Biomedical subjects
Publications and source records attributed to T M Davidson.
Different scar revision techniques are compared on similar scars, all on the same patient. Comparison of the final results is unique and interesting and provides insight into choosing the "optimal" technique for these procedures. Historical perspective is provided.
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A reptile caretaker was bitten and envenomated by Atractaspis bibronii while handling a box of "non-venomous" colubrid feeder snakes. The patient was bitten on a finger by a single fang. Pain and swelling were noted within 10 min and dissipated over the ensuing 3 days. This case report adds to the limited number of bites by A. bibronii already found in the literature and reviews what is currently known about the species.
Subjects in 2 experiments (ns = 72 and 50) learned a 16-item, 4-category word list and were then administered hypnotic suggestions to be amnesic for all the words in 1 of the categories. Even when selective amnesia was completely successful, subjects in both experiments revealed a high level of recall for words not targeted for amnesia; moreover, these words were recalled in a highly organized, category-by-category fashion. Evidently, attention to relevant retrieval (i.e., organizational) cues does not oblige recall of words targeted for amnesia. Forgetting in the presence of such powerful mnemonic cues seems to characterize hypnotic amnesia and some spontaneous forms of forgetting as well. We argue that mnemonic lapses of this kind represent a failed attempt to remember rather than a successful attempt to forget.
Parotid surgery often leaves a facial contour deformity. Free abdominal dermal-fat grafts were used to preserve the facial contour of nine patients undergoing parotid surgery. This procedure is simple to perform and provides an improved cosmetic result without significantly increasing operative time or lengthening hospitalization. No troublesome fat absorption occurred postoperatively. The dermal-fat graft also serves as a barrier to regenerating neurons, thereby preventing postoperative gustatory sweating.
Olfactory dysfunction is currently not listed among the NINCDS-ADRDA clinical criteria for the diagnosis of Alzheimer's disease. There is a large amount of psychophysical and neuropathologic evidence to suggest that patients with Alzheimer's type dementia have olfactory system abnormalities. The rhinologic status of this group has not been characterized. The authors examined 21 Alzheimer's patients and 21 age-matched controls to determine whether 1. the Alzheimer's group, in fact, had a diminished sense of smell, and whether 2. rhinologic factors were responsible for this nasal dysfunction. The findings support a neurologically mediated phenomenon as the cause for significant impairment in olfactory function in patients with probable Alzheimer's disease.
The relationship between functional residual capacity (FRC) and shunt development with halothane anesthesia in 18 nonobese surgical patients (age, 21-34 yr) was studied. FRC was measured by helium dilution, and intrapulmonary shunt was distinguished from ventilation-perfusion inequality by multiple tracer inert gas elimination analysis. Awake supine FRC was 34.6 +/- 6.6% (mean +/- SD) of total lung capacity (TLC), and closing capacity (CC) was 29.8 +/- 5.3% of TLC. Anesthesia, muscle paralysis, tracheal intubation, and mechanical ventilation produced an average 14.6 +/- 13.3% FRC reduction to an average anesthesia FRC 29.8% of TLC (P = 0.002). Shunt increased from 1.2% +/- 1.5% awake to 8.6 +/- 8.3% during anesthesia (P = 0.005). A nonlinear relationship was found between shunt and FRC/TLC so that anesthetized subjects with an FRC less than awake CC had an average 11.4 +/- 8.3% shunt, whereas subjects with an FRC greater than CC had a 2.4 +/- 2.8% shunt (P = 0.025). Nonsmokers developed shunt only if FRC was less than CC. Smokers showed a significantly higher shunt for a given (FRC-CC)/TLC compared to nonsmokers (P less than 0.001). The slope of the regression of shunt on BMI (body mass index = weight/height2) showed a significant increase during anesthesia (P = 0.005), and smokers had a significantly higher slope compared to nonsmokers (P = 0.001). These findings suggest a gravity-dependent mechanism for intrapulmonary shunting during anesthesia. Therefore, shunting was due to dependent regional lung volume reduction associated with an FRC decrease to less than closing capacity. The enhanced intrapulmonary shunting in smokers may have been related to the increased dependent regional residual volume associated with smoking.
Microscopically Oriented Histologic Surgery (MOHS) has been applied to primary epidermoid cancers of the mucosal tissues of the head and neck since 1979. In that time we have treated 170 patients and maintained excellent records, losing no patients to follow-up. One hundred three patients have been followed for 2 years. Of this group, only nine patients have developed local recurrences; three were salvaged, six were not. This presentation reviews the concept of MOHS and its application to head and neck mucosal lesions. The results are analyzed, and conclusions are drawn regarding what we have learned about the biologic behavior of head and neck tumors and the role of MOHS in treating these neoplasms.
Intravenous envenomation by North American rattlesnakes is an uncommon occurrence, but a true emergency. In three documented, successfully resuscitated cases, the mainstay of treatment was the immediate intravenous administration of antivenin.
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Lateral canthopexy using permanent suspending sutures to shorten the lateral canthal tendon helps prevent scleral show, increased sloping of the upper lid, and inferomedial displacement of the lateral canthus following lower lid blepharoplasty. While these complications usually are prevented by flap suspension techniques, in which more skin is excised above and lateral to the commissure than below it, sutures running from the inferomedial part of the lateral canthal tendon to its superolateral aspect and to periosteum just inside the orbit still further reduce the tendency toward the complications mentioned. We report technical aspects and results. After several years of clinical experience, we have the impression that the technique is a useful adjunct, even though it may produce more swelling and inflammation and a longer recuperative period.
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The management of snake bites once the patient reaches the hospital should be to obtain the necessary blood parameters (type and cross-matched blood, complete blood count, platelets, PT, PTT, fibrinogen and fibrin split products, electrolytes and calcium), to evaluate the fang marks and the neurovascular status of the involved extremity and to monitor systemic signs and symptoms. These steps are extensively described in the literature, and are commonly agreed upon. We then start intravenous antivenom, after appropriate skin testing for horse serum allergy, beginning with 4--5 vials (8--10 in children) over the initial 30--60 minutes and titrating to cessation of the progression of the toxic signs. Concomitantly, we measure intracompartmental and subcutaneous tissue pressure in all clinically suspected areas. If intracompartment pressures are less than 30 mm Hg, surgical intervention is not necessary; antivenom is continued as necessary and the wick catheter measurements are repeated if indicated. If pressures are greater than 30 mm Hg,immediate surgical decompression is advisable.
Nasal profiles are altered in almost every rhinoplasty operation. Often neglected in diagnosis and surgery are alterations in profiles of the cheeks and upper lip that should be made at the same time. We show aesthetic effects produced by alterations in these structures and describe how we measure and record the adjustment. A few examples of results are presented to indicate the techniques used and the importance of including changes in profiles of the cheeks and upper lip in cosmetic rhinoplastic diagnosis and treatment.
The rhomboid and other 60 degrees transposition flaps have theoretical and practical disadvantages for many applications. A better flap for these is one having an angulation of 30 degrees at its distal end. When this 30 degrees flap is combined with the M-plasty, a versatile and cosmetically favorable repair is provided for many surface defects. In fact, over the years, it has become our most useful method of closure with flaps. Fundamentally, it allows sharing of tensions of closure better than does the rhomboid flap, produces less level disparities or protrusions than does any 60 degrees flap, and its resulting scar length is only fractionally longer than that of the rhomboid flap. Rhomboid and other 60 degrees angle flaps have been exceedingly valuable tools to many surgeons; the 30 degrees flap combined with M-plasty should be significantly more useful.
Blepharoplasty on lower lids frequently results in a downward pull on the free border of the lid and inferomedially on the lateral canthus. Extending the incision in the lower lid upward and lateral to the outer canthus allows most of the excision to occur laterally. Closure then pulls superolaterally, which tends to prevent the commonest complications of blepharoplasty on lower lids.