Reduction in amino-acid-induced anti-hypothermic effects during general anesthesia in ovariectomized rats with progesterone replacement.

PURPOSE: The aim of the present study was to determine whether the ovarian hormones, estrogen and progesterone, had different influences on amino-acid-induced anti-hypothermic effects during general anesthesia. METHODS: Ovariectomized Sprague-Dawley female rats were divided into four groups: those administered 17ß-estradiol plus saline or an amino acid mixture (E2-Sal and E2-AA, respectively) and progesterone plus saline or an amino acid mixture (P-Sal and P-AA, respectively). Five weeks after ovariectomy, rats were given either E2 or P and then administered either Sal or AA solution for 180 min during anesthesia with sevoflurane. Rectal temperatures were measured. RESULTS: Rectal temperatures were significantly higher in the E2-AA group than in the E2-Sal group 165 and 180 min after initiating the infusion of the test solutions. However, no significant differences were observed between the P-treated groups. The phosphorylation of 4E-BP1 and S6K1 was significantly greater in the E2-AA group than in the E2-Sal group (P < 0.05, P < 0.001, respectively). In contrast, the phosphorylation of 4E-BP1 was significantly lower in the P-AA group than in the P-Sal group (P < 0.001). CONCLUSIONS: These results suggest that progesterone reduces amino-acid-induced anti-hypothermic effects during general anesthesia.

A prospective randomized multicenter comparative study of BLM-240 (desflurane) versus sevoflurane in Japanese patients.

The present study was conducted to evaluate the efficacy and safety of BLM-240 (desflurane) in comparison to sevoflurane in Japanese patients. A total of 216 patients were enrolled in this randomized comparative study at 15 medical institutions. The patients received either BLM-240 with 50-70 % N2O in O2 (n = 111), BLM-240 with 30 % O2 in air (n = 55), or sevoflurane with 50-70 % N2O in O2 (n = 50). Efficacy was evaluated by an efficacy rate based on an efficacy evaluation criteria and recovery time to extubation from the discontinuation of the anesthetics. Safety was evaluated by incidence of adverse drug reactions (ADR) and other clinical indicators. The efficacy rate of BLM-240 was 98.8 % (164/166 patients), indicating that BLM-240 is effective as an anesthetic. Time from discontinuation of anesthetic delivery to extubation was 9.7 ± 0.6 min in the BLM-240/N2O group and 14.3 ± 0.9 min in the sevoflurane/N2O group, meeting the pre-defined non-inferiority criteria of BLM-240 to sevoflurane. There was no statistically significant difference in the incidence of total ADR between the BLM-240 group (62.0 %) and sevoflurane group (48.0 %). The results indicate that BLM-240 is an effective and safe inhalation anesthetic in Japanese patients.

[Anesthetic management in a case of myotonic distrophy with dexmedetomidine].

We encountered a 53-year-old woman with myotonic dystrophy for a total abdominal hysterectomy. In patients with myotonic dystrophy, hypersensitivity to anesthetic drugs, especially muscle relaxants and opioids, may complicate postoperative management. Combined spinal and epidural block was used in this patient to prevent the occurrence of potential postoperative complications associated with general anesthesia, including respiratory depression. In addition, dexmedetomidine was used for sedation during surgery, because the patient had mental retardation associated with this disease. Airway obstruction was observed after the initial administration of dexmedetomidine at 2 microg x kg(-1) x hr(-1). Therefore, the dose of the drug was reduced to a maintenance dose of 0.2% microg x kg(-1) x hr(-1), resulting in adequate sedation. Dexmedetomidine was proved to be useful in this case; however, use of the drug should be carefully started at a low initial dose in patients with myotonic dystrophy.

[Sedation during day surgery for oral implantation].

BACKGROUND: Oral implantation surgery is performed under sedation without monitoring consciousness, but BIS monitor is useful for evaluation of sedation level. Therefore we investigated whether BIS monitor is useful for this surgery. METHODS: Sixty-four patients scheduled for oral implant surgery were analyzed retrospectively. Patients were classified into two groups; BIS monitor was used (Group B) or not (Group A). We investigated the dose of midazolam necessary for intraoperative sedation, and for patient's satisfaction. RESULTS: The dose of midazolam in Group B was greater than that in Group A. The dose in Group B was higher than that in Group A according to patient's satisfaction. CONCLUSIONS: BIS monitor is useful for oral implant surgery.

Protein malnutrition prevents heat conservation induced by amino acid infusion during general anesthesia in rats.

The intravenous administration of an amino acid (AA) mixture during general anesthesia reduces anesthesia-induced hypothermia. AA-induced skeletal muscle protein synthesis and thermogenesis play important roles in the antihypothermic effects of AAs. We hypothesized that a preanesthetic dietary protein deficiency impairs the antihypothermic effects of AAs during general anesthesia due to a reduction in thermogenesis caused by a decrease in muscle protein synthesis. Sprague-Dawley rats were divided into 4 groups: fed a control diet plus saline (CON-SAL) or the AA mixture (CON-AA), and fed a protein-free diet plus saline (PF-SAL) or the AA mixture (PF-AA). SAL solution or AA mixture solution was infused for 180 minutes during sevoflurane anesthesia, and rectal temperatures were measured. Rectal temperatures were significantly higher in the CON-AA group than in the PF-AA group 90 to 180 minutes after initiating the intravenous infusion of the test solutions. There was no significant difference between the PF-SAL and PF-AA groups. Plasma insulin concentrations were significantly higher in the CON-AA group than in the PF-AA group (P < .05). The phosphorylation states of protein kinase B, mammalian target of rapamycin, and eukaryotic initiation factor 4E-binding protein 1 were significantly greater in the CON-AA group than in the PF-AA group (P < .05, P < .05, and P < .01, respectively). Our results indicated that a dietary protein deficiency before general anesthesia impaired the antihypothermic effects of an AA mixture infusion during general anesthesia by decreasing muscle protein synthesis through the insulin-stimulated phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin complex 1 signaling pathway followed by metabolic heat production.

Edaravone and cyclosporine A as neuroprotective agents for acute ischemic stroke.

It is well known that acute ischemic stroke (AIS) and subsequent reperfusion produce lethal levels of reactive oxygen species (ROS) in neuronal cells, which are generated in mitochondria. Mitochondrial ROS production is a self-amplifying process, termed "ROS-induced ROS release". Furthermore, the mitochondrial permeability transition pore (MPTP) is deeply involved in this process, and its opening could cause cell death. Edaravone, a free radical scavenger, is the only neuroprotective agent for AIS used in Japan. It captures and reduces excessive ROS, preventing brain damage. Cyclosporine A (CsA), an immunosuppressive agent, is a potential neuroprotective agent for AIS. It has been investigated that CsA prevents cellular death by suppressing MPTP opening. In this report, we will outline the actions of edaravone and CsA as neuroprotective agents in AIS, focusing on their relationship with ROS and MPTP.

Design and its application of the f(n)-zeta chart capable of direct readout of the highest frequency indicating the limit of obtaining distortion-free waveforms.

We have already reported that the highest frequency (f(h)) could serve as an index for evaluating the fidelity of pressure waveform derived via a catheter manometer system and be read off by the f(n)-zeta chart. Fh is determined by the natural frequency (f(n)) and damping coefficient ( zeta ) in the frequency characteristics of the system. Inversely, f(h) determines two pairs of f(n) and zeta in the f(n)-zeta chart, one in the case of zeta < 0.7 and the another zeta > 0.7. Then, each pair of f(n) and zeta determines respectively the resonant frequency (f(r)) and its amplitude (Ar) ( zeta < 0.7), or the corner frequency (f(c)) and its amplitude (Ac) ( zeta > 0.7) in the frequency characteristics. Thus, the point (f(r), Ar) or (f(c), Ac) represents the position of f(h) projected in the frequency characteristics. Repeating the same operation for other f(n) and zeta corresponding to the same f(h), yields the curve of f(h) in the frequency characteristics. Calculations for other f(h)'s provide a group of curves. Frequency characteristics of pulmonary artery catheters were measured and overwritten thereupon, resulting in f(h)'s to be from 1.2 to 3.2 Hz. These results were in agreement with that calculated by the conventional method.

Differences in penetration force of intravenous catheters: effect of grinding methods on inner needles of intravenous catheters.

OBJECTIVES: To compare penetration forces of intravenous catheters based on two grinding methods used for the inner needle tip. METHOD: Forty intravenous catheters were divided into two groups according to two inner needle grinding methods: Lancet and Backcut. To compare the characteristics of inner needles, 18 gauge Surflo outer catheters, were attached to all inner needles. We measured penetration forces by attaching a "Push-Pull-Gauge" to the chamber of intravenous catheters, then we penetrated intravenous catheters through a 0.04-mm thick polyethylene film. The penetration velocity was 3.3 mm/sec. we measured penetration forces at 30- and 45-degree penetration angles. RESULTS: There was no significant difference in the penetration forces of inner needle and outer catheter between the two groups at the 45-degree penetration angle. Penetration forces of the inner needle and the outer catheter in the Backcut group was significantly lower than those of the Lancet group at the 30-degree penetration angle. The penetration force of the outer catheter was reduced from 0.3 N to 0.18 N, a 40 % reduction at 30-degree penetration angle. Computerized measurements of penetration holes indicate that the Y-shaped incision mark of the Backcut leaves larger incision hole than the actual puncture size. We hypothesize that the Y-shaped incision mark creates more efficient path for the outer catheter to advance. Therefore, lower penetration force was indicated compared to the other group. CONCLUSION: Backcut shows less penetration force of inner needles of peripheral intravenous catheters than lancet.

Blind endobronchial insertion of a movable bronchial blocker attached to an endotracheal tube, Univent tube.

The endotracheal tube with a movable bronchial blocker, Univent tube, used to effect one-lung ventilation is easy to use in endotracheal intubation. However, problems are often encountered when inserting the blocker into the bronchus. We herein describe a method which enables the easy blind insertion of the blocker into the left or right bronchus. The techniques of inserting the blocker into the left main stem bronchus will be described. With the patient in a supine position, the head of the patient is moved to the left. The operator then places his right hand fingers near the cricoid and presses to displace the larynx of the patient toward the right. While performing this procedure, the operator advances the blocker using the left hand. Finally, using a bronchoscope, the placing of the blocker is to be ascertained in an appropriate position inside the left bronchus. When strong resistance is left, the blocker should be retracted, the force of laryngeal displacement is altered and, then, the blocker is inserted again in a resistance-free manner. We have so far experienced no complications such as severe tracheobronchial hemorrhage, tracheobronchial perforation of laryngeal dislocation. We herein describe a useful and simple method for inserting the bronchial blocker of the Univent tube into the bronchus.

Effects of intravenous amino acids on anesthesia-induced hypothermia in ovariectomized rats.

A decrease in core temperature during general anesthesia is attenuated by infusion of an intravenous amino acid mixture. The purpose of the present study was to investigate the influence of physical and endocrine changes caused by ovariectomy on the inhibitory effect of amino acid infusion on anesthesia-induced hypothermia. Sprague-Dawley female rats were divided into a sham-operated (Sham) group and an ovariectomized (OVX) group. Saline solution or an amino acid mixture solution was infused for 180 min during sevoflurane anesthesia, and the rectal temperature was measured (4 groups). Intraperitoneal white adipose tissue mass, bilateral gastrocnemius weight and plasma insulin levels were measured. In the Sham rats, no inhibitory effect of the amino acid mixture on anesthesia-induced hypothermia was found, while in the OVX rats, hypothermia was significantly decreased. The intraperitoneal fat weight/body weight ratio was significantly higher in the OVX rats than in the Sham rats, but the gastrocnemius weight/body weight ratio was not significantly different. After amino acid infusion, the plasma insulin level was significantly higher in the OVX rats than in the Sham rats. In conclusion, our findings suggest that, in rats, ovarian function or female hormone affects protein turnover mediated by increase in insulin secretion and, thus, decreases the inhibitory effect of an infusion of amino acid mixture on anesthesia-induced hypothermia.

The effect of amino acid infusion on anesthesia-induced hypothermia in muscle atrophy model rats.

An infusion of amino acids stimulates heat production in skeletal muscle and then attenuates the anesthesia-induced hypothermia. However, in a clinical setting, some patients have atrophic skeletal muscle caused by various factors. The present study was therefore conducted to investigate the effect of amino acids on the anesthesia-induced hypothermia in the state of muscle atrophy. As the muscle atrophy model, Sprague-Dawley rats were subjected to hindlimb immobilization for 2 wk. Normal rats and atrophy model rats were randomly assigned to one of the two treatment groups: saline or amino acids (n=8 for each group). Test solutions were administered intravenously to the rats under sevoflurane anesthesia for 180 min, and the rectal temperature was measured. Plasma samples were collected for measurement of insulin, blood glucose, and free amino acids. The rectal temperature was significantly higher in the normal-amino acid group than in the muscle atrophy-amino acid group from 75 to 180 min. The plasma insulin level was significantly higher in the rats given amino acids than in the rats given saline in both normal and model groups. In the rats given amino acids, plasma total free amino acid concentration was higher in the model group than in the normal group. These results indicate that skeletal muscle plays an important role in changes in body temperature during anesthesia and the effect of amino acids on anesthesia-induced hypothermia decreases in the muscle atrophy state. In addition, intravenous amino acids administration during anesthesia induces an increase in the plasma insulin level.

Increased dosage of propofol in anesthesia induction cannot control the patient's responses to insertion of a laryngeal mask airway.

An increased dosage of propofol is frequently administered to reduce responses to insertion of the laryngeal mask airway (LMA). However, its clinical effect remains unknown. We investigated whether an increased dosage of propofol reduces responses to LMA insertion. Sixty adult patients were divided into 3 groups according to induction dosage of propofol (2.0 mg/kg, 2.5 mg/kg and 3.0 mg/kg). The patient's responses including body movement and the upper airway reflex were observed. The bispectral index (BIS) score as the index of the sedation level was monitored. There were no significant differences among the three groups in responses to LMA insertion, and no correlation was seen between the BIS score and the responses. These results suggest that propofol alone at clinical dosage levels does not completely control responses to LMA insertion. It is also suggested that the monitoring of BIS score is not effective in predicting responses to LMA insertion. Combination of propofol and analgesics such as fentanyl may be useful in reducing responses to LMA insertion.

Development of a safe guidewire.

As the result of a locking phenomenon that may occur in a guidewire inside a metal puncture needle when using the Seldinger technique to insert a central venous catheter, the guidewire can break and cause an embolism. To counter this possibility we devised a guidewire with a structure that made it difficult for locking to occur and compared it to conventional guidewires. Conventional guidewires are wound lengthways with a spring. The improved version has a special multi-ply structure. A series of 100 cases were divided into two groups: group A, the conventional guidewire group; and group B, the improved guidewire group. We punctured the internal jugular vein and attempted insertion of the guidewire through the side hole of a 22-gauge metal needle. We then compared the frequency of locking and the frequency of bending of the guidewire tips that have been withdrawn. In group A, locking occurred in 72% of the cases where the guidewire was unable to be inserted, but this figure was 0% in group B. The improved guidewire has the advantage of reducing the risk of locking and of guidewire breakage.

Relationship between aortic-to-radial arterial pressure gradient after cardiopulmonary bypass and changes in arterial elasticity.

BACKGROUND: An aortic-to-radial arterial pressure gradient may develop during and after cardiopulmonary bypass (CPB). The mechanisms of this pressure gradient remain controversial. To clarify the cause of the pressure gradient after CPB, the authors investigated the relationship between the pressure gradient and changes in the pulse wave velocity (PWV) before and after CPB. METHODS: The pressure gradient from the aorta to the radial artery and a change in PWV were measured with a wire (0.37 mm in diameter) tipped with a miniature pressure transducer in 12 patients undergoing cardiac surgery. The pressure distributions and waveforms were measured and recorded with electrocardiograph. The PWV was calculated by measuring the propagation time between the R wave of the electrocardiograph and the rising point of the arterial pressure waveform at 10-cm intervals. RESULTS: After CPB, 7 of 12 patients demonstrated a marked pressure gradient. In these patients, the pressure distribution showed a gradual decrease toward the periphery without a precipitous step-down in pressure at any one specific anatomic location. The PWV decreased as the intraarterial pressure decreased from the aorta to the radial artery, and the relative arterial elasticity decreased linearly toward the periphery. CONCLUSIONS: The results showed that the decrease in PWV implies a decrease in arterial elasticity, and the decrease in the arterial elasticity correlated with the decrease in intraarterial pressure. These findings demonstrated that a radial artery pressure lower than the aortic pressure after CPB may be due to the decrease in arterial elasticity.