Tatsuya Fuchigami

Propofol reduces spinal motor neuron excitability in humans.

IMPLICATIONS We investigated in humans whether changes in spinal motor neuron excitability correlate with the predicted propofol concentration (Cpt) achieved by a target-controlled infusion system. Propofol suppressed F-wave persistence in a Cpt-dependent manner, indicating that propofol depresses spinal motor neuron excitability at clinically relevant concentrations.

Spinal astrocyte glutamate receptor 1 overexpression after ischemic insult facilitates behavioral signs of spasticity and rigidity

Using a rat model of ischemic paraplegia, we examined the expression of spinal AMPA receptors and their role in mediating spasticity and rigidity. Spinal ischemia was induced by transient occlusion of the descending aorta combined with systemic hypotension. Spasticity/rigidity were identified by simultaneous measurements of peripheral muscle resistance (PMR) and electromyography (EMG) before and during ankle flexion. In addition, Hoffman reflex (H-reflex) and motor evoked potentials (MEPs) were recorded from the gastrocnemius muscle. Animals were implanted with intrathecal catheters for drug delivery and injected with the AMPA receptor antagonist NGX424 (tezampanel), glutamate receptor 1 (GluR1) antisense, or vehicle. Where intrathecal vehicle had no effect, intrathecal NGX424 produced a dose-dependent suppression of PMR [ED50 of 0.44 μg (0.33–0.58)], as well as tonic and ankle flexion-evoked EMG activity. Similar suppression of MEP and H-reflex were also seen. Western blot analyses of lumbar spinal cord tissue from spastic animals showed a significant increase in GluR1 but decreased GluR2 and GluR4 proteins. Confocal and electron microscopic analyses of spinal cord sections from spastic animals revealed increased GluR1 immunoreactivity in reactive astrocytes. Selective GluR1 knockdown by intrathecal antisense treatment resulted in a potent reduction of spasticiy and rigidity and concurrent downregulation of neuronal/astrocytic GluR1 in the lumbar spinal cord. Treatment of rat astrocyte cultures with AMPA led to dose-dependent glutamate release, an effect blocked by NGX424. These data suggest that an AMPA/kainate receptor antagonist can represent a novel therapy in modulating spasticity/rigidity of spinal origin and that astrocytes may be a potential target for such treatment.

Development of baclofen tolerance in a rat model of chronic spasticity and rigidity.

Systemic or spinal treatment with baclofen has been associated with the development of tolerance in patients with chronic spasticity. In the present study, we used a rat model of spinal ischemia-induced spasticity to characterize the development of baclofen tolerance after chronic intrathecal (i.t.) baclofen infusion. Following the induction of spinal ischemia and the development of behavioral spasticity, animals were implanted with i.t. catheters connected to osmotic pumps to continuously infuse baclofen (1.0 microg/0.5 microl/h). Hindleg peripheral muscle resistance (PMR) was measured periodically after initiation of chronic infusion and after bolus i.t. baclofen injection (1.0 microg). Peripheral muscle resistance was significantly decreased at the onset of baclofen infusion, however, after 5-7 days of infusion a progressive return of spasticity was noted, where baseline PMR values returned to preinfusion levels. At the same time, the efficacy of bolus i.t. baclofen treatment also decreased, where after 5 days of baclofen infusion 1.0 microg (i.t.) baclofen only reduced PMR by 10% (compared to 40-50% preinfusion). Baclofen efficacy progressively returned once continuous infusion was stopped. These data demonstrate that transient spinal ischemia leads to the development of spasticity which is sensitive to spinal baclofen. Chronic i.t. infusion leads to a progressive development of tolerance. This model offers potential to study tolerance mechanisms after spinal injury, and aid in drug discovery for use in baclofen-tolerant patients.

Influence of the Descending Thoracic Aortic Cross Clamping on Bispectral Index Value and Plasma Propofol Concentration in Humans

Background:In this study, the authors investigated changes in Bispectral Index (BIS) values and plasma propofol concentrations (Cp) after aortic cross clamping in the descending thoracic aortic aneurysm repair surgery during propofol anesthesia. Methods:Prospectively, in 10 patients undergoing thoracic aortic surgery during total intravenous anesthesia with propofol, BIS values were recorded during cross clamping of the descending thoracic aorta. In this study, the rate of propofol infusion was controlled to keep the BIS value between 30 and 60 throughout surgery. Simultaneously, Cp values in the blood samples taken from the right radial artery (area proximal to cross clamping) and the left femoral artery (area distal to cross clamping) were measured. Results:Approximately 15 min after initiating aortic cross clamping, BIS values in all cases started to decrease abruptly. Cp values of samples taken from the radial artery after cross clamping of the aorta were significantly (P < 0.05) increased compared with pre–cross clamp values (1.8 ± 0.4 &mgr;g/ml), and the mean Cp after aortic cross clamping varied between 3.0 and 5.3 &mgr;g/ml. In addition, there were significant differences in the Cp values between radial arterial and femoral arterial blood samples throughout aortic cross clamping. Cp values in samples from the radial artery were approximately two to seven times higher than those from the femoral artery. Conclusions:This study showed that Cp values increased and BIS values decreased rapidly after aortic cross clamping in thoracic aortic aneurysm repair surgery during propofol anesthesia. These findings suggested that all anesthesiologists should control the infusion rate carefully, taking the abrupt changes in its pharmacokinetics into consideration, especially during cross clamping of the descending thoracic aorta.

Potent suppression of stretch reflex activity after systemic or spinal delivery of tizanidine in rats with spinal ischemia-induced chronic spastic paraplegia

BACKGROUND Spasticity and rigidity are serious complications associated with spinal traumatic or ischemic injury. Clinical studies show that tizanidine (Tiz) is an effective antispasticity agent; however, the mechanism of this effect is still not clear. Tiz binds not only to α2-adrenoreceptors (AR) but also to imidazoline (I) receptors. Both receptor systems (AR+I) are present in the spinal cord interneurons and α-motoneurons. The aim of the present study was to evaluate the therapeutic potency of systematically or spinally (intrathecally [IT]) delivered Tiz on stretch reflex activity (SRA) in animals with ischemic spasticity, and to delineate supraspinal or spinal sites of Tiz action. EXPERIMENTAL PROCEDURES Animals were exposed to 10 min of spinal ischemia to induce an increase in SRA. Increase in SRA was identified by simultaneous increase in recorded electromyography (EMG) activity and ankle resistance measured during computer-controlled ankle dorsiflexion (40°/3 s) in fully awake animals. Animals with increased SRA were divided into several experimental subgroups and treated as follows: (i) Tiz administered systemically at the dose of 1 mg kg(-1), or IT at 10 μg or 50 μg delivered as a single dose; (ii) treatment with systemic Tiz was followed by the systemic injection of vehicle, or by nonselective AR antagonist without affinity for I receptors; yohimbine (Yoh), α2A AR antagonist; BRL44408 (BRL), α2B AR antagonist; ARC239 (ARC), nonselective AR and I(1) receptor antagonist; efaroxan (Efa), or nonselective AR and I(2) receptor antagonist; idazoxan (Ida); (iii) treatment with IT Tiz was followed by the IT injection of selective α2A AR antagonist; atipamezole (Ati). In a separate group of spastic animals the effect of systemic Tiz treatment (1 mg/kg) or isoflurane anesthesia on H-reflex activity was also studied. RESULTS Systemic and/or IT treatment with Tiz significantly suppressed SRA. This Tiz-mediated anti-SRA effect was reversed by BRL (5 mg kg(-1)), Efa (1 mg kg(-1)), and Ida (1 mg kg(-1)). No reversal was seen after Yoh (3 mg kg(-1)) or ARC (5 mg kg(-1)) treatment. Anti-SRA induced by IT Tiz (50 μg) was reversed by IT injection of Ati (50 μg). Significant suppression of H-reflex was measured after systemic Tiz treatment (1 mg/kg) or isoflurane (2%) anesthesia, respectively. Immunofluorescence staining of spinal cord sections taken from animals with spasticity showed upregulation of α2A receptor in activated astrocytes. CONCLUSIONS These data suggest that α2A AR and I receptors, but not α2B AR, primarily mediate the Tiz-induced antispasticity effect. This effect involves spinal and potentially supraspinal sites and likely targets α2A receptor present on spinal neurons, primary afferents, and activated astrocytes. Further studies using highly selective antagonists are needed to elucidate the involvement of specific subtypes of the AR and I receptors in the antispasticity effect seen after Tiz treatment.

Acute Respiratory Distress Syndrome due to Strongyloides stercoralis Infection in a Patient with Cervical Cancer

A 62-year-old woman complained of diarrhea and vomiting after receiving chemotherapy for cervical cancer in association with high doses of corticosteroids. Two months later, the patient developed acute respiratory distress syndrome, and numerous Strongyloides stercoralis parasites were found in the intrabronchial discharge. Ivermectin was administered daily until nematodes were no longer detected in the sputum, and the patients condition was successfully rescued. Antibodies for human T-cell lymphotropic virus-1 (HTLV-1) were positive. HTLV-1 infection and the administration of corticosteroids are known risk factors for strongyloides hyperinfection syndrome. Therefore, physicians should consider this disease in the differential diagnosis of patients from endemic areas who present with gastrointestinal symptoms under these risk factors.

Vascular hyperpermeability in pulmonary decompression illness: 'the chokes'.

Decompression illness (DCI) develops during or after diving. Pulmonary decompression illness (‘Chokes’) is rarely seen because the affected individual usually dies in the water. We encountered a rare and interesting case. A 60‐year‐old man complained of leg pain after diving. Despite rapid transfer to a nearby hospital, advanced respiratory failure and shock had set in. He was then transferred to our hospital for hyperbaric oxygen therapy (HBOT). On account of his poor general condition, we initially treated him in the intensive care unit without HBOT, where he showed extreme hyperpermeability and a high level of serum procalcitonin (PCT; 20.24 ng/mL). Despite large‐volume fluid therapy, severe intravascular dehydration and shock status remained. We assume that the injured endothelial cells induced vascular hyperpermeability and increased levels of inflammatory cytokines leading to the high serum PCT level. PCT might be a useful stress marker of endothelial damage and severity in DCI, including Chokes.

Unanticipated full stomach at anesthesia induction in a type I diabetic patient with asymptomatic gastroparesis

We encountered a case of unanticipated full stomach at anesthesia induction, despite a 12-h fasting period, in a type I diabetes patient with diabetic neuropathy presenting for elective vitrectomy for proliferative diabetic retinopathy. The patient had ingested seaweed 24 h prior to the surgery, and it was later found in the aspirated gastric content. Gastrointestinal dysfunction due to diabetic neuropathy and the high fiber content of the ingested seaweed are the probable causes of unanticipated full stomach in our case.

Intrathecal nicorandil and small-dose morphine can induce spastic paraparesis after a noninjurious interval of spinal cord ischemia in the rat.

We investigated the interaction between nicorandil, a K+ATP channel opener, and morphine on motor function after a noninjurious interval of spinal cord ischemia in the rat. Spinal ischemia was induced by aortic occlusion for 6 min with a balloon catheter in Sprague-Dawley rats. All animals received intrathecal (IT) injection of morphine (1–60 &mgr;g) 1 h after ischemia. In addition to IT injection of morphine, group M (control), group MN (combination of morphine and nicorandil), and group MNG (combination of morphine, nicorandil, and glibenclamide) received IT saline, nicorandil (10 &mgr;g), and both glibenclamide (10 &mgr;g) and nicorandil (10 &mgr;g) after 150 min of reperfusion, respectively. A quantal bioassay for the effect of IT morphine on neurological function after ischemia was performed to calculate 50% effective dose values (ED50) for inducing paraparesis at 3 h of reperfusion. The ED50 in group M and group MN was 15.1 ± 4.9 &mgr;g and 2.9 ± 1.0 &mgr;g of IT morphine, respectively (P < 0.05). In Group MNG, the dose-response curve shifted back to the right and the ED50 for inducing paraparesis was 11.6 ± 4.7 &mgr;g of IT morphine. The present study demonstrates that IT small-dose morphine combined with nicorandil induces spastic paraparesis after noninjurious interval of spinal cord ischemia in the rat.

Aberrant halt of syringe pump motion: an improved system to prevent false setting of the syringe

A syringe pump is used to inject precise doses of drugs having a strong action; for example, vasoactive drugs. Unexpected and undetected halt of a syringe pump can lead to potentially life-threatening complications. We experienced a sudden halt in the movement of a syringe pump (Terufusion syringe pump; Terumo, Tokyo, Japan) in two patients while administering norepinephrine in the intensive care unit (ICU). Fortunately, the patients had only transient hypotension, which was immediately detected and promptly treated, without any untoward sequelae. As a result of the occurrence of such cases, we conducted a detailed investigation of the causes of this sudden halt in the syringe pump. We could not reproduce the aberration of the syringe pump and thus could not specify the cause in the first patient. In the second patient, however, a false setting on the syringe was suspected to be the cause of the problem. In order to prove this, we tried to reproduce the situation where a syringe pump, due to a false syringe setting, abruptly terminated while giving a “syringe loss” warning, after a period of precise functioning. Once we had determined how a false setting of the syringe could occur without the syringe pump giving off an alarm from the onset, we collaborated with the Terumo Company to revise their current instruction manual to incorporate this as a warning. We also helped in the development of a new model, including a new safety feature that would prevent a false setting of the syringe from occurring at all. This new model was released in December 2003.