Anesthesiology
-
Chiral local anesthetics, such as ropivacaine and levobupivacaine, have the potential advantage over racemic mixtures in showing reduced toxic side effects. However, these S-(levo, or "-")isomers also have reportedly lower potency than their optical antipode, possibly resulting in no advantage in therapeutic index. Potency for local anesthetics inhibiting Na+ channels or action potentials depends on the pattern of membrane potential and so also does the stereopotency ratio. Here the authors have quantitated the stereopotencies of R-, S-, and racemic bupivacaine, comparing several in vitro assays of neuronal Na+ channels with those from in vivo functional nerve block, to establish relative potencies and to understand better the role of different modes of channel inhibition in overall functional anesthesia. ⋯ Although the in vitro actions of bupivacaine showed stereoselectivity ratios of 1.3-3:1 (R:S), in vivo nerve block at clinically used concentrations showed much smaller ratios for peak effect and no significant enantioselectivity for duration. A primary role for the blockade of resting rather than open or inactivated Na+ channels may explain the modest stereoselectivity in vivo, although stereoselective factors controlling local disposition cannot be ruled out. Levo-(S-)bupivacaine is effectively equipotent to R- or racemic bupivacaine in vivo for rat sciatic nerve block.
-
Comparative Study
Pharmacokinetics and pharmacodynamics of inhaled versus intravenous morphine in healthy volunteers.
A new pulmonary drug delivery system produces aerosols from disposable packets of medication. This study compared the pharmacokinetics and pharmacodynamics of morphine delivered by an AERx prototype with intravenous morphine. ⋯ The onset and duration of the effects of morphine are similar after intravenous administration or inhalation via this new pulmonary drug delivery system. Morphine bioavailability after such administration is 59% of the dose loaded into the dosage form.
-
Gender-related differences in pain have been clearly shown in experimental settings. Clinical studies of such differences have produced conflicting findings. No studies have shown a significant difference in pain experience associated with differences in functional outcomes. Arthroscopic anterior cruciate ligament reconstruction (AACLR) produces pain of moderate intensity and provides a useful setting for examining gender-related differences in pain and function. ⋯ Women seem to experience greater intensity of pain after AACLR that is associated with a decrease in an intermediate measure of functional outcome. These differences may result from differences in either response to analgesics or neuroprocessing.
-
Cerebral hyperthermia after hypothermic cardiopulmonary bypass has been poorly documented for adults and never in children. This study was designed to monitor brain temperature during and up to 6 h after cardiopulmonary bypass in infants and children. ⋯ Mean JVBT was significantly increased over the mean core temperature at all times from rewarming by cardiopulmonary bypass onward. Although the lower esophageal, rectal, and tympanic temperatures correlated well with JVBT, all three failed to reflect JVBT during recovery. This observation might help to elucidate factors involved in the functional and structural neurologic injury known to occur in pediatric patients.