Katsumi Okuyama

The effective time and concentration of nitrous oxide to reduce venipuncture pain in children

STUDY OBJECTIVE To investigate the time of administration and concentration of inhaled nitrous oxide (N(2)O) needed to reduce the pain associated with intravenous (i.v.) cannulation in children. DESIGN Prospective, randomized study. SETTING Operating room of a childrens hospital. PATIENTS 73 ASA physical status I and II children, aged 6-15 years, scheduled for elective day or non-day surgery. INTERVENTIONS Children were randomly allocated to one of 4 groups prior to i.v. insertion of a 24-gauge catheter in the dorsum of the hand: Group 1 (n = 18): 50% N(2)O in O(2) for three minutes; Group 2 (n = 18): 50% N(2)O in O(2) for 5 minutes; Group 3 (n = 18): 70% N(2)O in O(2) for three minutes; or Group 4 (n = 19): 70% N(2)O in O(2) for 5 minutes. MEASUREMENTS Just after the venous cannulation, degree of pain was assessed by examining the faces of the patient by the parent and an operating room nurse. MAIN RESULTS Pain scores obtained from parents of children in Groups 3 and 4 were significantly lower than from those in Groups 1 and 2. Pain scores from the nurse in Group 3 was significantly lower than those in Group 1. However, there was no significant difference in pain score between Group 3 and Group 4. Frequency of side effects was similar among the 4 groups. CONCLUSIONS Seventy percent N(2)O in O(2) given for three minutes was effective for reducing venipuncture pain in children.

The direct effects of propofol on pial microvessels in rabbits.

Propofol is widely used for neurosurgical anesthesia; however, its effects on the pial microvasculature are unknown. We therefore evaluated the direct effects of propofol on pial microvessels in rabbits. Pial microcirculation was visualized using a closed cranial window technique in 20 Japanese white rabbits. In the first experiment (n=14), after baseline hemodynamic measurements, the cranial window was superfused with 5 increasing concentrations of propofol (10−8, 10−7, 10−6, 10−5, 10−4 mol/L; n=8) or intralipid (at comparable concentrations; n=6) dissolved in artificial cerebrospinal fluid for 7 minutes each. A typical anesthetic concentration of 5 μg/mL corresponds to 10−6 mol/L. In the second experiment (n=6), phenylephrine 10−6 mol/L and nitroglycerin 10−6 mol/L were applied topically for 7 minutes under pentobarbital anesthesia. In the third experiment (n=3), electroencephalogram and bispectral index were measured under pentobarbital anesthesia. Diameters of selected pial arterioles and venules were visualized with a microscope-video capture unit combination and subsequently measured with a digital video analyzer. Topical application of propofol at 10−8, 10−7, 10−6, or 10−5 mol/L did not alter the diameters of the pial microvessels; however, at 10−4 mol/L propofol induced dilation in large and small arterioles, along with venular dilation. Intralipid alone did not have any significant effect on vessel diameters. Phenylephrine and nitroglycerin produced pial arteriolar and venular constriction and dilation, respectively. Phenylephrine constricted and nitroglycerin dilated pial arterioles and venules. Pentobarbital did not produce either burst suppression or an isoelectric electroencephalogram. The results confirm our hypothesis: clinically relevant concentrations of propofol, that is, approximately 10−6 mol/L, do not dilate pial arterioles or venules.

Urinary bladder and oesophageal temperatures correlate better in patients with high rather than low urinary flow rates during non-cardiac surgery

Background and objective: To investigate the effect of urinary flow rate on the urinary bladder temperature, we compared the accuracy and precision of urinary bladder temperature with oesophageal temperature at both high and low urine flow rates. Methods: Twenty‐four patients ASA physical status I or II who were undergoing tympanoplasty were randomly assigned to two groups with different intravenous fluid volumes: high (10 mL kg−1 h−1, n = 12) and low (3 mL kg−1 h−1, n = 12). General anaesthesia was induced with propofol and maintained with sevoflurane (1.5‐2.5%) in nitrous oxide and oxygen. Urinary bladder temperature was measured using a Foley urinary catheter; distal oesophageal temperature was measured using a stethoscope thermocouple. These temperatures were measured every 5 min during surgery and the accuracy and precision of urinary bladder temperature with oesophageal temperature were determined using regression and Bland and Altman analyses. Results: The correlation coefficient for oesophageal and urinary bladder temperature was 0.90 in the high urinary volume group and 0.75 in the low urinary volume group. The offset (oesophageal‐urinary bladder) was −0.13 ± 0.32°C and −0.46 ± 0.45°C, respectively. Conclusion: Urinary bladder temperature appears to be more accurate at high urinary flow rates than at low urinary flow rates for clinical use.

The shivering threshold in rabbits with JM-1232(-), a new benzodiazepine receptor agonist.

BACKGROUND: JM-1232(−) is a novel isoindoline derivative which shows sedative and hypnotic activities through the benzodiazepine site of &ggr;-aminobutyric acid type A (GABAA) receptors. Typical doses of midazolam, another GABAA receptor agonist, slightly reduce the shivering threshold in humans. We thus determined the extent to which JM-1232(−) decreases the shivering threshold. METHODS: Eighteen rabbits, lightly anesthetized with isoflurane 0.2 minimum alveolar anesthetic concentration (MAC), were randomly assigned to infusions of 1) saline (control), 2) 0.01 mg · kg−1 · min−1 JM-1232(−), or 3) 0.1 mg · kg−1 · min−1 JM-1232(−). Body temperature was reduced at a rate of 2-3°C/h by perfusing water at 10°C though a U-shaped plastic tube positioned in the colon. Cooling continued until shivering was observed by an investigator blinded to treatment, or until core temperature reached 34°C. Core temperatures were recorded from the distal esophagus, and core temperature at the onset of shivering defined the threshold. Data were analyzed by one-way analysis of variance with Student-Newman-Keuls tests. Results are presented as means ± sd; P < 0.05 was considered statistically significant. RESULTS: The rabbits given a saline infusion shivered at 36.5 ± 0.3°C. Five of the six rabbits given JM-1232(−) at a rate of 0.01 mg · kg−1 · min−1 shivered at 35.7 ± 0.8°C, and one of these rabbits failed to shiver at 34.0°C. None of the rabbits given JM-1232(−) at a rate of 0.1 mg · kg−1 · min−1 shivered before reaching the 34.0°C cutoff temperature. CONCLUSION: A low dose of JM-1232(−) reduced the shivering threshold in rabbits approximately 0.8°C which is similar to the effects in humans given premedication doses of midazolam. In contrast, a 10-fold larger dose reduced the threshold more than 2.5°C. This is a substantial decrement and might facilitate induction of therapeutic hypothermia.

Forced-air warming effectively prevents midazolam-induced core hypothermia in volunteers.

Background and objective Midazolam is a commonly used sedative and anaesthetic adjuvant and the agent is known to decrease core temperature by core-to-periphery redistribution of heat. We tested the hypothesis that forced-air warming could effectively prevent midazolam-induced hypothermia. Methods Six healthy male volunteers were studied over 3 days. On the first day, the volunteers were alert during a 30 min control period with forced-air warming. On the second day, after the volunteers were vasoconstricted, 75 μg kg−1 midazolam was injected intramuscularly and they were covered with a cotton blanket. On the third day, after the volunteers were vasoconstricted, 75 μg kg−1 midazolam was again administered and they were given forced-air warming. Tympanic temperature was measured as the core temperature. Four adhesive skin-surface probes with thermocouples were fixed on the chest, upper right arm, lateral calf and thigh, and both mean skin and body temperatures were calculated. Fingertip perfusion was evaluated using forearm minus fingertip and calf minus toe skin-surface temperature gradients. Thirty minutes after the intramuscular injection of midazolam, the level of sedation in volunteers was measured by a blinded observer according to the alertness/sedation scale. Results Core temperature significantly decreased by midazolam premedication in a time-dependent manner. Although forced-air warming did not prevent the midazolam-induced transient decrease in core temperature, it increased the temperature to the control level thereafter. Conclusion We conclude that forced-air warming can effectively prevent midazolam-induced redistribution hypothermia.

Vascular prosthetic implantation is associated with prolonged inflammation following aortic aneurysm surgery

The purpose of this study was to semiquantify the magnitude of surgical stress in patients undergoing aortic surgery by measuring inflammatory responses perioperatively, focusing on cytokine secretion. Serum concentrations of interleukin (IL) 1Α, IL-6, IL-8, and tumor necrotizing factor (TNF) Α were measured in patients undergoing abdominal or thoracic aortic aneurysmectomy preoperatively and periodically thereafter for 2 weeks. Urinary trypsin inhibitor (UTI/Cr) and C-reactive protein (CRP) concentration and the systemic inflammatory response syndrome (SIRS) score also were determined. Indices of inflammation and cytokine concentrations peaked at 1–3 days after surgery and decreased thereafter; however, IL-8 increased again after day 7. Concentrations of IL-8, UTI/Cr, and CRP and the SIRS score were still higher 14 days after surgery than preoperatively. The maximum concentrations of IL-6 and IL-8 were higher after thoracic than abdominal aortic repair; however, the maximum values of cytokines were not correlated with operative factors in all patients. A patient suffering from graft infection showed an increase in cytokine concentrations on day 7. The inflammatory response does not return to preoperative values within 2 weeks of surgery in patients undergoing thoracic or abdominal aortic aneurysm repair. The prolonged secretion of IL-8 suggests a host reaction to the synthetic prosthesis. A large increase in inflammatory cytokines on day 7 may indicate infection of the vascular graft.

Isovolaemic haemodilution decreases the shivering threshold in rabbits

Background and objective The inhibition of thermoregulatory control by anaesthesia is manifested by reduced vasoconstriction and shivering thresholds. As intraoperative bleeding can result in haemodynamic changes, including vasoconstriction, we investigated the effect of experimental bleeding on the shivering threshold in rabbits. Methods Twenty‐four rabbits were randomly assigned to one of three treatment strategies: (1) no blood removal (control), (2) 5 mL kg−1 isovolaemic blood removal and (3) 10 mL kg−1 isovolaemic blood removal. After tracheal intubation under isoflurane anaesthesia, anaesthesia was maintained with 50% nitrous oxide in oxygen. The removed blood volume was replaced with the same volume of warm hydroxyethyl starch colloid solution. Oesophageal temperature was measured as a core temperature at 1‐min intervals. After blood removal, the animals body was cooled at a rate of 2–3°C h−1 by perfusing water at 10°C through a U‐shaped thermode positioned in the colon. Hypothermic shivering was evaluated by visual inspection, and the core temperature at which shivering was triggered was identified as the thermoregulatory threshold for this response. Results Just before the cooling, the body temperature of the animals was around 38.6°C in all of the three groups. The shivering threshold in the control group was 37.2 ± 0.2°C (mean ± SD). The shivering thresholds in the 5 mL kg−1 (36.9° ± 0.3°C) and 10 mL kg−1 (36.5° ± 0.5°C) blood removal groups were significantly lower and in proportion with the volume of blood removed than that in the control group. Conclusion Isovolaemic haemodilution decreased the shivering threshold in rabbits in proportion with the volume of blood removed.

Anesthetic Management of a Child With Jeune Syndrome for Tracheotomy: A Case Report.

Jeune syndrome is a rare autosomal-recessive skeletal disorder. Anesthetic management of these patients is often difficult because of thoracic and lung hypoplasia. A 5-month-old boy with Jeune syndrome was scheduled to undergo a tracheotomy. Despite 5-minute preoxygenation with continuous positive airway pressure, the patient’s oxygen saturation rapidly dropped during the induction of anesthesia. The continuous positive airway pressure should have been titrated to effective tidal volume during preoxygenation to recruit the patient’s functional residual capacity and to prevent desaturation. During tracheotomy, volume-controlled ventilation with a high respiratory rate and sufficient inspiratory time effectively improved the patient’s respiratory status.

Intravenous famotidine does not always change core temperature during general anesthesia

It has been reported that oral premedication with the H2 receptor antagonist famotidine augmented intraoperative hypothermia. We again investigated whether the H2 receptor antagonist famotidine significantly affected body temperature during open abdominal surgery under general anesthesia. We studied 20 female patients undergoing elective gynecological surgery. Participating patients were assigned randomly to one of two regimens: (1) 10 ml saline given intravenously just before induction of general anesthesia or (2) 20 mg famotidine in 10 ml saline given just before induction of general anesthesia. General anesthesia was induced by 2 mg·kg−1 propofol and 0.1 mg·kg−1 vecuronium. After tracheal intubation, anesthesia was maintained with sevoflurane (1%–2%) in nitrous oxide (2 l·min−1) and oxygen (1 l·min−1) along with 1–2 μg·kg−1 fentanyl as needed. Tympanic temperature (TTym) was measured as the core temperature, and arteriovenous perfusion of the fingertip was evaluated using the forearmminus-fingertip skin-surface temperature gradient (Grada–f). TTym gradually and significantly decreased in both groups during anesthesia, and no significant differences in these values were observed between the two groups. Grada–f did not differ significantly between the two groups during anesthesia. We conclude that intravenous famotidine does not always change the core temperature during general anesthesia.

Influence of Thermistor Probe Depth from the Anterior Nares on Measurement of Nasopharyngeal Temperature

Nasopharyngeal temperature is allegedly accurate and is generally used during cardiopulmonary bypass for open-heart surgery. However, adequate depth from the anterior nares to measure nasopharyngeal temperature has not been evaluated. To test whether nasopharyngeal temperature is sufficiently accurate and precise for clinical use and to clarify the suitable depth of insertion, we compared nasopharyngeal temperature measurements to simultaneous tympanic temperature measurements during open-heart surgery with cardiopulmonary bypass. Subjects comprised 4 women and 6 men undergoing cardiac surgery with a target core temperature of 32 °C. Nasopharyngeal temperature was measured at 4 sites by placing thermocouples in the nasal cavity in 1-cm increments starting at 2 cm from the anterior nares. The reference temperature (tympanic temperature) was measured at the right tympanic membrane using a thermocouple. Both temperatures were measured every 5 min and compared using correlation coefficients of linear regressi...