Active glottal closure during anoxic gasping in lambs.

The present study was aimed at assessing laryngeal dynamics and their consequences during anoxic gasping in ketamine-sedated lambs. We first verified that the glottis was closed between gasps during anoxic gasping in seven chronically instrumented lambs, aged 11-15 days. Recording of glottal constrictor muscle electrical activity, subglottal pressure and lung volume, together with endoscopic observation, confirmed the presence of active glottal closure with maintenance of a high lung volume between gasps. Secondly, we tested whether maintenance of a high lung volume between gasps improved autoresuscitation efficiency. Six sedated lambs aged 8-11 days underwent two anoxic runs, including one with an open tracheostomy to prevent maintenance of a high lung volume. Access back to air was allowed for gasping. No significant difference was found in time to eupnea resumption, hemodynamic parameters or arterial blood gases. We conclude that a high lung volume is actively maintained by glottal closure between anoxic gasps in sedated lambs. Further studies are however needed to define the importance of laryngeal dynamics during gasping.

Microvascular anastomosis using histoacryl glue and an intravascular soluble stent.

OBJECTIVE: The purpose of this study was to assess a new technique for microvascular anastomosis on small arteries using Histoacryl glue and an intravascular soluble stent. METHODS: Sprague-Dawley rats were randomly assigned to either of two experimental groups or one control group. The first author (DL, a postgraduate year 4 resident) performed 12 end-to-end anastomoses on rat carotid arteries (1-mm vessel) (group A) using the experimental technique with Histoacryl glue and an intravascular stent. Thirteen microsuture carotid anastomoses performed by the senior author (DD), an experienced microsurgeon, served as control (group C). Permeability was assessed at 1 week for half of the animals and at 6 weeks for the others. Pathologic examination was done on both groups. To evaluate the influence of vessel size on the experimental technique, eight end-to-end anastomoses on rat abdominal aorta (2 mm) (group B) were also done by the first author. Permeability was assessed at 24 to 48 hours for this group. RESULT: In the experimental groups (A and B), two predictable failures (both in group A) were observed. Median anastomosis times were 11 minutes and 7 minutes, respectively. The control group had no failure and a median time of 17 minutes. Pathologic examination revealed more inflammation in group A than in group C. Coagulative necrosis of the arterial wall was observed exclusively in group A. CONCLUSION: This new technique is easy to learn and readily accessible to less experienced microsurgeons. The technique is fast and efficient. The calibre of the vessel has a great influence on ease and speed of the technique. However, histotoxicity of Histoacryl glue was observed. This technique can be valuable for free-tissue transfer in head and neck reconstruction. A less toxic glue would be useful.

Radiotelemetry system for apnea study in lambs.

Neonatal apneas are being studied in the laboratory using polysomnographic recordings in lambs. Standard equipment, requiring animal restraint, disrupts sleep and prevents development of spontaneous apneas. The aim of the current work was to develop and validate a wireless recording equipment to study freely moving lambs. Firstly, a radiotelemetry equipment composed of a multichannel FM transmitter and a receiver was developed. Secondly, to test the telemetry equipment, each biopotential - [electroencephalogram (EEG), electrooculogram (EOG), electrocardiogram (ECG), electromyograms (EMGs), nasal airflow] - was recorded simultaneously by standard equipment and by telemetry (5 lambs). The results indicated an excellent concordance between signals obtained by both systems. Finally, the 8-channel telemetry prototype was tested for polysomnographic recordings (16 lambs). Results obtained confirmed the possibility of recording frequent REM sleep periods and spontaneous apneas. In conclusion, this radiotelemetry polysomnographic equipment brings new possibilities for research on neonatal apneas.

Retropharyngeal abscesses: a clinical and radiologic correlation.

OBJECTIVE: This study evaluates the efficacy at our centre of the lateral neck x-ray and the computed tomography (CT) scan in differentiating retropharyngeal cellulitis from abscess in retropharyngeal space inflammatory process. METHOD: We reviewed the medical records of 37 patients with the diagnosis of retropharyngeal abscess or cellulitis hospitalized at the Centre Universitaire de Santé de l'Estrie in Sherbrooke between 1986 and 1997. Patients with a positive drainage at surgery were considered as retropharyngeal abscess and the rest as cellulitis. We measured the sensitivity, specificity, and positive and negative predictive values for the lateral neck x-ray and CT scan. Demographic and clinical data were also extracted for each patient. RESULTS: Twenty-five patients were classified as retropharyngeal cellulitis and only six patients as retropharyngeal abscess, although 13 patients went to the operating room for drainage. Results for the sensitivity and specificity were 80% and 100% for the lateral neck x-ray and 100% and 45% for the CT scan. Positive and negative predictive values for lateral neck x-ray were 100% and 94%, respectively. Forty percent and 100% were the values calculated for the CT scan. Clinical data were consistent with what has been reported in the literature. CONCLUSION: CT scan is helpful in the management of retropharyngeal abscess but has limits in differentiating cellulitis and abscess. Lateral neck x-ray was found to be very specific when the air sign was present.

Vagal afferents and active upper airway closure during pulmonary edema in lambs.

The present study was undertaken to gain further insight into the mechanisms responsible for the sustained active expiratory upper airway closure previously observed during high-permeability pulmonary edema in lambs. The experiments were conducted in nonsedated lambs, in which airflow and thyroarytenoid and inferior pharyngeal constrictor muscle electromyographic activity were recorded. We first studied the consequences of hemodynamic pulmonary edema (induced by impeding pulmonary venous return) on upper airway dynamics in five lambs; under this condition, a sustained expiratory upper airway closure consistently appeared. We then tested whether expiratory upper airway closure was related to vagal afferent activity from bronchopulmonary receptors. Five bivagotomized lambs underwent high-permeability pulmonary edema: no sustained expiratory upper airway closure was observed. Finally, we studied whether a sustained decrease in lung volume induced a sustained expiratory upper airway closure. Five lambs underwent a 250-ml pleural infusion: no sustained expiratory upper airway closure was observed. We conclude that 1) the sustained expiratory upper airway closure observed during pulmonary edema in nonsedated lambs is related to stimulation of vagal afferents by an increase in lung water and 2) a decrease in lung volume does not seem to be the causal factor.

Effects of capsaicin pretreatment on expiratory laryngeal closure during pulmonary edema in lambs.

The present study, performed in nonsedated, conscious lambs, consisted of two parts. In the first part, we 1) examined for the first time whether a respiratory response to pulmonary C-fiber stimulation could be elicited in nonsedated newborns and 2) determined whether this response could be abolished by capsaicin pretreatment. Then, by using capsaicin-desensitized lambs, we studied whether pulmonary C fibers were involved in the sustained, active expiratory upper airway closure previously observed during pulmonary edema. Airflow and thyroarytenoid and inferior pharyngeal constrictor muscle electromyographic activities were recorded. In the first set of experiments, a 5-10 microg/kg capsaicin bolus intravenous injection in seven intact lambs consistently led to a typical pulmonary chemoreflex, showing that C fibers are functionally mature in newborn lambs. In the second series of experiments, eight lambs pretreated with 25-50 mg/kg subcutaneous capsaicin did not exhibit any respiratory response to 10-50 microg/kg intravenous capsaicin injection, implicating C fibers in the response. Finally, in the above capsaicin-desensitized lambs, we observed that halothane-induced high-permeability pulmonary edema did not cause the typical response of sustained expiratory upper airway closure seen in the intact lamb. We conclude that functionally mature C fibers are present and responsible for a pulmonary chemoreflex in response to capsaicin intravenous injection in nonsedated lambs. Capsaicin pretreatment abolishes this reflex. Furthermore, the sustained expiratory upper airway closure observed during halothane-induced pulmonary edema in intact nonsedated lambs appears to be related to a reflex involving stimulation of pulmonary C fibers.

Complete glottic closure during central apnea in lambs.

OBJECTIVE: The objectives of this study were threefold: to document complete glottic closure during artificially induced central apnea in lambs; to unequivocally confirm that thyroarytenoid muscle electrical activity during central apneas in lambs reflects complete glottic closure; and to evaluate the physiologic significance of this phenomenon in artificially induced central apneas in lambs. METHODS: We recorded thyroarytenoid (TA) muscle EMG, subglottic pressure, and lung volume simultaneously with direct endoscopic vision of the glottis from beneath on nine 11- to 15-day-old lambs during artificially induced central apneas. RESULTS: Thirty-eight central apneas were induced. Complete glottic closure was present on 35/38 (92%) of these apneas. Complete glottic closure was always paralleled by thyroarytenoid muscle electromyogram (EMG) activity (35/38). In no instance was TA EMG recorded without complete glottic closure. Moreover, positive subglottic pressure and maintenance of lung volume above functional residual capacity were observed in 27/30 (90%) and 18/19 (95%), respectively, of these apneas where complete glottic closure was present. CONCLUSIONS: Complete glottic closure is present throughout most artificially induced central apneas in lambs. Complete glottic closure is paralleled by TA EMG in artificially induced central apneas. Thyroarytenoid muscle electromyographic activity is a reliable way to document complete glottic closure during apneas, especially in the presence of positive subglottic pressure. These observations suggest that complete glottic closure could be a physiologic mechanism aimed at maintaining higher lung volumes to improve gas exchange during central apneas.

[Ameloblastic carcinoma. Apropos of a case]. / Carcinome améloblastique. A propos d'un cas.

Ameloblastic carcinoma is an exceptionally rare odontogenic tumor. Ameloblastoma is considered malignant if there is evidence of metastasis or histological features of malignancy. Present classification of these tumors is debated. Several authors use the term malignant ameloblastoma for tumours that metastasize despite "benign" histological features whereas ameloblastic carcinoma is referred to as a tumor with malignant histological features regardless of its metastatic potential. We report a case of mandibular ameloblastic carcinoma with cervical lymph node metastasis in a 70-year-old man, documented by MRI and CT. We discuss current knowledge on these tumors.

Coordination between glottic adductor muscle and diaphragm EMG activity in fetal lambs in utero.

It has previously been reported that active glottic adduction is present during prolonged apneas but absent during periods of breathing movements in fetal lambs in utero. The present study was aimed at examining the precise coordination between fetal breathing movements [diaphragm electromyographic (EMG) activity (Di EMG)] and glottic adduction [thyroarytenoid muscle EMG activity (TA EMG)]. Electrodes for electroencephalogram, eye movements, TA EMG, and Di EMG and an arterial catheter were surgically implanted in fetal lambs 123-142 days postconception. Polygraphic recordings were performed without sedation while the ewe breathed room air (n = 11) or various gas mixtures (hypoxia, n = 5; hyperoxia, n = 4; hypercapnia, n = 5; hypercapnia+hyperoxia, n = 5). Tonic TA EMG was observed throughout >90% of apneas (>6 s) in both non-rapid-eye-movement and rapid-eye-movement sleep, and when Di EMG frequency decreased in rapid-eye-movement sleep. In all but two fetuses, TA EMG was immediately inhibited when Di EMG appeared. Altering blood gases did not modify these results. In conclusion, Di EMG and TA EMG are well coordinated in late gestation in fetal lambs, except in a few cases. These findings may have consequences for understanding the pathogenesis of mixed/obstructive apneas of prematurity.

[Intra-parotid neurogenic tumors of the facial nerve. Value of MRI]. / Tumeurs neurogènes intraparotidiennes du nerf facial. Intérêt de l'IRM.

Facial nerve intraparotid neuromas are rare. We report two cases with no facial paralysis. In the first case, the clinical protocol for the evaluation of a parotid mass did not suggest the intramastoid tumor extension. This extension was shown by CT and MRI and confirmed by gross and microscopic appearance. In the second case, no intrapretrous extension was observed with MRI. The diagnosis of neuroma was made during surgery. With a literature review, we discuss the diagnostic difficulties encountered in the investigation of parotid facial nerve tumors, emphasizing on the usefulness of CT and MRI in its diagnosis.

How I do it: Zenker's stapler diverticulectomy.

Zenker's diverticulum is an outpouching of the hypopharyngeal mucosa through Killian's area, a dehiscent or weak area between the cricopharyngeus muscle and the inferior constrictor muscle. Although this entity was described more than a century ago, these pulsion diverticuli continue to challenge surgeons to this day. The authors would like to reintroduce a method of resection that has proved useful in our practice.

Role of xanthine oxidase in reperfusion injury of ischemic skeletal muscles in the pig and human.

We investigated whether xanthine oxidase (XO) is a major source of oxygen-derived free radicals (oxy-radicals) in the pig and human skeletal muscles. It was observed that xanthine dehydrogenase and XO activities in nonischemic pig latissimus dorsi (LD) and gracilis muscles and human LD and rectus abdominis (RA) muscles were < 0.5 mU/g wet wt. The pig LD muscle hypoxanthine content increased significantly from 0.33 +/- 0.02 to 2.33 +/- 0.44 mumol/g dry wt after 5 h of warm ischemia, but the muscle uric acid content remained unchanged up to 2 h of reperfusion. Similarly, the hypoxanthine content in the human LD and RA muscles increased from 0.33 +/- 0.03 to 0.84 +/- 0.23 mumol/g dry wt after 2.0-3.5 h of warm ischemia, and the muscle uric acid content remained unchanged at the end of 15-90 min of reperfusion. Furthermore, 5 days of allopurinol treatment (25 mg/kg iv twice daily) starting 2 days before ischemia or 3 days of oxypurinol treatment (25 mg/kg iv twice daily) starting 15 min before reperfusion did not attenuate the extent of skeletal muscle necrosis in pig LD muscles subjected to 5 h of ischemia and 48 h of reperfusion. However, deferoxamine treatment (250 mg/kg iv twice daily) starting before or after ischemia, as described above, significantly reduced the extent of pig LD muscle necrosis. Finally, at 2 and 48 h of reperfusion significantly higher muscle neutrophil contents were seen in ischemic than in nonischemic control pig LD muscles. Neutrophil depletion with mechlorethamine (0.75 mg/kg iv) significantly reduced the extent of necrosis in pig LD muscles. These observations indicate that XO is not a major source of oxy-radicals in ischemia/reperfusion injury in the pig gracilis and LD muscles and human RA and LD muscles.

[Vascular territory expansion: a surgical technique for augmenting survival of an animal model of a musculocutaneous flap]. / L'expansion du territoire vasculaire: une technique chirurgicale pour augmenter la survie d'un modèle animal de lambeau musculocutané.

Ischemia-induced flap failure remains a major concern for reconstructive surgeons. A porcine rectus abdominis musculocutaneous (TRAM) flap was designed and subsequently used to study our hypothesis of vascular territory expansion whereas the perfusion territory of a previously ligated vessel is taken over by the remaining vessel(s). Specifically, we observed that ligation of the superior epigastric (SE) vessels two weeks prior to raising the TRAM flap significantly (p less than 0.05) increased the length and area of the viable skin in the transverse skin paddles of the treatment flaps compared to the contralateral sham manipulated control flaps. This significant increase in skin viability was seen to be accompanied by a significant (p less than 0.05) increase in skin and muscle capillary blood flow in the treated flaps compared with the controls (n = 9). The mechanism of vascular territory expansion is unclear. We postulate that hypoxia resulting from the ligation of the SE vessels prior to the flap surgery may play a role in triggering the deep inferior epigastric (DIE) artery to take over some of the territory previously perfused by the SE artery.

Augmentation of transmidline skin perfusion and viability in transverse rectus abdominis myocutaneous (TRAM) flaps in the pig.

The aim of this experiment was to design a clinically relevant TRAM flap in the pig and to use this flap model to study the effectiveness of preoperative ligation of the dominant vascular pedicle in augmentation of muscle and skin capillary blood flow and skin viability in the TRAM flap. This TRAM flap model was based on the deep inferior epigastric vascular pedicle, with the center of the transverse skin paddle attached to the underlying rectus abdominis muscle at the superior end of the muscle and extending bilaterally from its attached muscle. The transverse skin paddle (8 x 30 cm) included a contralateral and ipsilateral random portion of skin. This flap model was based on the deep inferior epigastric rather than the superior epigastric vascular pedicle because the deep inferior epigastric vascular pedicle is the smaller of the two in the pig and augmentation of its blood supply by ligation of the dominant superior epigastric vascular pedicle resembles more closely the clinical situation. It was observed that ligation of the dominant superior epigastric vascular pedicle 14 days prior to raising the TRAM flap significantly (p less than 0.05; n = 5) increased the total muscle and skin capillary blood flow and skin viability in the transverse skin paddle compared with the sham-operated control (n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical augmentation of skin blood flow and viability in a pig musculocutaneous flap model.

A porcine rectus abdominis musculocutaneous (TRAM) flap model was designed and validated in nine pigs. This TRAM flap was based on the deep inferior epigastric (DIE) vessels with an 8 x 18 cm transverse skin paddle at the superior end of the rectus abdominis muscle. The model was subsequently used to test our hypothesis of surgical augmentation of flap viability by vascular territory expansion. Specifically, we observed that ligation of the superior epigastric (SE) vessels at 4, 7, 14, and 28 days (N = 6 to 8) prior to raising the TRAM flaps significantly increased (p less than 0.05) the length and area of the viable skin in the transverse skin paddles of the treatment flaps compared with the contralateral shammanipulated control flaps. This significant increase in skin viability was seen to be accompanied by a significant increase (p less than 0.05) in skin and muscle capillary blood flow in the treatment TRAM flaps compared with the controls (N = 9). The mechanism of vascular territory expansion is unclear. We postulate that hypoxia resulting from the ligation of the superior epigastric vessels prior to the flap surgery may play a role in the triggering of the deep inferior epigastric artery to take over some of the territory previously perfused by the superior epigastric artery. This would then increase the skin and muscle capillary blood flow in the transverse paddle when the TRAM flap was raised on the deep inferior epigastric vascular pedicle.