Mixture Of Propofol Research Articles

Antibacterial activity of remifentanil and mixtures of remifentanil and propofol

Study Objective To investigate the antibacterial activity of glycine, which is contained in remifentanil, when combined with propofol. Design Prospective study. Setting Departments of anesthesiology and microbiology of a university hospital. Measurements Growth of the microorganisms Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans in propofol 1%; saline dilutions of remifentanil at one-, 10-, and 100- μg/mL concentrations; and 1:1 mixtures of propofol with remifentanil solutions was determined. Main Results Remifentanil inhibits bacterial growth in a concentration-dependent manner. The antibacterial effects were more pronounced with Staphylococcus aureus and Pseudomonas aeruginosa at cultures obtained at the fifth hour. The inhibition of bacterial growth was less influenced with Escherichia coli and Candida albicans. Conclusions Propofol and remifentanil mixtures decreased bacterial growth, and combinations may reduce the infectious complications from accidentally contaminated propofol.

Anesthesia in xylazine premedicated donkeys with ketamine and ketamine-propofol mixture: A comparative study

This study was conducted to evaluate the anesthetic quality produced by ketamine hydrochloride (K) (3 mg/kg, I.V.) and ketamine–propofol (K-P) mixture (2 mg/kg-1 mg/kg, I.V., respectively) in six donkeys premedicated with xylazine (X), (1 mg/kg, I.V.). Each donkey was anesthetized one time with each dose of (K) and (K-P), five minutes after (X) administration, in random order at (1) week intervals. The anesthetic parameters; induction and sleeping time, abolishment of the swallowing reflex, recumbencey period, cardiopulmonary responses, were qualitatively and quantitatively assessed. The results revealed presence of significant difference (p< 0.05) in the induction and sleeping time between (K) and (K-P) protocols. Neither the swallowing reflex, nor recumbency period represented statistical difference between (K) and (K-P) protocols. But clinically, anesthesia with (K-P) produced shorter and smoother recovery to recumbency than with (K), and the swallowing reflex was abolished while persisted with (K) anesthesia. The excellent anesthesia produced with K-P was characterized by smooth, calm, gradual and free of excitement induction (23.75±1.75 sec), good narcosis (22.50±3.57 minutes) and muscle relaxation. The swallowing reflex was abolished for (15.75±5.61 minutes). The recumbency period was characteristically smooth and featured by its rapidness (10.50±2.62 minutes). While on the other hand, induction of anesthesia with (K) protocol was characterized by rough, slow and excitement (56.25±8.44 sec), muscle rigidity, and persistence of the swallowing reflex (not disappeared or slightly disappeared). The shorter sleeping time (10.5±0.95 minutes) and the longer recumbencey (14.75±2.28 minutes) periods that was associated with violent convulsion and excitement, were clinically an obvious associate with (K) anesthesia. The intubations with (K-P) anesthetic protocol was easily performed, but was difficult or failed during (K) anesthesia.In conclusion, anesthesia with (K-P) protocol produced an excellent anesthetic mixture for induction of general anesthesia in donkeys, and up to our knowledge this the first report on the use of this mixture for total intravenous anesthesia in donkeys.

Use of a variable-stiffness colonoscope decreases the dose of patient-controlled sedation during colonoscopy: a randomized comparison of 3 colonoscopes

The variable-stiffness colonoscope incorporates different degrees of stiffness of the insertion tube, which can be adjusted during the examination. Whether its use can lead to reduced procedure-related pain and sedative use is unknown. Our purpose was to compare the use of 3 types of colonoscope with different shaft stiffnesses in relation to procedure-related pain and sedative consumption. Prospective randomized trial. Endoscopy unit of a university-affiliated hospital. Consecutive patients undergoing ambulatory colonoscopy. Random assignment was made of patients into 3 groups to receive colonoscopic examinations by one of the 3 types of colonoscope: conventional standard adult size, 1.3-m; 1.6-m; and the new variable-stiffness adult size, full-length (1.6-m) colonoscope. A mixture of propofol and afentanil, delivered by a patient-controlled syringe pump, was used for sedation in all groups. Outcome measures included dose of patient-controlled sedation consumed, pain score, cecal intubation rate, cecal intubation time, requirement of abdominal pressure and change of patients' positions during colonoscopy, and endoscopists and patients' satisfaction scores according to a visual analog scale. A total of 335 patients were randomized. Patients in group 3 used significantly less propofol (in milligrams per kilograms, mean [SD]) compared with the other 2 groups (group 1: 1.00 [0.75], group 2: 0.93 [0.62], and group 3: 0.75 [0.65]; P = .02; 1-way analysis of variance). The mean (SD) pain score was also lower in group 3. The endoscopists were not blinded. The use of the new variable-stiffness adult-size colonoscope significantly reduced procedure-related pain and doses of sedative medications during colonoscopy.

Reduction of pain on injection of propofol: combination of pretreatment of remifentanil and premixture of lidocaine with propofol

There is a high incidence of pain following intravenous injection of propofol, and many studies have been conducted to find a way of reducing this. The administration of lidocaine and, recently, remifentanil has also been used for this purpose, but it is only partially effective. Thus, the purpose of this study was to investigate the analgesic effect of a combination of pretreatment with remifentanil and premixture of lidocaine with propofol and to compare either treatment alone during propofol injection in dorsal hand-veins. In a prospective, randomized, double-blinded trial, we studied 141 adult patients scheduled for elective surgery. The combination of pretreatment of remifentanil (0.35 microg kg(-1) min(-1)) and a premixture of lidocaine with propofol (mixture of propofol 1% and lidocaine 1% in a 10:1 ratio) was compared with either treatment alone in the prevention of pain on propofol injection. Pain was assessed on a four-point scale (0=none, 1=mild, 2=moderate, 3=severe) during propofol injection. Patients in Group B received remifentanil (0.35 microg kg(-1) min(-1)) 30 s before the injection of propofol. The reduction of pain on propofol injection was similar in both the remifentanil pretreatment and lidocaine premixture groups (62.2% vs. 62.2%). Combination therapy was associated with a higher incidence of patients without pain (91.3%) than either treatment alone (P<0.001). On analysing the injection pain scores, we found a significant reduction of the score in the remifentanil and lidocaine Group C compared with the lidocaine Group A (P<0.001) and the remifentanil Group B (P<0.001). The combination of pretreatment of remifentanil and premixture of lidocaine with propofol was more effective in reducing the incidence of pain on injection of propofol than either treatment alone.

A novel mixture of propofol, alfentanil, and lidocaine for regional block with monitored anesthesia care in ophthalmic surgery

Study Objective The purpose of this study is to determine the efficacy and safety of sedation/analgesia using a mixture of propofol, alfentanil, and lidocaine. Design A retrospective case review was undertaken. Setting This study took place at a university medical center. Patients Eighty-nine American Society of Anesthesiologists physical status 1, 2, and 3 adult patients undergoing ophthalmic surgery with regional block and monitored anesthesia care were studied. Intervention Six milliliters of propofol, 2 mL of alfentanil, and 2 mL of 2% lidocaine (6-2-2 mixture) were freshly mixed. The bolus dose was determined based on the patients' age: 5 μg/kg of alfentanil (and 0.3 mg/kg of propofol) for patients older than 75 years; the dose increased 1 μg/kg per 10-year decrease in age; and up to 9 μg/kg of alfentanil (0.54 mg/kg of propofol) for patients younger than 45 years. Regional block was performed at 1 minute after bolus completion. Blood pressure (BP), Sa o 2 , electrocardiogram, capnography, clinical signs of sedation, responses to block, need for airway support, nausea and vomiting (N/V), pain due to propofol infusion, recall, and patient and surgeon satisfaction were recorded. Measurements and Main results Seventy-eight percent of patients achieved analgesia and sedation without adverse response to the block. Twelve percent achieved good analgesia and sedation with only eyebrow movement upon needle insertion. Twenty-seven percent had respiratory depression but were able to follow commands and maintain adequate ventilation. Two percent had brief apnea alleviated by chin lift or jaw thrust. None had pain because of propofol infusion or N/V. Before sedation, average systolic BP was significantly increased ( P < 0.0001) compared with baseline. After sedation and block, systolic BP decreased 6% from baseline ( P < 0.005). Conclusion Adjusted for age and weight, the dose of the 6-2-2 mixture met the sedation requirements for most patients. With a low incidence of need for airway support, no pain during infusion, and no N/V, this novel mixture of propofol, alfentanil, and lidocaine provided adequate analgesia and sedation as well as hemodynamic stability for ophthalmic surgery under regional block.

Inhibition of bacterial growth by different mixtures of propofol and thiopentone

Propofol is, as a result of its formulation, an ideal bacterial and yeast culture medium. An outbreak of sepsis in humans and an increase in wound infections in dogs has been ascribed to the use of propofol. It has been previously reported that a 1:1 mixture of propofol and thiopentone has bactericidal properties. This study was undertaken to determine if further serial mixtures of propofol and thiopentone maintained the bactericidal properties. Mixtures of 1:1 (solution A), 5:1 (solution B), 10:1 (solution C), 50:1 (solution D) and 100:1 (solution E) of 1% propofol to 2.5 % thiopentone, 2.5% thiopentone (solution T), 1% propofol (solution P) and saline (solution S) were prepared and inoculated with between 10(5) and 10(6) colony-forming units of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. A sample was withdrawn from each solution at 0, 1, 6, 12, 48 and 120 hours after inoculation and a bacterial count was performed. This study showed that thiopentone and solution A behaved in similar fashion by inhibiting bacterial growth and was bactericidal after 48 hours. Solution B was not bactericidal against S. aureus and C. albicans. Propofol and solutions D and E all supported growth of all the organisms tested. These data indicate that mixtures of propofol and thiopentone at a ratio less than 1:1 do not maintain the bactericidal properties.

Propofol-ketamine mixture for anesthesia in pediatric patients undergoing cardiac catheterization

Objective To evaluate the safety of a propofol-ketamine mixture to induce and maintain anesthesia in spontaneously breathing pediatric patents during cardiac catheterization. Design Prospective clinical study. Setting Departments of Cardiothoracic Surgery, Anesthesiology, and Pediatric Anesthesiology in a university hospital. Participants Forty-five children aged 6 months to 16 years with ASA grade II to III undergoing cardiac catheterization. Interventions Continuous intravenous infusion of a mixture of propofol (4 mg/mL) and ketamine (2 mg/mL) with spontaneous ventilation. The infusion rate was changed and additional boluses of propofol or/and ketamine were given as needed. Hemodynamic, respiratory, and other variables were recorded during the procedure and recovery. Results Mean dose of ketamine was 26 ± 8.3 μg/kg/min and of propofol, 68.3 ± 21.7 μg/kg/min. Changes in heart rate and mean arterial pressure of more than 20% from baseline were observed in 4 and 5 patients, respectively. A transient reduction in oxygen saturation because of hypoventilation was observed in 3 patients and responded to oxygen administration and manual assisted ventilation. No other complications were observed. Conclusions The propofol-ketamine mixture is a safe, practical alternative for general anesthesia in pediatric patients undergoing cardiac catheterization.

Pretreatment with intravenous ketamine reduces propofol injection pain

Paediatric procedural sedation using propofol has been shown to be safe and effective and is widely used. Pain at the injection site is a frequent complaint and can be particularly distressing for children, especially for those undergoing repeated procedures. Ketamine has analgesic properties and can diminish the incidence of propofol infusion pain in adults. The aim of the study was to investigate whether pretreatment with ketamine would reduce infusion line pain in propofol sedation in children. We performed a prospective, randomized, double-blind trial in a paediatric sedation unit of a tertiary referral teaching hospital. A total of 122 children admitted for gastroscopy were randomly allocated into two groups. Group 1 received atropine and ketamine before propofol infusion. Group 2 received atropine, normal saline solution, and a mixture of propofol with lidocaine. The main outcome measure evaluated was pain associated with the infusion and secondary outcome measures were mean medium arterial pressure decrease and desaturation. The incidence of pain of the infusion was significantly lower in patients pretreated with ketamine (8% vs 37%, P = 0.0001). Pretreatment with ketamine (0.5 mg.kg-1) is very effective in preventing propofol infusion pain.

Growth of microorganisms in propofol and methohexital mixtures

Purpose: The purpose of this study was to evaluate the growth of 4 different microorganisms in propofol, methohexital, and 1:1 and 1:3 mixtures of propofol and methohexital. Materials and Methods: The microbial growth of Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and Escherichia coli in 1:1 and 3:1 mixtures of methohexital and 2 types of propofol was measured for 48 hours after mixing the solutions. Two of the 4 test solutions were composed of 1% methohexital combined with Diprivan (AstraZeneca Pharmaceuticals, Wilmington, DE), which uses EDTA as a microbial growth inhibitor. The growth of the same 4 microorganisms was also evaluated in 1:1 and 3:1 mixtures of 1% methohexital and a recently introduced generic propofol marketed by Baxter Pharmaceuticals (Deerfield, IL) that uses sodium metabisulfite as a preservative. Results: Combining either Diprivan or generic propofol with methohexital in a 1:1 or 1:3 mixture ratio resulted in a solution that, like methohexital alone, significantly resisted the growth of C albicans, E coli, S aureus, and P aeruginosa for 48 hours. Conclusion: The results of our study suggest that 1:1 and 1:3 mixtures of propofol (either Diprivan or generic propofol) and methohexital behave similarly to methohexital alone by resisting growth of the microorganisms studied over the 48-hour time period. If, as has been reported elsewhere, the mixture of these 2 agents results in a solution with desirable anesthetic properties, its ability to resist microbial growth becomes clinically significant by extending the shelf-life of propofol in these mixtures.

Echocardiographic evaluation of dogs receiving 1:1 thiopental/propofol in a clinical setting

The purpose of this study was to compare the echocardiographic Doppler blood pressure and heart rate effects of 1:1 thiopental/propofol with thiopental and propofol, when used as anesthesia-induction agents. Seven healthy dogs (six Beagles and one Pembroke Welsh Corgi), ranging in age from 1 to 9 years and weighing 14.2 ± 2.4 kg (mean ± SD), were used during the study. In a cross-over study design with a minimum drug interval of 3 days, each dog received propofol, thiopental, or a mixture of propofol–thiopental IV until each dog received all the three anesthetic agents. An initial dose (propofol 4.9 ± 0.8 mg kg−1; thiopental 12.9 ± 2.4 mg kg−1; propofol–thiopental 2.3 ± 0.3 mg kg−1 (P)−5.7 ± 0.8 mg kg−1 (T)) of each anesthetic agent was titrated IV until intubation was accomplished. Echocardiographic Doppler blood pressure and heart rate variables were recorded prior to anesthesia and at 1, 5, and 10 minutes after induction of anesthesia. anova and the Bonferroni's t-test were used to evaluate the groups for differences. Alpha was <0.05. There was no significant effect of treatment on systolic or diastolic ventricular wall thickness, septal thickness, left atrial diameter, or systolic left ventricular diameter. There was a tendency for diastolic left ventricular diameter to decrease over time. There was a tendency for heart rate to increase with a significant difference at the 10-minute time period between propofol (109 ± 26 beats minute−1) and thiopental (129 ± 23 beats minute−1). At the 10-minute recording period, heart rate following the propofol/thiopental mixture (110 ± 34 beats minute−1) was closer to that following propofol than to that following thiopental. With all induction agents, indirect blood pressure tended to decrease over time (p = 0.005); however, there was no difference between the groups. The changes observed were not considered to be of clinical significance. The propofol/thiopental mixture produces similar changes in echocardiographic variables when compared to propofol or thiopental, and could be substituted for propofol for induction of anesthesia in dogs.

Nitrous oxide/oxygen mixture and the prevention of pain during injection of propofol

Background and objective: The incidence of pain associated with the injection of propofol still remains a problem. This study sought to examine the analgesic effects of inhaled nitrous oxide in oxygen on the prevention of propofol injection pain. Methods: Nitrous oxide in oxygen was compared with a lidocaine (20 mg)-propofol mixture and with propofol alone (control) in a prospective, randomized, observer-blinded study. ASA I and II patients (n = 135) scheduled for elective surgical procedures were studied. A standard propofol injection technique and scoring system to measure the pain on injection was used. Results: Demographic variables were similar between the study groups. Without analgesia (control) 26 of 45 patients (58%) reported pain on injection compared with 11 of 45 patients (24%) in both the nitrous oxide (95% CI: 14-52%, P = 0.001) and lidocaine groups (95% CI: 14-52%, P = 0.001). Conclusions: The inhalation of a nitrous oxide/oxygen mixture significantly reduces the incidence of pain during propofol injection. This therapeutic stratagem was as effective as a lidocaine-propofol mixture.

Patient-Controlled Sedation for Outpatient Thermal Balloon Endometrial Ablation

Study Objective To evaluate the effectiveness, safety, and patient satisfaction with patient-controlled sedation during thermal balloon endometrial ablation. Design Prospective observational study (Canadian Task Force classification II-2). Setting University-affiliated teaching hospital. Patients Thirty consecutive women with idiopathic menorrhagia refractory to medical treatment. Intervention Thermal balloon endometrial ablation under patient-controlled sedation with a mixture of propofol and alfentanil through an analgesia pump. Measurements and Main Results Pain was assessed using a descriptive pain score and the procedure was divided into four stages for assessment: catheter insertion, preheating phase, treatment cycle, and end of treatment. Patient satisfaction was assessed using the 8-item client satisfaction questionnaire. The procedure was well tolerated with good cooperation and no oversedation. Preheating was the most painful, and pain could be alleviated by asking the patient to self-administer a bolus of anesthesia before that phase. The median consumption of propofol was 35 mg (range 0–70 mg) and of alfentanil was 175 mg (range 50–200 μg). There were no intraoperative complications and the overall success rate in treating menorrhagia was 87%. Over 85% of the women did not think that general anesthesia was necessary. They all were highly satisfied and would recommend the procedure to others. Conclusion Patient-controlled sedation is a safe and effective method of alleviating pain and discomfort during thermal balloon ablation and is well accepted by patients.

Patient-controlled sedation versus intravenous sedation for colonoscopy in elderly patients: A prospective randomized controlled trial

Background: A prospective randomized trial was conducted to compare the safety, effectiveness, and patient acceptance of patient-controlled sedation and intravenous sedation for colonoscopy in a group of elderly patients undergoing outpatient colonoscopy. Methods: One hundred patients over 65 years of age were recruited and randomized to patient-controlled sedation (n = 50) or intravenous sedation (n = 50) groups by means of computer-generated numbers. In the patient-controlled sedation group, a mixture of propofol and alfentanil was delivered by means of a patient-controlled pump; each bolus delivered 4.8 mg propofol and 12 μg alfentanil. No loading dose was used and the lockout time was set at zero. In the intravenous sedation group, fixed doses of diazemuls (0.1 mg/kg) and meperidine (0.5 mg/kg) were given with further increases in dosages administered at the discretion of the endoscopist. Outcome measures assessed included cardiopulmonary complications, recovery time, pain score, and satisfaction score. Results: The mean (SD) age of patients in the patient-controlled sedation and intravenous sedation groups were, respectively, 72.4 years (5.3) and 73.5 years (6.1). The mean dose of propofol consumed in the patient-controlled sedation group was 0.79 (0.46) mg/kg. The mean doses of diazemuls and meperidine consumed in intravenous sedation group were, respectively, 5.8 (1.3) mg and 30.1 (6.8) mg. Hypotension occurred in 2 (4%) patients in the patient-controlled sedation group and 14 (28%) in the intravenous sedation group ( p < 0.01). Oxygen desaturation was recorded for 4 patients (8%) in the intravenous sedation group. The median (interquartile range [IQR]) recovery time was significantly shorter in the patient-controlled sedation group compared with the intravenous sedation group (respectively, 0 minutes [IQR 0-5] vs. 5 minutes [IQR 5-10]; p < 0.01). There were no statistically significant differences between groups for pain and satisfaction scores. Conclusions: Patient-controlled sedation appears to be safer than intravenous sedation, with comparable effectiveness and acceptance, in elderly patients undergoing elective outpatient colonoscopy. (Gastrointest Endosc 2002;56:629-32.)

Prévention de la douleur à l’injection du propofol chez l’enfant : comparaison de l’inhalation de protoxyde d’azote à l’injection de lidocaïne

Introduction: Injection pain caused by propofol is an important disadvantage, especially in children, incompletely reduced by adding lidocaine intravenously. Nitrous oxide’s analgesic effects, well known, have never been evaluated on pain due to propofol. Objective: To compare the effects of nitrous oxide with lidocaine on pain on injection caused by propofol in children. Study design: Double blind, randomised, prospective study. Patients and methods: 48 children aged more than 5 were randomly allocated to one of the 2 groups: N 2O group, breathed 50 %N 2O + 50 %O 2 than received propofol only and Lido group breathed 100% O 2 and received a mixture of propofol with lidocaine. The possible pain was scored during injection by a behavioural scale and once again in the recovery room by the child himself with a VAS. Results: There was no significant difference in behavioural pain scores among the 2 groups; pain was assessed as being moderate or severe in 6/24 patients in N 2O group and 10/24 in Lido group (behavioural scores > 1). Significantly more children in the N 2O group had low VAS scores compared with the Lido group (no child/24 scored a VAS > 4 and 7/23 in the Lido group) demonstrating that N 2O amnesic effects would omit the memory of pain caused by propofol. Conclusion: The use of nitrous oxide is an easy, cheap and efficient method to reduce the incidence of pain injection of propofol and his amnesic effects can provide real advantages in paediatric anaesthesia.

Relaxation music decreases the dose of patient-controlled sedation during colonoscopy: A prospective randomized controlled trial

Background: A prospective randomized controlled trial was performed to test the hypotheses that music decreases the dose of sedative medication required for colonoscopy and that the combination of music and patient-controlled sedation improves patient acceptance of colonoscopy. Methods: One hundred sixty-five patients scheduled to undergo elective colonoscopy were randomized to receive 1 of 3 different modes of sedation: Group 1, a combination of music and patient-controlled sedation with a mixture of propofol and alfentanil; Group 2, patient-controlled sedation alone; Group 3, music alone with diazemuls and meperidine administered intravenously if requested by the patient. Each bolus of patient-controlled sedation delivered 4.8 mg propofol and 12 μg alfentenil. Music was provided by means of a portable compact disc machine with headphones. Outcome measures assessed immediately after colonoscopy and 24 hours later included dose of patient-controlled sedation used, complications, recovery time, pain score, satisfaction score, and willingness to repeat the procedure with the same mode of sedation. Results: The mean (SD) dose of propofol used in Group 1 was significantly less than Group 2 (0.84 mg/kg [0.69 mg/kg] vs. 1.15 mg/kg [0.83 mg/kg]; p = 0.02, t test). The mean (SD) satisfaction score was higher in Group 1 (7.8 [2.1]) compared with Group 2 (6.8 [2.3]) and Group 3 (7.4 [2.3]) (p = 0.05, 1-way analysis of variance). The majority of patients in Group 1 were willing to repeat the same mode of sedation when queried immediately after colonoscopy (87%) and 24 hours later (75%), which was significantly different from the corresponding results in the other 2 groups; p = 0.04 and p < 0.01 respectively, chi-square test. Conclusions: Music can decrease the dose of sedative medication required for colonoscopy. The combination of music and patient-controlled sedation was the best-accepted mode of sedation among 3 groups. (Gastrointest Endosc 2002;55:33-6.)

Clinical Evaluation of Total Intravenous Anesthesia Using a 3-in-1 Mixture of Propofol, Alfentanil and Atracurium

Background: The use of 3 syringe pumps for one patient has disadvantages. To avoid errors and confusion associated with 3 separate infusions, we conducted a feasibility study of total intravenous anesthesia (TIVA) using a 1 syringe pump to deliver a 3-in-1 mixture containing fixed proportions of propofol, alfentanil and atracurium. Methods: The 3-in-1 mixture was obtained by mixing 400 mg propofol, 2.5 mg alfentanil, 40 mg atracurium, and totally 80 ml with a 5% dextrose solution. Light microscopy was used to compare emulsion instability of the 3-in-1 with a control mixture. In 40 ASA physical status 1 patients, bolus infusions of 0.5 ml/kg of the 3-in-1 mixture were given for induction of anesthesia. All patients were subsequently intubated and ventilated with an oxygen. Immediately after induction, the maintenance infusion rate was initially set at 2 ml/kg/hr for the first 5 to 10 minutes followed by 1 ml/kg/hr. If inadequate anesthetic depth or muscle relaxation was suspected clinically, a 5 ml bolus of the 3-in-1 mixture (rescue solution) was administered followed by a 10% stepwise increase in the infusion rate. Ten to fifteen minutes before the expected time of completion of surgery, the infusion rate of the 3-in-1 mixture was reduced to 0.5 ml/kg/hr and was stopped at the end of surgery. Results: The 3-in-1 mixtures remained stable for up to 5 hours after preparation. Induction and maintenance of anesthesia were smooth, intubation conditions satisfactory, and intraoperative hemodynamic changes acceptable. Recovery from anesthesia and neuromuscular blockade was rapid. There were no major intra- or immediate postoperative complications. Conclusions: It may be feasible to provide TIVA using the 3-in-1 mixture for induction and maintenance of anesthesia.

An improved survival model of hypoxia/ischaemia in the piglet suitable for neuroprotection studies

The purpose of this study was to develop a newborn piglet model of hypoxia/ischaemia which would better emulate the clinical situation in the asphyxiated human neonate and produce a consistent degree of histopathological injury following the insult. One-day-old piglets ( n=18) were anaesthetised with a mixture of propofol (10 mg/kg/h) and alfentinal (55.5 μg/kg/h) i.v. The piglets were intubated and ventilated. Physiological variables were monitored continuously. Hypoxia was induced by decreasing the inspired oxygen (FiO 2) to 3–4% and adjusting FiO 2 to maintain the cerebral function monitor peak amplitude at ≤5 μV. The duration of the mild insult was 20 min while the severe insult was 30 min which included 10 min where the blood pressure was allowed to fall below 70% of baseline. Control piglets ( n=4 of 18) were subjected to the same protocol except for the hypoxic/ischaemic insult. The piglets were allowed to recover from anaesthesia then euthanased 72 h after the insult. The brains were perfusion-fixed, removed and embedded in paraffin. Coronal sections were stained by haematoxylin/eosin. A blinded observer examined the frontal and parietal cortex, hippocampus, basal ganglia, thalamus and cerebellum for the degree of damage. The total mean histology score for the five areas of the brain for the severe insult was 15.6±4.4 (mean±S.D., n=7), whereas no damage was seen in either the mild insult ( n=4) or control groups. This ‘severe damage’ model produces a consistent level of damage and will prove useful for examining potential neuroprotective therapies in the neonatal brain.

The stability of remifentanil hydrochloride and propofol mixtures in polypropylene syringes and polyvinylchloride bags at 22 degrees-24 degrees C.

Remifentanil and propofol mixtures may be prepared extemporaneously. This study demonstrated that such mixtures are stable for 0 to 36 h, depending on relative concentrations of the drugs and the storage container used. The most stable mixtures were stored in syringes and used large concentrations of the two drugs.

Transformations of 2,6-Diisopropylphenol by NO-Derived Nitrogen Oxides, Particularly Peroxynitrite

To investigate the protective effect of the anesthetic 2,6-diisopropylphenol, or propofol, in oxidative processes in which •NO and peroxynitrite are involved, direct interactions were explored. The reactions of the highly lipophilic propofol with •NO in methanolic or aqueous buffered solutions under air were shown to produce the same compounds as those detected with peroxynitrite, but with very low yields and slow rates. In aqueous neutral medium, peroxynitrite (ONOO−, ONOOCO−2, ONOOH) was able to nitrate and oxidize propofol: In addition to oxidation products, quinone and quinone dimer, the formation of the 4-nitropropofol derivative was detected, increasing with peroxynitrite or CO2 concentrations. Nitration reached 20% after the addition of 25 mM bicarbonate to an equimolecular mixture of peroxynitrite and propofol in methanol/phosphate-buffered solution (1/4,v/v) at pH 7.4. However, peroxynitrite either in methanol or in alkaline-buffered mixture (optimum pH 10–12) resulted in the rapid and almost complete transformation of propofol to an intermediate compound 1, which further decomposed to 4-nitrosopropofol. The transient compound 1 was obtained from either peroxynitrite or •NO in the presence of oxygen. From mass spectrometry determination of compound 1 we propose the involvement of the nitrosodioxyl radical ONOO•, forming an adduct with the propofoxyl radical, to yield 4-nitrosodioxypropofol and finally 4-nitrosopropofol.

3327 A randomized trial comparing patient-controlled sedation using propofol/Alfentanil to diazemul/Pethidine in patients undergoing outpatient colonoscopy.

Background and Study Aims: PCS is increasingly used in day-case surgery. Its use seems ideal for colonoscopy as an outpatient procedure. In theory PCS leads to faster recovery and earlier discharge. Patients and Methods: Between July 1999 and October 1999 patients undergoing colonoscopy as an outpatient procedure were randomized to receive intravenous injection of diazemuls 0.1mg/Kg and pethidine 0.5mg/Kg or a mixture of propofol 400mg and alfentanil 1 mg delivered via a Graseby 3300 PCA pump in bolus of 2mg/ml (lockout period of 3 minutes). Patients' pulse rate and oxygen saturation were monitored continuously and blood pressure taken every 5 minutes. Outcome parameters included procedure time, recovery time, pain score (un-scaled 10cm visual analogue score), desaturation (oxygen saturation