Defective brain development in mice lacking the Hif-1alpha gene in neural cells

Hypoxia-inducible factor 1alpha (HIF-1alpha) is essential for vascular development during embryogenesis and pathogenesis. However, little is known about its role in brain development. To investigate the function of HIF-1alpha in the central nervous system, a conditional knockout mouse was made with the Cre/LoxP system with a nestin promoter-driven Cre. Neural cell-specific HIF-1alpha-deficient mice exhibit hydrocephalus accompanied by a reduction in neural cells and an impairment of spatial memory. Apoptosis of neural cells coincided with vascular regression in the telencephalon of mutant embryos, and these embryonic defects were successfully restored by in vivo gene delivery of HIF-1alpha to the embryos. These results showed that expression of HIF-1alpha in neural cells was essential for normal development of the brain and established a mouse model that would be useful for the evaluation of therapeutic strategies for ischemia, including hypoxia-mediated hydrocephalus.

Efficacy of oral clonidine premedication in children

BACKGROUND

Clonidine, an alpha 2-adrenoceptor agonist, has been shown to be effective as a preanesthetic medication in adults. The current study was designed to investigate the efficacy of two doses of oral clonidine as a premedicant preceding oral atropine in children.

METHODS

In a prospective, randomized, double-blind, controlled clinical trial, 105 children, aged 4-12 yr, undergoing elective ophthalmologic surgery received 0.4 mg/kg diazepam, 2 micrograms/kg clonidine, or 4 micrograms/kg clonidine orally. These agents mixed with apple juice were administered 105 min before the estimated time of induction of anesthesia, and were followed by treatment with 0.03 mg/kg oral atropine 60 min before anesthesia. A blinded observer noted the children's level of sedation, quality of separation from parents, and degree of acceptance of mask application during inhalation of nitrous oxide used for establishment of venous access. Anesthesia was induced with 5 mg/kg thiamylal, and tracheal intubation was facilitated with 0.2 mg/kg vecuronium. Hemodynamic changes after tracheal intubation were compared among the three groups.

RESULTS

Clonidine produced significant sedation, and the effect was dose related. Clonidine, 4 micrograms/kg, provided better quality of separation and acceptance of mask than the two other regimens. This dose of clonidine attenuated the increases in blood pressure and heart rate after tracheal intubation. No clinically significant perioperative hypotension or bradycardia was observed.

CONCLUSIONS

These data indicate that, even in pediatric surgery, the combination of 4 micrograms/kg and 0.03 mg/kg oral clonidine is an effective premedication. However, the safety and optimal dose of clonidine in this setting remain to be determined.

Tumor necrosis factor-alpha (TNF-alpha) plays a protective role in acute viralmyocarditis in mice: A study using mice lacking TNF-alpha

BACKGROUND

It has been reported that tumor necrosis factor-alpha (TNF-alpha) is expressed in the heart with viral myocarditis and that its expression aggravates the condition. The pathophysiological effects of TNF-alpha on viral myocarditis, however, have not been fully elucidated.

METHODS AND RESULTS

To investigate the role of TNF-alpha in the progression of viral myocarditis, we used TNF-alpha gene-deficient mice (TNF-alpha(-/-)) and induced acute myocarditis by infection with encephalomyocarditis virus (EMCV). The survival rate of TNF-alpha(-/-) mice after EMCV infection was significantly lower than that of TNF-alpha(+/+) mice (0% versus 67% on day 14). Injection of recombinant human TNF-alpha (0.2 to 4.0 microg/mouse IV) improved the survival of TNF-alpha(-/-) mice in a dose-dependent manner, indicating that TNF-alpha is essential for protection against viral myocarditis. The levels of viral titer and viral genomic RNA of EMCV in the myocardium were significantly higher in TNF-alpha(-/-) than in TNF-alpha(+/+) mice. Histopathological examination showed that the inflammatory changes of the myocardium were less marked in TNF-alpha(-/-) than in TNF-alpha(+/+) mice. Immunohistochemical analysis revealed that the levels of immunoreactivity of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in the myocardium were decreased in TNF-alpha(-/-) mice compared with TNF-alpha(+/+) mice.

CONCLUSIONS

These observations suggested that TNF-alpha is necessary for adhesion molecule expression and to recruit leukocytes to inflammatory sites, and thus, the lack of this cytokine resulted in failure of elimination of infectious agents. We concluded that TNF-alpha plays a protective role in the acute stage of viral myocarditis.

Effect of lidocaine pretreatment on endotoxin-induced lung injury in rabbits

BACKGROUND

It is well known that endotoxin causes acute lung injury resulting in adult respiratory distress syndrome. Numerous cellular and humoral factors such as macrophages, neutrophils, platelets, and inflammatory mediators (e.g., activated complements, cytokines, and arachidonic acid metabolites) are thought to play a pivotal role in the pathogenesis of endotoxin-induced lung injury. Furthermore, pulmonary edema in acute lung injury is associated with an increase in vascular permeability that may arise from a perturbation of the endothelial cell surface membrane. Lidocaine has been shown to inhibit function of these cells and stabilize cell membranes. The aim of the current study was to determine whether pretreatment with intravenous lidocaine could attenuate acute lung injury induced by endotoxin in rabbits.

METHODS

Twenty-seven anesthetized male rabbits were randomly assigned to receive one of three treatments (n = 9 for each group); infusion of saline (as a control), infusion of Escherichia coli endotoxin (30 micrograms kg-1 over a 60-min period) without treatment with lidocaine, and infusion of endotoxin with treatment with lidocaine. A single dose of intravenous lidocaine 2 mg.kg-1 was administered 10 min before infusion of endotoxin and thereafter infused at a rate of 2 mg.kg-1.h-1 until 6 h after the start of endotoxin administration, when the animals were killed. The lungs of the rabbits were ventilated with 40% oxygen. Hemodynamics, peripheral leukocytes counts, and arterial oxygen tension were recorded during the ventilation period. After the observation, lung mechanics, cell fraction of bronchoalveolar lavage fluid (BALF), activated complements, cytokines, and arachidonic acid metabolites concentrations in BALF were measured and analyzed. The lung wet-to-dry-weight ratio and albumin concentrations in BALF were analyzed as an indices of pulmonary edema. The cypridina luciferin analog-dependent chemiluminescence (representing superoxide production) by neutrophils isolated from the pulmonary artery and light microscopic findings were compared among the three groups.

RESULTS

Endotoxin caused decreases in peripheral leukocyte counts, lung compliance, and arterial oxygen tension, and increases in the lung wet-to dry-weight ratio, polymorphonuclear cell counts in BALF, and albumin, C3a, C5a, tumor necrosis factor alpha, interleukin-1 beta, and thromboxane B2 concentrations in BALF. Lidocaine pretreatment attenuated these changes. The cypridina luciferin analog--dependent chemiluminescence was greater in rabbits receiving endotoxin than in the control. Lidocaine pretreatment attenuated the increase in chemiluminescence. Endotoxin caused extensive morphologic lung damage, which was lessened by lidocaine.

CONCLUSIONS

These results suggest that intravenous lidocaine pretreatment has a prophylactic effect on endotoxin-induced lung injury in rabbits. However, further studies are required to investigate the therapeutic (as an early posttreatment) effect of the drug given after lung injury because rabbits in the current study received lidocaine before endotoxemia.

Intravenous lidocaine attenuates acute lung injury induced by hydrochloric acid aspiration in rabbits

BACKGROUND

Neutrophils play a crucial role in the pathogenesis of acid-induced acute lung injury. Lidocaine inhibits the function of neutrophils. This study aimed to determine whether lidocaine attenuates acute lung injury induced by hydrochloric acid (HCl) instillation.

METHODS

In study 1, rabbits were divided into four groups (n = 7 each). Lung injury was induced by intratracheal HCl (0.1 N, 3 ml/kg) in two groups. The other two groups received saline intratracheally. Lidocaine given intravenously (2 mg/ g bolus + 2 mg x kg(-1) x h(-1) infusion) was started 10 min before intratracheal instillation in one HCl and one saline group, and saline was given intravenously in the other two groups. In study 2, rabbits (four groups of seven animals each) received HCl (0.1 N, 3 ml/kg) intratracheally. Treatment with intravenous lidocaine was started 10 min before, 10 min after, or 30 min after acid instillation, or saline was given intravenously 10 min before instillation.

RESULTS

In study 1, HCl caused deterioration of the partial pressure of oxygen (PaO2), lung leukosequestration, decreased lung compliance, and increased the lung wet-to-dry weight ratio and albumin, interleukin-6 (IL-6), and IL-8 levels in bronchoalveolar lavage fluid. Lidocaine pretreatment attenuated these changes. Hydrochloric acid increased superoxide anion production by neutrophils and caused morphologic lung damage, both of which were lessened by lidocaine. In study 2, lidocaine given 10 min after acid instillation was as effective as pretreatment in PaO2, lung mechanics, and histologic examination. However, PaO2 changes in lidocaine 30 min after injury were similar to those in saline given intravenously.

CONCLUSIONS

Intravenous lidocaine started before and immediately after acid instillation attenuated the acute lung injury, in part by inhibiting the sequestration and activation of neutrophils.

3-Hydroxyanthranilic acid, an L-tryptophan metabolite, induces apoptosis in monocyte-derived cells stimulated by interferon-gamma

3-Hydroxyanthranilic acid (3-HAA), a metabolite of L-tryptophan, accumulates in monocyte-derived cells (THP-1), but not in other cell lines tested (MRC-9, H4, U373MG, Wil-NS), following immune stimulation that induces indoleamine-2,3-dioxygenase (IDO), a rate-limiting enzyme in the L-tryptophan kynurenine pathway. We examined whether metabolites of the L-tryptophan-kynurenine pathway act to induce apoptosis in monocytes/macrophages. Of the L-tryptophan metabolites tested, only 3-HAA at a concentration of 200 micromol/L was found to induce apoptosis in THP-1 and U937 cells. The addition of ferrous or manganese ions further enhanced apoptosis and free radical formation by 3-HAA in these two types of cells. The apoptotic response induced by 3-HAA was significantly attenuated by the addition of antioxidant, alpha-tocopherol or Trolox (a water-soluble analogue of vitamin E), and the xanthine oxidase inhibitor, allopurinol. In addition, the 3-HAA-induced apoptotic response was slightly attenuated by catalase, but not by superoxide dismutase (SOD), indicating that generation of hydrogen peroxide is involved in this response. Interferon-gamma (IFN-gamma), an inducer of IDO, potently induced apoptosis in THP-1 cells, but not in U937 cells, in the presence of ferrous or manganese ions. This different susceptibility to apoptosis inducer between THP-1 and U937 cells may depend on the capacity of the cells for 3-HAA synthesis following IDO induction by IFN-gamma. Furthermore, apoptosis was suppressed by cycloheximide in THP-1 cells, suggesting that newly synthesized proteins may be essential for apoptotic events. These results suggest that 3-HAA induces apoptosis in monocytes/macrophages under inflammatory or other pathophysiological conditions.

Lidocaine attenuates hyperoxic lung injury in rabbits

BACKGROUND

High concentrations of oxygen acute lung injury. Neutrophils are thought to play a pivotal role in the pathogenesis of this lung injury through the release of oxygen radicals, neutral proteases, and lysosomal enzymes. Lidocaine has been shown to inhibit neutrophil function. We examined whether intravenous pretreatment with lidocaine attenuated acute lung injury induced by hyperoxia.

METHOD

Twenty-seven anaesthetized male rabbits were allocated to receive one of three treatments (n = 9 for each group): ventilation with 100% oxygen for 36 h with and without lidocaine treatment, and ventilation with air for 36 h without lidocaine. In the lidocaine-treated group, a single intravenous lidocaine 2 mg/kg was administered immediately after the initiation of exposure to 100% oxygen; thereafter, the lidocaine was infused at a rate of 2 mg.kg(-1).h(-1) for 36 h until the animals were sacrificed. Haemodynamics, PaO2, and lung mechanics were recorded during the ventilation period. After exposure, the lung mechanics and cell fraction in bronchoalveolar lavage fluid (BALF) were measured and analyzed, as was the concentration of activated complements, and cytokines in BALF. The lung wet-to dry- (W/D) weight ratio and albumin concentrations in BALF were analyzed as an index of pulmonary oedema. We also compared the chemiluminescence of neutrophils isolated from the pulmonary artery, and light microscopic findings, in the three groups.

RESULTS

Pure oxygen for 36 h caused no significant changes in haemodynamics, lung mechanics, or PaO2/FiO2 ratio. However, hyperoxia significantly increased the lung W/D weight ratio, the influx of neutrophils into the lung, and BALF concentrations of C3a, C5a, TNF-alpha, IL-1 beta, and albumin. Lidocaine attenuated these increases (W/D ratio: 5.7 vs 5.1, %PMN: 19.2% vs 1.6%, C3a: 62 ng/dl vs 14 ng/dl, C5a: 7.9 ng/dl vs 4.1 nd/dl, TNF-alpha: 25 fmol/ml vs 2.8 fmol/ml, IL-1 beta: 36 fmol/ml vs 2.2 fmol/ml, and albumin: 9.5 mg/dl vs 2.8 mg/dl, all: P < 0.05). The chemiluminescence was increased in hyperoxic compared with in normoxic rabbits and lidocaine treatment attenuated the increase (opsonized zymosan stiluated: 3.7 x 10(6) cpm vs 2.3 x 10(6) cpm, P < 0.05). Exposure to 100% oxygen caused extensive morphologic lung damage which was lessened by lidocaine (lung injury score (mean): 3 vs 4, P < 0.05).

CONCLUSION

These findings suggest that intravenous lidocaine has a prophylactic effect on initial hyperoxic lung injury (pulmonary vascular permeability, histopathological, and biochemical BALF changes) in rabbits. The effects of lidocaine on more severe lung injury (decreased oxygenation) caused by hyperoxia for 72 h deserve further study.

Propofol inhibits human neutrophil functions

Neutrophils play important roles in the antibacterial host defense mechanism and in the pathogenesis of tissue injury. Propofol has been reported to impair the production of reactive oxygen species from neutrophils. We examined the effect of propofol (2,6-diisopropylphenol), at clinically relevant concentrations and at 10 and 100 times this concentration, on several aspects of human neutrophil functions using an in vitro system. Propofol significantly inhibited chemotaxis, phagocytosis, and reactive oxygen species (ROS) (O2-, H2O2, OH) production of neutrophils in a dose-dependent manner. At clinically relevant concentrations, propofol suppressed these neutrophil functions, but it did not decrease ROS generation by the cell-free (xanthine-xanthine oxidase) system. Increase in intracellular calcium concentrations in neutrophils stimulated by N-formyl-L-methionyl-L-leucyl-L-phenylalanine was dose-dependently attenuated by propofol. This decreasing effect on [Ca2+]i in neutrophils may represent one of the mechanisms responsible for the inhibition of neutrophil functions by propofol.

IMPLICATIONS

Neutrophils play a pivotal role in the antibacterial host defense system and tissue injury. We found that at clinically relevant concentrations, propofol impaired neutrophil functions. Further studies may determine whether this impairment, observed in vitro, leads to clinical immunological suppression.

Cloning and expression of a Streptomyces cholesterol oxidase gene in Streptomyces lividans with plasmid pIJ702

The cholesterol oxidase gene (cho) of Streptomyces sp. was cloned into Streptomyces lividans with the vector pIJ702. Deletion analysis of the recombinant plasmid showed that entire coding sequence of the cho gene was located within a 2.5-kilobase segment of the chromosomal DNA obtained from the cholesterol oxidase-producing strain. When cloned cells of S. lividans were grown in an appropriate medium, the cells produced severalfold more cholesterol oxidase extracellularly than did the producing strain.

Crucial role of group IIA phospholipase A(2) in oleic acid-induced acute lung injury in rabbits

Group IIA secretory phospholipase A(2) (sPLA(2)) has been implicated in a variety of inflammatory diseases including acute lung injury (ALI); however, the role of sPLA(2) in this disorder remains unclear. The aim of the present investigation was to examine the role of this enzyme in a model of ALI induced by oleic acid (OA) in rabbits by testing human group IIA phospholipase A(2) (PLA(2)) inhibitor, S-5920/LY315920Na. Experimental groups consisted of a saline control group (n = 8), an OA control group (n = 10) infused intravenously with OA (0.1 ml/kg/h for 2 h), and three groups given OA + S-5920/LY315920Na (three different doses, n = 8, respectively). Infusion of OA provoked pulmonary hemorrhage and edema formation, protein leakage, and massive neutrophil infiltration, resulting in severe hypoxemia and impaired lung compliance. PLA(2) activity was detected in the bronchoalveolar lavage fluid (BALF), but not plasma, which correlated well with severity of lung injury in this model. Pretreatment with S-5920/LY315920Na diminished the OA-induced PLA(2) activity in the BALF and dose-dependently attenuated the previously described lung injury induced by OA, accompanied by protection against lung surfactant degradation and production of thromboxane A(2) (TXA(2)) and leukotriene B(4) (LTB(4)). S-5920/LY315920Na also inhibited the OA-induced production of interleukin-8 (IL-8), both in plasma and BALF. Thus, sPLA(2) appears to play a key role in OA-induced lung injury, suggesting that the group IIA PLA(2) inhibitor may be a promising agent for patients with acute respiratory distress syndrome (ARDS).

Comparison of nicardipine, diltiazem and verapamil for controlling the cardiovascular responses to tracheal intubation

We have compared the efficacy of three calcium channel blockers, nicardipine, diltiazem and verapamil, in attenuating the cardiovascular responses to laryngoscopy and intubation in 60 normotensive patients (ASA I) undergoing rapid sequence induction of anaesthesia with thiopentone and fentanyl. We also examined whether or not these blockers inhibited catecholamine release induced by intubation. The patients were allocated to one of four groups (n = 15 for each): saline (control), nicardipine 30 micrograms kg-1, diltiazem 0.2 mg kg-1 or verapamil 0.1 mg kg-1. Verapamil and the three other drugs were administered 45 s and 60 s before the start of direct laryngoscopy, respectively, in a double-dummy design. Anaesthesia was induced with thiopentone 4 mg kg-1 i.v. and fentanyl 2 micrograms kg-1 i.v. Tracheal intubation was facilitated with vecuronium 0.2 mg kg-1. During anaesthesia, ventilation was assisted or controlled with 1% isoflurane and 50% nitrous oxide in oxygen. Laryngoscopy lasting 30 s was attempted 2 min after administration of thiopentone and vecuronium. Patients receiving saline exhibited significant increases in systolic and diastolic arterial pressures (AP), heart rate (HR) and plasma concentrations of catecholamines associated with tracheal intubation. The increase in AP was attenuated in patients treated with any calcium channel blocker. The greatest effect was elicited by verapamil, which attenuated the increase in HR, although nicardipine seemed to enhance tachycardia. All three drugs failed to suppress the increase in plasma catecholamine concentrations in response to tracheal intubation. These findings suggest that bolus injection of verapamil 0.1 mg kg-1 was a more effective method of controlling hypertension and tachycardia associated with intubation than diltiazem 0.2 mg kg-1 or nicardipine 30 micrograms kg-1, and that these prophylactic effects were not caused by inhibition of the catecholamine response.

Oral clonidine premedication reduces vomiting in children after strabismus surgery

This is a prospective randomized double-blind trial conducted to determine whether preoperative orally administered clonidine causes or potentiates postoperative vomiting in 140 children (3-12 yr) undergoing strabismus surgery. They were all inpatients and classified randomly into four groups (n = 35 each); placebo (control), diazepam 0.4 mg.kg-1, clonidine 2 micrograms.kg-1, and clonidine 4 micrograms.kg-1. These agents were administered 93-112 min (mean; 100 min) before the anticipated time of induction of anaesthesia. All children received inhalational anaesthesia with halothane and nitrous oxide in oxygen. Muscle relaxation in all patients was obtained with vecuronium and residual neuromuscular blockade was antagonized with neostigmine and atropine before tracheal extubation. Diclofenac suppository was prescribed to prevent postoperative pain. No opioids or postoperative antiemetics were administered. All children remained in hospital for two days postoperatively. The incidence and frequency of vomiting were compared in the groups with Kruskall-Wallis Rank test. Clonidine 4 micrograms.kg-1 caused a lower incidence and frequency of vomiting than did placebo and diazepam (incidence and frequency: 11% and 1.37% and 3, and 34% and 2 in clonidine 4 micrograms.kg-1, placebo, and diazepam, respectively; P < 0.05 for clonidine 4 micrograms.kg-1 vs placebo and diazepam). However, low-dose clonidine was ineffective. These data suggest that preanaesthetic medication with clonidine 4 micrograms.kg-1 may be useful for preventing emesis following strabismus surgery. This property of clonidine indicates that it may be superior to other sedative premedicants such as diazepam and midazolam.

Fentanyl attenuates cardiovascular responses to tracheal extubation

We carried out a controlled, randomized, double-blind study to examine the effects of intravenous fentanyl (1 or 2 micrograms kg-1) on hemodynamic changes during tracheal extubation and emergence from anesthesia in 60 ASA physical status I or II patients undergoing elective gynecological surgery. Anesthesia was maintained with 0.5%-1.5% isoflurane and 60% nitrous oxide (N2O) in oxygen. Muscle relaxation was achieved with vecuronium. The patients were randomly assigned to three group (each, n = 20), and fentanyl (1 or 2 micrograms kg-1), or saline (as a control) was given at the time of peritoneal closure. Changes in heart rate (HR) and blood pressure (BP) were measured during and after tracheal extubation. Adverse effects, including postoperative sedation and respiratory depression, were also assessed. The HR, systolic BP, and diastolic BP increased significantly during tracheal extubation in the control group (P < 0.05). Fentanyl 2 micrograms kg-1 attenuated the increases in these variables more effectively than fentanyl 1 microgram kg-1. The time interval from the study drug to extubation was similar in each group. Postoperative somnolence and respiratory depression were not observed in any patients in any of the three groups. We concluded that a bolus dose of intravenous fentanyl 2 micrograms kg-1 given at the time of peritoneal closure was of value in attenuating the cardiovascular changes associated with tracheal extubation and emergence from anesthesia, and that this treatment did not prolong the recovery. However, further studies are required to assess this technique in patients with cardiovascular or cerebrovascular diseases.

Regional distribution and age-dependent expression of N-acylphosphatidylethanolamine-hydrolyzing phospholipase D in rat brain

The endocannabinoid anandamide (N-arachidonoylethanolamine) and other bioactive long-chain N-acylethanolamines are thought to be formed from their corresponding N-acylphosphatidylethanolamines by a specific phospholipase D (NAPE-PLD) in the brain as well as other tissues. However, regional distribution of NAPE-PLD in the brain has not been examined. In the present study, we investigated the expression levels of NAPE-PLD in nine different regions of rat brain by enzyme assay, western blotting and real-time PCR. The NAPE-PLD activity was detected in all the tested brain regions with the highest activity in thalamus. Similar distribution patterns of NAPE-PLD were observed at protein and mRNA levels. We also found a remarkable increase in the expression levels of protein and mRNA of the brain NAPE-PLD with development, which was in good agreement with the increase in the activity. The age-dependent increase was also seen with several brain regions and other NAPE-PLD-enriched organs (heart and testis). p-Chloromercuribenzoic acid and cetyltrimethylammonium chloride, which inhibited recombinant NAPE-PLD dose-dependently, strongly inhibited the enzyme of all the brain regions. These results demonstrated wide distribution of NAPE-PLD in various brain regions and its age-dependent expression, suggesting the central role of this enzyme in the formation of anandamide and other N-acylethanolamines in the brain.

Oral clonidine premedication reduces minimum alveolar concentration of sevoflurane for tracheal intubation in children

BACKGROUND

Sevoflurane is a useful anesthetic for inhalational induction in children because of its low solubility in blood and relatively nonpungent odor. Clonidine has sedative and anxiolytic properties and reduces the requirement for inhalation agents. Nitrous oxide (N2O) also decreases the requirement of inhaled anesthetics, but the effect is variable. The minimum alveolar concentration for tracheal intubation (MAC(TI)) of sevoflurane was assessed with and without N2O and clonidine premedication.

METHODS

Seventy-two patients, aged 3-11 yr, were assigned to one of six groups (n = 12 each). They received one of three preanesthetic medications (two groups for each premedication): placebo (control), 2 microg/kg oral clonidine or 4 microg/kg oral clonidine. In one group of each premedication, anesthesia was induced with sevoflurane in oxygen; in the other group, anesthesia was induced with sevoflurane in the presence of 60% N2O. Each concentration of sevoflurane at which tracheal intubation was attempted was predetermined according to Dixon's up-and-down method and held constant for at least 20 min before the trial

RESULTS

The MAC(TI) of sevoflurane in the absence of N2O (mean +/- SEM) was 3.2 +/- 0.2%, 2.5 +/- 0.1%, and 1.9 +/- 0.2% in the control, 2-microg/kg clonidine, and 4-microg/kg clonidine groups, respectively. Nitrous oxide (60%) decreased the MAC(TI) of sevoflurane by 26%, 24%, and 27% in the control, 2-microg/kg clonidine, and 4-microg/kg clonidine groups.

CONCLUSIONS

Oral clonidine premedication decreased the MAC(TI) of sevoflurane. Nitrous oxide also decreased the MAC(TI). The combination of clonidine and N2O lessened the MAC(TI) of sevoflurane more than did either drug alone.

Reversible hypophosphatemia during moderate hypothermia therapy for brain-injured patients

OBJECTIVE

Because plasma potassium, which may similarly change as plasma phosphate (P), decreases during moderate hypothermia, plasma P, a requisite electrolyte for the cell function, may alter during therapeutic moderate hypothermia for brain-injured patients. In 22 such patients who underwent moderate hypothermia or were treated with normothermia, plasma concentrations of P and other chemicals were examined.

DESIGN

A prospective study.

SETTING

The intensive care unit of a medical university hospital.

PATIENTS AND INTERVENTIONS

In 15 consecutive patients with brain injury who underwent moderate hypothermia and 7 serial patients treated with normothermia, plasma concentrations of P, potassium, glucose, blood gas tension and pH, daily urine volume, and water balance were examined. Inequality in the numbers of patients of the two groups was the result of patient exclusion because of multiple trauma, aluminum hydroxide administrations, hyperventilation, preexisting diabetes mellitus, or administration of insulin. Daily blood sampling was done around 8 am. Inclusion criteria included a Glasgow Coma Scale score assessment < or = 8 at admission to the emergency room and evidence of injury on computerized tomography scanning of the brain.

MEASUREMENT AND MAIN RESULTS

Hypothermia decreased plasma P levels as compared with those of normothermia within 4 days after the injury (this period was similar to the duration of the hypothermic phase in the hypothermia group). Such reduction related to changes in blood glucose levels, but not to any in the urine volume, or water balance. The P decrease occurred during the hypothermic phase, but subsequently there was a recovery of P after the rewarming phase. The changes in plasma potassium levels were similar to those in plasma P concentrations during the course. Such changes were accompanied by a recovery of decreased heart rate that occurred during the hypothermic phase.

CONCLUSION

The results suggest that moderate hypothermia of 32-33 degrees C decreases plasma P levels. Further studies are required to examine whether P repletion may overcome certain hemodynamic derangements during moderate hypothermia in brain-injured patients.

Effects of 2-, 4- and 12-hour fasting intervals on preoperative gastric fluid pH and volume, and plasma glucose and lipid homeostasis in children

We evaluated 105 randomly-selected unpremedicated children aged 1-14 years to determine the effects of a 2-, 4- and 12-h preoperative fasting interval on the preoperative gastric fluid pH and volume, and plasma glucose and lipid homeostasis. Each child undergoing elective surgery ingested a large volume (approximately 10 ml/kg b.w.) of apple juice and then fasted for 2, 4 or 12 h before the estimated induction of anaesthesia. After induction of anaesthesia, gastric fluid was aspirated through a large-bore, multiorifice orogastric tube. Plasma concentrations of glucose, total ketone bodies, non-esterified fatty acid (NEFA), triglycerides, and cortisol were measured at the time of induction to evaluate the fasting interval effects on preoperative plasma glucose and lipid homeostasis. There were no significant differences between the three groups in either gastric fluid volume or pH. In addition, there were no significant differences between the groups with respect to the proportion with a pH < 2.5 and volume > 0.4 ml/kg b.w. Neither plasma concentrations of glucose, triglycerides, nor cortisol at the time of anaesthetic induction differed between the three groups. Both 4 and 12 h nil per os (NPO) caused an increase in lipolysis, which was presumably a compensatory mechanism to maintain normoglycaemia. The plasma NEFA and total ketone bodies concentrations were therefore significantly higher in these two fasting intervals than in 2 h NPO. These data suggest that a 2-h NPO, after a large volume of ingested apple juice, may offer additional benefits by preventing an increase in lipolysis during the fasting interval without either increasing the volume of gastric fluid or decreasing the gastric pH.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effect of local anaesthetics on reactive oxygen species production by human neutrophils

BACKGROUND

Reactive oxygen species (ROS) generated from neutrophils accumulated in various major organs are thought to play a pivotal role in the pathogenesis of host auto-injury. Lidocaine has been shown to reduce the injury. We investigated the effect of local anaesthetics (lidocaine, mepivacaine and bupivacaine) on ROS production by neutrophils using an in vitro system.

METHODS

We measured the production of superoxide (ferricytochrome c method), hydrogen peroxide (H2O2: scopoletin fluorescence technique), and hydroxyl radical (OH.: ethylene gas method) by neutrophils isolated from human adult volunteers in the absence and presence of lidocaine (2-200 micrograms/mL), mepivacaine (3-300 micrograms/mL), and bupivacaine (3-300 micrograms/mL). We also measured the ROS generation in a cell-free (xanthine-xanthine oxidase) system.

RESULTS

Lidocaine and mepivacaine at higher levels significantly decreased the production of ROS by neutrophils. However, these local anaesthetics at clinically relevant blood concentrations had no effect on the levels of ROS. Furthermore, lidocaine and mepivacaine failed to reduce ROS generated by the cell-free system. Bupivacaine did not decrease ROS generation by either generating system.

CONCLUSION

In conclusion, in the present in vitro system, only concentrations of lidocaine and mepivacaine 100-fold higher than clinically feasible ones reduced ROS production by human neutrophils. However, the local anaesthetics at clinically relevant blood concentrations had no suppressive effect. Further studies using in vivo systems are required to elucidate the inhibitory effects of local anaesthetics on ROS generation in clinical settings.

Clonidine decreases the dose of thiamylal required to induce anesthesia in children

Clonidine is a useful drug to give preoperatively because it produces anxiolysis, sedation, and hemodynamic stability, and reduces intravenous and volatile anesthetic requirements. Several premedicants, including midazolam and diazepam, have been shown to reduce the induction dose of intravenous anesthetics, such as thiopental, ketamine, or propofol. A randomized, double-blind controlled study was conducted to evaluate the effect of premedication with oral clonidine on thiamylal requirement for the induction of anesthesia and on associated hemodynamic changes in children. Sixty children (ASA grades I-II, 7-12 yr old) were assigned randomly to receive one of three treatments (n = 20, for each group): placebo (control), clonidine 2 micrograms/kg, or clonidine 4 micrograms/kg 105 min before the induction of anesthesia. Thiamylal was injected at a dose of 1 mg/kg every 15 s until loss of the eyelash reflex and the dose was recorded. Blood pressure (BP), heart rate (HR), and arterial oxygen saturation were recorded every minute from the beginning of injection of thiamylal for 5 min. Significant decreases in thiamylal dose were observed in patients receiving clonidine. The induction dose of thiamylal (mean +/- SD) was 5.4 +/- 0.9, 4.5 +/- 1.1, and 3.4 +/- 0.9 mg/kg for patients receiving placebo, clonidine 2 micrograms/kg, and clonidine 4 micrograms/kg, respectively (P < 0.05). Systolic BP decreased by 6.8%, 5.6%, and 6.6% and HR increased by 5.7%, 4.8%, and 4.1% after administration of thiamylal in the control (placebo) group and the clonidine 2 micrograms/kg and clonidine 4 micrograms/kg groups, respectively (P > 0.05). Premedication with oral clonidine reduced the dose of intravenous thiamylal required for the induction of anesthesia in children.

The effect of diltiazem on the cardiovascular response to tracheal intubation

The efficacy of diltiazem in the attenuation of the cardiovascular response to laryngoscopy and tracheal intubation was studied in patients who received 0.2 or 0.3 mg/kg diltiazem 60 seconds before the start of laryngoscopy. These data were compared with a control group who received saline. Each group consisted of 10 patients who had elective surgery. Patients who received saline showed a significant increase in mean arterial pressure and rate pressure product associated with tracheal intubation. These increases after tracheal intubation were reduced in diltiazem-treated patients compared with those of the control group (p less than 0.05). The data suggest that a bolus injection of diltiazem is a simple, practical and effective method to attenuate the hypertensive response to laryngoscopy and tracheal intubation.