The Mechanism of Action of Intrathecal Morphine in Neuropathic Pain Induced by Nerve Ligation: The Effect of Naloxone / 대한마취과학회지

BACKGROUND: Although the efficacy of morphine in the neuropathic pain state is somewhat controversial, spinally administered morphine reversed the tactile allodynia in our previous animal study. Using a von Frey filament test, we examined the mechanism of action of intrathecal morphine by administration of the opioid receptor antagonist naloxone in a rat model of neuropathic pain induced by nerve ligation injury. METHODS: Male Sprague Dawley rats were prepared with tight ligation of the left lumbar 5th and 6th spinal nerves and a chronic lumbar intrathecal catheter. Intrathecal doses (0.3 and 1 microgram) of morphine were administered to attenuate the allodynic state. Naloxone was administered intrathecally (10 microgram) or intraperitoneally (30 and 150 microgram) in order to investigate the reversal of the antiallodynic effect of morphine. Allodynic thresholds for left hindpaw withdrawal to the von Frey hairs test were assessed and converted to %MPE. RESULTS: A reduced effect of tactile allodynia by intrathecal morphine was produced. Naloxone 10 microgram (IT) and 150 microgram (IP), but not naloxone 30 microgram (IP), reversed the antiallodynic effect of intrathecal morphine (P < 0.05). CONCLUSIONS: The results suggest that the mechanism of tactile antiallodynia induced by intrathecal morphine may include the opioid receptor system at the spinal and supraspinal level in a rat model of nerve ligation injury.

The Accuracy of Pulse Oximeter in Predicting the Arterial Oxygen Saturation

We studied 21 neonates who required mechanical ventilation during study period in NICU OF Il Sin Christian Hospital with diagosis of prematurity, IRDS, pneumothorax and diaphragmatic hernia to evaluate the accuracy of pulse oximeter in predicting the arterial oxygen saturtion, hypoxia and hyperoxemia. We also studied whether the changes of birth weight, hematocrit, blood pressure and body temperature affect the accuracy of pulse oximeter. The results are 1) Linear regression analysis revealed a close correlation between in vivo pulse oximeter readings and in vitro SaO2 measurements in patients (Y=0.008X+12.34, r=0.946) 2) The changes of birth weight, hematocrit, blood pressure and body temperature did not affect the accuracy of pulse oximeter. 3) SpO2-PaO2 relationship was similar to the SsO2-PaO2 relationship. 4) When Nellcor N-100 pulse oximeter was setted at alarm limit 96% to avoid hyperoxemia, it identified 16 of 22 hyperoxemic instances (sensitivity 73%) and alarmed falsely in 48 of 92 nonhyperoxemic instances (specificity 59%).