Assessment of the potential for pathogen dispersal during high-flow nasal therapy.

High-flow nasal therapy is increasingly used in hospitals because of its effectiveness and patient comfort. However, pathogens in the patient's nasal and oral cavities may be dispersed by forced air. This study aimed to investigate the risk of pathogen dispersal during high-flow nasal therapy. Liquid and bacterial dispersal were assessed via in-vitro experimental set-ups using a manikin. Thickened water or fresh yeast solution mimicked saliva and nasal mucus secretions. Dispersal was limited to the proximal area of the face and nasal cannula, suggesting that high-flow nasal therapy does not increase the risk of droplet and contact infection.

Removal methods of rigid stylets to minimise adverse force and tracheal tube movement: a mathematical and in-vitro analysis in manikins.

This study investigated displacement of the tracheal tube caused by different methods of intubating stylet removal, using in-vitro experiments and mathematical analysis. In the first in-vitro experiment, we measured the distance travelled by the tube tip during stylet extraction. Then, we investigated the ideal technique for stylet extraction using mathematical analysis, which would cause minimal tube displacement. Then, using a training manikin, we measured the force applied to the vocal cords and stylet extraction force during tracheal intubation. When the stylet was extracted along a straight path towards the stylet end, the distance travelled by the tube tip significantly increased as the bending angle increased. Mathematical analysis revealed that the stylet should be diagonally extracted (in the sagittal plane) at an appropriate angle, rather than along a straight path towards the direction of the stylet end. In simulated tracheal intubation, extraction force and force applied to the vocal cords both significantly increased as the bending angle increased. Compared with the 'hockey stick'-shaped stylet, the arcuate-shaped stylet resulted in reduced force. Our results indicate the potential risk for vocal cord injury when using hockey stick-shaped stylets with large bending angles.

The effects of Patent Blue dye on peripheral and cerebral oxyhaemoglobin saturations.

We measured the effect of Patent Blue dye on oxyhaemoglobin saturations after injection into breast tissue: 40 women had anaesthesia for breast surgery maintained with sevoflurane or propofol (20 randomly allocated to each). Saturations were recorded with a digital pulse oximeter, in arterial blood samples and with a cerebral tissue oximeter before dye injection and 10, 20, 30, 40, 50, 60, 75, 90, 105 and 120 min afterwards. Patent Blue did not decrease arterial blood oxyhaemoglobin saturation, but it did reduce mean (SD) digital and cerebral oxyhaemoglobin saturations by 1.1 (1.1) % and 6.8 (7.0) %, p < 0.0001 for both. The falsely reduced oximeter readings persisted for at least 2 h. The mean (SD) intra-operative digital pulse oxyhaemoglobin readings were lower with sevoflurane than propofol, 97.8 (1.2) % and 98.8 (1.0) %, respectively, p < 0.0001.

Large current MOSFET on photonic silicon-on-insulator wafers and its monolithic integration with a thermo-optic 2 × 2 Mach-Zehnder switch.

n-channel body-tied partially depleted metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated for large current applications on a silicon-on-insulator wafer with photonics-oriented specifications. The MOSFET can drive an electrical current as large as 20 mA. We monolithically integrated this MOSFET with a 2 × 2 Mach-Zehnder interferometer optical switch having thermo-optic phase shifters. The static and dynamic performances of the integrated device are experimentally evaluated.

Sevoflurane suppresses tumour necrosis factor-α-induced inflammatory responses in small airway epithelial cells after anoxia/reoxygenation.

BACKGROUND: Lung ischaemia-reperfusion (I/R) injury is correlated with poor clinical outcome. The inflammatory cytokines interleukin (IL)-6, IL-8, and monocyte chemotactic protein-1 (MCP-1) are produced by pulmonary epithelial cells during lung transplantation and are considered to be involved in I/R injury. The volatile anaesthetic sevoflurane has been shown to exert a protective effect on I/R injury in various organs. We investigated the effect of sevoflurane on the inflammatory functions of pulmonary epithelial cells in vitro. METHODS: Human normal small airway epithelial cells (SAEC) were incubated under anoxic conditions for 24 h with or without sevoflurane and then stimulated with tumour necrosis factor (TNF)-α under hyperoxic conditions for 5 h with or without sevoflurane. After incubation, IL-6, IL-8, and MCP-1 mRNA expression was analysed by quantitative real-time RT-PCR. The production of IL-6, IL-8, and MCP-1 was assayed by enzyme-linked immunosorbent assay, the effects of sevoflurane on inflammatory gene expression were examined by DNA microarray analysis, and the effects of sevoflurane on NF-κB-mediated inflammatory cytokine production were examined by immunoblotting. RESULTS: Sevoflurane suppressed TNF-α-induced IL-6, IL-8, and MCP-1 gene expression and the production of IL-6 and IL-8 in SAEC under anoxia/reoxygenation conditions. DNA microarray analysis indicated that sevoflurane modulated NF-κB-related gene expression. Sevoflurane significantly inhibited TNF-α-induced translocation of p65 NF-κB into the nucleus. Sevoflurane enhanced TNF-α-induced gene expression of inhibitor κB (IκB) but not of NF-κB. CONCLUSIONS: Sevoflurane suppressed the NF-κB-mediated production of pulmonary epithelial cell-derived inflammatory cytokines, including IL-6 and IL-8, which are capable of causing I/R injury.

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 degrees C and -0.46 +/- 0.45 degrees 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.

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 animal's body was cooled at a rate of 2-3 degrees C h(-1) by perfusing water at 10 degrees 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 degrees C in all of the three groups. The shivering threshold in the control group was 37.2 +/- 0.2 degrees C (mean +/- SD). The shivering thresholds in the 5 mL kg(-1) (36.9 degrees +/- 0.3 degrees C) and 10 mL kg(-1) (36.5 degrees +/- 0.5 degrees 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.

The use of patient-controlled epidural fentanyl in elderly patients.

We studied whether delivering postoperative analgesia, using a patient-controlled epidural analgesia (PCEA) device was effective and safe in elderly patients. We enrolled 40 patients aged > 65 years (elderly group) and 40 patients aged 20-64 years (young group) scheduled for elective major abdominal surgery. PCEA infusion was started following completion of surgery. Mean (SD) fentanyl consumption (10.7 (3.7) compared with 10.5 (2.7) microg.kg(-1), p = 0.76) and number of times patients pressed the bolus switch (32 (36) compared with 44 (38), p = 0.16) during the first 24 h postoperatively were similar in the two groups. Pain scores, which were similar in both groups at rest, were significantly lower in the elderly on coughing (at 24 h, p < 0.05). In addition, average pain scores were similar at the time of PCEA bolus demands in the two groups. Elderly and young adult patients therefore required similar amounts of patient-controlled epidural fentanyl to produce satisfactory pain relief.

Predictors of atrial fibrillation after off-pump coronary artery bypass graft surgery.

BACKGROUND: Postoperative atrial fibrillation (AF) is one of the most common complications after cardiothoracic surgery and is associated with an increased risk of stroke, and longer hospital stay. The pathophysiology of postoperative AF is uncertain, and its prevention remains unsatisfactory. Many previous studies have examined the predictors of AF after on-pump coronary artery bypass graft surgery (CABG), but there are few reports after off-pump CABG. METHODS: The aim of the present prospective observational study, in which 296 consecutive patients were enrolled, was to elucidate the predictors of AF after off-pump CABG. The association of perioperative factors with AF was investigated using univariate analysis. Significant variables were included into a stepwise logistic regression model to ascertain their independent influence on the occurrence of AF. RESULTS: The incidence of AF was 32%. AF prolonged the time until patients were fit for discharge by 3 days (P<0.01). Stepwise multivariate analysis identified increasing age [odds ratio (OR) 1.44 per 10-yr increase; 95% confidence interval (CI) 1.06-1.95], intraoperative average core temperature (OR 1.64; 95% CI 1.05-2.56), the average cardiac index in the intensive care unit (OR 0.37; 95% CI 0.19-0.71), and intraoperative fluid balance (OR 0.96 per 100-ml increase; 95% CI 0.93-0.99) as independent predictors of postoperative AF. CONCLUSION: Our present findings indicate that ageing, the intraoperative fluid balance, and postoperative cardiac index are associated with the onset of AF after off-pump CABG.

Upregulation of retinal transglutaminase during the axonal elongation stage of goldfish optic nerve regeneration.

Fish CNS neurons can repair their axons following nerve injury, whereas mammalian CNS neurons cannot regenerate, and become apoptotic within 1-2 weeks after the nerve lesion. One explanation for these differences is that one, or several molecules are upregulated in fish CNS neurons during nerve regeneration, and this same molecule is downregulated in mammalian CNS neurons before the development of apoptosis caused by nerve injury. A molecule satisfying these criteria might successfully rescue and repair the mammalian CNS neurons. In this study, we looked for such a candidate molecule from goldfish retinas. Transglutaminase derived from goldfish retina (TG(R)) was characterized as a regenerating molecule after optic nerve injury. A full-length cDNA for TG(R) was isolated from the goldfish retinal cDNA library prepared from axotomized retinas. Levels of TG(R) mRNA and protein increased only in the retinal ganglion cells (RGCs) between 10 and 40 days after optic nerve transection. Recombinant TG(R) protein enhanced neurite outgrowth from adult fish RGCs in culture. Specific interference RNA and antibodies for TG(R) inhibited neurite outgrowth both in vitro and in vivo. In contrast, the level of TG(R) protein decreased in rat RGCs within 1-3 days after nerve injury. Furthermore, the addition of recombinant TG(R) to retinal cultures induced striking neurite outgrowth from adult rat RGCs. These molecular and cellular data strongly suggest that TG(R) promotes axonal elongation at the surface of injured RGCs after optic nerve injury.

Is the ARX index a more sensitive indicator of anesthetic depth than the bispectral index during sevoflurane/nitrous oxide anesthesia?

BACKGROUND: During general anesthesia, hypnotic components have been monitored with electroencephalogram. The bispectral index is derived from a cortical electroencephalogram, but the A-line ARX index is the electroencephalographic response to auditory stimuli. The purpose of this study was to compare the changes of the A-line ARX index and the bispectral index during sevoflurane - nitrous oxide anesthesia. METHODS: One hundred females aged 30-60 years, and scheduled for partial mastectomy, were divided into two groups. Anesthesia was induced with sevoflurane 5% and nitrous oxide in oxygen for 3 min. A laryngeal mask airway was inserted, and anesthesia was maintained with sevoflurane 1-2% and nitrous oxide in oxygen. During surgery, the sevoflurane end-tidal concentration was kept at 0.5%, 1%, or 2% for 5 min before each measurement. Blood pressure, heart rate, and the A-line ARX index (n = 50), and the bispectral index (n = 50) were measured. RESULTS: Blood pressure and heart rate increased following laryngeal mask airway insertion and blood pressure decreased at 2% sevoflurane in both groups similarly. The A-line ARX index, but not the bispectral index, increased significantly by laryngeal mask airway insertion and skin incision. The A-line ARX index decreased at 2% sevoflurane compared with 0.5%, while the bispectral index remained unchanged. CONCLUSION: During sevoflurane-nitrous oxide anesthesia, the A-line ARX index might be a more sensitive indicator of anesthetic depth than the bispectral index.

The vasoconstriction threshold is increased in obese patients during general anaesthesia.

BACKGROUND: In anaesthetized patients, body temperature decreases often, but overweight patients become less hypothermic. Obesity in itself protects body heat, and thermoregulatory reflexes may maintain normothermia in obese patients. We tested the hypothesis that even slight obesity increases the vasoconstriction threshold. METHODS: Twenty male patients aged 30-65 years scheduled for open abdominal surgery were allocated to two groups: body fat >/=25% (obese group, n = 10), or <25% (normal weight group, n = 10). Anaesthesia was maintained with 0.4% isoflurane and opioid. The thermoregulatory vasoconstriction threshold was defined by the tympanic membrane temperature at which the skin temperature gradient equalled 0 degrees C. Plasma adrenaline, noradrenaline and leptin were measured. RESULTS: Age, height, heart rate and blood pressure did not differ between the two groups of patients. In the obese group the vasoconstriction threshold was higher than that in the normal weight group: 36.0 +/- 0.1 vs. 35.5 +/- 0.2 degrees C. Consequently, after 4 h of anaesthesia, the core temperature was highest in the obese patients: 36.4 +/- 0.1 vs. 35.5 +/- 0.2 degrees C. CONCLUSIONS: These results suggest that core temperature is maintained in obese patients because their vasoconstriction threshold to a low environmental temperature is high.

Warming by resistive heating maintains perioperative normothermia as well as forced air heating.

BACKGROUND: Even mild perioperative hypothermia is associated with several severe adverse effects. Resistive heating has possible advantages compared with other active warming systems because it can heat several fields independently. To assess this new warming system, we measured core temperature in patients during surgery who were warmed with circulating water mattresses, forced air covers or resistive heating covers. METHODS: Twenty-four patients undergoing laparoscopic cholecystectomy were randomly assigned to (i) circulating water mattress (38 degrees C), (ii) forced air warming (set to 'medium') or (iii) carbon-fibre resistive warming (38 degrees C). Warming was applied throughout anaesthesia and surgery. The groups were compared using one-way ANOVA and Student-Newman-Keuls tests. RESULTS: Confounding factors were similar among the groups. Core temperatures in each group decreased for 20 min, but subsequently increased in the forced air and resistive heating groups. There was no significant difference between the forced air and resistive heating groups at any time. In contrast, core temperature in the circulating water group continued to decrease. Consequently, core temperature in the circulating water group was significantly lower than in the other groups 30 min after anaesthetic induction and at later times. CONCLUSIONS: Resistive heating maintains core body temperature as well as forced air heating and both are better than circulating water. Resistive heating offers the advantage of adjustable heating pods.

Preoperative blood pressure and catecholamines related to hypothermia during general anesthesia.

BACKGROUND: We previously demonstrated that preoperative blood pressure values affect intraoperative hypothermia during general anesthesia. We hypothesized that increased catecholamine secretion could be responsible for the relationship between preoperative blood pressure and hypothermia. METHODS: To evaluate the effect of preoperative systolic blood pressure (SBP) and plasma catecholamine levels on core temperature during general anesthesia, 40 male patients who were scheduled for open abdominal surgery were allocated to two groups: those whose preoperative SBP was 140 mmHg or greater (high SBP group, n = 20), and those whose SBP was less than 140 mmHg (normal SBP group, n = 20). Anesthesia was maintained with 0.4% isoflurane and opioids. RESULTS: The average age, height, and weight of the patients in the two groups did not differ. Preoperative SBP, mean blood pressure, diastolic blood pressure and heart rate in the high SBP group were significantly higher than those in the normal SBP group. Plasma norepinephrine concentrations in the high SBP group were significantly greater than those in the normal SBP group before and 1 h after the induction of anesthesia. Tympanic membrane temperatures in the normal SBP group started to decline further just after the induction of anesthesia, more so than that in the high SBP group. The vasoconstriction threshold in the normal SBP group was significantly lower than that in the high SBP group. CONCLUSION: These results suggest that the higher levels of preoperative catecholamine secretion contributed to the lesser degree of intraoperative hypothermia observed in the high SBP group.

Effect of preoperative amino acid infusion on thermoregulatory response during spinal anaesthesia.

BACKGROUND: Intravenous amino acid infusion during general anaesthesia prevents decreases in core temperature resulting from increased energy expenditure and heat accumulation. METHODS: We investigated whether such stimulation also occurs during spinal anaesthesia, which blocks sympathetic nervous activity. We examined the effect of i.v. amino acid infusion on changes in core temperature during spinal anaesthesia. Thirty-five patients were divided into two groups: an i.v. amino acid infusion group (4 kJ kg(-1) h(-1) starting 2 h before surgery); and a saline infusion group. Tympanic membrane core temperature, forearm-fingertip temperature gradient (an index of peripheral vasoconstriction) and mean skin temperature were measured for 90 min after the onset of spinal anaesthesia. RESULTS: Changes in mean arterial pressure and heart rate did not differ significantly between the groups during the study period. Mean final core temperature 90 min after induction of spinal anaesthesia was 35.8 (SEM 0.1) degrees C in the saline group and 36.6 (0.1) degrees C in the amino acid group (P<0.05). The increased level of oxygen consumption in the amino acid group compared with the saline group was preserved even after the onset of spinal anaesthesia. The thermal vasoconstriction threshold, defined as the tympanic membrane temperature that triggered a rapid increase in forearm-fingertip temperature gradient, was increased in the amino acid group [36.8 (0.1) degrees C] compared with the saline group [36.5 (0.1) degrees C] (P<0.05). CONCLUSIONS: Preoperative infusion of amino acids effectively prevents spinal anaesthesia-induced hypothermia by maintaining a higher metabolic rate and increasing the threshold core temperature for thermal vasoconstriction.

Nitrous oxide decreases shivering threshold in rabbits less than isoflurane.

BACKGROUND: Comparable minimum alveolar concentration (MAC) fractions of volatile anaesthetics produce similar thermoregulatory impairment. Nitrous oxide, however, decreases the vasoconstriction threshold less than sevoflurane or isoflurane. We tested the hypothesis that nitrous oxide also decreases shivering threshold less than isoflurane alone or in combination. METHODS: Twenty-four rabbits were assigned randomly to one of three 0.3 MAC anaesthetic regimens: (i) nitrous oxide 69%; (ii) nitrous oxide 35% and isoflurane 0.3%; or (iii) isoflurane 0.6%. Body temperature was lowered by perfusing 10 degrees C water through a U-shaped thermode positioned in the colon. Shivering was evaluated by inspection. RESULTS: The rabbits anaesthetized with nitrous oxide alone shivered at 37.0 (0.5) degrees C (P<0.01 vs other groups). In those given the nitrous oxide and isoflurane combination, the shivering threshold was 36.4 (0.5) degrees C and that in the isoflurane group was 35.9 (0.4) degrees C. CONCLUSION: This study indicates that nitrous oxide reduces the shivering threshold less than isoflurane.