Anesthetic management in a parturient with progressive systemic sclerosis during cesarean section--a case report

This case report concerns a successful Cesarean section (C/S) delivery in an expectant woman affected with progressive systemic sclerosis (PSS) with clinical manifestations of severe pulmonary hypertension (PH), cor pulmonale, severely restrictive ventilatory impairment, pregnancy-induced hypertension (PIH), and esophageal dysfunction under general anesthesia (GA). This is an extremely rare condition in obstetrics and the victim is usually in a great peril of conception, delivery, surgery and anesthesia because of poor pulmonary and cardiac reserves. We herewith reported our experience in two GAs given uniquely to the same patient who was affected with the disorder and discuss the problem.

Anesthetic management in parturients with uterine rupture preoperatively--report of two cases

Uterine rupture is a rare obstetric emergency, and the diagnosis of rupture is not always obvious. High surgical delivery rate today which tends to increase the incidence of the disaster urged us to present this report. Two cases of spontaneous rupture of uterus are described. Case 1 concerns spontaneous rupture of a previously intact uterus; case 2 is a rupture due to placenta percreta. A review relevant to its incidence, risk factors, clinical characteristics, and anesthetic managements is given.

EMLA cream and lidocaine local injection in the treatment of extravenous thiopental injection--a case report

Thiopental extravasation which would cause tissue edema and necrosis in rapid progression by chemical reaction and vascular spasm is a potentially serious complication in anesthesia. Early diagnosis and treatment may bear a favorable outcome. A patient who sustained thiopental extravasation and received local injection of lidocaine and local application of EMLA (Eutectic Mixture of Local Anesthetics) for treatment with excellent results is presented hereunder.

Priming technique accelerates the onset time of mivacurium in children during halothane anesthesia

BACKGROUND

Mivacurium is considered a relaxant suitable for tracheal intubation in children due to its rapid onset. We compared the neuromuscular effects of mivacurium, with and without priming, in children undergoing elective surgery during halothane anesthesia.

METHODS

Forty pediatric patients (2-10 yr, ASA class I) were randomly into 2 groups and studied under halothane anesthesia. The non-priming group (n = 20) received mivacurium 0.25 mg/kg, and the priming group (n = 20) received a priming dose of mivacurium 0.025 mg/kg, followed by an intubating dose of 0.225 mg/kg 3 min later. Thenar Electromyogram responsive to supramaximal train-of-four stimulation of the ulnar nerve at 12 s intervals was used as neuromuscular monitoring.

RESULTS

The onset time in the priming group was significantly faster than in the non-priming group (1.04 min vs. 1.7 min). The mean time from injection of intubating dose to spontaneous recovery to 25%, 50% and 75% twitch were not influenced by priming technique. Side effects, such as cutaneous flushing and hypotension, were unremarkable at this dose in children.

CONCLUSIONS

Priming technique can significantly accelerates the onset of mivacurium in the pediatric patients under halothane anesthesia.

Myocardial protective effect of honokiol: an active component in Magnolia officinalis

Honokiol is an active component of Magnolia officinalis. It was reported to be 1000 times more potent than alpha-tocopherol in inhibiting lipid peroxidation in rat heart mitochondria. In this study, we investigated the in vivo antiarrhythmic and antiischemic effects of honokiol in coronary ligated rats. Male Sprague-Dawley rats were anesthetized with urethane. Honokiol, at dosages of 10(-7) g/kg, 10(-8) g/kg, and 10(-9) g/kg, was administered intravenously 15 min before ligation of the coronary artery. Incidence and duration of ventricular tachycardia and ventricular fibrillation during 30 min coronary ligation were significantly reduced by 10(-7) g/kg honokiol. Ventricular arrhythmia during 10 min reperfusion after the relief of coronary ligation was also reduced. In rats subjected to 4 hours coronary ligation, 10(-7) g/kg, 10(-8) g/kg, and 10(-9) g/kg honokiol significantly reduced the infarct zone. We concluded that honokiol may protect the myocardium against ischemic injury and suppress ventricular arrhythmia during ischemia and reperfusion.

Retrograde ascending aortic dissection diagnosed by intraoperative transesophageal echocardiography

Aortic dissection is a risky but challenging cardiovascular emergency and rapid surgical intervention for life-saving is sometimes inevitable. For detection of aortic dissection, computed tomography, magnetic resonance imaging, aortography all have their advantages but all have their limitations. Transesophageal echocardiography (TEE), which is portable and relatively noninvasive, is a highly sensitive and specific diagnostic tool for evaluation of aortic diseases. We presented a case in which preoperative imaging studies such as MRI and cardiac catheterization were all suggestive of DeBakey's type I aortic dissection. However, it was further proved to be a retrograde ascending aortic dissection during intraoperative TEE imaging study as a retrograde ascending blood flow was demonstrated within the dissected aortic lumen. So the initial operative scheme was changed and sternothoracoabdominal incision was selected for better exposure for one-stage repair of the entire thoracic aorta. Nevertheless, severe intrathoracic adhesion and case to bleed prevented any aggressive intervention to proceed. The operation was called off and the patient was transferred to ICU for further medical treatment.

Magnolol reduces infarct size and suppresses ventricular arrhythmia in rats subjected to coronary ligation

1. Magnolol is an active component of Magnolia officinalis. It is 1000-times more potent than alpha-tocopherol in inhibiting lipid peroxidation in rat heart mitochondria. In the present study, the in vivo antiarrhythmic and anti-ischaemic effects of magnolol in coronary ligated rats were investigated. 2. Male Sprague-Dawley rats were anaesthetized with urethane. Magnolol, at dosages of 10(-7), 10(-8) and 10(-9) g/kg, was administered intravenously 15 min before ligation of the coronary artery. 3. The incidence and duration of ventricular tachycardia and ventricular fibrillation during 30 min coronary ligation were significantly reduced by magnolol. Ventricular arrhythmias during 10 min reperfusion after the relief of coronary ligation were also reduced. 4. In rats subjected to 4 h coronary ligation, 10(-7) and 10(-8) g/kg magnolol significantly reduced infarct size. 5. We conclude that magnolol may protect the myocardium against ischaemic injury and suppress ventricular arrhythmia during ischaemia and reperfusion.

Trilinolein preserves mitochondria ultrastructure in isolated rat heart subjected to global ischemia through antioxidant activity as measured by chemiluminescence

Oxygen-derived free radicals (OFR) have been proposed as the cause of myocardial damage through lipid peroxidation during ischemia and reperfusion. Antioxidants can effectively ameliorate the damage induced by lipid peroxidation. Trilinolein is a triacylglycerol recently purified from the well known traditional Chinese herb Panax pseudoginseng, which has been used in treating circulatory disorders among Chinese for hundreds of years; it has linoleate as the only fatty acid residue in all three esterified positions of glycerol. This chemical has recently been demonstrated to have antioxidant activity by enhanced chemiluminescence. The addition of phorbol myristic acetate (PMA) to medium containing leukocytes produces OFR; this phenomenon was measured by chemiluminescence. Addition of trilinolein to medium containing leukocytes preceding the addition of PMA suppressed the production of OFR. The control value of chemiluminescence of a medium containing leukocytes with addition of PMA was 9.23 +/- 1.19 x 10(3) mV. The most effective concentration of trilinolein was 10(-7) mol/l which decreased the signals to 4.59 +/- 0.02 x 10(3) mV (p < 0.001). The antioxidant effect had a concentration-response curve similar to alpha-tocopherol. After pretreatment for 15 min with trilinolein at a concentration of 10(-7) mol/l in isolated perfused rat heart which had been subjected to 60 min of global ischemia, the integrity of the rat heart mitochondria was preserved as examined under the electron microscope. No swelling of mitochondria occurred and there was good alignment of cristae and absence of amorphous density. Previous experiments have shown that trilinolein can also improve erythrocyte deformability in vitro. Infarct size reduction of about 50% was also demonstrated in in vivo rat heart subjected to 4 h coronary occlusion. The mechanism of myocardial protection, in addition to the antioxidant effect, is suggested as maintaining the membrane fluidity of cardiomyocytes.

Effect of P-6 acupressure on prevention of nausea and vomiting after epidural morphine for post-cesarean section pain relief

BACKGROUND

Nausea and vomiting are important side effects following administration of epidural morphine for post-Cesarean section pain relief. Stimulation of the P-6 (Neiguan) acupoint is a traditional Chinese acupuncture modality used for antiemetic purpose; it has been found to be effective. The aim of this study was to evaluate the antiemetic effect of P-6 acupressure in parturients given epidural morphine for post-Cesarean section pain relief.

METHOD

In a randomized, double-blind and controlled trial, sixty parturients receiving epidural morphine for post-Cesarean section pain relief were investigated. Parturients were allocated to receive the acupressure bands or placebo bands on the P-6 acupoint bilaterally before the administration of spinal anesthesia and were observed over a 48-hour study period.

RESULTS

The incidence of nausea and vomiting was significantly decreased from 43% and 27% in the control group, to 3% and 0% in the acupressure group, respectively (P < 0.05).

CONCLUSION

The results demonstrate that prophylactic use of acupressure bands bilaterally on the P-6 acupoint can significantly reduce incidence of nausea and vomiting after epidural morphine for post-Cesarean section pain relief.

The effect of intrathecal bupivacaine with combined fentanyl in cesarean section

BACKGROUND

The use of neuraxial opioids has gained popularity over the last few years; they may augment the analgesia produced by the local anesthetic through direct binding with the specific spinal receptors. Morphine, a lipophobic opioid, may not be optimal as an intrathecal drug for intraoperative analgesia because of its slow onset. The lipophilic opioid, fentanyl for instance, if administered intrathecally, its onset is fast and many of its merits by virtue of its lipophilic property may be seen intraoperatively.

METHODS

Seventy five healthy pregnant women who sustained cesarean section under spinal anesthesia were assessed in a randomized fashion. The spinal anesthetic used was 0.5% hyperbaric bupivacaine. Patients were divided into 5 groups, 15 in each group. Fentanyl 0 (Group I), 7.5 (Group II), 10 (Group III), 12.5 (Group IV) and 15 (Group V) micrograms was respectively added to normal saline to make a total volume of 0.3 ml, which was then added to bupivacaine and administered to patients in a randomized fashion. The effect of analgesia, vital signs and side effects were observed every 5 min during operation and every 30 min after operation.

RESULTS

It was disclosed that all patients in group V and IV had excellent analgesia intraoperatively, while only 33.3% patients in the control group had an analgesia which was qualified as excellent. Complete analgesia (time from injection to first report of pain) also lasted longer in group IV (201.3 +/- 16.4 min, mean +/- SEM) and group V (210.3 +/- 18.6 min) compared with group I (118.9 +/- 10.4 min). The duration of effective analgesia (time from injection to first parental opioid) was increased with the dose of intrathecal fentanyl above 12.5 micrograms (293 +/- 22.4 min). Both complete analgesia and effective analgesia were not significantly different between group IV and group V. Pruritus was the most common side effect. The incidence of shivering decreased significantly in group IV & V as compared with control group.

CONCLUSIONS

The combination of bupivacaine with a dose of fentanyl as low as 7.5 micrograms did not produce actual clinical effects. As the dose of fentanyl was increased to 12.5 micrograms or 15 micrograms the quality of surgical analgesia was better and the postoperative analgesia lasted longer. It seemed that the clinical effect might reach its ceiling at the dose of 12.5 micrograms. Pruritus was the most common side effect, but it was mild.

Evaluation of the hemostatic clot formation of newborns by Sonoclot coagulation analyzer

BACKGROUND

Sonoclot Analyzer has been widely used for more than five years in The United States to evaluate the platelet function and coagulation in adult. No clinical trial with the Analyzer has been reported in the field of pediatrics. The present study was aimed to evaluate the efficacy of the Sonoclot Analyzer for urgent determination of platelet function and coagulation in newborns.

METHODS

Venous blood samples were drawn from the umbilical vein in 70 healthy newborns, and from the median cubital vein in 70 healthy adult volunteers, between 24 to 40 years of age, for control. DP2951 Sonoclot II Surgical Analyzer with graphic printer was used to evaluate the hemostatic clot formation.

RESULTS

Results demonstrated that Sono ACT (activated coagulation time), peak time and retraction time increased by 36%, 66% and 70% respectively in newborns, while clot rate decreased by 69% in comparison with that of these adults.

CONCLUSIONS

The results of using the Sonoclot Analyzer in this study confirmed other previous investigation that platelet function and coagulation are altered in newborns when compared with that of adults. The Sonoclot Analyzer is a simple device, easy to perform; It requires only small amounts of blood sampled (0.4 ml), and provides a rapid coagulation function for newborns.

Trilinolein reduces infarct size and suppresses ventricular arrhythmias in rats subjected to coronary ligation

Trilinolein, a triacylglycerol with linoleic acid as the only fatty acid residue in all esterified positions of glycerol, was previously found to improve erythrocyte deformability in vitro. In this study, the in vivo antiarrhythmic and anti-ischemic effects of trilinolein in coronary ligated rats were investigated. Male Sprague-Dawley rats were anaesthetized with urethane. Trilinolein, at dosages ranging from 10(-11) to 10(-7) g/kg, was administered intravenously 15 min before ligation of coronary artery. Also, the effect of trilinolein on arrhythmia was studied by ligating the coronary artery for 30 min, then reperfusing myocardium for 10 min. During the 30-min ischemia, trilinolein reduced not only the number of ectopic beats but also the incidence rate and duration of ventricular tachycardia. At 10(-7) g/kg, trilinolein completely suppressed all ventricular arrhythmias. Ventricular arrhythmias during 10 min reperfusion were also reduced by trilinolein at similar dosages. Furthermore, the effect of trilinolein on infarct size was evaluated by occluding the coronary artery for 4 h before the infarct zone was stained and weighed. In rats subjected to 4 h coronary ligation, pretreatment with 10(-7) g/kg trilinolein at 15 min prior to the coronary ligation significantly reduced infarct size. Trilinolein may protect myocardium against ischemic injury and suppress arrhythmia during ischemia and reperfusion.

The interaction of the neuromuscular effects between mivacurium and esmolol in rats

BACKGROUND

To study the neuromuscular interaction between mivacurium and esmolol, we compared the neuromuscular actions of the ED90 dose of mivacurium both in the absence and presence of esmolol infusion.

METHODS

Twelve rats were anesthetized with urethane. Train-of-four stimulation was applied every 12 s to the sciatic nerve, and the electromyogram (EMG) response of the anterior tibial muscle was measured.

RESULTS

The ED50 and ED90 of mivacurium in rats were 144 +/- 7.3 micrograms/kg and 197 +/- 7.7 micrograms/kg, respectively. The maximal EMG depression produced by ED50 of mivacurium decreased significantly with esmolol treatment from 88.2 +/- 2.7% to 83.1 +/- 2.6% after esmolol infusion (p < 0.05). The onset time for 75% EMG depression was much shorter for control (44 +/- 6.3 s) than that of esmolol treatment (78.2 +/- 2.4 s; p < 0.05). There was no difference between their duration.

CONCLUSIONS

The results of this study demonstrated that esmolol does not potentiate the neuromuscular effect of mivacurium but antagonize the maximal neuromuscular block and decrease its onset time in rats.

The physiological effect of CO2 pneumoperitoneum in pediatric laparoscopy

BACKGROUND

The physiological effect of CO2 pneumoperitoneum during laparoscopy is a great concern of the anesthesiologists. Its effect in pediatric laparoscopy has not been previously reported. The purpose of this study was to examine the physiological alteration of pediatric patients during CO2 pneumoperitoneum.

METHODS

One hundred and twenty six children aged from 11 mon to 13 yr undergoing laparoscopic inguinal exploration were divided into three groups based on age orientation: group I comprising 40 children with age from 11 mon to 2 yr; group II 46 children with age between 2 to 5 yr; and group III 40 children aged from 5 to 13 yr. All patients received endotracheal anesthesia with halothane-N2O in 50% O2 and atracurium for muscle relaxation. Respiration was controlled by an Ohmeda 7000 ventilator with constant minute ventilation to maintain baseline end-tidal CO2 tension (PETCO2) between 32-33 mmHg. After anesthesia, CO2 was insufflated into the peritoneal cavity via the opened hernia sac. The intraabdominal pressure exerted by CO2 was 10 mmHg and the duration of pneumoperitoneum and laparoscopy was 15 min. We recorded airway pressure, PETCO2, body temperature, blood pressure, heart rate, heart rhythm, and oxygen saturation simultaneously at 1 min interval before, during, and after laparoscopy.

RESULTS

The airway pressure and PETCO2 showed significant increases during laparoscopy (15-18% and 18-20% respectively) in all cases, but the percentage of increases were not significantly different among groups. However, the PETCO2 change in terms of time lag were different between groups: (1) the time lag from CO2 insufflation to the emergence of PETCO2 change (latent period) was respectively 0.7 +/- 0.1 (mean +/- SD) min in group I, 0.9 +/- 0.2 min in group II and 1.5 +/- 0.2 min in group III (p < 0.05); (2) the PETCO2 change from baseline to a plateau (ascending period) was respectively 4.2 +/- 0.6 min in group I, 6.3 +/- 1.0 min in group II and 9.1 +/- 1.1 min in group III (p < 0.05); (3) the PETCO2 decline from plateau to baseline after CO2 deflation (descending period) was respectively 6.2 +/- 0.5 min in group I, 8.3 +/- 0.8 min in group II and 12.0 +/- 1.3 min in group III (p < 0.05). The body temperature and hemodynamics including blood pressure, heart rate, heart rhythm, oxygen saturation were not significantly changed during laparoscopy in all groups.

CONCLUSIONS

The changes of PETCO2 during laparoscopy did not influence the hemodynamic stability in our study. The younger children give a faster reaction time of PETCO2 change after CO2 insufflation than do the older children which may be related to the variation of physiological exhibition at different state of development.

Transesophageal indirect atrial pacing for open-heart surgery in children

BACKGROUND

Transesophageal atrial pacing (TAP) has been successfully applied for clinical use for more than 30 years. Not only for cardiac pacing, or diagnosis and treatment of rhythmic disturbance but also for assessing the presence and severity of coronary artery disease and maintaining adequate heart rate can TAP provide satisfactory effect. In this study we applied TAP on children undergoing the cardiac surgery to evaluate its efficacy and side effects during such major surgery.

METHODS

Twenty-four children (15 M and 9 F) undergoing open-heart surgery with informed consents were included in this study. After induction of anesthesia the bipolar pacing electrode (Tapcath, Arzco Medical Electronics) was inserted into esophagus through the nose until the ideal site for atrial pacing was found by monitoring the esophageal ECG lead (lead I), and then initiation of atrial pacing was performed by applying the transesophageal cardiac stimulator (Arzco Medical Electronics). Continuous ECG, arterial blood pressure and central venous pressure (CVP) were simultaneously monitored and recorded. Patient's height, inserted length of the pacing electrode, current and pulse duration for effective atrial pacing were also recorded.

RESULTS

The effective rate for initiating sinus tachycardia (atrial capture) by applying TAP was 79.2% (19/24) in our study. For effective atrial pacing the average current was 11.6 +/- 2.4 mA, the average stimulus pulse duration was 4.8 +/- 1.0 ms, and the average inserted length of bipolar electrode was 19.1 +/- 2.2 cm.

CONCLUSIONS

TAP method can be applied satisfactorily in children undergoing cardiac surgery. If urgent cardiac pacing must be applied in these patients TAP would be a choice.

[Mediastinal mass and anesthesia in children--a case report]

A three-year-old girl with mediastinal mass received right exploratory thoracotomy was reported. The mediastinal mass of this patient occupied the whole right lung and compressed the right main bronchus as confirmed by X-ray and CT of the chest. For mediastinal mass surgery, several fatal hazards can happen during induction of anesthesia, maintenance and even the post-operative period. The two main hazards are trachobronchial obstruction and cardiovascular collapse. We presented our experience of this case including preparation, planning, induction technique, maintenance of anesthesia and postoperative care. We hoped that this can help others to minimize accidents when they handle patients with similar conditions.

[A comparison between the pain relief effect of electroacupuncture, regional never block and electroacupuncture plus regional never block in frozen shoulder]

BACKGROUND

Frozen shoulder is a kind of spontaneous, progressive peri-arthritis over the shoulder joint. The etiology is not yet clear. Traditional treatments for frozen shoulder included conservative medical therapy, physical therapy, nerve block and acupuncture and so on. The purpose of our study is to determine the pain relief effect of electroacupuncture (EAP), regional nerve block (RNB) and the combination of EAP + RNB for frozen shoulder.

MATERIALS & METHODS

One hundred and fifty patients with fresh frozen shoulder were, randomly divided into 3 groups. Group I patients (n = 50) had RNB with stellate ganglion block and suprascapular nerve block by 1% xylocaine 10 ml. Group II patients (n = 50) had EAP with local acupoint--Chien-Yu, Chien-Ching, Chien-Nei-Ling, Ah-Shih Hsueh treatment and Group III (n = 50) patients had RNB+EAP performed with acupuncture first, then followed by the regional nerve block. Six vectors of movements were checked in all methods. Four graded Bromage score was used for pain assessment, Grade 1 means complete painless; Grade 2 means slight pain (i.e. pain on motion); Grade 3 means moderate pain (i.e. pain on silence); Grade 4 means severe pain (i.e. need analgesics). The range of shoulder joint was also recorded. Patients were requested for second treatment if pain recurred. The onset (time from injection to maximal pain relief), duration (time from injection to grade 3) Bromage score and side effects were recorded.

RESULTS

The results showed that the combined EAP and RNB method had significant high pain control quality, longer duration, and better range of movement of the shoulder joint than that of EAP or RNB performed alone.

Neuromuscular interactions between succinylcholine and esmolol in the rat

To study the neuromuscular interactions between succinylcholine (Sch) and esmolol, we determined the dose-response relationship of Sch and the neuromuscular actions of the 3xED90 dose of Sch, both prior to and following esmolol pretreatment. Twenty rats were anaesthetized with urethane. Train-of-four stimulation was applied every 12 s to the sciatic nerve, and the electromyogram (EMG) of the tibialis anterior muscle was measured. The results showed that the potency of Sch decreased with esmolol pretreatment. The ED50 of Sch increased significantly, from 191 ug/kg to 227 ug/kg after esmolol infusion, p < 0.05. The duration of EMG depression achieved by the 3xED90 dose of Sch decreased significantly with esmolol pretreatment (12 min vs 14 min p < 0.05), and also the onset time was significantly longer (43 sec vs 28 sec, p < 0.05). There were no significant difference between groups with regard to the maximal block or recovery index. The results of two methods of study demonstrated that the pharmacological interaction between Sch and esmolol is antagonistic instead of potentiating.

Neuromuscular interactions between suxamethonium and magnesium sulphate in the cat

In order to study the neuromuscular interactions between suxamethonium and magnesium sulphate (MgSO4), we have determined the dose-response relationship of suxamethonium and the neuromuscular actions of 1.25 x ED50 dose of suxamethonium, both before and after pretreatment with MgSO4. We have also compared the effect of 1.25 x ED50 dose of suxamethonium in the absence and in the presence of 50% neuromuscular block, established previously by infusion of MgSO4. Twenty-one cats were anaesthetized with urethane. Train-of-four stimulation was applied every 12 s to the sciatic nerve and the force of contraction of the tibialis anterior muscle was measured. The potency of suxamethonium decreased in each instance with pretreatment with MgSO4. The ED50 of suxamethonium increased significantly from mean 21.0 (SEM 1.9) micrograms kg-1 before MgSO4 to 25.6 (2.3) micrograms kg-1 after MgSO4 60 mg kg-1 and to 26.6 (2.2) micrograms kg-1 after MgSO4 90 mg kg-1 (P < 0.05). Twitch depression produced by 1.25 x ED50 dose of suxamethonium decreased significantly with MgSO4 pretreatment, from 76.7 (2.6)% before MgSO4 to 61.7 (6.4)% after MgSO4 60 mg kg-1 and 48.7 (7.5)% after MgSO4 90 mg kg-1 (P < 0.05). With stable 50% neuromuscular block, established previously by infusion of MgSO4, the 1.25 x ED50 dose of suxamethonium produced more twitch augmentation (133 (6.3)% vs 108.3 (1.3)%; P < 0.05) and less twitch depression (31.6 (9.6)% vs 74.1 (0.6)%, P < 0.05) than in the absence of MgSO4. The results of all three methods demonstrated that the pharmacological interaction between suxamethonium and magnesium was antagonistic.

Trilinolein improves erythrocyte deformability during cardiopulmonary bypass

The in vitro effect of trilinolein, a triglyceride with linoleic acid as the major fatty acid residue in the esterified positions of glycerol, on erythrocyte deformability was studied in blood samples collected from 12 patients before and after cardiopulmonary bypass (CPB). Erythrocyte deformability was measured with a filtration method and expressed as red cell filtration rate (RFR). RFR was reduced after CPB and the reduction was time dependent. Trilinolein at a concentration of 10(-7) M significantly reversed the CPB-induced reduction of RFR when it was mixed with blood samples collected 30, 60 and 90 min from the start of CPB. This study confirmed the effect of CPB on erythrocyte deformability and showed that this damage could be significantly improved by mixing blood with trilinolein.

Refractoriness of neuromuscular transmission: determination by computer subtraction of neurally evoked compound electromyograms

Shortly after elicitation of a muscle response by supramaximal stimulation of its motor nerve, there exists a period of refractoriness of neuromuscular transmission when a second stimulation elicits only a submaximal response or no response at all. Many anaesthetics and neuromuscular blocking and facilitatory drugs change the refractoriness of neuromuscular transmission. Measurement of this refractoriness may improve our understanding of the neuromuscular actions of these drugs and be useful in differential diagnosis. However, the neuromuscular refractory periods (RP) are difficult to measure, and the unavailability of normal values renders accurate determination of drug effects impossible. Based on an existing technique of digitization and time expansion of the neurally evoked compound electromyogram (ncEMG), we developed a computer programme of waveform subtraction, and determined in nine normal awake volunteers the various interstimulus intervals when neuromuscular transmission was refractory (RP0), 3/4 refractory (RP.25), half refractory (RP.5), 1/4 refractory (RP.75) or non-refractory (RP1). We confirmed our hypotheses that computer-based waveform subtraction of the digitized ncEMG is a feasible and necessary technique for the accurate determination of the RPs of neuromuscular transmission, and report that the normal values in humans are: RP0 = 1.0 +/- 0.1, RP.25 = 1.3 +/- 0.3, RP.5 = 1.9 +/- 0.3, RP.75 = 2.9 +/- 0.5, and RP1 = 6.6 +/- 1.9 ms (mean +/- SD), respectively, in the ulnar nerve-first dorsal interosseous muscle model.

Electrophysiological actions of alfentanil: intracellular studies in the rat locus coeruleus neurones

1. The electrophysiological effects of alfentanil on 156 neurones of the rat locus coeruleus were investigated by use of intracellular recordings from the in vitro brain slice preparation. 2. Bath application of alfentanil (5-100 nM) reversibly decreased the firing rate of all neurones tested in a dose-dependent manner, with an IC50 4.1.nM. 3. Based on inhibition of the spontaneous firing rate, alfentanil was 22 times more potent than morphine. 4. At 100 nM, alfentanil produced a complete inhibition of firing of all neurones tested (n = 62); the inhibition was accompanied by a membrane hyperpolarization 17.0 +/- 0.8 mV (range 6.1-30.3 mV, n = 62) and a reduction in input resistance 26.4 +/- 1.7% (range 6.5-53%, n = 51). 5. The effects of alfentanil were antagonized by naloxone, with a dissociation equilibrium constant of 2.7 +/- 0.4 nM (n = 6). 6. The reversal potential for the alfentanil-induced hyperpolarization was -110 +/- 2 mV (n = 9), which is approximately the potassium equilibrium potential. 7. The alfentanil-induced hyperpolarization was blocked by caesium chloride and barium chloride. 8. These results indicate that alfentanil binds to mu-opioid receptors on the cell membrane of neurones of the locus coeruleus. This leads to opening of the inward-going rectification potassium channels, resulting in the observed hyperpolarization of the membrane.

A clinical assessment of desflurane anaesthesia and comparison with isoflurane

In 48 randomly assigned ASA I adult patients undergoing elective orthopaedic procedures, we compared the pharmacodynamics of desflurane (DF) and isoflurane (IF), and their pharmacokinetics during rapid induction of deep anaesthesia (via face mask, to 1.5-2 MAC, after thiopentone), maintenance of anaesthesia at 1.25 MAC, and emergence therefrom. During induction, laryngeal reactions ranging from mild crowing to laryngospasm occurred more frequently with DF than with IF (15/24 DF, 5/24 IF; P < 0.05) and was more severe (9/24 DF, 1/24 IF, excluding the mildest form, P < 0.05). As a result, induction of anaesthesia was not accomplished faster with DF, in spite of a faster equilibration between exhaled and inhaled concentrations. Emergence from DF was more rapid and less complicated by delirium. Pharmacokinetically, the exhaled concentration of DF reached 90% of the inhaled concentration within five minutes of induction, whereas that of IF lagged behind and remained 25% below the inhaled concentration (1 vs 1.34 +/- 0.05) even one hour after induction. Premature ventricular contractions did not occur in any patient even during periods of difficulty with the airway and oxygen desaturation. It is concluded that DF is a safe anaesthetic, pharmacokinetically superior to IF but clinically inferior for induction of anaesthesia via a face mask. Because of the fast equilibration, the exhaled concentration of DF can be controlled more precisely by the dial setting of the vaporiser.

[The effects of intravenous and intraperitoneal dexamethasone treatment on vecuronium in the anesthetized rat]

It is fairly widespread clinical practice to administer large doses of corticosteroids to patients in cases of shock; doses of hydrocortisone as high as 50 mg/kg given intravenously have been proposed and used; especially in cases of Myasthenia Gravis. Its effects on neuromuscular transmission is not yet fully understood. In order to determine the mechanism of this interaction, we undertook this investigation. The neuromuscular effects of Dexamethasone, at single dose of 100 micrograms/kg intravenously or intraperitoneally, were studied by electromyographical quantification of the tibialis-anterior muscle evoked by sciatic nerve stimulation in 21 rats anesthetized with Urothane 1.25 g/kg given intraperitoneally. Intravenous Dexamethasone (n = 7) had no obvious effect on the blockade of tibialis-anterior muscle produced by the cumulative doses of Vecuronium (ED50 = 180 +/- 24 micrograms/kg), as compared with the control group (n = 7) (ED50 = 201 +/- 18 micrograms/kg). In contrast, intraperitoneal Dexamethasone (n = 7) produced a significant (P < 0.05) change (ED50 = 240 +/- 28 micrograms/kg), when compared with control group. The results showed that in tibialis-anterior muscle sciatic nerve preparation of rats, intraperitoneal Dexamethasone had antagonism effect on Vecuronium. However, there was no obvious influence on Vecuronium in the intravenous Dexamethasone group.