Path integral approach to universal dynamics of reservoir computers.

In this work, we give a characterization of the reservoir computer (RC) by the network structure, especially the probability distribution of random coupling constants. First, based on the path integral method, we clarify the universal behavior of the random network dynamics in the thermodynamic limit, which depends only on the asymptotic behavior of the second cumulant generating functions of the network coupling constants. This result enables us to classify the random networks into several universality classes, according to the distribution function of coupling constants chosen for the networks. Interestingly, it is revealed that such a classification has a close relationship with the distribution of eigenvalues of the random coupling matrix. We also comment on the relation between our theory and some practical choices of random connectivity in the RC. Subsequently, we investigate the relationship between the RC's computational power and the network parameters for several universality classes. We perform several numerical simulations to evaluate the phase diagrams of the steady reservoir states, common-signal-induced synchronization, and the computational power in the chaotic time series inference tasks. As a result, we clarify the close relationship between these quantities, especially a remarkable computational performance near the phase transitions, which is realized even near a nonchaotic transition boundary. These results may provide us with a new perspective on the designing principle for the RC.

[Perioperative Blood Pressure Changes in a Patient Undergoing One-stage Bilateral Nephrectomy for Treatment-resistant Hypertension].

We describe our experience with a 15-year-old girl receiving anesthesia during one-stage bilateral nephrectomy for treatment-resistant hypertension due to chronic renal failure. Approximately 10 minutes after removal of both kidneys, a reduction in blood pressure associated with decreased cardiac contractile force was observed and this necessitated catecholamine administration. However, blood pressure was sufficiently improved approximately 60 minutes later, and catecholamine administration was not necessary after she awoke from anesthesia. Although administration of an antihypertensive agent as required after surgery, as had been the case before surgery, the dose was gradually tapered and we were able to stop drug administration on postoperative day 31.

[Comparison of thoracoscopic and open repair of esophageal atresia with tracheoesophageal fistula].

BACKGROUND: With the increasing use of endoscopic surgery in children, several papers report the comparison between the thoracoscopic and open repair of the neonatal esophageal atresia with tracheoesophageal fistula (EA/TEF). Most of them focus on the duration and outcome of the surgery with few focusing on the neonatal tolerance to the thoracoscopic procedure and intraoperative anesthetic management. METHODS: We retrospectively reviewed the repair surgery of EA/TEF performed during 2001 and 2006 in our institution and compared thoracoscopic repair (thoracoscopy group, n=5) with open repair (open group, n=7). The right main bronchus was blocked with Fogarty catheter in thoracoscopic repair, but not in open repair. Thoracoscopic repair was performed with insufflation of carbon dioxide (3-5 mmHg). RESULTS: The thoracoscopy group had a higher incidence of intraoperative hypercapnia and acidosis and required higher inspired oxygen fraction. On admission to ICU Pa(CO2) was in the normal range in both groups and there was no difference in the duration of mechanical ventilation and ICU stay. CONCLUSIONS: Hypercapnia and acidosis were severer in thoracoscopy group. Careful perioperative adjustment of inspired oxygen fraction and ventilator setting is required.

[Epidural blood patch for postdural puncture headache in a five-year-old child].

A case was presented of a 5-year-old girl who suffered an accidental dural puncture during placement of an epidural catheter under general anesthesia for orthopedic surgery. She complained of headache 4 days after the operation, which was relieved on supine position but became worse on sitting position. Her symptoms failed to respond to conservative management. An epidural blood patch was performed under general anesthesia and completely resolved her symptoms. The reported incidence of epidural blood patch for post dural puncture headache following accidental dural puncture in children is low. We outline this case and the consideration for management for epidural blood patch in pediatric patients.

The sound intensity and characteristics of variable-pitch pulse oximeters.

OBJECTIVE: Various studies worldwide have found that sound levels in hospitals significantly exceed the World Health Organization (WHO) guidelines, and that this noise is associated with audible signals from various medical devices. The pulse oximeter is now widely used in health care; however the health effects associated with the noise from this equipment remain largely unclarified. Here, we analyzed the sounds of variable-pitch pulse oximeters, and discussed the possible associated risk of sleep disturbance, annoyance, and hearing loss. METHODS: The Nellcor N 595 and Masimo SET Radical pulse oximeters were measured for equivalent continuous A-weighted sound pressure levels (L(Aeq)), loudness levels, and loudness. Pulse beep pitches were also identified using Fast Fourier Transform (FFT) analysis and compared with musical pitches as controls. RESULTS: Almost all alarm sounds and pulse beeps from the instruments tested exceeded 30 dBA, a level that may induce sleep disturbance and annoyance. Several alarm sounds emitted by the pulse oximeters exceeded 70 dBA, which is known to induce hearing loss. The loudness of the alarm sound of each pulse oximeter did not change in proportion to the sound volume level. The pitch of each pulse beep did not correspond to musical pitch levels. CONCLUSIONS: The results indicate that sounds from pulse oximeters pose a potential risk of not only sleep disturbance and annoyance but also hearing loss, and that these sounds are unnatural for human auditory perception.

[Spinal anesthesia using hyperbaric bupivacaine HCl for cesarean section].

BACKGROUND: We performed this prospective study to determine the proper amount of hyperbaric bupivacaine hydrochloride as a spinal anesthetic agent for cesarean section. METHODS: The parturients were randomly allocated to receive one of four spinal agents in a blind manner; tetracaine 10 mg (control), bupivacaine 10, 12.5 and 15 mg. Morphine HCl 0.1 mg was added to each agent and the total volume was adjusted to 3.1 ml with 10% glucose solution. RESULTS: All the four spinal agents provided an adequate analgesic level (T 5) without serious complications. Among the three dosages of bupivacaine, the time interval requiring for anesthetic level to reach T 5 tended to be shorter with a larger amount of bupivacaine. The incidence of intraoperative supplemental analgesic and hypotension and the dosage of ephedrine used to treat hypotension were greater in the patients anesthetized with tetracaine 10 mg than in those anesthetized with bupivacaine 10 mg, which is equipotent to tetracaine 10 mg. CONCLUSIONS: 1. As a spinal anesthetic agent for cesarean section, hyperbaric bupivacaine is superior to tetracaine. 2. Hyperbaric bupivacaine 10 mg, 12.5 mg or 15 mg can be used safely and effectively as a spinal agent for cesarean section. 3. High dose bupivacaine is recommended in an urgent case, and low dose bupivacaine is recommended when maternal hypotension must be strictly avoided.

[Anesthesia for a woman with triplet pregnancy presenting with acute abdomen after the recent epidural blood patch].

We report a case of primipara with triplet pregnancy who underwent combined spinal and epidural anesthesia 10 weeks after epidural blood patch. At 15 weeks of gestation, a woman with triplet gestation underwent Shirodkar operation under spinal anesthesia and subsequent epidural blood patch as a treatment of post-dural puncture headache. At 26 weeks she presented with acute abdomen and laparotomy was scheduled. Spinal anesthesia was selected with an epidural catheter inserted in case of prolonged operation and for postoperative pain control. The placement of an epidural catheter was without problem. Laparotomy revealed right paraovarian cyst torsion and the right salpingo-paraoophocystectomy was performed. Patient-controlled analgesia with epidural bupivacaine and fentanyl was effectively continued for two days. Postoperative course was uneventful and the triplets were delivered by cesarean section at 35 weeks.

A small preoperative test dose of intravenous fentanyl can predict subsequent analgesic efficacy and incidence of side effects in patients due to receive epidural fentanyl.

UNLABELLED: Because individual variation is a likely factor affecting both the incidence and severity of side effects and the analgesic efficacy of epidural opioids, assessment of individual variation could be useful in deciding optimal dosage. By evaluating the response to a small test dose of IV fentanyl, we designed this study to predict the degree of pain relief and the incidence of side effects in patients who would be receiving postoperative epidural fentanyl. Before the induction of anesthesia, 50 micro g of fentanyl was administered IV, and 2 min after fentanyl, the patient response was evaluated. Twenty-three patients, who reported nausea, sleepiness, dizziness, sensation of warmth, and other symptoms, were categorized as responders (Group R); the remaining 20 patients were categorized as nonresponders (Group NR). At the completion of surgery, infusion of epidural fentanyl was administered (0.3 mg/d in 0.25% bupivacaine) for 96 h. At postoperative Hours 6 and 24, Group R had significantly lower visual analog scale scores for postoperative pain intensity and required fewer analgesics than Group NR. The incidence of side effects, however, was 74% for Group R and 10% for Group NR (P < 0.05), and side effects were more serious in Group R. This study demonstrates that preoperative administration of a small dose of fentanyl during the induction of anesthesia enables prediction of the analgesic efficacy of postoperative epidural fentanyl and the incidence and severity of side effects. IMPLICATIONS: Preoperative administration of a small dose of fentanyl during the induction of anesthesia enables prediction of the analgesic efficacy of postoperative epidural fentanyl and the incidence and severity of side effects.