[Current status of portable disposable infusers]

Portable disposable infusers are widely used for treatment of various types of pain including postoperative pain and cancer pain, because they are simple to use, of lightweight, and inexpensive. In Japan, nine series of infusers are available from eight manufacturers. Volumes and flow rates of various infusers used for pain therapy widely vary from 40 to 500 ml and from 0.5 to 15 ml x hr(-1), respectively. Several infusers have flow selectors and/or patient-controlled analgesia circuits. Such a wide variety enables us to select optimal infusers for individual patients and thus to offer adequate pain control to those patients suffering from severe pain.

Relationship Between Real-Time Monitoring of the Graft Motility and Mucosal Histology in Swine Intestinal Transplantation

We studied the correlation between the motility and the mucosal histology of the small bowel seeking to detect rejection in an early stage by real-time monitoring using a swine model. Intestinal transplantation (ITx) was performed orthotopically using FK506 immunosuppression. The distal about 20 cm segment of the allograft was exteriorized as a Thiry-Vella stoma for biopsies. Strain gauge (SG) force transducers were attached to the graft for real-time monitoring of graft motility. Pigs without ITx were used as controls (group 1). Rejection was classified into four groups by histologic findings: nonrejection (group 2), mild rejection (group 3), moderate rejection (group 4), and severe rejection (group 5). Migrating motor complex (MMC) phase III was analyzed for the following parameters: duration, amplitude, interval, motility index, velocity, and frequency of propagation. In group 2, all parameters were almost the same as those for group 1. In contrast, groups 4 and 5 showed most parameters significantly lower than those in group 1. In group 3, the contractility of the MMC was not significantly altered, but the frequency of the propagation was decreased significantly. In conclusion, graft motility detected by a real-time SG method correlated with the grade of mucosal histology. This method is useful to detect rejection at an early stage by examining the frequency of MMC propagation.

Inhibition of morphine tolerance by processed Aconiti tuber is mediated by kappa-opioid receptors

Previously, we found that processed Aconiti tuber (PAT) could inhibit morphine tolerance in mice. In the present study, we investigated mechanisms underlying this effect. Mice received subcutaneous (s.c.) morphine (10 mg/kg) and oral PAT at a subanalgesic dose (0.3 g/kg), once a day for 12 days. Additional PAT-treated groups received morphine and PAT, at 120 min after pretreatment with s.c. clocinnamox mesylate (C-CAM) (0.5 mg/kg), or nor-binaltorphimine (nor-BNI) (5 mg/kg). The antinociceptive effect was assessed with the tail pressure test, at 60 min after the daily s.c. morphine injections were given. In the placebo-treated group, repeated morphine injections caused morphine tolerance, and morphine antinociception was abolished by day 6, whereas in PAT-treated groups, significant antinociception was maintained until day 12, suggesting that PAT inhibited morphine tolerance, thereby sustaining morphine antinociception. C-CAM, a selective mu-opioid receptor (MOR) antagonist, blocked morphine antinociception whereas nor-BNI, a selective kappa-opioid receptor (KOR) antagonist, did not. However, both C-CAM and nor-BNI could block the antinociception maintained by the morphine-PAT combination. Results of the study suggested that chronic treatment with PAT at a subanalgesic dose maintained MOR-mediated morphine antinociception by attenuating development of morphine tolerance, and that this tolerance-attenuating effect of PAT was mediated by KOR.

Variable Very-High-Energy Gamma-Ray Emission from the Microquasar LS I +61 303

Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes.

Effects of deep hypothermic circulatory arrest with retrograde cerebral perfusion on electroencephalographic bispectral index and suppression ratio

OBJECTIVE

No systematic study has been conducted to investigate effects of deep hypothermic circulatory arrest (DHCA) on electroencephalographic bispectral index (BIS) and suppression ratio (SR). Thus, the effects of DHCA were evaluated on BIS and SR.

DESIGN

A prospective clinical study.

SETTING

University hospital (single institute).

PARTICIPANTS

Twenty consecutive patients undergoing thoracic aortic surgery using DHCA under narcotics-sevoflurane anesthesia.

INTERVENTIONS

BIS and SR were monitored during cardiopulmonary bypass, simultaneously with nasopharyngeal temperature (NPT).

MEASUREMENTS AND MAIN RESULTS

BIS decreased to 0 with induction of deep hypothermia and rose again with rewarming, although rates of BIS changes in response to cooling and rewarming varied widely among patients. Typically, BIS decreased slowly until NPT reached 26 degrees C during cooling and then it began to decrease rapidly and reached 0 at 17 degrees C, in inverse proportion to SR, which increased rapidly with deep hypothermia and reached 100% at 17 degrees C. When SR was 50% or more, BIS was determined by SR according to the expression: BIS = 50-SR/2. With rewarming, BIS rose again and returned to precooling baseline levels. Time to the beginning of the BIS recovery significantly correlated with duration of DHCA.

CONCLUSIONS

With induction of deep hypothermia, BIS decreased in a biphasic manner to 0 at rates varying among patients. With rewarming, BIS rose again at rates extremely widely varying among patients. The rate of BIS recovery was related to duration of DHCA. BIS may be capable of conveniently tracing suppression and recovery of a part of cerebral electrical activity before, during, and after DHCA.

Effects of processed Aconiti tuber and its ingredient alkaloids on the development of antinociceptive tolerance to morphine

Processed Aconiti tuber (PAT) is a herbal medicine that has been widely used as an analgesic since ancient times. We investigated effects of subanalgesic doses of PAT on morphine tolerance in mice. Mice received subcutaneous morphine (10 mg/kg) and oral PAT at subanalgesic doses (0.1 or 0.3 g/kg), once a day for 7 days. Mechanical nociceptive thresholds were measured using the tail pressure test, at 60 min after the daily s.c. morphine injections. In the placebo-treated group, repeated administration of s.c. morphine resulted in development of analgesic tolerance. In the PAT-treated groups, oral PAT attenuated morphine tolerance, dose-dependently. The main ingredient alkaloid of PAT causing its tolerance-attenuating activity was mesaconitine, but other ingredient alkaloids, such as aconitine and hypaconitine, also contributed to this activity. In addition, repeated treatment with PAT could reverse already-developed morphine tolerance. Subanalgesic doses of oral PAT thus can attenuate and reverse morphine tolerance in mice.

Pain-relieving effects of processed Aconiti tuber in CCI-neuropathic rats

Neuropathic pain is often refractory to conventional pain therapies and thus requires exploration of effective drugs. We evaluated if processed Aconiti tuber (PAT), a traditional oriental herbal medicine that has been used as an analgesic, relieves neuropathic pain in the rat chronic constriction injury (CCI) model. Ten to 14 days after CCI in the right hind paw, six groups of rats received oral placebo, or PAT at 0.5, 1, 2, 3, or 5 g/kg. Additional groups received oral PAT, 2 g/kg, after pretreatment with intraperitoneal naloxone; intraperitoneal nor-binaltorphimine (norBNI); or intrathecal norBNI. As indicators of mechanical allodynia and thermal hyperalgesia, the pressure threshold of paw withdrawal (PWT) in response to linearly increasing pressure, and latency to paw withdrawal (PWL) in response to radiant heat, were measured before and after drug administration. Oral PAT dose-dependently increased PWT and PWL, which had been decreased due to CCI. The increases in PWT and PWL by oral PAT were inhibited by intraperitoneal and intrathecal norBNI: a selective kappa-opioid receptor antagonist, but not by intraperitoneal naloxone. These results indicate that oral PAT can alleviate mechanical allodynia and thermal hyperalgesia, dose-dependently, via spinal kappa-opioid receptor mechanisms in a rat CCI neuropathic pain model.

Clinical application of adenosine and ATP for pain control

This review summarizes clinical application of adenosine and adenosine 5'-triphosphate (ATP) in pain conditions. Investigations have been performed in patients with acute perioperative pain or chronic neuropathic pain treated with intravenous adenosine or ATP, or intrathecal adenosine. Characteristic central adenosine A1 receptor-mediated pain-relieving effects have been observed after intravenous adenosine infusion in human inflammation/sensitization pain models and in patients with chronic neuropathic pain. Adenosine compounds, in low doses, can reduce allodynia/hyperalgesia more consistently than spontaneous pain, suggesting that these compounds affect neuronal pathophysiological mechanisms involved in central sensitization. Such pain-relieving effects, which are mostly mediated via central adenosine A1 receptor activation, have a slow onset and long duration of action, lasting usually for hours or days and occasionally for months. With acute perioperative pain, treatment with a low-dose infusion of adenosine compounds and the A1 receptor-mediated central antisensitization mechanisms may play only a minor part in the total perioperative pain experience. By administering sufficient doses of adenosine compounds during surgery, however, significant and long-lasting perioperative pain relief can be achieved via central A1 receptor-mediated antinociceptive/analgesic actions as well as via peripheral A2a or A3 receptor-mediated antiinflammatory actions. Thus, adenosine compounds have significant potential for alleviating various types of pain.

How individual sensitivity to opiates can be predicted by gene analyses

Opiate analgesics are widely used and abused drugs. Individual differences in opiate sensitivity can hamper effective pain treatments and increase risks of drug abuse. Although genetic factors might affect individual differences in opiate sensitivity, scientific evidence for specific genetic mechanisms that underlie these differences has been sparse. Recent studies using inbred and knockout mice have revealed that the mu opioid peptide (MOP) receptor encoded by the Oprm1 gene has a mandatory role in the analgesic and addictive properties of opiate drugs. Increasing evidence suggests that differences in Oprm1 gene sequences affect the amount of Oprm1 mRNA and sensitivity to opiates, and >100 polymorphisms have been identified in the human OPRM1 gene, some of which are related to vulnerability to drug dependence in some populations. Rapid advances in this research field are leading to improved understanding of the relationships between gene polymorphisms and opiate sensitivities that will enable more-accurate prediction of the opiate sensitivity and opiate requirements in individual patients.

Analgesic effect of intravenous ATP on postherpetic neuralgia in comparison with responses to intravenous ketamine and lidocaine

PURPOSE

No study has been performed on the analgesic effect of adenosine 5'-triphosphate (ATP) on postherpetic neuralgia (PHN). We conducted an open-label trial of ATP in patients with PHN, and compared ATP with ketamine and lidocaine.

METHODS

Twelve patients with PHN were studied. On separate days, ketamine (0.3 mg.kg(-1)), lidocaine (2 mg.kg(-1)), and ATP (100 microg.kg(-1).min(-1) or less for 120 min) were administrated intravenously. The intensity of spontaneous pain as well as tactile allodynia was assessed using a visual analog scale (VAS). When the VAS score for spontaneous pain was decreased by more than 50%, the patient was classified as a responder.

RESULTS

Five, 6, and 6 patients responded to ketamine, lidocaine, and ATP, respectively. In 6 ATP responders, pain relief developed slowly and lasted for 9 (median) h (range: 3-72 h). All 5 ketamine responders and only 1 of 7 ketamine nonresponders responded to ATP (5/5 vs 1/7, P < 0.05, chi2 test) whereas 2 of 6 responders to lidocaine and 4 of 6 nonresponders to lidocaine responded to ATP (2/6 vs 4/6, P > 0.05). The ketamine responders responded to ATP more often than did the lidocaine responders (5/5 vs 2/6, P < 0.05).

CONCLUSION

Intravenous ATP exerted slowly developing and long-lasting analgesic effects in half of patients with PHN. Patients with ketamine-responsive PHN were likely to respond to ATP.

A rabbit model for evaluation of surgical anesthesia and analgesia: characterization and validation with isoflurane anesthesia and fentanyl analgesia

PURPOSE

With a clamp test, quantitative estimation of the level of surgical anesthesia/analgesia is not easy. We have developed a rabbit pain model allowing for quantitative evaluation of the level of surgical anesthesia/analgesia using both electrical and mechanical stimuli as simulated surgical stimuli. We evaluated whether this model allows for accurate tracing of dynamically changing levels of surgical anesthesia/analgesia induced by isoflurane and fentanyl.

METHODS

Eight rabbits tracheotomized and vascularly cannulated under 3% isoflurane anesthesia were placed on a sling that allowed for free movement of the head and extremities. After the isoflurane concentration was reduced stepwise to 1.5% and then to 0%, four graded doses of fentanyl (5, 10, 20, and 40 microg.kg(-1)) were injected intravenously at intervals of 120 min. At each dose, anesthetic/analgesic end-point variables were determined, including the number of animals behaviorally unresponsive to clamping the forepaw (nonresponders) and the threshold voltage of subcutaneous electrical stimulation (2, 5, and 50 Hz) required to evoke the head lift (HLT: pain detection/arousal threshold: sedative/hypnotic index) and the escape movement (EMT: pain tolerance threshold: analgesic index).

RESULTS

With increasing doses of isoflurane and fentayl, HLTs and EMTs, especially those at 5 Hz, increased dose-dependently and proportionately to increases in the number of nonresponders to clamping the forepaw, a standard indicator of the anesthetic/analgesic level.

CONCLUSION

Using the HLT and EMT, especially at 5 Hz, combined with a clamp test, this rabbit model allows for repeated, quantitative, and distinctive evaluation of the dynamically changing levels of both sedative/hypnotic and analgesic components of surgical anesthesia/analgesia.

Change in Bispectral Index During Epileptiform Electrical Activity Under Sevoflurane Anesthesia in a Patient with Epilepsy

We observed abnormal fluctuation in Bispectral Index (BIS) caused by repeated alternations between two electroencephalographic (EEG) waveform patterns in a patient with a recent history of epileptic seizure under sevoflurane anesthesia. The repetitive development of the abnormal EEG changes (slow delta with or without spike) and the fluctuation in BIS disappeared almost immediately after administration of anticonvulsants. BIS may give useful information not only on the sedative-hypnotic state, but also on the development of and recovery from abnormal epileptiform EEG activity.

IMPLICATIONS

During epileptiform electroencephalographic activity (EEG), the Bispectral Index shows an abnormal fluctuation caused by repeated abrupt alterations between normal EEG and abnormal epileptiform EEG patterns.

Cerebral ischaemia during cardiac surgery in children detected by combined monitoring of BIS and near-infrared spectroscopy

BACKGROUND

Children frequently suffer transient cerebral ischaemia during cardiac surgery. We measured cerebral ischaemia in children during cardiac surgery by combining two methods of monitoring.

METHODS

We studied 65 children aged between 5 months and 17 yr having surgery to correct non-cyanotic heart disease using hypothermic cardiopulmonary bypass (CPB). During surgery, we measured the Bispectral Index (BIS) and regional cerebral haemoglobin oxygen saturation (SrO2) with near-infrared spectroscopy (NIRS). Cerebral ischaemia was diagnosed if both SrO2 and BIS decreased abruptly when acute hypotension occurred. In each patient, the relationship between SrO2 and arterial blood pressure (AP) was indicated by a plot of mean SrO2 against simultaneous mean AP.

RESULTS

We noted 72 episodes of cerebral ischaemia in 38 patients. Sixty-three ischaemic events were during CPB. Cerebral ischaemia was less frequent in older patients. Cerebral ischaemia was more common and more frequent in children under 4 yr old. Haematocrit during CPB was lower and SrO2 was more dependent on AP in children under 4 yr.

CONCLUSIONS

Children less than 4 yr of age are more likely to have cerebral ischaemia caused by hypotension during cardiac surgery. Ineffective cerebral autoregulation and haemodilution during CPB may be responsible.

An animal model for surgical anesthesia and analgesia: characterization with isoflurane anesthesia and remifentanil analgesia

With a traditional clamp test alone, quantitative evaluation of the level of surgical anesthesia/analgesia is not easy. We have developed a rabbit model that allows for repeated quantification of the varying level of surgical anesthesia/analgesia using both mechanical and electrical stimulation as simulated surgical stimuli. After tracheostomy and intravascular cannulations under isoflurane anesthesia, eight rabbits were placed on a sling that allowed for free movement of the head and extremities. The inspired isoflurane concentration was reduced from 3% to 1.5% and then to 0%. Remifentanil was then infused at 4 graded infusion rates (0.1-0.8 microg. kg(-1) x min(-1)). At each drug dose, analgesic variables were determined including the number of animals behaviorally unresponsive to clamping the forepaw (nonresponders) and threshold voltage of subcutaneous electrical stimulation (2 Hz, 5 Hz, and 50 Hz) required to evoke the head lift (HLT, pain detection/arousal threshold) and escape movement responses (EMT, pain tolerance threshold). With increasing drug doses, HLTs and EMTs at 5 Hz increased dose-dependently and most proportionately to increases in the number of nonresponders, a standard indicator of the anesthetic/analgesic level. Therefore, using the HLT and EMT at 5 Hz combined with a clamp test, this rabbit model allows for quantitative evaluation of the varying level of surgical anesthesia/analgesia.

IMPLICATIONS

We have developed a rabbit model of surgical anesthesia and analgesia using both mechanical and electrical stimulation as simulated surgical stimuli, which allows for repeated, quantitative, and qualitative evaluation of the varying level of surgical anesthesia and analgesia, differentiation between sedative/hypnotic and analgesic components of drug actions, and simultaneous monitoring of all the clinically relevant physiological variables including cardiovascular and respiratory variables.

Detection of Acute Tolerance to the Analgesic and Nonanalgesic Effects of Remifentanil Infusion in a Rabbit Model

Although acute tolerance to analgesia develops rapidly with remifentanil, it is unknown whether acute tolerance also develops to its nonanalgesic effects. We investigated the analgesic and cardiorespiratory effects of remifentanil during a continuous infusion in a rabbit model. Ten tracheotomized New Zealand White rabbits with arterial and venous accesses were placed on a sling that allowed for reasonably free movement. In spontaneously breathing conscious animals, remifentanil was infused IV at a constant-rate of 0.3 microg kg(-1)x min(-1) for 360 min. Sedative/analgesic and cardiorespiratory variables were assessed repeatedly during remifentanil infusion, including the number of animals behaviorally unresponsive to clamping the forepaw (nonresponders) and subcutaneous electrical stimulation thresholds required to elicit head lift (HLT: pain detection/arousal threshold) and escape movement responses (EMT: pain tolerance threshold). Within 60-120 min of starting the infusion, the number of nonresponders, HLT, EMT, and PaCO(2) increased significantly, whereas blood pressure, heart rate, and respiratory rate decreased. Thereafter, all variables returned towards preinfusion levels despite continuing infusion. These results indicate that during a remifentanil infusion acute tolerance develops for both its analgesic and cardiorespiratory effects.

IMPLICATIONS

Using a new rabbit model, we found that during continuous, constant-rate remifentanil infusion acute tolerance developed within the first few hours, not only to its analgesic but also to its cardiovascular and respiratory effects, albeit in slightly different time courses.

Detection of cerebral hypoperfusion with bispectral index during paediatric cardiac surgery

BACKGROUND

The bispectral index (BIS) may indicate changes in cerebral activity when the cerebral circulation is affected by acute hypotension.

METHODS

We measured BIS and cerebral haemoglobin saturation (Sr(O(2))) by near-infrared spectroscopy in 10 children undergoing cardiac surgery.

RESULTS

We noted 14 episodes of simultaneous decreases in Sr(O(2)) and BIS during acute hypotension in five children. An acute decrease in BIS, which coincided with a decrease in Sr(O(2)) suggesting a reduction in cerebral blood flow, was associated with acute slowing of the raw EEG waveforms.

CONCLUSIONS

Our findings suggest that an acute decrease in BIS during acute hypotension indicates cerebral hypoperfusion, and that cerebral hypoperfusion caused by hypotension may occur frequently during paediatric cardiac surgery.

[A case of post-radiation therapy patient with difficulty in intubation unexpected preoperatively]

We experienced a post-radiation therapy patient who had a narrow trachea, and presented with unexpected difficulty for intubation. His trachea was narrowest at 2 cm below the glottis. The fiberscope barely could pass the narrowest part of the trachea. We speculate that the radiation therapy induced his tracheal constriction. Careful attention is necessary when examining the post-radiation therapy patients. Multiple cervical radiographs are necessary in such a case.