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Biomedical subjects

T A Thomas

Publications and source records attributed to T A Thomas.

At least 19 recordsLinked to original sources
PubMed2000

Randomized study of intravenous fluid preload before epidural analgesia during labour.

We performed a randomized controlled trial of the effect of intravenous fluid preload on maternal hypotension and fetal heart rate (FHR) changes in labour after the first epidural injection. Group 1 (49 women) received 1 litre of crystalloid preload. Group 2 (46 women) received no preload. No statistically significant difference was shown between the two groups for either of the outcomes. Hypotension was found in three women in group 1 and five in group 2 (P = 0.4). Deterioration in FHR pattern was found in four women in group 1 and 11 in group 2 (P = 0.08). This study has not shown a significant increase in the incidence of hypotension when intravenous preload is omitted before epidural analgesia using a low concentration of bupivacaine during labour. Because of the clinical importance of the difference in the rate of FHR deterioration between the two groups, we continue to administer preload for high-risk cases.

Analgesia, Epidural↗
PubMed2000

Schemes for the identification of tissue types and boundaries at the tool point for surgical needles.

Precise control of automated invasive surgical tools requires real-time identification of tissue types and their deformation. At the focus of this paper is the epidural puncture, for which it is shown that the tissue type and deformation can respectively be determined from laser-based spectroscopy and the change in force required to push the needle through the various tissues. Studies have shown that physiological variations from one patient to another are too great to allow absolute values to be reliably used to indicate the position of the needle tip. However, the pattern of force variation during penetration is shown to be similar between specimens. Interpretation of this information in conjunction with spectroscopic techniques can be used to discriminate between tissues and tissue structure at the needle tip. This paper describes results from an investigation on automatic techniques for interpreting the type and deformation of tissues under tool action.

Adipose Tissue↗
PubMed2000

An alternative technique for creating the gastrojejunostomy in laparoscopic Roux-en-Y gastric bypass: experience with 28 consecutive patients.

BACKGROUND: This study illustrates our experience in laparoscopic Roux-en-Y gastric bypass (LRYGBP) using a new technique for creating the gastro-jejunostomy. METHODS: Between April and November 1999, 28 patients underwent LRYGBP. In the first 10 patients the transoral route with endoscopic guidance was utilized for placement of the anvil in the gastric pouch. A new totally intra-peritoneal approach was utilized in the next 18 patients, avoiding the trans-oral route. RESULTS: There were 23 women and 5 men with an average age of 36 years (range 24-51). The mean BMI was 47, with range 41-64. Of the patients, 82% had one or more associated co-morbid conditions (hypertension, diabetes, sleep apnea, arthritis). Average operative time in the first 10 patients using the trans-oral route with endoscopic guidance was 340 minutes (range 240-390 min). The next 18 patients underwent totally intra-peritoneal anvil placement with a 240-minute average operating time (range 150-310 min). There were no open conversions or mortalities. There were 4 complications, including 2 wound infections, one urinary tract infection, and one intra-abdominal abscess. The two wound infections occurred in the first 10 patients that underwent trans-oral introduction of the anvil. CONCLUSIONS: LRYGBP was a safe and feasible operation. We believe that our technique is easily reproducible, avoiding the trans-oral route for introducing the anvil. This technique may also decrease operative time and possibly the incidence of wound infections, although we are still in the learning curve and final conclusions cannot be made.

Adult↗
PubMed1999

A novel genotype encoding a single amino acid insertion and five other substitutions between residues 64 and 74 of the HIV-1 reverse transcriptase confers high-level cross-resistance to nucleoside reverse transcriptase inhibitors. Abacavir CNA2007 International Study Group.

We investigated HIV-1 reverse transcriptase (RT) polymorphisms of plasma isolates from 98 HIV-1-infected study subjects with >2 years of antiretroviral therapy who were failing their current protease inhibitor (PI)-containing regimen. In 1 patient, we detected a virus with a heavily mutated beta3-beta4 connecting loop of the HIV-1 RT fingers subdomain, consisting of a single aspartate codon insertion between positions 69 and 70 and five additional variations: 64N, K65, K66, 67G, 68Y, T69, Ins D, 70R, W71, R72, K73, 74I. Mutants with the recently described 2-aa insertions between codons 68 and 70 of RT were detected in another 3 patients. Among the four isolates with the 1- or 2-aa insertions, the novel genotype was the most refractory to therapy and displayed the highest level of phenotypic resistance to nucleoside reverse transcriptase inhibitors (NRTIs). Follow-up samples demonstrated that the novel mutant represents a stable genetic rearrangement and that the amino acid insertions can coexist with nonnucleoside analogue reverse transcriptase inhibitors (NNRTI) mutations resulting in phenotypic resistance to both NRTIs and NNRTIs. An increasing number of HIV-1 isolates containing various insertions in the beta3-beta4 hairpin of the HIV-1 RT fingers subdomain appear to emerge after prolonged therapy with different NRTIs, and these polymorphisms can confer multiple drug resistance against NRTIs.

Amino Acid Substitution↗
PubMed1999

An analysis of limb-threatening lower extremity wound complications after 1090 consecutive coronary artery bypass procedures.

The objective of this study was to examine and characterize limb-threatening lower extremity wound or soft tissue complications after coronary artery bypass (CABG) and determine risk factors for their cause. While minor wound problems of the leg after CABG are not uncommon, serious limb-threatening complications, though less frequent, do occur and are often de-emphasized in the surgical literature. A review of 1090 consecutive CABG procedures performed from January 1, 1995 through December 31, 1995 was instituted, which screened for limb-threatening lower extremity wound or soft tissue complications defined as wounds that: required additional surgery for treatment; prolonged the length of stay; or which required lengthy home health nursing for treatment. Minor lymph leaks, leg swelling, infections or wound problems treated as an outpatient were excluded. Of 1090 patients, 54 (5.0%) experienced a limb-threatening lower extremity complication. Complications were categorized as vein harvest incision non-healing (n = 36, 66.7%), decubitus ulceration (n = 11, 20.4%), forefoot ischemia/embolization (n = 10, 18.5%), groin hematoma/abscess (n = 6, 11.1%), severe cellulitis (n = 3, 5.6%), or a combination (n = 12, 22.2%). Statistically significant risk factors by univariate and bivariate analysis for a complication included older age (68 years vs 62 years, p = 0.007), female sex (57% vs 28%, p < 0.001), diabetes (57% vs 33%, p = 0.005) and longer pump time (129 min vs 114 min, p = 0.009). These complications necessitated five major lower extremity amputations and nine revascularization procedures. Chronic lower extremity ischemia from peripheral vascular disease (PVD) was a major contributing factor for the development of wounds in at least 23 (42.6%) of these patients, though suspected in only 10 (43.5%) preoperatively. A non-healing vein harvest incision below the knee of a patient retrospectively found to have inadequate distal circulation for healing occurred in 17 (31.5%) of the total 54 cases. It was concluded that non-healing vein incisions, decubitus ulcers and forefoot ischemic lesions frequently occurring in older diabetic females with undetected pre-existing PVD, comprise the majority of limb-threatening leg complications after CABG. Nearly one-third of the complications may have been avoided had the vein harvest incision not been made at the ankle of a patient with unappreciated PVD.

Age Distribution↗
PubMed1999

The Abuela Project: safe cheese workshops to reduce the incidence of Salmonella typhimurium from consumption of raw-milk fresh cheese.

OBJECTIVES: A multiagency intervention was implemented in Yakima County, Wash, to reduce the incidence of Salmonella serotype Typhimurium infections resulting from eating queso fresco (fresh cheese) made from raw milk, a traditional food in the Hispanic diet. METHODS: A pasteurized-milk queso fresco recipe with taste and texture acceptable to the Hispanic community was developed. Trained Hispanic volunteers conducted safe cheese workshops, which were attended by more than 225 persons. RESULTS: Workshop participants' acceptance of the new recipe was excellent and positive behavior changes were maintained over 6 months. CONCLUSIONS: Educational interventions in Hispanic communities can reduce the incidence of Salmonella Typhimurium associated with eating queso fresco.

Adolescent↗
PubMed1997

The influence of timing of ketorolac administration on post-operative analgesic requirements following total abdominal hysterectomy.

One hundred and thirty-seven patients were studied to assess whether the timing of a dose of ketorolac affected cumulative morphine requirements during the first 12 post-operative hours. Pain, sedation and nausea scores, respiratory rate and degree of operative blood loss were also recorded. Thirty-six patients (group A) were given placebo injections pre- and intra-operatively. Thirty-one patients (group B) received placebo pre-operatively and ketorolac 30 mg intra-operatively. Thirty-six patients (group C) received ketorolac 10 mg pre-operatively and ketorolac 20 mg intra-operatively and thirty-four patients (group D) were given ketorolac 30 mg pre-operatively and placebo intra-operatively. Post-operative analgesia was with intravenous (i.v.) morphine administered using a patient controlled analgesia (PCA) device. Analysis of variance revealed a significant difference in morphine consumption at 1, 2, 4, 8 and 12 h postoperatively (P < 0.05) between group A (no ketorolac) and groups B, C and D (ketorolac). However, there were no significant differences between groups B, C and D during the study period. Thus, the timing of ketorolac administration made no difference to overall morphine consumption. Pain, nausea, sedation and respiratory rate scores were similar in all four groups. There was a significantly greater blood loss in patients receiving ketorolac (groups B, C and D) compared with those receiving placebo alone (group A).

Adult↗
PubMed1997

Simulation of resistance forces acting on surgical needles.

High precision in the manual control of needles and biopsy probes in medical treatment requires high skill and dexterity levels. In anaesthesia, force sensation is an important feedback mechanism, and the practitioner needs to refresh or develop skills to improve on the interpretation of needle progress towards the target site. This paper describes an experimental tactile force simulator for uniaxial needle action for which the force resisting progress of the needle is derived from measured data. As an example, the approach taken to develop the simulation of the insertion of epidural needles is described. Adaptation to other procedures would be possible by adopting new reference models based on appropriate measured force data.

Animals↗
PubMed1995

Epidural infusions of bupivacaine and diamorphine in labour.

Three different concentrations of bupivacaine, 0.125%, 0.062% and 0.031%, all with diamorphine 0.0025%, were given as an epidural infusion at 10 ml.h-1 to 63 mothers in labour. When the three infusions were compared, significant differences were found in maternal requirements for top-ups and the degree of motor block, but there were no differences in the pain scores. The reduced motor block was not associated with a reduction in the instrumental delivery rate.

Adult↗
PubMed1994

Overpressure isoflurane at caesarean section: a study of arterial isoflurane concentrations.

In this study we have measured arterial concentrations of isoflurane obtained during Caesarean section in two groups of patients. Patients in group 1 received 1% isoflurane throughout operation, whilst those in group 2 received 2% isoflurane for the first 5 min, 1.5% for the next 5 min and 0.8% thereafter. We found that arterial isoflurane concentrations were significantly greater in group 2 than in group 1 (ANOVA, P < 0.05). Isoflurane concentrations greater than 30 micrograms ml-1 were achieved rapidly in most patients in both groups, but there was a large scatter of results. The isoflurane concentration at which awareness or recall may occur is not known, but an "overpressure" technique as described for patients in group 2 may result in fewer patients being at risk of awareness.

Adolescent↗
PubMed1993

Comparison of automatic oscillometric arterial pressure measurement with conventional auscultatory measurement in the labour ward.

We have compared two non-invasive methods of arterial pressure (AP) measurement used in labour wards: an automatic oscillometric measurement obtained by Dinamap 1846, and a conventional auscultatory measurement obtained by midwives. A total of 369 AP measurements were recorded, involving 28 normotensive and hypertensive pregnant women during labour, with or without extradural analgesia. Compared with the midwife group, the Dinamap group had a greater systolic AP, by 2.7 mm Hg (P < 0.01) and smaller diastolic AP, by 9.8 mm Hg (P < 0.01). The correlations between the two methods were highly significant, but the limits of agreement were relatively wide for both systolic and diastolic AP measurements. We conclude that a clinically important difference exists in diastolic AP measurements. Dinamap diastolic AP must be corrected using a regression equation, or simply by adding 10 mm Hg, before being compared with the available normal and hypertensive AP values.

Adult↗
PubMed1993

Isoflurane in labour.

A comparison of the analgesic efficacy of Entonox (50% nitrous oxide in oxygen) and Entonox with 0.2% isoflurane was made in 18 consenting mothers during the first stage of labour. The inhalational gases were self-administered during contractions over a 3 h study period using a standard Entonox demand valve and breathing system. Isoflurane 0.2% was added from an Ohmeda Isotec drawover vaporizer and the inspired concentration of isoflurane was analysed continuously using a Datex Ultima analyser. Linear analogue scores for pain were significantly lower (p < 0.001) during the Entonox-isoflurane administration compared with Entonox alone. Drowsiness was not a clinical problem and there was a high acceptance rate for Entonox-isoflurane inhalational analgesia during labour.

Adolescent↗
PubMed1992

Spinal anaesthesia for caesarean section: comparison of 22-gauge and 25-gauge Whitacre needles with 26-gauge Quincke needles.

We have studied 150 women undergoing elective Caesarean section under spinal anaesthesia. They were allocated randomly to have a 22-gauge Whitacre, a 25-gauge Whitacre or a 26-gauge Quincke needle inserted into the lumbar subarachnoid space. The groups were compared for ease of insertion, number of attempted needle insertions before identification of cerebrospinal fluid, quality of subsequent analgesia and incidence of postoperative complications. There were differences between groups, but they did not reach statistical significance. Postdural puncture headache (PDPH) was experienced by one mother in the 22-gauge Whitacre group, none in the 25-gauge Whitacre group and five in the 26-gauge Quincke group. Five of the six PDPH occurred after a single successful needle insertion. Seven of the 15 mothers in whom more than two needle insertions were made experienced backache, compared with 12 of the 129 receiving two or less (P < 0.001). We conclude that the use of 22- and 25-gauge Whitacre needles in elective Caesarean section patients is associated with a low incidence of PDPH and that postoperative backache is more likely when more than two attempts are made to insert a spinal needle.

Adolescent↗
PubMed1991

Epidural infusion of diamorphine with bupivacaine in labour. A comparison with fentanyl and bupivacaine.

We have compared the analgesic effects of three epidural infusions in a randomised, double-blind study of 61 mothers in labour. An initial dose of bupivacaine 0.5% 8 ml was followed by either bupivacaine 0.125%, bupivacaine 0.125% with diamorphine 0.0025% or bupivacaine 0.125% with fentanyl 0.0002%. All infusions were run at a rate of 7.5 ml/hour. Analgesia was significantly better in both the groups receiving opioids. Diamorphine was shown to be the more effective supplement to bupivacaine. The 5% incidence of pruritus in the opioid groups was less than that reported by earlier authors.

Analgesia, Epidural↗