An Introduction to Dialysis for Non-Renal Clinical Engineering Technicians.

Part 1

Introduction

The role of the clinical engineering technician is broad and diverse, providing an interface between technology, clinicians, nursing staff and patients. For example, the clinical engineering technician ensures that all electro-medical equipment for use on patients complies to National and International standards, thus ensuring the safety of the patient, the user and the environment. In the dialysis unit the clinical engineering technician, dialysis or renal technician deals with safety, electronics, computers, hydraulics, mechanics, water sampling, and supporting the ancillary equipment which may be used in the unit such as infusion devices, ECG machines, and defibrillators. In this area of operation an understanding of the clinical application of the equipment or device is essential. Problem solving and fault finding are examples of areas made easier by understanding the clinical application of the equipment. Communications with the nursing, medical and technical staff is vital to the smooth running of the department from an engineering perspective. The renal technician must ensure that the down time of vital equipment is minimised and that safety is foremost at all times. As an engineer with twenty years experience in Healthcare Engineering I was surprised by the steep learning curve I faced when introduced to this new area of responsibility. Engineering in a Dialysis unit is a challenging and interesting one, working closely with clinical, nursing and technical staff as well as patients. This paper was written to provide an informative overview of some of the interesting areas of dialysis for engineering technicians not familiar with this area of work.

The purpose of Dialysis

Acute renal failure is defined as a sudden decrease in renal function resulting in the retention of urea nitrogen and creatinine in the blood. The origin of kidney disease may be infectious, genetic, traumatic, immunologic, metabolic, or degenerative (Brenner & Rector,1986). As creatinine is primarily eliminated by glomerular filtration, it is the most convenient laboratory value for assessing renal function.

Some patients develop acute renal problems and are treated as emergencies and require dialysis as part of their acute medical management, others with chronic renal impairment are treated as part of a planned renal dialysis programme. Only as a last resort where kidney disease has progressed to renal failure, after intensive pharmacological, fluid or electrolyte therapies will Patients with renal failure be put on dialysis. Dialysis is intended to re-establish the body's fluid and electrolyte balance. It allows toxic waste products to be removed from the blood. Patients have benefited greatly in recent years from the technological advancements in the area of dialysis.

A History of Dialysis

The concept of cleaning the blood of toxic substances while removing excess water by a membrane process was first suggest by the experiments of Able, Rowntree, and Turner at the John Hopkins Medical School back in 1913. They demonstrated the feasibility of blood dialysis to balance plasma solute concentrations with those imposed by an appropriately formulated washing solution. Their observation was not followed by clinical application due perhaps to the difficulty of fabricating suitable exchange membranes. (The Biomedical Engineering Handbook ) However in 1854 Thomas Graham F.R.S. 1805-1869 the invited speaker at The Bakerian Lecture presented a paper titled "On Osmotic Force" in which he stated that these principles might be applied to medicine.

The first animal dialysis took place in 1913. The first human dialysis on a patient was performed in 1926. Major problems occurred due to coagulation of the blood. Before 1916 Hirudin extracts from the siliva of leeches was the only practical anticoagulant. Insufficient purification caused major side effects and allergic reaction. Hirudin was first identified in 1884.

In 1916 McLean isolated heparin as a naturally occurring mammalian anticoagulant. Haas used heparin in animal experiments. The use of heparin in human medicine became a standard after appropriate purification technology was available in 1937 (Murray et.al ). In the series reported by Professor Georg Haas in his paper published in 1928 "About Blood Washing " there were no surviours of his treatment. Willem Kolff's 17th patient a 67 year old female was admitted to Kampen hospital on September 3rd 1945 with acute renal failure. She fully recovered after one week of dialysis and died at the age of seventy three from an unrelated disease.

In the Netherlands during 1944 Kolff designed his own kidney machine for use on human patients with acute renal failure. The device consisted of a long segment of cellophane sausage tubing coiled around a drum rotating in a thermostablised bath filled with hypertonic buffered electrolyte solution, called dialysate. Blood was allowed to flow from a vein into the coiled cellophane tube. Water and solute exchange occurred through the membrane with a warm dialysate pool, which had to be renewed every few hours because of the risk of bacterial growth. The blood was returned to the patients circulation by means of a pump.

During the Korean war "Mobile Army Surgical Hospitals" units used the Kolff- Brigham artificial kidney in the battle field. Seventy two treatments were carried out on thirty one patients. Eight out of ten patient's died with post traumatic renal insufficiency despite intensive modern therapy.

Frank Kelly IEng. MIHEEM
Clinical Engineering Department
St. Vincent's University Hospital, Dublin