HPLC-DAD determination of mepivacaine in cerebrospinal fluid from a fatal case.

A fatal case involving mepivacaine-induced epidural anesthesia is described. The pathological findings were typical of cardiac shock from ischemic origin. Cerebrospinal fluid (CSF) was obtained several hours after death and mepivacaine was identified by gas chromatography-mass spectrometry (GC-MS). Its concentration was determined by high performance liquid chromatography with diode array detection (HPLC-DAD). Extraction from CSF was performed by deproteinization with acetonitrile. The mepivacaine concentration in the sample was 264 microg/mL. Concentrations of mepivacaine in CSF following epidural anesthesia are not reported in literature to our knowledge. This is the first reported case of death in which the mepivacaine concentration in CSF has been determined.

Determination of local anaesthetics in body fluids by gas chromatography with surface ionization detection.

Ten local anaesthetics were tested for their detection by gas chromatography (GC)-surface ionization detection (SID). Lidocaine, mepivacaine and bupivacaine were detected with the highest sensitivity; their detection limit was 5-10 pg in an injected volume. The sensitivity of other drugs, such as procaine, dibucaine tetracaine and oxybuprocaine, was an order of magnitude lower than that of the above three local anaesthetics. A detailed procedure for isolation of local anaesthetics from human whole blood and cerebrospinal fluid (CSF) by the use of Sep-Pak C18 cartridges, before the GC-SID, is also presented. The recovery of lidocaine, mepivacaine and bupivacaine, which had been added to 1 ml of whole blood or CSF, was close to 100%.

Spinal fluid concentrations of mepivacaine in horses and procaine in cows after thoracolumbar subarachnoid analgesia.

The CSF concentrations of mepivacaine in 10 Standardbred horses and of procaine in 10 Holstein cows given the drugs by thoracolumbar subarachnoid injection were determined. Mepivacaine hydrochloride was injected into the horses (502 +/- 60.5 kg) at an average dosage of 30 mg (1.5 ml of 20 mg/ml solution). Analgesia was produced 7.5 +/- 4.3 minutes after injection, extended between spinal cord segments T13 and L3 on both sides of the spinal column, and lasted 47 +/- 18.7 minutes at the T18 dermatome. Procaine hydrochloride was injected into cows (614 +/- 51.5 kg) at a dosage ranging between 75 mg and 100 mg (1.5 ml and 2 ml of 50 mg/ml solution). Analgesia was produced 8.2 +/- 2.0 minutes after injection, extended between spinal cord segments T11 and L4 on both sides of the spinal column, and lasted 47 +/- 17.5 minutes at the T13 dermatome. The critical CSF concentrations of local anesthetics required to eliminate response to pinprick stimulation were 204.4 +/- 90.3 micrograms of mepivacaine/ml in horses and 197.0 +/- 86.1 micrograms of procaine/ml in cows. Average CSF concentrations at 120 minutes after injections were made were 16.8 +/- 15.5 micrograms of mepivacaine/ml and 30.6 +/- 17.1 micrograms of procaine/ml. In in vitro experiments to determine the rates of hydrolysis of mepivacaine and procaine in CSF, significant changes (P greater than 0.05) were not seen in the CSF concentrations of mepivacaine in horses and procaine in cattle after a 120-minute incubation (37 C). The analgesic threshold concentrations of mepivacaine in CSF of horses and procaine in CSF of cows were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

[The solutibility of local anaesthetics in cerebrospinal fluid and the dependency of the process on the hydrogene ion concentration (author's transl)]. / Löslichkeit von Lokalanaesthetika im Liquor cerebrospinalis und ihre Abhängigkeit von der Wasserstoffionenkonzentration.

Reports on in vitro precipitation of local anesthetics suggested the possibility of a damaging effect on nervous tissue with spinal anesthesia. The present assays showed that the solubility of local anesthetics in aqueous media decreases with rising pH-levels. The partial pressure of CO2 determines the pH-level of the cerebrospinal fluid, the level ranging at about 7.35 + 0.011 (95% range: 7.327-7.371). The solubilities calculated for a pH of 7.371 (at 37 degrees C) are as follows: Bupivacaine.HCl 0.83+/-0.10 mh/ml Carticaine.HCl 27 +/-2.8 mg/ml Lidocaine.HCl 24 +/-1.3 mg/ml Mepivacaine.HCl 14.8 +/- 0.2 mg/ml Tetracaine.HCl 1.4 +/- 0.12 mg/ml.

[Clinical and experimental contribution concerning the pathogenesis of acute life-threatening complications during neck anaesthesia]. / Klinischer und experimenteller Beitrag zur Pathogenese akuter lebensbedrohlicher Zwischenfälle bei Nackenanästhesien

Apart from the usual hazards of local anesthesia (toxic reaction due to overdose or intravasal administration, allergic reaction, reaction to the vasoconstrictor), a further risk which should be borne in mind in local anesthesia of the neck region is inadvertent epidural or intrathecal administration of the local anesthetic agent. Depression of respiration or total respiratory failure may occur due to blockade of the superficially located medullary chemoreceptors in the form of a high or total spinal block. The pathogenesis of these incidents is investigated. Respiratory failure is usually reversible and requires immediate and effective therapy (artificial respiration, oxygen administration). The indications for neck anesthesia and their relativity within the entire therapeutic program should be given careful consideration. If (radicular) pain occurs during the injection, or if cerebrospinal fluid is aspirated, the procedure should be interrupted immediately and some time allowed to elapse. In fatal cases the injection channel must be dissected layer-wise in local anemia down to the dural sac. The possible pathway of toxic administration (epidural, subdural, intravasal) must be demonstrated chemically.