Caffeine ingestion and fluid balance: a review

BACKGROUND

Caffeine and related methylxanthine compounds are recognized as having a diuretic action, and consumers are often advised to avoid beverages containing these compounds in situations where fluid balance may be compromised. The aim of this review is to evaluate the available literature concerning the effect of caffeine ingestion on fluid balance and to formulate targeted and evidence-based advice on caffeinated beverages in the context of optimum hydration.

METHOD

A literature search was performed using the Medline database of articles published in the medical and scientific literature for the period of January 1966-March 2002. Subject headings and key words used in this search were: tea, coffee, caffeine, diuresis, fluid balance and water-electrolyte balance. A secondary search was performed using the bibliographies of publications identified in the initial search.

RESULTS

The available literature suggests that acute ingestion of caffeine in large doses (at least 250-300 mg, equivalent to the amount found in 2-3 cups of coffee or 5-8 cups of tea) results in a short-term stimulation of urine output in individuals who have been deprived of caffeine for a period of days or weeks. A profound tolerance to the diuretic and other effects of caffeine develops, however, and the actions are much diminished in individuals who regularly consume tea or coffee. Doses of caffeine equivalent to the amount normally found in standard servings of tea, coffee and carbonated soft drinks appear to have no diuretic action.

CONCLUSION

The most ecologically valid of the published studies offers no support for the suggestion that consumption of caffeine-containing beverages as part of a normal lifestyle leads to fluid loss in excess of the volume ingested or is associated with poor hydration status. Therefore, there would appear to be no clear basis for refraining from caffeine containing drinks in situations where fluid balance might be compromised.

Antiarrhythmic efficacy of amiodarone in recurrent ventricular tachycardia evaluated by multiple electrophysiological and ambulatory ECG recordings

Thirty-three patients with recurrent drug-refractory ventricular tachycardia were treated with oral amiodarone during an average period of 6.1 months. In-hospital monitoring for two weeks or more, electrophysiological tests and ambulatory ECG were used to evaluate the results. Twenty patients are still using the drug with complete control of the arrhythmia. Eleven have failed the drug, ten due to recurrence of documented ventricular tachycardia. Only three patients failed after the first month of therapy. Two patients died, one suddenly. The drug was discontinued in a further two patients due to side-effects. Other side-effects were tolerable or manageable by dose adjustments alone. Five patients showed evidence of inadequate arrhythmia control between days 15 and 32 of therapy but subsequently responded to the drug for 4-9 months, giving further support to the concept that in some patients at least 30 days of therapy is necessary for the full effect of the drug to appear. In 16 of the 20 patients tested by arrhythmia induction study while on the drug, ventricular tachycardia could still be induced. Seven (44%) of these eventually failed the drug. Arrhythmia recurred in one of those four in whom tachycardia could not be induced. Amiodarone is a valuable drug in the management of recurrent ventricular tachycardia, refractory to other antiarrhythmic drugs.

157 VIRAL RISK ASSESSMENT OF BOVINE OOCYTES HARVESTED FROM ABATTOIR ORIGIN

Bovine oocytes derived from abattoir origin are mainly used for artificial reproductive techniques in both agricultural and biomedical applications. Regulatory agencies have expressed concern for potential transmission of adventitious viruses by sourcing bovine oocytes from abattoir origin. To evaluate this concern, a viral risk assessment was conducted on batch samples collected from follicular fluid, cumulus cells, oocytes, and Day 8 embryos. These batch samples were collected from ovaries on seven randomly selected days in a 2-week period and they were frozen and stored at –80°C until tested. All samples were tested by 9 Code of Federal Regulations (9CFR) part 113.53c (animal viral testing) at a GLP compliant laboratory (American BioResearch Laboratories, Sevier, TN, USA). The 9CFR viral testing includes bovine viral diarrhea virus (BVDV), bovine parvovirus, bovine adenovirus type 3 and 5, bovine rabies virus, bovine bluetongue virus, bovine respiratory syncytial virus, bovine reovirus, viral cytopathic effect, and hemadsorption on permissive cell cultures. Batch samples were also tested for BVDV and bovine leukemia virus (BLV) by polymerase chain reaction (PCR) and follicular fluids for BVDV antibody neutralization activity at an accredited diagnostic laboratory (Animal Disease Research and Diagnostic Laboratory, SDSU, Brookings, SD, USA). The 9CFR viral testing results on all the batch samples were negative. The BVDV PCR test had a low positive (37.89 cycles) with one follicular fluid batch sample (1/7) and a low positive (37.9 cycles) on all cleaved embryos (7/7). However, BVDV virus isolation was negative for both batch samples by 9CFR testing. The BLV PCR had a positive follicular batch sample (1/7), with all other samples testing being negative. BVD serum neutralization antibody assay demonstrated that all follicular fluid had significant titers of 1:128–1:1024. Although some of the viral particles may have been detected in follicular fluid and cleaved embryos by PCR, none of the batch samples collected were positive for viral growth in this study. The BVDV PCR indicated low levels of BVDV RNA. It is speculated that the positive BVDV PCR results on cleaved embryos could possibly be attributed to the use of irradiated fetal calf serum (contaminated BVDV virus) used in culture media. Follicular fluids also have high titers to BVDV which may have neutralized the virus. These results indicate that virus-free bovine oocytes can be derived from the abattoir. Thus, with appropriately applied quality assurance testing, abattoir-origin oocytes might be used effectively in agricultural and biomedical applications. Table 1. Summary of test results on batch samples from abattoir-derived oocytes

Ganciclovir Population Pharmacokinetics in Neonates Following Intravenous Administration of Ganciclovir and Oral Administration of a Liquid Valganciclovir Formulation

Cytomegalovirus (CMV) is the most common viral congenital infection, producing both sensorineural hearing loss and mental retardation. Our objective was to assess the population pharmacokinetics of a research-grade oral valganciclovir solution in neonates with symptomatic congenital CMV disease. Twenty-four neonates received 6 weeks of antiviral therapy. Ganciclovir and valganciclovir were measured by liquid chromatography/tandem mass spectroscopy. NONMEM version VI beta was used for population analyses. All profiles were consistent with a one-compartment model. Postnatal age, body surface area, and gender did not improve the model fit after body weight was taken into account. The typical value of clearance (l/h), distribution volume (l), and bioavailability of ganciclovir were 0.146 x body weight (WT)(1.68), 1.15 x WT, and 53.6%, respectively. Although these results cannot be extrapolated to extemporaneously compounded valganciclovir preparations, they provide the foundation on which a commercial-grade valganciclovir oral solution may be a viable option for administration to neonates.

Genotyping of Mycobacterium bovis isolates from badgers in four areas of the Republic of Ireland by restriction fragment length polymorphism analysis

An analysis of the molecular epidemiology of Mycobacterium bovis in badgers was made in four selected areas of the Republic of Ireland in which an intensive badger removal programme was being carried out over a period of five years. Tissue samples from 2310 badgers were cultured. Restriction fragment length polymorphism (RFLP) analysis with IS6110, polymorphic GC-rich sequence (PGRS) and direct repeat sequence (DR) probes was applied to the isolates from 398 badgers, and 52 different rflp types were identified. Most of the isolates belonged to seven predominant types, and the other 45 types were represented by few isolates. An analysis suggests that some of these 45 types may have been introduced by the inward migration of badgers and others may have been the result of genetic changes to one of the prevalent types. The badgers were divided into groups on the basis of the sett at which they were captured, and RFLP typing was applied to isolates from two or more badgers from 85 groups. Multiple RFLP types were identified among isolates from 50 of these groups, suggesting that badgers probably moved frequently between group territories.

Selamectin is a potent substrate and inhibitor of human and canine P-glycoprotein

The transport of the antiparasitic agents, ivermectin, selamectin and moxidectin was studied in human intestinal epithelial cell monolayers (Caco-2) and canine peripheral blood lymphocytes (PBL). Both models expressed the mdr1-coded 170 kDa ATP-binding cassette (ABC) transporter P-glycoprotein (P-gp). Fluxes of the P-gp substrate rhodamine-123 (Rh-123) across Caco-2 monolayers showed that ivermectin and selamectin acted as potent P-gp inhibitors with IC50 values of 0.1 microm. In contrast, moxidectin was a weaker P-gp inhibitor with an IC50 of 10 microm. The transport of radiolabelled ivermectin, selamectin and moxidectin through Caco-2 monolayers showed that ivermectin, selamectin and moxidectin were P-gp substrates with secretory/absorptive ratios of 7.5, 4.7 and 2.6 respectively. Secretory transport of [3H]-ivermectin and [3H]-selamectin was blocked by the P-gp inhibitor, verapamil. Ivermectin and selamectin inhibited the efflux of Rh-123 from PBL and the concentration of inhibition was similar to that of verapamil. In contrast, moxidectin did not have a significant effect on Rh-123 efflux from PBL. The data suggest that ivermectin and selamectin are potent P-gp substrates, while moxidectin is a weak one.

Comparison of end-tidal and transcutaneous measures of carbon dioxide during general anaesthesia in severely obese adults

BACKGROUND

Patients with severe obesity (body mass index (BMI) greater than 35 kg x m(-2)) present difficulties for end-tidal carbon dioxide (FE'(CO(2))) monitoring. Previous studies suggest that transcutaneous (TC) carbon dioxide measurements could be valuable, so we compared FE' and TC measures with Pa(CO(2)) in severely obese patients during anaesthesia.

METHODS

We studied patients with severe obesity (BMI >or=40 kg x m(-2)) undergoing gastric bypass surgery. Carbon dioxide was measured with both FE' and TC devices. The difference between each measure (FE'(CO(2)) and TC-CO(2)) and the Pa(CO(2)) was averaged for each patient to provide one value, and data compared with a non-paired, two-way t-test, Fisher's exact test.

RESULTS

We studied 30 adults (aged 18-54 yr, mean 41, SD 8.0 yr; weight: 115-267 kg, mean 162, SD 35 kg). The absolute difference between the TC-CO(2) and Pa(CO(2)) was 0.2 (0.2) (mean, SD) kPa while the absolute difference between the FE'(CO(2)) and Pa(CO(2)) was 0.7 (0.4) kPa (P<0.0001). The bias and precision were +0.1 (0.3) kPa for TC vs arterial carbon dioxide and -0.7 (0.4) kPa for FE' vs arterial carbon dioxide.

CONCLUSIONS

Transcutaneous carbon dioxide monitoring provides a better estimate of Pa(CO(2)) than FE'(CO(2)) in patients with severe obesity.

A modern day holy anorexia? Religious language in advertising and anorexia nervosa in the West

OBJECTIVE

In this review we comment on the media, in particular advertisements and the internet, using religious and moralistic motifs in connection with eating and their possible role in promoting modern-day 'nutritional' consumerism and fundamentalism (diet, discipline and discipleship).

METHOD

We have reviewed historically the concept of holy anorexia and have analyzed the pictorial and language content of some representative advertisements.

RESULTS

Words used include 'temptation', 'decadent', 'heaven' and 'purity' and suggest a connection with eating and moral values. They also imply eating as either heaven or sin, to be yielded to in both circumstances.

CONCLUSIONS

Such messages identifying eating with guilt or reward could precipitate 'atypical' eating disorders in vulnerable subjects, invoking the historical associations with extreme religiosity and anorexia. It is not clear how these 'fundamentalist' trends developed but health educators should be aware of them in dealing with at-risk subjects for eating disorders.

The effects of a home exercise program on pain and perceived dysfunction in a woman with TMD: a case study

There are few reports analyzing the effects of exercise on patients with temporomandibular disorders. This paper presents a case study examining whether there were additional benefits from performing neuromuscular control home exercises (NMCHE) in a patient with temporomandibular disorder who was already receiving conventional treatment. A woman, 41 years of age, completed a health status questionnaire called the TMJ Scale prior to being accepted. She completed additional TMJ Scales after receiving conventional treatment and again after conventional treatment was combined with neuromuscular control home exercises. Based on the TMJ Scale's best subscore indicator of the presence or absence of a temporomandibular disorder, the patient did not derive benefit from conventional treatment without exercise. However, she received a large benefit from the addition of NMCHE. It was concluded that exercises for patients with temporomandibular disorders may be beneficial to those who do not improve with conventional treatment alone.

The biology of signal transduction inhibition: basic science to novel therapies

Developing drugs to specifically inhibit oncogenes has been a major goal of cancer research for many years. Identifying the appropriate intracellular targets and understanding the signal transduction pathways in which these molecules participate are critical to this process. A large number of the activated oncogenes implicated in the pathogenesis and progression of malignancy are tyrosine kinases. Bcr-Abl, the causative molecular abnormality in chronic myeloid leukemia (CML), is a prototypic oncogenic kinase and an attractive drug target. The tyrosine kinase inhibitor imatinib mesylate (formerly STI571, [Gleevec]; Novartis Pharmaceuticals Corp, East Hanover, NJ) was recently approved for the treatment of CML and provides proof of principle for the strategy of targeted signal transduction inhibition. This drug is effective in the chronic phase of CML, a single gene disorder driven by Bcr-Abl, and in the advanced phases of CML, showing that inhibition of a single oncogene in a multigene disorder also may be of benefit. The success of imatinib mesylate in CML led rapidly to clinical trials in other cancers associated with activation of two other tyrosine kinases known to be sensitive to imatinib mesylate, c-Kit and the platelet-derived growth factor receptor. Gastrointestinal stromal tumors, which have activating mutations in c-Kit, are now also being found to respond to kinase inhibition with the drug. The general approach of specifically targeting activated kinases with small-molecule drugs is likely to be effective in other tumors in the future.

Normal flow (TIMI-3) before mechanical reperfusion therapy is an independent determinant of survival in acute myocardial infarction: analysis from the primary angioplasty in myocardial infarction trials

BACKGROUND

Whereas survival after lytic therapy for myocardial infarction is strongly dependent on early administration, it is unknown whether the otherwise excellent outcomes in patients undergoing primary PTCA for acute myocardial infarction, in whom TIMI-3 flow rates of >90% may be achieved, can be further improved by early reperfusion.

METHODS AND RESULTS

Among 2507 patients enrolled in 4 PAMI trials undergoing primary PTCA, spontaneous reperfusion (TIMI-3 flow) was present in 16% at initial angiography. Compared with patients without TIMI-3 flow, those with TIMI-3 flow before PTCA had greater left ventricular ejection fraction (57+/-10% versus 53+/-11%, P=0.003) and were less likely to present in heart failure (7.0% versus 11.6%, P=0.009). Patients with initial TIMI-3 flow had significantly lower in-hospital rates of mortality, new-onset heart failure, and hypotension and had a shorter hospital stay. Cumulative 6-month mortality was 0.5% in patients with initial TIMI-3 flow, 2.8% with TIMI-2 flow, and 4.4% with initial TIMI-0/1 flow (P=0.009). By multivariate analysis, TIMI-3 flow before PTCA was an independent determinant of survival (odds ratio 2.1, P=0.04), even when corrected for by postprocedural TIMI-3 flow.

CONCLUSIONS

Patients undergoing primary PTCA in whom TIMI-3 flow is present before angioplasty present with greater clinical and angiographic evidence of myocardial salvage, are less likely to develop complications related to left ventricular failure, and have improved early and late survival. These data warrant prospective randomized trials of pharmacological strategies to promote early reperfusion before definitive mechanical intervention in acute myocardial infarction.

Effect of soft lumbar support belt on abdominal oblique muscle activity in nonimpaired adults during squat lifting

STUDY DESIGN

A counterbalanced repeated measures design.

OBJECTIVE

To determine the effect of a soft lumbar support on abdominal oblique muscle electromyography (EMG) during lifting.

BACKGROUND

Use of a soft lumbar back support is a common preventive measure to reduce the incidence of back injuries. Because the abdominal oblique muscles stabilize the spine during lifting, wearing this support may alter the activity level of these muscles.

METHODS AND MEASURES

Twenty nonimpaired subjects (14 women and 6 men, mean age 28.9 +/- 8.1 years) were tested using surface electrodes to record the EMG of the right abdominal oblique muscles during lifting with and without the support.

RESULTS

A paired t test revealed a significant decrease in activity of the abdominal oblique muscles during lifting with the support (29.7 +/- 3.13 mV) compared to without it (33.3 +/- 3.05 mV). Of the 20 subjects, the 14 women showed decreased EMG amplitude during the lift with the lumbar support compared to without the support, while 5 of the men showed increased EMG amplitude with the support and 1 man showed no change.

CONCLUSION

This finding suggests that the soft lumbar support may play some role in the stabilization of the lumbar region during lifting.