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Biomedical subjects

W G Parkin

Publications and source records attributed to W G Parkin.

11 recordsLinked to original sources
PubMed1991

Three dimensional closed loop control of the human circulation.

In the control of the circulation it is suggested there is merit in describing states which are the object of each therapy. Considering the determinants of venous return rather than those of cardiac output, we suggest that the mean systemic filling pressure is a parsimonious description of the volume state. A method is described of deriving a mean systemic filling pressure analogue based on stopping the flow in a notional regional systemic circulation. The mean systemic filling pressure (PM) forms a quantitative link between volume therapy and circulatory dynamics. The systemic vascular resistance is a conventional measure of the state of arteriolar resistance. We suggest that the ratio (PM - PRA)/PM (where PRA is the right atrial pressure) is a global measure of the effect of cardioactive drugs. Studies are reported in which the mean blood pressure, right atrial pressure and cardiac output are simultaneously controlled within desired tolerances using state based control.

Blood Circulation↗
PubMed1987

The use of electrical conductivity measurement in the calculation of ion-free water loss in urine.

The urine electrical conductivity is a practical guide to the ion-to-water ratio of urine. It may be used to assess the influence of urinary loss upon the total body ion-to-water ratio. It is suggested that the total body ion-to-water ratio is the object of control in water therapy, commonly administered as 5% dextrose. The total body ion-to-water ratio closely accords with the ratio in the extracellular fluid. Since sodium is the predominant extracellular cation, the plasma sodium concentration closely reflects the extracellular and total body ion-to-water ratio. As a consequence the urine electrical conductivity may be used as a continuous signal in the open or closed loop control of water balance as reflected by the plasma sodium concentration.

Critical Care↗
PubMed1985

Charcoal hemoperfusion treatment of severe theophylline toxicity.

A 38 year old man was admitted eight hours after taking ten grams of theophylline. The plasma concentration of theophylline on admission was 732 mumol/l. In view of the patient's continuing clinical deterioration, charcoal hemoperfusion was undertaken. This led to a rapid fall in plasma theophylline concentrations and improvement in clinical signs. It is suggested that charcoal hemoperfusion has a role in the severely theophylline toxic patient in whom standard conservative measures are failing. The patient's hyperglycemia, metabolic acidosis, and hypokalemia are discussed.

Adult↗
PubMed1982

An 8-year prospective experience with balloon tamponade in emergency control of bleeding esophageal varices.

The use of balloon tamponade in the emergency control of bleeding from esophageal varices is controversial. This paper reports a prospective study over an 8-year period in which balloon tamponade has been the sole means employed for the early control of bleeding varices. During 1972-1980 all patients referred to Prince Henry's Hospital with upper gastrointestinal bleeding were admitted to a special unit. Ninety-one had bleeding esophageal varices, and 17 were admitted on one or more occasions for bleeding for a total of 132 admissions. After early endoscopy, balloon tamponade was used during 103 of these admissions with failure to control bleeding on six occasions; five of these patients died from hemorrhage and the sixth recovered after emergency portacaval shunt. Another patient died from rebleeding not treated by tamponade. Reinsertion of the balloon for rebleeding was necessary on 28 occasions with successful control in all cases. Balloon tamponade was not used during 29 admissions because bleeding had ceased or the patient was considered to have terminal liver disease. In this group there were four deaths from severe liver disease and hemorrhage. Balloon tamponade was used in 78% of admissions and controlled bleeding in more than 90% of patients. This suggests that tamponade may be the method of choice early control of bleeding from esophageal varices.

Adult↗
PubMed1982

The patient/computer interface--a problem area.

In disease states, loss of homeostatic control may be countered by the provision of external inputs or therapy. Where the variables of interest may change rapidly and respond predictably to therapy, a patient/computer interface may be used to enhance data collection and/or in the formation of appropriate therapeutic responses. Ultimately, if appropriate dynamic responses are achieved, the patient therapy loop may be closed. Realisation of problem-free interfaces requires careful design of input transducers, computing hardware and software, output therapeutic devices and their integration. This process will require ingenuity, engineering competence and a thorough understanding of medicine and the clinical environment. In addition to sound technological solutions, the designer must be cognisant of the human aspects, for both patient and user of interface operation.

Computers↗
PubMed1979

Successful treatment of ergotamine poisoning with sodium nitroprusside.

A case of ergotamine overdosage which produced vascular insufficiency in a 26-year-old female is described. She was treated successfully with the intravenous infusions of sodium nitroprusside and low molecular weight dextran, and anticoagulation with heparin. It is suggested that sodium nitroprusside may represent the drug of first choice in this condition.

Adult↗
PubMed1977

Use of a microprocessor in the control of malignant hypertension with sodium nitroprusside.

In a malignant hypertensive, steady control of blood pressure at a pre-determined level has been achieved with the continuous intravenous infusion of sodium nitroprusside. A microprocessor was programmed to assess the patient's blood pressure and adjust the rate of nitroprusside infusion so that a mean pressure of 106 mmHg was achieved. Brief interruption of the nitroprusside infusion allowed the effectiveness of changes in oral therapy to be evaluated. Thiocyanate concentrations were measured throughout as an index of potential nitroprusside toxicity. After six days, blood pressure control was maintained with oral therapy alone and papilloedema had almost resolved.

Adult↗