Improved PCO 2 monitoring during high frequency jet ventilation

During high frequency jet ventilation (HFJV), it has been shown that Pa_{CO 2} can be predicted by capnography when the frequency was temporarily reduced to obtain a steady expiratory CO₂ tension (Pet _{CO 2}). The influence of the sampling site of expiratory gas in the airway and the driving pressure of the ventilator on the difference between Pa_{CO 2} and Pet _{CO 2} was investigated in ten adult patients who underwent general anesthesia. During HFJV (frequency: 100bpm, inspiratory duty cycle; 30%), its frequency was temporarily reduced to 10bpm in twelve different condition; i.e., 3 different driving pressures (Pd; 20, 30, and 40psi) at 4 different sampling sites (d; 0, 2, 5, and 10cm in the endotracheal tube). Both Pet _{CO 2} and Pa_{CO 2} were measured simultaneously, and their difference was evaluated by using Students t-test. The difference between Pa_{CO 2} and Pmax_{CO 2} (the maximum P_{CO 2} value in the airway during exhalation) was minimal, when Pd was greater than 30psi, and d was greater than 5cm. The present study suggests that better prediction of Pa_{CO 2} can be done by Pet _{CO 2} during HFJV, when d and Pd were set as large as possible to obtain stable expiratory P_{CO 2} curve.(Kotani T, Ochiai R, Takeda J, et al.: Imploved P_{CO 2} monitoring during high frequency jet ventilation. J Anesth 6: 75–79, 1992)     

Hemodynamic effects of high-frequency jet ventilation in dogs with acute right coronary arterial ligation and pulmonary arterial banding

The hemodynamic effects of high-frequency jet ventilation (HFJV), synchronized with diastole, and intermittent positive-pressure ventilation (IPPV) were studied in 10 dogs with acute right-sided myocardial ischemia and elevated right ventricular pressure. Myocardial ischemia was produced by ligation of the proximal right coronary artery (RCA), then the right ventricular pressure was elevated to facilitate the ischemia by banding the main pulmonary artery. Before and 1, 2, 3, and 5hr after the RCA ligation, cardiorespiratory variables for each ventilatory mode and creatine phosphokinase MB isoenzyme (CPK-MB) were measured. During HFJV compared with IPPV: there were significant increases in stroke index and left ventricular stroke work index at all ischemic periods, and decreases in peak and mean airway pressures and pulmonary vascular resistance at all ischemic periods, and in the product of systolic right ventricular pressure and heart rate at 2hr, 3hr, and 5hr. The difference in mean airway pressure between IPPV and HFJV correlated significantly with those in cardiac index and stroke index (r = 0.575 and 0.779, respectively). CPK-MB was significantly greater at 3hr and 5hr than that before RCA ligation. These findings suggest that HFJV synchronized with diastole offers hemodynamic advantages over IPPV to ischemic right ventricle with constricted pulmonary artery, mainly due to lowering the mean airway pressure.(Ushijima K, Oka Y, Weinberg P et al.: Hemodynamic effects of high-frequency jet ventilation in dogs with acute right coronary arterial ligation and pulmonary arterial banding. J Anesth 4: 232–241, 1990)     

Regulation of mineral-to-matrix ratio of lumbar trabecular bone in ovariectomized rats treated with risedronate in combination with or without vitamin K<Subscript>2</Subscript>

The relationship between bone turnover and bone tissue and material properties was examined in ovariectomized (OVX) rats treated with risedronate in combination with or without vitamin K₂. Seventy female rats, 18 weeks of age, were assigned to 7 groups (n = 10): sham-operated + vehicle control; OVX + vehicle control; OVX + risedronate 0.1, 0.5, or 2.5mg/kg/day po; OVX + vitamin K₂ 30mg/kg/day po; OVX + vitamin K₂ (30mg/kg/day) and risedronate (0.5mg/kg/day). Treatments were given daily for 9 months. To assess bone turnover, we measured serum osteocalcin and urinary deoxypyridinoline at 0, 3, and 9 months. To assess vertebral and femoral tissue and material properties, bone mass, bone mineral density (BMD by DXA), trabecular bone structure (vertebra: 3D-CT), cortical bone structure (femur: histomorphometry), biomechanical properties, and mineral properties (mineral-to-matrix and carbonate-to-phosphate ratios by Fourier transform infrared microspectroscopy) were measured ex vivo at 9 months. Ovariectomy increased bone turnover and induced significant loss of bone mass/density, structure, mineral properties (mineral-to-matrix ratio), and strength. Risedronate produced dose-dependent inhibition of the ovariectomy-induced increase in turnover and loss of bone mass/density, structure, mineral-to-matrix ratio, and strength, with a lowest effective dose of 0.1–0.5mg/kg/day. High-dose risedronate (2.5mg/kg/day) did not induce increases in any parameter above that of sham control. Vitamin K₂ had no effects. In the OVX groups, urinary deoxypyridinoline at 3 and 9 months correlated significantly with vertebral BMD, trabecular bone volume, ultimate load, stiffness, and mineral-to-matrix ratio, and with femoral BMD, cortical area, and ultimate load. These results support the concept that changes in bone tissue and material properties can result directly from changes in bone turnover. Different effects among different drugs on material properties, including mineral-to-matrix ratio, may reflect differences in the relative rate and magnitude of osteoclastic bone resorption and osteoblastic primary bone mineralization.     

Changes in respiratory pattern during continuous positive airway pressure in infants after cardiac surgery

Purpose Spontaneous breathing trials are commonly used in adults to enable smooth weaning from mechanical ventilation. However, few investigations have examined spontaneous breathing tests in infants. We investigated how respiratory patterns of infants changed during continuous positive airway pressure (CPAP) and whether successful extubation followed CPAP.Methods Fifty-one consecutive post—cardiac surgery infants satisfied the following weaning criteria: stable hemodynamics, pH > 7.30, tidal volume > 5ml·kg^–1, and respiratory rate < 50 breaths·min^–1 with pressure control of 10–16cm H₂O. We applied CPAP of 3cm H₂O for 30min to these 51 infants. During CPAP, tidal volume, respiratory rate, and arterial blood gases were measured. CPAP was terminated if the patient showed a sustained increase or decrease in heart rate or blood pressure (>20%), a decrease in arterial oxygen saturation (>5%), agitation, or diaphoresis. After the completion of CPAP, tracheal extubation was performed. We considered extubation successful if no reintubation was required in the ensuing 48h.Results Although hemodynamic and ventilatory variables were unstable for the first 5min, they stabilized after 10min of CPAP. Fifty infants completed the CPAP trial safely. Of these, 46 (92%) underwent successful extubation after the CPAP trial. The failure group (4 infants) showed lower pH, higher arterial carbon dioxide tension, and more rapid shallow breathing during CPAP than the success group.Conclusion After cardiac surgery, when infants recovered stable hemodynamics and spontaneous breathing, the ventilatory pattern and hemodynamics became stable after 10min of CPAP. Ninety-two percent of the patients were successfully extubated following a 30-min CPAP trial.     

Comparison of anesthetic effects of epidural and intravenous administration of buprenorphine during operation

Thirty six patients were received epidural anesthesia with or without buprenorphine (BPN) during upper abdominal surgery. They were divided into three groups of 12 patients as follows; G-I received 20ml of 1% lidocaine epidurally, G-II received 20ml of 1% lidocaine epidurally and 0.6mg BPN intravenously, G-III received 20ml of 1% lidocaine with 0.6mg BPN epidurally. Additional 5ml of 1% lidocaine was given to any patient if systolic blood pressure or heart rate increased 10% compared to control value. Trachea was intubated following anesthetic induction with thiopental. The lungs were ventilated with a mixture of N₂O/O₂ (33%) and pancuronium was used for muscle relaxation. The total required doses of lidocaine in G-II and G-III were decreased 60% compared to control group (G-I) (P 0.05). The mean period of time until the first administration of pentazocine for postoperative pain was 13 ± 10hr (mean ± SD) in G-II and 19 ± 24hr in G-III compared to 5 ± 4hr in G-I (P 0.001). The dose of the administration of pentazocine that was required for pain relief during the first 48 postoperative hr in G-III was 54 ± 10mg (mean ± SD) compared to 150 ± 21mg in G-I (P 0.02) and 106 ± 28mg in G-II (P 0.05). Recovery from anesthesia in G-III was more rapid than that in G-I (P 0.05). The Pa_{CO 2} values in G-II and G-III increased 15% compared to control group at about 4hr and 8hr after administration of BPN, but any clinical treatment was not needed for them. Nonrespiratory side effects, e.g., nausea, vomiting, fatigue and headache, were comparably common in all groups. Mild hematuria associated with acute hypotension occurred in two patients in G-II (17%) immediately after the intravenous injection of 0.6mg of BPN. The results showed that 0.6mg of BPN given epidurally demonstrated better anesthetic and more potent postoperative analgesic effects and lesser side effects than 0.6mg of BPN given intravenously in patients undergoing upper abdominal surgery.(Yonemura E, Fukushima K.: Comparison of anesthetic effects of epidural and intravenous administration of buprenorphine during operation. J Anesth 4: 242–248, 1990)     

Prostaglandin E1 (PGE1) attenuates vasoconstriction induced by PGE2, PGD2 and phorbol myristate acetate in the perfused rat liver

It has been shown that prostaglandins (PGs) produced by Kupffer and endothelial cells play an important role in mediating physiological responses to various immunological stimuli. We studied the effect of prostaglandin E₁ (PGE₁) on the hemodynamic and metabolic changes induced by prostaglandin E₂ (PGE₂), D₂ (PGD₂) and phorbol 12-myristate 13-acetate (PMA), a potent inducer of PGs in the isolated rat liver perfused with Krebs-Ringer-bicarbonate (KRB) solution at a constant pressure of 12cmH₂O. The liver was taken from overnight-fasted male Sprague-Dawley rats weighing 260 to 310g. Both PGE₂ and PGD₂ significantly decreased hepatic flow when their initial concentration was elevated to micromolar range. Although 1 × 10^–6M of PGE₁ did not have a major effect on hepatic flow, it significantly attenuated the declines of hepatic flow produced by 4 × 10^–6M of PGE₂ and PGD₂. However, none of PGs tested influenced glucose and lactate concentrations in the medium. Continuous infusion of PGE₁ into the medium at a rate of 5µg·min^–1 significantly diminished the decreases in hepatic flow and oxygen consumption induced by 2 × 10^–8M of PMA. These results suggest that administration of PGE₁ may preserve hepatic blood flow by modifying the intrahepatic regulatory mechanism involving the activation of Kupffer and endothelial cells.(Inaba H, Araki M, Numai T, et al.: Prostaglandin E₁ (PGE₁) attenuates vasoconstriction induced by PGE₂, PGD₂ and phorbol myristate acetate in the perfused rat liver. J Anesth 7: 56–65, 1993)     

Oedema formation in experimental photo-irradiation therapy of brain tumours using 5-ALA

Summary Background. Five-aminolevulinic acid (5-ALA) induces the specific accumulation of photosensitising porphyrins in malignant gliomas and has been explored for photo-irradiation therapy of these tumours. However, information is unavailable on whether and to what extent this treatment modality may induce the formation of brain oedema, and how potential oedema might be treated.Methods. Rats were implanted with C6 gliomas. Eight days later magnetic resonance images (MRI) were obtained. On day 9 rats received 100mg 5-ALA/kg b.w. and were craniotomized for photo-irradiation of tumours 6 hours later (100J/cm², 635nm argon-dye laser). Part of the animals was treated with daily dexamethasone injections (0.3mg/kg), beginning 6 hours before phototherapy. 72 hours later, brains were removed and dissected according to tumour dimensions on pre-therapy MRI into tumour, brain around tumour (BAT), residual cortex and basal ganglia, for measurements of water contents. Measurements were also performed in untreated animals with tumours, with or without steroid treatment and in control animals. An additional group of animals lacking tumours, with or without steroid treatment, underwent 5-ALA-phototherapy to determine effects on normal brain.Results. C6 gliomas induced brain oedema, which responded to steroid treatment. 5-ALA-phototherapy resulted in additional oedema, which responded partly to steroids. 5-ALA-phototherapy of normal brain increased water content moderately in irradiated cortex. This oedema was also partly counteracted by steroids.Conclusions. Photo-irradiation therapy with 5-ALA induces oedema which is partly counteracted by steroid therapy. The possibility of steroid resistant oedema formation should be considered when planning human trials with this treatment modality.     

Correlation of continuously monitored regional cerebral blood flow and brain tissue oxygen

Summary Background. The purpose of this study was to investigate the relationship between continuously monitored regional cerebral blood flow (CBF) and brain tissue oxygen (P_tiO₂).Methods. Continuous advanced multimodal neuromonitoring including monitoring of P_tiO₂ (Licox, GMS) and CBF (QFlow, Hemedex) was performed in eight patients after severe subarachnoid haemorrhage (n=5) and traumatic brain injury (n=3) for an average of 9.6 days. Parameters were measured using a flexible polarographic P_tiO₂-probe and a thermal diffusion CBF-microprobe.Findings. Regarding the whole monitoring period in all patients, the data indicated a significant correlation between CBF and P_tiO₂ (r=0.36). In 72% of 400 analysed intervals of 30 minutes duration with P_tiO₂ changes larger than 5mmHg, a strong correlation between CBF and P_tiO₂ existed (r>0.6). In 19% of intervals a still statistically significant correlation was observed (0.3<r<0.6). During the remaining 9% no correlation was found (r<0.3). Regarding the clinical stability of the monitoring devices, the CBF monitoring system allowed monitoring of CBF in 64% of the time when P_tiO₂ monitoring was possible only. Phases of non-monitoring were mostly due to fever of the patient, when the system does not allow monitoring to avoid overheating of the cerebral tissue.Conclusions. This study suggests a correlation between CBF and P_tiO₂. The level of P_tiO₂ seems to be predominately determined by regional CBF, since changes in P_tiO₂ were correlated in 90% of episodes to simultaneous changes of CBF.     

Laryngeal mask airway can be inserted with inhaled desflurane induction

Purpose In this prospective, randomized, controlled trial, we investigated the reliability of laryngeal mask airway (LMA) insertion with inhaled desflurane.Methods Eighty patients undergoing elective surgery were randomized into two groups to receive either 2.5mg·kg^–1 propofol (n = 40) or tidal breath desflurane (n = 40) induction followed by LMA insertion. All patients received fentanyl 1µg·kg^–1 2min before induction. Inhalation of desflurane was started at 3% and increased by 3% every 3–5 breaths up to settings of 12%.Results Insertion of the LMA was faster in the propofol group (131.8s versus 228.6s, P < 0.01). The number of patients in whom the jaw opening was described as good (95% versus 72.5%, P = 0.27, for the desflurane and propofol groups, respectively) and the ease of LMA insertion described as good (87.5% versus 72.5%, P = 0.6) were comparable. The LMA was inserted in a single attempt in the majority of patients in both groups (80% versus 77.5%, P = 0.90). There were more complications at insertion in the propofol group than in the desflurane group (2.5% versus 19.5%, P < 0.01), especially for apnea (7.5% versus 70%, P < 0.01) and excitatory movements (2.5% versus 25%, P < 0.01). There were significant decreases in the mean arterial pressure in the propofol group compared to baseline data over the first 5min of induction. Mean arterial pressure, heart rate, and S_{p O 2} remained stable during the same period in the desflurane group.Conclusion We demonstrated that inhaled desflurane when used with caution in a controlled manner provided acceptable conditions for LMA insertion.     

Treatment outcomes and mortality of 94 patients with acromegaly

Summary Background. Due to new therapeutic modalities and modified therapeutic goals outcome of patients with acromegaly may change over time and differ by centre. We analysed treatment outcomes and mortality of our patients with acromegaly seen between 1971 and 2003.Method. The cohort consisted of 94 patients who had been followed for 0.3–31 years (mean 10.6 years). Remission criteria were a normalized IGF-I concentration, a nadir GH level during oral glucose load of <1.0µg/l and a random GH value of <2.5µg/l.Findings. Transsphenoidal surgery achieved remission in 80% of patients with micro-adenomas (<1cm), 65% with meso-adenomas (1cm to <2cm) and 27% with macro-adenomas (2cm). Patients with meso-adenomas operated on after 1995 tended to have a better outcome compared to those operated on before 1995 (Remission in 83% vs. 38%). Radiotherapy resulted in disease control in 22 of 47 patients (47%). Intramuscular depot formulation of octreotide (Sandostatin^® LAR^®) led to disease control in 17 of 26 patients (65%). After multimodal therapy persistent acromegalic activity remained in 18% of the patients; only one of them had an adenoma of <2cm. The standardized mortality ratio was 1.30 (95% CI 0.52–2.67) for patients in remission and 1.38 (95% CI 0.51–3.00) for patients with persistent acromegalic activity.Conclusions. Most patients with adenomas of <2cm can be expected to achieve remission by transsphenoidal surgery alone. Furthermore, virtually all patients with adenomas of <2cm and more than 80% of patients with adenomas of 2cm can be expected to achieve remission by adjuvant treatment. Aggressive multimodal therapy is critical in the management of acromegaly reducing mortality risk close to that of the general population.     

Real-time integration of ultrasound into neuronavigation: technical accuracy using a light-emitting-diode-based navigation system

Summary. Background. In brain surgery, intraoperative brain deformation is the major source of postimaging inaccuracy of neuronavigation. For intraoperative imaging of brain deformation, we developed a platform for the integration of ultrasound imaging into a navigation system.Method. A commercially available ultrasound system was linked to a light-emitting-diode- (LED) based neuronavigation system via rigid fixation of a position localiser to the ultrasound probe and ultrasound image transfer into the navigation system via a S-VHS port. Since the position of the ultrasound image co-ordinate system is not readily defined within the navigation reference co-ordinate system (REF CS), a transformation which links both co-ordinate systems has to be defined by a calibration procedure. Calibration of the ultrasound probe within the REF CS was performed via a cross-wire phantom. The phantom target was defined within the navigation co-ordinate system (by pointer under microscopic control) and imaged by ultrasound. Ultrasound presets were optimised (digital beam focusing, gain intensity) to attain a small echoic target for manual target definition. The transformation was derived from 150 ultrasound measures and iteration. Accuracy was calculated as mean linear error (LE; in X_REF, Y_REF, or Z_REF direction), overall mean LE (linear errors of all axes X_REF to Z_REF) and Euclidean error (EE; vectorial distance from the physical target).Findings. Optimised ultrasound presets (8MHz frequency, digital beam focusing, 20% gain intensity) enabled a low interobserver error (mean: 0.5mm, SD: 0.28) for target definition within the 2-D ultrasound image. Mean accuracy of pointer-based physical target definition in the REF CS was 0.7mm (RMSE; SD: 0.23mm). For navigated ultrasound, the overall mean LE was 0.43mm (SD: 1.36mm; 95%CL: 3.13mm) with a mean EE of 2.26mm (SD: 0.97mm; 95%CL: 4.21mm).Interpretation. Using a single target cross-wire phantom, a highly accurate integration of ultrasound imaging into neuronavigation was achieved. The phantom accuracy of integration lies within the range of application accuracy of navigation systems and warrants clinical studies.     

Modification of hepatic protein kinase C with phorbol myristate acetate and staurosporine alters hemodynamics in the perfused rat liver

Activation of protein kinase C (PKC) has been implicated in the pathogenesis of endotoxicosis and severe sepsis. Since hepatic blood flow and metabolism have been known to be altered in endotoxicosis and sepsis, we studied the hemodynamic effect of PKC modulation with phorbol 12-myristate 13-acetate (PMA) and staurosporine (St) on the perfused rat liver. The liver was isolated from overnight-fasted male Sprague-Dawley rats and placed in a recirculating perfusion apparatus. The liver was perfused with Krebs-Ringer-bicarbonate solution at a constant pressure of 12cmH₂O. Flow to the liver was continuously monitored with an electric magnetic flowmeter. PMA at an initial concentration of 2 × 10^–8M significantly decreased hepatic flow. Staurosporine (St), a potent PKC inhibitor at 4 × 10^–7M produced a small increase in hepatic flow. Pretreatment with St significantly attenuated the flow reduction by PMA. St significantly suppressed the flow reductions by 4 × 10^–6M of prostaglandin E₂ and D₂. These results suggest that the PKC inside the liver may play an important role in the regulation of hepatic blood flow during endotoxicosis and sepsis.(Inaba H, Araki M, Numai T, et al.: Modification of hepatic protein kinase C with phorbol myristate acetate and staurosporine alters hemodynamics in the perfused rat liver. J Anesth 7: 48–55, 1993)     

Breathing pattern and respiratory mechanics in sevoflurane-anesthetized humans

In order to determine the respiratory effects of sevoflurane in humans, breathing pattern and mechanical behavior of respiratory system were investigated in ten subjects at anesthetic depth of 1MAC (minimum alveolar concentration). Average tidal volume and breathing frequency amounted to 275ml and 20.9 breaths per minute. Arterial carbon dioxide tension amounted to 45.6mmHg. Duration of inspiration was 1.06s and that of expiration was 1.92s. Mean inspiratory flow rate amounted to 259ml·s^–1. Average value of passive respiratory elastance determined by the method of Zin et al. amounted to 21.8cmH₂O·l ^–1, while those of active respiratory elastance and resistance obtained by the method of Behrakis et al. were 28.0cmH₂O·l ^–1 and 3.15cmH₂O·l ^–1·s^–1, respectively.Values of these variables were compared to those reported in halothane and enflurane anesthesia and possible explanations of the differences between the anesthetics are discussed.(Izumi Y, Kochi T, Isono S, et al.: Breathing pattern and respiratory mechanics in sevoflurane-anesthetized humans. J Anesth 4: 343–349, 1990)     

Multiple endocrine neoplasia type 1 in end-stage renal failure

A 59-year-old woman with chronic renal failure due to type 2 diabetes mellitus (DM) is presented. Her father and a brother had a history of brain tumor. Her blood urea nitrogen and serum creatinine levels were 102mg/dl and 4.5mg/dl, respectively. Her serum Ca²⁺ and Pi were within the normal range (9.4mg/dl and 5.4mg/dl, respectively). Her intact parathyroid hormone (PTH) level was 1730000pg/ml. A ^99mTc-methoxy-isobutylisonitrile scintigraphy showed high uptake in three parathyroid glands. A magnetic resonance image showed microadenoma in the pituitary gland. The serum gastrin level was high. Genetic examination revealed a mutation of the MEN1 gene (894–9 G A). From these findings, she was diagnosed with multiple endocrine neoplasia (MEN) type 1. Subsequently, a parathyroidectomy was performed successfully, a parathyroid gland was transplanted to her right forearm, and her serum Ca²⁺ level was controlled at 8.5–9.0mg/dl. It is very important to identify MEN1 if an end-stage renal disease (ESRD) patient has hyperparathyroidism with multigland involvement. Examination of the MEN1 gene may be valuable to make an accurate diagnosis and choose the appropriate therapy in some ESRD patients with hyperparathyroidism.     

Cardiovascular interaction between sevoflurane and nicardipine in open chest dogs

Cardiovascular interaction between nicardipine and sevoflurane was examined in dogs and compared with nicardipine-thiopental interaction and nicardipine-halothane interaction. The bolus intravenous injection of nicardipine at dosages of 15µg/kg and 30µg/kg under sevoflurane anesthesia produced transient decreases in blood pressure, systemic vascular resistance, left ventricular pressure, left ventricular ^dp/_dt and –^dp/_dt, and a slight increase in cardiac output. The degrees of these changes were almost identical to those under thiopental or halothane anesthesia. Left and right atrial pressure, pulmonary arterial pressure, pulmonary vascular resistance were not changed by nicardipine under any of the three anesthetics. These results suggest that the cardiovascular interaction of nicardipine and sevoflurane is additive and similar to that of nicardipine and halothane and that the cardiovascular changes induced by nicardipine are not modified by the presence of anesthetics.(Iwatsuki N, Kaise A, Koga Y et al.: Cardiovascular interaction between sevoflurane and nicardipine in open chest dogs. J Anesth 2: 146–153, 1988)     

Changes of local brain tissue oxygen pressure after vasopressin during spontaneous circulation

Summary. Background. Brain tissue oxygen pressure (PbtO₂) correlates to cerebral blood flow (CBF) during spontaneous circulation, with one important regulator being nitric oxide (NO). Although it is established that arginine vasopressin (AVP) improves CBF and global cerebral oxygenation during cardiopulmonary resuscitation, it is unknown whether similar beneficial effects are present during spontaneous circulation. The purpose of this study was to investigate the effects of AVP with and without pre-treatment with the NO synthase inhibitor N-omega-nitro-L-arginine methyl ester (L-NAME) on local brain tissue oxygenation in a beating heart model.Methods. Following approval of the Animal Investigational Committee, nine healthy piglets underwent general anaesthesia, and were instrumented with a probe in the cerebral cortex to measure PbtO₂. Each animal was assigned to receive AVP (0.4U·kg^–1), and after a wash-out period, L-NAME (25mg·kg^–1 over 20min) followed by AVP (0.4U·kg^–1). After each AVP administration, nitroglycerine (25µg·kg^–1 over 1min) as a NO donor was infused to test the vascular reactivity independently from NOS inhibition.Findings. Three minutes after administration of AVP, PbtO₂ increased significantly (P<.05; mean±SEM, 31±11 versus 43±14mmHg, +39%), compared with baseline. After pre-treatment with L-NAME, the changes of PbtO₂ after AVP were not significant (32±11 versus 28±10, –13%) when compared with the baseline.Conclusion. In this beating heart porcine model, local brain tissue oxygenation was improved after AVP alone, but not after inhibition of NO synthesis with L-NAME.     

Bench test assessment of the new Raumedic Neurovent-P ICP sensor: a technical report by the BrainIT group

Summary. Background. In clinical practice, fiberberoptic and piezo-electric ICP probes are often used for measuring intracranial pressure (ICP). A number of similar technologies, although performing well in bench test studies, have been shown to exhibit unacceptable zero drift, fragility or both during trials conducted under clinical conditions. Recently, a new technology has become available, the Neurovent-P (Raumedic AG+CO, Raumedic, Germany). As a pre-requisite for a clinical trial, we have conducted and report on bench test studies to confirm the manufacturers long term zero-drift performance for this technology.Method. In a test rig static tests (recording of 20mmHg pressure) and dynamic tests, ranging from 5 to 50mmHg have been performed.Findings. 10 ICP probes have been tested for a total of 60 days. All the catheters, after the connection with the ICU monitor displayed a static pressure of 0±1mmHg and did not required pre-insertion alteration. At five days, mean zero drift was 0.6±0.9mmHg. Overall, zero drift ranged from 0 to 2mmHg. At a fixed static pressure of 20mmHg, the mean recorded value was 20.6±0.8mmHg, ranging from 19 to 23mmHg. A regression analysis of the relationship between the applied pressure and the recorded pressure during the dynamic tests of the 10 catheters yielded a correlation coefficient R² of 0.997. Applying the Altman and Bland method to assess the bias and confidence limits for the Raumedic catheter responses during the dynamic tests against the applied gold-standard hydrostatic column pressures, the average bias of –0.66±0.85mmHg, with 95% CLs of –2mmHg and 1mmHg.Conclusions. Mean zero drift, after five days, was very small and long-term continuous recording of a stable pressure was very precise. The response at dynamic tests, i.e. the changes of pressure in a wide range, was excellent. The average bias of the Raumedic catheter compared with the hydrostatic column is very small. After this bench test, the next and most critical step will be to conduct a trial of this promising technology under more demanding clinical environment.     

Dose-finding study of intravenous midazolam for sedation and amnesia during spinal anesthesia in patients premedicated with intramuscular midazolam

Purpose We investigated the effective and safe dose of intravenous midazolam for sedation and amnesia during spinal anesthesia in patients premedicated with intramuscular midazolam.Methods One hundred and eighty patients aged 20–50 years scheduled for spinal anesthesia received midazolam 0.06mg·kg^–1 and atropine 0.01mg·kg^–1 intramuscularly 15min before entering the operating room. Spinal anesthesia was performed with 0.5% hyperbaric tetracaine. Five minutes after starting surgery, midazolam 0 (control group), 0.01, 0.02, 0.03, 0.04, or 0.05mg·kg^–1 was intravenously administered (30 patients each). Blood pressure, heart rate, respiratory rate, percutaneous oxygen saturation (S_{p O 2}), verbal response, eyelash reflex, and involuntary body movement were measured every 5min for 30min. Memory during surgery was also investigated.Results The number of the patients with loss of verbal response, with loss of eyelash reflex, and with no memory during surgery were significantly larger in the groups receiving midazolam 0.03mg·kg^–1, 0.04mg·kg^–1, and 0.02mg·kg^–1, respectively. The decrease in blood pressure or increase in respiratory rate with decrease in S_{p O 2} was significantly larger in the groups receiving midazolam 0.03mg·kg^–1 or 0.05mg·kg^–1, respectively.Conclusion For sedation and amnesia of the patients aged 20–50 years in spinal anesthesia with about 1h duration receiving intramuscular midazolam 0.06mg·kg^–1 as a premedication, intravenous midazolam 0.02mg·kg^–1 might be effective and safe.     

EnHurane supresses phrenic nerve-diaphragm Transmissionin vivo

We examined the effects of enflurane on the diaphragmatic function in 15 pentobarbital-anesthetized, mechanically ventilated dogs. They were divided into three groups of five animals each, according to the administered concentration of enflurane. The diaphragmatic function was assessed from transdiaphragmatic pressure (Pdi) and integrated diaphragmatic electromyography (Edi) developed at functional residual capacity against an occluded airway during bilateral supramaximal phrenic nerve stimulation at 0.5, 10, 20, 50 and 100Hz under quasiisometric condition. After a control measurement, enflurane was administered at a constant end-expired concentration (0, 0.5 and 1MAC) and the measurement was repeated after 1 hour of exposure. The Pdi amplitude generated by single twitch (0.5Hz) and during 10, 20 and 50Hz stimulation was unchanged between the groups. No change in Pdi during 100Hz stimulation was noted during 0 and 0.5MAC exposure, while it was reduced by 1MAC of enflurane. When the values of Pdi were expressed as % of maximum Pdi (%Pdi,max) that developed during control measurement and analyzed in terms of %Pdi,max—stimulus frequency relationship, a significant decrease in %Pdi,max was noted for 100Hz stimulation in 0.5 and 1MAC groups compared to the control. Similarly, Edi during 100Hz stimulation obtained in 0.5 and 1MAC groups was markedly depressed compared to the control. Edi during 50Hz stimulation was also decreased at 1MAC. Relative changes in Edi following enflurane administration were greater than the corresponding changes of Pdi. These results demonstrate that enflurane impairs diaphragmatic function through its inhibitory effects on neuromuscular transmission.(Kochi T, Ide T, Isono S, et al.: Enflurane supresses phrenic nerve-diaphragm transmission in vivo. J Anesth 5: 260–267, 1991)     

Changes in pulmonary function during continuous epidural bupivacaine with or without morphine following upper abdominal surgery

To assess the effect of postoperative continuous thoracic epidural infusion of bupivacaine on pulmonary function, a prospective randomized study was conducted in patients undergoing upper abdominal surgery (UAS). Sixteen patients, divided into two treatment groups, received continuous epidural infusion of 0.25% bupivacaine at a rate of 2–5ml·hr^–1, or that of a combination of 0.125% or 0.25% bupivacaine and 0.0025% or 0.005% morphine at a rate of 2–4ml·hr^–1. One, 4, 10, 16, 24 and 40hr postoperatively, the following indices were measured: visual analogue scale score, modified Prince Henry pain scale score, arterial Pa_{O 2} and Pa_{CO 2}, functional residual capacity (FRC), and tidal volume (TV). There was no difference in pain scores between the two groups except for significantly less pain at 40hr in the combination group. Postoperative measurements of pulmonary function revealed a significant fall in Pa_{O 2}, FRC and TV, indicating a reduction of 15–25% as compared with the preoperative values, and no significant differences between the two groups. The authors conclude that postoperative continuous epidural infusion of bupivacaine combined with morphine is highly effective in alleviating pain and impoving pulmonary function in patients following USA.(Sakura S, Yanagidani T, Saito Y et al.: Changes in pulmonary function during continuous epidural bupivacaine with or without morphine following upper abdominal sugery. J Anesth 4: 319–326, 1990)