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PubMed1997

Pharmacoeconomics of propofol in anesthesia.

Pharmacoeconomic data on the use of propofol in anesthesia are reviewed, with consideration of clinical characteristics that affect overall costs. Propofol is more expensive than many other anesthetics but its use can affect the costs of perioperative care as well as costs not directly related to the health care system, such as those associated with time off work. Using propofol can result in earlier discharge from the postanesthesia care unit (PACU), which can result in lower PACU costs. Anesthesia induction and maintenance with propofol versus barbiturates for induction and volatile anesthetics for maintenance have been associated with a lower frequency of postoperative nausea and vomiting (PONV) in the immediate postoperative period. A reduced frequency of PONV may improve the ability to increase patient flow through the PACU, which may reduce PACU costs. The cost of treating PONV in the PACU might not be high enough to justify the use of more expensive agents such as propofol solely for their reduced propensity to cause PONV. Propofol use has been associated with significantly shorter times to extubation of cardiac-surgery patients compared with the use of other agents. Early extubation has, in turn, been associated with shorter hospital stays, shorter stays in the cardiac intensive care unit, and lower hospital charges. Policy changes regarding criteria for discharge from the PACU may need to be implemented if the economic advantages of propofol are to be realized. Anesthesia with propofol, compared with other agents, has been associated with shorter stays in the PACU. Whether using propofol decreases the costs of care is unclear.

Anesthetics, Intravenous↗

PubMed1994

Does tolerance develop to the anaesthetic effects of propofol in rats?

We have studied the development of tolerance to the anaesthetic effects of propofol in rats. In the first set of experiments, three groups of rats (A, B and C) received i.v. propofol 10 mg kg-1, 15 mg kg-1 and 20 mg kg-1, respectively. The durations of anaesthesia were recorded, the rats were killed and blood was collected to measure the concentrations of propofol. In a second set of experiments, rats received propofol 10 mg kg-1 i.v. repeated 24 h (group D), 48 h (group E) or 72 h (group F) later. Sleeping times were recorded after the first and the second administration and concentrations of propofol at awakening were measured after the second dose, when rats were killed. Sleeping times were significantly longer in groups B (22.4 min) and C (25.9 min) compared with group A (13.7 min) (P < 0.001 for both). Durations of anaesthesia in groups D, E and F were 14.7, 14.5 and 14.3 min, respectively, after the first dose of propofol and 11.6, 12.1, and 14.9 min, respectively, after the second dose. The rats in groups D and E exhibited shorter sleeping times after the second dose of propofol than after the first (P < 0.01 for both). Concentrations of propofol at awakening did not differ between groups A, B and C or between groups D, E and F. The results suggest lack of changes in susceptibility of the CNS to the anaesthetic effects of propofol.

Anesthesia, General↗

PubMed1995

Comparison of the effects of propofol and isoflurane anaesthesia on right ventricular function and shunt fraction during thoracic surgery.

I.v. anaesthetic agents, including propofol, have not been shown to inhibit hypoxic pulmonary vasoconstriction (HPV). This may encourage the use of propofol in thoracic surgery where one lung ventilation (OLV) is required. We have compared the effects of maintaining anaesthesia with either isoflurane or propofol infusion on right ventricular function and shunt fraction. We studied 10 patients who received isoflurane and 12 who received propofol. When OLV commenced there was a greater reduction in both mean cardiac index (3.2 (SEM 0.2) to 2.4 (0.1) litre min-1 m-2 for propofol, and 3.4 (0.2) to 3.3 (0.4) litre min-1 m-2 for isoflurane) and right ventricular ejection fraction (0.45 (0.03) to 0.37 (0.02) for propofol, and 0.48 (0.02) to 0.42 (0.02) for isoflurane) in patients who received propofol. Furthermore, these reductions were sustained for longer in the propofol group. However, propofol was not associated with a significant increase in shunt fraction during OLV, which increased threefold in patients who received isoflurane.

Adult↗

PubMed1996

Antiemetic effect of subhypnotic doses of propofol after thyroidectomy.

Postoperative nausea and vomiting (PONV) are unpleasant, often underestimated side effects of anaesthesia and surgery, not devoid of medical complications. Prevention with antiemetics is only partially effective. Propofol has been shown recently to possess antiemetic properties in several situations. In this prospective, randomized, controlled trial, we have compared the antiemetic efficacy of subhypnotic doses of propofol, with Intralipid as placebo, after thyroidectomy. We studied 64 patients of both sexes, aged 22-71 yr, ASA I or II, undergoing thyroidectomy. After premedication with a benzodiazepine, balanced anaesthesia was produced with isoflurane and nitrous oxide in oxygen, and supplementary analgesia with fentanyl i.v. as required. Postoperative analgesia was provided with non-opioids, and piritramide 0.25 mg kg-1 i.m. on demand. Patients were allocated randomly and blindly to receive a 20-h infusion of either propofol or 10% Intralipid 0.1 ml kg-1 h-1. Intralipid, the excipient of propofol, was chosen as placebo as it is devoid of antiemetic effects. Sedation scores, respiratory and cardiovascular variables, and incidence of PONV were assessed every 4 h for 24 h. Pulse oximetry and ECG were monitored continuously. Both groups were comparable in characteristics, surgical and anaesthesia procedures, amount of opioids given during and after operation, and total amount of the study drug infused after operation. Occurrence of PONV was similar before the start (propofol 41%, Intralipid 50%) and after completion (propofol 0.64%, Intralipid 1.6%) of infusion and decreased with time in both groups during the infusion. However, symptoms were reduced to nil with propofol but persisted and were more severe with Intralipid during infusion (P < or = 0.01). The overall incidence of PONV during infusion was 10% (three of 32 patients) in the propofol group and 65% (21 of 32 patients) in the Intralipid group. Cardiovascular and respiratory variables, and SpO2 were unaltered, and sedation decreased similarly with time in both groups. We conclude that propofol, given at subhypnotic doses, effectively reduced the incidence of PONV without untoward sedative or cardiovascular effects.

Adult↗

PubMed1997

Effect of methohexitone and propofol with or without alfentanil on seizure duration and recovery in electroconvulsive therapy.

We have studied the effects of methohexitone and propofol with and without alfentanil on seizure duration and recovery in this observer-blinded, prospective, randomized, crossover study involving 24 patients undergoing electroconvulsive therapy (ECT). Each patient had four treatment sessions, and received the following four i.v. regimens in random order: methohexitone 0.75 mg kg-1, methohexitone 0.50 mg kg-1 and alfentanil 10 micrograms kg-1, propofol 0.75 mg kg-1, propofol 0.50 mg kg-1 and alfentanil 10 micrograms kg-1. Additional methohexitone or propofol was given as needed in 10-20-mg increments until loss of consciousness. Suxamethonium 1.0 mg kg-1 i.v. was given for muscular paralysis. Mean motor and EEG seizure durations were longer with methohexitone-alfentanil (44.7 (SD 15.0) and 70.5 (29.7) s) than with methohexitone (37.6 (12.6) and 52.6 (15.3) s) and similarly, seizures were longer with propofol-alfentanil (36.8 (15.2) and 54.5 (20.9) s) than with propofol alone (27.2 (11.9) and 39.2 (3.9) s). Seizures were longest with methohexitone-alfentanil and shortest with propofol. Recovery time was statistically shorter in patients receiving propofol compared with methohexitone-alfentanil and methohexitone alone. Alfentanil with a reduced dose of methohexitone or propofol provided unconsciousness and increased seizure duration in patients undergoing ECT. We conclude that the combination of methohexitone with alfentanil is a good regimen for ECT, especially for patients with short seizure duration.

Adult↗

PubMed1999

Effects of propofol on vascular reactivity in isolated aortae from normotensive and spontaneously hypertensive rats.

We have investigated the effects of propofol 50 mumol litre-1 on contractile and relaxant responses in experimental hypertension and assessed endothelial modulation of these responses. Propofol attenuated norepinephrine-induced contraction of endothelium-intact and endothelium-denuded rings from both Wistar Tokyo (WKY) and spontaneously hypertensive rats (SHR). The effect was significantly greater in endothelium-intact aortae from SHR than in those from WKY rats. Propofol markedly attenuated AVP-induced contraction in aortae from both WKY and SHR. Propofol attenuation of norepinephrine contraction was also observed in rings from both SHR and WKY rats incubated with L-NAME. Propofol attenuation of norepinephrine contraction was suppressed by indomethacin in aortae from SHR but not in those from WKY rats. These results suggest that: (1) propofol attenuated vascular contraction of isolated aortae from SHR in part by a mechanism dependent on events distal to the receptor site (norepinephrine, arginine vasopressin); (2) the effect of propofol on contraction in SHR, observed in the presence of nitric oxide synthase inhibitors but not cyclooxygenase inhibitors, was consistent with either propofol induction of vasodilating cyclooxygenase metabolites from the endothelium or propofol inhibition of vasoconstricting cyclooxygenase metabolites.

Anesthetics, Intravenous↗

PubMed2001

Comparison of relaxant effects of propofol on methacholine-induced bronchoconstriction in dogs with and without vagotomy.

Propofol has been suggested to have in vivo airway relaxant effects, although the mechanism is still unclear. In this study, we determined whether propofol could antagonize methacholine-induced bronchoconstriction and determined whether vagotomy modifies this relaxant effect. Fourteen mongrel dogs anaesthetized with pentobarbital and pancuronium were assigned to a control group (n=7) and a vagotomy group (n=7). The trachea was intubated with a special endotracheal tube that had a second lumen for insertion of the bronchoscope. Bronchial cross-sectional area, which was monitored continuously through the bronchoscope, was measured with image analysis software. Bronchoconstriction was elicited with methacholine (0.5 microg kg(-1) + 5.0 microg kg(-1) min(-1)) until the end of the experiment. Thirty minutes after the start of methacholine infusion, propofol 0, 0.2, 2.0 and 20 mg kg(-1) was administered. Changes in bronchial cross-sectional area were expressed as percentages of the basal area. Plasma concentrations of propofol and catecholamine were measured by high-performance liquid chromatography. Maximal inhibition (bronchoconstriction = 0%, baseline = 100%) and IC50 (concentration producing 50% inhibition of maximal effect) produced by propofol was obtained from each concentration-response curve using a curve-fitting program. Methacholine decreased bronchial cross-sectional area to 49.3% (95% confidence interval 38.5-60.1%) and 45.3% (34.8-55.7%) of the baseline value. Propofol 20 mg kg(-1) significantly reversed this effect: bronchial cross-sectional area was reduced to 77.8% (66.2-89.6%) and 75.9% (64.0-87.9) in the control and vagotomy groups respectively. The two groups did not differ significantly in the maximal inhibitory effect of propofol [control group, 61.1% (46.3-75.9%), vagotomy group, 64.2% (40.1-88.3%)] or pIC50 [control group 5.03 (4.55-5.51), vagotomy group 4.86 (4.49-5.24)]. Therefore, the relaxant effects of propofol on methacholine-induced bronchoconstriction may not be mediated centrally. Propofol may relax airway smooth muscles directly or through the peripheral vagal pathway.

Anesthetics, Intravenous↗

PubMed2003

Influence of propofol concentrations on multipulse transcranial motor evoked potentials.

BACKGROUND: Motor evoked potentials can be affected by propofol anaesthesia. We studied how increasing target concentrations of propofol altered transcranial motor evoked potentials (tcMEP) during scoliosis surgery. METHODS: Fifteen patients undergoing surgery for scoliosis were anaesthetized with remifentanil and propofol without nitrous oxide or neuromuscular blocking agents (BIS<60). tcMEP were elicited by transcranial electric multipulse stimulation of the motor cortex and recording of compound action potentials from the anterior tibialis muscle. tcMEP were obtained before surgery with propofol target values set from 4 to 8 mg litre(-1), and then during surgery. Arterial propofol concentrations were measured for each tcMEP recording. RESULTS: Before surgery, increasing propofol reduced tcMEP amplitude in a dose-dependent manner, with no effect on latency. During surgery, at equivalent propofol concentrations, tcMEP were not statistically different from those obtained before surgery. In all except one patient, tcMEP signals were present during the entire procedure. In this patient the loss of tcMEP was unfortunately related to an anterior spinal cord lesion, which was confirmed by a wake-up test. CONCLUSION: We found that, although propofol had a dose-dependent effect on tcMEP amplitude, anaesthesia could be maintained with remifentanil and propofol to allow recording and interpretation of tcMEP signals.

Adult↗

PubMed2004

Mid-latency auditory evoked response during propofol and alfentanil anaesthesia.

BACKGROUND: Propofol has been shown to affect the mid-latency auditory evoked response (MLAER) in a dose-dependant manner. Few studies have investigated the addition of alfentanil. Myogenic responses, such as the post-auricular responses (PAR), can confound the MLAER but there has been little investigation as to which electrode site reduces this interference. METHODS: We studied the MLAER in 27 women. They received an infusion of alfentanil 15 micro g kg(-1) h(-1), followed by either a high or low infusion regimen of propofol (final infusion rates 6 and 3 mg kg(-1) h(-1)). We compared the results with those of our study using propofol alone. We collected the data from two electrode sites: vertex-inion and vertex-mastoid. We evaluated the occurrence of the PAR and the shape of the MLAER at each electrode site. RESULTS: The infusion rate of propofol associated with loss of the eyelash response in 50% of subjects was 3.3 mg kg(-1) h(-1). This was significantly lower than using propofol alone (5.8 mg kg(-1) h(-1)). Nb latency was the best MLAER discriminator of unconsciousness (sensitivity 94%, specificity 88%), with a threshold of 46 ms (propofol alone was 53 ms). The addition of alfentanil did not alter the relationship between propofol infusion rate and MLAER. The vertex-inion electrode site gave the best protection against PAR in awake subjects (P=0.0003), and after 30 min of propofol infusion (P=0.06). The magnitude of the MLAER obtained from the vertex-mastoid electrodes was larger than from the other site, although the increase was not consistent throughout the waveform (brain stem 100%, Nb 14%). CONCLUSIONS: Addition of alfentanil lowers the propofol infusion rate required to produce unconsciousness and the Nb latency that predicts it. The better of the two sites to reduce the incidence of PAR is the vertex-inion electrode site.

Alfentanil↗

PubMed2005

Propofol 6% as sedative in children under 2 years of age following major craniofacial surgery.

BACKGROUND: After alarming reports concerning deaths after sedation with propofol, infusion of this drug was contraindicated by the US Food and Drug Administration in children <18 yr receiving intensive care. We describe our experiences with propofol 6%, a new formula, during postoperative sedation in non-ventilated children following craniofacial surgery. METHODS: In a prospective cohort study, children admitted to the paediatric surgical intensive care unit following major craniofacial surgery were randomly allocated to sedation with propofol 6% or midazolam, if judged necessary on the basis of a COMFORT behaviour score. Exclusion criteria were respiratory infection, allergy for proteins, propofol or midazolam, hypertriglyceridaemia, familial hypercholesterolaemia or epilepsy. We assessed the safety of propofol 6% with triglycerides (TG) and creatine phosphokinase (CPK) levels, blood gases and physiological parameters. Efficacy was assessed using the COMFORT behaviour scale, Visual Analogue Scale and Bispectral Index monitor. RESULTS: Twenty-two children were treated with propofol 6%, 23 were treated with midazolam and 10 other children did not need sedation. The median age was 10 (IQR 3-17) months in all groups. Median duration of infusion was 11 (range 6-18) h for propofol 6% and 14 (range 5-17) h for midazolam. TG levels remained normal and no metabolic acidosis or adverse events were observed during propofol or midazolam infusion. Four patients had increased CPK levels. CONCLUSION: We did not encounter any problems using propofol 6% as a sedative in children with a median age of 10 (IQR 3-17) months, with dosages <4 mg kg(-1) h(-1) during a median period of 11 (range 6-18) h.

Chemistry, Pharmaceutical↗

PubMed2005

Effect of clonidine pre-medication on propofol requirements during lower extremity vascular surgery: a randomized controlled trial.

BACKGROUND: Pre-medication with clonidine reduces the requirement for volatile agents during general anaesthesia. This may also be true for anaesthesia with propofol, but the amount of dose reduction has not been measured. Because clonidine also affects cardiac output and thus regional blood flow it could alter the pharmacokinetics of propofol. This randomized, double-blind placebo-controlled trial aimed to study the effect of clonidine pre-medication on dose requirement for propofol during lower extremity vascular surgery using the bispectral index (BIS) as a measure of anaesthetic depth. METHODS: After oral pre-medication with either clonidine 3 microg kg(-1) or placebo, 39 subjects had lower limb vascular surgery using propofol infusion for anaesthesia. Anaesthetic depth was adjusted to a BIS of 45. Predicted plasma propofol concentrations were noted every 30 min from a target-controlled propofol infusion pump and arterial samples were taken at the same time for propofol measurements. RESULTS: Patients in both groups were anaesthetized to similar depths of anaesthesia as indicated by BIS readings (P=0.44). The groups had comparable mean (95% CI) arterial concentrations of propofol, 4.8 (3.5-6.1) microg ml(-1) in the patients given clonidine, and 4.6 (3.4-5.7) microg ml(-1) in the patients given placebo (P=0.81). However, the average plasma concentration predicted by the target-controlled infusion was less in the clonidine group [3.2 (2.9-3.5)] than in the group given placebo [3.6 (3.3-3.9)] microg ml(-1) (P<0.05). CONCLUSIONS: Pre-medication with clonidine reduces the requirement for propofol, which is a pharmacokinetic effect and not a pharmacodynamic central sedative effect.

Aged↗

PubMed2005

Changes in the effect of propofol in response to altered plasma protein binding during normothermic cardiopulmonary bypass.

BACKGROUND: During normothermic cardiopulmonary bypass (CPB), the effect on propofol pharmacokinetics of changes in its binding to plasma proteins is consistent with the predictions of the well-stirred model of hepatic elimination for nonrestrictively cleared drug. However, whether changes in binding lead to clinically significant changes in the drug effect remains unclear. The purpose of this study was to assess changes in the drug effect of propofol in response to altered plasma binding using quantitative EEG measurements. METHODS: Thirty patients undergoing cardiac surgery were assigned randomly to receive propofol infusions at 4 (Group P-4) or 6 (Group P-6) mg kg(-1) h(-1) during surgery. The concentration of propofol in blood samples, collected from the radial artery at predetermined intervals, was determined by HPLC. The unbound fraction of drug in plasma was estimated using equilibrium dialysis. Bispectral index (BIS) and burst suppression ratio (BSR) were measured at the time blood samples were collected. RESULTS: The total concentration of propofol in blood was unchanged during CPB relative to the pre-CPB value in both groups. However, the fraction of unbound propofol in blood increased by 2-fold during CPB. While BIS values were unchanged during CPB in Group P-4, there was a slight, but significant, decrease in Group P-6. In both groups, BSR significantly increased during CPB. BIS values showed a weak correlation with the concentration of unbound propofol (r(2)=0.19, P<0.001). BSR showed a moderate correlation with the concentration of unbound propofol (r(2)=0.56, P<0.001). CONCLUSIONS: The anaesthetic effect of propofol significantly increased during CPB without any alteration in the total drug concentration. The enhanced efficacy may be caused by a reduction in plasma binding of the drug.

Adult↗

PubMed2006

Level of consciousness affects the excitability of spinal motor neurones during propofol sedation in humans.

BACKGROUND: To investigate the relationship between the depression of spinal motor neuronal excitability and the sedative level induced by propofol infusion, we simultaneously analysed the suppressive effect of propofol on the F wave and the sedative level during propofol infusion. METHODS: After spinal anaesthesia, sedation was achieved using a propofol target-controlled infusion (TCI) system to achieve a score of 4 on the Wilson sedation scale. The excitability of spinal motor neurones was determined by measuring the left median nerve F wave. F-wave persistence and the F/M ratio were recorded at pre-sedation as the control, during sedation, at arousal by mild physical stimulation and at post-sedation. RESULTS: Wilson sedation scores increased significantly corresponding to the increase in the target propofol concentration (Cpt), and a Cpt-producing Wilson sedation scale 4 ranged between 1.2 and 1.8 microg ml(-1). The F-wave persistence and F/M ratio before propofol infusion were 80.7 (8.6)% and 9.5 (3.9)%, respectively. At Wilson sedation scale 4, F-wave persistence and F/M ratio were 17.6 (12.8)% (0-37.5%) and 4.3 (4.1)%, and, at return of consciousness by mild physical stimulation, significantly increased to 71.3 (7.9)% and 10.0 (5.0)%, respectively. CONCLUSION: We demonstrated that the excitability of spinal motor neurones was suppressed during sedation by propofol TCI, but this suppressive effect vanished at return of consciousness by mild physical stimulation even at a constant Cpt. Our data suggested that the effect of propofol on the excitability of spinal motor neurones might be affected by consciousness level rather than propofol Cpt in humans.

Adult↗

PubMed1992

Propofol anaesthesia for ultrasound guided oocyte retrieval: accumulation of the anaesthetic agent in follicular fluid.

Propofol (2,6-diisopropylphenol, Diprivan, ICI-Pharmaceuticals, Manchester, UK) is widely used either as an adjunct in general anaesthesia or as sole anaesthetic agent by the continuous intravenous route and intermittent bolus injections for minor surgical interventions. For several years, we have been using this kind of anaesthesia in transvaginal oocyte retrieval for in-vitro fertilization (IVF), allowing a completely painless puncture on an out-patient basis. From in-vitro studies on mouse oocytes, it appeared that propofol could be deleterious for fertilization in a dose- and time-dependent manner. We therefore investigated the concentrations of propofol in follicular fluid during oocyte retrieval in women. We measured propofol levels in serum and follicular fluid of nine patients at fixed intervals during ultrasound guided oocyte retrieval. Serum levels fluctuated randomly, due to interference from top-off doses of propofol. In follicular fluid, however, we found a steady increase of propofol levels, which was proportional to the total dose of propofol administered. These data indicate that propofol accumulates in follicular fluid. Although it seems unlikely that propofol as used in the present protocol exerts a clinically significant unfavourable effect on IVF, we suggest that the oocyte retrieval procedure should be kept as short as possible, in order to limit the accumulation of the anaesthetic in follicular fluid.

Dose-Response Relationship, Drug↗

PubMed1996

Inhibition of regulated neuropeptide secretion from mouse pituitary cells by propofol.

Neuropeptides modulate neuronal responses to stimuli. Secretion of neuropeptides is a potential site for anesthetic action. This paper examines the hypothesis that propofol alters the secretion of beta-endorphin. Cultures of a mouse pituitary cell line (AtT-20) were exposed to propofol in vitro, then induced to secrete beta-endorphin. Secretion was measured by immunoassay. Propofol caused statistically significant inhibition of secretion. Secretion stimulated by phorbol ester was inhibited by propofol with a calculated 50% inhibitory concentration (IC50) value of 48 microM. The propofol IC50 values for secretion stimulated by other secretagogs were 47 microM (barium), 42 microM (Bay K 8644, a calcium channel agonist), and 28 microM (a cyclic adenosine monophosphate [cAMP] analog). AtT-20 cells recovered their ability to secrete beta-endorphin upon removal of the propofol, which demonstrated that they were not damaged permanently by propofol. The effect was relatively specific to neuropeptide secretion, as AtT-20 cells grew normally for 5 days in the presence of 10 or 80 microM propofol. The finding suggests that propofol inhibited a site in neuropeptide exocytosis common to the three studied pathways of secretion.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1996

The direct effects of propofol on myocyte contractile function after hypothermic cardioplegic arrest.

Propofol is being used more often in cardiac surgery, particularly after hypothermic, hyperkalemic cardioplegic arrest (HHCA). The purpose of this study was to examine the effects of propofol on isolated myocyte contractile function under both normothermic conditions and after simulated HHCA and rewarming. Myocytes were isolated from the left ventricle of eight pigs. Myocyte contractile function was measured under both normothermic conditions and after simulated HHCA (incubation at 4 degrees C for 2 h in crystalloid cardioplegia; K+ = 24 mEq/L) using computer-assisted videomicroscopy in the presence of 2, 4, and 6 micrograms/mL propofol (11.2, 22.4, and 33.6 microM/L, respectively). Isoproterenol (25 nM) was then added and contractile function measurements repeated. Propofol caused significant dose-dependent reductions in myocyte velocity of shortening (baseline = 67 +/- 2 microns/s; propofol = 2 micrograms/mL, 45 +/- 4 microns/s; and propofol = 6 micrograms/mL, 27 +/- 3 microns/s; P < 0.05). HHCA and rewarming caused a significant reduction in myocyte velocity of shortening (29 +/- 0.9 microns/s, P < 0.05), with further significant dose-dependent reductions in contractile function after the addition of propofol. Propofol caused a decrease in beta-adrenergic responsiveness under normothermic conditions, but not after simulated HHCA. Results from the present study demonstrated for the first time that the reduction in isolated myocyte contractile function after simulated HHCA is further decreased by propofol administration.

Adrenergic beta-Agonists↗

PubMed1997

Age-related propofol effects on electrophysiological properties of isolated hearts.

We compared the direct effects of propofol on the conduction system of neonatal (< 7 days) and adult (> 3 mo) rabbit hearts using intracardiac recording/ stimulation in Langendorff-perfusion and autonomic blockade. At a low concentration (3 microM), propofol caused a slight but significant lengthening of the atrio-ventricular (AV) conduction interval of the adult hearts, but not of neonatal hearts. At a higher concentration (10 microM and above), propofol significantly prolonged the AV conduction interval in a frequency-dependent manner in both neonates and adults. The AV Wenckebach cycle length was also lengthened, with the change more significant in the adults. However, with concentrations of propofol up to 100 microM, the neonatal hearts frequently (9 of 13 experiments) progressed to complete AV block, which was not observed in the adults. Conduction through the atrial tissue (SA interval) and the His-Purkinje system (HV interval), as well as the spontaneous heart rate, were all slowed by propofol at 30 microM or above. However, the lengthening of SA interval was more pronounced in the neonates, and only in the neonate was the atrial refractory period prolonged by propofol at 10 microM and above. We conclude that 3 microM propofol produces no significant direct effects on the neonatal cardiac electrophysiological properties, although AV conduction of the adult heart may be suppressed at this concentration of propofol. At higher concentrations, age-related propofol effects were demonstrated in the AV node and the atrial tissue.

Aging↗

PubMed1997

Use of alfentanil and propofol for outpatient monitored anesthesia care: determining the optimal dosing regimen.

UNLABELLED: Propofol and alfentanil are both rapid and short-acting drugs that can be used for sedation and analgesia during monitored anesthesia care (MAC). This study was designed to determine the optimal infusion rates of propofol and alfentanil when administered during local anesthesia. In this randomized, double-blind study, we evaluated the effects of different propofol infusion rates on the alfentanil requirement, level of sedation, intraoperative recall, respiratory and cardiovascular variables, and recovery. Seventy-two consenting ASA physical status I or II female outpatients undergoing breast biopsy procedures with local anesthesia were randomly assigned to one of four treatment groups. All patients received midazolam, 2 mg intravenously (I.V.) for premedication. Propofol was infused at 0, 25, 50, or 75 microg x kg(-1) x min(-1) during the operation. Sedation was evaluated using the Observer's Assessment of Alertness/Sedation (OAA/S) scale at 5-min intervals by a blinded observer. Two minutes before the infiltration of the local anesthetic solution, a bolus of alfentanil, 2.5 microg/kg I.V., was administered, followed by a maintenance infusion of 0.5 microg x kg(-1) x min(-1). The alfentanil infusion rate was subsequently varied to maintain patient comfort and stable cardiovascular and respiratory function. Pictures were shown at the start of the propofol infusion, upon initiating the alfentanil infusion, and at 45 min after the skin incision to evaluate recall of intraoperative events. Propofol produced dose-dependent increases in the level of sedation (with median OAA/S scores of 2-4, P < 0.05). Higher infusion rates of propofol (50-75 microg x kg(-1) x min(-1)) produced significant amnesia, opioid-sparing effects (alfentanil 0.3 +/- 0.2 vs 0.6 +/- 0.2 microg x kg(-1) x min(-1)), and less postoperative nausea and vomiting (P < 0.05). However, episodes of transient hemoglobin oxygen desaturation were more common in the deeply sedated patients. Thus, in healthy outpatients premedicated with midazolam, 2 mg I.V., a propofol infusion of 25-50 microg x kg(-1) x min(-1) in combination with an alfentanil infusion of 0.2-0.4 microg x kg(-1) x min(-1) is recommended for sedation and analgesia during MAC in the ambulatory setting. IMPLICATIONS: Sedation is often given during local anesthesia. This study demonstrated that administration of an intravenous anesthetic, propofol, in combination with an opioid infusion (i.e., alfentanil) to provide sedation analgesia and amnesia with a low incidence of side effects, such as nausea and vomiting and respiratory depression in outpatients premedicated with midazolam.

Adult↗