Hirofumi Arisaka

Upper airway obstruction associated with flexed cervical position after posterior occipitocervical fusion

Upper airway obstruction resulting from overflexion fixation of the cervical spine is a rare but life-threatening complication after cervical spine surgery. There are few reports of dyspnea after a posterior cervical fusion. We present the case of a 63-year-old woman with rheumatoid arthritis who developed an upper airway obstruction immediately after an O–C4 fusion. She was reintubated with a fiberoptic scope. Revision surgery allowing the angle to return to the neutral position was performed to ameliorate the overflexion of the cervical spine fixation and the consequent upper airway obstruction. After revision surgery, the upper airway obstruction disappeared. Our experience suggests that intraoperative use of fluoroscopy and extubation with a tube exchanger are recommended to avoid this complication, especially in patients at high risk of upper airway obstruction.

Comparative effects of verapamil, nicardipine, and nitroglycerin on myocardial ischemia/reperfusion injury.

The aim of this experiment was to establish whether verapamil, nicardipine, and nitroglycerin have (1) infarct size-limiting effects and (2) antiarrhythmic effects in in vivo rabbit hearts during ischemia/reperfusion. Rabbits received regional ischemia by 30 min of left anterior descending coronary artery occlusion followed by 3 hours of reperfusion under ketamine and xylazine anesthesia. The animals were randomly assigned to the following 4 treatment groups: a control group, a verapamil group, a nicardipine group, and a nitroglycerin group. A continuous infusion of verapamil, nicardipine, or nitroglycerin was initiated 5 min prior to ischemia. Infarct size/area at risk decreased in verapamil, and nitroglycerin. The incidence of ischemia-induced arrhythmia decreased in nicardipine, verapamil and nitroglycerin. The incidence of reperfusion-induced arrhythmias decreased in verapamil and nitroglycerin. From the present experimental results, verapamil and nitroglycerin rather than nicardipine did afford significant protection to the heart subjected to ischemia and reperfusion in a rabbit model.

Application of nasal flexible laryngeal mask airway in anesthesia for oral surgery

The laryngeal mask airway has been used increasingly in clinics but is seldom applied in anesthesia for oral surgery, as the mask occupies the middle of the mouth and tends to obstruct the surgical field. Here, we report the successful placement and usage of a nasal flexible laryngeal mask airway (FLMA) in an oral surgical procedure. Fifteen patients undergoing dental procedures under general anesthesia were studied. We clinically applied a previously reported method for inserting an FLMA with some modifications. There was no significant bleeding from the intubated nostril in any of the patients. None of the patients complained of sore throat, coughing, hoarseness, or any discomfort in the nose. Although we anticipate that further refinements of the technique may be possible and that the safety of this method using a nasal FLMA needs to be assessed in a greater number of patients, in this preliminary study we provide a proof-of-principle demonstration of the efficacy of nasal LMA ventilation as a method of airway management for oral surgery.

Application of gum elastic bougie to nasal intubation.

Gum elastic bougie (GEB), a useful device for difficult airway management, has seldom been used for nasotracheal intubation. Among 632 patients undergoing dental procedures or oral surgery, GEB was used successfully in 16 patients in whom conventional nasal intubation had failed because of anatomical problems or maldirection of the tip of the tracheal tube. We recommend that GEB should be applied from the first attempt for nasal intubation in patients with difficult airways.

Orexin induces excitation of respiratory neuronal network in isolated brainstem spinal cord of neonatal rat

Endogenous neuropeptides known as orexins (hypocretins) play important roles in the regulation of feeding, drinking, endocrine function, and sleep/wakefulness. Orexin neuron projection sites include the rostral ventrolateral medulla of brainstem, which is related to the control of breathing. Previous studies suggest that orexins modulate the central CO2 ventilatory response during wakefulness in rodent. In the present study, we examined the effects of the orexinergic system on central respiratory control by adding orexin into a superfusion medium in the isolated brainstem-spinal cord of neonatal rat. Exposure to orexin B resulted in dose-dependent increases in C4 burst rate via brainstem, but not spinal cord. These increases in C4 burst rate induced concomitant increases in the depolarizing cycle rate of pre-inspiratory (Pre-I) and inspiratory (Insp) neurons. Tonic discharge was induced on C4 recording, although the rhythmic bursts of Pre-I and Insp neurons were maintained. Expiratory (Exp) neurons were also depolarized on administration of orexin B. Our findings indicate that orexin B activates central respiratory activity, mainly through depolarization and decreases in membrane resistance in Pre-I and Insp neurons, and possibly through early initiation of the expiratory phase induced by depolarization of Exp neurons.

Donepezil reverses buprenorphine-induced central respiratory depression in anesthetized rabbits

Buprenorphine is a mixed opioid receptor agonist-antagonist used in acute and chronic pain management. Although this agents analgesic effect increases in a dose-dependent manner, buprenorphine-induced respiratory depression shows a marked ceiling effect at higher doses, which is considered to be an indicator of safety. Nevertheless, cases of overdose mortality or severe respiratory depression associated with buprenorphine use have been reported. Naloxone can reverse buprenorphine-induced respiratory depression, but is slow-acting and unstable, meaning that new drug candidates able to specifically antagonize buprenorphine-induced respiratory depression are needed in order to enable maximal analgesic effect without respiratory depression. Acetylcholine is an excitatory neurotransmitter in central respiratory control. We previously showed that a long-acting acetylcholinesterase inhibitor, donepezil, antagonizes morphine-induced respiratory depression. We have now investigated how donepezil affects buprenorphine-induced respiratory depression in anesthetized, paralyzed, and artificially ventilated rabbits. We measured phrenic nerve discharge as an Index of respiratory rate and amplitude, and compared discharges following the injection of buprenorphine with discharges following the injection of donepezil. Buprenorphine-induced suppression of the respiratory rate and respiratory amplitude was antagonized by donepezil (78.4 +/- 4.8 %, 92.3% +/- 22.8 % of control, respectively). These findings indicate that systemically administered donepezil restores buprenorphine-induced respiratory depression in anesthetized rabbits.

Comparison of tracheal diameter measured by chest x-ray and by computed tomography

Assessments of tracheal diameter (TD) are important to select proper endotracheal tubes. Previous studies have used X-ray and physical indices to estimate tracheal diameter but these may not reflect the actual TD. We compared TD measured by X-ray (TD-XP) and by computer tomography (TD-CT) in 200 patients. Also, we analyzed correlation of TD-CT with physical indices such as age, height, weight, and BMI. TD-XP and TD-CT were significantly correlated (male: n = 55, P = .0146; female: n = 91, P = .001). TD-XP was 0.4 mm wider in male and 1.0 mm wider in female than TD-CT. However, correlation coefficients of TD-XP and TD-CT are very weak (male: r = 0.36; female: r = 0.653). TD-CT did not correlate with age, height, weight, or BMI. Our findings suggest that correlations of TD-XP and TD are statistically significant but not clinically significant. Physical indices are not useful to estimate TD.

Perioperative management of obstructive sleep apnea with nasal continuous positive airway pressure.

The high risks associated with general anesthesia in obstructive sleep apnea syndrome (OSAS) patients have been reported. Many authors have suggested that the intraoperative administration of opioids and sedatives should be limited or avoided because these drugs selectively impair muscle activity in the upper airway. We report the case of an OSAS patient who was managed with nasal continuous positive airway pressure (NCPAP) and treated safely in spite of the use of conventional anesthetic and analgesic agents typically used for patients without OSAS. She had little pain during the perioperative period. It is suggested that NCPAP is an effective treatment for not only preventing airway obstructive apnea but for allowing the administration of anesthetic and analgesic drugs without major complications.

Effects of Lidocaine on Ischemia/Reperfusion Injury in In vivo Rabbit Hearts

Objective: The aim of this study was to investigate the cardioprotective effects of lidocaine administered at three different timings, as indexes of hemodynamics, infarct size, antiarrhythmic action, and changing activation time by electrocardiogram in in vivo rabbit hearts. Methods: Thirty two rabbits received regional ischemia by 30 min of left anterior descending coronary artery occlusion followed 3 hours of reperfusion under ketamine and xylazine anesthesia. The animals were randomly assigned to the following 4 treatment groups: a control group, a lidocaine-preconditioned group, a lidocainepostconditioned group, and a lidocaine-continuous administration group. Results: The ratio of areas at risk revealed no significant difference among all groups. Mean infarct size of the area at risk was significantly less in a lidocaine-continuous administration group than other 3 groups. The incidence of arrhythmias during myocardial ischemia was no significant difference between a control group and other 3 groups. The incidence of arrhythmias during reperfusion was no significant difference among all groups. However, lidocaine depressed the activation time which was prolonged by ischemia.

AirWay Scope™ for Difficult Ventilation in a Patient With Epiglottic Cyst

Epiglottic cysts often cause difficulty in airway management, with potential serious life-threatening complications. 1 This case report describes a patient with an epiglottic cyst in whom mask ventilation became difficult after induction of anesthesia. Immediately, an AirWay Scope™ (TMAWS-S100; Pentax, Japan) was inserted orally, and the location of the epiglottis was clarified to assess the reason for difficulty with ventilation. This case demonstrates usefulness of the AirWay Scope in patients with epiglottic cyst.