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PubMed1992

Spectral analysis of heart rate variability during isoflurane anesthesia.

The autonomic nervous system is an important neural control system for maintaining cardiovascular stability in humans. Analysis of heart rate variations may provide important clinical information on the influence of anesthesia on the autonomic nervous system and the central nervous system. Therefore, the effects of 1.0, 1.5, and 2.0 minimum alveolar concentrations of isoflurane anesthesia on beat-to-beat heart rate variations were studied in ten patients (ASA Physical Status 1). Spectral analysis was used to determine the intensity of the variations. For each power spectrum, the frequency components were identified as follows: 1) the parasympathetically mediated respiratory component (0.15-0.4 Hz) and 2) both parasympathetically and sympathetically mediated components (0.04-0.15 Hz). The latter was subdivided into the low-frequency component (0.04-0.09 Hz) of vasomotor origin and the mid-frequency component (0.09-0.15 Hz) of baroreceptor origin. Marked reductions in the power of heart rate variations, at all frequencies, were found during isoflurane anesthesia, indicating isoflurane decreased total autonomic nervous system activity. Isoflurane decreased the high-frequency and mid-frequency components in a concentration-dependent manner. The low-frequency component increased transiently at 1.5 minimum alveolar concentrations concomitant with the burst suppression in the electroencephalogram. The ratio of mid-frequency to high-frequency components did not change significantly during isoflurane anesthesia compared with the awake period. These frequency characteristics of heart rate variations during isoflurane anesthesia suggest there are dose-related decreases in autonomic nervous system activity in both the vagus and the cardiac sympathetic nerves.

Adult↗
PubMed1993

Dexmedetomidine alters the hemodynamic effects of desflurane and isoflurane in chronically instrumented dogs.

BACKGROUND: Previous studies have shown that desflurane and isoflurane produce similar hemodynamic actions. This investigation examined the cardiovascular effects of desflurane and isoflurane in the presence or absence of dexmedetomidine, a highly selective alpha 2-adrenergic agonist that may be clinically useful as a premedicant or anesthetic adjuvant. METHODS: Four groups, comprising 40 experiments, were performed using ten dogs that were chronically instrumented for measurement of aortic and left ventricular pressure, the maximum rate of increase of left ventricular pressure (dP/dtmax), diastolic coronary blood flow velocity, cardiac output, and subendocardial segment length. On separate experimental days, systemic and coronary hemodynamics were recorded, and plasma concentrations of catecholamines were measured with or without oral dexmedetomidine pretreatment (30 micrograms/kg) in the conscious state and after 15 min of equilibration at 1.0, 1.3, and 1.6 end-tidal MAC desflurane or isoflurane in a random fashion. RESULTS: In conscious dogs, dexmedetomidine significantly decreased heart rate, cardiac output, percent segment shortening (%SS), left ventricular dp/dtmax, myocardial oxygen consumption (as estimated by the pressure-work index), and plasma norepinephrine concentration. Concomitant increases in systemic and diastolic coronary vascular resistance were observed. Pretreatment with dexmedetomidine decreased peak increases in heart rate during desflurane and isoflurane anesthesia. Mean arterial pressure was reduced less by desflurane than by isoflurane in the absence of dexmedetomidine. This difference was abolished in dogs pretreated with dexmedetomidine. Desflurane, but not isoflurane, decreased cardiac output in dexmedetomidine-pretreated dogs when compared with untreated dogs. Concomitantly, systemic vascular resistance was greater in desflurane- versus isoflurane-anesthetized dogs pretreated with dexmedetomidine. No differences in myocardial contractility, as assessed by left ventricular dP/dtmax and %SS, were observed between desflurane and isoflurane groups in the absence or presence of dexmedetomidine. CONCLUSIONS: The results indicate that the cardiovascular actions of desflurane or isoflurane are similar in the absence or presence of dexmedetomidine; however, some differences between anesthetic groups were noted. In the presence of dexmedetomidine, systemic vascular resistance during desflurane anesthesia was higher when compared with that during isoflurane anesthesia, indicating that desflurane produces less pronounced direct effects on peripheral vascular tone. The concomitant greater reductions in cardiac output are consistent with greater impedance to left ventricular outflow in desflurane-anesthetized dogs pretreated with dexmedetomidine, because no differences in contractile function were observed between volatile anesthetics. In contrast, cardiac output during isoflurane anesthesia after pretreatment with oral dexmedetomidine is better maintained secondary to the peripheral vasodilator actions of this agent.

Adrenergic alpha-Agonists↗
PubMed1995

Regulation of norepinephrine release by beta 2-adrenergic receptors during halothane anesthesia.

BACKGROUND: Presynaptic receptors control norepinephrine (NE) release. It has been hypothesized that epinephrine stimulates prejunctional beta 2-adrenergic receptors to facilitate NE release from sympathetic nerve endings, and therefore, presynaptic receptors controlling NE release are potential therapeutic targets to limit the adverse effects of excess sympathetic stimulation during anesthesia. We have previously demonstrated beta 2-adrenergic receptor-augmented release of NE in the human forearm and have shown that halothane inhibits sympathetic activity in vivo by decreasing the NE spillover rate into plasma. The goal of the current study was to determine the effect of halothane on beta 2-adrenergic receptor-augmented NE release in a canine hind-limb experimental model. METHODS: Seven female dogs were studied awake and during halothane anesthesia (1.0 minimum alveolar concentration). A trace dosage of [3H]NE (15 microCi over a 1-min period and 0.6 microCi/min thereafter) was infused into the femoral vein. Before and during femoral arterial administration of isoproterenol at two dosages (30 and 80 mg/min), hind-limb blood flow was measured by an ultrasonic flow probe and hind-limb NE spillover by an isotope dilutional technique. RESULTS: In awake dogs, isoproterenol significantly increased hind-limb blood flow and NE spillover into the hind limb. Halothane had no effect on baseline or isoproterenol-stimulated hind-limb blood flow (a postjunctional beta 2 effect) but significantly inhibited the isoproterenol-induced increase in hind-limb NE spillover (a prejunctional beta 2 effect). CONCLUSIONS: The isoproterenol-mediated increase in NE release is inhibited by halothane anesthesia, indicating that halothane inhibits prejunctional beta 2-adrenergic receptor regulation of NE release.

Anesthesia↗
PubMed1976

Relative hypoxemia during rhytidoplasty.

The results of blood gas analyses in 24 patients who had a rhytidoplasty under local anesthesia indicated that a moderate degree of hypoxemia can be elicited in these patients when they have had standard doses of the usual sedatives. While the acid-base abnormalities were generally corrected spontaneously, the extent of the hypoxemia can be aggravated further by the additional use of diazepam during the operation. Therefore, over-sedation of such a patient during the operation, without a secured airway, must be avoided. Additionally, we recommend deep breathing at frequent intervals, with or without supplemental oxygen through a high flow system.

Adult↗
PubMed1988

Nerve root infiltration in the diagnosis of radicular pain.

Clinical and standard radiographic evaluation of patients with lumbosacral radicular symptoms may, on occasion, fail to delineate a cause. This study retrospectively reviews 62 patients who had undergone nerve root infiltration (NRI) and assesses the accuracy and indications for this diagnostic study. Surgical exploration of patients with a Group 1 response (typical pain reproduced by needle placement and then relieved by NRI) confirmed local root pathology in all. Exclusive of patients with arachnoiditis, a Group 1 response showed 85% accuracy in identifying a single symptomatic root. A Group 2 response (typical pain reproduced by needle placement but not relieved by local anesthesia) indicated multiple root involvement. Patients with a Group 3 or Group 4 response (typical pain not reproduced by needle insertion, with or without relief of pain by local anesthesia) were seldom relieved of radicular pain. NRI was most useful in investigation of patients with radicular symptoms in whom other investigations were 1) normal, 2) showed multiple level involvement, or 3) were difficult to interpret because of previous surgery.

Back Pain↗
PubMed1977

Systemic and regional blood flow during epidural anesthesia with epinephrine in the Rhesus monkey.

Hemodynamic and regional blood flow measurements were made in five rhesus monkeys before and 10, 20, 40 and 80 min after induction of high epidural anesthesia (T1) with lidocaine (1%) containing 1:200,000 epinephrine. Following induction of epidural anesthesia with epinephrine, there were significant decreases in heart rate, mean arterial pressure, cardiac output and myocardial and renal blood flow. The percentage of cardiac output received by the brain was significanly increased following epidural anesthesia with epinephrine, thus evidencing autoregulation to maintain cerebral blood flow. Vascular resistance in the lower extremity was significantly decreased during anesthesia, indicating arteriolar dilatation. Also, during anesthesia, the lungs received a significantly increased proportion of the microspheres, suggesting an increased peripheral arteriovenous shunting of microspheres due to the arteriolar dilatation.

Adjuvants, Anesthesia↗
PubMed1982

Effects of halothane-nitrous oxide inhalation anesthesia and Inactin on overall renal and tubular function in Sprague-Dawley and Wistar rats.

Real function, plasma renin concentration (PRC) and prostaglandin (PG) excretion rate was studied in groups of Sprague-Dawley (SPRD) and Wistar (WIST) rats anesthetized with either Halothane-N2O or Inactin. Conscious rats were used as controls. A. In Halothane-N2O anesthesia inulin clearance (CIN) and absolute proximal reabsorption rate (APR) was moderately decreased (by about 20%), while renal plasma flow (RPF), urine flow and solute excretion remained unchanged as compared to conscious rats. There was a linear relationship between the reciprocal of the proximal occlusion time (OT) and CIN in Halothane anesthesia indicating that the proximal luminal diameter was constant and independent of CIN. B. Inactin anesthesia CIN was similarly reduced but APR was more depressed (by about 35%). RPF and solute excretion rate decreased only in SPRD rats, while urine flow was significantly reduced in both strains. 1/OT was invariant to changes in CIN indicating luminal diameter variations in proportion to CIN. Urinary PGE2-and PGF2 alpha excretion rates and PRC were moderately elevated in operated animals of both strains regardless of the anesthetics used. It is concluded that renal functional parameters in surgically prepared rats are more severely depressed by Inactin than by Halothane-N2O anesthesia. The gas anesthesia is equally well tolerated by both strains of rats.

Anesthesia, Inhalation↗
PubMed1988

Cardiac arrhythmias during arousal from hibernation in three species of rodents.

Cardiac activity was monitored during arousal from deep hibernation in three species of hibernators (Citellus tridecemlineatus, Marmota monax, and Mesocricetus auratus). Individuals of each species showed marked arrhythmias, and these were confined to a body temperature range of between 11 and 20 degrees C, measured orally or rectally. The arrhythmias consisted of intermittent periods of asystole and bradycardia and were sometimes marked by the appearance of premature ventricular contractions and elevated or depressed S-T segments. Surgical manipulation of euthermic M. monax, under pentobarbital sodium anesthesia, indicated that none of the arrhythmias observed was inducible by injections of cold saline into the vena cava.

Animals↗
PubMedDate not supplied

Cardiovascular effects of atropine sulfate preparations in vagotomized dogs under halothane anesthesia.

The cardiovascular effects of 3 preparations of atropine sulfate were studied acutely in open-chest, vagotomized dogs under endotracheal halothane anesthesia. Indices of myocardial performance (LVdp/dt/CPIP and maximum ascending aortic blood acceleration) showed insignificant changes when varying doses of IV atropine (0.04 mg/kg and 0.04 mg/kg) were given. However, mean ascending aortic pressure fell by 20 percent following the larger doses of 2 commercial preparations containing antibacterial preservatives, and only 9 percent following a "pure" (USP) atropine preparation. Calculated changes in systemic vascular resistance closely followed actual pressure values. These results indicate that atropine, even in large doses, causes little or no depression of ventricular function independently of its chronotropic action. However, atropine does cause a fall in blood pressure, seemingly due to peripheral vasodilation, particularly in commercial preparations containing preservatives.

Anesthesia, Endotracheal↗
PubMed1991

Treatment of periodontal defects with an absorbable membrane (polyglactin 910) with and without osseous grafting: case reports.

The purpose of these reports is to illustrate the possible use of polyglactin 910 as an absorbable membrane for periodontal healing. Eleven surgical sites in 10 patients are reported. Vicryl mesh was used on all sites, and osseous allograft material was used in 8 of these sites. Radiographic evaluation and sounding with anesthesia indicate improvement in the treated areas. Few adverse effects were seen at the treated sites. Therefore, polyglactin offers promise as a material for use in periodontal therapy, especially in deep infrabony pockets. Further controlled studies comparing polyglactin 910 and other resorbable materials as barrier membranes are needed to establish their safety and efficacy.

Adult↗
PubMed1987

Effect of clot removal at 24 hours on chronic vasospasm after SAH in the primate model.

The efficacy of complete clot removal 24 hours after subarachnoid hemorrhage (SAH) in the prevention of chronic cerebral vasospasm was evaluated in monkeys in a blind randomized controlled trial. Twenty-four monkeys were randomized to one of three groups to undergo sham-operation (sham-operated group), clot placement only (clot group), or clot placement and removal (clot-removal group). By means of standard microsurgical techniques, the major cerebral vessels bilaterally were dissected free of arachnoid. An autologous hematoma averaging 5 gm was placed around the vessels in the subarachnoid spaces in the clot and clot-removal groups. Saline solution was instilled in the subarachnoid spaces of the sham-operated group. All animals underwent reoperation 24 hours after the first procedure. In the clot-removal group, the hematoma was evacuated. In the sham-operated and clot groups, the incision was simply closed again after 3 hours of anesthesia. Indices monitored before and 7 days after SAH induction included neurological status, angiographic cerebral vessel caliber, and arterial blood pressure. All animals were evaluated with magnetic resonance imaging (MRI); representative animals were evaluated with computerized tomography (CT) brain scans. There were no neurological deficits in either the sham-operated or the clot-removal groups. One animal in the clot group developed a progressive delayed ischemic deficit on Day 5 after SAH. A second animal in this group died suddenly on Day 4 post-SAH. An autopsy revealed a recent infarct in the territory of the superior cerebellar artery. Clinical findings correlated with MRI and CT images. Significant vasospasm (25% to 100% reduction in vessel caliber) was present on Day 7 in 100% of the clot animals (p less than 0.01). There was no significant vasospasm (p greater than 0.05) on Day 7 in either the sham-operated or the clot-removal groups. A large volume of clot placed bilaterally resulted in a 25% incidence of delayed ischemic deficit. Evacuation of subarachnoid hematoma within 24 hours of SAH prevented the development of chronic vasospasm and delayed ischemic deficit in the primate model.

Animals↗
PubMed1975

[Peridural anesthesia in obstetrics (author's transl)].

In German speaking countries peridural anesthesia in obstetrics has been introduced 25 years ago by Anselmino. Because of the increase of operative delivery and the--however rare--serious complications in the mother the technique has been employed less and less. Now, with the introduction of the catheter technique, which renders lower doses of the anesthetic effective and with improved treatment of complications due to it, the technique has become safer for the mother. Anomalies of the position of the fetal head are not more common than in deliveries without peridural anesthesia. But the more frequent need for low forceps delivery remains, since the strain-reflex is abolished, although motorfunction of lower limbs and abdomen are intact. The safe use of peridural anesthesia requires a considerably increased personnel, since the doctor conducting the delivery is only rarely sufficiently qualified in anesthetics and even then should not have to take the responsibility for both delivery and anesthesia. Since we can consider the technique safe for the mother, its effect on the child is predominant interest. Examination of the acid-base metabolism in the fetal blood from the scalp and umbilical cord post-partum has shown favorable results. The effect of complete painlessness on respiration and blood-gases of the mother is of interest (Strasser, Huch, Huch). Further investigations of the effects on fetal heart frequency and its assessment in supine or constant lateral positioning and of the maternal circulation with modern cardiologic techniques have not yet been concluded. On their results will depend, at least in part, the indication for peridural anesthesia in pregnancies and deliveries at risk. Clinical observations and comparison with deliveries under general anesthesia indicate that catheter peridural anesthesia may be advantageous for the child with diabetes, EPH gestosis and prematurity.

Anesthesia, Epidural↗
PubMedDate not supplied

The use of local anesthetics in the treatment of chronic pain.

Local anesthetics are an important and effective tool in the treatment of patients with chronic pain syndromes. Orthopaedic nurses are in a pivotal position to assess potential problems and intervene where appropriate. This article addresses the pharmacology of local anesthesia, indications for nerve blocks with local anesthetics, and nursing management.

Anesthesia, Epidural↗
PubMed1988

In vivo nuclear magnetic resonance studies of hepatic methoxyflurane metabolism. II. A reevaluation of hepatic metabolic pathways.

Methoxyflurane (2,2-dichloro-1,1-difluoro-ethyl methyl ether) is believed to be metabolized via two convergent metabolic pathways. The relative flux through these two metabolic pathways has been investigated using a combination of in vivo surface coil NMR techniques and in vitro analyses of urinary metabolites. Analysis of the measured concentrations of inorganic fluoride, oxalate, and methoxydifluoroacetate in the urine of methoxyflurane-treated rats for 4 days after anesthesia indicates that the anesthetic is metabolized primarily via dechlorination to yield methoxydifluoroacetate. The methoxydifluoroacetate is largely excreted without further metabolism, although a small percentage of this metabolite is broken down to yield fluoride and oxalate, as determined by urine analysis of rats dosed with synthetic methoxydifluoroacetate. At early times after methoxyflurane exposure, the relative concentrations of methoxyflurane metabolites indicate that a significant fraction of the metabolic flux occurs via a different pathway, presumably demethylation, to yield dichloroacetate as an intermediate. Direct analysis of dichloroacetate in the urine using water-suppressed proton NMR indicates that the level of this metabolite is below the detection threshold of the method. Measurements made on the urine of rats dosed directly with dichloroacetate indicate that this compound is quickly metabolized, and dichloroacetate levels in urine are again found to be below the detection threshold. These results demonstrate the quantitative importance of the dechlorination pathway in the metabolism of methoxyflurane in rats.

Animals↗
PubMedDate not supplied

The role of regional nerve block anesthesia for carotid endarterectomy: an experimental comparison with previous series with the use of general anesthesia and barbiturates for cerebral protection.

A retrospective analysis was performed on a consecutive series of 60 cases divided into two groups given carotid endarterectomy (C.E.) for atherosclerotic disease. In the first group general anesthesia and barbiturate cerebral protection were employed; in group two, loco-regional anesthesia. Indications and risk factors were similar in the two groups; the surgical procedure was identical. The differences in the results are reported and factors contributing to cerebral protection or reduction in the risk of stroke are analyzed. The analysis indicates that loco-regional anesthesia for C.E. is a reliable method for detecting cerebral ischemia and guaranteeing cerebral protection by means of a temporary shunt when strictly necessary.

Anesthesia, General↗
PubMedDate not supplied

[Treatment of acute ischemia of the hand].

Among numerous non-traumatic vascular disorders of the hand, only embolism and arterial thrombosis present acute characteristics, exceptional cases of extensive and sudden venous thrombosis apart. These signs are neurological and indicate extreme clinical urgency. Paresis and anesthesia indicate direct arterial surgery, embolectomy, thrombectomy, reconstruction by grafting or prosthesis. When ischemia affects only part of the hand, anticoagulant and vasodilative treatment is often sufficient and upper thoracic sympathectomy is unnecessary.

Acute Disease↗
PubMed1979

Halothane anesthesia in calves.

Because of the calf's popularity as an experimental animal and its often noted sensitivity to anesthetics and anesthesia, the potency of halothane was studied in eight, young (x = 5.85 weeks), healthy, male Holstein-Friesian calves. The minimal alveolar halothane-O2 concentration (MAC) which just prevented calf movement in response to a tail clamp was 0.76 +/- SEM 0.03 vol% and is less than predictions based on studies in man. The addition of 50% N2O to inspired gases decreased the halothane MAC to 0.59 +/- 0.03%. In the absence of common modifying factors of anesthesia, halothane-O2 caused cardiopulmonary depression in these calves in proportion to anesthetic dose. Only two (total protein and albumin) of 17 selected blood clinical biochemical values were significantly (P less than 0.05) altered from base line within seven days of anesthesia, indicating insults to major organ systems did not occur.

Anesthesia, Inhalation↗
PubMed1980

Serum inorganic fluoride and renal function in dogs after methoxyflurane anesthesia, tetracycline treatment, and surgical manipulation.

Effects of 2 hours of methoxyflurane-induced anesthesia in 25 dogs were determined by serum inorganic fluoride, serum urea nitrogen, serum creatinine, water intake, urine excretion, and urine specific gravity measurements; arterial concentrations of the anesthetic were also determined. The dogs were allotted to 5 groups (PTM, CTM, PTML, CTML, ML) of 5 dogs in each group and were anesthetized (M, in group designations) for 2 hours. The dogs were injected with chemically pure tetracycline or commercial tetracycline (PT and CT, in group designations) before, on the day of, and after anesthesia. In 3 groups, laparotomy (L, in group designations) was done; group ML did not receive tetracycline but a laparotomy was performed. Serum inorganic fluoride increased (P less than 0.05) in all groups 24 hours after anesthesia when compared with the base-line values; the highest mean serum concentration was 81.1 +/- 7.91 mumol/L (group PTM) and the lowest was 32.7 +/- 4.53 mumol/L (group PTML). There was no difference (P greater than 0.05) seen in serum urea nitrogen concentrations between groups. Methoxyflurane and tetracycline treatment caused no difference (P greater than 0.05) on serum concentrations of inorganic fluoride and urea nitrogen. Serum creatinine concentrations differed (P less than 0.05) only for groups PTM, CTM, PTML, and CTML vs group ML. Water intake reached peak at 48 hours after anesthesia. Arterial concentrations of methoxyflurane determined at 60 and 120 minutes of anesthesia indicated no difference (P greater than 0.05) among groups. Neither clinical nor laboratory signs of severe kidney dysfunction were detected in any of the experimental dogs during a 5-day observation period after anesthesia.

Anesthesia, Inhalation↗