Changes in the cuff pressure in neonates in the absence of nitrous oxide.

BACKGROUND: Changes in the pressure of cuffed neonatal size tracheal tubes (TT) during anaesthesia without nitrous oxide are not well described. We determined whether the cuff pressure changes over time in neonates under general anaesthesia without nitrous oxide. METHODS: The airways of thirty neonates were secured with a high volume low pressure cuffed TT for meningocele surgery. The cuff was manually inflated until there was no audible leak and maintained at 10-15 cm H2O throughout by monitoring the pressure continuously with both a manometer and a pressure transducer. At baseline, the cuff pressure was assessed in the supine and then prone positions. During surgery, if the pressure exceeded 15 cm H2O, the cuff was deflated to < 15 cm H2O and if it was < 10 cm H2O, the cuff was inflated to 10-15 cm H2O. The time interval between corrections and the number of corrections were recorded. RESULTS: The cuff pressures in 18 neonates (60%) required correction during surgery. The cuff pressure exceeded 15 cm H2O in nine neonates (30%) and was corrected. The cuff pressures in 13 neonates were less than 10 cm H2O and required correction. The gender, weight, height, and duration of anaesthesia did not differ significantly between neonates who required correction of the cuff pressure and those who did not. Mean cuff pressures were similar at 15, 45, and 75 minutes of anaesthesia. CONCLUSIONS: In 60% of neonates undergoing surgery in the prone position under general anaesthesia without nitrous oxide, the cuff pressure exceeded 15 cm H2O. In such cases, cuff pressure should be monitored continuously throughout the surgery.

Glottic views using a Miller size 0 blade are superior to those from a Macintosh size 0 blade in neonates: a randomized trial.

INTRODUCTION: Both the Miller and Macintosh blades are commonly used during laryngoscopy in infants and children, although the glottic views have not been compared in neonates. This study compared the glottic views with the Miller and Macintosh size 0 blades in neonates when the blades were placed above and below the epiglottis. MATERIAL AND METHODS: Forty anaesthetized and paralyzed neonates undergoing elective surgery were enrolled and randomized to either the Miller or Macintosh size 0 blade. Two glottic views were obtained in random order in each neonate and were photographed using the same blade: lifting the epiglottis first then the tongue base or vice versa. The percentage of glottic opening (POGO) scores were evaluated with each view. The POGO scores and cardiorespiratory variables were then analysed. RESULTS: The POGO scores using the Miller blade to lift both the epiglottis and the tongue base were similar, whereas the scores using the Macintosh blade to lift the epiglottis were greater than those to lift the tongue base. The POGO scores using the Miller blade in both positions were significantly greater than those using the Macintosh blade in the corresponding positions (P = 0.0001). The heart rate using the Miller blade was greater than that using the Macintosh blade (P = 0.0001). CONCLUSIONS: In neonates, the glottic views using the Miller size 0 blade to lift both the epiglottis and the tongue base were deemed to be excellent and superior to those using the Macintosh blade in both positions.

Performance of first and second generation supraglottic airway devices in patients with simulated difficult airway: a randomised controlled trial.

BACKGROUND: Guidelines for management of unanticipated difficult intubation recommend the use of supraglottic airway devices (SADs) in cases of failed intubation. How-ever, there is a lack of comparative studies for different type of devices. In this randomised controlled trial, the performance of 1st and 2nd generation supraglottic airway devices was compared in patients with a simulated difficult airway. MATERIAL AND METHODS: We enrolled 90 patients, scheduled for elective surgery and suitable for supraglottic airway device insertion. Laryngeal mask airway (LMA)-classic (LMAC), LMA-proseal (LMAP) and LMA-flexible (LMAF) were evaluated. The modified Mallampati test was used for the preoperative airway assessment. Maximal mouth opening, body mass index, thyromental and sternomental distances, and neck circumference were measured, and patients with predicted difficulty were excluded. Insertion time, ease of insertion, oropharyngeal leak pressure, and Brimacombe and Berry Bronchoscopy Scores were evaluated. Peak airway pressure was measured at 1, 15 and 60 min following the insertion of SADs. Complications were recorded. RESULTS: Oropharyngeal leak pressures were 35.2 ± 8.1, 31.7 ± 7.7 and 31.3 ± 6.0 mm Hg for LMAP, LMAC and LMAF respectively (P = 0.079). First min peak airway pressure values were 14.0 ± 4.2, 15.0 ± 3.9, 14.9 ± 4.4 mm Hg respectively (P = 0.403). There was a significant positive correlation between oropharyngeal leak pressure and first min peak airway pressure (r = 0.264, P = 0.013). Mean number of attempts was 1.1 ± 0.3 times (P = 0.840). Insertion time was 20.0 ± 10.4, 17.0 ± 5.7 and 16.4 ± 10.2 s respectively (P = 0.440). Ease of insertion score was 2.0 ± 0.9, 2.1 ± 0.9 and 2.1 ± 1.3 respectively (P = 0.837). There was no significant difference for optimization manoeuvre requirement or fibreoptic scope grades (P = 0.265, P = 0.651, respectively). CONCLUSIONS: First and second generation of supraglottic airway devices provided similar clinical performance for patients with difficult airway and trauma due to limited cervical motion.

Brachiocephalic artery cannulation in proximal aortic surgery that requires circulatory arrest.

The brachiocephalic artery is an alternative cannulation site in the repair of ascending aortic lesions that require circulatory arrest. We evaluate the effectiveness and safety of this technique. Proximal aortic surgery was performed in 32 patients from 2006 through 2012 via brachiocephalic artery cannulation and circulatory arrest. Twenty-four (75%) of the patients were men. The mean age was 48.69 ± 9.43 years (range, 30-68 yr). Twelve had type I dissection, 2 had type II dissection, and 18 had true aneurysms of the ascending aorta. All operations were performed through a median sternotomy. The arterial cannula was inserted through an 8-mm vascular graft anastomosed to the brachiocephalic artery in an end-to-side fashion. In dissections, the distal anastomosis was performed without clamping the aorta. The patients were cooled to 24 °C, and circulatory arrest was established. The brachiocephalic and left carotid arteries were clamped, and antegrade cerebral perfusion was started at a rate of 10 mL/kg/min. Cardiopulmonary bypass was resumed after completion of the distal anastomosis and the initiation of rewarming. The proximal anastomosis was then performed. None of the patients sustained a major neurologic deficit, but 5 patients experienced transient postoperative agitation (<24 hr). There were 2 early deaths (6.25%), on the 3rd and the 11th postoperative days, both unrelated to the cannulation technique. Brachiocephalic artery cannulation through a graft can be a safe and effective technique in proximal aortic surgical procedures that require circulatory arrest.

Intravenous amitraz poisoning.

Amitraz, a derivative of dimethylformamidine, is an acariside and insecticide used to control parasites in animals. Amitraz inhibits monoamine oxidase and prostaglandin synthesis and is an alpha-2 adrenergic agonist. Xylene, a mixture of o-, m-, and p-dimethylbenzene, is widely used in industry. A 22-year-old woman was poisoned by an intravenous injection of 5-6 mL of an amitraz formulation (amitraz 12.5% + xylene 57.5%). Clinical findings were coma (Glasgow coma score 3), respiratory depression, hypotension, bradycardia, hematuria, and edema and hyperemia at the injection site. Although her coma and other symptoms quickly resolved, as has been seen in oral and dermal amitraz poisoning, intoxication with higher doses occurring from intravenous injection may result in more serious problems.

The role of K(+) channels on the inhibitor effect of sevoflurane in pregnant rat myometrium.

UNLABELLED: Volatile anesthetics and K(+) channel openers inhibit spontaneous contractions in myometrial smooth muscle. Volatile anesthetics modulate K(+) channel activity. We investigated the role of two K(+) channel blockers on the effect of sevoflurane in pregnant rat myometrium. Term pregnant rat uteri were excised, and cross-sectional myometrial strips were mounted for isometric force recording. Sevoflurane inhibited the amplitude and frequency of spontaneous myometrial contractions in a concentration-dependent manner. The maximal inhibition measured in amplitude and frequency of spontaneous myometrial contractions with sevoflurane (at 3 minimum alveolar anesthetic concentration) was 44.32% and 33.32% of control contractions, respectively. Tetraethylammonium (TEA) and glibenclamide, K(+) channel blockers, increased spontaneous myometrial contractions in a concentration-dependent manner. Sevoflurane responses were repeated at concentrations with no effect on spontaneous contractility of TEA, a Ca(2+)-activated K(+) channel blocker, and glibenclamide, an adenosine triphosphate-sensitive K(+) channel blocker, in myometrial strips. TEA (3.10(-4) M) caused a significant reduction in sevoflurane-induced inhibitor responses, but glibenclamide (10(-6) M) did not. Sevoflurane-induced maximal inhibition (at 3 minimum alveolar anesthetic concentration) on amplitude and frequency of spontaneous myometrial contractions in the presence of TEA (3.10(-4) M) was 31.85% and 22.33% of control contractions, respectively (P < 0.05). These results suggest that the in vitroapplication of sevoflurane inhibited the amplitude and frequency of spontaneous myometrial contractions in pregnant rats in a concentration-dependent manner. Such inhibition was reduced by TEA. The inhibition of myometrial smooth muscle induced by sevoflurane seems to be mediated, at least in part, via activation of Ca(2+)-activated K(+) channels, because inhibition was reduced by TEA. IMPLICATIONS: In this study, we found that sevoflurane causes significantly decreased myometrial contractile activity in pregnant rats. The inhibition of myometrial smooth muscle induced by sevoflurane seems to be mediated, at least in part, via activation of Ca(2+)-activated K(+) channels, because inhibition was reduced by tetraethylammonium.