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Biomedical subjects

K Armstrong

Publications and source records attributed to K Armstrong.

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

Diagnostic accuracy and clinical utility of fine-needle aspiration cytology in the diagnosis of clinically primary bone lesions.

Optimal treatment of primary bone sarcomas requires minimal disturbance of the tumor prior to preoperative radiation and chemotherapy. Currently, carefully planned incisional or cutting needle biopsies are the favored methods for procurement of specimens. Recently, fine-needle aspiration has gained favor as the initial diagnostic procedure at some centers. We investigated the diagnostic accuracy and the effects of errors in diagnosis and of complications on the patient's course in a series of 101 patients presenting with lesions clinically believed to have arisen in bone. We found that 29% of aspirates were insufficient for the diagnosis; 41% of aspirates yielded a correct diagnosis that had a significant favorable impact on the patient's course, while 20% of aspirates gave a correct diagnosis that did not significantly influence therapy. In 7% of cases, the aspirates were associated with an incorrect diagnosis that negatively influenced therapy, and in an additional 3% of cases an incorrect diagnosis was obtained that had no impact on patient outcome. No complications were encountered in this series of patients.

Biopsy, Needle↗
PubMed1993

Effects of isoflurane dose, duration of anoxia, and reoxygenation on isoflurane's preservation of energy balance in anoxic isolated hepatocytes.

We investigated how the protection of energy status by isoflurane in isolated hepatocytes varied with isoflurane dose, duration of anoxia, and reoxygenation. Hepatocytes were isolated from fed rats and incubated in Krebs buffer under O2/CO2 or N2/CO2 (95/5) for 30 or 90 min, followed by 5 or 30 min of reoxygenation. From measurements of adenosine tri-, di-, and monophosphate (ATP, ADP, AMP) in the cells, energy charge (= [ATP + 1/2 ADP]/[ATP + ADP + AMP]) was calculated to reflect the balance between ATP supply and demand, and total adenine nucleotide (= ATP + ADP + AMP) to indicate the potential maximum ATP level. During 30 min of anoxia, energy charge and total adenine nucleotide steadily increased with isoflurane dose from 0 to 2 minimum alveolar anesthetic concentration, then decreased from 2 to 3 minimum alveolar anesthetic concentration. In short incubations (30-35 min) at 1 minimum alveolar anesthetic concentration isoflurane, there was a modest decrease in energy charge during anoxia, partially prevented by isoflurane and completely reversed by reoxygenation, and no decrease in total adenine nucleotide. In long incubations (90-120 min), there were large decreases in both energy charge and total adenine nucleotide during anoxia, with partial and no reversal by reoxygenation, respectively. Isoflurane partly prevented decreases in both energy charge and total adenine nucleotide during both anoxia and reoxygenation. We conclude that at doses in the clinical range, isoflurane partially protected isolated hepatocytes against decreases in both energy charge and total adenine nucleotide occurring either during short (reversible) or long (irreversible) anoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
PubMed1992

The why, when and whether of condom use among female and male drug users.

Eight focus groups consisting of all male, all female and mixed male and female drug users were conducted to gain an in-depth understanding of beliefs and behavior regarding the use of family planning services and contraceptives, particularly condom use in an effort to reduce the perinatal transmission of HIV. While participants often supported the use of condoms because of STDs and AIDS, their unplanned pregnancies and STD histories indicated in-consistent use, depending on the partner and the circumstances. The vast majority of both men and women did not like to use condoms because it interfered with the spontaneity and pleasure of sexual relations, though women seemed more willing to use condoms than their partners. Participants varied in their knowledge about the benefits of using a condom, in how and when to put it on, in the associations they made between condom use and trust and commitment, in the type of partner and conditions under which they would use condoms and in their willingness to consider condom use as an integral part of their lives. Issues of trust, commitment and condom use did not seem to have been resolved in the drug using community, particularly among younger people who appeared to have more difficulty in negotiating condom use. Promoting the use of condoms needs to be considered as part of a larger, multifaceted behavior change effort.

Condoms↗
PubMed1988

Pitfalls in the use of a continuous performance test as a diagnostic tool in attention deficit disorder.

Although automated continuous performance tests (CPT) are gaining popularity as aids to the diagnosis of attention deficit disorder (ADD), little is known of their validity in this context. Our preliminary experience with a commercially available visual CPT indicated that as many as a third of children meeting the DMS-III criteria for ADD may score well enough on this measure to escape detection. We therefore analyzed the results of neuropsychological testing as well as CPT performance in 14 ADD children and six non-ADD children in an effort to determine whether CPT performance might reflect higher level cognitive variables other than attention and/or impulsivity. We found that those ADD children classified as "abnormal" on the basis of the CPT scored significantly below those classified as "normal" on measures of abstract reasoning and logical problem solving, simple verbal reasoning, nonverbal problem solving, and simple arithmetic skills. The non-ADD group contained a high proportion (83%) of subjects with CPT performance outside of the normal range. These data suggest that CPT may yield both false negative and false positive results when used as screening tools for ADD, and we recommend therefore that caution be used in their interpretation.

Adolescent↗
PubMed1988

Popliteal vascular injuries and war: are Beirut and New Orleans similar?

Trauma to the lower extremity associated with fracture and vascular injury has a high reported incidence of limb loss. This study reviews and contrasts the experience at Tulane University affiliated hospitals (TU) and the American University of Beirut (AUB) (1980 to 1984), both of which are surrounded by hostile action. Seventy-six male patients (28--AUB, 48--TU) with an average age of 21.2 (TU) and 24.4 (AUB) years (range, 17 to 42) presented with popliteal artery injuries with (34 [14--AUB; 20--TU] ) and without (42 [14--AUB; 28--TU]) associated fractures. All patients were clinically evaluated, angiogrammed, begun on cephalosporin antibiotics, and operated upon. Fractures were treated with extraskeletal fixation or splinting. Time of initiation of operative therapy varied from less than one to greater than 12 hours. When necessary, contralateral limb reversed saphenous vein was used as an interposition graft. Fasciotomies were done for popliteal artery injuries with greater than 6 hours' ischemic time, and combined popliteal artery and popliteal vein injuries. Nine limbs of 76 at risk were amputated: 5/34 (2/14--AUB; 3/20--TU) with popliteal injuries and fractures, and 4/42 (1/14--AUB; 3/28--TU) with popliteal injuries and without fractures. Five of the amputated limbs had initiation of therapy at greater than 12 hours; three had initiation of therapy at greater than 8 hours. Good communication between surgeons, prompt fracture reduction, antibiotics, angiography, and total repair of the vascular injury resulted in limb salvage in 30/40 patients with popliteal artery injury and fracture, and in 39/42 patients with popliteal artery injury without fracture.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Encainide for refractory supraventricular tachycardia in children.

Fifteen children, aged 5 days to 19 years (mean 4.7 years), with medically refractory supraventricular tachycardia were given oral encainide. In 10 of 15 children with "incessant" tachycardia (greater than 10% of the day), encainide alone controlled supraventricular tachycardia in 5 children; in combination with other antiarrhythmic agents, it partially controlled supraventricular tachycardia in 4 and was ineffective in 1. In 5 children with accessory atrioventricular connections, encainide eliminated supraventricular tachycardia in 3 and was ineffective in 2. Therapeutic encainide dosages ranged from 60 to 120 mg/m2/day (mean 90) (2.0 to 5.7 mg/kg/day). Encainide caused prolongation of the PR interval by 35%, RP interval by 17%, QRS interval by 44% and corrected QT interval by 10%. In 5 children with depressed left ventricular function administration of encainide, by controlling the arrhythmia, increased echocardiographic left ventricular shortening fraction from a mean of 24% to a mean of 36%. Three patients developed excessive QRS aberrancy, which was associated with wide QRS tachycardia in 2. No adverse reactions were noted in the absence of QRS aberration. Side effects were minor and noted in only 1 of 9 patients continuing to take the drug in 9 months of follow-up. Encainide was effective, or partially effective, in the control of resistant or incessant supraventricular tachycardia in 80% of children treated. Encainide allowed rapid resolution of arrhythmia-induced cardiomyopathy by controlling chronic supraventricular tachycardia.

Adolescent↗
PubMed1985

Clinical experience, complications, and survival in 70 patients with the automatic implantable cardioverter/defibrillator.

Seventy patients received the automatic implantable defibrillator, five original devices and 72 modified second-generation devices using only bipolar rate sensing and delivering an R wave synchronous cardioverting/defibrillating shock, for either ventricular tachycardia or fibrillation. The primary clinical arrhythmia was sustained ventricular tachycardia in 32 patients, ventricular fibrillation in 20 patients, and both ventricular tachycardia and fibrillation in 18 patients. Before implantation of the device the patients had survived 3.1 +/- 2.3 arrhythmic episodes, including 1.9 +/- 1.7 cardiac arrest, and had received 4.0 +/- 2.1 antiarrhythmic drugs without improvement. Sixty-eight patients ultimately received devices. After a follow-up period of 8.9 +/- 7.7 months (range 1 to 33), 37 patients received a total of 463 discharges. Inability to determine the precise reason for most discharges and the unpleasant nature of the discharges were the major clinical problems encountered. Complications included postoperative death (one patient), lead problems (six patients), inadequate energy requiring explanation (two patients), and pocket infection (one patient. Life-table analysis revealed 6 and 12 month cardiovascular survival of 95.0% and 89.9% and sudden death survival of 98.2%. In our experience, survival with the automatic implantable cardioverter/defibrillator exceeds that with other forms of therapy.

Arrhythmias, Cardiac↗
PubMed1984

Measurement of cardioversion/defibrillation thresholds in man by a truncated exponential waveform and an apical patch-superior vena caval spring electrode configuration.

Defibrillation/cardioversion thresholds were measured in 33 patients undergoing defibrillator implants. Each patient had a 12 cm2 patch placed near the left ventricular apex via a thoracotomy and a 10 cm2 spring lead placed pervenously at the right atrial-superior vena caval junction. Ventricular tachycardia of stable morphology, polymorphic ventricular tachycardia, or ventricular fibrillation was induced four times in each patient and 1, 5, 10, and 25 J truncated exponential shocks with 60% tilt were given in a random sequence. The conversion rate was constant (77%, 86%, 87%, 85%) with increasing energy for ventricular tachycardia but progressively increased for polymorphic ventricular tachycardia and ventricular fibrillation (8%, 33%, 58%, 92%). The ventricular tachycardia acceleration rates for 1, 5, 10, and 25 J were 23%, 14%, 10%, and 15%. Patients not reliably converted with 25 J may require repositioning of leads or two patches. We conclude that for the spring-patch electrodes, increasing energy from 1 to 25 J improves the conversion rate for polymorphic ventricular tachycardia and ventricular fibrillation; the ventricular tachycardia conversion rate is constant. Acceleration of ventricular tachycardia occurs at all energies. Defibrillator implantation requires extensive intraoperative electrophysiologic testing to ensure safe and reliable termination of ventricular tachycardia and fibrillation.

Adult↗
PubMed1982

Preferential site-dependent cleavage by restriction endonuclease PstI.

The four identical recognition sites for the restriction endonuclease PstI in purified plasmid pSM1 DNA I are cleaved at markedly different rates. The order and relative frequencies of cleavage at these four PstI sites have been determined from the order of appearance of partial cleavage products and from an analysis of production of specific unit length linear molecules. The same pattern of preferential cleavage is also found when linear, nicked circular, or relaxed closed circular forms of the same plasmid DNa are used as substrates for PstI. Inspection of the nucleotide sequences immediately adjoining each of the PstI sites suggests that the presence of adjacent runs of G-C base pairs confers significant resistance to cleavage.

Base Sequence↗
PubMed1981

An outbreak of Pseudomonas mastitis in dairy cows.

An outbreak of mastitis in a dairy herd is described in which the causative organism was Pseudomonas aeruginosa. Cases occurred either in dry cows or in animals which had very recently calved. The fact that all four quarters were involved is a very strong indication that the bacteria had been introduced in the dry cow therapy.

Animals↗