Monitoring of PETCO2 during High Frequency Jet Ventilation for Laryngomicrosurgery

In general, PETCO2 is well correlated with PaCO2 during spontaneous and conventional mechanical ventilation in normal lungs. However, it is known that during high frequency jet ventilation, PETCO2 may underestimate PaCO2 because of inadequate washout of the anatomical dead space by a small tidal volume and the relatively slow response time of infrared CO2 analyzers. The validity of PETCO2 as a reflection of PaCO2 was assessed during HFJV in 40 patients undergoing laryngeal microsurgery. HFJV was applied through an injector inserted into the trachea 6 cm below the vocal cord. PETCO2 was obtained from a sampling line placed 2 cm below the injector. Both PETCO2 and PaCO2 were measured simultaneously after decreasing the frequency from 100 beats per minute to 15 beats per minute 10 and 20 minutes after the commencement of HFJV. There was a strong correlation (r = 0.955, P < 0.001) and a good correspondence between the mean PETCO2 and PaCO2 values with an average difference of 1.93 +/- 1.21 mmHg and a limit of agreement from -0.49 to 4.35 mmHg. It is suggested that the PETCO2 obtained following a decrease in the jet frequency during HFJV could closely reflect PaCO2.

Analgesic Effects of Intraperitoneal Morphine, Nalbuphine, and Ketorolac on the Formalin Test in Rats / 대한마취과학회지

BACKGROUND: The antinociceptive effect and the potency of systemically administered morphine (micro-agonist), nalbuphine (agonist-antagonist), and ketorolac (cyclooxygenase inhibitor) was examined in rats using the formalin test. METHODS: Male Sprague-Dawley rats (250~300 g) received intraperitoneal injection of either saline or 3 doses of each test drug (0.3, 1.0, 3.0 mg/kg of morphine, 0.3, 1.0, 3.0 mg/kg of nalbuphine, and 10, 30, 100 mg/kg of ketorolac) 30 minutes prior to formalin injection. 50 microliter of 10% formalin was injected into the dorsal surface of the right hindpaw after 1 minute of 4% halothane induction. The construction of the dose-response curves and the determination of doses producing 50% maximum possible effect (ED50) were computed. RESULTS: Intraperitoneal injection of morphine, nalbuphine and ketorolac resulted in the significant, dose-dependent supression of both phases, but nalbuphine has a ceiling effect at high dose for analgesia at the phase I of the formalin test. The rank order of relative potency in rats to the formalin test was nalbuphine (1.16)>morphine (1)>>ketorolac (0.1) in phase I, morphine (1)>nalbuphine (0.61)>>ketorolac (0.02) in phase IIa, and morphine (1)>nalbuphine (0.57)>>ketorolac (0.03) in phase IIb. CONCLUSION: Comparing the systemic analgesic potency, nalbuphine and ketorolac will be needed in dosages 1.5 and 50 times that of morphine, respectively. These results suggest that ketorolac is not good enough as a single analgesic drug in preemptive analgesia for major surgery.