Regional anesthesia
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Regional anesthesia · May 1989
Comparative StudyAntinociceptive effects of localized administration of opioids compared with lidocaine.
To study possible antinociceptive effects of perineurally administered opioids, the rat infraorbital nerve block (IONB) model was employed for investigations of opioids (morphine, meperidine, buprenorphine, ethylketocyclazocine, and fentanyl) of differing receptor selectivity and physicochemical properties such as lipid solubility. Only meperidine in doses greater than 1 mg/kg produced localized analgesia, the duration of which increased dose-dependently. Naloxone failed to counteract the analgesic effects of meperidine. ⋯ The two agents caused a similar duration of sensory block in infiltration anesthesia. Meperidine was shorter than lidocaine in epidural anesthesia. The characteristics of blocks induced by the two agents may be explained by structural differences and associated differences in physicochemical properties such as lipid solubility and pKa.
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Regional anesthesia · Mar 1989
Comparative StudyA comparison of cardiovascular responses of normotensive and hypertensive elderly patients following bupivacaine spinal anesthesia.
The hypotensive effects of spinal anesthesia were investigated in 60 patients aged 75 years or older and divided into two groups: 30 normotensive patients (group 1) and 30 treated hypertensive patients (group 2). In both groups, spinal anesthesia was performed in lateral decubitus position with 3 ml 0.5% isobaric bupivacaine. Hemodynamic measurements were performed before the establishment of spinal blockade and repeated during the 60 minutes following intrathecal injection. ⋯ Five patients in group 2 (but none in group 1) had a SBP decrease of 40% from baseline or more. The decreases in MBP and DBP were persistent after 60 minutes. These results suggest that pre-existing hypertension can be recognized as an important factor to explain blood pressures changes during isobaric bupivacaine spinal anesthesia in elderly patients.
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Regional anesthesia · Mar 1989
Contractility effects of local anesthetics in the presence of sodium channel blockade.
The effects of lidocaine (25, 50 and 100 micrograms/ml) and bupivacaine (5, 10, and 20 micrograms/ml) on amplitude, velocity, and contraction frequency were studied in monolayer cultures of spontaneously beating chick embryo ventricular cells. The physiologic parameters of contraction frequency, amplitude, and velocity of shortening were measured with an optical-video system. Studies were also carried out in the presence of 1 microM tetrodotoxin (TTX) to isolate effects caused by TTX-sensitive ion channel blockade from other possible mechanisms of action of local anesthetics. ⋯ In the presence of TTX, lidocaine (50 micrograms/ml) produced a further decrease in amplitude of contraction, but no significant change in contraction frequency or velocity of contraction. It is well known that local anesthetics block Na+ channels of excitable membranes. The authors observations suggest that both lidocaine and bupivacaine have at least one locus of action at a site other than a TTX blockade site.