Effects of succinylcholine on the recovery of block produced by mivacurium in rats.

This study investigates the effects of succinylcholine on the recovery of neuromuscular blockade produced by mivacurium in rats. In 48 anesthetized animals, the sciatic nerve was prepared and stimulated, and twitches of the flexor digitorum longus muscle were recorded. Animals were randomly divided into four groups (n = 12 each): bolus dose of succinylcholine 0.1 mg/kg (GroupSch), bolus dose of mivacurium 0.15 mg/kg (GroupMiv), bolus dose of mivacurium 0.15 mg/kg, followed by succinylcholine 0.1 mg/kg at 25% neuromuscular recovery from mivacurium (Group-MivSch(25)), or bolus dose of mivacurium 0.15 mg/kg, followed by succinylcholine 0.1 mg/kg at 75% neuromuscular recovery from mivacurium (GroupMivSch(75)). Onset times of neuromuscular block following succinylcholine in mivacurium-treated groups were comparable and significantly shorter than in GroupSch (p < 0.001). Duration of action of succinylcholine was more prolonged when it was given in the presence of deeper neuromuscular block induced by mivacurium (p < 0.001 in GroupMivSch(25) and p < 0.01 in GroupMivSch(75)). Our results suggest that, in rats, mivacurium administration has a significant potentiating effect on a subsequent succinylcholine-induced neuromuscular block.

Ultrastructure of the rat hippocampus after isobaric respirative hyperoxia.

After exposing rats to an environment of isobaric hyperoxia, the ultrastructural alterations of the hippocampus were studied. No major alterations were found in the nerve cells. Of importance was the moderate osmiophilia and the spindle-like transformation of the mitochondria. Vacuolated synapses and neuraxons were found, containing amorphous material. Astrocytic perivascular end feet were found vacuolated in many places. Many endothelial cells of the capillaries presented high osmiophilia, which sometimes prevented structural details. Quantitatively, the findings were proportionally related to the time of exposure in the pure oxygen atmosphere (24, 48 and 65 hours).

Hypoxic pretreatment protects against neuronal damage of the rat hippocampus induced by severe hypoxia.

The present study investigates whether under conditions of successive hypoxic exposures pretreatment with mild (15% O(2)) or moderate (10% O(2)) hypoxia, protects hippocampal neurones against damage induced by severe (3% O(2)) hypoxia. The ultrastructural findings were also correlated with regional superoxide dismutase (SOD) activity changes. In unpretreated rats severe hypoxia induced ultrastructural changes consistent with the aspects of delayed neuronal death (DND). However, in preexposed animals hippocampal damage was attenuated in an inversely proportional way with the severity of the hypoxic pretreatment. The ultrastructural hypoxic tolerance findings were also closely related to increased regional SOD activity levels. Thus the activation of the endogenous antioxidant defense by hypoxic preconditioning, protects against hippocampal damage induced by severe hypoxia. The eventual contribution of increased endogenous adenosine and/or reduced excitotoxicity to induce hypoxic tolerance is discussed.

Clonidine versus ketamine to prevent tourniquet pain during intravenous regional anesthesia with lidocaine.

BACKGROUND AND OBJECTIVES: Both clonidine and ketamine have been found to prolong the action of local anesthetics through a peripheral mechanism. Our study compares the efficacy of a low dose of clonidine or ketamine separately added to intravenous regional anesthesia (IVRA) with lidocaine to prevent tourniquet pain. METHODS: We conducted a prospective randomized double-blinded study in 45 patients undergoing hand or forearm surgery, with anticipated duration exceeding 1 hour under IVRA. Proximal cuff inflation of a double tourniquet was followed by administration of 40 mL of lidocaine 0.5% and either saline, 1 microg/kg clonidine, or 0.1 mg/kg ketamine. When anesthesia was established, the inflation of the proximal and distal cuff was interchanged. Thereafter, tourniquet pain was rated on a visual analog scale (VAS) every 10 minutes. Intraoperatively, boluses of 25 microg fentanyl were provided for tourniquet pain treatment when required, and total fentanyl consumption was recorded. RESULTS: Patients receiving plain lidocaine persistently reported the highest pain scores among groups (P <.001) 20 minutes after distal cuff inflation. Differences between the groups with additional treatment were noted 50 minutes after distal cuff inflation and until the end of the observation, with significantly lower VAS ratings (P <.001 to P <.01) in ketamine-treated patients. Total fentanyl consumption was significantly decreased by ketamine (70.00 +/- 25.35 microg) or clonidine (136.67 +/- 39.94 microg) compared with the plain lidocaine group (215.33 +/- 52.33 microg) (P <.001 between all groups). CONCLUSIONS: The addition of clonidine 1 microg/kg or ketamine 0.1 mg/kg to lidocaine for IVRA delays the onset of unbearable tourniquet pain and decreases analgesic consumption for tourniquet pain relief, although ketamine has a more potent effect.

Pancuronium effect on the neuromuscular function of hypoglycemic rats.

An expected response in a hypoglycemic patient to a muscle relaxant formed the basis for the research presented in this study. There was no information available in the accessible literature and references gave no data on this subject. But because perioperative hypoglycemia is not unusual, we scheduled this experimental work. Four groups of 6 white adult Wistar albino rats were used in the study. Group A was the normoglycemia control group, with blood glucose levels of 80-120 mg/dl. Groups B, C and D were made hypoglycemic by i.v. injection of insulin 1 IU/100 g b.w. Blood glucose levels were reduced to 50% of the control values in hypoglycemic animals, which were sacrificed 40 min later. Phrenic nerve-hemidiaphragm preparations were placed in a 100 ml bath containing Paradelis-Zaimis solution, 37 degrees C, pH 7.2, aerated with O2/CO2:95/5%. After stabilization and recording of neuromuscular activity, pancuronium bromide was administered in doses of 1.5 x 10(-9) M in groups A and B, 3 x 10(-9) M in group D. Statistical analysis between A-B, A-C, A-D groups was done with Student's paired t test. Results showed that under hypoglycemic conditions the amount of pancuronium bromide needed for complete neuromuscular blockade was 2.5-fold greater than that needed in normoglycemic conditions. These findings suggest that the integrity of the neuromuscular junction is altered during hypoglycemia.

Neuromuscular blocking activity of aminoglycoside antibiotics.

The aminoglycoside antibiotics possess neuromuscular blocking activity; the potency of those antibiotics tested appears to be as follows: gentamicin greater than streptomycin greater than amikacin greater than sisomicin greater than kanamycin = tobramycin greater than kanendomycin = dibekacin. The neuromuscular blockade produced by these antibiotics is not reversed by neostigmine, whereas it is reversed by calcium. Calcium not only has the ability to restore the neuromuscular transmission but also to exert protective action against the neuromuscular blocking activity of aminoglycoside antibiotics; these antibiotics are also potentially capable of interacting with non-depolarizing muscle relaxant drugs (d-tubocurarine, pancuronium) or propranolol, a beta-adrenergic receptor blocking agent. This interaction results in respiratory depression and/or prolonged apnoea. Our findings lead to the assumption that amino-glycoside antibiotics are involved in the process of acetylcholine release by nerve impulses, antagonizing calcium ions.

Effect of succinylcholine on the neuromuscular junction of hypoglycemic rats.

The aim of the present study was to investigate the effect of neuromuscular blocking drugs on the neuromuscular junction in hypoglycemic rats. Three groups of 6 white adult Wistar albino rats were used. Group A consisted of the control animals with normal blood glucose levels ranging between 80-120 mg/dl. Groups B and C consisted of animals which were made hypoglycemic by intravenous injection of insulin at a dose of 1 iU/100 g b.w. In this way, their blood glucose levels were reduced to 50% of the blood glucose levels of the control animals. The test animals (groups B and C) were sacrificed 40 min after the injection of insulin and the preparations of the phrenic nerve-hemidiaphragm were placed into a 100 ml_bath containing Paradelis-Zaimis solution. The bath was aerized with O2/CO2:95/5%, it's temperature was maintained at 37 degrees C and it's pH at 7.2. After the stabilization of the system and the recording of neuromuscular activity, succinylcholine was administered (1.5 x 10(-8) M in groups A and B and 3.0 x 10(-8) M in group C). For the statistical analysis of the results, student's t-test was used. According to our results, there is a statistically significant difference (with p < 0.02 being considered significant) between the n.bl/t% (magnitude of final neuromuscular blockage) values of the animals of groups B and C and those of the animals of group A. We also observed a statistically significant difference (with p < 0.001 being considered significant) between the t (time required for complete blockage in groups A and C or time required for stabilization of blockage in group B) values of the animals of groups B and C and those of the animals of group A. On the other hand, there was a statistically significant difference (p < 0.02 being considered significant) in the n.bl/5'% (magnitude of neuromuscular blockage 5 min after the administration of succinylcholine) values only between the animals of group A and B. Our results indicate that under hypoglycemic conditions, the amount of succinylcholine required for final neuromuscular blockage is two times greater than that needed under normal glucose blood levels. This finding suggests that the integrity of the neuromuscular junction is altered during hypoglycemia.

Monitoring the onset of neuromuscular blockade with double burst stimulation (DBS).

The present study was undertaken to evaluate the suitability of the DBS mode in the determination of the proper time to perform tracheal intubation following cisatracurium muscle relaxation. The DBS3.3 pattern was administered to the ulnar nerve at the wrist in 45 patients paralyzed with cisatracurium 0.15 mg.kg-1 and tracheal intubation was attempted immediately after the disappearance of both palpable contractions of the adductor pollicis. Intubation conditions were assessed with a standard four-graded scoring system and the onset time of the relaxant was determined. Forty-two patients (93%) exhibited acceptable intubation conditions as soon as both responses to DBS were absent and the estimated apparent onset time, according to the stimulation mode applied, was 114.68 +/- 13.2 sec. Our data suggest that disappearance of both palpable responses to DBS3.3 may be used as an accurate predictor of acceptable intubation conditions, following nondepolarizing relaxants such as cisatracurium.

Ultrastructural changes of the myocardial and striated muscle following a challenge of normobaric hyperoxia: the protective effects of alpha-tocopherol.

Normobaric hyperoxia has known deleterious effects on survival, presumably due to the generation of superoxide anion and hydrogen peroxide. To investigate the anatomical substrate of the effect of normobaric hyperoxia on the myocardial and striated muscles and the protective effect, if any, of alpha-tocopherol (vitamin E) on these tissues, we administered 95-99% O2 to adult male Wistar rats for 24, 48, 60 and 72 h. The animals were divided into four groups: 1) control I: six rats which breathed room air were used as controls for the ultrastructural studies; 2) control II: 10 rats which breathed 95-99% of O2 for up to 72 h were used as controls for arterial pressure, blood gases/pH, PvO2 and Hb measurements; 3) group A: hyperoxia: 24 rats divided into four subgroups according to the time of exposure to hyperoxia, A24, A48, A60, A72; and 4) group B: alpha-tocopherol/hyperoxia: 24 rats treated with alpha-tocopherol, 15 mg/kg/day, for 14 days before the beginning and throughout the period of hyperoxia, were divided into four subgroups (B24, B48, B60, B72) according to the time of exposure to hyperoxia. Our results showed that: 1) up to the 60th hour, arterial pressure (MAP) was satisfactory; PaO2 > 280 mmHg; PaCO2, pH and Hb were within normal limits; 2) ultrastructural studies of the myocardial apex, the diaphragm and the quadriceps femoris showed dilatation of the sarcoplasmic reticulum/T-tubuli system, swelling of mitochondria, and structural derangement of myofibrils, in particular in the z-bands. The findings were proportionally related to the time of exposure of hyperoxia. They were also more intensely shown on myocardial and diaphragmatic fibers in group A; 3) the survival time (mean +/- SD) was 63.8 +/- 2.5 h in group A and 68.9 +/- 3.8 h in group B. These results suggest that normobaric hyperoxia exerts a cytotoxic effect on the myocardial and striated muscle fibers and that the administration of alpha-tocopherol may delay or change the development of oxygen toxicity.

Interaction of aminoglycoside antibiotics and calcium channel blockers at the neuromuscular junctions.

Aminoglycoside antibiotics (mmol.l-1) gentamicin (0.74), streptomycin (1.02), netilmicin (1.24), amikacin (2.23), sisomicin (2.74), dactimicin (2.75), kanamycin (3.43), kanendomycin (3.45), tobramycin (3.53) and dibekacin (4.35) produce a complete neuromuscular blockade at the isolated phrenic nerve-hemidiaphragm preparation of the rat, which is only reversed by calcium chloride. On the other hand, verapamil (2.04 mmol.l-1), a calcium channel blocker, also produces a complete neuromuscular blockade at the above preparation which is reversed by calcium chloride. Aminoglycoside antibiotics are potentially capable of interacting with verapamil and produce a complete neuromuscular blockade at concentrations significantly reduced. The neuromuscular blockade which is produced by the concurrent administration of the aminoglycoside antibiotics and verapamil is obtained with the usual therapeutic blood concentrations of the individual agents. Furthermore, the neuromuscular blockade which is produced during verapamil-aminoglycoside antibiotics interactions is completely reversed after calcium chloride administration. The mechanism by which aminoglycoside antibiotics and verapamil produce neuromuscular blockade must be the same. Both classes of drugs interfere with calcium ions movements through the calcium channels of the membrane of the motor nerve-endings inhibiting acetylcholine release at the synaptic cleft. The interaction of aminoglycoside antibiotics and calcium channel blockers is of clinical significance because when these agents are given concurrently during the perioperative period they may lead to respiratory depression or prolonged apnoea. These respiratory disturbances can be managed by slow intravenous infusion of 50 to 200 mg of calcium gluconate.

Demographic profile and outcome analysis of pediatric intensive care patients.

BACKGROUND: Demographic profile and outcome can vary in pediatric intensive care unit (PICU) patients. The aim of our study was to analyze demographic profile and outcome in a Greek PICU. METHODS: Prospective observational study. DATA COLLECTED: demographic profile; co morbidities; source and diagnosis at admission; Pediatric Risk of Mortality (PRISM III-24); Glasgow Coma Scale (GCS, pediatric); Injury Severity Score (ISS); procedures; treatment; mechanical ventilation (MV); MV days; length of stay (LOS) and the outcome at PICU discharge. STATISTICAL ANALYSIS: Student's t-test; Mann-Whitney U test; Kruskall-Wallis test; χ(2) criterion with relative risk (RR) estimation; Cox regression analysis; as appropriate. Values are mean ± SD, p < 0.05. RESULTS: 300 patients (196 boys/104 girls), aged 54.26 ± 49.93 months, were admitted due to respiratory failure (22.3%), head trauma (15.3%), seizures (13.7%), coma (9.7%), postoperative care (7.7%), polytrauma (7%), accidents (5.3%), sepsis-septic shock (5.3%), cardiovascular diseases (4.7%), metabolic diseases (3.3%), multiple organ failure syndrome (3%) and miscellaneous diseases (2.7%). PRISM III-24 score was 8.97 ± 7.79 and predicted mortality rate was 11.16% ± 18.65. MV rate was 67.3% (58.3% at admission) for 6.54 ± 14.45 days, LOS 8.85 ± 23.28 days and actual PICU mortality rate 9.7%. Patients who died had statistically worse severity scores. Significant mortality risk factors were inotropic use, PRISM III-24 > 8, MV, arterial and central venous catheterization, nosocomial infections, complications, and cancer. COX regression analysis showed that PRISM III-24 score and inotropic use were independent predictors of mortality. CONCLUSIONS: Demographic profile followed similar patterns to relevant studies while there were major differences in case mix and the severity of the disease. Mortality rate (9.7%) was relatively high but better than predicted and in accordance with the characteristics of our population.

Accidental puncture of the right lymphatic duct during pulmonary artery catheterization. A case report.

A case of an accidental placement of the introducer sheath of a Swan Ganz catheter into the right lymphatic duct during right internal jugular vein catheterization is presented. This rare complication has to be reported, because the choice of the right internal jugular vein for central venous catheterization has been strongly recommended, with special concern being paid to the avoidance of any thoracic duct injury. No deleterious complications were observed either in the immediate or in the later postanaesthetic period.

Migraine of gastrointestinal origin.

UNLABELLED: A consecutive series of 31 children (median age 12 years) suffering from migraine with (n = 21) or without (n = 10) aura underwent endoscopic oesophageal, gastric and duodenal biopsy in order to determine whether the complaints were of gastro-intestinal origin. Of these 31 children, 13 (41.9%) showed oesophagitis, 16 (51.6%) gastritis of corpus, 12 (38.7%) antral gastritis and 27 (87.1%) duodenitis. Thus, 29 of the 31 children studied had an underlying inflammatory lesion explaining their complaints. Helicobacter pylori colonization was found in 7 of the children: one had H. pylori associated antral and corporal gastritis and 6 H. pylori associated antral gastritis only. Gastritis of corpus without H. pylori was present in all these 6 children. Our data do not support that H. pylori is a primary pathogen of inflammatory changes seen in children studied, neither do they establish an association between H. pylori, antral gastritis and migraine. However, our data strongly suggest that there is a gastro-intestinal origin of these patients' complaints. CONCLUSION: Our findings provide further evidence that recurrent abdominal pain is an early expression of migraine and strongly support a causal link between recurrent abdominal pain and migraine.

Reliability of continuous jugular venous bulb hemoglobin oxygen saturation during cardiac surgery.

OBJECTIVE: To evaluate the accuracy and reliability of continuous measurement of jugular venous bulb hemoglobin oxygen saturation (SjvO2) with a fiberoptic catheter (SjvO(2OX)) during cardiac surgery versus simultaneous paired measurements of hemoglobin oxygen saturation by the Hemoximeter (SjVO(2HEM); Radiometer, Copenhagen, Denmark) and indirect estimations of hemoglobin oxygen saturation from measurements of partial pressure of oxygen in blood gases (SjVO(2BG)). DESIGN: A prospective study. SETTING: American Hellenic Educational Progressive Association General Hospital, University Hospital of Thessaloniki, Greece. PATIENTS: Thirty patients undergoing elective aortocoronary artery bypass surgery. INTERVENTIONS: In addition to routine pressure monitoring, a 4F fiberoptic catheter was placed in the left jugular bulb by a retrograde internal jugular vein approach and SIvO(2OX) was continuously measured. Before insertion, each catheter was calibrated in vitro. MEASUREMENTS AND MAIN RESULTS: One hundred twelve simultaneous paired recordings between SjvO(2OX) and SjVO2BG were performed to define the accuracy of SjVO(2OX) to SjVO(2BG). Sixty-one of 112 simultaneous paired recordings between SjvO(2OX) and SjVO(2HEM) and SjVO(2HEM) and SjVO(2BG) were performed to define the accuracy of SjvO(2OX) to the reference SjVO(2HEM) and the reliability of the SjVO(2BG) measurement to SjVO(2HEM). The fiberoptic catheter readings varied from underestimating to overestimating hemoglobin saturation by a mean of -5.35% to +9.67% and of -3.22% to +7.81% versus Blood Gas Analyzer (Ciba-Corning) and Co-Oximeter (OSM 2b Hemoximeter, Radiometer) values, respectively. The mean underestimation and overestimation of Co-Oximeter versus Blood Gas Analyzer values were -3.18% and +4.17%, respectively. CONCLUSION: SjvO2 values obtained continuously from a jugular venous bulb fiberoptic catheter may give relatively accurate readings provided they are duly interpreted and errors caused by wall artifact or blood sampling are avoided.

Controlled hypotension during anesthesia for otologic operations. An ultrastructural study of the brain in an experimental animal model.

We have studied the fine structure of the cerebral cortex, the cerebellar cortex, the thalamus, the caudate nucleus, the amygdala, the putamen, the vestibular nuclei, the substantia nigra, the hippocampus and the centrum semiovale in a canine model following 20 min controlled hypotension by the administration of sodium nitroprusside. The neurons and the astrocytes of all structures were intact morphologically. The synapses in the cerebral and cerebellar cortex were all unremarkable. Sensitive areas such as the molecular layer of the cerebellum did not demonstrate any ultrastructural alterations. We believe that carefully controlled sodium-nitroprusside-induced hypotension might be applied in middle ear microsurgery in otherwise healthy patients as an effective and innocuous method without causing any anoxic insult to sensitive areas of the central nervous system.

Intercostal nerve blockade with a mixture of bupivacaine and phenol enhance the efficacy of intravenous patient-controlled analgesia in the control of post-cholecystectomy pain.

Prolonged nerve conduction blockade has been proposed to result from the summed effects of charged and neutral local anaesthetics. Thirty-seven patients were randomly allocated to receive intravenous patient-controlled analgesia alone or combined with intercostal blockade (T7-T11) with a mixture of 0.45% bupivacaine and 0.6% phenol for post-cholecystectomy analgesia. Adequacy of pain relief was measured by patient scores on a 10-cm visual analogue scale and by dose-demand ratio, amounts of loading dose and total consumption of morphine and also the duration of patient-controlled analgesia in each group. No differences were found between groups in post-operative scores, dose-demand ratios and loading doses of morphine. However, in the combined treatment group, a significantly lower total consumption of morphine (P < 0.05), associated with a shorter duration of patient-controlled analgesia (P < 0.02) and a decreased mean number of unsuccessful demands (P < 0.001) were recorded. Intercostal blockade with bupivacaine-phenol supplements intravenous patient-controlled analgesia for post-cholecystectomy pain relief.