Agitation and changes of Bispectral Index and electroencephalographic-derived variables during sevoflurane induction in children: clonidine premedication reduces agitation compared with midazolam.
(65/245)
BACKGROUND: This double-blind randomized study was undertaken to assess agitation, Bispectral Index (BIS) and EEG changes during induction of anaesthesia with sevoflurane in children premedicated with midazolam or clonidine. METHODS: Children were allocated randomly to receive rectal midazolam 0.4 mg kg(-1) (n=20) or oral clonidine 4 microg kg(-1) (n=20) as premedication. Rapid induction of anaesthesia was achieved with inhalation of sevoflurane 8% in nitrous oxide 50%-oxygen 50%. After tracheal intubation, the children's lungs were mechanically ventilated and the inspired sevoflurane concentration was adjusted to achieve an end-tidal fraction of 2.5%. The EEG and BIS were recorded during induction until 10 min after tracheal intubation. The EEG was analysed using spectral analysis at five points: baseline, loss of eyelash reflex, 15 s before the nadir of the BIS (BIS(nadir)), when both pupils returned to the central position (immediately before intubation), and 10 min after intubation. RESULTS: Agitation was observed in 12 midazolam-treated and five clonidine-treated patients (P=0.05). At baseline, EEG rhythms were slower in the clonidine group. Induction of anaesthesia was associated with similar EEG changes in the two groups, with an increase in total spectral power and a shift towards low frequencies; these changes were maximal around the end of the second minute of induction (BIS(nadir)). When the pupils had returned to the central position, fast EEG rhythms increased and BIS was higher than BIS(nadir) (P<0.05). In both groups, agitation was associated with an increase in slow EEG rhythms at BIS(nadir). CONCLUSIONS: Compared with midazolam, clonidine premedication reduced agitation during sevoflurane induction. During induction with sevoflurane 8% (oxygen 50%-nitrous oxide 50%), the nadir of the BIS occurred at the end of the second minute of inhalation. Agitation was associated with a more pronounced slowing of the EEG rhythms at BIS(nadir) compared with inductions in which no agitation was observed. The BIS may not follow the depth of anaesthesia during sevoflurane induction in children. (+info)
Cardioprotective effects of desflurane: effect of timing and duration of administration in rat myocardium.
(66/245)
BACKGROUND: We compared the cardioprotective effects of 1 minimum alveolar concentration (MAC) desflurane administered before, during or after ischaemia, or throughout the experiment (before, during and after ischaemia) on myocardial infarct size following 30 min occlusion of the left anterior descending coronary artery and 3 h reperfusion in adult rats. METHODS: Fifty male Sprague-Dawley rats were anaesthetized with pentobarbital, intubated and mechanically ventilated. Blood gases, pH and body temperature (37.5-38 degrees C) were controlled. Heart rate and arterial pressure were measured continuously. Animals were randomly assigned to the following groups (n=10 in each group): pentobarbital only ("Pento"); 15 min desflurane administration followed by 10 min of washout before 30 min ischaemia and 3 h reperfusion ("Precond"); 30 min desflurane administration during ischaemia period ('Isch'); desflurane administration during the 15 first min of reperfusion ("Reperf") and desflurane administration throughout the experiment (before, during and after ischaemia; "Long"). Volumes at risk and infarct sizes were assessed by Indian ink and with 2,3,5-triphenyltetrazolium chloride staining, respectively. RESULTS: Physiological parameters and volumes at risk were not significantly different between groups. In the Pento group, mean myocardial infarct size was 65 (sd 15)% of the volume at risk; myocardial infarct size was reduced to a significant and comparable extent in the desflurane-treated groups (Precond 42 (14)%; Isch 34 (11)%; Reperf 41 (15)%; Long 33 (10)%; P<0.0002 vs Pento group). CONCLUSIONS: In rats, desflurane 1 MAC significantly decreased myocardial infarct size whatever the period and duration of administration. (+info)
The diuretic effect of Sairei-to is mediated by nitric oxide production in pentobarbital-anesthetized rats.
(67/245)
Sairei-to (TJ-114), a Japanese traditional medicine, has been used clinically for the treatment of various edematous disorders. The inhibitory effect on edema may be dependent on the diuretic response to TJ-114. This study was conducted to clarify the mechanism of diuresis. Pentobarbital-anesthetized rats were infused with a saline solution intravenously (0.4 mL/30 min). Urine was collected through a bladder cannula for 30 min. Intraduodenal administration of TJ-114 (0.5 - 1.5 g/kg) resulted in a dose-dependent increase of urine volume with insignificant urinary sodium excretion and significant urea excretion, but no effect on mean arterial blood pressure. Furthermore, TJ-114 significantly increased urinary levels of NO(2) + NO(3). In addition, intraperitoneal pre-treatment with 6 mg/kg of N(G)-nitro-L-arginine methyl ester inhibited the increase in urine volume, urinary urea excretion, and urinary levels of NO(2) + NO(3) in the rats treated with TJ-114. These results suggest that TJ-114 induces a diuretic response via production of NO. (+info)
Anesthesia for ambulatory anorectal surgery.
(68/245)
The prevalence of minor anorectal diseases is 4-5% of adult Western population. Operations are performed on ambulatory or 24-hour stay basis. Requirements for ambulatory anesthesia are: rapid onset and recovery, ability to provide quick adjustments during maintenance, lack of intraoperative and postoperative side effects, and cost-effectiveness. Anorectal surgery requires deep levels of anesthesia. The aim is achieved with 1) regional blocks alone or in combination with monitored anesthesia care or 2) deep general anesthesia, usually with muscle relaxants and tracheal intubation. Modern general anesthetics provide smooth, quickly adjustable anesthesia and are a good choice for ambulatory surgery. Popular regional methods are: spinal anesthesia, caudal blockade, posterior perineal blockade and local anesthesia. The trend in regional anesthesia is lowering the dose of local anesthetic, providing selective segmental block. Adjuvants potentiating analgesia are recommended. Postoperative period may be complicated by: 1) severe pain, 2) urinary retention due to common nerve supply, and 3) surgical bleeding. Complications may lead to hospital admission. In conclusion, novel general anesthetics are recommended for ambulatory anorectal surgery. Further studies to determine an optimal dose and method are needed in the group of regional anesthesia. (+info)
Stepwise sedation is safe and effective for the insertion of central venous catheters.
(69/245)
BACKGROUND: The introduction of a central venous catheter in haemodialysis patients is an unpleasant procedure for the patient. Intravenous sedation is accepted practice in complicated endoscopic procedures but not often used in haemodialysis patients. METHODS: We developed a protocol for the use of stepwise sedation in these patients with the use of midazolam and fentanyl. RESULTS: Stepwise sedation with midazolam and fentanyl was used in 155 procedures. No or minor movements were observed in 94% of 154 procedures. 88% of the 155 procedures were graded as very easy or easy. No or only very slight recall of the procedure were noted in 86% of 133 procedures. Only in 7% of 132 procedures were the patients able to recollect most of the procedure. No, or only a small amount of pain was recollected in 93% of 131 procedures. The most important complication was a slight decrease in oxygen saturation in 23 procedures. In the second part of the study we compared the effects of sedation with midazolam alone versus the combination of midazolam and fentanyl for the introduction of Tesio catheters. Amnesia, ease of procedure and the recollection of pain were equivalent. Oxygen desaturation occurred significantly less often with the use of midazolam alone. CONCLUSION: We conclude that stepwise sedation is effective and safe in haemodialysis patients and leads to a complete amnesia for the procedure. (+info)
Effects of anesthetics on systemic hemodynamics in mice.
(70/245)
The aim of this study was to compare the systemic hemodynamic effects of four commonly used anesthetic regimens in mice that were chronically instrumented for direct and continuous measurements of cardiac output (CO). Mice (CD-1, Swiss, and C57BL6 strains) were instrumented with a transit-time flow probe placed around the ascending aorta for CO measurement. An arterial catheter was inserted into the aorta 4 or 5 days later for blood pressure measurements. After full recovery, hemodynamic parameters including stroke volume, heart rate, CO, mean arterial pressure (MAP), and total peripheral resistance were measured with animals in the conscious state. General anesthesia was then induced in these mice using isoflurane (Iso), urethane, pentobarbital sodium, or ketamine-xylazine (K-X). The doses and routes of administration of these agents were given as required for general surgical procedures in these animals. Compared with the values obtained for animals in the conscious resting state, MAP and CO decreased during all anesthetic interventions, and hemodynamic effects were smallest for Iso (MAP, -24 +/- 3%; CO, -5 +/- 7%; n = 15 mice) and greatest for K-X (MAP, -51 +/- 6%; CO, -37 +/- 9%; n = 8 mice), respectively. The hemodynamic effects of K-X were fully antagonized by administration of the alpha(2)-receptor antagonist atipamezole (n = 8 mice). These results indicate that the anesthetic Iso has fewer systemic hemodynamic effects in mice than the nonvolatile anesthetics. (+info)
GHB (gamma-hydroxybutyrate) carrier-mediated transport across the blood-brain barrier.
(71/245)
gamma-Hydroxybutyrate (sodium oxybate, GHB) is an approved therapeutic agent for cataplexy with narcolepsy. GHB is widely abused as an anabolic agent, euphoriant, and date rape drug. Recreational abuse or overdose of GHB (or its precursors gamma-butyrolactone or 1,4-butanediol) results in dose-dependent central nervous system (CNS) effects (respiratory depression, unconsciousness, coma, and death) as well as tolerance and withdrawal. An understanding of the CNS transport mechanisms of GHB may provide insight into overdose treatment approaches. The hypothesis that GHB undergoes carrier-mediated transport across the BBB was tested using a rat in situ brain perfusion technique. Various pharmacological agents were used to probe the pharmacological characteristics of the transporter. GHB exhibited carrier-mediated transport across the BBB consistent with a high-capacity, low-affinity transporter; averaged brain region parameters were V(max) = 709 +/- 214 nmol/min/g, K(m) = 11.0 +/- 3.56 mM, and CL(ns) = 0.019 +/- 0.003 cm(3)/min/g. Short-chain monocarboxylic acids (pyruvic, lactic, and beta-hydroxybutyric), medium-chain fatty acids (hexanoic and valproic), and organic anions (probenecid, benzoic, salicylic, and alpha-cyano-4-hydroxycinnamic acid) significantly inhibited GHB influx by 35 to 90%. Dicarboxylic acids (succinic and glutaric) and gamma-aminobutyric acid did not inhibit GHB BBB transport. Mutual inhibition was observed between GHB and benzoic acid, a well known substrate of the monocarboxylate transporter MCT1. These results are suggestive of GHB crossing the BBB via an MCT isoform. These novel findings of GHB BBB transport suggest potential therapeutic approaches in the treatment of GHB overdoses. We are currently conducting "proof-of-concept" studies involving the use of GHB brain transport inhibitors during GHB toxicity. (+info)
The role of gamma-aminobutyric acid and glutamate for hypoxic ventilatory response in anesthetized rabbits.
(72/245)
Acute hypoxia produces an increase in ventilation. When the hypoxia is sustained, the initial increase in ventilation is followed by a decrease in ventilation. Hypoxia causes changes in brain neurotransmitters depending on its severity and durations. The purpose of this study was to investigate the role of gamma-aminobutyric acid (GABA) and glutamate for hypoxic ventilatory response in rabbits. The experiments were performed in peripheral chemoreceptors intact and denervated rabbits anesthetized with Na-pentobarbitate. For intracerebroventricular (ICV) injections of reagents in each animal, cannula was placed in left lateral cerebral ventricle by stereotaxic method. After ICV injection of GABA (0.48 mg/kg), air breathing in both groups caused a depression of respiratory activity. On the other hand, after ICV injection of GABA, breathing of hypoxic gas mixture (8% O(2)-92% N(2)) in both groups produced the hypoxic hyperventilation. After ICV injection of GABA, blockade of GABA(A) receptors with bicuculline (0.2 mg/kg) did not prevent the hypoxic hyperventilation. In contrast, after ICV GABA injection, blockade of glutamate NMDA receptors with MK-801 (0.09 mg/kg) completely abolished the hypoxic hyperventilation observed while the animals were breathing hypoxic gas mixture. Our findings suggest that ICV injection of GABA causes respiratory depression in normoxic conditions, and that it increases ventilation in hypoxic conditions with or without peripheral chemoreceptor impulses by increasing glutamate. (+info)