Ictal vomiting in partial seizures of temporal lobe origin

We report 3 cases presenting ictal vomiting during partial seizures of temporal lobe origin. Two patients had complex partial seizures accompanying vomiting characteristics. Ictal vomiting occurred early in the course of the seizure when rhythmic discharges involved predominantly the left hemisphere, the language dominance hemisphere. The other patient had ictal vomiting in simple partial seizures which originated from the right temporal lobe or the language nondominant side. All 3 patients underwent anterior temporal lobectomy with promising outcomes. Pathologic diagnosis included hippocampal sclerosis in 2 patients and astrocytoma in 1 patient. In our patients, ictal vomiting does not lateralize temporal lobe epilepsy and is not specific to pathology.

[Shear bond test of HF acid etching porcelain bonded to enamel with different concentration and disposing time]

OBJECTIVE:Understand the effect of shear bond test of HF acid etching porcelain bonded to enamel with different concentration and disposing time. METHODS:After HF acid etching under 30 groups composed of 5 different HF concentrations and 6 exposing times,shear bonding strength of porcelain to enamel was tested under imitating occlusion and debonding types of the composite were examined by microscope.RESULTS:The favorable concentration-time groups for clinics were 2.5%-5min;5.0%-2.5min;10%-30s;7.5%,15%-5min.The debonding type of porcelain resin enamel composite body was mixed one.CONCLUSION:The results showed HF acid etching technique had a positive influence on the bonding strength of porcelain to enamel.

Unpreconditioned free revascularized dynamic cardiomyoplasty. Is it feasible?

BACKGROUND

Cardiomyoplasty is a new ventricular bioassist device for myocardial failure. But there are some limitations in standard cardiomyoplasty, such as the orientation of the muscle and fiber and the efficiency of the contractile segment of the flap. Free revascularized latissimus dorsi flap may be a good idea for solving these problems.

METHODS

We designed a canine free latissimus dorsi flap by revascularizing the flap with the left internal thoracic vessels by micro-surgical technique. Group I (n = 3) as control was performed by standard cardiomyoplasty, and the Group II (n = 10) was performed by the revascularized method. The heart was then wrapped by the revacularized flap. Group II was divided into IIa (n = 6, no pre-treatment before revascularization) and IIb (n = 4, normal saline pre-treatment before revascularization) by the different preservation methods. Hemodynamic data were recorded.

RESULTS

Group I all survived the 8-week training period. But Group II, Group IIa and IIb, all died in 3 days, but survived more than 12 hours. The hemodynamic analysis in Group I did not show any significant change except left ventricular end diastolic pressure. It showed elevated left ventricular pressure when the cardiostimulator was ON.

CONCLUSIONS

According to the result of this experiment, it seemed impossible to get a satisfactory result of more than 3 days for free revascularized cardiomyoplasty at present. There were a lot of problems waiting to be solved, such as preservation method during ischemia, bulky mass of the flap, and the potential problem of neuromuscular atrophy.

Programmable high-bit-rate pattern generator with a segmented semiconductor optical amplifier

We have demonstrated that spatial gain modulation in a segmented semiconductor optical amplifier can be converted to a temporal signal. A four-segment amplifier was used to generate digital return-to-zero patterns at 40 Gbits/s , and this technique should be readily scalable to more than 100 Gbits/s .

Displacement effect of valproate on bilirubin-albumin binding in human plasma

Drugs that can displace bilirubin from plasma albumin binding may cause various late manifestations of brain damage if given to newborns with unconjugated hyperbilirubinemia. The purpose of this study was to examine the displacement effect of valproate (VPA) on bilirubin-albumin binding in human serum albumin (HSA) and human plasma. Bilirubin-HSA solution and bilirubin-plasma solution containing no or serial concentrations of VPA were prepared, and free bilirubin in these solutions was measured by the enzyme oxidation method. VPA displaced bilirubin from bound bilirubin-albumin. The binding constant (KD) of VPA to the high affinity bilirubin-binding site of HSA and plasma protein were 11.6 L/mmol and 9.0 L/mmol respectively. The displacement effect may occur at the clinical concentration range of VPA, with a maximal displacing factor of 1.5 to 4.7. These results suggest that the clinician should use VPA in jaundiced neonates with caution.

Evaluation of buffering capacity and acid neutralizing-pH time profile of antacids

The antacid properties of seven antacids listed in the hospital formulary of a medical center were evaluated with in vitro tests. These included not only the preliminary antacid test and acid-neutralizing capacity test as described in the United States Pharmacopeia (USP XXIII), but also a buffering pH profile test. The preliminary antacid test measured the final pH of a 10-mL solution of 0.5 N HCl 10 minutes after addition of the minimum recommended dose of an antacid, while the neutralizing capacity test measured the amount (mEq) of HCl neutralized by the minimum recommended dose in 15 minutes. The buffering pH profile recorded the pH time course of dynamic simulated gastric fluid neutralization by a dose of an antacid. In the preliminary antacid test, magnesium oxide showed the highest pH (9.52 +/- 0.14, mean +/- standard deviation, n = 3); aluminum phosphate gel yielded a final pH of 2.51 +/- 0.01, thus failing to meet the criteria of an antacid (pH > 3.5). In the acid-neutralizing capacity test, hydrotalcite had the highest neutralizing capacity (28.26 +/- 0.3 mEq), while sodium bicarbonate had the lowest (7.40 +/- 0.12 mEq). In the buffering pH profile test, aluminum-magnesium hydroxide suspensions and hydrotalcite tablets maintained a steady optimum pH (3-5) for around 1.5 hours. One tablet of calcium carbonate, sodium bicarbonate or magnesium oxide could not raise the gastric pH to above 3, but two tablets increased the pH excessively (5.3 to 8.6). The higher dose (two tablets) of aluminum hydroxide hexitol complex could not raise the pH to the optimal level. These findings demonstrate that there is disparity in the antacid effectiveness estimated by the neutralizing capacity test and the buffering pH profile test and suggest that the efficacy of an antacid cannot be accurately predicted from its acid-neutralizing capacity. The dose of antacids greatly influences the neutralizing pH profiles. Aluminum-magnesium compounds appear to provide steadier buffering than carbonate compounds or magnesium oxide.

Effect of valproate on the pharmacokinetics of free and total plasma bilirubin in experimental hyperbilirubinemia in guinea pigs

The effects of valproate (VPA) on free and total bilirubin concentrations in plasma were studied in guinea pigs. Steady-state hyperbilirubinemia (around 2.5-3.0 mg/100 mL) was induced by constant intravenous (i.v.) infusion of bilirubin followed by an i.v. bolus dose of sodium valproate (VPA-Na) of 50 (n = 4) or 200 (n = 5) mg/kg. Steady-state plasma total bilirubin concentration was lowered by 40% and 55% and the unbound fraction (fu) increased by 1.9- and 4.9-fold at the respective doses of 50 mg/kg and 200 mg/kg VPA-Na. Free bilirubin was not significantly changed by 50 mg/kg VPA-Na, but did show a significant transient elevation with the 200 mg/kg dose. In another experiment, guinea pigs (n = 3) were given a constant i.v. infusion of VPA-Na to maintain a steady-state plasma concentration (58 micrograms/mL), followed by an i.v. bolus dose of bilirubin (2 mg/kg). A control study (n = 3) was performed simultaneously using normal saline instead of VPA. Free bilirubin was detectable only following induction of hyperbilirubinemia in either group. A higher volume of distribution and lower elimination rate constant of bilirubin were observed in the VPA-treated than in the control animals. The displacement effect of VPA on bilirubin-plasma binding in vitro was studied by adding serial concentrations of VPA-Na to bilirubin-plasma solution. VPA displaced bilirubin from the high-affinity plasma protein binding site, with a binding constant (KD) of 5.7 x 10(-2)/microM. Similar displacement of bilirubin plasma protein binding was observed in vivo. These results suggest that VPA reduces plasma protein binding and slows the elimination rate of bilirubin. The principal mechanism for decreased plasma concentrations of total bilirubin by administration of VPA is caused by decreased plasma binding, as opposed to metabolic induction.

Uptake of charged liposomes by the rat liver

The influences of liposomal surface charge on hepatic uptake of liposomes in vivo and in vitro were studied in rats. 3H-inulin was entrapped in positively charged, negatively charged or neutral liposomes composed of phosphatidylcholine, cholesterol, and a charge lipid at a molar ratio of 4:4:1, or without a charge lipid. Plasma and liver concentrations of inulin were measured 5, 15, 30, and 60 minutes after an intravenous bolus dose of liposome. The in vitro study comprised incubation of liposomes with primary culture of isolated rat hepatocytes. The incubation was terminated at 30, 60, 90, 120, and 180 minutes, and cellular uptake of inulin was determined. The results showed that the positively charged liposomes resulted in the highest plasma liposome concentration. The negatively charged liposomes gave the highest liver liposome concentration, among the three liposomes. In vitro study also demonstrated that cellular uptake of a negatively charged liposome was higher than positively charged or neutral liposomes. These results suggest that positively charged liposomes might be preferable for maintaining higher plasma concentrations, while negatively charged liposomes might be more efficient for drug delivery to the liver.

Comparison of systemic absorption of aqueous and liposomal lidocaine following intra-articular injection in rabbits

Aqueous lidocaine is a local anesthetic that is frequently used in intra-articular injection. However, aqueous lidocaine may be less than ideal because of its rapid absorption. Liposomes can serve as drug carriers for encapsulating lidocaine. Both aqueous lidocaine and liposomal lidocaine were injected into knee joints of adult rabbits and the pharmacokinetic changes were studied. The peak serum level of lidocaine from the liposomal preparation was significantly lower than that from the aqueous preparation. The amount of lidocaine absorbed in 4 hours was also significantly lower in the liposomal group. This phenomenon may have been due to local accumulation of liposomal lidocaine and the slow release of lidocaine from liposomes. Intra-articular use of liposomal lidocaine may have advantages over the aqueous form because of its lower systemic serum concentration.

Negative transcriptional regulation of the chicken Na+/K(+)-ATPase alpha 1-subunit gene

Although the Na+/K(+)-ATPase alpha 1-subunit gene is ubiquitously expressed in vertebrates, its level of expression varies among tissue and cell types. In spite of similar mRNA distribution in tissues of mammals and birds, the 5'-flanking regions of alpha 1-subunit genes exhibit remarkable diversity; i.e., the core promoter activity of the TATA-less chicken alpha 1 gene strongly depends upon multiple Sp1-based regulation (six Sp1 sites), whereas the promoter activity of the TATA-like rat alpha 1-subunit gene relies on the two Sp1 and additional positive regulatory factors. Further analysis of the regulatory regions of the Na+/K(+)-ATPase alpha 1-subunit genes revealed that the vertebrate alpha 1-subunit genes may share common inhibitory mechanisms for subtle transcriptional regulation; the core promoter activities can be either enhanced or repressed depending on the availability of inhibitory factors. Two potential candidates for such inhibitory elements in both avian and mammalian Na+/K(+)-ATPase alpha 1-subunit genes are (1) a newly identified element, GCCCTC, and (2) a GCF-binding sequence, NN[G/c]CG[G/c][G/c][G/c]CN, or its reverse complement. Gel retardation assays using the inhibitory region of the chicken gene and crude nuclear extracts from tissue-cultured chicken and mouse cells showed the existence of a set of proteins that bind to this region. The amounts of individual regulatory proteins in different cell types seem to vary, resulting in differential formation of DNA/protein complexes in different cell types. Thus, the regulation of Na+/K(+)-ATPase alpha 1-subunit gene expression under different cellular environment as well as in different cell types can be achieved by a shared mechanism; modulation of the ratio of the abundance of individual inhibitory factors.

Glucuronidation metabolic kinetics of valproate in guinea pigs: nonlinear at clinical concentration levels

PURPOSE

Nonlinear conjugation metabolic rate of valproic acid (VPA) has been speculated previously from plasma elimination and liver concentration of VPA in guinea pigs. The purposes of the present study were to assess our speculation by direct measurement of VPA glucuronidation rate in vitro.

METHODS

VPA at various concentrations (10-200 micrograms/ml) was incubated with guinea-pig liver-homogenate, mitochondria or microsome in the presence of cofactor, uridine 5'-diphosphoglucuronic acid (UDPGA). The maximum glucuronidation rate (Vmax) and Michaelis-Menten constant (Km) of VPA were determined.

RESULTS

On a body weight basis, the Vmax and the Km values of VPA glucuronidation estimated from liver homogenate were 1.8 mumol/min/kg and 0.3 mumol/ml, respectively; and that from microsome suspension were 1.2 mumol/min/kg and 0.16 mumol/ml, respectively. These data are comparable with the primary metabolic parameters observed from previous in vivo study. The glucuronidation clearance calculated from these parameters was 0.10-0.48 fraction of total clearance, which was in agreement with the reported data observed from clinical and animal urinary recoveries of VPA-G. The glucuronidation reaction was not detectable in mitochondria suspension.

CONCLUSIONS

The glucuronidation kinetics of VPA is nonlinear and saturable within clinical concentration range. Estimation of in vivo VPA glucuronidation kinetics from in vitro kinetic parameters is feasible.

Dose-dependent distribution volumes of total and unbound valproate in guinea-pigs: consequence of non-linear plasma protein binding

The response of steady-state distribution volume (Vdss for total and Vdssu for unbound drug) of valproate (VPA) to dose-dependent plasma protein binding was studied in guinea-pigs. Various steady-state plasma concentrations of VPA were achieved by intravenous constant infusion. The concentrations of VPA in plasma (Css for total and C(uss) for unbound drug) and various tissues (CT) were determined. The Vdss and the Vdssu were estimated based upon the apparent tissue-to-plasma concentration ratio of VPA. The results showed that the plasma unbound fraction (fu) of VPA increased significantly with dose. The Vdss was significantly increased with, while the Vdssu was significantly decreased against the increasing dose. The increase in Vdss with dose indicated an increase in tissue-to-plasma concentration ratio, which may be attributed to the increase in distribution of unbound drug from plasma to tissues subsequent to non-linear plasma protein binding. The decrease in Vdssu against the increasing dose indicated a decrease in tissue-to-unbound plasma concentration ratio, which suggests that the extravascular distribution of unbound VPA might be capacity limited and the tissue binding of VPA negligible.

Propofol concentration monitoring in plasma or whole blood by gas chromatography and high-performance liquid chromatography

We compared the measurement of propofol concentrations in plasma or whole blood by high-performance liquid chromatography (HPLC) to that of gas chromatography (GC). Blood samples were collected from patients who had received bolus injection or continuous infusion of propofol. The results showed that the two methods correlated well both in plasma and whole blood samples. However, significant biphasic differences of propofol concentrations between plasma and whole blood specimens were observed in the bolus injection group. Differences were larger in the infusion group. This discrepancy in concentrations resulted from the infusion or clearance of propofol, and the lag of redistribution across blood cell membranes. In conclusion, monitoring of propofol concentrations by the methods of GC and HPLC gives equivalent results. For propofol concentration monitoring, plasma samples are preferred, but immediate centrifugation is needed.

Lack of effect of flumazenil on the reversal of propofol anaesthesia

Propofol, like the benzodiazepines, activates the GABAA receptor-chloride ionophore complex; they potentiate one another. Since neither pharmacodynamic nor pharmacokinetic data concerning drug interaction between flumazenil and propofol is available, and especially considering the relationship of binding sites, flumazenil, the antagonist of benzodiazepines, was investigated to determine its effect upon recovery from propofol anaesthesia. Forty women receiving dilatation and curettage procedures were included in this double-blind test. After 50 micrograms fentanyl, propofol 2 mg.kg-1 was injected for induction and followed by infusion at the rate of 15 mg.kg-1.hr-1. After the operation, patients were given normal saline (Group A) or flumazenil 10 micrograms.kg-1 (Group B) randomly. Recovery time in Group A was 15.2 +/- 5.1 min and Group B 15.8 +/- 4.8 min. Propofol concentrations at the end of infusion were 4.17 +/- 1.33 micrograms.ml-1 (Group A) and 4.03 +/- 1.45 micrograms.ml-1 (Group B); these then declined to 1.22 +/- 0.17 micrograms.ml-1 (Group A) and 1.18 +/- 0.15 micrograms.ml-1 (Group B) when patients were able to open their eyes on command. No significant differences were found between the groups based on propofol concentrations and recovery time, nor did haemodynamic changes differ between them after administration of reversal agents. It was concluded that flumazenil 10 micrograms.kg-1 does not influence recovery from propofol anaesthesia.

Analysis of tissue distribution of valproate in guinea-pigs: evidence for its capacity-limited tissue distribution

The tissue distribution of valproic acid (VPA) was investigated over a wide range of steady-state plasma levels (Css) in guinea-pigs. The VPA concentrations in various tissues, except the kidney, were all lower than in plasma. Tissue-to-unbound plasma concentration ratios (Kpu) of VPA for adipose, heart, kidney, liver, lung, muscle, pancreas and skin all decreased significantly with increasing unbound plasma concentration (Cuss). The Kpu for brain (0.5-0.9), intestine, spleen and stomach failed to show significant change with Cuss. The disposition of VPA in tissues is adequately described by a model in which VPA was distributed in interstitial and intracellular fluid and bound to interstitial albumin, with limited tissue binding. Tissue binding was extensive only in the kidney. Most of the measured apparent Kpu values agreed well with simulated Kpu values. Steady-state tissue concentration of VPA can be predicted from Css and Cuss when reference data for interstitial albumin and tissue total water are available.

Assembly of Na,K-ATPase alpha-subunit isoforms with Na,K-ATPase beta-subunit isoforms and H,K-ATPase beta-subunit

cDNA encoding an epitope tag was joined to cDNAs encoding the chicken Na,K-ATPase beta 1 and beta 2 and H,K-ATPase beta-subunits to allow recognition of these beta-subunits with the same monoclonal antibody during assembly assays. cDNAs encoding chicken Na,K-ATPase alpha 1, alpha 2, or alpha 3 and Na,K-ATPase beta 1 or beta 2 or H,K-ATPase beta-subunits were transiently coexpressed in mammalian cells. Subunit assembly was assayed by immune precipitation of alpha-isoforms with a monoclonal antibody to the epitope-tagged beta-subunits. Each of the chicken alpha-isoforms assembled with each of the Na,K-ATPase beta-subunits and the H,K-ATPase beta-subunit. Each of the epitope-tagged beta-subunits also assembled with a Na,K-ATPase/Ca-ATPase chimera that retained only 26 amino acids of the Na,K-ATPase alpha-subunit, demonstrating that all three beta-subunits recognize this same alpha-subunit assembly site.

Effects of ethanol on pharmacokinetics and intestinal absorption of paraquat in animals

The effect of ethanol on pharmacokinetics of paraquat was studied in rabbits by intravenous (i.v.) bolus injection of ethanol 0.5 g/kg (or normal saline, in the control group) followed by an i.v. dose of paraquat 20 mg/kg. A greater apparent volume of distribution (Vd), faster distribution rate constants and lower peak plasma concentration (P < 0.01) of paraquat were observed in the ethanol-treated than that in the control rabbits. The total clearance of paraquat was not significantly different between the two groups. The effect of ethanol on the intestinal absorption of paraquat was estimated by in situ intestinal perfusion technique in rats. The perfusate contained paraquat 50 micrograms/ml alone or with 1% or 2% ethanol. Inulin 320 micrograms/ml was added to the perfusate for the measurement of water net flux. The absorption clearance of paraquat as well as the absorption of water increased (P < 0.01) about two-fold in the presence of ethanol. The results of this study suggest that ethanol may potentiate paraquat toxicity by increasing intestinal absorption and tissue distribution. The critical lethal plasma concentration of paraquat is supposed to be lower in the presence of ethanol owing to increased volume of distribution.

Comparison of absorption of aqueous lidocaine and liposome lidocaine following topical application on rabbit vessels

Liposomes are small particles that encapsulate lidocaine to form topical drug carriers. Forty rabbits were used to compare the absorption of aqueous lidocaine with that of liposome lidocaine after application of each on femoral and iliac vessels. Both agents entered the circulation rapidly. The serum levels of lidocaine were significantly lower and the peaks in concentration appeared later after the use of liposome lidocaine than after the use of aqueous lidocaine. This phenomenon was due to local accumulation of liposome lidocaine and slow release of lidocaine from the liposome. As a topical spasmolytic agent, liposome lidocaine may be superior to the aqueous form due to a lower serum concentration and less total absorption.

Quantitation of propofol in plasma by capillary gas chromatography

A rapid, accurate and sensitive gas chromatographic method is described for measuring plasma concentrations of propofol. The technique required only 200 microliters of plasma and a single extraction process, using chloroform containing pentadecane (500 ng/ml) as an internal standard. Quantitation was achieved on an SGE BP-1 fused-silica capillary column (25 m x 0.33 mm I.D., 0.5 micron film thickness) with flame ionization detector. The peak response was linear over a wide concentration range (10-10,000 ng/ml) and the limit of quantitation was 10 ng/ml. The absolute recoveries were over 96% (n = 3). The method is applicable for both research and routine plasma level monitoring.

Nonlinear elimination and hepatic concentration of conjugation-metabolite of valproate in guinea-pigs

The plasma clearance and metabolic rate characteristics of valproic acid (VPA) were studied using guinea-pigs placed on various (0.08-9 mumol ml-1 = 11-1303 micrograms ml-1) steady-state plasma concentrations (Css) by constant intravenous (i.v.) infusion. The total clearance (CL) was significantly decreased at plasma concentration of 0.61 mumol ml-1 (88 micrograms ml-1). The metabolic clearance of VPA was apparently biphasic. The maximum metabolic rate (Vmax) and the Michaelis-Menten constant (Km) for the primary (Vmax1, Km1) and the secondary (Vmax2, Km2) pathways were Vmax1 = 1.52 mumol min-1 kg-1, Km1 = 0.15 mumol ml-1, Vmax2 = 24.98 mumol min-1 kg-1 and Km2 = 11.70 mumol ml-1, respectively. The Km1 value was within clinical therapeutic concentration range. The formation of conjugated VPA (cjVPA) metabolite in liver was shown to be saturable. Plasma protein binding of VPA was also nonlinear. The dose-dependent decrease in metabolic clearance was counterbalanced by the increased unbound fraction (fu), resulting in a relatively constant apparent clearance of VPA over a wide concentration range. The hepatic concentration of VPA was not significantly different from the plasma unbound concentration, again over a wide concentration range. The biliary and hepatic concentrations of VPA were not significantly different; but the concentration ratio of cjVPA in bile compared with that of VPA in liver decreased against hepatic concentration of VPA, which suggests a saturable conjugation rate. The Km value estimated from hepatic cjVPA production as a function of plasma VPA concentration was comparable with the Km1 value.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose-dependent inhibition in plasma protein binding of valproic acid during continued treatment in guinea-pigs

Plasma protein binding of valproic acid over a wide range of steady-state plasma concentration (11.3 +/- 2.6-1303.0 +/- 122.9 micrograms mL-1: s.e.m., n = 5) in guinea-pigs has been studied. Valproic acid was given by intravenous constant infusion. At steady-state the plasma protein binding of valproic acid was analysed. Nonlinear binding was observed. Unbound fraction (fu) of valproic acid increased from 25 to 95% with the increase of steady-state plasma concentration (Css). The plasma protein-bound drug concentration (Cb) of valproic acid increased initially with Css but decreased after the Css exceeded 345.0 micrograms mL-1, where the Cb was 152.5 +/- 26.8 micrograms mL-1. At a Css of 1303.3 +/- 122.9 micrograms mL-1 the Cb was significantly (P less than 0.05) decreased to 72.8 +/- 20.2 micrograms mL-1. Binding characteristics of valproic acid in-vitro were studied using drug-free guinea-pig plasma with added valproic acid (10-1000 micrograms mL-1). The binding behaviour was also nonlinear in-vitro. The fu increased from 14 to 79% with the increase of valproate concentrations. No decrease in Cb was observed throughout the range. The study demonstrated that binding characteristics of valproic acid in-vivo and in-vitro are not parallel. The results suggest that valproic acid may produce or induce plasma protein binding competitors; metabolites of valproic acid may be implicated.

Effect of ethanol on the disposition of paraquat

Rabbits that received paraquat (200 mg/kg) and ethanol (1.0-3.8 g/kg) by gavage resulted in shorter median survival times and higher mortality rates than those dosed with paraquat alone. Plasma paraquat levels in rabbits dosed with ethanol before, after and concurrently with ingestion of paraquat were significantly higher when compared with animals without ethanol intake. Furthermore, substantial differences in paraquat kinetics, higher AUC, lower total clearance (CL/F) and volume of distribution (V/F) were seen in the ethanol-paraquat group. The effect of ethanol on acute paraquat toxicity is, at least in part, associated with the increase in paraquat absorption and/or the decrease in paraquat excretion.

Absorption of lidocaine following topical application in microvascular procedures on rabbits

Fifty rabbits were used to investigate the absorption of lidocaine following its topical application to blood vessels. The lidocaine level in the blood was determined by gas chromatography and the enzyme immunoassay. Animals were divided into five groups according to anatomic site (femoral vs iliac) and according to whether vessels were intact or anastomosed. In the last group (E), a water-tight sleeve was placed on the anastomosed femoral artery so that the lidocaine contacted only a small segment of the artery. In each group, 0.4 and 1 ml of 10% lidocaine were used. Our results revealed that absorption of lidocaine from topical usage was rapid. The absorption peak occurred within 5-15 min. The serum concentration of lidocaine was significantly higher in groups with intact vessels than in those with anastomosed ones. The peak level of lidocaine in the serum occurred sooner in the iliac area than in the femoral area. Absorption in group E was very low due to only a small segment of the artery being immersed with lidocaine. The main absorption site of lidocaine was not through the vessel but through the perivascular area. Toxicity may develop clinically if a high concentration of lidocaine is applied on a vessel during microsurgery.