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Biomedical subjects

K Leslie

Publications and source records attributed to K Leslie.

At least 19 recordsLinked to original sources
PubMed1999

Common peroneal nerve stimulation for neuromuscular monitoring: evaluation in awake volunteers and anesthetized patients.

UNLABELLED: The study was conducted in two parts. First, evoked responses to common peroneal nerve stimulation at four electrode positions were tested in 25 awake volunteers. The initial threshold stimulus current (ITS) (minimal current producing dorsiflexion or eversion of the ankle joint and great toe) and the supramaximal stimulus current (SMS) (the point at which further increases in current did not produce increases in twitch tension) were defined. SMS was not reliably achieved using electrodes at each side of the fibular head. However, an exploratory electrode accurately located the nerve and enabled SMS in all volunteers (SMS/ITS = 3.4). Second, 16 anesthetized, paralyzed patients were studied. The common peroneal and ulnar nerves were stimulated simultaneously. Evoked tension was recorded at the adductor pollicis using a force transducer and at the great toe by a blinded observer. Reversal was given when the train-of-four count at the great toe reached four. Onset times were longer, and median posttetanic counts were greater, at the great toe compared with the adductor pollicis. Time from reversal to train-of-four ratio = 0.7 at the adductor pollicis was 207+/-160 s. We conclude that neuromuscular monitoring at the common peroneal nerve was not equivalent to monitoring at the ulnar nerve. IMPLICATIONS: Accurate neuromuscular monitoring is important for patient safety. We studied the accuracy of monitoring at the common peroneal nerve in volunteers and patients. An exploratory electrode accurately located the common peroneal nerve. Monitoring at the common peroneal nerve was not equivalent to monitoring at the ulnar nerve in patients.

Adult↗
PubMed1998

Epidural fentanyl reduces the shivering threshold during epidural lidocaine anesthesia.

UNLABELLED: Epidural local anesthetics and IV opioids both decrease the core temperature that triggers shivering. However, the effect of epidural opioids on shivering thresholds has not been assessed. In this study, we tested the hypothesis that adding epidural fentanyl to epidural lidocaine decreases the shivering threshold compared with epidural lidocaine alone. Fourteen healthy male patients undergoing extracorporeal shockwave lithotripsy under epidural anesthesia were randomly assigned to receive either epidural lidocaine or epidural lidocaine plus epidural fentanyl. Ice-cold lactated Ringer's solution was given IV before epidural blockade, and the core temperature that triggers shivering was established. Then epidural anesthesia was induced, and the shivering threshold was established again after lithotripsy. Results were analyzed using paired or unpaired t-tests. Reduction in the shivering threshold by epidural anesthesia was significantly greater when fentanyl was added to lidocaine than when lidocaine was used alone (mean +/- SD: -0.6+/-0.4 degrees C versus -0.1+/-0.4 degrees C; P < 0.02). We conclude that patients are at increased risk of hypothermia when fentanyl is added to epidural lidocaine. IMPLICATIONS: Fentanyl is often added to lidocaine to improve the quality of epidural blockade and to reduce side effects. However, this study shows that patients are at increased risk of hypothermia when fentanyl is added to lidocaine.

Adult↗
PubMed1998

The association between selected metabolic parameters and left abomasal displacement in dairy cows.

The objective of this study was to examine the association between selected metabolic parameters and subsequent left displaced abomasum (LDA) diagnosis in dairy cows. Forty-four LDA cows sampled in the third week ante partum (a.p.) which was at a median of 34 days prior to LDA diagnosis, 36 LDA cows sampled in the first week post partum (p.p.) which was at a median of 14 days prior and 28 LDA cows sampled in the second week p.p., which was at a median of 9 days prior to LDA diagnosis were used. Each case was matched to 3 controls by herd and calving date. Data were available from a large field study. Aspartate-aminotransferase (AST) activity, the concentrations of beta-hydroxybutyrate (BHB), glucose, calcium and urea in blood, and the body condition score (BCS) were studied. Logistic regression was used to analyse the association between these parameters and subsequent LDA, adjusting for the effects of parity and pretreatment. A separate model was used for each sampling week and each parameter. In the third week a.p. none of the parameters were significantly associated with LDA. AST and BHB sampled in the first week p.p. and in the second week p.p. were significantly associated with LDA diagnosis. The higher the AST and BHB, the higher the odds of being diagnosed subsequently with LDA. The lower glucose and Ca in the second week p.p. the higher the odds of subsequent LDA diagnosis. Urea and BCS were not significantly associated with LDA in any of the weeks examined. We conclude that AST and BHB in the first and second week p.p. might be used as tests for subsequent LDA. Glucose, calcium, urea and body condition were either not significantly associated with LDA or significantly associated only in the second week p.p.; this may limit their use as tests for LDA.

3-Hydroxybutyric Acid↗
PubMed1998

Analysis of survivorship after displaced abomasum is diagnosed in dairy cows.

The objective of this study was to analyze the survivorship of dairy cows after displaced abomasum was diagnosed. Survivorship from the calving preceeding diagnosis of displaced abomasum to removal from the herd was investigated for cows that were diagnosed with displaced abomasum compared with herdmates. For cows that were diagnosed with displaced abomasum, factors that affected survivorship from the diagnosis of the disease to removal were investigated. Data from a total of 135 cows that had been diagnosed with displaced abomasum and 373 controls matched by herd and lactation number were available from a database at the University of Guelph. The hazard rate of removal from the herd was estimated using proportional hazard regression adjusted for intraherd correlation. Diagnosis of displaced abomasum significantly increased the hazarad rate of removal from the herd. For cows that were diagnosed with displaced abomasum the hazard rate of removal increased as parity increased. However, the hazard rate decreased with recurrent displaced abomasum and with higher days in milk at diagnosis of the disease. Although the 305-d milk production of cows that were diagnosed with displaced abomasum was lower during the lactation when the disease was diagnosed, 305-d milk production was not associated with removal of cows with that disease from the herd. Milk production during subsequent lactations did not differ between cows that were diagnosed with displaced abomasum and control cows. Low milk production during the subsequent lactations increased the hazard of removal of cows with that disease from the herd.

Abomasum↗
PubMed1998

Evaluation of five cowside tests for use with milk to detect subclinical ketosis in dairy cows.

The objective of this study was to evaluate the characteristics of five ketone tests for use with milk to detect subclinical ketosis [defined as > 1200 mumol of beta-hydroxybutyrate (BHBA)/L of blood] in dairy cows. The tests studied were the Ketolac BHB strip to detect BHBA (Hoechst, Unterschleissheim, Germany) and four tests based on sodium nitroprusside to detect acetoacetate (Rothera tests) [Ketostix strip (Bayer, Etobicoke, ON, Canada), Bioketone powder (Societé d' Analyses Biopharmaceutiques, Laval, QC, Canada), Ketocheck powder (Great States, St. Joseph, MO), and Utrecht powder (University of Utrecht, Utrecht, The Netherlands)]. Milk samples (n = 529) from 266 cows in 25 Ontario dairy herds were used for this investigation. The Ketolac BHB strip at 50 and 100 mumol of BHBA/L of milk showed sensitivities of 92 and 72%, respectively. This test was more sensitive for subclinical ketosis than were any of the Rothera tests. The sensitivities of the Rothera tests were 43, 33, 28, and 5%, respectively, for Utrecht powder, Bioketone powder, Ketocheck powder, and Ketostix strip. The Rothera tests were highly specific, as was the Ketolac BHB strip at 200, 500, and 1000 mumol of BHBA/L of milk (specificity, > 97%). The prevalence of subclinical ketosis was highest during the first 6 wk of lactation, and a peak was detected during the 2nd wk of lactation. Of the tests evaluated in this study, Ketolac BHB strip was the most useful to monitor subclinical ketosis in dairy herds.

3-Hydroxybutyric Acid↗
PubMed1998

Extension of useful reagent shelf life beyond manufacturers' recommendations. Cell Markers Committee of the College of American Pathologists.

OBJECTIVE: The College of American Pathologists Cell Markers Committee designed a study to evaluate the use of immunohistochemistry primary antibodies beyond manufacturers' recommended dates. METHODS: Pathologists were asked to save aliquots of primary antibodies during mid-1997 so that by spring 1998 the reagents would be "outdated" according to manufacturers' recommendations. Three tumors were immunostained both in mid-1997 and early 1998 (using outdated reagents in 1998). Two hundred twenty-one laboratories participated. PATIENT SAMPLES: Immunostained materials consisted of an angiomyolipoma immunostained for muscle-specific actin and HMB-45, a melanoma immunostained for S100 protein and HMB-45, and a large cell lymphoma immunostained for common leukocyte antigen and HMB-45. Blocks from the same tumor were used in each instance. MAIN OUTCOME MEASURE: We compared the immunostaining results as a percentage of laboratories indicating a positive or negative immunohistochemical result between the 1997 and 1998 time points. RESULTS: Only minor differences were identified for the 221 reporting laboratories in 1998 as compared with those in 1997. CONCLUSIONS: The data suggest review of the Health Care Financing Administration's ruling on extending the useful reagent shelf life beyond manufacturers recommendations. Similar studies using more inherently quantitative methodology are suggested.

Antibodies↗
PubMed1998

The implications of hypothermia for early tracheal extubation following cardiac surgery.

Thermoregulation is impaired during anesthesia for cardiac surgery. Redistribution of body heat and heat loss to the environment result in mild hypothermia before cardiopulmonary bypass. Maintenance of normothermia, rather than hypothermia, may facilitate early tracheal extubation. Hypothermia alters the distribution and decreases the metabolism of most drugs, including anesthetic drugs and muscle relaxants, thus prolonging recovery. Postoperative shivering increases metabolic rate and potentially leads to myocardial ischemia; prevention is therefore critical to the success of early tracheal extubation after cardiac surgery. Coagulopathies, increased incidence of surgical wound infection, and perioperative cardiac morbidity are other potential risk factors identified in noncardiac patients. Hypothermia, however, does have potential benefits to the patient, including protection from cerebral ischemia and hypoxemia. Mild core hypothermia (approximately 34 degrees C) may represent the optimal balance between risks and benefits for fast-track patients.

Anesthesia Recovery Period↗
PubMed1997

The arterial blood propofol concentration preventing movement in 50% of healthy women after skin incision.

To target appropriate drug concentrations and to facilitate comparisons between drugs, the potency of propofol must be firmly established. We therefore determined the arterial blood propofol concentration preventing movement in 50% of patients after skin incision and the ability of arterial blood pressure and heart rate to predict movement after incision. Fifteen healthy women scheduled for breast surgery were randomly assigned to computer-targeted propofol blood concentrations. No other drugs were administered. Fifteen minutes after starting the propofol infusion, a 5-cm skin incision was made. Patients were observed for gross purposeful movement for 1 min. Arterial blood was sampled for propofol to confirm steady-state blood concentrations. Arterial blood pressure and heart rate were measured noninvasively. Logistic regression was used to calculate the propofol blood concentrations and arterial blood pressures at which 50% and 95% of patients did not move after skin incision (CP50 and CP95, MABP50 and MABP95, respectively). The CP50 and CP95 values for propofol were 14.3 +/- 1.6 microg/mL (mean +/- SE) and 20.6 microg/mL, respectively. The MABP50 and MABP95 values were 63 +/- 4 mm Hg and 43 mm Hg, respectively. Heart rate did not differ significantly in patients who moved and who did not move. Propofol blood concentrations required to prevent movement in most patients resulted in significant arterial hypotension.

Adult↗
PubMed1997

Fat/protein ratio in first DHI test milk as test for displaced abomasum in dairy cows.

First DHI test milk that was sampled prior to displaced abomasum (DA) diagnosis was used to evaluate milk fat/protein ratio (FPR) for prediction of subsequent DA in dairy cows. Odds ratio, sensitivity, specificity, predictive values, and likelihood ratio were determined. Twenty-seven DA cases were matched to three controls per case by herd and calving date. Milk was tested 18 to 23 days (95% CI) after calving, which was 9 to 17 days (95% CI) prior to DA diagnosis. Adjusted for parity and days in milk, a fat/protein ratio > or = 1.4 was 8.6 times more likely (95% CI, 2.8 to 26) to come from a cow subsequently diagnosed with DA than a fat/protein ratio < 1.4. Using the cut off value of 1.4, the sensitivity of the FPR for DA was 80% and the specificity was 69%. A response operating characteristics curve indicated that the minimum sum of false negative and false positive results was at an FPR cut off value of 1.4. The likelihood ratio indicated that fat/protein ratios > or = 1.6 are 3.3 times more likely to come from cows that are diagnosed subsequently with DA than from cows without DA. The fat/protein ratio in first DHI test milk might be useful as a test for subsequent DA in dairy cows.

Abomasum↗
PubMed1997

An evaluation of milk ketone tests for the prediction of left displaced abomasum in dairy cows.

Two commercial milk ketone tests (Ketocheck) Great States, St. Joseph, MI and Ketolac BHB; Hoechst, Unterschleissheim, Germany) were used with milk samples collected within 2 wk postpartum to evaluate the use of these tests in the prediction of left displaced abomasum in dairy cows. Odds ratios, sensitivities, specificities, and likelihood ratios were determined. For the study of Ketocheck, 47 milk samples from 26 cows that were later diagnosed with left displaced abomasum were taken at a median of 6 d postpartum (12 d prior to diagnosis of the disease. For the study of Ketolac BHB, 26 milk samples from 15 cows that were later diagnosed with left displaced abomasum were taken at a median of 6 d postpartum (11 d prior to diagnosis of the disease). Each cow that was subsequently diagnosed with left displaced abomasum was matched with three control cows by herd and calving date. Positive Ketocheck results and Ketolac BHB results that indicated > or = 100 or > or = 200 mumol of beta-hydroxybutyrate (BHBA)/L of milk were significantly associated with the subsequent diagnosis of left displaced abomasum. The sensitivity of Ketocheck for the prediction of left displaced abomasum was 22%; specificity was 96%. The sensitivity of Ketolac BHB for the prediction of left displaced abomasum was 46% when the results indicated > or = 100 mumol of BHBA/L and was 34% when the results indicated > or = 200 mumol of BHBA/L. Ketocheck and Ketolac BHB might be used as tests for the prediction of left displaced abomasum when used with milk sampled within 2 wk postpartum. Hyperketolactia is a significant risk factor of left displaced abomasum.

Abomasum↗
PubMed1997

Evaluation of aspartate transaminase activity and beta-hydroxybutyrate concentration in blood as tests for prediction of left displaced abomasum in dairy cows.

OBJECTIVE: To evaluate aspartate transaminase (AST) activity and beta-hydroxybutyrate (BHB) concentration in blood obtained during the first or second postpartum (PP) week as tests for prediction of subsequent left displaced abomasum (LDA) diagnosis in dairy cows. ANIMALS: 36 cows with LDA tested at a mean 3 PP days, which was 7 to 22 days prior to LDA diagnosis (25, 75% quantiles), and 28 cows with LDA tested at 10 PP days, which was 5 to 18 days prior to LDA diagnosis, were matched to 3 controls per case by herd and calving date. Data were available from a large field study. PROCEDURE: Odds ratio, sensitivity, specificity, and likelihood ratio were determined for various AST and BHB cutoff values. RESULTS: AST, using cutoff values between 100 and 180 U/L, and BHB, using cutoff values between 1,000 and 1,600 mumol/L, were significantly associated with subsequent LDA diagnosis. When cutoff values were increased, odds ratio and likelihood ratio increased; however, sensitivity decreased and specificity increased. CONCLUSION AND CLINICAL RELEVANCE: AST activity and BHB concentration in blood obtained during the first or second PP week might be useful as predictors of subsequent LDA diagnosis.

3-Hydroxybutyric Acid↗
PubMed1996

Bone mass and soft tissue composition in adolescents with anorexia nervosa.

The relationship between bone mass and compartments of soft tissue was studied in 22 adolescent women with anorexia nervosa (mean, 17 years). Results were compared to data on age- and gender-matched controls. Bone mass of the lumbar vertebrae and femoral neck, fat and lean tissue was measured by dual energy X-ray absorptiometry (DXA). Bone mass in the central third of the skeleton, by neutron activation analysis (NAA), and body protein, by prompt gamma ray analysis (PGA), was measured on patients, but not controls. The patients had significantly lower values than controls in total weight (26%), lean tissue (16%), fat (60%), bone mass of lumbar spine (14%), and femoral neck (15%). The mean calcium bone index (CaBI), the central skeletal calcium normalized for body size based on height, was significantly lower than the value for external controls, (0.86 +/- 0.10 vs. 0.97 +/- 0.10). The nitrogen index (NI), body protein normalized for height, showed a similar reduction from external controls (0.84 +/- 0.10 vs. 1.0 +/- 0.10). Bone mass (both DXA and NAA data) was strongly correlated to lean tissue and to protein; the correlations to fat were weaker. Follow-up studies after 7-26 months in 12 patients showed a modest increase in weight (mean, 4.9 kg) which was due, primarily, to an increase in fat with only insignificant increase in lean tissue and in protein. In bone mass, there was either no change or further loss. Only four restored body weight to normal (BMI > 20) and they achieved normal menstruation, but even these four responders showed no increase in bone mass. Our studies confirm that adolescent females with anorexia nervosa suffer losses not only in all compartments of body composition, but also demonstrate that the restoration of bone mass lags behind improvement in soft tissue compartments. These results were independent of methods used for the measurements.

Absorptiometry, Photon↗
PubMed1996

Prediction of movement during propofol/nitrous oxide anesthesia. Performance of concentration, electroencephalographic, pupillary, and hemodynamic indicators.

BACKGROUND: Movement in response to painful stimulation is the end point classically used to assess the potency of anesthetic agents. In this study, the ability of modeled propofol effect-site concentration to predict movement in volunteers during propofol/nitrous oxide anesthesia was tested, then it was compared with the predictive abilities of the Bispectral Index and 95% spectral edge frequency of the electroencephalogram, pupillary reflex amplitude, and systolic arterial blood pressure. In addition, the relationships between simple end points of loss and recovery of consciousness, and pupillary, hemodynamic, and propofol concentration indicators were studied. METHODS: Ten healthy volunteers were anesthetized with an infusion of propofol, which was increased in three equal steps to 21 mg.kg lean body mass-1.h-1. After loss of the ability to hold a syringe and of the eyelash reflex, 60% nitrous oxide was introduced and the trachea was intubated without the use of muscle relaxants. The propofol infusion rate then was decreased to 15.4 mg.kg lean body mass-1.h-1. Ten minutes later, tetanic electrical stimulation was administered to the thigh via needle electrodes: if movement was observed within 1 min, the propofol infusion rate was increased by 1.75 mg.kg lean body mass-1.h-1 5 min after the stimulus; if not, it was similarly decreased. This 15-min sequence was repeated until volunteers "crossed over" from movement to no movement (or vice versa) four times. The propofol infusion rate then was increased to 21 mg.kg lean body mass-1.h-1, nitrous oxide was discontinued, the trachea was extubated, and the infusion rate was decreased in five equal steps over 50 min. The times at which the eyelash reflex returned and the birth date was recalled were recorded. The electroencephalogram was monitored continuously (FP1, FP2, ref: nasion, ground: mastoid). Measurements of the pupillary response, arterial blood pressure, and heart rate were recorded during induction and awakening, just before and for 5 min after each stimulation. Arterial blood samples were obtained for propofol assay, and propofol effect-site concentrations were calculated at each time. The predictive value of indicators was compared using a new static, the prediction probability (PK). RESULTS: Loss and return of the eyelash reflex occurred at greater propofol effect-site concentrations than either dropping the syringe or recall of the birthday. The propofol effect-site concentration (in the presence of 60% nitrous oxide) predicted to prevent movement after a supramaximal stimulus in 50% of volunteers was 1.80 micrograms/ml (95% confidence limits: 1.40-2.34 micrograms/ml). The Bispectral Index (PK = 0.86), 95% spectral edge frequency (PK = 0.81), pupillary reflex amplitude (PK = 0.74), and systolic arterial blood pressure (PK = 0.78) did not differ significantly from modeled propofol effect-site concentration (PK = 0.76) in their ability to predict movement. CONCLUSIONS: Indicators of pharmacodynamic effect, such as the electroencephalogram, pupillary light reflex, and systolic arterial blood pressure, predict movement as well as effect-site concentration during propofol/nitrous oxide anesthesia. Loss and return of the eyelash reflex correspond to a deeper level of anesthesia than syringe-dropping or recall of the birth date.

Adult↗
PubMed1996

Reduction in the shivering threshold is proportional to spinal block height.

BACKGROUND: Hypothermia is nearly as common, and may be as severe, during spinal and epidural anesthesia as during general anesthesia. The authors have proposed that thermoregulatory failure results when regional anesthesia increases apparent leg skin temperature to a level far exceeding actual leg skin temperature. Extensive dermatomal blocks will alter thermal input to the hypothalamus from a greater skin-surface area more than less extensive ones and thus might be expected to impair central thermoregulatory control more. Accordingly, they tested the hypothesis that reduction in the shivering threshold is directly related to the number of dermatomes blocked during spinal anesthesia. METHODS: Eleven men, aged 62 +/- 6 yr (mean +/- SD), undergoing urologic surgery were studied. Ice-cold lactated Ringer's solution was administered intravenously before spinal blockade and the shivering threshold (triggering core temperature) was established. Spinal anesthesia then was induced using a randomly assigned dose of 0.5% bupivacaine (2-4 ml). Again, sufficient cold lactated Ringer's solution was given to induce shivering. Tympanic membrane, ambient and skin temperatures were measured, and extent of block was defined by loss of temperature discrimination. Presence of shivering was evaluated by a blinded observer. Mean upper-body skin and ambient temperatures, cooling rates and intravenous fluid volumes at the two thresholds were compared using paired, two-tailed t tests (P < 0.05). Linear regression defined the relationship between reduction in shivering threshold and the number of dermatomes blocked. RESULTS: There were no significant differences between mean upper-body skin and ambient temperatures, cooling rates or intravenous fluid volumes at the control and spinal shivering thresholds. Spinal anesthesia reduced the shivering threshold in direct relation to the number of dermatomes blocked: delta threshold = 0.74 - 0.06 (dermatomes blocked); r2 = 0.58, P < 0.006. CONCLUSIONS: Extensive spinal blockade impairs central thermoregulatory control more than less extensive blockade. Clinicians can thus anticipate more core hypothermia during extensive than during restricted spinal blockade.

Aged↗
PubMed1996

Axillary brachial plexus block in two hundred consecutive patients.

Two hundred consecutive, minimally-sedated patients presenting for upper limb surgery were audited prospectively to determine the overall clinical success rate, extent of cutaneous neural blockade, reliability and complication rate of each indicator of axillary sheath entry, and degree of patient satisfaction. The axillary sheath was identified, using a 22 gauge, short-bevelled needle, by one of four indicators, whichever was elicited first (paraesthesia, arterial or venous puncture, or tethering by the axillary sheath). Alkalinized mepivacaine 1.2%, 50 ml then was injected. The cutaneous distribution of the block was mapped in the presence of minimal sedation. Anaesthesia was supplemented with peripheral nerve blocks where necessary. Patients were followed up with a mailed questionnaire and surgeon interview. The overall clinical success rate was 92.5%, improving to 99% with supplementary nerve blocks. Complete anaesthesia distal to the elbow was achieved in 85% of patients. Complications were common, but generally mild and transient: mild acute local anaesthetic toxicity, 3.5%; axillary tenderness and bruising, 12%; and dysaesthesias, 12.5%. Despite this, patient satisfaction was high (97%).

Adolescent↗
PubMed1995

Mild hypothermia alters propofol pharmacokinetics and increases the duration of action of atracurium.

Mild intraoperative hypothermia is common. We therefore studied the effects of mild hypothermia on propofol pharmacokinetics, hepatic blood flow, and atracurium duration of action in healthy volunteers. Six young volunteers were studied on two randomly assigned days, at either 34 degrees C or 37 degrees C. Anesthesia was induced with thiopental, 3 mg/kg, and maintained with 70% N2O and 0.6% isoflurane. Core hypothermia was induced by conductive and convective cooling. On the other study day, normothermia was maintained by a Bair Hugger (Augustine Medical, Inc., Eden Prairie, MN) forced-air warmer. Propofol, 1 mg/kg lean body mass (LBM), then was given, followed by a 4-h infusion at 5 mg.kg-1.h-1. After 2 h, atracurium 0.5 mg/kg was administered as an intravenous bolus. Indocyanine green was administered for estimation of hepatic blood flow. Arterial blood was assayed for propofol and indocyanine green concentration. Pharmacokinetic analysis was performed using NONMEM. Results are reported as means +/- SEM. Propofol blood concentrations averaged approximately 28% more at 34 degrees C than at 37 degrees C (P < 0.05). Hepatic blood flow decreased 23% +/- 11% in normothermic volunteers during the propofol infusion, and 33% +/- 11% in hypothermic volunteers (P = not significant). A three-compartment mamillary model fitted the data best. Inclusion of hepatic blood flow change from the prepropofol baseline as a covariate for total body clearance significantly improved the fit. The intercompartmental clearances were decreased in the presence of hypothermia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Propofol blood concentration and the Bispectral Index predict suppression of learning during propofol/epidural anesthesia in volunteers.

Propofol is often used for sedation during regional anesthesia. We tested the hypothesis that propofol blood concentration, the Bispectral Index and the 95% spectral edge frequency predict suppression of learning during propofol/epidural anesthesia in volunteers. In addition, we tested the hypothesis that the Bispectral Index is linearly related to propofol blood concentration. Fourteen healthy, male volunteers were studied on three randomly ordered days: no propofol, target propofol blood concentration 1 microgram/mL, and target propofol blood concentration 2 micrograms/mL. Each day, epidural anesthesia (approximately T11 level) was induced using 2% 2-chloroprocaine. Propofol was infused by a computer-controlled pump, and propofol concentration measured in central venous blood. We administered a Trivial Pursuit-type question task on all 3 days. The electroencephalogram was monitored continuously (Fp1, Fp2; reference, Cz; ground, mastoid). Propofol caused concentration-related impairment of learning. The propofol blood concentration suppressing learning by 50% was 0.66 +/- 0.1 microgram/mL. The Bispectral Index value when learning was suppressed by 50% was 91 +/- 1. In contrast, the 95% spectral edge frequency did not correlate well with learning. The Bispectral Index decreased linearly as propofol blood concentration increased (Bispectral Index = -7.4.[propofol] + 90; r2 = 0.47, n = 278). There was no significant correlation between the 95% spectral edge frequency and propofol concentration. In order to suppress learning, propofol blood concentrations reported to produce amnesia may be targeted. Alternatively, the Bispectral Index may be used to predict anesthetic effect during propofol sedation.

Adult↗