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Biomedical subjects

M Lydon

Publications and source records attributed to M Lydon.

15 recordsLinked to original sources
PubMed1999

Infradiaphragmatic central venous pressures reflect supradiaphragmatic pressures in stable burn patients.

OBJECTIVE: Because the skin of the groin is often spared, femoral central venous catheters are sometimes used in patients with extensive burns. The accuracy of central venous pressures obtained from the infradiaphragmatic location relative to the traditional supradiaphragmatic value is not known in this population. METHODS: Seventeen seriously injured but hemodynamically stable burn patients were enrolled in a protocol approved by the human studies committee in which, during scheduled central venous line rotations, supradiaphragmatic and infradiaphragmatic central venous pressures were determined simultaneously. RESULTS: These 17 patients were an average of 21.8+/-20.1 years old (range, 6 months to 61 years), and the average burn size was 60.8+/-22.6% (range, 20 to 90%). Supradiaphragmatic and infradiaphragmatic pressures correlated well, with an r value of 0.903, p less than 0.01. CONCLUSION: In the absence of clinically significant abdominal distention, infradiaphragmatic central venous pressure is an accurate reflection of supradiaphragmatic pressure, and indirectly, circulating blood volume.

Adolescent↗
PubMed1993

Acoustic analysis of infantile stridor: a review.

The review compares five methods that utilise electronic/computer acoustic processing techniques for the analysis of infantile stridor sounds. The first method uses traditional spectrographic techniques to produce time/frequency/intensity three-dimensional representation of the waveform. The second method is computer-based and uses the fast Fourier transformation (FFT) to show the frequency composition of the waveform. The third uses linear prediction coefficients (LPCs) to produce a power spectrum and inverse filtering to estimate the cross-sectional area of the human upper airway. The fourth technique employs a proprietary digital filterbank to analyse normal infant vocalisations, which may be used as a control by subsequent researchers. In the fifth method, a physiologically based digital filterbank, designed to closely model the human ear response, is proposed. It is envisaged that this approach will offer the flexibility of all the previous techniques and also closely model the analysis procedure carried out using subjective auscultation. It is concluded that none of the above techniques are sufficiently robust to provide unambiguous diagnosis of stridor type and that a reappraisal is required in terms of feature extraction so that relevant features can be identified. To this end, the authors propose that a physiologically based model of the human airway, including the vocal cords, be developed as an aid to the assessment of acoustic features.

Acoustics↗
PubMedDate not supplied

Evaporative water losses through a temporary wound dressing under simulated wound conditions.

Patients with burns lose large amounts of water through evaporation from open wounds. Because the wound covering is the first line of defense for maintenance of body fluid balance in these patients, quantification of the evaporative water loss through wound coverings at the bedside would improve the accuracy of estimations of body water loss. The present experiment evaluates the use of a small ventilated capsule system automated with miniature resistance-type dew-point sensors for measurement of evaporative water loss through biologic dressings under simulated wound conditions. Evaporative water loss from wounds was simulated by pilocarpine-induced profuse sweating on the forearm. Evaporative water loss through uncovered skin was compared with that of skin covered with commercially available temporary wound dressings. Compared with an adjacent unstimulated area, forearm dew-point temperature in the capsule (Tcdp) and sweat rate increased immediately after pilocarpine exposure and remained significantly elevated and relatively constant for an additional 60 minutes. Evaporative water loss of the forearm was 29 +/- 4.8 gm/m2/hr (mean +/- SE) at baseline and rose significantly to 275 +/- 18.2 gm/m2/hr after pilocarpine exposure. The pilocarpine-stimulated sweat rate and Tcdp at neutral conditions were similar to those obtained from walking on a treadmill for 60 minutes in a 30 degrees C room. Compared with pilocarpine-induced evaporative water loss of the uncovered skin, temporary wound dressings significantly reduced evaporative water loss by 40% to 60%. No significant differences were observed between varieties of temporary wound dressings differing in thickness and/or porosity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Once-daily wound cleansing and dressing change: efficacy and cost.

Children requiring inpatient burn care generally undergo wound cleansing and dressing change twice daily. Each dressing change is associated with significant pain and expense. We explored the efficacy of once- versus twice-daily dressing changes in children with burns of 30% or less of the body surface in a Human Studies Committee approved, prospective, open-label protocol. Fifty children with an average age of 4.4 +/- 4.7 years (range 1 month to 16 years) and an average burn size of 11.2% +/- 8.1% of the body surface (range 1% to 45%) treated with once-daily wound cleansing and dressing change were compared with a matched control group treated twice daily. We noted a significant saving of nursing staff time and a decreased need for pain medication with no change in infectious morbidity, length of stay, or the need for surgery. The patients, parents, and nursing staff were very enthusiastic about the efficacy of the once-daily regimen. This will now become the standard method of managing wounds of this size. We plan to expand the study to burns of 30% to 60%.

Adolescent↗
PubMedDate not supplied

Ultrasonic imaging as an adjunct to femoral venous catheterization in children.

Central venous catheterization is critically important to the management of burned children, but major morbidity is associated with the technical misadventures that can occur when inserting these devices. We used a bedside ultrasound device to facilitate placement of femoral venous catheters in eight edematous children with an average age of 7.0 years, weight of 23 kg, and burn size of 54%. To our knowledge, this is the first report of this technique in children. All children had central venous catheters placed in the femoral position requiring an average of 2 (range, 1 to 4) venepuncture attempts. There were no mechanical complications. We found the needle guide too cumbersome for our small patients, but found that the ability to mark the anatomy with a pen facilitated accurate catheter placement. In most patients, standard external anatomic landmarks are adequate for accurate catheter placement, however, in this initial experience, we found bedside ultrasound imaging to be a useful adjunct in selected patients with massive soft tissue edema.

Adolescent↗
PubMedDate not supplied

Tunable dye laser neovessel ablation as an adjunct to the management of hypertrophic scarring in burned children: pilot trial to establish safety.

Hypertrophic scarring is a major source of morbidity in patients with burns. The physiologic characteristics are poorly understood, but increased neovascularity is typically seen in those wounds destined to become hypertrophic. We theorize that ablation of the developing neovasculature may favorably influence the development of the hypertrophic scar. The goal of this pilot trial was to establish the practicality and safety of tunable dye laser neovessel ablation at 585 nm. Ten sites of evolving hypertrophic scar in nine children were treated with a series of 450 msec 6.75 J/cm2 pulses at 585 nm. Although all children had the expected transient posttreatment purpura, no pain, ulceration, pruritus, or worsening of the lesions was seen. The technique appears safe and is worthy of continuing investigation. Investigations with higher fluences and multiple treatments are in progress.

Burns↗
PubMedDate not supplied

Treatment of the seriously burned infant.

Infants (younger than 12 months) with large (more than 30%) burns are reported to have poorer chances for survival than older children with similar injuries. However, recent experience with such infants has been positive, prompting a 5-year review of management techniques. The injuries were approached in an organized fashion that included precise fluid support, excision, and biologic closure of full-thickness wounds within 5 days, limited exposure to high inflating pressures (more than 40 cm H2O), weekly replacement of central venous catheters, and intensive nutritional support via the enteral route whenever possible. Twelve such infants were treated during the 5-year interval. Their average age was 7.8 months (range, 1 to 12 month[s]), average weight was 8.8 kg (range, 4.3 to 13 kg), and average burn size was 42% (range, 30% to 90%). Inhalation injury was present in two of the children, and one child aspirated hot liquid. Six (50%) of the infants required the support of a mechanical ventilator for an average of 11.6 days (range, 4 to 18 days). Eight children required an average of 5.7 operations (range, 1 to 18 operation[s]), seven required central venous catheters, and five required arterial cannulae. Major infectious complications were seen in four children. Complications included pneumonia (two), catheter sepsis (two), peritonitis from a perforated ulcer (one), and wound sepsis (two). Six children required parenteral nutritional support for an average of 15 days (range, 5 to 36 days), and six children required enteral tube feedings for an average of 23 days (range, 9 to 55 days). Anabolic agents were not used. Discharge weights averaged 8.6 kg (range, 4.9 to 10.5 kg). The average ratio of the children's discharge to admission weight was 101% (range, 73% to 120%). All children survived and were discharged home. We conclude that these difficult injuries can be approached successfully with a strategy that emphasizes precise fluid repletion; early excision and biologic closure of wounds; avoidance of ventilator-induced lung injury; and intensive nutritional support.

Anti-Bacterial Agents↗
PubMedDate not supplied

Acellular allodermis in burns surgery: 1-year results of a pilot trial.

We grafted 10 sites on 6 children with limited (< 25%) areas of body surface available for donor harvest with an acellular allogenic dermis and a thin autograft. Matched control sites were grafted with autograft alone. Study site autografts (0.0074 +/- 0.0007 in, median 0.006 in, range 0.006 to 0.012 in) were thinner than control site autografts (0.0102 +/- 0.0008 in, median 0.012 in, range 0.006 to 0.013 in), with a P value of .015. Endopoints were initial engraftment (in percent) as judged by a blinded experienced observer and Vancouver scar scores. The 6 children (3 girls and 3 boys) had an average age of 5.2 +/- 0.9 years (range 2.8 to 10 years) and an average burn size of 68.7% +/- 6.7% total body surface area (range 47% to 85% total body surface area). The 10 study and control sites were treated with 10 separate procedures; 9 of the procedures were reconstructive and 1 was performed for the excision of an acute burn. Successful initial epithelialization was noted at 7 days postburn for 83% +/- 3.4% (range 60% to 95%) at the cryopreserved acellular human dermis sites and 83.3% +/- 4.3% (range 60% to 98%) at the control sites (not significant, P = .96). At a mean follow-up interval of 43.7 +/- 3.6 weeks (median 52, range 26 to 52 weeks), the differences between the study and control sites in the total mean (pigmentation, vascularity, pliability, and height) of the patients' Vancouver scar scores were not different.

Burns↗
PubMedDate not supplied

Early burn center transfer shortens the length of hospitalization and reduces complications in children with serious burn injuries.

Prompt transfer of the child with acute burns can be difficult from distant or inaccessible locations, and it is believed that the outcomes of children with serious burns whose transfer to a specialized burn care facility is delayed may be compromised. A 4-year experience with 16 consecutive children with serious burns (> or =20% of the body surface area) whose transfer to a burn care facility was delayed for 5 or more days was reviewed to document the difficulties that can follow such delays. These 16 children had an average age of 8.6+/-1.6 years and an average wound size of 57.6%+/-5.8% of the body surface area, and they arrived a mean of 16.3+/-3.4 days after the injury (range, 5 to 44 days). These children had undergone an average of 1 operation, excluding escharotomies, at referring facilities. Only 4 (25%) of the children had no infectious focus at transfer, and at admission resistant bacteria were recovered from 9 (56%) of the children and fungal organisms were found in 10 (63%). Compared with a concurrently managed matched control group of patients admitted to the burn center within 24 hours of injury, the delayed-transfer group had statistically significantly more bacteremia, renal dysfunction, wound sepsis, and central venous catheter days. It was also more expensive to manage these children; the delayed-transfer group required statistically significantly longer to achieve 95% wound closure, and they had greater total lengths of hospital stay and more rehabilitation days. The early transfer of children with serious burns to a specialized burn center may truncate hospitalization and thereby reduce costs.

Body Surface Area↗
PubMedDate not supplied

Initial experience with a prototype staple detector.

Stainless steel staples can be overgrown by granulation tissue or skin grafts and become buried in tissue. Although they are generally asymptomatic, they can on rare occasion erode to the surface or complicate the radiographic evaluation of pain not related to the staples. A device to facilitate detection of retained staples would be desirable, but it has been difficult to develop because stainless steel staples have poor magnetic and conductive properties. A prototype device, based on the presence of metal disturbing a low-power electromagnetic field, was developed. With human studies committee approval, this miniaturized detector was used in 13 burn patients to detect staples during planned removal of large numbers of staples. Staples were first removed using visual inspection and palpation of the wounds. This was followed by use of the staple detector. The age of the patients was 10.8 +/- 3.3 years, and burn size was 54.6 +/- 8.8% of the body surface. In 8 (62%) of the patients one or more additional staples were detected by the device that would otherwise have been overlooked. In 4 (31%) of the patients there was a false-positive signal, possibly related to topical silver in the wounds, that required additional focused physical examination. A portable staple detector has been developed. Initial experience with the device is favorable and warrants an expanded trial, which is in the planning stages.

Adolescent↗