A paradox of cerebral hyperperfusion in the face of cerebral hypotension: the effect of perfusion pressure on cerebral blood flow and metabolism during normothermic cardiopulmonary bypass

BACKGROUND

The purpose of this study was to determine the impact of perfusion pressure on cerebral blood flow (CBF) and metabolism during normothermic cardiopulmonary bypass (CPB) and after weaning.

MATERIALS AND METHODS

Two groups of mongrel dogs were studied (Group A, CPB perfusion at 50 mm Hg, n = 6; and Group B, CPB perfusion at 100 mm Hg, n = 6). All animals underwent 2 h of normothermic bypass at cardiac indexes >2.1 L/min/m2 and were weaned from pump, maintained at pressures >75 mm Hg, and followed for an additional 2 h.

RESULTS

In both groups CBF increased over 85% from baseline, in proportion to the hemodilution during the initiation of CPB. Intracranial pressure increased moderately in both groups during CPB, compromising CBF at 1 h in Group A, but not in Group B. The Group A cerebral metabolic rate for oxygen (CMRO2), however, remained unchanged as the percentage of oxygen extraction increased to compensate for the decreased CBF. During recovery, temperature, mean arterial pressure, and cerebral perfusion pressure were not significantly different between the two groups. However, the CBF, percentage of oxygen extracted, and CMRO2 were significantly lower in Group A.

CONCLUSIONS

Normothermic CPB initiated with a crystalloid prime and performed at the lower end of a 50-70 mm Hg perfusion window resulted in a highly significant increase in CBF in order to compensate for hemodilution, while at the same time reduced the perfusion pressure available to supply the increased CBF. Together, these two events create a hemodynamic paradox of hyperperfusion in the face of hypotension. The reduction in CMRO2 in Group A is yet to be explained but seems to remain coupled to CBF and could represent a previously undescribed protective mechanism of hibernating cerebral tissue, similar to the phenomena of ischemic preconditioning in the heart, where cerebral tissue is stimulated to lower metabolism in response to inadequate CBF.

Osteolysis versus osteomyelitis: a clinical case report

Differentiating osteolysis and osteomyelitis is a formidable challenge for even the most experienced clinician. Although the two may have a similar presentation, the treatment regimen, morbidity, and long term prognosis for the patient are vastly dissimilar. The diagnosis of osteomyelitis carries with it a need for immediate and decisive action that may include early aggressive amputation. Conversely, the diagnosis of osteolysis necessitates a patient, conservative approach so as not to "burn any bridges", and to allow time for the affected part to heal.

Variability in measurement of central retinal artery velocity using color Doppler imaging

The purpose of our study was to test the reproducibility of the central retinal artery velocity measurements as made by color Doppler imaging and pulsed Doppler spectral tracings and to define the optimal location for placement of the sample volume. We used the Siemens Quantum (Q 2000) with a 7.5 MHz linear array transducer to identify the central retinal artery and record its velocity. Eleven eyes from 11 normal subjects were evaluated for the peak systolic central retinal artery velocity in two positions, the first posteriorly in the optic nerve at an average of 3.56 mm from the surface of the optic disc and the second at an average of 1.76 mm from the surface of the optic disc. We then used a color-flow threshold to identify and record the point of maximal velocity. The range of systolic velocities in the 11 eyes was from 5.85 to 22.51 cm/sec. The peak systolic velocity posteriorly in the optic nerve averaged 8.16 cm/sec, whereas near the surface of the optic disc the velocity averaged 13.89 cm/sec (70.2% higher). Using the color flow threshold method, the maximal velocity was located at an average of 1.98 mm from the surface of the optic disc. Our data show that large differences exist in measured central retinal artery velocity that depend on the location of the measurement, and that color-flow thresholding is valuable in locating the optimal location for pulsed Doppler spectral recording.

Gas chromatographic determination of vapor-phase biomarkers formed from rats dosed with CCl4

Sprague-Dawley rats dosed with CCl4 (3 ml kg-1) were placed in a glass chamber through which air was passed continuously at a rate of 60 ml min-1. Volatile aldehydes and ketones in expired air from rats were derivatized to thiazolidines by passing the effluent gas stream through an aqueous cysteamine solution. The thiazolidine derivatives were then extracted and analyzed by gas chromatography with a nitrogen-phosphorus detector and gas chromatography/mass spectrometry. The compounds identified were formaldehyde, acetaldehyde, acetone and formyl chloride. There were no appreciable differences in levels of formaldehyde and acetaldehyde between CCl4-dosed rats and control rats, whereas the levels of acetone in CCl4-dosed rats showed an increase compared to those in control rats. Results suggest that acetone is the major volatile carbonyl compound produced following acute doses of CCl4. Results of thiobarbituric acid assay on the livers from a control rat and a CCl4-dosed rat did not show any appreciable differences.

Sesamoids and accessory bones of the foot

This contribution presents the major pathologic findings and causes of sesamoid disease. The reader will appreciate the thoroughness of this article.

Gas chromatographic analysis of reactive carbonyl compounds formed from lipids upon UV-irradiation

Peroxidation of lipids produces carbonyl compounds; some of these, e.g., malonaldehyde and 4-hydroxynonenal, are genotoxic because of their reactivity with biological nucleophiles. Analysis of the reactive carbonyl compounds is often difficult. The methylhydrazine method developed for malonaldehyde analysis was applied to simultaneously measure the products formed from linoleic acid, linolenic acid, arachidonic acid, and squalene upon ultraviolet-irradiation (UV-irradiation). The photoreaction products, saturated monocarbonyl, alpha,beta-unsaturated carbonyls, and beta-dicarbonyls, were derivatized with methylhydrazine to give hydrazones, pyrazolines, and pyrazoles, respectively. The derivatives were analyzed by gas chromatography and gas chromatography-mass spectrometry. Lipid peroxidation products identified included formaldehyde, acetaldehyde, acrolein, malonaldehyde, n-hexanal, and 4-hydroxy-2-nonenal. Malonaldehyde levels formed upon 4 hr of irradiation were 0.06 micrograms/mg from squalene, 2.4 micrograms/mg from linolenic acid, and 5.7 micrograms/mg from arachidonic acid. Significant levels of acrolein (2.5 micrograms/mg) and 4-hydroxy-2-nonenal (0.17 micrograms/mg) were also produced from arachidonic acid upon 4 hr irradiation.

Development and validation of new analytical method for acrolein in air

A new method was developed to determine vapor-phase acrolein in air samples. Air containing vapor-phase acrolein was purged into impingers filled with a dichloromethane solution of N-methylhydrazine. The resulting derivative, 1-methyl-2-pyrazoline, was analyzed by gas chromatography using a nitrogen-phosphorous detector (NPD). The detection limit was 8.9 pg 1-methyl-2-pyrazoline, equivalent to 5.9 pg acrolein. The recovery efficiencies of vapor-phase acrolein were 98.0 +/- 2.9% and 100.3 +/- 3.1% for 150 and 15 micrograms, respectively. This method was satisfactorily applied for determination of acrolein formed from various heated fats. The amounts of acrolein formed in a headspace were 109 micrograms/L from lard, 164 micrograms/L from corn oil, 5.1 micrograms/L from cotton seed oil, and 163 micrograms/L from sunflower oil.

Infection following caesarean section

In a prospective clinical study of post-operative infection in 124 patients undergoing Caesarean section, 39 (31.5%) patients developed a total of 45 infections. There was no significant difference in infection rates between elective and emergency procedures. Five patients (4%) developed endometritis, wound infection was found in 14 (11.3%) and 18 patients (14.5%) developed a post-operative urinary tract infection. Pre-operative C-reactive protein levels and intraoperative swabs of the uterine cavity were not helpful in the early detection of endometritis. The risk factors predisposing to post-caesarean infection were obesity and low socioeconomic status.

Production of malonaldehyde from squalene, a major skin surface lipid, during UV-irradiation

Malonaldehyde (MA), a product of lipid peroxidation, is known to have a number of toxicological effects. Among skin surface components, squalene has been suggested as a significant source of MA following UV exposure. Irradiation of squalene coated on the inside surface of glass tubes served as a simple model to examine skin surface photochemistry. Malonaldehyde produced during UV-irradiation was reacted with methyl hydrazine to form N-methylpyrazole, which was then measured by gas chromatographic analysis. Ultraviolet A-irradiation produced low levels of MA from squalene, with a maximum of 1.0 nmol MA/mumol squalene near 6 h. Malonaldehyde production varied with the energy of irradiation, with levels of 176 nmol/mg squalene and 9 nmol/mg squalene produced after 3 h of irradiation with UVB and UVA, respectively. The thiobarbituric acid (TBA) assay for lipid peroxidation showed large overestimations of MA levels under all irradiation conditions tested. The TBA assay predicted the highest levels of MA with UVC but we did not detect any MA with our assay.

Gas chromatographic determination of malonaldehyde formed by lipid peroxidation

Gas chromatographic (GC) methods for the determination of malonaldehyde (MA) all require formation of a stable derivative of MA since free MA is not suitable for direct GC analysis. Most reported GC methods give a total measure of free MA and its bound forms because their assay conditions are sufficient to hydrolyze or decompose bound MA during sample preparation. In this paper, GC methods that provide a measure of total MA (free plus bound) are reviewed. A recently developed capillary GC method that allows determination of free MA apart from other forms is also discussed. The method involves derivatization of MA to N-methylpyrazole under milder reaction conditions than with other GC methods. The method represents an advantage over existing techniques for free MA determination because capillary GC offers the highest efficiency of separation among chromatographic methods thus allowing a more specific and accurate measure of MA.

The OVEIA assay, a simultaneous measurement of oestrone and pregnanediol glucuronides, for studying the treatment of infertility patients

A new simple assay developed for establishing the limits of the fertile period was evaluated in infertility patients. This assay is a colorimetric method for measuring the oestrone glucuronide/pregnanediol glucuronide ratio. Steroid levels were assayed simultaneously and an index of their ratio was obtained in this dual analyte assay (DAA). Twenty subfertile women, receiving clomiphene citrate for ovulation induction, were monitored for the DAA index using early morning urine samples. Ten of these women were also monitored in a pretreatment cycle. A further 10 patients on an in-vitro fertilization (IVF) programme were assessed with the same assay. DAA ratios were found to correlated with follicular phase serum oestradiol levels. Peak DAA ratios dropped dramatically when significant rises in urinary luteinizing hormone concentrations occurred prior to ovulation. An association between high DAA ratios and adequate luteal phase activity was also established. In addition, the total volume of the three largest ovarian follicles, as measured by ultrasound, in IVF patients was found to correlate with DAA measurements.

Analysis of free malondialdehyde in photoirradiated corn oil and beef fat via a pyrazole derivative

Malondialdehyde (MA) formed in linolenic acid, linoleic acid, corn oil and beef fat upon photoirradiation was determined by gas chromatography (GC). The MA produced was reacted with methylhydrazine to give 1-methylpyrazole and was subsequently analyzed on a GC equipped with a nitrogen-phosphorus specific detector and a fused silica capillary column. MA values determined by this method correspond to free or unbound MA levels. Linolenic and linoleic acids produced 867 micrograms MA/g and 106 micrograms MA/g, respectively. Oleic and stearic acids did not produce detectable levels of MA upon photoirradiation. Amounts of MA produced after eight hour irradiations of corn oil and beef fat were 56.24 micrograms/g and 25.01 micrograms/g, respectively. Some photoreaction products in irradiated corn oil also were identified as methylhydrazine derivatives.

Reference values for 75 g oral glucose tolerance test in pregnancy

A 75 g oral glucose tolerance test was performed in 212 pregnant women with no predisposing factors suggesting glucose intolerance to establish the normal pattern of glucose metabolism in pregnancy. Reference values for the test were established for the middle of pregnancy (14-20 weeks, n = 43) and late pregnancy (28-37 weeks, n = 168). One woman was excluded because she had diabetes that required treatment with insulin. There were statistically significant differences between the two groups for samples taken both one and two hours after the glucose load. Reference ranges for the interpretation of the glucose tolerance test in pregnancy should therefore take account of the period of gestation. Arbitrary upper limits of normal (represented by the 97.5 centile) two hours after a 75 g oral glucose load are proposed at 7.5 and 9.6 mmol/l for the second and third trimesters, respectively.

The suppression of ovarian function by the new oral contraceptive--Femodene

Luteinising hormone, oestradiol and progesterone were measured in 36 women commencing Femodene contraception on the first day of menstruation. Of these subjects, 17 were not on any oral contraception during the preceding cycle, the remaining 19 changing from another oral contraceptive formulation. Full measurements were performed in the cycle preceding and the first cycle on Femodene. In another 3 subjects the measurements were made during only one cycle - the first on Femodene. The results confirm ample suppressive effects of Femodene on pituitary and ovarian function. The clinical side effects experienced by the 39 subjects are described.

You see what you look for and recognize what you know

The clinical examination is the cornerstone for all diagnostic and therapeutic decisions. The pertinent components of the history and physical examination as they relate to diabetes are discussed in this article.

A random plasma glucose method for screening for abnormal glucose tolerance in pregnancy

A method is described for screening all pregnant women for abnormal glucose tolerance. It is based on determining random plasma glucose at 28-30 weeks gestation, having simply noted whether the woman had eaten within the preceding 2 h. If the random plasma glucose level was greater than or equal to 97.5th centile, a 75 g oral glucose tolerance test was performed. This method of screening is cheaper and slightly more efficient than screening based on conventional risk indications.

Suppression of ovarian function by Microgynon 30 in day 1 and day 5 "starters"

The suppression of ovulation during the first treatment cycle with Microgynon 30 (150 micrograms levonorgestrel and 30 micrograms ethinyl oestradiol) for nine subjects starting the "pill" on day 1 of their cycle and five subjects on day 5 was investigated. Serum oestradiol and progesterone levels throughout the cycle and midcycle urinary LH levels were reliably suppressed in all day 1 "starters". Serum progesterone levels and urinary LH levels were also suppressed in day 5 "starters" but one subject produced oestradiol levels within the normal range of ovulatory cycles. Mean oestradiol levels of day 5 "starters" were found to be significantly higher than those of day 1 "starters" (p less than 0.05).

Improved separation of motile sperm in asthenospermia and its application to artificial insemination homologous (AIH)

A method is described for the separation of motile sperm from semen by "migration' into a diluent, providing a large area of interface between the semen and the diluent and resulting in a good yield of motile sperm (58%), with a mean percentage of motility of 95%. The method provides a specimen free of seminal plasma and debris and suitable for intrauterine insemination in less than two hours. The motile fraction was used for AIH treatment of 20 couples with a mean of 4 years' infertility, where the female factor had been excluded and the male was asthenospermic. After a mean of six cycles, three pregnancies were achieved. Improvement of the percentage of motility alone did not, in this study, give a significant improvement in conception rates when compared with accepted cycles with the placebo.

Characterization of cloned rat ribosomal DNA fragments

Two Charon 4A lambda bacteriophage clones were characterized which contain all and part o the 18S ribosomal DNA of the rat. One clone contained two Eco RI fragments which include the whole 18S ribosomal RNA region and part of 28S ribosomal RNA region. The other clone contained an Eco RI fragment which covers part of 18S ribosomal RNA region. There were differences between the two clones in the non-transcribed spacer regions suggesting that there is heterogeneity in the non-transcribed spacer regions of rat ribosomal genes. The restriction maps of the two clones were compared to the restriction map of the cloned mouse ribosomal DNA. Eco RI, Hind III, Pst I, and Bam HI sites in 18S ribosomal RNA regions were in the same places in mouse and rat DNA but the restriction sites in the 5'-spacer regions were different.

The Wessex abortion studies: II. Attitudes of consultant gynaecologists to provision of abortion services

Interviews with consultant gynaecologists serving the Wessex region about various aspects of their abortion work revealed considerable variations in attitudes and practice. Although the respondents referred to the same criteria in deciding whether to do an abortion, the assessments they made about the significance of these criteria were more of an individual matter. The variation in assessments partly explains the interdistrict disparities in the availability of N.H.S. abortions.

The Wessex abortion studies: I. Interdistrict variation in provision of abortion services

An analysis of fertility and the provision of abortion and abortion-related services in the health districts of Wessex showed considerable variation between districts in the provision of formal family-planning services. The patterns of fertility varied between the districts and there appeared to be some relationship between family-planning provision and the rates for illegitimate and "legitimated" births and induced abortion. Although the region as a whole was meeting the demand of 42% of its abortion patients within the National Health Service, there was a considerable variation from district to district which could be explained only in part by variations in the provision of resources. The main differences could be accounted for by the attitudes of the women and of their general practitioners and consultants. Of Wessex women obtaining induced abortions privately at the British Pregnancy Advisory Service (B.P.A.S.) clinic at Brighton, 85% said they would have been willing to have an N.H.S. operation locally if one had been available but that no choice had been offered. It is concluded that the differences in provision between the health districts are more likely to be explained by the attitudes of doctors to providing this service than by the wishes of women to use private medical treatment.

The effect of temperature on the velocity of human spermatozoa as measured by time-lapse photography

A method of time-lapse photography for the assessment of sperm velocity is presented. The intersampling variation was not significant, nor was the effect of dilution. Sperm velocity increased with temperature within the range 25 degrees C to 40 degrees C. The possible clinical use of the technique is discussed.

A glucose-controlled insulin infusion system for diabetic women during labour

A glucose-controlled insulin infusion system was used to control blood glucose concentration during labour or caesarean section in six insulin-dependent diabetics. The mean blood glucose concentration during the four hours of labour immediately before delivery was 4.6-5.2 mmol/1 (82.9-93.7 mg/100 ml). Feedback control of insulin delivery by blood glucose concentration should decrease the risk of postpartum hypoglycaemia in the infant and allow normal obstetric management for the insulin-dependent diabetic in labour.

Clinical application of human-placental-lactogen values in late pregnancy

Human-placental-lactogen (H.P.L.) levels were measured in the blood of 1000 women in the third trimester of pregnancy to see how measurement of H.P.L. could help in the management of an obstetric population in Britain. It was found that in the 93% of the population with a mean H.P.L. level of 4.3 mg/l or above, only 1.1% would have a poor pregnancy and 4.8% a compromised pregnancy. Of the 7% with levels below 4.3 mg/l, 57% woul have a normal outcome and 43% a poor or indifferent outcome. The false-positive rate was considerable, but the results of the study indicate nevertheless that H.P.L. levels are useful in predicting the outcome of pregnancy and that their measurement should be included as part of routine screening in the third trimester.

The teaching of medical ethics at Southampton University Medical School

For centuries medical schools in Britain and elsewhere had a fairly static curriculum based on what might be called the 'three Rs' of medicine, and consequently had to make room for new subjects as the need arose in a fashion which was sometimes makeshift. However, Southampton University has only had a medical school for six years, and therefore their course on medical ethics and legal medicine was carefully integrated into the curriculum after some preliminary experiments carried out by a subcommittee which is continually reviewing the situation. Medical ethics has now a definite place in the fourth year, preceded by an introduction to ethical problems encountered in medicine in the first year. Not only do members of the medical faculty participate in this teaching but also members of the faculties of law and the arts.

Sexual knowledge and attitudes of Southampton medical students

A survey of three groups of medical students at the University of Southampton--each group being at a different stage in the course--was carried out in order to establish how far sexual attitudes and knowledge were influenced by the curriculum. Few changes in attitude were recorded, but knowledge of sexual matters was found to have increased in the students who had completed the third year of the course, compared with the level of knowledge assessed in those who were about to begin their course or who had completed the first year. As a result of the survey, some changes have been made in the undergraduate curriculum.

The cellular composition of the human oviduct epithelium

Epithelium from human Fallopian tubes was examined to determine the ratio of ciliated to secretory cells. A comparison was made between results from oviducts from women at different stages of the menstrual cycle, and also between the fimbrial, ampullary and isthmic regions of the oviduct. A high percentage of ciliated cells was found in each case, including the isthmic region, with little difference seen throughout the cycle. The role of cilia in ovum transport is discussed.

Ciliary activity in the human oviduct

Ciliary activity of the human oviduct was investigated using a cinematographic technique. Oviducts from preovulatory, postovulatory and puerperal subjects were analyzed and the fimbrial, ampullary and isthmic regions were compared. It was found that cilia beat more rapidly after ovulation, this difference being significant in both ampullary and isthmic regions, but not in the fimbriae. The implications of these findings are discussed.