Is the IV obstructed or infiltrated? A simple clinical test

Objective. The objective of our study was to determine if clinical observation of pressure-flow relationships (PFR) can differentiate between partial external obstruction (obstruction) and infiltration as a cause of poor performance of gravity-fed infusions.Methods. A total of 24 patients with functional intravenous cannulae in situ had obstruction simulated by the application of a tourniquet proximal to the cannula. The change in flow (F) for a discrete change in pressure (P) was determined in each case by counting drop rates at two different elevations of the fluid reservoir level, 10 cm apart. The same process was repeated in 15 patients in whom the cannula was in an extra vascular location (infiltration). Three sizes of cannula—16-gauge, 18-gauge, and 20-gauge—were examined, with equal distribution of sizes in each group. The effect on flow rates of inflating a blood pressure (BP) cuff proximally on the cannulated limb was assessed. The ratio P/F is the total resistance of the infusion system, and by subtracting known values for resistance of infusion tubing and cannula, the venous or tissue resistance was calculated.Results. There was a statistically significant difference between the change in flow for obstructed compared with infiltrated cannulae for the same change in pressure for each cannula size. The mean venous resistance was 23 mm Hg/L/hr, while that of tissue was 280 mm Hg/L/hr, with no overlap between groups. There was no effect on flow rate with blood pressure cuff inflation in the infiltrated group whereas flow progressively fell in the obstructed group.Conclusions. Clinical observation of PFRs in poorly functioning gravity-fed IV infusions can assist in detecting infiltration as a cause. Inflation of a blood pressure cuff will further impair flow where the cannula is intravascular, but will have no effect in an extravascular location.     

A comparison of augmenting central serotonin and noradrenaline function in healthy subjects: implications for studies on the neurochemistry of anxiety

Biochemical and psychophysiological effects of augmenting serotonergic and noradrenergic function were compared in 12 normal volunteers. Fluvoxamine (100 mg), a serotonin (5-HT) re-uptake inhibitor, maprotiline (75 mg), a noradrenaline re-uptake inhibitor, and placebo were given for 7 days each to each subject. Subjects were tested pre-drug on days 1, 4 and 8 of each treatment. Catecholamines in 24 h urine, 'platelet-rich' plasma 5-HT and hormones, EEG, auditory evoked response, skin conductance, and bodily and psychological responses were monitored. Augmentation of central 5-HT by fluvoxamine was demonstrated by the decrease of 5-HT plasma levels. Fluvoxamine also reduced urinary dopamine, indicating a decrease in dopamine metabolism in response to augmentation of 5-HT function. Decrease in pulse rate, loss of appetite and a mild arousing effect were also detected with administration of fluvoxamine. Thus, further investigations on the neuro chemistry of anxiety disorders should include the study of mechanisms of interaction of neurotransmitters.     

Mistreatment due to weight: prevalence and sources of perceived mistreatment in women and men

OBJECTIVE: Previous research has documented prejudicial attitudes and discrimination against overweight people. Yet the extent to which overweight people themselves perceive that they have been mistreated because of their weight has not been carefully studied. The purpose of this study was to examine the prevalence of perceived mistreatment due to weight and sources of perceived mistreatment. METHODS AND PROCEDURES: A non-clinical sample of healthy adults (187 men and 800 women) enrolled in a weight gain prevention program comprised the study population. A self-administered questionnaire was used to measure perceived mistreatment due to weight. RESULTS: Overall, 22% of women and 17% of men reported weight-related mistreatment. The most commonly reported sources of mistreatment among women were strangers (12.5%) and a spouse or loved one (11.9%). Men were most likely to report mistreatment by a spouse or loved one (10.2%) and friends (7.5%). Somewhat surprisingly, sex differences in perceived weight-related mistreatment were significant only for stranger as the source. Perceived weight-related mistreatment was positively associated with body mass index (BMI) (r = 0.39, p<0.0001). Reported mistreatment was nearly ten times as pervalent among individuals in the highest quartile of the BMI distribution (42.5%) than among those in the lowest BMI quartile (5.7%), but was significantly greater than zero in all but the very lean. DISCUSSION: Perceived mistreatment due to weight is a common experience and is not restricted to the morbidly obese. Results are discussed in light of the sociocultural value for thinness.     

New PBPK model applied to old occupational exposure to benzene

An intensive program of benzene monitoring using new techniques was undertaken in Western Europe in the late 1960s and early 1970s. Significant exposure was found in the transport of benzene and gasoline, particularly during the loading of barges, and during the loading and operation of sea-going vessels. The ceiling threshold limit value of 25 ppm recommended at that time generated problems in assessing exposure, so alternative criteria were proposed. During that period some shore-based exposures were reported, and their significance was discussed in several articles. The information gained at that time is reexamined by physiologically based pharmacokinetic (PBPK) modeling and is used to help validate an improved PBPK model, which is described and tested on results from experimental exposure in a companion article. The old field data, comprising five specific studies, confirm the relevance of modeling to assessment of occupational exposure, and demonstrate its value for interpretation of field data, which is seldom as complete, systematic, or accurate as that obtained in experimental work. The model suggests that metabolism of benzene in humans may not be restricted to the liver. Sites and processes of metabolism merit further investigation.     

Plasma tryptophan and trait aggression.

Many studies have reported correlations between measures of aggression and indices of serotonergic function, but most have studied patient or offender populations and relatively few have investigated plasma concentrations of the serotonin precursor tryptophan. This study investigates the relationship between plasma concentrations of tryptophan and trait hostility, depression and anxiety in male healthy volunteers. Sixty-seven healthy male volunteers gave blood samples and completed trait questionnaires. Plasma tryptophan was positively correlated with the Buss-Durkee Hostility Inventory Total score and Motor Aggression subscale, but not with the Attitudinal Hostility subscale or with trait anxiety or depression. In conclusion, there is evidence for an association between high concentrations of plasma tryptophan and aggressive behaviour in men, presumably mediated by some aspect of central serotonergic function, which seems unlikely to be explained by high trait anxiety or depression.     

Characteristics of the vibratory reflex in humans with reduced suprasegmental influence due to spinal cord injury

The tonic stretch reflex elicited by vibration of a muscle or tendon provides a means of studying segmental reflex activity in humans with impaired volitional motor activity due to spinal cord injury (SCI). Vibration applied to the achilles or patellar tendon in a group of 51 SCI subjects elicited motor unit activity different from that found in 12 healthy subjects. Four distinct features of motor unit responses to vibration of a single tendon (achilles or patellar) could be seen in the SCI subjects: (i) a rapid onset, tonic response, frequently beginning with a single burst analogous to a tendon jerk, in 72% of vibrated sites; (ii) repetitive, phasic bursts of activity or vibratory-induced clonus in 23% of the tonic responses; (iii) spread of activity to muscles distant from the vibration in 44% of the tonic responses; and vibratory-induced withdrawal reflexes (VWR) which occurred after vibration of 37% of the sites. Overall, 81% of stimulated sites responded to vibration in SCI subjects. In contrast, only 54% of vibrated sites responded in control subjects, always with a gradual onset tonic response, never accompanied by a VWR. The VWR in SCI subjects was typically of much larger amplitude than the tonic responses and involved a mean of 5 muscles (41% bilaterally). Features of these responses provide an insight into underlying neurocontrol mechanisms which may provide guidance in the selection of appropriate intervention or management strategies.     

Molteno implants in children

We report our experience with Molteno implants in 27 eyes of 20 children with glaucoma. Associated ocular findings included Sturge Weber syndrome (one patient), aniridia and retinoschisis (one patient), aphakia (seven patients, eight eyes), rubella syndrome (two patients), Peters anomaly (one patient), and Treacher Collins syndrome (one patient). Fifteen eyes received a single-plate implant, and 12 eyes received a double-plate implant in two stages. The patients' ages ranged from 2 months to 13 years (mean 47 +/- 55 months). The average number of previous glaucoma procedures was four per eye (range two to 10). The follow-up period ranged from 6 to 36 months (mean 20 +/- 9 months). The mean intraocular pressure before surgery was 34 +/- 4 mm Hg. The mean postoperative intraocular pressure was 19 +/- 11 mm Hg at 1 month and 19 +/- 6 mm Hg at 1 year (p < 0.001 at both times). After surgery nine eyes (33.3%) required no medication for control of intraocular pressure. Additional surgery was required in 12 eyes (44.4%). We believe the Molteno implant is a useful approach for children with glaucoma who fail to respond to standard medical and surgical treatments.     

The bioactivation of 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954)--I. Purification and properties of a nitroreductase enzyme from Escherichia coli--a potential enzyme for antibody-directed enzyme prodrug therapy (ADEPT).

A nitroreductase enzyme has been isolated from Escherichia coli B. This enzyme is an FMN-containing flavoprotein with a molecular mass of 24 kDa and requires either NADH or NADPH as a cofactor. Partial protein sequence analysis showed extensive homology with the "classical nitroreductase" of Salmonella typhimurium and a nitroreductase induced in Enterobacter cloacae. In common with the Salmonella enzyme, the E. coli B enzyme is capable of reducing nitrofurazone. The E. coli nitroreductase is also capable of reducing the anti-tumour agent CB1954 [5-(aziridin-1-yl)-2,4-dinitrobenzamide], a property shared with the mammalian enzyme DT diaphorase [NAD(P)H dehydrogenase (quinone)] as isolated from Walker cells. The reduction of CB1954 by the E. coli enzyme results in the generation of cytotoxic species. Both enzymes also share the properties of being able to reduce quinones and are both inhibited by dicoumarol. The nitroreductase is a more active enzyme against CB1954 (kcat = 360 min-1) than Walker DT diaphorase (kcat = 4 min-1) and also has a lower Km for NADH (6 vs 75 microM).     

Quality assurance in biomedical or clinical engineering

Biomedical department directors must begin serious consideration of quality assurance (QA) implementation if they are to satisfy JCAHO directives. This consideration need not be approached with fear or anxiety. The purpose of this paper is to focus attention on the need and purpose of quality assurance in the biomedical or clinical engineering discipline while demonstrating the ease with which QA may be integrated into an existing biomedical environment. Because every biomedical program is unique, the approach described here can serve as a basic guide for tailoring essential components into a working quality assurance system.