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Biomedical subjects

W A Chambers

Publications and source records attributed to W A Chambers.

At least 55 records · Page 3Linked to original sources
PubMed1993

Subarachnoid local anesthetic block does not affect morphine absorption from paired intramuscular and subcutaneous injection sites in the elderly patient.

Morphine absorption from subcutaneous and intramuscular injection sites is dependent on local skin and muscle blood flow. Normally, drug absorption from intramuscular and subcutaneous injections at the same anatomical site is comparable, but spinal anesthesia alters muscle and skin blood flow in the blocked area. This study measured morphine absorption from pairs of intramuscular and subcutaneous injection sites at vastus lateralis and deltoid following a single dose of morphine sulfate in the presence of spinal anesthesia. Differences between the maximum concentration achieved after injection (Cmax) and the time at which this occurred (Tmax) were not significant when absorption for each "same-site" pair of injections was compared, but Tmax after intramuscular injection at vastus lateralis was significantly longer than that observed following either intramuscular or subcutaneous injection at the deltoid (P < 0.05 for both comparisons). Cmax/Tmax ratios and the area under concentration time curve (AUC) also were analyzed, but there were no statistically significant differences among any of the four groups.

Absorption↗
PubMed1992

Continuous collection of pulse oximetry data: a new, inexpensive, portable computerized method.

The availability of reliable pulse oximetry equipment has led to interest in identifying patterns of hypoxaemia in the postoperative period. Methods for the computerized collection and analysis of pulse oximetry data have been described, but these require continuous use of a relatively powerful computer system throughout both the monitoring (data collection) and analysis periods. We have designed a technique which uses a small, portable and relatively inexpensive computer unit for data collection, after which the data may be transferred to a more powerful computer for analysis. Appropriate programming and choice of software have produced a relatively "user friendly" system which can be operated successfully even with minimal computing experience. The unit has the potential to be modified to form the basis of a "medical advice system" which could be used for the "intelligent" monitoring of high risk patients.

Humans↗
PubMed1990

Conjunctival allergen challenge. A clinical approach to studying allergic conjunctivitis.

To evaluate antiallergic agents, we conducted five allergen challenge studies of increasing refinement. The final study design that evolved included two baseline visits, when skin test-positive subjects were administered a bilateral ocular allergen challenge. At the first visit, the threshold dose of reactivity was determined by increasing allergen doses at 10-minute intervals. At the second baseline visit, 3 days later, the responsive subjects were challenged with the final, highest dose used on visit 1 to assure that the allergic reaction was reproducible and not a cumulative effect of multiple allergen doses. The responsive subjects then returned 3 days later for the drug efficacy evaluation. After a slit-lamp examination, subjects were pretreated with the test drug in one eye and the placebo in the fellow eye in a randomized, double-masked fashion. After 10 minutes, subjects were challenged bilaterally with the allergen dose identified on the previous visits. Postchallenge evaluations of hyperemia, itching, chemosis, eyelid swelling, and tearing were performed at 3, 10, and 20 minutes. Subjects were rechallenged 4 hours after drug administration to assess duration of action. Slit-lamp examinations were again performed at the same intervals as after the initial challenge. A total of 396 subjects were given a baseline allergen challenge; 83.6% responded with a moderate (2+) ocular allergic reaction. Of the 266 given a second baseline challenge, 87.2% responded positively again, suggesting that ocular challenge was highly correlated with skin reactivity and reproducible with a second challenge. No statistically significant difference in redness and itching was found when both eyes were challenged with the same dose of allergen.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Pregnancy and the risk of hemorrhage from cerebral arteriovenous malformations.

We conducted a retrospective analysis of 451 women with an arteriovenous malformation (AVM) of the brain to determine whether pregnancy is a risk factor for cerebral hemorrhages. A total of 540 pregnancies occurred among our patient population, resulting in 438 live births and 102 abortions. There were 17 pregnancies complicated by a cerebral hemorrhage. The hemorrhage rate during pregnancy for women with an unruptured AVM was 0.035 +/- 0.005 per person-year. The hemorrhage rate for nonpregnant women of childbearing age with an unruptured AVM was 0.031 +/- 0.002 per person-year. Pregnancy did not increase significantly the rate of first cerebral hemorrhage from an AVM (P = 0.35). We found that women with an AVM face a 3.5% risk of hemorrhage during pregnancy. Pregnancy is not a risk factor for hemorrhage in women without a previous hemorrhage. This conclusion assumes no selection bias exists in our study population; a bias would be introduced if the risk of fatal outcome after a hemorrhage were greater in pregnant women than in nonpregnant women.

Adolescent↗
PubMed1990

Platelet function after intramuscular diclofenac.

A randomised double-blind controlled study was performed to examine the effect of diclofenac on skin bleeding time and in vitro whole blood platelet aggregation. Twenty thoracotomy patients were studied; 10 were given diclofenac 75 mg intramuscularly at induction of anaesthesia, and 10 formed a control group. Skin bleeding times and platelet aggregation tests were performed the day before and repeated one hour after induction of anaesthesia. Diclofenac prolonged skin bleeding time and reduced platelet aggregation. There were no significant changes in the control group.

Adult↗
PubMed1988

Keratoconus. Evaluation of recent trends in the surgical and nonsurgical correction of keratoconus.

Recent focus on the optical correction for "contact lens failure" keratoconus patients has been in the use of epikeratoplasty as an alternative to penetrating keratoplasty. In a 2-year retrospective review of keratoconus patients, 33 were referred as "contact lens failures" and as such might be considered candidates for surgical intervention. Of these, 29 patients (average keratometry, 50.4; range, 43-73) were successfully refitted with contact lenses. All patients obtained wearing times of 12 hours and achieved a visual acuity of 20/40 or better, with 85% realizing 20/30 or better. The data suggest that with concerted effort most keratoconus patients may be successfully refitted despite initial contact lens failure.

Adolescent↗
PubMed1988

Plasma prilocaine concentrations after three techniques of brachial plexus blockade.

Brachial plexus blockade (n = 30: 10 axillary, 10 perivascular subclavian, 10 interscalene) was performed on 28 patients, using 35 ml of 1.5% prilocaine in plain solution. Plasma prilocaine concentrations were measured at intervals over the following 60 min. There was no significant difference in the prilocaine concentrations between the three groups. One asymptomatic patient in the interscalene group had a peak prilocaine concentration greater than the accepted threshold for toxic symptoms.

Brachial Plexus↗
PubMed1988

Corneal ulcers in house staff: are risk factors identifiable?

Thirty-six incoming house officers and 20 incoming third-year medical students had conjunctival cultures taken before and after hospital exposure. The groups were divided evenly between contact-lens and noncontact-lens wearers. A decrease in incidence of positive conjunctival cultures was observed after hospital exposure. Within this group, a lower incidence of positive cultures was observed in contact-lens wearers compared with noncontact-lens wearers. The clinical records of corneal ulcer patients during a three-year period from October 1982 through October 1985 were also reviewed. Significant associated risk factors were identified, the largest of which was contact-lens wear.

Adolescent↗
PubMed1986

Effects of the addition of potassium to prilocaine or bupivacaine. Studies on brachial plexus blockade.

A double-blind comparison of prilocaine and prilocaine plus potassium chloride, and of bupivacaine with bupivacaine plus potassium chloride, in brachial plexus blockade (axillary approach) was obtained in two groups of 20 patients. The addition of potassium chloride made no difference to the characteristics of the block with prilocaine, but resulted in a more rapid onset of sensory loss when added to bupivacaine.

Adjuvants, Anesthesia↗
PubMed1983

Extradural morphine for the relief of pain following caesarean section.

Thirty patients took part in a double-blind trial to compare morphine 10 mg i.m. with morphine 5 mg into the extradural space for pain relief following Caesarean section. With the extradural route the mean time to first analgesia was 7.95 h compared with 4.75 h for the i.m. route. The mean number of further doses of diamorphine 7.5 mg required for pain relief in the first 24 h was 1.93 (+/- 0.30) in the i.m. group and 1.46 (+/- 0.31) in the extradural group. There was a small but definite advantage in the use of the extradural route for the initial dose of morphine. No serious side-effects were noted in either group.

Anesthesia, Epidural↗
PubMed1983

Spinal anesthesia with tetracaine--effect of added vasoconstrictors.

The effect of adding 0.2 ml of 1:1000 epinephrine or 0.5 ml of 1% phenylephrine to 1.5 ml of 1% tetracaine for spinal anesthesia was assessed in 30 patients in a double-blind study. Phenylephrine but not epinephrine produced a significant prolongation of sensory loss in the T12 dermatome. Both vasoconstrictors produced a significant prolongation of the total duration of sensory and motor blockade. These findings differ from those in previous studies in which lidocaine and bupivacaine were used.

Aged↗
PubMed1982

Spinal anaesthesia with hyperbaric bupivacaine: effects of concentration and volume administered.

A double-blind study was carried out using hyperbaric solutions of bupivacaine to compare the effects of varying the concentration of bupivacaine and the volume of solution administered intrathecally. Fifty-seven patients were studied. Ten patients received each volume of each concentration: 0.5% bupivacaine in 8% dextrose, 2 ml, 3 ml or 4 ml and 0.75% bupivacaine in 8% dextrose, 1.3 ml or 2 ml. A further seven patients received 3 ml of the 0.75% solution. Both solutions consistently produced good nerve blockade. With the 0.5% solution, increases in the volume administered had no effect on the spread of sensory loss, whereas with the 0.75% solution, increasing the volume administered resulted in a significantly greater cephalad spread. The use of 3 ml of this solution was abandoned after seven patients had received it because of the excessive spread. With both solutions, increasing the volume produced a longer duration of action. The use of a 0.75% solution of hyperbaric bupivacaine for spinal anaesthesia did not appear to confer any advantage over the 0.5% solution.

Anesthesia, Spinal↗
PubMed1982

Spinal anesthesia with hyperbaric bupivacaine: effect of added vasoconstrictors.

The effect of adding 0.2 ml of 1:1000 epinephrine or 0.5 ml of 1% phenylephrine to 3 ml of 0.5% bupivacaine in 8% dextrose for spinal anesthesia was assessed in 30 patients in a double-blind study. The addition of phenylephrine gave a small prolongation of the block which was not statistically significant. Although epinephrine produced a greater prolongation, this only reached statistical significance with regard to total duration. Three patients who received solutions that contained a vasopressor had prolonged blocks, but these solutions could not be relied upon to produce consistently a clinically significant increase in duration in individual patients.

Aged↗
PubMed1981

Closing volume in normal pregnancy.

Closing volume and other principal lung volumes were measured during and after pregnancy in 10 healthy non-smoking women aged 18--25 yr. There were no significant changes on closing volume or closing capacity. A decrease in functional residual capacity as pregnancy progressed resulted in airway closure during tidal breathing in more than 50% of subjects at term when in a supine position, but this did not occur when they were seated.

Adolescent↗
PubMed1981

Effect of baricity on spinal anaesthesia with bupivacaine.

In a double-blind study of spinal anaesthesia with 0.5% bupivacaine 3 ml with no glucose, 5% glucose or 8% glucose all three solutions gave consistently good nerve blocks. The hyperbaric solutions (5% and 8% glucose) produced a greater cephalad spread and were suitable for lower abdominal surgery, whereas the plain solution (no glucose) seldom affected the thoracic nerves. Cardiovascular changes were more marked with the hyperbaric solutions but only necessitated treatment on two occasions. The duration of block was not affected by baricity and was in the range 140-160 min.

Adolescent↗