Anesthesia and analgesia
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Anesthesia and analgesia · Mar 1996
Comparative StudyOndansetron blocks nifedipine-induced analgesia in rats.
The serotonergic system is involved in pain transmission and the 5-hydroxytryptamine (5-HT3) receptor subtype mediates some of these effects at the spinal level. Therefore, we explored the effects of the serotonergic system on nifedipine-induced analgesia by using the 5-HT3 receptor antagonist ondansetron. Male Sprague-Dawley rats were pretreated with ondansetron (1 mg/ kg intraperitoneally) or normal saline. ⋯ Rats treated with nifedipine alone had an increase in tail-flick latency of 122%, as measured by the area under the curve, compared to rats treated with DMSO alone. Pretreatment with ondansetron, however completely blocked the analgesic effect of nifedipine, with tail-flick latency remaining at baseline throughout the measurement period. These results indicate that the 5-HT3 receptor plays an important role in the analgesic response to nifedipine and that medications that block this receptor may decrease the analgesic effectiveness of this type of therapy.
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Anesthesia and analgesia · Mar 1996
The effects of neuromuscular block on peak airway pressure and abdominal elastance during pneumoperitoneum.
Administration of muscle relaxants is considered as necessary to prevent high intraabdominal and peak inspiratory pressures induced by pneumoperitoneum during laparoscopy. In the present study, we hypothesized that neuromuscular block does not alter pulmonary or abdominal elastic properties in pigs receiving general anesthesia. To test this hypothesis, changes in peak airway pressure and abdominal elastance during intraabdominal CO(2), insufflation from 0 to 15 mm Hg were recorded in anesthetized pigs, with or without muscle relaxants. ⋯ Abdominal pressure/volume relationships were independent of muscle relaxant administration (calculated elastance was 3.98 +/- 1.56 mm Hg/L without muscle relaxant vs 3.86 +/- 1.37 mmHg/L in the atracurium group). We conclude that high peak inspiratory airway pressures and intraabdominal pressures during laparoscopy are not affected by neuromuscular block. These findings also question the necessity of muscle relaxants in clinical anesthetic practice during laparoscopic surgery.
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Anesthesia and analgesia · Mar 1996
Comparative StudyCerebral microregional oxygen balance during chronic versus acute hypertension in middle cerebral artery occluded rats.
This study was performed to compare microregional 0(2) supply and consumption balance in spontaneously hypertensive rats (SHR), normotensive Wistar Kyoto rats (WKY), and in phenylephrine-induced acutely hypertensive WKY (WKY + ph) rats. Under isoflurane anesthesia, a middle cerebral artery (MCA) of SHR (n = 7) and WKY (n = 14) rats was occluded. Seven of the WKY rats were infused with phenylephrine (WKY + ph) to keep the mean arterial pressure (MAP) at the same level as that of the SHR. ⋯ The number of veins with low 02 saturation (SvO2 < 40%) in the ischemic cortex was significantly lower in the WKY + ph than in the SHR or in the WKY group. Our data suggest that in chronically hypertensive animals, cerebrovascular adaptations enable the microregional 02 balance in focal ischemia to be maintained at a level similar to that of normotensive animals. However, in normotensive animals with focal cerebral ischemia, an acute increase of MAP improves microregional O2 balance.
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Anesthesia and analgesia · Mar 1996
Spinal cord blood flow after intrathecal injection of ropivacaine: a screening for neurotoxic effects.
The study of spinal cord blood flow (SCBF) after spinal drug application is an important aspect of preclinical neurotoxicological screening. This investigation was designed to study how a new local anesthetic, ropivacaine, affects SCBF after intrathecal (IT) administration in the rat. SCBF was measured continuously in spontaneously breathing, enflurane/N2O-anesthetized rats, using the laser-Doppler flowmetry technique. ⋯ SCBF decreased significantly to approximately 45% of the predrug value after the high concentration of 20 mg/mL ropivacaine (200 micrograms given IT), and this reduction was reversible within a period of 20 - 40 min after the injection. Whereas a high concentration of ropivacaine caused a definite reduction in spinal cord blood flow when administered IT to anesthetized rats, clinically relevant concentrations induced only minor changes. These results suggest that ropivacaine may be used to induce spinal anesthesia without causing clinically relevant effects on SCBF.