A rapid bedside method of monitoring blood glucose in diabetic hyperglycemia.
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Autoanalysis↗
Biomedical subjects
A D Stephens
Publications and source records attributed to A D Stephens.
Rapid identification of hemoglobin variants by electrospray ionization mass spectrometry.
The precise identification of human hemoglobin variants, over 700 human hemoglobin variants are known, is essential for prediction of their clinical and genetic significance. A systematic approach to their rapid identification is described. Traditionally this requires protein or DNA characterization which entails lengthy analytical procedures. To overcome these obstacles a rapid approach to variant hemoglobin identification has been developed using conventional phenotypic methods combined with electrospray ionization-mass spectrometry (ESI-MS). The latter requires only a small amount of whole blood (10 microl) but in most cases 2 microl would have been sufficient and no preanalytical steps, such as separation of red cells or globin chains, are necessary. Aged, hemolyzed blood samples can also be analyzed. This approach has been used to positively identify 95% of the variants in over 250 samples. The remaining 5% in which a variant was detected by phenotypic techniques were not resolved by mass spectrometry. Ninety-nine different abnormalities comprising 36 alpha-chain variants, 59 beta-chain variants (including 2 extensions), and 4 hybrid hemoglobins were identified. These include 15 novel variants. The application of ESI-MS described requires approximately 1 h to prepare and analyze each sample and has minimal reagent costs. The turnaround time on a single sample can be as little as 2 h. This technique can now be considered a useful additional tool for reference laboratories.
Amino Acid Substitution↗
The potential of electrospray ionization mass spectrometry for the diagnosis of hemoglobin variants found in newborn screening.
Analytical procedures have been developed for the detection and diagnosis of sickle cell disease in newborn babies by analyzing the hemoglobin extracted from dried blood spots on Guthrie cards using electrospray ionization mass spectrometry (ESI-MS). An essential requirement is the ability to reliably differentiate two globin chains whose molecular weights differ by only 1 Da such as adult hemoglobin (Hb A) and Hb C. This has been achieved by improving the accuracy and precision of the molecular weight determination to a fraction of a dalton. We report the potential of mass spectrometry for screening neonates for these debilitating diseases by presenting results from 147 blood spots that had been characterized by phenotypic methods and which include samples from 20 sickle cell disease, 1 beta-thalassemia major, 57 sickle cell trait, and 39 normal babies. In all cases, the mass spectrometric results agreed with the results obtained using conventional analytical practice with high-performance liquid chromatography (HPLC) and isoelectric focusing (IEF). We show that mass spectrometry is a viable technique for the diagnosis of newborns with sickle cell disease or homozygous beta0-thalassemia.
Anemia, Sickle Cell↗
Radiofrequency hyperthermia in the palliative treatment of mucinous carcinomatosis of appendiceal origin: optimizing and monitoring heat delivery in western patients.
Mucinous peritoneal carcinomatosis from a primary gastrointestinal malignancy is a lethal condition that has few treatment options with the use of surgery, chemotherapy or radiation therapy. Recent advances in hyperthermia technology and in knowledge of the natural history of this disease has suggested the possible utility of hyperthermia in the application of aggressive local-regional therapy. Radiofrequency (RF) hyperthermia to the whole abdomen, to the hemithorax, or to an isolated mucinous tumour deposit obstructing the gastrointestinal tract was used in patients with disseminated mucinous adenocarcinoma of appendiceal origin. There were 228 hyperthermia treatments in 21 patients, with a median of 10 treatments per patient. The maximum number of treatments was 26, and minimum was one. For the first six hyperthermia treatments, escalating doses of deep hyperthermia (41-45 degrees C) was monitored with multiple sensor internal temperature probes and a single sensor subcutaneous temperature probe. After reaching a maximal hyperthermia treatment, this was maintained for all subsequent treatments. Initially, the maximal temperature allowed in tumour and subcutaneous tissue was 43 degrees C. After 50 hyperthermia treatments, this was changed to 45 degrees C. If disease stabilization or response was insufficient and maximal tolerable hyperthermia had been established, the frequency of treatment was increased from every 4 weeks to every 2 weeks, and escalating doses of mitomycin C at 8 mg/m2 were added to the regimen. Mitomycin C was infused during the hyperthermia treatment. For the first 165 treatments, patients were monitored just before and 10 days after hyperthermia with a complete blood count and a full battery of laboratory tests including amylase and lipase. Response was monitored by carcinoembryonic antigen assays on a monthly basis and CT scans on a 6 monthly basis. None of the 21 patients included in this study died, required intensive care, or required major surgical interventions as a result of hyperthermia treatments. One potentially life-endangering event was profound bradycardia and hypotension observed in a 76-year-old male receiving hyperthermia treatment to his right hemithorax. Two patients developed an enterocutaneous fistula (a frequent spontaneous event in this group of patients) while under treatment. No abnormal laboratory tests were observed in the first 165 hyperthermia treatments. Heat damage to normal tissue was limited to skin blisters in three patients and induration of the subcutaneous tissues in 10 patients. Skin pain on an analogue scale of 0-10 was scored by patients as a mean of 3.6 (range 0-8) before skin analgesia was routinely utilized. With anesthetic gel, the skin discomfort was greatly reduced. Prolonged abdominal pain for 4-20 days following treatment which required narcotic analgesia was seen in four patients. A complication rate of 62% was caused by the long-term indwelling temperature probe sheaths. Infection was observed in four patients, small bowel fistula in one, and dislodgement of the temperature probe sheath requiring repeat CT was necessary in seven patients. After maximal escalation of RF power in seven patients (33%), deep hyperthermia compatible with thermal destruction of tumour (> or = 43 degrees C for 45 min) was recorded in all subsequent treatments. In eight patients (38%), heat generation compatible with chemotherapy augmentation (41.5-43 degrees C) was consistently recorded. In six patients, non-therapeutic temperatures were recorded. There was no correlation of maximal tumour temperature, maximal subcutaneous tissue temperature and maximal RF power. With the use of skin anaesthetic there was no correlation of tumour temperature and the thickness of the subcutaneous layer of the skin. Progression was seen in 14 patients, and 11 of these patients died. No patients who showed disease stabilization have died with a minimum of 2 year follow-up. (ABSTRACT TRUNCATED)
Adenocarcinoma, Mucinous↗
Heated intraoperative intraperitoneal mitomycin C and early postoperative intraperitoneal 5-fluorouracil: pharmacokinetic studies.
PURPOSE: The purpose of this study was to report the pharmacokinetics of heated intraoperative intraperitoneal mitomycin C (MMC) and to analyze the impact of heat, extent of peritoneal resections, and effect of intraoperative hyperthermic chemotherapy on the pharmacological properties of the peritoneal plasma barrier. METHODS: Sixty patients with peritoneal carcinomatosis were included in a phase I/II study combining cytoreductive surgery with 2 h of heated intraperitoneal mitomycin C in an intraoperative lavage technique and one cycle of early postoperative 5-fluorouracil (5-FU) given on postoperative days 1-5. Three pharmacokinetic analyses were performed: (1) pharmacokinetics of heated intraoperative intraperitoneal MMC was determined for 18 patients by sampling peritoneal fluid, plasma, and urine during the 2-h procedure; (2) impact of peritoneal resections on MMC pharmacokinetics was assessed by comparing a group of patients who underwent < or = 1 peritonectomy procedure (minimal surgery) to a group of patients who underwent > or = 2 peritonectomy procedures (extensive surgery), and (3) effects of heated intraoperative intraperitoneal chemotherapy on the pharmacokinetics of early postoperative intraperitoneal 5-FU by comparing a group of patients treated with heated intraoperative intraperitoneal MMC to a control group who did not receive heated intraoperative intraperitoneal chemotherapy. RESULTS: The mean dose of heated intraoperative intraperitoneal MMC per patient was 22.5+/-7.1 mg (12.9+/-3.8 mg/m2). Drug absorption from perfusate was 14.3+/-2.7 mg. The mean aeras under the curve (AUC) for perfusate and plasma were, respectively, 340+/-138 and 15+/-4 microg/ml x min. The mean AUC peritoneal fluid/plasma ratio was 23.5+/-5.8. Patients who underwent extensive peritoneal resections exhibited a significantly (p = 0.037; Wilcoxon rank test) increased peak plasma concentration of MMC, a significantly (p = 0.029) increased AUC of plasma concentrations and a significantly (p = 0.034) decreased peritoneal fluid/plasma AUC ratio. Pharmacokinetic studies of early postoperative intraperitoneal 5-FU showed no significant difference in plasma AUC, perfusate AUC and AUC ratio between patients who received and those who did not receive heated intraoperative intraperitoneal MMC. CONCLUSIONS: Heated intraoperative intraperitoneal chemotherapy achieves high peritoneal concentrations of MMC with limited systemic absorption. Systemic drug absorption during heated intraoperative intraperitoneal chemotherapy is increased when extensive peritoneal resections are performed, but such slight increases are unlikely to change the risk of systemic drug toxicities. Heated intraoperative intraperitoneal chemotherapy does not alter the pharmacokinetics of early postoperative intraperitoneal 5-FU.
Antibiotics, Antineoplastic↗