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Biomedical subjects

A P Winnie

Publications and source records attributed to A P Winnie.

At least 19 recordsLinked to original sources
PubMed1992

A comparative study of 0.25% ropivacaine and 0.25% bupivacaine for brachial plexus block.

The present study compares the effectiveness of 0.25% ropivacaine and 0.25% bupivacaine in 44 patients receiving a subclavian perivascular brachial plexus block for upper extremity surgery. The patients were assigned to two equal groups in this randomized, double-blind study; one group received ropivacaine 0.25% (112.5 mg) and the other, bupivacaine 0.25% (112.5 mg), both without epinephrine. Onset times for analgesia and anesthesia in each of the C-5 through T-1 brachial plexus dermatomes did not differ significantly between the two groups. The mean onset time for analgesia ranged from 11.2 to 20.2 min, and the mean onset time for anesthesia ranged from 23.3 to 48.2 min. The onset of motor block differed only with respect to paresis in the hand, with bupivacaine demonstrating a shorter onset time than ropivacaine. The duration of sensory and motor block also was not significantly different between the two groups. The mean duration of analgesia ranged from 9.2 to 13.0 h, and the mean duration of anesthesia ranged from 5.0 to 10.2 h. Both groups required supplementation with peripheral nerve blocks or general anesthesia in a large number of cases, with 9 of the 22 patients in the bupivacaine group and 8 of the 22 patients in the ropivacaine group requiring supplementation to allow surgery to begin. In view of the frequent need for supplementation noted with both 0.25% ropivacaine and 0.25% bupivacaine, we do not recommend using the 0.25% concentrations of these local anesthetics to provide brachial plexus block.

Adult↗
PubMed1991

Baricity and the distribution of lidocaine in a spinal canal model.

The role of the baricity of local anaesthetic solutions in determining the distribution of local anaesthetics injected into the subarachnoid space (and hence the level of anaesthesia) has been challenged. A recent study found no difference in the extent of cephalad spread of hyperbaric and isobaric solutions and concluded that density had no effect on the spread of local anesthetics. The present study, to determine the validity of this conclusion, utilized a spinal model filled with a "cerebrospinal fluid equivalent." Following the injection of hyperbaric lidocaine, the local anaesthetic was most concentrated at the lower end of the column, whereas following the injection of isobaric solution the local anaesthetic was most concentrated around the site of injection. Therefore, baricity is an important determinant of local anaesthetic distribution in the subarachnoid space.

Atmospheric Pressure↗
PubMed1991

Piriformis muscle syndrome: an underdiagnosed cause of sciatica.

This is a retrospective review of 26 patients with sciatica due to the piriformis muscle syndrome. Most patients had pain in the buttock area and sciatica, and most experienced difficulty walking and sitting, even for short periods of time. Reproduction of the sciatica upon deep palpation, either by gluteal or rectal route, was diagnostic. Reproduction of sciatica occurred in 92% of the patients upon deep digital palpation and in 100% of the patients upon rectal or pelvic examination. Other signs were helpful but not consistent. After the appropriate diagnosis, the treatment was relatively easy and rewarding. This study emphasizes that the diagnosis of piriformis muscle syndrome is clinical; without the appropriate clinical examination, it can be easily misdiagnosed.

Adult↗
PubMed1991

A complete regional anesthesia technique for cardiac pacemaker insertion.

Sixteen consecutive adult patients scheduled for permanent transvenous cardiac pacemaker insertion received as their total anesthetic the combination of a cervical plexus block and blocks of the second, third, and fourth intercostal nerves using a combination of 1% mepivacaine and 0.2% tetracaine with epinephrine, 1:200,000. This technique consistently provided complete surgical anesthesia of the third cervical (C3) through the fourth thoracic (T4) dermatomes, without anesthesia of the brachial plexus. Anesthesia was adequate for the surgical procedure without the need for supplemental analgesia or anesthesia in all cases. Because fluoroscopy was used routinely for the surgical procedure, it was possible to document that there were no instances of diaphragmatic paralysis or pneumothorax. In contrast to other reports, this technique provides surgical anesthesia that is adequate for all of the approaches used for transvenous pacemaker implantation, except for placement of a battery in an abdominal pouch. There were no serious complications and/or side effects in any of the patients studied.

Aged↗
PubMed1990

Brachial plexus block with a new local anaesthetic: 0.5 per cent ropivacaine.

A new local anaesthetic, ropivacaine hydrochloride, was used in a concentration of 0.5 per cent in 32 patients receiving a subclavian perivascular block for upper extremity surgery. One group (n = 15) received 0.5 per cent ropivacaine without epinephrine and a second group (n = 17) received 0.5 per cent ropivacaine with epinephrine in a concentration of 1:200,000. Anaesthesia was achieved in 87 per cent of the patients in both groups in all of the C5 through T1 brachial plexus dermatomes. Motor block was profound with 100 per cent of patients in both groups developing paresis at both the shoulder and hand and 100 per cent developing paralysis at the shoulder. There was a rapid initial onset of sensory block (a mean of less than four minutes for analgesia) with a prolonged duration (a mean of greater than 13 hr of analgesia). The addition of epinephrine did not significantly affect the quality or onset of sensory or motor block. The duration of sensory block was reduced by epinephrine at T1 for analgesia and at C7, C8, and T1 for anaesthesia. The duration of sensory block in the remaining brachial plexus dermatomes as well as the duration of motor block was not effected by epinephrine. There was no evidence of cardiovascular or central nervous system toxicity in either group with a mean dose of 2.5-2.6 mg.kg-1 ropivacaine.

Adult↗
PubMed1989

Clinical pharmacokinetics of carbonated local anesthetics. III: Interscalene brachial block model.

To compare serum levels of lidocaine resulting from 1.1% lidocaine carbonate and 1.0% lidocaine hydrochloride, the two salts were administered to ten healthy adult patients undergoing upper extremity surgery under interscalene brachial plexus block. Epinephrine (1:200,000) was added to both the solutions just prior to injection, and, following performance of the blocks, venous blood samples were drawn at 3, 5, 10, 15, 20, 30, 60 and 120 minutes. The concentration of lidocaine tended to rise more rapidly and to achieve higher levels in the first 10 minutes following injection of the carbonated lidocaine. However, no significant differences were found in the parameters of Cmax, Tmax or AUC for the two salts, and the serum levels in both groups at all times were well below the levels known to produce systemic toxicity. Therefore, while previous studies appear to indicate that the carbonate salt enhances diffusion, penetration, and uptake of neural tissues as compared with the hydrochloride salt, the present study indicates that vascular uptake is not similarly affected.

Adult↗
PubMed1989

Ketamine for intravenous regional anesthesia.

We studied ketamine intravenous regional anesthesia of the upper extremity in volunteers using concentrations of 0.5%, 0.3%, and 0.2%. Ketamine 0.5 and 0.3% produced adequate intravenous regional anesthesia. Anesthesia was inadequate when a 0.2% concentration was used. However, although the 0.3% concentration provides complete sympathetic, sensory, and motor blockade when injected into the isolated extremity, unpleasant psychotomimetic effects after the release of the tourniquet limit the usefulness of this use of ketamine. Ketamine cannot be recommended for intravenous regional anesthesia unless these unpleasant side effects are abolished or controlled by means of pharmacologic adjuvants.

Adult↗
PubMed1989

Lidocaine disposition following intravenous regional anesthesia with different tourniquet deflation technics.

It has been claimed that tourniquet cycling, cyclic deflation and reinflation of the tourniquet at the termination of intravenous regional anesthesia (IVRA), enhances the safety of IVRA by minimizing the peak blood level of local anesthetics. To evaluate the validity of these claims and to determine the optimal cycling technic, peak arterial (Cmax) plasma concentrations of lidocaine were determined as well as the time to reach these peaks (Tmax) utilizing contralateral radial arterial blood samples in three groups of volunteers after 30 minutes of IVRA: In all three groups IVRA was induced with 3 mg/kg of lidocaine and maintained for 30 min. In the first group the tourniquet was then simply deflated once (and not reinflated); in the second group the tourniquet was deflated three times with variable periods of deflation (0, 10 and 30 seconds) separated by 1-minute periods of reinflation; and in the third group the tourniquet was again deflated 3 times but with fixed periods of deflation (10 sec) separated by 1 min periods of reinflation. The results obtained indicate that cycling technics do not appear to significantly reduce Cmax, but they do significantly prolong Tmax. Of the two cycling technics, the 10-second deflation interval technic appeared to be superior, both clinically and pharmacologically, as it was associated with less venous congestion and therefore less discomfort, and it sequentially decreased the arterial plasma concentration of lidocaine with each subsequent deflation-reinflation cycle.

Adult↗
PubMed1988

Incidence and etiology of failed spinal anesthetics in a university hospital: a prospective study.

Two recent retrospective reports on the incidence of failed spinal anesthetics that indicated extremely variable results prompted the present prospective study of 200 consecutive spinal anesthetics to determine the incidence and causes of failed spinal anesthetics. Tetracaine was the spinal anesthetic agent utilized in all cases--crystalline tetracaine (Niphanoid) in 71% and a 1% solution in 19% of the cases. The failure rate overall was 4%, with all failures being due to anesthetic factors, both technical and pharmacologic. However, only 25% of the failures were due to errors in technique, and 75% were due to errors in judgment with respect to pharmacologic factors (dosage, use of epinephrine, and/or positioning of the patient). Our data, therefore, differ from those of Levy et al. (Anesth Analg 1985;64:705-10), both in terms of failure rate, which is 25% of theirs, and in terms of causation, with our data indicating errors in judgment to be the causative factor three times as often as errors in technique. Presumably, this difference is due to the greater experience in spinal anesthesia that a resident receives at our institution.

Adolescent↗
PubMed1987

Clinical pharmacokinetics of carbonated local anesthetics. I: Subclavian perivascular brachial block model.

Fifty healthy adult patients undergoing upper extremity surgery under brachial plexus anesthesia provided by the subclavian perivascular technique were divided into two groups, so that anesthesia provided by 1% lidocaine hydrochloride in one group could be compared with that provided by 1.1% lidocaine carbonate in the other group. Epinephrine, 1:200,000, was added to both solutions just before injection. Carbonated lidocaine reduced the latency of anesthesia by 45% as compared with the hydrochloride salt and produced complete motor block in almost twice as many patients (54 vs 31%). The duration of anesthesia provided by the two agents was virtually identical, as was duration of motor blockade.

Adult↗
PubMed1987

Clinical pharmacokinetics of carbonated local anesthetics. II: Interscalene brachial block model.

A double-blind comparison of 1.1% lidocaine carbonate and 1.0% lidocaine hydrochloride was carried out in 30 healthy adult patients undergoing upper-extremity surgery under interscalene brachial plexus block. Epinephrine (1:200,000) was added to both solutions just before injection. As compared to lidocaine hydrochloride, lidocaine carbonate produced, in addition to a 38% reduction in onset time, a remarkable increase in the extent of anesthesia: lidocaine carbonate produced surgical anesthesia of the entire upper extremity including the hand in 87% of the patients, whereas lidocaine hydrochloride produced similar anesthesia in only 53% of the patients. Thus, supplemental blocks were required in 66% of the patients who received lidocaine hydrochloride, whereas they were required in only 25% of those who received lidocaine carbonate.

Adult↗
PubMed1987

Nalbuphine as an analgesic component in balanced anesthesia for cardiac surgery.

The efficacy and safety of nalbuphine hydrochloride as an IV analgesic used in combination with pretreatment and supplemental doses of diazepam with and without N2O were assessed in 15 patients scheduled to undergo aortocoronary bypass (n = 11) or valve replacement surgery (n = 4). The loading infusion of 3.0 mg/kg nalbuphine given in 20 min 5 min after conclusion of IV injection of 0.4 mg/kg/5 min diazepam caused no significant changes in systolic or diastolic systemic and pulmonary arterial blood pressures or in heart rate, cardiac index, stroke index, systemic and pulmonary vascular resistance, or right and left ventricular stroke work index. After the initial 1-hr loading infusion of 6.66 +/- 0.89 mg/kg nalbuphine (mean +/- SE), additional nalbuphine infusion maintenance doses of 4.73 +/- 0.77, 1.87 +/- 0.31, 2.16 +/- 0.23, 1.65 +/- 0.22, and 2.35 +/- 0.44 were used in the subsequent hourly periods to maintain a pain-free state throughout surgery. Hemodynamic changes during the three most stressful periods, tracheal intubation, skin incision, and sternotomy, were not statistically significant. Normal plasma catecholamine and cortisol levels indicate that these patients experienced neither stress nor pain during the maintenance of anesthesia. Nalbuphine caused no significant histamine release. All patients had uncomplicated maintenance of and emergence from anesthesia.

Adult↗
PubMed1985

The inhibitory effect of glycopyrrolate on human plasma-cholinesterase.

The in vitro inhibitory effect of glycopyrrolate and atropine on the hydrolysis of benzoylcholine at 50.0 microM concentration was determined in the plasma of 6 healthy volunteers at 37 degrees C and at 240 nm by the ultraviolet spectrophotometric method of Kalow. The 50 per cent inhibitory concentration (I50) of glycopyrrolate was found to be 1.0 mM and the I50 of atropine was 0.9 mM. This inhibitory effect of glycopyrrolate and atropine is moderate but its interaction with the in vivo hydrolysis of succinylcholine or that of ester-type of local anaesthetics in patients should be further studied. Although both glycopyrrolate and atropine inhibit PChE to the same extent, glycopyrrolate should be utilized in patients in whom inhibition of brain PChE or central effects ought to be avoided, since glycopyrrolate does not penetrate the blood-brain barrier.

Atropine↗