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Biomedical subjects

J R Colvin

Publications and source records attributed to J R Colvin.

At least 19 recordsLinked to original sources
PubMed1995

Shaping attitudes to postoperative pain relief: the role of the acute pain team.

Postoperative pain relief is often inadequate. Ignorance and misconceptions about opioids by ward staff contribute to this poor management. The introduction of acute pain teams has done much to improve pain relief for patients. It may also have contributed to changes in attitudes and knowledge of medical and nursing staff. We questioned 48 doctors and nurses on their knowledge and beliefs about postoperative pain relief. Staff members were questioned on two units, one with access to an acute pain team and one without. Over half those on the unit using traditional postoperative care thought patients did not receive adequate pain relief (58%). In comparison, only one respondent from the unit with the pain team thought this was the case (P < 0.001). More staff members that had experience of patient-controlled analgesia (PCA) were optimistic about its benefits than those in the unit with no experience; they were also less concerned about possible side effects. Only one respondent on the unit using PCA thought it carried a risk of drug dependence, compared to over half (55%) of those on the unit with no experience in this technique (P < 0.001). Over two-thirds of staff familiar with PCA thought nursing workload had decreased. Acute pain teams have an important role in educating ward staff. The impact of establishing such teams on staff knowledge and attitudes needs further study to ensure that they can carry out this role most effectively.

Attitude of Health Personnel↗
PubMed1993

The administration of supplementary oxygen to prevent hypoxia during upper alimentary endoscopy.

A prospective, randomized, controlled trial was conducted in 200 consecutive patients undergoing endoscopy of the upper alimentary tract. One hundred patients received supplementary oxygen at 4 liters/minute through nasal cannulae, while 100 patients received no additional oxygen. Within each of these two groups, 50 patients were sedated with midazolam and 50 patients with diazepam suspension ("Diazemuls"). The patients' weights were recorded and correlated with their height to assess whether they were over or under their ideal weight. Oxygen saturation was recorded at baseline and throughout the endoscopic procedure. The principal finding of this study was that hypoxia (oxygen saturation less than 93%) was prevented in all cases by the administration of 4 liters/minute of oxygen, whereas 48 of the 100 patients who did not receive oxygen exhibited falls in oxygen saturation to less than 93% (p < 0.0001). Those with the highest risk were the obese patients (p < 0.01). There was no significant difference between the two sedative drug groups in either frequency or severity of associated hypoxia (p = 0.77, patients not given oxygen; p = 0.31, patients receiving oxygen). The cost of administering oxygen during upper gastrointestinal endoscopy would be an average of 95 pence ($1.60) per patient. In conclusion, the administration of oxygen during endoscopy is a worthwhile prophylactic measure to prevent hypoxia and its potential adverse effects.

Costs and Cost Analysis↗
PubMed1993

Closed loop control of arterial hypertension following intracranial surgery using sodium nitroprusside. A comparison of intra-operative halothane or isoflurane.

Forty patients were chosen at random to receive halothane or isoflurane anaesthesia during craniotomy and a comparison of the postoperative hypertensive response was made using a microcomputer-based closed-loop arterial pressure control system with sodium nitroprusside to control and assess arterial pressure during the first 6 postoperative hours. A desired target systolic pressure was chosen for each patient and the frequency of hypertension, sodium nitroprusside requirements and quality of arterial pressure control were compared between the two groups. Thirty-five patients required sodium nitroprusside. The halothane group required a median dose of 15.2 mg (range 0-72) compared to 3.4 mg (range 0-87) in the isoflurane group. This difference is not statistically significant. Quality of arterial pressure control was satisfactory in both groups. In conclusion, arterial hypertension occurs frequently following intracranial surgery and is uninfluenced by the choice of halothane or isoflurane intra-operatively. This closed-loop arterial pressure control system functioned safely and effectively in this context.

Adolescent↗
PubMed1993

Sedation with propofol during surgery under local blockade. Assessment of a target-controlled infusion system.

The ability of a target-controlled propofol infusion system to provide sedation for 40 patients undergoing surgery under regional blockade was assessed. Eighty-eight per cent of the total infusion time was at the desired sedation level with little oversedation. This was achieved with a median blood propofol concentration of 0.93 micrograms.ml-1. The pharmacokinetic algorithm performed as well when used for sedation as for total intravenous anaesthesia. The predicted and measured blood propofol concentrations showed a bias of -12% and a precision of 34%.

Adolescent↗
PubMed1992

Evaluation of closed loop control of arterial pressure during hypotensive anaesthesia for local resection of intraocular melanoma.

We have studied 20 patients undergoing local resection of intraocular melanoma during hypotensive anaesthesia, allocated randomly to receive either manual control by an experienced anaesthetist or closed-loop computer control of an infusion of a 5:1 mixture of trimetaphan camsylate (TMP) and sodium nitroprusside (SNP). There were no significant differences in the smallest systolic and diastolic arterial pressures obtained, heart rate or infusion requirements between the two groups, but the duration of both the infusion and the operation were significantly longer in the computer-controlled group (P < 0.05). The quality of control of arterial pressure was assessed by the percentage of time spent at pressures greater and less than the prescribed target values, and was satisfactory in both groups during the critical period of profound hypotension. We conclude that the computer-controlled infusion performed satisfactorily during profound hypotension compared with an experienced anaesthetist.

Adult↗
PubMed1989

Development and evaluation of a dual-pump microcomputer-based closed-loop arterial pressure control system.

Hypertension after cardiac surgery is common and is associated with increased morbidity. It is usually managed by the infusion of short acting vasodilators. The use of a closed-loop computer system to control the infusion of a vasodilator has been shown to compare favourably with manual control. We have developed a closed-loop system for the ATARI 1040ST microcomputer to control arterial pressure by the simultaneous infusion of two vasodilators. The control program is based on a proportional-integral-derivative algorithm which has been adapted to allow control of two IMED 929 infusion pumps from one RS-232 port. All communication between the user and computer is carried out with a 'mouse', thus increasing acceptability of the system to ward staff. Cardiovascular data are collected on-line from the patient monitor via a custom-built analogue to digital convertor. This system was used to study glyceryl trinitrate and sodium nitroprusside in 24 patients requiring vasodilators after cardiopulmonary bypass. The study showed that in 14 of the patients hypertension was controlled by GTN alone and 10 required supplementary SNP. We have demonstrated that this dual-pump automatic arterial pressure control system is a satisfactory and safe method of administering two vasodilators simultaneously. It is suitable for both routine clinical and research uses.

Blood Pressure↗
PubMed1989

Microcomputer-controlled administration of vasodilators following cardiac surgery: technical considerations.

Hypertension in the early postoperative period after cardiopulmonary bypass is associated with increased morbidity, and is commonly managed by the infusion of short-acting vasodilators. Automatic arterial blood pressure control by closed-loop infusion has been shown to be superior to manual control in several studies. The investigators have developed a closed-loop arterial pressure control system based on the Atari 1040ST microcomputer (Atari, Sunnyvale, CA). The program uses a proportional-integral-derivative control algorithm, developed from that described by Sheppard and his colleagues. The arterial waveform is sampled digitally, and the waveform analysis routine incorporates several artifact detection and rejection functions. Additional safety features are provided in the computer-infusion pump subroutine, which cause alarms to be activated if computer-pump communication fails to occur within a specified time period. A novel feature of this system is the clinical staff's use of a "mouse" to enter data and control the program, which makes keyboard skills unnecessary. This system is in routine service in the cardiac intensive care unit (CICU), both for direct clinical use and for research into various aspects of arterial pressure control, and has proved to be acceptable to the clinical staff.

Algorithms↗
PubMed1989

Effect of ketanserin on sodium nitroprusside requirements, arterial pressure control and heart rate following coronary artery bypass surgery.

In a double-blind, placebo controlled study ketanserin, a serotonin S2 antagonist, was administered to hypertensive patients who had undergone coronary artery bypass surgery. Patients were allocated randomly to receive placebo or ketanserin at an infusion rate of 0.05, 1 or 2 mg kg-1 h-1. Sodium nitroprusside was used as escape medication. Ketanserin reduced the nitroprusside requirements and improved the quality of arterial pressure control in all groups, and this was significant in the low- and high-dose groups. There was a significant decrease in heart rate in the low- and high-dose groups compared with placebo, and no effect in patients who received the medium dose of ketanserin. Ketanserin may be a useful treatment for hypertension following coronary artery surgery as it reduced arterial pressure without reflex tachycardia.

Adult↗
PubMed1989

Automatic control of arterial pressure after cardiac surgery. Evaluation of a microcomputer-based control system using glyceryl trinitrate and sodium nitroprusside.

Arterial hypertension after cardiac surgery is common and is associated with increased morbidity. Glyceryl trinitrate may be a more suitable agent for control of hypertension than sodium nitroprusside. We have developed a closed-loop system for the Atari 1040ST microcomputer to control arterial pressure by the simultaneous infusion of two vasodilators under computer control. Use of this system with glyceryl trinitrate and sodium nitroprusside in 24 patients who required vasodilators after cardiopulmonary bypass, revealed that hypertension was controlled by glyceryl trinitrate alone in 14 of the patients and 10 required supplementary sodium nitroprusside. The results suggest that glyceryl trinitrate is a suitable agent for control of hypertension after cardiac surgery in the majority of patients. They also show that a sizeable minority required additional sodium nitroprusside, and that an automated 'dual pump' system is a satisfactory method of administering two vasodilators in this way.

Cardiac Surgical Procedures↗
PubMed1982

Spontaneous protoplast formation in Methanobacterium bryantii.

Methanobacterium bryantii was found to undergo rapid lysis when grown in a prereduced chemically defined medium under H2-CO2 (4:1, vol/vol). The addition of 20 mM MgCl2 to the medium gave, rather than rapid lysis, a gradual formation of phase-dark spherical bodies which in thin section appeared as true protoplasts. In general, the protoplasts were stabilized by divalent but not monovalent cations and, unlike whole cells, were sensitive to lysis by Triton X-100. Electron microscopic examination revealed that protoplast formation was preceded by a general breakdown of the cell wall with an apparent squeezing out of the protoplast through the degraded wall. The growth of cells was greatly increased and not accompanied by detectable lysis in a medium modified by elevating the levels of nickel and ammonium.

Bacteriolysis↗
PubMed1979

The ultrastructure of the major species of an enriched methanogenic culture utilizing acetic acid.

The ultrastructure of the cells of the major component of an enriched culture of a presumed methanogen which utilized acetic acid was studied by transmission and scanning electron microscopy. The filaments were composed of Gram-positive, rod-shaped cells, 1--2 micrometer in length and about 0.5 micrometer in breadth, attached end to end. Septa between cells were complex, with a central, electron-dense sheet which had a spherical enlargement in the center separating the cell walls. The cells walls themselves were of variable thickness with a light, fluffy, thin portion on the outside and a denser, thicker portion within. They contain a series of rings stacked side by side which are composed of material that stains strongly and positively with phosphotungstate ion. The cytoplasmic membrane of these cells had an outer leaflet which stains more densely with uranium and lead ions than the inner leaflet. There were no recognizable organelles in the cytoplasm other than ribosomes. It is shown in these observations that the presumed methanogen may likely be a new species.

Acetates↗
PubMed1979

Additional properties of a soluble polymer of glucose from cultures of Acetobacter xylinum.

The results of differential, thermal analysis of a soluble, beta (1 leads to 2)-branched, beta (1 leads to 4)-D-glucan isolated from cultures of Acetobacter xylinum are consistent with previous conclusions about its structure. The O-acetyl content of the polymer is 8.3% which corresponds to a maximum substitution of one acetyl group per three glucose residues. Proton nuclear magnetic resonance spectra confirm that all the glycosidic bonds are beta linkages. Some preparations of the polymer are contaminated by another polymer containing mannose and rhamnose. No evidence was obtained to support a previous suggestion that the branched D-glucan is a precursor of bacterial cellulose and this suggestion is now withdrawn.

Glucans↗
PubMed1978

Morphology microstructure, and development of colonies of Acetobacter xylinum.

Development of the morphology and microstructure of colonies of Acetobacter xylinum growing on agar was studied by optical microscopy, and transmission and scanning electron microscopy. The mass of rapidly dividing cells surrounded by a sheath of cellulose microfibrils passes from a smooth spheroid to a flattened aggregate with a characteristic "pillowed" surface. This morphology is the result of a repeated extrusion of cells from the confirming sheath, followed by regeneration of a new portion of the sheath on the extrusion of cells from the confirming sheath, followed by regeneration of a new portion of the sheath on the extruded cell mass. Relations of this mechanism to others which produce similar shapes are indicated.

Agar↗
PubMed1977

The structure of cellulose-producing bacteria, Acetobacter xylinum and Acetobacter acetigenus.

The structure of the pellicles and cells of the cellulose-producing bacteria, Acetobacter xylinum and Acetobacter acetigenus, was studied by transmission electron microscopy of thin sections and freeze-etch replicas of glucose-stimulated cell suspensions, quiescent cell suspensions, and discrete pellicles. These bacteria have a relatively thin cell wall in section, with several irregular features superimposed on an otherwise simple, Gram-negative morphology. There are no flagella or pili. Unfixed, unextracted cells, viewed as whole mounts, show spherical or ellipsoidal bodies of undetermined composition which disappear after extraction with water or ethanol and propylene oxide. For both species, there are several kinds of cell surface irregularities, some of which are localized protrusions of the cell envelope. A variety of irregularities is seen frequently on cells in the first minutes of glucose incubation, on cells in a discrete pellicle, on quiescent cells, and on starved cells. Immediately after the addition of glucose to cellulose-free cells in suspension culture, fine fibrils appear on and (or) near the cell envelope. The fine fibrils are frequently as small as 3 nm in diameter in both freeze-etch and thin-section preparations and are frequently associated with freshly synthesized cellulose fibrils. Starved cells in suspensions free of (classical) microfibrils sometimes reveal stubs of an extracellular structure whose morphology resembles that of a nascent cellulose fibril.

Cell Membrane↗