Ablation of gene expression of N-methyl-D-aspartate receptor one by antisense oligonucleotides in striatal neurons in culture

In the present study, a twenty-mer antisense oligonucleotide specific for N-methyl-D-aspartate receptor one (ANR1) was applied to striatal neurons in primary cell culture. The ANR1 was found to be specific and nontoxic. Significant reductions in expression of NR1 mRNA and proteins were resulted after a single dose of ANR1 transcripts. Interestingly, there were reductions in total NR1 proteins but two phosphorylated forms of NR1 proteins at serine 896 and 897 residues were not reduced. There was also no change in the pattern of distribution of NR1 immunoreactivity in the striatal neurons. In addition, significant reductions of NMDA-mediated peak inward current were found after application of a higher concentration of ANR1 (20-100 microM) by patch clamp recordings. The present results indicate that ANR1 is a useful agent in reducing NMDA receptor functions. The present data thus provide detailed cellular and molecular mechanisms to explain our previous findings of amelioration of motor symptoms in a rat model of Parkinson's disease. More importantly, application of ANR1 was also found to display neuroprotective effects of striatal neurons against NMDA-induced excitotoxic cell death. The findings have implications in development of new approach in prevention of cell death in neurodegenerative diseases and new treatments for these diseases.

Striatal neurons but not nigral dopaminergic neurons in neonatal primary cell culture express endogenous functional N-methyl-d-aspartate receptors

Developmental expression of N-methyl-D-aspartate (NMDA) receptor subunits were determined and compared in striatal and nigral neurons in neonatal primary cell cultures. In striatal neurons, NR1, NR2A and NR2B mRNAs and immunoreactivity, and NR2D mRNA were found and the maximal levels of NR1 mRNA and immunoreactivity expression were found at 6 day-in-vitro (DIV). NMDA receptors found at this stage in striatal neurons are likely to contain NR1 plus NR2A, NR2B and NR2D subunits. In nigral neurons, NR1 and NR2B mRNAs and immunoreactivity, and NR2D mRNA were found and the maximal level of NR1 immunoreactivity expression was found at 10 DIV. Unlike striatal neurons, NMDA receptors found in nigral neurons are likely to contain NR1 plus NR2B and NR2D subunits only. NMDA-induced toxicity assays showed that striatal neurons were most susceptible to cell death at around 10 DIV but nigral neurons were not susceptible to NMDA-induced cell death at all stages. In addition, patch clamp analysis revealed that functional NMDA receptors could only be found in striatal neurons but not in nigral dopaminergic neurons in vitro. The present results indicate that striatal and nigral neurons are programmed to express distinct NMDA receptor subunits during their endogenous development in cell cultures. Despite dopaminergic neurons in culture display NMDA receptor subunits, functional NMDA receptors are not assembled. The present findings have demonstrated that dopaminergic neurons in vitro may behave very differently to their counterparts in vivo in terms of NMDA receptor-mediated responses. Our results also have implications in transplantations using dopaminergic neurons in vitro in treatments of Parkinson's disease.

Differential expression of N-methyl-D-aspartate receptor subunit messenger ribonucleic acids and immunoreactivity in the rat neostriatum during postnatal development

The present study was performed to investigate the patterns of gene expression of N-methyl-D-aspartate (NMDA) receptors (NRs) in the rat neostriatum during postnatal development. Reverse transcriptase-polymerase chain reactions (RT-PCR) indicated that levels of NR1, NR2A and NR2D mRNAs reached peak levels between postnatal days 7 (PND 7) and PND 14. The levels of NR2B and NR2C mRNAs were low at PND 1 and their levels increased at PND 7 and remained high in adults. Immunofluorescence combined with image analysis revealed that the levels of NR1 immunoreactivity rose to its maximum at PND 14. In contrast, NR1 immunoreactivity rose progressively in perikarya of striatal neurons. Levels of NR2A immunoreactivity in the neostriatum were highest in adults. However, levels of NR2A immunoreactivity were higher in striatal neurons at PND 1 and PND 7. Levels of NR2B immunoreactivity were highest at PND 7. In the perikarya of striatal neurons however, the highest levels of NR2B immunoreactivity were detected at PND 14 and adult striatal neurons. In addition, double immunofluorescence revealed that the levels of NR1 immunoreactivity increased but the levels of NR2A immunoreactivity were the same in parvalbumin (PV)-positive striatal interneurons of PND 14 and adult rats. NR2B immunoreactivity was not detected in PV-positive neurons of PND 14 rats, but intense NR2B labeling was seen in PV-positive neurons of adult rats. Last but not least, in choline acetyltransferase (ChAT)-positive striatal interneurons of PND 14 and adult rats, levels of NR1 and NR2A immunoreactivity was seen to increase. Level of NR2B immunoreactivity remained the same in ChAT-positive neurons of PND 14 and adult rats. The present results indicate that there are differential patterns of expression of NR mRNAs and immunoreactivity in the neostriatum during different stages of postnatal development. Different combinations of NR have been found in different subpopulations of striatal neurons at different developmental stages. NR1, NR2A and NR2B are the major NMDA receptor subunits expressed during development. The change in patterns of expression of NR may be related to the functional maturation of neurons in the neostriatum.

Different trends in modulation of NMDAR1 and NMDAR2B gene expression in cultured cortical and hippocampal neurons after lead exposure

Exposure to heavy metal lead (Pb(2+)) has been reported to cause problems in cognitive functions of the brain, e.g. memory loss and difficulties in mental development. N-Methyl-D-aspartate receptors (NRs) are important molecules that are known to be involved in mediation of learning and memory. In order to investigate the effects of Pb(2+) on the gene expression of NR1 and NR2B subunits in neurons, primary cell cultures of rat cortical and hippocampal neurons were employed. After treatments with different concentrations of Pb(2+) ions in culture medium (0, 5, 10, 25 and 50 microM), the cellular localization of Pb(2+) in neurons was evaluated by laser scan confocal microscopy by using a Pb(2+) ion specific fluorescence probe. In addition, the gene expression of NR1 and NR2B subunits was determined by reverse transcriptase-polymerase chain reaction, immunofluorescence and Western blotting. The results of the present study showed that both cortical and hippocampal neurons accumulated intracellular Pb(2+) in accordance with the concentrations of Pb(2+) ions present in the culture medium. After Pb(2+) treatments, levels of NR1 mRNA, immunoreactivity and protein were found to be unchanged but levels of NR2B mRNA, immunoreactivity and protein were found to be significantly increased in cortical neurons. In contrast, both NR1 and NR2B mRNAs, immunoreactivity and proteins were found to be significantly decreased in hippocampal neurons. The changes in gene expression were found to be dose dependent in accordance with the Pb(2+) concentrations. The present results indicate that Pb(2+) has a differential effect on the expression of NR1 and NR2B subunits in cortical and hippocampal neurons, respectively. It is likely that the toxic effects of Pb(2+) may cause differential damage to different types of memory that are mediated by cortical and hippocampal neurons, respectively.

Anesthetic management of a patient with relapsing polychondritis--a case report

Relapsing polychondritis is a rare multisystem disorder of uncertain etiology. It is characterized by recurrent and progressive destruction of both elastic and hyaline cartilages as well as connective tissue. Respiratory tract involvement is associated with high mortality and morbidity. General anesthesia may be required in these patients for tracheostomy, bronchoscopy, nasal reconstruction, aortic valve replacement, and recent tracheobronchial stenting which they usually sustain. Tracheostomy was once the most likely surgical procedure in relapsing polychondritis. However, this procedure is only effective in patients with upper subglottic involvement. In cases of extensive tracheobronchial involvement, tracheostomy is ineffective because the distant tracheal collapse below the tracheostomy is still unresolved. We would like to report a case of relapsing polychondritis with tracheobronchial involvement, who underwent an emergent tracheostomy. Tracheostomy with continuous positive airway pressure (CPAP) effectively improved her airway collapse. Herein, we also discuss the anesthetic management after review of the current literature.

Chemical sympathectomy for neuropathic pain: does it work? Case report and systematic literature review

OBJECTIVE

To determine if chemical sympathectomy successfully reduces limb neuropathic pain.

DESIGN

Systematic literature review of the effectiveness of phenol or alcohol sympathectomy for extremity neuropathic pain.

PATIENT

A 29-year-old female with complex regional pain syndrome of both lower extremities after back surgery who was submitted to bilateral lumbar chemical sympathectomy.

SEARCH STRATEGY

The Cochrane Database of Systematic Reviews, the Cochrane Controlled Trials Register, Medline, and EMBASE were systematically searched.

OUTCOME MEASURES

(1) For the patient in question: spontaneous pain, allodynia, pinprick hyperalgesia, pressure evoked pain; (2) For the literature review: meaningful versus nonmeaningful pain relief based on degree and duration (>2 weeks) of pain relief.

RESULTS

(1) The case reported experienced partial temporary relief of pain primarily related to selective modulation of allodynia, but not deep pain or pinprick hyperalgesia; (2) 44% of 66 patients in 13 studies that met the authors' inclusion criteria experienced meaningful pain relief. Whereas 19% experienced no meaningful relief, for the remaining 37% of the patients no conclusions regarding duration and degree of relief could be drawn due to poor reporting of outcomes.

CONCLUSIONS

Based on the case reported and systematic literature review, chemical sympathectomy seems to have at best a temporary effect, limited to cutaneous allodynia. Despite the popularity of chemical sympatholysis, only few patients and poorly defined outcomes are reported in the literature, substantiating the need for well-designed studies on the effectiveness of the procedure.

Inadvertent hypothermia causes pulseless electrical activity in a patient during cervical spine surgery--a case report

Recent studies have shown that hypothermia triples the incidence of major cardiac events. We present a happening in which a 71-year-old patient developed pulseless electrical activity (PEA) while he was undergoing cervical laminectomy for spinal stenosis in the sitting position. Thromboembolism or venous air embolism and acute myocardial infarction were respectively excluded by transesophageal echocardiography and cardiac enzymes analysis to be the causes of the cardiac event. The abnormal finding that stood out was low nasopharyngeal temperature (31 degrees C) during the procedure, which was thought to contribute to the development of the PEA episode.

Thermal symmetry of skin temperature: normative data of normal subjects in Taiwan

BACKGROUND

The aims of this study were (a) to establish normative data of thermal symmetry (left vs. right) in normal subjects; (b) to compare the skin temperature in various regions between young and old people in Taiwan and between male and female.

METHODS

The skin surface of 57 healthy volunteers (aged 24 to 80 yr) was divided into 25 areas and measured by an infrared thermography (Avionics TVS-2000, Japan). The average temperatures of these 25 regions were compared: (a) left vs. right side, (b) young (< or = 60 yr, n = 37) vs. old (> 60 yr, n = 20), and (c) male vs. female. Student's t-test was used to assess means between both groups.

RESULTS

The neck carried the highest skin temperature (31.9 degrees C +/- 0.6; mean +/- SD) of the body in comparison with the toes that had the lowest one (27.5 degrees C +/- 2.0). The side-to-side temperature differences were subtle, which did not exceed 0.5 degrees C. The average skin temperature of elderly was slightly lower than that of young subjects in 11 out of 25 areas (p < 0.05), especially the distal parts of extremities. Elderly female had lower skin temperature in various truncal areas as compared with their counterpart. However, the skin temperature was higher in the distal extremity (p < 0.05).

CONCLUSIONS

The thermoregulatory system is substantially symmetrical. The result of this study offered valuable normative database on skin thermal symmetry in normal population of Taiwan, and may be useful as a diagnostic aid in patients with various states of disorders associated with autonomic dysfunctions.

Hemodynamic changes caused by venous gas embolism in dogs: comparisons among air, carbon dioxide and oxygen

BACKGROUND

The volume of a bulky venous air emboli (VAE) can be estimated based on the calibration curve generated by injections of minute amount of air into the right atrium (RA) of dogs. We speculated that in patients similar VAE calibration curves could be generated using CO2 injections. As part of pre-clinical evaluation of the usefulness of CO2 injection, the present study was designed to determine whether injection of CO2 into the RA would cause less hemodynamic changes in dogs as compared with that of air or O2.

METHODS

Twenty-one anesthetized mongrel dogs were divided into 3 groups, i.e., groups air, CO2 and O2 (n = 7 each). Animals were injected a bolus of gas (air, CO2 or O2) in increasing volumes (from 0.25 to 4.0 mL/kg) into the RA via a central venous catheter at 10-min intervals. We measured the maximal changes in mean arterial pressure (MAP), pulmonary arterial pressure (PAP), central venous pressure (CVP), end-tidal CO2 (ETCO2), heart rate (HR), and mixed venous O2 saturation (SvO2).

RESULTS

After venous injections, dogs receiving O2 or air showed greater decreases in MAP and ETCO2 as compared with those receiving CO2 (volume > 2.5 mL/kg; P < 0.05). The increases in PAP and CVP bore direct relation to O2 and air volume. In the CO2 group, the maximal changes in PAP and CVP were subtle as compared with the baseline (P < 0.05). There were no significant differences in HR and SvO2 among three groups.

CONCLUSIONS

Injections of CO2 in increasing volumes into the RA of dogs caused less hemodynamic changes in comparison with that of air and O2.

Repeated attacks of venous air embolism during craniotomy--a case report

Venous air embolism (VAE) is not uncommon during craniotomy, but repeated attacks of VAE during a single surgical procedure is rarely seen. We report a successful intraoperative management of repeated attacks of air embolism in a patient who sustained craniotomy for intracranial hemorrhage (ICH) in prone position. A 70-year-old male suffering from hemorrhage in the right cerebellar hemisphere with impending brainstem herniation was scheduled for craniotomy. He had history of hypertension but it was not well controlled with medical treatment. Emergent craniotomy for removal of blood clot resulting from ICH was performed. During the operation, sudden decrease of end-tidal CO2 (EtCO2) level, fall of blood pressure and increase of central venous pressure (CVP) were noted. Since air bubbles were retrieved from CVP catheter venous air embolism was highly suspected. With prompt diagnosis and proper management, we successfully improved the patient's hemodynamic status and he was discharged without any sequelae. Early detection together with aggressive treatment is the only way in the management of intraoperative venous air embolism.

Inadvertent knotting of a thoracic epidural catheter

We report a case of corrosive injury of upper gastrointestinal and respiratory tracts scheduled for feeding jejunostomy under thoracic epidural anesthesia. An epidural catheter was inserted at the T8-T9 intervertebral space and threaded 7 cm beyond the tip of the Tuohy needle in a rostral direction. Resistance was noticed during attempts to inject the local anesthetic. As resistance could not be relieved by changing the position of the patient, kinking of the epidural catheter was suspected. Following informing the patient of the associated risks, the catheter was retrieved successfully by gentle and steady pulling. A tight double-knot of catheter was found. No neurological sequelae to the procedure were noticed.

Bilateral pulmonary edema after endoscopic sympathectomy in a patient with glucose-6-phosphate dehydrogenase deficiency

Transaxillary endoscopic sympathectomy of thoracic ganglia (T2-T3) has recently gained wider acceptance as the treatment of choice for palmar hyperhidrosis. It requires one-lung ventilation to facilitate the surgery. One-lung ventilation, however, is not without complications, among which acute pulmonary edema has been reported. In this case report, we present a patient with palmar hyperhidrosis complicated by glucose-6-phosphate dehydrogenase (G-6-PD) deficiency, who received bilateral endoscopic sympathectomy under alternate one-lung anesthesia, and developed acute pulmonary edema immediately after recruitment of the successive collapsed lung. The effects of hypoxemia, G-6-PD deficiency and sympathectomy might all add to the development of acute pulmonary edema secondary to reexpansion of each individual lung after alternate one-lung ventilation. The possibilities of the inferred causes are herein discussed.

Thoracic epidural analgesia with morphine does not prevent postthoracotomy pain syndrome: a survey of 159 patients

BACKGROUND

This retrospective study sought to determine the incidence of postthoracotomy pain syndrome (PTPS), and whether epidural morphine for the postoperative analgesia could prevent the development of PTPS.

METHODS

We reviewed the charts of 372 patients who had undergone thoracotomy. The majority underwent general anesthesia (GA) combined with thoracic epidural analgesia (TEA). Of the 372 patients, only 159 (42%) were available for interview. Patients were divided into two groups based on the duration of pain, i.e., pain group (pain > 3 months, n = 65) and pain-free group (pain < 3 months, n = 94).

RESULTS

Both groups were comparable regarding sex, age, weight, height, smoking, alcohol ingestion, education, marital status, duration of surgery, and the number of patients either receiving GA plus TEA or GA alone. About 41% of the patients experienced PTPS that persisted for 21 +/- 12 mon (follow-up: 28 +/- 12 mon). Most pain was mild or moderate and was usually described as being only a discomfort. Only 6.2% suffered severe pain with shooting, aching, burning or numbness. Patients with PTPS suffered more depression and insomnia. The incidence of PTPS was not different in patients who received GA alone or GA plus TEA (39% vs. 42%).

CONCLUSIONS

Epidural morphine for postoperative analgesia that continued for 3 days appeared to have no effect in the prevention of PTPS.

Effects of glucose-free maintenance solution on plasma glucose during anesthesia in patients undergoing long neurologic surgery

BACKGROUND

Using glucose-free solution as fluid maintenance is widely advocated during neurosurgery because of concerns about hyperglycemia aggravating cerebral ischemia. This study evaluated the alterations in plasma glucose concentrations in both adult and pediatric patients undergoing lengthy neurologic surgery, during which they were given glucose-free solutions.

METHODS

This study included 154 patients (ASA class II, aged 3 months-75 years) undergoing elective neurosurgical procedures. They were divided into two groups: group A (15-75 years-of-age) and group P (3 months-14 years-of-age). Groups A (n = 126) and P (n = 28) were further divided into five subgroups, respectively, based on the duration of surgery: 5, 6, 7, 8 and 9 hours. Anesthesia was maintained with isoflurane, fentanyl and vecuronium. Blood sampling was undertaken every hour throughout surgery.

RESULTS

Adult patients differed significantly in body weight (61.5 +/- 10.9 vs 25.6 +/- 14.9 kg), age (58.9 +/- 15.7 vs 7.5 +/- 4.3 years), use of preoperative beta-blocking agents (33/126 vs 1/28) and the need for blood transfusion (58/126 vs 24/28). Neither group had elevated glucose levels. Compared with pediatric patients, the incidence of intraoperative hypoglycemia was statistically higher in adult patients, with a rate that peaked in the eighth (25.9%, group A vs 0% group P) and ninth hours (27.3%, group A vs 0% group P) of surgery. There were no differences in glucose concentrations at other points in time.

CONCLUSIONS

In contrast to pediatric patients, intraoperative hypoglycemia occurred more often in adult patients during prolonged neurosurgical procedures when glucose-free solution was used for fluid maintenance. Therefore, frequent determination of plasma glucose concentrations is mandatory, especially in patients undergoing long-lasting neurosurgical anesthesia.

Postoperative right atrial and pulmonary embolism after prolonged spinal surgery

Perioperative pulmonary thromboembolism can proceed rapidly with grave prognosis, in which immediate or accurate diagnosis and management is not easy. According to the literatures, patients receiving spinal surgery are at relatively lower risk of developing thromboembolism. We would like to present a case of postoperative pulmonary thromboembolism which developed after a prolonged lumbar spinal surgery. Tachycardia and unstable hemodynamics were noted postoperatively. Pulmonary and right atrial thrombi were disclosed by transesophageal echocardiography. Although cardiotomy and thrombectomy were immediately performed, the patient finally died 3 days after the operation. The pathogenesis of venous thromboembolism (VTE) in the surgical patients, the risk factors which predispose a patient to VTE, diagnosis, and treatment as well as the prophylactic measures of VTE are herein reviewed and discussed.

Postoperative pulmonary edema after cervical spine surgery--a case report

Injury of the cervical spine may cause serious complications and neurological sequelae. Recently, a patient with C1-2 spinal cord compression developed pulmonary edema postoperatively associated with unstable hemodynamics, which might result from overzealous fluid administration in order to correct neurogenic shock during anesthesia. Therefore, early recognition and timely use of vasoconstrictors, together with judicious fluid replacement are important in the anesthetic management of patients with cervical spine injury undergoing surgery. In addition, the placement of pulmonary artery catheter is crucial for assessing the cardiac function and fluid status.

Normative data of quantitative thermal and vibratory thresholds in normal subjects in Taiwan: gender and age effect

BACKGROUND

Quantitative sensory testing has gained popularity as a tool in the diagnosis of peripheral neuropathies. This study aims to establish normative data of quantitative thermal and vibratory thresholds in normal subjects in Taiwan. In addition, we also examined the effect of age and gender differences on these thresholds.

METHODS

The study included 100 healthy subjects (50 males and 50 females) who were admitted for regular physical examination. The quantitative testing of thermal, cold and vibratory sensations were performed having recourse to a Thermotest instrument applied on the right hand and foot of these subjects. Measurements included perception thresholds of warm (WT), cold (CT), heat pain, cold pain and vibration as well as a visual analog pain scale.

RESULTS

Age was comparable between the sexes, but the male subjects were taller than the female subjects. A higher WT and CT in the hand, but not in the foot, were found in the male subjects in comparison with the female subjects. Heat pain threshold and cold pain threshold of both sites did not significantly differ between genders. Moreover, the groups did not differ in vibration threshold and visual analog pain scale. Young subjects (age < 30 years) showed a higher CT in the foot than the older subjects (age > 50 years). None of the above parameters were different between these two age groups. Overall, the age or height bore no significant relation to the difference between WT and CT (DDWT-CT).

CONCLUSIONS

The female subjects were found to be more sensitive to warm and cold stimulation in the hand than their counterparts. These results have provided valuable normative data on sensory perceptive thresholds in Taiwanese, which are useful as a tool in the diagnosis of peripheral neuropathy.

Unexpected transurethral resection of prostate syndrome complicated with acute myocardial infarction during transurethral incision procedure--a case report

Transurethral incision (TUI) is a simple and safe procedure. We, herein, present a case undergoing transurethral incision procedure during which he developed transurethral resection of prostate syndrome (TURP syndrome) and hypothermia precipitating an acute perioperative myocardial infarction attack. The potential risk of development of TURP syndrome in settings other than TURP surgery as well as its prevention are reviewed and discussed.

Wavelet analysis of embolic heart sound detected by precordial Doppler ultrasound during continuous venous air embolism in dogs

The spectrum of the embolic heart sounds (EHS) detected by precordial Doppler ultrasound has been previously characterized, but only on small volumes of venous air embolism (VAE). We sought to determine whether real-time wavelet analysis is useful in analyzing the signals of EHS and whether the embolic power of the EHS for larger volumes of air is proportionate to the volume of VAE that has been reported for small volumes of VAE. A series of small air boli (0.01, 0.02, 0.05, 0.07, 0.1, 0.15, 0.2, 0.3, 0.4, and 0.8 mL), followed by continuous infusion of larger volumes of air (0.8, 1.6, 2.4, 4.8, and 9.6 mL), was injected into the external jugular vein through a central catheter in seven pentobarbital-anesthetized dogs. We measured the spectrum of the Doppler heart sound (DHS) in a real-time manner by using wavelet analysis at different scales. Wavelet analysis at scale = 1 yielded satisfactory results in distinguishing abnormal EHS from normal DHS with high sensitivity (100%) and good positive predictive value (100%) compared with the conventional method, which requires an anesthesiologist to listen to the audio DHS signals in a real-time manner. There was a linear relationship (y = 1.08x + 7.89, r = 0.75, P < 0.001) between the cumulative embolic power of the EHS and the air volume introduced in the form of either bolus or continuous infusion. The 95% confidence intervals for slope and intercept were 0.89-1.27 and 7.65-8.13, respectively. Our results suggest that wavelet analysis is effective as a real-time monitor and that it is possible to distinguish larger volumes of air emboli based on previous injections of small volumes of air.

IMPLICATIONS

The real-time wavelet analysis of the heart sound detected by precordial Doppler ultrasound may be useful in estimating larger volumes of air emboli based on previous injections of small volumes of air in anesthetized dogs.

Involvement of cerulospinal glutamatergic neurotransmission in fentanyl-induced muscular rigidity in the rat

BACKGROUND

Investigators in the authors' laboratory previously established the critical participation of the cerulospinal noradrenergic pathway in muscular rigidity elicited by fentanyl. The identification of colocalization of glutamate with tyrosine hydroxylase in most locus ceruleus neurons suggests a role for cerulospinal glutamatergic neurotransmission in fentanyl-induced muscular rigidity. This suggestion and the subtype(s) of glutamate receptors involved were investigated here.

METHODS

Electromyographic signals activated by bilateral microinjection of 2.5 microg fentanyl into the locus ceruleus were recorded differentially from the left sacrococcygeus dorsi lateralis muscle of adult male Sprague-Dawley rats. The effect of intrathecal administration at the lower lumbar spinal cord of various N-methyl-D-aspartate (NMDA) and non-NMDA receptor antagonists or agonists on this index of muscular rigidity was studied. Rats were under mechanical ventilation, and intravenous infusion of ketamine (30 mg x kg(-1) x h(-1)) was maintained until 10 min before fentanyl was administered.

RESULTS

Microinjection of fentanyl bilaterally into the locus ceruleus increased the root mean square and decreased the mean power frequency values of electromyographic signals. The efficacy of fentanyl to elicit muscular rigidity in this manner was significantly reduced by previous intrathecal administration of either 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801), D-(-)-2-amino-5-phosphonovaleric acid (AP5), or (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP). Intrathecal administration of kainic acid or NMDA also resulted in significant electromyographic activation.

CONCLUSIONS

In addition to the cerulospinal noradrenergic mechanism, the cerulospinal glutamatergic pathway and both NMDA and non-NMDA receptors in the spinal cord may mediate fentanyl-induced muscular rigidity in the rat.

Fast detection of venous air embolism in Doppler heart sound using the wavelet transform

The introduction of air bubbles into the systemic circulation can result in significant morbidity. Real-time monitoring of continuous heart sound in patients detected by precordial Doppler ultrasound is, thus, vital for early detection of venous air embolism (VAE) during surgery. In this study, the multiscale feature of wavelet transforms (WT's) is exploited to examine the embolic Doppler heart sound (DHS) during intravenous air injections in dogs. As both humans and dogs share similar physiological conditions, our methods and results for dogs are expected to be applicable to humans. The WT of DHS at scale 2j (j = 1, 2) selectively magnified the power of embolic, but not the normal, heart sound. Statistically, the enhanced embolic power was found to be sensitive (P < 0.01 at 0.01 ml of injected air) and correlated significantly (P < 0.0005, r = 0.83) with the volume of injected air from 0.01 to 0.10 ml. A fast detection algorithm of O(N) complexity with unit complexity constant for VAE was developed (processing speed = 8 ms per heartbeat), which confirmed the feasibility of real-time processing for both humans and dogs.

Involvement of spinal adenosine A1 and A2 receptors in fentanyl-induced muscular rigidity in the rat

In the present study, using hydrophilic adenosine antagonists either selective to A1 or A2 receptors, we investigated the central and spinal adenosinergic participation in fentanyl-induced muscular rigidity. Adult Sprague-Dawley rats were anesthetized with ketamine and were under mechanical ventilation. Fentanyl (100 micrograms/kg, i.v.) consistently elicited electromyographic (EMG) activation in the sacrococcygeal dorsalis lateralis muscle. This implied muscular rigidity was not blocked by i.c.v. administration of the adenosine A1 antagonist, 1-allyl-3,7-dimethyl-8-p-sulfophenyl-xanthine (ADSPX; 20 or 40 nmol/2.5 microliters), except at higher dose (80 nmol). Equimolar doses of the adenosine A2 antagonist, 3,7-dimethyl-1-propargylxanthane (DMPX), did not exert any inhibitory effect on fentanyl-induced rigidity. Intrathecal (i.t.) administration of the same doses of ADSPX (20, 40 or 80 nmol/10 microliters) appreciably suppressed the EMG activation. However, the rigidity was only inhibited by 40 or 80 nmol (i.t.) of DMPX, but not by the lowest dose. High-dose (80 nmol, i.t.) adenosine A1 or A2 antagonist per se did not induce motor impairment or hindlimb paralysis in conscious animals. These results suggest that adenosine A1 and A2 receptors in the spinal cord may play a more crucial role than those in the central nervous system (CNS) in fentanyl-induced muscular rigidity in rats.

Comparison of diuretic effects of glycerol with furosemide after transurethral prostatectomy

BACKGROUND

Diuretic therapy after transurethral prostatectomy (TURP) is primarily intended to induce diuresis against water intoxication and cystic clot retention. This study was undertaken to compare the diuretic effects of glycerol with furosemide after TURP.

METHODS

Thirty patients (ASA I or II) undergoing TURP were studied. Spinal anesthesia was induced with bupivacaine. At the end of prostatic resection, the patients were randomly allocated into two groups. In one group (n = 15) the patients received furosemide 30 mg i.v., while in the other group (n = 15) they received glycerol 0.5 g/kg i.v. Blood samples were collected for measurements of osmolality, hematocrit, sodium and glucose concentration before anesthesia and after surgery. Urine output was also recorded after surgery in each group.

RESULTS

Plasma osmolality in glycerol group was higher than furosemide group at 30 min (295.3 +/- 10.6 vs. 283.8 +/- 5.6 mOsm/kg, p < 0.01) and 1 h after operation (294.9 +/- 8.7 vs 286.3 +/- 6.7 mOsm/kg, p < 0.01). Blood glucose was higher in glycerol group than that in furosemide group at 2 h after operation (195.6 +/- 121.9 vs 152.9 +/- 70.1 mg/dl, p < 0.05). Measured urine output was significantly greater in furosemide group at 30 min after operation (904.6 +/- 491.5 vs. 248.4 +/- 143.4 ml, p < 0.05) but was greater in glycerol group at 12 h after operation.

CONCLUSIONS

Since urine output is significantly less in glycerol group at 1 h after operation, glycerol is inferior to furosemide for preventing cystic clot retention after TURP. But glycerol may protect against water intoxication better for its merit of producing higher plasma osmolality.

Terbutaline inhalation suppresses fentanyl-induced coughing

PURPOSE

To study the suppressive effect of inhalation of a selective beta 2-adrenergic bronchodilator terbutaline, and the effect of an intravenous anticholinergic, atropine, on fentanyl-induced coughing.

METHODS

We studied 131 ASA class I patients, aged 16-45 yr, scheduled for elective surgery, randomized into four groups. Fifteen minutes before bolus fentanyl (5 micrograms.kg-1, iv), patients inhaled either normal saline (4 ml; Group I, n = 30) or terbutaline (5 mg in 2 ml normal saline; Group 2, n = 34) via a jet nebulizer. After inhalation of normal saline, patients in Group 3 (n = 32) received sterile water iv instead of fentanyl. Patients in Group 4 (n = 35) were pretreated with atropine (0.01 mg.kg-1, iv) 10 min before iv fentanyl bolus. The onset, frequency and intensity of cough were observed immediately by an anaesthetist blinded to the study.

RESULTS

The cough frequency was higher in Groups I (43%) and 4 (46%) than in Groups 2 (3%) and 3 (0%) (P < 0.05). The onset time and intensity of cough showed no difference among groups. No truncal rigidity was observed in patients receiving fentanyl bolus iv. The blood pressure, heart rate, and peripheral oxygen saturation did not change in Groups 1, 2, and 3, while patients in Group 4 showed an increase in heart rate (25.5 +/- 15.2%).

CONCLUSIONS

The inhalation of a selective beta 2-adrenergic bronchodilator, terbutaline, effectively inhibited fentanyl-induced cough, whereas atropine, an antimuscarinic vagolytic, had no efficacy. Our results suggest that bronchoconstriction may underlie the mechanism on fentanyl-induced cough.

A child of suspected malignant hyperthermia during general anesthesia for dental surgery

Malignant hyperthermia is clinically an uncommon disorder characterized by acute hypercatabolic reactions in muscles in response to the triggering effects of certain drugs mainly used during anesthesia or to physical or emotional stress. We present a pediatric patient with multiple caries who was suspected to contract malignant hyperthermia while underwent the operative procedure of comprehensive restoration. Sinus tachycardia, hyperthermia, hypercapnia, metabolic acidosis, hyperkalemia and hypercalcemia developed unexpectedly during the operation. Fortunately, the patient survived the episode with early recognition and prompt management.

Incidence and risk factors of guidewire-induced arrhythmia during internal jugular venous catheterization: comparison of marked and plain J-wires

STUDY OBJECTIVES

To compare the incidence and risk factors of guidewire-induced arrhythmia (GIA) during internal jugular venous catheterization (IJV).

DESIGN

Prospective study.

SETTING

Operating rooms at a medical center.

PATIENTS

303 ASA physical status I, II, III, and IV patients undergoing elective surgery.

INTERVENTIONS

All patients were cannulated with the central venous catheters placed via the right internal jugular vein after induction of anesthesia. They were randomly divided into two groups. In one group, we used a marked J-wire and inverted up to, but not beyond 20 cm (Group M, n = 127). In the other group, a plain unmarked J-wire was used and inserted at will (Group UM, n = 176). All IJV catheterizations were performed by residents, and the length of J-wire inserted was then measured.

MEASUREMENTS AND MAIN RESULTS

Types of arrhythmia [eg, premature atrial contraction (PAC) or premature ventricular contraction (PVC)] were interpreted by attending anesthesiologists on lead II ECG. Patients in Group UM had a significantly greater incidence of GIA than those in Group M (28.4% vs. 3.9%; p < .005). However, in both groups, PAC occurred more frequently than PVC. Factors such as the inserted length of guidewire longer than 20 cm, body height less than 170 cm, and female gender were significantly associated with GIA (p < 0.005).

CONCLUSIONS

Limiting the length of the guidewire insertion to less than or equal to 20 cm for right IJV catheterization by using a marked J-wire will reduce the incidence of GIA. We recommend the use of a marked J-wire for IJV catheterization.

EMG spike trains of succinylcholine-induced fasciculations in myalgic patients

Single spike activity from the surface electromyogram (EMG) of fasciculations induced by succinylcholine (Sch) were studied from limb muscles (biceps, triceps, anterior tibialis and gastrocnemius) in 100 female patients. About 2/3 of them (n = 72) also received nondepolarizing neuromuscular pretreatment (atracurium or vecuronium). We observed from 20% of EMG records in the myalgic (but not in the nonmyalgic) patients, sustained spike trains (mean duration 1.47 s) that resembled motor units firing at physiologically high rates (mean 21.7 spikes/s). The finding reflects Sch's distal actions at the muscle spindle. The implications for myalgia and the possible involvement of micro damage at the extrafusal muscles are discussed.

Spectral analysis of arterial pressure variability during induction of propofol anesthesia

We studied the effect of continuous infusion of propofol on spectral components in systemic arterial pressure (SAP) signals in 35 consenting patients undergoing abdominal surgery. Anesthesia was induced with intravenous bolus administration of propofol (2.0 mg/kg), followed by infusion at either 5 mg.kg-1.h-1 (Group 1, n = 18) or 10 mg.kg-1.h-1 (Group 2, n = 17). Tracheal intubation was facilitated by administration of vecuronium (0.1 mg/kg). The SAP signal was subjected to off-line spectral analysis to obtain changes in power of the very low frequency (VLF; 0.00-0.08 Hz), low frequency (LF; 0.08-0.15 Hz), high frequency (0.15-0.25 Hz); and very high frequency (VHF; 0.80-1.60 Hz) components. Venous blood for the measurement of plasma concentration of propofol was collected at 5 min before bolus injection of propofol; at 5, 10, and 15 min after infusion of propofol; and immediately after endotracheal intubation. Infusion of propofol significantly decreased the total power of SAP spectrum in both groups, especially the VLF, LF, and VHF components at all intervals except postintubation. Immediately after tracheal intubation, patients in Group 1 showed a significant increase in mean arterial pressure when compared with those in Group 2 (118 +/- 5 mm Hg vs 102 +/- 5 mm Hg, P < 0.05). Similar change was also seen in the VLF component (7.4 +/- 0.7 mm Hg2 vs 4.4 +/- 0.5 mm Hg2, P < 0.05). After tracheal intubation, patients in Group 1 showed 15.7-, 3.3-, and 4.4-fold increase in the VLF, LF, and VHF components, respectively. There were 14.1-, 2.8-, and 2.8-fold increases in the respective components of the SAP signal in Group 2. At all intervals, the spectral components of SAP, however, did not correlate well with the plasma concentration of propofol in either group. These results suggest that spectral analysis of SAP signals may provide an alternative for assessing autonomic activities, such as the sympathetic response, to tracheal intubation during propofol anesthesia.

Inhibition by intrathecal prazosin but not yohimbine of fentanyl-induced muscular rigidity in the rat

We evaluated the effect of intrathecally administered prazosin, alpha 1-adrenoceptor antagonist, or yohimbine, alpha 2-adrenoceptor antagonist, on fentanyl-induced muscular rigidity. Adult, male Sprague-Dawley rats were anesthetized with ketamine and were under mechanical ventilation. Fentanyl given intravenously (100 micrograms/kg) or microinjected into the bilateral locus coeruleus (LC) (2.5 microgram/50 nl) consistently evoked a significant increase in the electromyographic activity recorded from the sacrococcygeus dorsalis lateralis muscle. This implied muscular rigidity was appreciably antagonized by prior intrathecal (10 microliters) administration of prazosin (5 or 10 nmol), but not equimolar dose of yohimbine. These results suggest that the spinal alpha 1-adrenoceptors in the coerulospinal noradrenergic pathway play a key role in fentanyl-induced muscular rigidity.

Involvement of potassium and calcium channels at the locus coeruleus in fentanyl-induced muscular rigidity in the rat

Previous work from our laboratory suggested that Go alpha protein at the locus coeruleus (LC) may be involved in the signal transduction process that underlies muscular rigidity induced by fentanyl. The present study further evaluated the roles of K+ and L-type Ca2+ channels, gating of which is known to be associated with activation of Go alpha protein, in this process, using Sprague-Dawley rats anesthetized with ketamine. Bilateral microinjection into the LC of tetraethylammonium chloride (100 or 200 pmol), a K+ channel blocker, and S(-)-Bay K 8644 (0.5 nmol), a Ca2+ channel activator, produced significant antagonization of the EMG activation elicited by fentanyl (100 micrograms/kg, i.v.), as recorded from the sacrococcygeus dorsalis lateralis muscle. On the other hand, local application to the bilateral LC of diazoxide (10 or 20 nmol), an ATP-dependent K+ channel activator, and nifedipine (0.25 or 0.5 pmol), a L-type Ca2+ channel blocker, was ineffective in blunting fentanyl-induced muscular rigidity. These results suggest that activation of K+ channels and/or inhibition of L-type Ca2+ channels secondary to triggering of the Go alpha protein at the LC may underlie the signal transduction process in the mediation of fentanyl-induced muscular rigidity.

Magnesium sulfate has negligible effect on middle cerebral artery blood flow velocity in response to endotracheal intubation

BACKGROUND

Pretreatment of magnesium sulfate (MgSO4) attenuates pressor response associated with endotracheal intubation. Vasodilating effect of MgSO4 may increase cerebral blood flow, which upsets the known benefit to cardiovascular hemodynamic. In the present study, we evaluated the effect of MgSO4 on the changes of cerebral blood flow in response to endotracheal intubation.

METHODS

Twenty four ASA class I or II patients who randomly received either normal saline 5 ml or MgSO4 (60 mg/kg, i.v.) 3 min before induction of anesthesia were included in the study. Mean blood flow velocity (VMCA) of the middle cerebral artery was obtained using a transcranial Doppler sonography (TCD) before and after endotracheal intubation. Anesthesia was induced with fentanyl (4 micrograms/kg) and thiopental (5 mg/kg) and endotracheal intubation was facilitated with succinylcholine (1.5 mg/kg).

RESULTS

Before endotracheal intubation, MgSO4 caused a transient decrease in VMCA (98 +/- 6% vs. 76 +/- 3% of baseline) and increase in heart rate (132% vs. 114% of baseline) compared to saline group. However, VMCA and heart rate did not show significant difference in both groups after tracheal intubation. Also, systolic and diastolic blood pressure did not differ during the study.

CONCLUSIONS

Our results suggest that MgSO4 appeared to have negligible effects on cerebral blood flow and hemodynamics in response to tracheal intubation. Its attenuating effect on pressor response induced by endotracheal intubation might be over emphasized.

Acquired long QT syndrome in a child undergoing craniotomy: a case report

The long QT syndrome (LQTS) is a rare disorder of cardiac conduction in children. It may lead to severe arrhythmia, syncope or sudden death. Electrolyte disturbance and the use of procainamide are closely related to the acquired LQTS. This report concerns a fatality of acquired LQTS in a boy undergoing craniotomy. After induction of anesthesia, his electrocardiogram displayed a frequent torsade de pointes type of ventricular tachycardia with prolonged QT interval. Therefore, congenital LQTS was impressed. However, the arrhythmia was aggravated by intravenous propranolol. Isoproterenol infusion was given under the diagnosis of acquired LQTS. The arrhythmia was successfully abolished and a stable hemodynamic status was maintained. However, the child could not tolerate the anesthesia which lasted for 30 hours, and eventually succumbed, despite aggressive treatment and resuscitation attempts. Differential diagnosis between the types of LQTS should be made promptly. This may be of paramount importance in the outcome since prognosis depends upon proper treatment. This case report discusses the etiology and management of this rare abnormality.

Mannitol increases cerebral arteriovenous oxygen difference in patients undergoing craniotomy

BACKGROUND

Monitoring the jugular venous oxygen saturation (SjVO2) and cerebral arteriovenous oxygen difference (AVDO2) is valuable in detecting cerebral ischemia. In the present study, we investigated the effect of mannitol on SjVO2 and AVDO2 in patients undergoing craniotomy.

METHODS

We studied 25 ASA class II-III patients undergoing craniotomy. Anesthesia was induced with thiopental, fentanyl and vecuronium. Immediately after induction, a 16-gauge central venous catheter was placed in the internal jugular vein, ipsilateral to the lesion side with cephalic insertion and anchorage in the jugular bulb. Anesthesia was maintained with continuous infusion of fentanyl (10 micrograms/kg/h), 0.5-1% isoflurane in 60% oxygen (oxygen/air) and supplemental dose of vecuronium for muscle relaxation as needed. Samples of arterial and jugular venous blood were obtained for the measurements of SjVO2 and AVDO2 in the following time intervals: (1) normocapnia (PaCO2 38-40 mmHg); (2) hypocapnia (PaCO2 28-30 mmHg); and (3) 30 min after mannitol (0.5 g/kg) infusion.

RESULTS

Hyperventilation resulted in a significant decrease in SjVO2 (96% patients) and increase in AVDO2 (88% patients). Hypocapnia followed by mannitol administration led to a further decrease and increase of SjVO2 and AVDO2 in 72% and 68% patients, respectively.

CONCLUSIONS

Mannitol may produce a further reduction in SjVO2 accompanied by an increase in AVDO2, suggesting a reduction of cerebral blood flow (CBF) during hyperventilation. Therefore, it should be given cautiously in neurosurgical patients under hyperventilation.

Vecuronium dissolved in normal saline exaggerates pain on intravenous injection

BACKGROUND

On some anesthetic occasions, many patients complained of pain at the site of injection when vecuronium, dissolved in normal saline, was administered intravenously. The aims of this study was to compare the incidence of pain on i.v. injection of vecuronium either dissolved in normal saline or in a solvent provided by the pharmaceutical manufacturer.

METHODS

We studied eighty patients of ASA physical status class I-II undergoing elective surgery under general anesthesia. Patients were arranged randomly to receive intravenous 0.1 mg/kg vecuronium dissolved either in solvent (n = 40) or in normal saline (n = 40) through the catheter indwelling in a vein on the dorsum of hand over 5 seconds. Immediately after injection, a nurse was appointed to score the degree of pain. Induction of anesthesia was accomplished with thiopental and fentanyl 30 seconds after vecuronium administration.

RESULTS

Vecuronium dissolved in normal saline induced severe pain more frequently during injection than that dissolved in solvent (27.5% versus 10%). There was no significant difference in pH between these two solutions (3.87 versus 4.08). However, vecuronium dissolved in normal saline showed higher osmolality than that dissolved in solvent (425 +/- 7 mOsm/kg versus 149 +/- 3 mOsm/kg).

CONCLUSIONS

Pain resulting from intravenous injection of vecuronium can be aggravated if normal saline was used as the solvent. Increased osmolality may also be responsible for this phenomenon.

Complete heart block induced by general anesthesia in a patient with suspected conduction system defect: a case report

We report a rare incident of complete heart block occurring after induction of general anesthesia in an apparently fit patient. An external temporary pacemarker was first applied, which was then replaced by isoproterenol infusion, but permanent pacing was required postoperatively. The role of anesthesia as a precipitating factor was discussed. It is suggested that surgical patients suspicious of conduction system defect should be under continuous hemodynamic monitoring with temporary pacing at hand during perioperative period.

Bilateral hydrothorax caused by left external jugular venous catheter perforation

We report a case of bilateral hydrothorax secondary to perforation of the superior vena caval wall, which was caused by a double-lumen central venous catheter used for catheterization of the left jugular vein. A patient undergoing craniectomy developed a right pleural effusion followed by a left hydrothorax 12 hours after the operation. There are several possible explanations for this phenomenon. The horizontal course of the left brachiocephalic vein, heart contraction, mechanical ventilation, changes in patient position, and solutions of high osmolality can promote vascular erosion by the catheter tip. High hydrostatic pressure in the thorax associated with a congenital or an acquired interpleural communication may cause bilateral hydrothorax. We suggest that it is always preferable to cannulate a central vein through the right side. When the left external jugular vein has to be cannulated, an intravascular ECG may be helpful to determine the position of the catheter tip. Chest roentgenogram should be obtained early to confirm catheter position. Furthermore, the distal port of the double-lumen central venous catheter should be used perioperatively for continuous surveillance of the central venous pressure waveform to ensure early warning of venous perforation.

Antagonization of fentanyl-induced muscular rigidity by neurotensin at the locus coeruleus of the rat

We evaluated the interaction between neurotensin (NT) and mu-opioid receptors at the locus coeruleus (LC), using fentanyl-induced muscular rigidity as our experimental index. Adult, male Sprague-Dawley rats anesthetized with ketamine (120 mg/kg, i.p., with 24 mg/kg/h i.v. infusion supplements) were used. Intravenous injection of fentanyl (100 micrograms/kg) consistently promoted a significant increase in the electromyographic activity recorded from the sacrococcygeus dorsalis lateralis muscle. This implied muscular rigidity was appreciably and dose-dependently antagonized by prior intracerebroventricular (i.c.v.) application of NT (15, 30 or 60 nmol/5 microliter). Microinjection of the tridecapeptide (300 or 600 pmol/100 nl) into the bilateral LC produced similar results. This suppressive effect of NT on fentanyl-induced muscular rigidity was antagonized by simultaneously administered NT antiserum (1:80), or partially blocked by its antagonist, (D-Trp11)-NT (300 pmol), but not by normal rabbit serum (1:80). These results suggest that NT may interact with the mu-opioid receptors at the LC, resulting in the suppression of fentanyl-induced muscular rigidity in the rat.

Power spectral analysis of electromyographic and systemic arterial pressure signals during fentanyl-induced muscular rigidity in the rat

We have measured electromyographic (EMG) and systemic arterial pressure (SAP) signals during fentanyl-induced muscular rigidity in adult male Sprague-Dawley rats anaesthetized initially with ketamine 120 mg kg-1 i.p. during controlled ventilation. Fentanyl 100 micrograms kg-1 i.v. induced significant increase in EMG activity, recorded from the sacrococcygeus dorsi lateralis muscle. Power spectral analysis revealed that this was produced by an increase in the root mean square and a decrease in the mean power frequency values of the signals, signifying recruitment and synchronous activation of motor units. Together with transient hypotension and bradycardia, power spectral analysis of the SAP signals demonstrated a reduced but maintained power density of the frequency components that represent respiratory, baroreceptor and vasomotor activities. All these effects were only demonstrated unequivocally in rats maintained by i.v. infusion of ketamine until 10 min before the administration of fentanyl. We conclude that analysis of the temporal alterations in the spectral components of the EMG and SAP signals in rats during mechanical ventilation provides a sensitive method of measuring fentanyl-induced muscular rigidity and the accompanying alterations in haemodynamic variables.

Involvement of G(o) alpha subtype of guanine nucleotide-binding regulatory protein at the locus coeruleus in fentanyl-induced muscular rigidity in the rat

Previous work from our laboratory suggested that locus coeruleus (LC) and the coerulospinal noradrenergic pathway are intimately related to the elicitation of muscular rigidity by fentanyl. The present study attempted to identify the subtype of guanine nucleotide-binding regulatory protein that may participate in this process, using Sprague-Dawley rats anesthetized with ketamine and under mechanical ventilation. Immunofluorescent staining with a polyclonal antiserum directed against a 39-kDa protein that corresponds to the alpha subunit of G(o) revealed the presence of G(o) alpha immunoreactivity in neurons of the LC. Bilateral microinjection of the same G(o) alpha antiserum into the LC also significantly blunted the enhanced electromyographic activity recorded from the sacrococcygeus dorsalis lateralis muscle induced by intravenous administration of fentanyl (100 micrograms/kg). These results suggest that G(o) alpha protein at the LC may participate in the signal transduction process that underlies muscular rigidity induced by high-dose fentanyl.

Spectral characteristics of embolic heart sounds detected by precordial Doppler ultrasound during venous air embolism in dogs

We have studied the frequency spectrum of embolic heart sounds as detected by precordial Doppler ultrasound after injecting air 0.01-0.1 ml into the external jugular vein of anaesthetized dogs (n = 7). At volumes of 0.05 ml and greater, there was a significant increase in both the maximum frequency of the spectrum and the power of those high frequency components to greater than control values. Both changes correlated significantly with the volume of air injected (P < 0.05). With repeated injections of air at 5-min intervals, there was a small increase in the high frequency components in the control signal between injections (P < 0.05). We conclude that such spectral changes could be used to quantify the volume of air in transit through the heart, and to reflect the short-term history of venous air embolism.

Antagonization of fentanyl-induced muscular rigidity by denervation of the coerulospinal noradrenergic pathway in the rat

The present study examined the effect of denervating the coerulospinal noradrenergic pathway on the muscular rigidity elicited by fentanyl in Sprague-Dawley rats anesthetized with ketamine. We demonstrated that the dopamine-beta-hydroxylase-positive nerve terminals arborizing on spinal motoneurons that innervate the sacrococcygeus dorsi lateralis (SCDL) muscle were significantly eliminated by DSP4 treatment. Unilateral microinjection of fentanyl (2.5 micrograms/50 nl) into the locus coeruleus of these animals also failed to evoke discernible increase in the electromyographic activity recorded from the SCDL muscle. These results lend further support for our previous finding that the coerulospinal noradrenergic neurotransmission is critically involved in fentanyl-induced muscular rigidity.

Verification of endotracheal tube misplacement with the colorimetric carbon dioxide detector during anesthesia

The sensitivity and reliability of the colorimetric end-tidal carbon dioxide detector (CETCO2) in verifying misplacement of endotracheal tube in the esophagus were assessed during induction of anesthesia using a conventional capnograph as control. Sixty patients of ASA physical status I and II undergoing elective minor surgery had their anesthesia induced with thiopental sodium (4-5 mg/kg, i.v.). Oral endotracheal intubation facilitated with succinylcholine (1.0 mg/kg, i.v.) was performed by junior residents. The time required for the appearance of discoloration from purple (< 2.5 torr) to tan-hued (3.8-7.6 torr) or yellow (> 15.2 torr) on the CETCO2 (T1) was significantly shorter (3.83 +/- 0.92 second vs. 8.23 +/- 1.14 second, p < 0.01) as compared with the initial display of the ETCO2 waveform on the capnograph (T2). Out of 60 patients esophageal intubation occurred in 6 (10%). Two patients had the color of the CETCO2 changing from purple to tan-hued at the first breath but reverting to purple at the 2nd or 3rd breath. Thus, the sensitivity of CETCO2 was 97.0% (3.0% false positive) if the first breath was chosen as the point of determination. However, if it was set at the 6th breath or yellow was chosen as the color of determination, the sensitivity increased to 100% without either false positive or false negative. In conclusion, the CETCO2 detector is reliable for the detection of correct placement of endotracheal tube during induction of anesthesia, no matter whether Jackson-Rees modification Ayre's T-piece or anesthetic breathing circuit is used for ventilation.

Spinal cord localization of the motoneurons innervating the sacrococcygeus dorsi lateralis muscle and their noradrenergic nerve terminals in rats

We examined in the present study the spinal cord localization of motoneurons innervating the caudal portion of the sacrococcygeus dorsi lateralis (SCDL) muscle and their noradrenergic nerve terminals in Sprague-Dawley rats, using horseradish peroxidase (HRP) and dopamine-beta-hydroxylase (DBH) double-labeling techniques. Retrogradely HRP-labeled motoneurons innervating the caudal part of the SCDL muscle were located ipsilaterally in the ventromedial aspect of the ventral horn (lamina IX) in spinal segments of S2-S4. These cells were polygonal in shape, with an average soma diameter of 37.0 +/- 1.1 microns (mean +/- S.E.M., n = 95) and amounted to 33.6 +/- 5.7 (n = 7) in the horizontal plane. Of note was the presence of abundant DBH-positive nerve terminals arborizing on the soma and dendrites of HRP-labeled motoneurons. These results provided anatomical evidence to further support our previous findings that the coerulospinal noradrenergic neurotransmission is involved in the mediation of fentanyl-induced muscular rigidity.

Modification of tonic-clonic convulsions by atracurium in multiple-monitored electroconvulsive therapy

STUDY OBJECTIVE

To determine the effect of two different doses of atracurium on the modification of tonic-clonic convulsions in multiple-monitored electroconvulsive therapy (MMECT). To compare recovery time and adverse reactions of these doses.

DESIGN

Clinical study. Anesthesiologist was blinded in the evaluation of post-electroconvulsive therapy (ECT) myalgia and other side effects.

SETTING

University-affiliated veterans general hospital.

PATIENTS

Two groups of twelve psychiatric inpatients who suffered from major depression or catatonic-type schizophrenia that failed to respond to tricyclic antidepressant therapy.

INTERVENTIONS

Under single-channel, prefrontal electroencephalographic (EEG) monitoring, patients were given either 0.3 mg/kg or 0.5 mg/kg of atracurium intravenously (IV) after anesthetic induction with methohexital 1 mg/kg i.v.

MEASUREMENTS AND MAIN RESULTS

Evoked electromyographic responses of the adductor pollicis muscle was obtained by train-of-four stimulation of the ulnar nerve at the wrist every 20 seconds. The first twitch depression (T1) of neuromuscular blockade was maintained within 11% to 25% (atracurium 0.3 mg/kg) or 0% to 10% (atracurium 0.5 mg/kg) of control during the entire session of MMECT. Patients pretreated with atracurium 0.5 mg/kg had significantly fewer ECT-induced moderate and vigorous convulsions when compared with patients receiving atracurium 0.3 mg/kg (16.7% vs. 78.4%, moderate; 0% vs. 8.3%, vigorous). However, patients pretreated with atracurium 0.5 mg/kg took a longer time to attain a T4 ratio of 0.5 than did patients receiving atracurium 0.3 mg/kg (9.2 +/- 0.8 minutes vs. 4.3 +/- 0.4 minutes). There was no significant difference between the two groups with respect to cumulative seizure duration or frequency of bradycardia, sialorrhea, postseizure myalgia, nausea, headache, or confusion. No patient in either group recalled any event concerning electroconvulsive shock.

CONCLUSIONS

Whereas full neuromuscular blockade by atracurium 0.5 mg/kg i.v. is very effective in the modification of tonic-clonic convulsions induced by ECT, we suggest that a lower dose of atracurium (0.3 mg/kg i.v.) be used if one needs to ascertain the occurrence of ECT-induced seizures as indicated by minimum peripheral muscle activity at the time of EEG recording during MMECT.