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A study of the in vitro clinical interaction between lidocaine and premedications using rat liver microsomes.

In this study, we have investigated the relationship between lidocaine metabolism and premedication, i.e., psychotropic and anti-anxiety agents (diazepam, midazolam), hypnotics (pentobarbital, thiamylal), depolarizing muscular relaxants (vecuronium, pancuronium and suxamethonium), an active anti-hypertensive (clonidine) and an H2 receptor antagonist (cimetidine) using rat hepatic microsomes in vitro. Lidocaine metabolism was noncompetitively inhibited by midazolam (Ki=29.0 microM). Thilamylal was a moderate competitive inhibitor of lidocaine metabolism (Ki=77.8 microM). Pentobarbital, diazepam and cimetidine weakly inhibited lidocaine metabolism formation in a concentration-dependent manner at high substrate concentrations. On the other hand, vecuronium, pancuronium, suxamethonium and clonidine did not inhibit lidocaine metabolism over the therapeutic range. These results show that the interaction between lidocaine and midazolam and thiamylal, catalyzed by a similar cytochrome P450, is of potential importance in toxicological and clinical studies.

Anesthetics, Local↗

Lorazepam premedication: lack of recall and relief of anxiety.

Premedication with lorazepam (4 mg), diazepam (10 mg), and a placebo was compared in a randomized, double-blind study of 95 adult surgical patients. Comparisons were made of recall of a memory card and events of the operative day, relief of anxiety, degree of somnolence, effects on blood pressure and heart rate, and incidence of side effects. Lorazepam produced a significant lack of recall (antegrade amnesia) compared to the other agents. Lorazepam produced a greater antianxiety effect than placebo and a greater degree of somnolence than diazepam or placebo. Since no adverse effects on blood pressure or heart rate occurred, lorazepam appears to show promise as a premedicant.

Adult↗

Acute intravenous premedication with nalbuphine.

In a randomized, double blind study of 75 adult surgical patients, nalbuphine (0.1 mg/kg), morphine (0.1 mg/kg), or a placebo were administered intravenously as premedication 12 to 16 minutes prior to induction of anesthesia. Comparison of the 3 groups showed: (1) patients receiving nalbuphine and morphine had a significant reduction of minute ventilation and a significantly greater incidence of immediate side effects than did patients receiving placebo injections; (2) patients receiving morphine required no medication for pain in the early postoperative period; and (3) patients receiving nalbulphine experienced less nausea and/or vomiting postoperatively than did those in the other 2 groups.

Cervix Uteri↗

Dexmedetomidine premedication for minor gynecologic surgery.

The effects of four different doses (0.167, 0.33, 0.67, and 1.0 microgram/kg) of dexmedetomidine, a novel alpha 2-adrenoceptor agonist, on anesthetic requirements, hemodynamics, and plasma catecholamine levels were investigated in a single-blind fashion in 20 healthy (ASA physical status I) women scheduled for uterine dilatation and curettage. The drug was administered intravenously 15 min before anesthesia induction with thiopental. Nitrous oxide/oxygen (70%/30%) was used for maintenance. Dexmedetomidine was well tolerated, and no serious drug-related subjective side effects or adverse events were observed. The most prominent subjective effects were tiredness and decreased salivation. The total amount of thiopental needed to perform uterine dilatation and curettage was decreased dose-dependently from 400 +/- 166 mg (mean +/- SD) after 0.167 microgram/kg of dexmedetomidine to 180 +/- 65 mg after 1.0 micrograms/kg of dexmedetomidine (P = 0.028). Blood pressure, heart rate, and plasma norepinephrine levels were reduced after dexmedetomidine. The optimal dose of dexmedetomidine for single-dose intravenous premedication studies in minor surgery appears to be in the range of 0.33-0.67 micrograms/kg.

Adrenergic alpha-Agonists↗

Is premedication with oral glycopyrrolate as effective as oral atropine in attenuating cardiovascular depression in infants receiving halothane for induction of anesthesia?

The authors conducted a double-blind study to compare premedication with oral glycopyrrolate and oral atropine in prevention of bradycardia and hypotension during induction of anesthesia with halothane-N2O in 90 outpatient infants and children aged 1-18 mo who were randomized into three groups to receive either an oral placebo, oral atropine (0.02 mg/kg), or oral glycopyrrolate (0.05 mg/kg) approximately 1 h before induction of anesthesia. Heart rate and mean arterial pressure were measured before drug administration, just before induction of anesthesia, and every minute until surgical stimulation occurred. Glycopyrrolate, at the dose used, was significantly less effective than atropine in attenuating bradycardia during induction; neither glycopyrrolate nor atropine altered the incidence or degree of hypotension. Antisialagogic activity and side effects were comparable, except for significantly more flushing with atropine.

Administration, Oral↗

Parental anxiety levels during pediatric induction with and without administration of premedication for general anesthesia.

This study measured parental anxiety before, during, and after elective dental procedures under general anesthesia using the Spielberger State-Trait Anxiety questionnaire. State anxiety started relatively high before the procedures, peaked immediately after induction using general anesthesia, and dropped during recovery to below the initial score. Parents, whose children were premedicated and fathers in general, had significantly higher anxiety immediately after induction. This study supports interventions to lower anxiety of the parents as well as that of children.

Anesthesia, Dental↗

Evaluation of epidural administration of morphine or morphine and bupivacaine for postoperative analgesia after premedication with an opioid analgesic and orthopedic surgery in dogs.

OBJECTIVE: To evaluate the analgesic efficacy of epidural administration of morphine or a morphine-bupivacaine combination administered before orthopedic surgery in dogs that received opioid premedication. DESIGN: Prospective, randomized, blinded, clinical study. ANIMALS: 36 healthy adult dogs that underwent elective orthopedic surgery on a pelvic limb. PROCEDURES: Each dog received 1 of 3 epidural treatments before surgery. Anesthetic and supportive care protocols were standardized. Dogs under going different surgical procedures were randomly allocated among the 3 treatment groups. Respiratory and cardiovascular variables, end-tidal isoflurane concentration, and requirements for rescue analgesia were monitored. Postsurgical analgesia was evaluated with a multiparametric pain scoring system and by determination of rescue analgesia requirements and cortisolemia. RESULTS: The morphine-bupivacaine combination was associated with lower values than morphine or a saline solution for intraoperative arterial blood pressure; minimum and maximum isoflurane requirements; and postoperative pain scores, rescue analgesia requirements, and plasma cortisol concentrations. Values obtained after administration of morphine alone were not significantly different from those obtained after administration of saline solution for most variables. CONCLUSIONS AND CLINICAL RELEVANCE: The preoperative epidurally administered morphine-bupivacaine combination induced better analgesia than morphine alone and should be considered for use in clinical patients. The degree of hemodynamic depression associated with the combination was considered acceptable for healthy patients undergoing elective surgery.

Analgesia, Epidural↗

Relationship between scores on developing cognitive abilities test and scores on medical college admissions test for nontraditional premedical students.

The relationship of students' performance on the Developing Cognitive Abilities Test (DCAT), a test of scholastic aptitude, and their subsequent performance on the Medical College Admission Test (MCAT) were examined for 122 nontraditional premedical students who participated in a medical educational preparatory program. A stepwise multiple regression analysis produced moderate, though significant multiple correlations among subscores on the two tests. While there were a few exceptions, for the most part all of the subscores on the Developing Cognitive Abilities Test made a significant contribution to the regression equation in the prediction of scores on MCAT subtests. Implications for the value of the Developing Cognitive Abilities Test as an admissions tool as well as providing direction for possible intervention are discussed.

Aptitude Tests↗

Effectiveness of career-development courses for nontraditional premedical students: improving professional identity.

The purposes of this study were to examine the effects of three career-development courses on the professional identities of participating students as measured by My Vocational Situation and to investigate the effect of gender on students' responses to the scale. A total of 64 students enrolled in a special premedical program took the scale as a pretest and again as a posttest after the completion of three career-development courses. Analysis yielded significant differences between pre- and posttest scores for the three subscales of Vocational Identity, Occupational Information, and Barriers. No significant gender differences were observed at pre- or posttest. Implications for further research designed to evaluate the effectiveness of intervention strategies in career development are discussed.

Adult↗

Some clinical effects of midazolam premedication in propofol-induced and isoflurane-maintained anaesthesia in dogs during ovariohysterectomy.

In a randomised, placebo-controlled clinical trial, anaesthesia was induced with propofol (4 mg/kg) after intravenous premedication with or without midazolam (0.1 mg/kg), in a group of 8 dogs scheduled for ovariohysterectomy. Midazolam administration induced acute behavioural changes, and increased reflex suppression after propofol induction. Compared to the control group, the dose required to obtain loss of the pedal reflex was significantly reduced by 37%, and the end-tidal isoflurane concentration during maintenance, reduced by 23%.

Adjuvants, Anesthesia↗

[Computation of mixed venous oxygen saturation in intracardial shunts and its dependence on age, anesthesia and premedication].

In patients with an intracardiac shunt, the oxygen saturation of the mixed venous blood cannot be measured, but it must be estimated from the oxygen saturation in the superior and in the inferior vena cava. We have evaluated the results of patients who had definitively no shunt and who had been catheterized for other reasons. Based on statistical principles we developed formulas to calculate the oxygen saturation of the mixed venous blood. We examined three group of patients: a) Children up to 11 years catheterized during general anaesthesia (58 patients) b) Children up to 11 years catheterized after premedication but without general anaesthesia (53 patients) c) Adults catheterized without general anaesthsia (59 patients) We found that the formulas from the patients who had been catheterized during general anaesthesia were quite different from those without anaesthesia. In the patients without an anaesthesia the superior vena cava was coupled with a much higher factor than the inferior vena cava; in patients with anaesthesia, the contribution of the inferior vena cava was stronger. The age of the patients had no significant influence on our formulas.

Adolescent↗

[Condition of patients after surgical wisdom tooth extraction under general anesthesia with different premedication variants--a prospective study based on a post-anesthesia questionnaire].

Evaluation of the modified "postanaesthesiological questionnaire" pointed to a subtle influencing of the condition of patients who had undergone 3rd molar surgery in general anaesthesia by using different premedication variants: "Atropine, Pethidine and Midazolam" (group A) and "Atropine, Midazolam and S-Ketamin" (group B). The combination in group B seems to be more suitable. On the one hand, a lower incidence of unwanted side-effects was found and, on the other hand, remarkable positive effects were observed. Of particular significance with this combination was also the more effective suppression of postoperative pain. The Propofol-supplemented general anaesthesia prepared in this way and administered using a nasal intubation technique found the full approval of the patients. Postoperative pain therapy was effective and also inexpensive, costing just 8.20 DM per patient, according to current prices calculated by Magdeburg University Hospital.

Adult↗

[Preparation, premedication and parental presence].

40% to 60% of children undergoing surgery under general anaesthesia develop anxiety in the preoperative period. Multiple factors contribute to the genesis of this disorder. Preoperative anxiety may complicate the induction of anaesthesia and can cause behavioural modifications in children even long after surgical procedures have been completed. It is important to focus on prevention of such problems. A preparation program, premedication and parental presence during induction of anaesthesia are valid tools for achieving this goal. We are herewith presenting a play preparation program carried out by play specialists and offered to all children prior to surgery. This approach proved effective in reducing preoperative anxiety in children and their mothers.

Age Factors↗

[Preoperative fasting regimens and premedication to reduce the risk of pulmonary aspiration].

Our greater understanding of gastric physiology and the epidemiology of Mendelson's syndrome has allowed the traditional guidelines for preoperative fasting (nothing by mouth after midnight or 6 hours before surgery) to be changed, based on the results of many scientific studies. The stomach is not emptied of liquids and solids in the same way, and therefore preoperative fasting should not be the same for both. Human milk leaves the stomach more rapidly than infant formulas, and the emptying of non-human milk is similar to that of solids. Fasting does not guarantee that the stomach will be empty or that the pH of gastric juices will be high; moreover, shortening the preoperative fasting period may bring several advantages for the patient. Factors such as premedication, anxiety, age, certain associated diseases or injuries may or may not influence gastric emptying and/or acidity at the time of anesthesia. We review the literature, including the guidelines on fasting of the American Society of Anesthesiologists for application with healthy patients of all ages in elective procedures, excluding, among others, women in childbirth and patients undergoing emergency surgery.

Adult↗

The value of premedication in diminishing salivary secretions.

A study has been carried out on the anti-sialogogue effect of some drugs used in premedication. Among different anaesthetic agents used in this study halothane appeared to be the least effective in stimulating salivary secretions. Pethidine-atropine combination proved to be very satisfactory as an anti-sialogogue. Atropine came next, where its intravenous route of administration was more satisfactory in short procedures than its intramuscular route.

Adolescent↗

[Utility of premedication with different regimens of omeprazole and ranitidine in the prevention of acid broncho-aspiration syndrome].

OBJECTIVE: To study the usefulness of several omeprazole regimens on gastric fluid volume and pH in patients undergoing elective surgery. MATERIAL AND METHODS: We analyzed 105 patients undergoing to elective surgery who received prophylactic treatment for the acid aspiration syndrome. They were randomly allocated into 7 homogeneous groups according to the therapeutic regime. Placebo (group 1), oral omeprazole (20 mg) the night prior to surgery (group 2), oral ranitidine (150 mg) the night before (group 6), two doses (the previous night and before surgery) in the remaining three groups: 20 mg of omeprazole (group 4), 40 mg of omeprazole (group 5) or 150 mg of ranitidine (group 7). In all patients we measured pH and volume of the gastric content after induction of anesthesia and one hour thereafter. RESULTS: There were no statistically significant differences in mean pH values and gastric volume content among groups 1.2,3, and 6 (2.1 (pH) and 27 ml (gastric volume) in group 1, 2.1 and 23 ml in group 2, 2.6 and 19 ml in group 3, and 2.2 and 32 ml in group 6). With repeated doses of 40 mg omeprazol (group 5), mean pH values were comparable to those found with the two doses of ranitidine (4.1 +/- 1.8 vs 4.1 +/- 3.6) although gastric volumes were significantly less (12 +/- 2.6 ml vs 20 +/- 4.8 ml). These two groups showed significantly greater mean pH values and less gastric volumes than the remaining patients. CONCLUSIONS: The incidence of patients with gastric content deemed at risk for acid aspiration (pH less than 2.5 and gastric volume greater than 25 ml) was less after premedication with two oral doses of omeprazole (40 mg) than either two doses of ranitidine (150 mg) or smaller doses of both drugs.

Adult↗

Serum potassium after enflurane-succinylcholine induction of anesthesia in children receiving rectal midazolam as premedication.

The administration of succinylcholine causes an increase in serum potassium (K+) concentrations in healthy patients. The purpose of this study was to investigate serum K+ changes following intravenous succinylcholine in children and to evaluate the effect of rectal midazolam pretreatment on these changes. Forty healthy children between the ages of 2 and 7 yr, and who were to undergo oral surgical procedures under general anesthesia were randomly assigned to receive either placebo (saline) or 0.25, 0.35, or 0.45 mg/kg midazolam administered rectally as premedication 30 min before induction of inhalational anesthesia. Blood was drawn after induction with enflurane and at 1, 2, 3, 4, and 5 min after administration of 1 mg/kg succinylcholine to determine changes in serum K+. Although the results indicate a significant increase in serum K+ after succinylcholine in all groups, midazolam pretreatment failed to cause any observable attenuation in the hyperkalemic response.

Administration, Rectal↗

[Histamine release during induction of combination anesthesia using nalbuphine or fentanyl. Modulation of the reaction by premedication with promethazine/pethidine].

In a controlled clinical trial in patients admitted for general surgery (mainly abdominal and thyroid), histamine release following nalbuphine 1 mg/kg i.v. versus fentanyl 5 micrograms/kg i.v. was studied in the course of an otherwise routine induction with promethazine/pethidine as premedication 30 min before the opioids and alcuronium-flunitrazepam-thiopental 5 min later. Succinylcholine was given before intubation and further analgesia was obtained by repeated administration of either nalbuphine or fentanyl. Plasma histamine levels were measured by a specific fluorometric assay, heart rate and blood pressure were measured for assessing hemodynamics, and clinical signs of anaphylactoid reactions such as skin eruptions and arrhythmias were registered. RESULTS. Nalbuphine and fentanyl both released histamine with an incidence of more than 40%. In addition, nalbuphine potentiated the histamine release evoked by the sequential administration of alcuronium-flunitrazepam-thiopental in one complex of application. The incidence of histamine release in the nalbuphine group was 6/13 = 46%, in the fentanyl group only 1/11 = 9% (chi2 test, P less than 0.05). Furthermore, this study showed high histamine levels after succinylcholine and intubation in a relation to time of administration that suggested histamine release as a stress response to intubation. Finally, the incidence of histamine release after a second injection of the opioids was still 30%. A direct correlation between plasma histamine levels, hemodynamic changes, and skin reactions could not be shown. A detailed causality analysis with histamine release as a contributory determinant showed histamine release less detrimental to hemodynamic stability than the opposite, which had been expected. However, the promethazine administered 30 min before induction of anaesthesia had strong H1- and H2-receptor antagonistic activity and was given with optimum timing for H1- and H2-prophylaxis. CONCLUSION. The study demonstrated that histamine release during anaesthesia and surgery depends strongly on the time sequence of drugs and measures used. Histamine release is not predictable from studies in human volunteers alone; studies in patients have to be added. Histamine release is not always detrimental. H3-receptor-mediated effects after H1- and H2-prophylaxis may help patients to counteract the effects of a series of vasoactive drugs given during induction of anaesthesia.

Adult↗