High laryngeal mask airway pressures resulting from nitrous oxide do not increase pharyngeal mucosal injury in dogs

PURPOSE

During general anesthesia, nitrous oxide (N2O) diffuses rapidly into the air-filled laryngeal mask airway (LMA) cuff, increasing intracuff pressure. There is no clear correlation between LMA intracuff pressure and pressure on the pharynx. We have studied the effects of high LMA intracuff pressures secondary to N2O on the pharyngeal mucosa of dogs.

METHODS

Sixteen mongrel dogs were randomly allocated to two groups: G1 (intracuff volume, 30 mL; n=8) breathed a mixture of O2 (l L x min(-1)) and air (l L x min(-1)) and G2 (intracuff volume, 30 mL; n=8) a mixture of O2 (l L x min(-1)) and N2O (l L x min(-1)). Anesthesia was induced and maintained with pentobarbitone. LMA cuff pressure was measured at zero (control), 30, 60, 90 and 120 min after #4 LMA insertion. The dogs were sacrificed, and biopsy specimens from seven predetermined areas of the pharynx in contact with the LMA cuff were collected for light (LM) and scanning electron microscopic (SEM) examination by a blinded observer.

RESULTS

LMA intracuff pressure decreased with time in G1 (P <0.001) and increased in G2 (P <0.001). There was a significant difference between the groups (P <0.001). In both groups, the LM study showed a normal epithelium covering the pharyngeal mucosa and mild congestion in the subepithelial layer. There were no differences between the groups (P >0.10) or among the areas sampled (P >0.05). In both groups, the SEM study showed a normal pharyngeal mucosa with mild superficial desquamation. Few specimens in G1 and G2 showed more intense epithelial desquamation.

CONCLUSION

High LMA intracuff pressures produced by N2O do not increase pharyngeal mucosal injury in dogs.

Effect of high laryngeal mask airway intracuff pressure on the laryngopharyngeal mucosa of dogs

OBJECTIVES

To evaluate the effect of increased of laryngeal mask airway (LMA) intracuff pressures on the laryngopharyngeal mucosa.

STUDY DESIGN

Animal model.

METHODS

Sixteen mixed-breed dogs were randomly allocated to two groups, G1 (intracuff volume, 30 mL; n = 8) and G2 (intracuff volume, 54 mL; n = 8), to produce, respectively, high or very high intracuff pressures. Anesthesia was induced and maintained with pentobarbital. Intracuff pressures were measured immediately after insertion and inflation of a No. 4 laryngeal mask airway (LMA) and 30, 60, 90, and 120 minutes thereafter. The dogs were euthanized, and biopsy specimens from eight predetermined areas of the laryngopharynx in contact with LMA cuff were collected for light microscopic (LM) and scanning electron microscopic (SEM) examination.

RESULTS

Initial LMA cuff inflation in G1 and G2 resulted in intracuff pressures of 119 mm Hg +/- 4 mm Hg and 235 mm Hg +/- 13 mm Hg, respectively. Over a 2-hour period, the intracuff pressure decreased significantly in G1 (P < .001) and G2 (P < .01), and there was a significant difference between the groups over time (P < .001). The LM study of laryngopharyngeal mucosa in both groups showed mild congestion in the subepithelial layer. There were no differences between the groups (P > .10) or among the areas sampled (P > .10). In some areas of G2, the SEM study showed epithelial desquamation that was more intense than that in G1.

CONCLUSIONS

The increase in LMA intracuff pressure caused only mild alterations in the laryngopharyngeal mucosa of the dog.

Investigation into the use of the laryngeal mask airway in pentobarbital anesthetized dogs

OBJECTIVE

To investigate the use of the laryngeal mask airway (LMA) in dogs.

STUDY DESIGN

Prospective experimental study.

ANIMALS

Eight healthy adult mixed breed dogs weighing from 15 to 20 kg.

METHODS

The dogs were anesthetized with intravenous pentobarbital. An LMA was introduced after the induction of anesthesia and 1 L/min O2 plus 1 L/min air was delivered using a circle anesthetic system. Respiratory rate, tidal volume, arterial O2 saturation (pulse oximetry), end tidal CO2, inspired fraction of O2, pulse rate, and mean arterial blood pressure were measured after the insertion of the LMA and 30, 60, 90, and 120 minutes afterwards.

RESULTS

There were no changes in respiratory rate, tidal volume, arterial O2 saturation, and pulse rate during anesthesia. End tidal CO2 decreased significantly by the end of anesthesia and ventilation appeared satisfactory.

CONCLUSIONS

An LMA appeared to be an alternative option to maintain the patency of the airway in dogs.

CLINICAL RELEVANCE

This device may allow safe maintenance of an airway in dogs when intubation is difficult or when it interferes with the procedure (eg, cervical myelography).

Tracheobronchial consequences of the use of heat and moisture exchangers in dogs

PURPOSE

To determine the effect of heat and moisture exchange (HME) on the tracheobronchial tree (TBT) using a unidirectional anesthesic circuit with or without CO2 absorber and high or low fresh gas flow (FGF), in dogs.

METHODS

Thirty-two dogs were randomly allocated to four groups: G1 (n=8) valvular circuit without CO2 absorber and high FGF (5 L x min(-1)); G2 (n=8) as G1 with HME; G3 (n=8) circuit with CO2 absorber with a low FGF (1 L x min(-1)); G4 (n=8) as G3 with HME. Anesthesia was induced and maintained with pentobarbital. Tympanic temperature (TT), inhaled gas temperature (IGT), relative (RH) and absolute humidity (AH) of inhaled gas were measured at 15 (control), 60, 120 and 180 min of controlled ventilation. Dogs were euthanized and biopsies in the areas of TBT were performed by scanning electron microscopy.

RESULTS

The G2 and G4 groups showed the highest AH (>20 mgH2O x L(-1)) and G1 the lowest (< 10 mgH2O x L(-1)) and G3 was intermediate (< 20 mgH2O x L(-1)) (P < 0.01). There was no difference of TT and IGT among groups. Alterations of the mucociliary system were greatest in G1, least in G2 and G4, and intermediate in G3.

CONCLUSION

In dogs, introduction of HME to a unidirectional anesthetic circuit with/without CO2 absorber and high or low FGF preserved humidity of inspired gases. HME attenuated but did not prevent alterations of the mucociliary system of the TBT.

Histopathologic features and management of ameloblastoma: study of 20 cases

BACKGROUND

Odontogenic ameloblastoma (OA) of the jaws is a rare neoplasia of the oral cavity (0.78%) with a 5:1 mandible/maxilla relation, with the molar region and the ascendant ramus being the most affected areas. Comparing our results with the literature demonstrated to us that this tumor may be considered to be a worldwide problem due to the similarity in clinical findings among different ethnic groups

CASE SERIES

The purpose of this study of 20 patients with ameloblastoma of the mandible and maxilla diagnosed at the Stomatology and Head and Neck Services of Heliópolis Hospital, São Paulo, Brazil, from 1980 to 1997, was to establish the histopathologic pattern of classification of those tumors through optical microscopy and the relation of this histopathology to therapeutic management. Using the Regeze, Kerr and Courtney classification (1978), we diagnosed follicular tumor in 11 cases, plexiform in 6 cases and unicystic in 3 cases, and performed surgical resection with a safety margin of 1.5 to 3.0 cm in the follicular and plexiform cases and bone curettage in the unicystic cases.

Intercomparison of calibration procedures for 192Ir HDR sources in Brazil

The lack of well established dosimetry protocols for HDR sources is a point of great concern regarding the uniformity of procedures within a particular country and worldwide. The main objective of this paper is to report the results from ten institutions of an intercomparison of calibration procedures for 192Ir HDR sources currently in use in Brazil. The treatment irradiator of one institution was calibrated by a reference system and used by all participants with their own measuring electrometers and ionization chambers under the same experimental conditions. Two methods were used: the calibration jig and the well-type ionization chamber. Each participant was allowed to use their own method and formalism. The results of this exercise were very positive since this was the first time in Brazil that a group of users gathered to share their experience and openly discuss the physical concepts behind the calibration procedures. The results were all within +/-3.0%, except one case where -4.6% was observed and later identified as a problem with the Nk value for x-rays. Though the magnitude of the deviations found was generally acceptable considering the diversity of formalisms currently in use, a proposal is now being prepared to be adopted as a national protocol. The identification of the institutions was left out for the sake of confidentiality.

Actinomycosis and botryomycosis of the tonsil

This study was carried out in 165 patients submitted to the surgery of tonsils or adenoid from 1977 to 1989 at the Botucatu Medical School Hospital. The clinical signs and histopathological findings were reviewed. All patients exhibited similar complaints with recurrent tonsillitis, sore throat, dysphasia, high temperature, and enlarged tonsils. After surgery, the tonsils was submitted to histopathological study and showed "grains" in the crypts in 6 cases. Four cases (2.4%) of Actinomyces and two (1.2%) of Botryomyces were identified. Any clinical peculiarity was identified with the presence of these "grains."