Influence of acute hypoxia combined with nitrous oxide on cardiovascular variability in conscious hypertensive rats.

Anesthetics have been reported to depress autonomic nervous system (ANS) responses to hypoxia. The mechanisms by which cardiovascular variability responds to acute progressive hypoxia (APH) under nitrous oxide (N(2)O) inhalation, however, remain unclear. Additionally, the effect of hypertension on ANS responses in such cases has not been fully clarified. The present study examined the influence of APH (10% O(2)) under 60% N(2)O inhalation on cardiovascular variability in conscious, spontaneously hypertensive rats (SHR). Twenty-seven male SHR were randomly assigned to 3 treatment groups receiving N(2)O inhalation alone, APH stress alone or APH stress under N(2)O inhalation, using Wistar Kyoto rats (WKY) or non-N(2)O inhalation rats as controls. Systolic blood pressure (SBP) and heart rate (HR) variability were evaluated time-dependently using the wavelet method. While inhalation of N(2)O alone induced more powerful sympathomimetic actions in SHR than in WKY, circulatory and parasympathetic reactions were weaker. APH stress alone evoked significant inhibition of cardiac parasympathetic activity from immediately after exposure to hypoxic stress in SHR in contrast to WKY, facilitating tachycardia. This inhibition of parasympathetic activity in SHR continued without coupled changes in sympathetic activity. In SHR, APH under N(2)O inhalation decreased SBP and sympathetic activity more prominently and earlier than APH alone, and earlier than APH under N(2)O inhalation in WKY. Additionally, APH under N(2)O inhalation inhibited cardiac parasympathetic activity in SHR as compared to APH stress alone. In conclusion, APH under N(2)O inhalation in SHR potentially results in exacerbation of circulatory suppression from the earlier hypoxic phase, compared with non-N(2)O inhalation.

Immunohistochemical localization of SNARE proteins in dental pulp and periodontal ligament of the rat incisor.

Distribution of three soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) proteins, syntaxin-1, synaptosomal-associated protein of 25 kDa (SNAP-25), and vesicle-associated membrane protein-2 (VAMP-2), was examined in dental pulp and periodontal ligament of the rat incisor. In the trigeminal ganglion, syntaxin-1 and SNAP-25 immunoreactivity was predominately detected in medium- to large-sized neurons. Most syntaxin-1 immunoreactive neurons expressed SNAP-25. In contrast, VAMP-2 was localized in small- to medium-sized neurons and in slender-shaped cells surrounding SNAP-25-immunopositive neurons. When the inferior alveolar nerve, one of the mandibular nerve branches innervating the dental pulp and periodontal ligament, was ligated, SNARE proteins accumulated at the site proximal to the ligation. In the incisor dental pulp, all nerve fibers displayed immunoreactivity for syntaxin-1, SNAP-25, and VAMP-2. In the periodontal ligament of the incisor, almost all nerve fibers displayed both syntaxin-1 and SNAP-25 immunoreactivity, but lacked VAMP-2 immunoreactivity. SNAP-25 protein expression was localized around the vesicle membranes at the axon terminal of the periodontal mechanoreceptors. These present data suggest that these three SNARE proteins are synthesized at the trigeminal ganglion, transported centrally and peripherally, and expressed in sensory endings where apparent synapses are not present. Because those proteins participate in docking and exocytosis of synapse vesicles in the central nervous system, they might also contribute to vesicle exocytosis at receptive fields where apparent synapses are not present.

[Case report of dentatorubral pallidoluysian atrophy in a patient on a ketogenic diet].

We report a 16-year-old woman with dentatorubral pallidoluysian atrophy (DRPLA) on a ketogenic diet. She was scheduled for dental treatment under general anesthesia. She was diagnosed as having DRPLA at the age of 10. Medication included clonazepam, chlordiazepoxide, ethosuximide, sodium valproate and piracetam. She had been placed on a ketogenic diet at the age of 15, and seizures decreased. Preoperative laboratory data were normal except for serum cholesterol level (228 mg x dl(-1)) and blood ketones (1.8 mmol x l(-1)) with the use of Medisense Xtra. General anesthesia was induced using thiamylal, vecuronium, sevoflurane and maintained with sevoflurane and nitrous oxide-oxygen. Fluid infusion employed Solita T1 (glucose content of 2.6%: total 150 ml). Operation and general anesthesia presented no problems. We continued to infuse Solita T1 (total 350ml) for about 4 hours postoperatively. Ketogenic diet and additional medicine were started after 5 hours postoperatively. We measured perioperative and postoperative BS and blood ketones with the use of Medisense Xtra. She recovered from anesthesia without any significant complication.

Influence of acute progressive hypoxia on cardiovascular variability in conscious spontaneously hypertensive rats.

The purpose of this study is to examine the influence of acute progressive hypoxia on cardiovascular variability and striatal dopamine (DA) levels in conscious, spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). After preparation for measurement, the inspired oxygen concentration of rats was decreased to 10% within 5 min (descent stage), maintained at 10% for 10 min (fixed stage), and then elevated back to 20% over 5 min (recovery stage). The systolic blood pressure (SBP) and heart rate (HR) variability at each stage was calculated to evaluate the autonomic nervous system response using the wavelet method. Striatal DA during each stage was measured using in vivo microdialysis. We found that SHR showed a more profound hemodynamic response to progressive hypoxia as compared to WKY. Cardiac parasympathetic activity in SHR was significantly inhibited by acute progressive hypoxia during all stages, as shown by the decrease in the high frequency band of HR variability (HR-HF), along with transient increase in sympathetic activity during the early hypoxic phase. This decrease in the HR-HF continued even when SBP was elevated. Striatal DA levels showed the transient similar elevation in both groups. These findings suggest that acute progressive hypoxic stress in SHR inhibits cardiac parasympathetic activity through reduction of baroreceptor reflex sensitivity, with potentially severe deleterious effects on circulation, in particular on HR and circulatory control. Furthermore, it is thought that the influence of acute progressive hypoxia on striatal DA levels is similar in SHR and WKY.

Nasotracheal intubation under curve-tipped suction catheter guidance reduces epistaxis.

BACKGROUND: Nasotracheal intubation (NTI) has greater potential for trauma of nasopharyngeal mucosa than orotracheal intubation. The present study investigated the success rate of NTI and frequency of nasal bleeding using a curve-tipped suction catheter (CTSC) to guide nasotracheal tube advancement. METHODS: Subjects comprised 131 adult patients who under-went NTI. Subjects were randomly divided into two groups: a) NTI under CTSC guidance (G[+] group). The CTSC (14 Fr) was first inserted through the tracheal tube, with the tip of the CTSC emerging from the distal end of the tube. The curved tip was directed ventrally. Both tracheal tube and CTSC were advanced together through the nasopharynx; b) NTI without CTSC guidance (G[-] group). The tracheal tube was advanced into the nasal cavity and passed into the pharynx without CTSC guidance. The time required to pass the endotracheal tube through the nasal cavity (nasal passage time), success rate of nasal passage with nasotracheal tube, and the incidence and severity of nasal bleeding were compared. RESULTS: Success rate for nasal passage was 100% in the G(+) group (62/62) and 82.6% in the G(-) group (57/69; P = 0.0006). Frequency of nasal bleeding was significantly lower in the G(+) group (21/62, 33.9%) than in the G(-) group (37/69, 53.6%; P = 0.023). Severity of nasal bleeding was also significantly lower in the G(+) group than in the G(-) group (P = 0.030). CONCLUSIONS: Nasotracheal intubation under CTSC guidance increases the success rate of airway instrumentation, and also reduces the incidence and severity of epistaxis.