Does long-term continuous transcranial Doppler monitoring require a pause for safer use?

BACKGROUND: Transcranial Doppler sonography (TCD) has been used widely for long-term monitoring of cerebral blood flow without adverse reports. However, attention has not been adequately paid to the fact that an increase in the time period of TCD insonation causes brain temperature to rise due to ultrasound absorption by tissue and the skull. We measured the actual temperature rise in local brain tissue induced by TCD insonation over a long time period during in vivo animal experiments in order to verify whether or not a pause is required in long-term, continuous TCD monitoring. METHODS: We inserted thermocouples into the skull-brain interface (SBI) of 15 New Zealand White rabbits (10: TCD application group; 5: control group, TCD non-application group). The TCD probe was placed on the parietal bone, and changes in SBI temperature (SBIT) were measured for 90 min. TCD was set at maximum output level (0.2 W, 2 MHz). RESULTS: SBIT in the TCD group increased rapidly to 3.47 degrees C within 25 min and then reached a plateau. The maximum time for safe continuous TCD application is estimated to be 33 min. CONCLUSIONS: Even though there are large differences in factors, such as brain volume and environmental conditions, between rabbits and humans, there is less difference in their cerebral blood flow per brain weight, which is the parameter that is mainly associated with heat reduction. Accordingly, the findings of the present experiment suggest that long-term TCD monitoring in clinical use should include a pause after every 30 min of insonation to avoid thermal damage to the brain surface.

The efficacy of intratracheal administration of vecuronium in rats, compared with intravenous and intramuscular administration.

To investigate the suitability of the intratracheal (IT) route as an alternative route for the administration of vecuronium, we compared the pharmacodynamic parameters for neuromuscular block in three groups of rats given vecuronium via the IT, IM, and IV routes. We also examined the pharmacokinetics of vecuronium in the three groups. The doses for the IT, IV, and IM groups were set at 1.50, 0.300, and 2.25 mg/kg, respectively. The onset of action in the IT group (127 +/- 17 s) was significantly earlier than that in the IM group (267 +/- 62 s), and significantly later than that in the IV group (18 +/- 7 s) (P < 0.05 by analysis of variance and the Tukey-Kramer analysis). The duration of action in the IT group (794 +/- 162 s) was significantly longer than that in the IV group (93 +/- 30 s) but not significantly different from that in the IM group (743 +/- 131 s). The recovery index in the IT group (134 +/- 30 s) was significantly shorter than that in the IM group (222 +/- 47 s) and significantly longer than that in the IV group (32 +/- 12 s). Although IT administration of vecuronium is still slower than IV administration, it appears to be more advantageous as compared with IM administration, given the more rapid absorption and faster onset of action.

Comparative effects of bupivacaine and ropivacaine on intracellular calcium transients and tension in ferret ventricular muscle.

BACKGROUND: Recent evidence suggests that ropivacaine exerts markedly less cardiotoxicity compared with bupivacaine; however, the mechanisms are not fully understood at the molecular level. METHODS: Isolated ferret ventricular papillary muscles were microinjected with the Ca-binding photoprotein aequorin, and intracellular Ca transients and tension were simultaneously measured during twitch in the absence and presence of bupivacaine or ropivacaine. RESULTS: Bupivacaine and ropivacaine (10, 30, and 100 microm) reduced peak systolic [Ca]i and tension in a concentration-dependent manner. The effects were significantly greater for bupivacaine, particularly on tension (approximately twofold). The percentage reduction of tension was linearly correlated with that of [Ca]i for both anesthetics, with the slope of the relationship being approximately equal to 1.0 for ropivacaine and approximately equal to 1.3 for bupivacaine (slope difference, P < 0.05), suggesting that the cardiodepressant effect of ropivacaine results predominantly from inhibition of Ca transients, whereas bupivacaine suppresses Ca transients and the reaction beyond Ca transients, i.e., myofibrillar activation, as well. BAY K 8644, a Ca channel opener, abolished the inhibitory effects of ropivacaine on Ca transients and tension, whereas BAY K 8644 only partially inhibited the effects of bupivacaine, particularly the effects on tension. CONCLUSION: The cardiodepressant effect of bupivacaine is approximately twofold greater than that of ropivacaine. Bupivacaine suppresses Ca transients more markedly than does ropivacaine and reduces myofibrillar activation, which may at least in part underlie the greater inhibitory effect of bupivacaine on cardiac contractions. These results suggest that ropivacaine has a more favorable profile as a local anesthetic in the clinical settings.

[Survey Report on International Cooperation 2001--report of the Japanese Society of Anesthesiologists Committee on International Affairs].

A survey was conducted in November 2001 with a questionnaire entitled "Survey Report on International Cooperation" compiled by the International Affairs of the Japanese Society of Anesthesiologists (JSA). The survey focused on member awareness of the importance of international cooperation by sending the questionnaire to its entire membership. Replies were received from approximately 15.6% of the membership or, to be exact, 1,353 JSA members. The survey produced several remarkable findings, which are as follows: 57.8% of the respondents are interested in international cooperation, 86.8% regard international cooperation as necessary, and 38.4% are willing to participate in international cooperation. Those who have actually engaged in international cooperation in the past account for only 7.5%, indicating that there are a good number of members who have not had a chance to provide assistance in international cooperation, their willingness notwithstanding. Regarding their employers' levels of understanding of this issue, 30.6% responded that their managements either recommend active participation or approve of the respondents' intention. Another 24.9% replied that their managements agreed to their participation on condition that they do so privately. Thus, a total of 55.5% of the respondents have permission to participate in international cooperation. Regarding the level of understanding from family members, 41.2% replied that their families agree to their desire irrespective of whether or not their services overseas are relevant to their profession. This figure became 72.4% when their services abroad would be relevant to their profession. On the other hand, 16.0% of the respondents (216 members) stated that they have no interest in international cooperation. For the reasons, 38.8% replied that the issue cannot be viewed as a matter worthy of immediate attention, 10.2% replied that it is not their problem, and 24.1% replied that this will involve dangers. When questioned about their overall impressions from actual participation in international cooperation in the past, among the 102 members responding, 88.2% said they are satisfied with what they have done, 4.9% were undecided as to whether or not they are satisfied, while none of them responded negatively about their services. Of those who are satisfied with their services, as many as 54.4% found their services "worthy of the time spent because of all the excitement involved and because each activity involved work other than their own profession," and 40.0% found them "worthy of their time and labor." Particularly noteworthy is the fact that 6.7% now consider activities in international cooperation "their divinely appointed work in life," and 65.7% hope to participate in international cooperation again. From these findings, it can be deduced that there are few obstacles to the members' international cooperation and that JSA's potential as a promoter of international cooperation may be highly estimated.

Comparison of sprotte and Quincke needles with respect to spinal fluid leakage using artificial spinal cord.

PURPOSE: This research investigated whether the Sprotte needle causes less leakage of CSF than the Quincke needle in the artificial spinal cord. METHODS: The changes in intradural pressure, extradural pressure, and leaked volume of CSF were evaluated following puncture with Sprotte and Quincke needles in the artificial spinal cord. RESULTS: The decrease in intradural pressure was 9.7±1.8 mm H2O with the Sprotte needle and 20.5±2.7 mm H2O with the Quincke needle (P<0.05). The volume of leakage of artificial CSF was 2.0±0.3 ml with the Sprotte needle and 3.3 ±0.3 ml with the Quincke needle (P<0.01). The extradural pressure increase was 166.1±8.2 mm H2O with the Sprotte needle and 186.8±13.2 mm H2O with the Quincke needle (P<0.05). CONCLUSION: The Sprotte needle produces less CSF leakage than the Quincke needle.