantable infusion pump with a single delivery rate has maintained chronic intravenous heparin infusion in man for greater than 35 mo and for greater than 5 yr in the dog. Intra-arterial infuson of fluorodeoxyuridine has been maintained for greater than 8 mo in man. In a pilot study using a commercially available, transcutaneously controllable, magnetically activated valve for baseline superimposed bolus insulin infusion, the feasibility of maintaining near normal serum glucose in diabetic dogs was demonstrated. The effect of long-term intravenous cannulation was investigated; it was found that the intimal tissues of the vena cava surrounding the cannulae were largely unaltered and microemboli could not be detected in the lungs of the animals studied. Cannula plugging, which occurred on several occasions due to thrombus formation in the final centimeter of the cannula, has been solved by changes in pump design and refilling procedures. The problem of insulin precipitation in flow passages of the pump remains unsolved, but there are indications that substances entering the cannula from the blood may be involved. A new pump design for modulated insulin infusion is described.

Intraarterial infusion chemotherapy for hepatic carcinoma using a totally implantable infusion pump

Intraarterial infusion chemotherapy has several theoretical advantage over conventional therapy for the treatment of unresectable malignancies. However, the catheter problems and patient restriction to the hospital associated with its use have resulted in infrequent application and a notable lack of progress in this field of oncology. This paper describes the use of a totally implantable, percutaneously refillable infusion pump in 5 patients with primary or metastatic carcinoma of the liver. The infusion cannulae were placed into the hepatic arteries under direct vision at laparotomy, and the pumps were placed in subcutaneous pockets. Four patients received infusions of 5-fluorodeoxyuridine at rates of 0.2-0.5 mg/kg/day for periods of three to 29 weeks; the pump in the fifth patient was defective and was removed. The implanted pumps were well tolerated in these subjects, who received chemotherapy as outpatients; the only adverse effects noted were related to FUDR toxicity. This implantable infusion pump appears to be a practical means of delivering long-term intraarterial infusion chemotherapy to outpatients.

The implantable infusion pump: a new concept in drug delivery

Several of our most useful drugs cannot be administered orally. This paper is a summary of our work with a new drug delivery system: a totally implantable, continuous infusion pump, with a self-contained inexhaustible power source. Currently, after bench tests and animal experimentation, we have initiated clinical series utilizing this device to treat individuals with refractory thromboembolic conditions by intravenous heparin, and patients with localized solid tumors by intra-arterial chemotherapy. The use of this device for the infusion of insulin in the management of diabetes mellitus is yet in the laboratory stage of development. In addition to improving dy-today diabetic control and obviating the need for daily insulin injections, this pump offers an ideal opportunity to test whether optimal blood glucose control can significantly prevent or delay the onset of the crippling vascular complications of diabetes. The potential uses of this device, in many fields, are myriad.

Control of blood glucose in experimental diabetes by means of a totally implantable insulin infusion device

Near-normal glucose tolerance tests in diabetic dogs were obtained during basal rate insulin infusions in restrained animals by use of extracorporeal infusion pumps and in conscious, unrestrained animals by means of implanted infusion pumps. Even better regulation of blood glucose in diabetic animals was obtained by the addition of predetermined pulses of insulin at higher flow rates than the basal flow rate, accomplished by use of a transcutaneously activated valve mechanism attached to the implanted infusion pump. We conclude that near-normal blood glucose concentrations can be maintained throughout the day in the dog by these means and that similar approaches, using implantable infusion pumps, in man may lead to better long-term control of diabetes than is currently available.

The effect of continuous heparin infusion for one year on serum cholesterol and triglyceride concentrations in the dog

Fourteen normal dogs received continuous infusions of intravenous heparin for one year by means of an implantable infusion pump. Heparin wad admistered at an overall mean rate of 666 units/kg/day, a dose sufficient to prolong the Lee-White clotting time to greater than twice normal. Eight control, animals, under the same dietary and activity regimen, received continuous infusions of bacteriostatic water for one year by means of implanted pumps. Serum cholesterol concentrations rose to 50% above control values after one month of heparin infusion, and remained significantly (P less than 0.05) elevated at this level for the remaining 11 months. Serum triglyceride levels were unchanged. A possible mechanism for this elevation resides in the known effect of heparin to increase plasma free fatty acid concentrations by its activation of lipoprotein lipase. These results may have implications for the long-term use of heparin anticoagulation in the treatment of atherosclerotic states in man.

Protracted parenteral drug infusion in ambulatory subjects using an implantable infusion pump

This study demonstrates the feasibility of ambulatory heparin therapy and its potential for successful treatment of refractory thromboembolic disease. The proven capability of the implantable infusion pump to provide long-term heparin infusion in ambulatory subjects suggests that it may have application in the delivery of other parenteral drugs as well.

Factors regulating amino acid release from extrasplanchnic tissues in the rat. Interactions of alanine and glutamine

1. Factors regulating the release of alanine and glutamine in vivo were investigated in starved rats by removing the liver from the circulation and monitoring blood metabolite changes for 30 min. 2. Alanine and glutamine were the predominant amino acids released into the circulation in this preparation. 3. Dichloroacetate, an activator of pyruvate dehydrogenase, inhibited net alanine release: it also interfered with the metabolism of the branched-chain amino acids valine, leucine and isoleucine. 4. L-Cycloserine, an inhibitor of alanine aminotransferase, decreased alanine accumulation by 80% after functional hepatectomy, whereas methionine sulphoximine, an inhibitor of glutamine synthetase, decreased glutamine accumulation by the same amount. 5. It was concluded that: (a) the alanine aminotransferase and the glutamine synthetase pathways respectively were responsible for 80% of the alanine and glutamine released into the circulation by the extrasplanchnic tissues, and extrahepatic proteolysis could account for a maximum of 20%; (b) alanine formation by the peripheral tissues was dependent on availability of pyruvate and not of glutamate; (c) glutamate availability could influence glutamine formation subject, possibly, to renal control.

The effects of inhibition of gluconeogenesis on ketogenesis in starved and diabetic rats

Experiments were performed in which the effects of inhibiting gluconeogenesis on ketone-body formation were examined in vivo in starved and severely streptozotocin-diabetic rats. The infusion of 3-mercaptopicolinate, an inhibitor of gluconeogenesis (DiTullio et al., 1974), caused decreases in blood [glucose] and increases in blood [lactate] and [pyruvate] in both normal and ketoacidotic rats. Patterns of liver gluconeogenic intermediates after 3-mercaptopicolinate infusion suggested inhibition at the level of phosphoenolpyruvate carboxykinase. This was confirmed by measurement of hepatic oxaloacetate concentrations which were increased 5-fold after 3-mercaptopicolinate administration. The infusion of 3-mercaptopicolinate caused a decrease in total ketone-body concentrations of 30% in starved rats and 73% in the diabetic animals. Blood glycerol and hepatic triglyceride concentrations remained unchanged. The decreases in ketone-body concentrations were associated with increases in the calculated hepatic cytosolic and mitochondrial [NADH]/[NAD+] ratios. The decrease in ketogenesis seen after inhibition of gluconeogenesis may have resulted from an inhibition of hepatic fatty acid oxidation by the more reduced mitochondrial redox state. It was concluded that gluconeogenesis may stimulate ketogenesis by as much as 30% in severe diabetic ketoacidosis.

Sequential amino acid measurements during experimental diabetic ketoacidosis

This study was designed to investigate the sequential amino acid response to acute insulin deprivation. Male Wistar rats were made severly diabetic by the intravenous injection of streptozotocin, 150 mg/kg, and maintained on insulin for 7 days. Insulin was then withheld, and measurememts of whole blood and plasma amino acid concentrations were made at 24-h intervals until 120 h, by which time animal mortality was 80%. Alanine and the other gluogenic amino acids displayed a biphasic response to insulin deprivation, decreasing in plasma and whole blood until 72 h after the last insulin injection then increasing in concentration until 120 h. The branched-chain amino acids valine, leucine, and isoleucine remained constant until 72 h after insulin, after which time their concentrations increased dramatically. It was concluded that the first phase represented enhanced gluconeogenesis and in the second phase amino acid uptake for gluconeogenesis was exceeded by net peripheral amino acid release. Enzymatic measurements showed a progressive increase in erythrocyte;plasma distribution ratios for glutamate in ketoacidosis.

The metabolic effects of sodium dichloroacetate in the starved rat

1. Sodium dichloroacetate (300mg/kg body wt. per h) was infused in 24h-starved rats for 4h. 2. Blood glucose decreased significantly, an effect that had previously only been noted in diabetic animals 3. Plasma insulin concentration decreased by 63%; blood lactate and pyruvate concentrations decreased by 50 and 33%, whereas concentrations of 3-hydroxybutyrate and acetoacetate increased by 81 and 73% respectively. 4. Livers were freeze-clamped at the end of the 4h infusion. There were significant decreases in hepatic [glucose], [glucose 6-phosphate], [2-phosphoglycerate], the [lactate]/[pyruvate] ratio, [citrate] and [malate], and also [alanine], [glutamate] and [glutamine], suggesting a diminished supply of gluconeogenic substrates. 5. Animals subjected to a functional hepatectomy at the end of 2h infusions showed no difference in blood-glucose disappearance but a highly significant decrease in the rate of accumulation of lactate, pyruvate, glycerol and alanine, compared with control animals. Dichloroacetate decreased ketone-body clearance. 6. After functional hepatectomy an increase in glutamine accumulation appeared to compensate for the decrease in alanine accumulation. 7. It is concluded that dichloroacetate causes hypoglycaemia by decreasing the net release of gluconeogenic precursors from extrahepatic tissues while inhibiting peripheral ketone-body uptake. 8. These findings are consistent with the activation of pyruvate dehydrogenase (EC 1.2.4.1) in rat muscle by dichloroacetate previously described by Whitehouse & Randle (1973).

Experimental diabetic ketoacidosis. Sequential changes of metabolic intermediates in blood, liver, cerebrospinal fluid and brain after acute insulin deprivation in the streptozotocin-diabetic rat

Male rats rendered diabetic by the intravenous injection of streptozotocin (150mg/kg) were treated with a long-acting insulin for 1 week, then allowed to develop ketoacidosis. By using sampling techniques designed to avoid the use of anaesthesia and extended anoxic periods, sequential measurements of metabolic intermediates were made in blood, liver, cerebrospinal fluid and brain at 24h intervals after the last insulin injection. Measurements in blood and liver suggested a rapid increase in hepatic glycogenolysis and gluconeogenesis and peripheral-depot lipolysis between 24 and 48h after the last insulin injection, whereas blood and liver ketone-body and triglyceride concentrations rose more slowly. The changing metabolic patterns occurring with increasing time of insulin deprivation stress the importance of sequential compared with static measurements in experimental diabetes. Data are presented for brain metabolic intermediates in diabetic ketoacidosis, and support recent evidence that glucose plays a less important role in brain oxidative metabolism in ketotic states.