Fetal umbilical artery flow velocity waveforms and placental resistance: clinical significance

Summary. Since the umbilical arteries carry fetal blood to the placenta we studied flow velocity waveforms in these vessels with a simple continuous wave Doppler system to assess placental blood flow. The ratio of peak systolic to least diastolic (A/B) flow velocity was measured as an index of placental flow resistance. In 15 normal pregnancies there was a small but significant decrease in this ratio through the last trimester. The A/B ratio was measured on 436 occasions in 168 high-risk pregnancies. In 32 of 43 fetuses subsequently shown to be small for gestational age there was an increase in placental flow resistance with reduced, absent or even reversed flow in diastole. This finding was also present in the one fetus which died in utero . Serial studies in patients with fetal compromise indicated increasing flow resistance, a reverse of the normal trend. These results were not available to the clinician yet of 24 fetuses born before 32 weeks 13 had a high A/B ratio, and all of them were born electively. Maternal hypertension was associated with an increase in fetal placental flow resistance. The umbilical artery A/B ratio provides a new and non-invasive measure of fetoplacental blood flow resistance.     

URODYNAMIC FACTORS INFLUENCE THE DURATION OF ESCHERICHIA COLI BACTERIURIA IN DELIBERATELY COLONIZED CASES

Purpose

We evaluated the influence of urodynamic factors on the establishment of bacteriuria, after deliberate intravesical inoculation with Escherichia coli.

Materials and Methods

Nine women and 7 men with recurrent symptomatic urinary tract infections underwent intravesical injection of E. coli 83972. This strain had documented ability to persist in the urinary tract and it lacks expressed virulence factors associated with urinary tract infection.

Results

Successful long-term colonization (5 months to 3 years) was achieved in 6 of 12 patients with neurogenic bladder disorder, including normal or high bladder capacity, normal or low detrusor pressure and residual urine. Short-term bacteriuria (13 days) occurred in 1 but long-term bacteriuria was not established in the 4 patients with normal lower urinary tract function. Occasionally urine samples from the colonized patients contained other bacterial strains, which cleared spontaneously except for a Klebsiella strain that became established in 2 and subsequently eliminated E. coli 83972.

Conclusions

E. coli 83972 bacteriuria could only be established in a subset of patients with defective bladder voiding, suggesting that urodynamic defects permit a nonvirulent strain to establish in the urinary tract, but that additional host factors determine if bacteriuria will persist.     

Subchronic and Reproduction Studies with Dibutyl Phenyl Phosphate in Sprague-Dawley Rats

Dibutyl phenyl phosphate (DBPP) was administered to male andfemale. Sprague-Dawley rats in their diets in separate subchronic(91-day) and two-generation reproduction studies. Dose levelsof DBPP were 5, 50, and 250 mg/kg/day in both studies. In thereproduction study, cross-fostering was performed between somehigh-exposure and control litter offspring and dams followinga second mating of F₀ animals. Compared to control animals,body weights were consistently lower in high-exposure adultanimals in both studies; this observation was less consistentin mid-exposure adult rats. High-exposure rats in the subchronicstudy had decreased erythrocyte counts and hematocrit and hemoglobinlevels. They also had increased absolute and/or relative liverweights with concomitant decreased hepatocytic vacuolation andincreased fatty accumulation. In the reproduction study, matingand fertility indices were comparable among the parental animalsin both generations, but survivability among high-exposure pupsreared by control dams appeared to be decreased. Urinary bladderhistopathologic changes, consisting of mononuclear cell infiltrationand transitional epithelial hyperplasia, were noted in mid-and high-exposure rats from both studies. The no observableadverse effect level in both of these studies was 5 mg/kg/ day.     

Inhibition of 5-hydroxytryptamine re-uptake impairs human gall-bladder emptying

Background: 5-Hydroxytryptamine (5-HT) is an important neurotransmitter in the enteric nervous system. The intrinsic neural plexus of the gall-bladder resembles the enteric nervous system and similarly contains 5-HT neurones. The action of 5-HT on gallbladder motility has been investigated in animals but its effect on the human gall-bladder in vivo is unknown. Methods: The effect of indirect 5-HT agonism using paroxetine, a specific inhibitor of neuronal 5-HT reuptake, on gall-bladder motility was investigated in 12 healthy volunteers. In a randomized double-blind crossover design, gall-bladder motility was assessed after administration of 30 mg paroxetine daily for two days and after placebo. Ultrasonography was used to determine gall-bladder volumes while fasting and at 5 min intervals following a 250 kcal mixed liquid meal. Results: Fasting gall-bladder volumes of 21.8 ± 3.2 ml on placebo and 28.0± 3.5 ml on paroxetine were similar. Paroxetine impaired postprandial gall-bladder emptying. Residual gall-bladder volume was 10.2 ±2.7 ml with placebo and 17.1±2.7 ml with paroxetine (P < 0.05). Ejection fraction was 57.3 ±7.7% on placebo and 40.9 ± 4.7% on paroxetine (P < 0.05). Conclusion: 5-HT pathways may participate in the regulation of biliary motility, and this study demonstrates an inhibitory role of 5-HT in the control of human gall-bladder emptying.     

CHANGES IN THE POWER SPECTRUM OF THE EVOKED COMPOUND ACTION POTENTIAL OF THE ADDUCTOR POLLICIS WITH THE ONSET OF NEUROMUSCULAR BLOCKADE

The effects of neuromuscular blockade by atracurium and vecuroniumon the power spectrum of the evoked compound action potential(ECAP) of the adductor pollicis were investigated in 30 adultpatients undergoing elective surgery. The changes in amplitudeand mean power frequency (MPF) of the ECAP were measured. Tenpatients received an ED₉₅ (0.23 mg kg^–1) of atracuriumand 10 received an ED₉₅ (0.055 mg kg^–1) of vecuronium.The remaining 10 patients did not receive any neuromuscularblocking drug, and were monitored for 6 min to exclude any time-relatedchanges in the ECAP. Neuromuscular blockade produced a decreasein total power and a shift towards lower frequencies. This wasreflected in a decrease in the MPF in those patients receivingatracurium or vecuronium. There was no significant difference(P < 0.05) between the atracurium and vecuronium groups inthe magnitude of the change in MPF. These findings suggest thatthe previously reported increase in the duration of the negativedeflection of the ECAP is predominantly the result of a changein its frequency components.     

EFFICIENCY OF AN ENCLOSED AFFERENT RESERVOIR BREATHING SYSTEM DURING CONTROLLED VENTILATION

We describe an enclosed afferent reservoir (EAR) breathing systemdeveloped by Ohmeda and designed to operate efficiently in spontaneousand controlled ventilation. The efficiency of the system wasevaluated by calculating the fractional utilization of freshgas in 10 ASA I–III patients during anaesthesia with controlledventilation. Maximum efficiency occurred when the minute ventilationto fresh gas flow ratio was greater than 1.5. Under these conditions,fractional utilization was relatively constant with a valueof 0.73 (95% confidence interval 0.69–0.78). The minimumfresh gas flow for use during controlled ventilation was determinedin another eight ASA I–III patients when the minute volumeto fresh gas ratio was greater than 1.5. In view of an increasedarterial to end-tidal carbon dioxide partial pressure differencein patients in the first part of the study (1.03 kPa), normocapniawas defined as an end-tidal carbondioxide partial pressure of4.3 kPa. Normocapnia was achieved with a mean fresh gas flowof 66 ml kg^–1 min^–1, while 70 ml kg^–1 min^–1produced mild hypocapnia.