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Biomedical subjects

C A Shanks

Publications and source records attributed to C A Shanks.

At least 19 recordsLinked to original sources
PubMed2001

Clinical delineation and localization to chromosome 9p13.3-p12 of a unique dominant disorder in four families: hereditary inclusion body myopathy, Paget disease of bone, and frontotemporal dementia.

Autosomal dominant myopathy, Paget disease of bone, and dementia constitute a unique disorder (MIM 605382). Here we describe the clinical, biochemical, radiological, and pathological characteristics of 49 affected (23 male, 26 female) individuals from four unrelated United States families. Among these affected individuals 90% have myopathy, 43% have Paget disease of bone, and 37% have premature frontotemporal dementia. EMG shows myopathic changes and muscle biopsy reveals nonspecific myopathic changes or blue-rimmed vacuoles. After candidate loci were excluded, a genome-wide screen in the large Illinois family showed linkage to chromosome 9 (maximum LOD score 3.64 with marker D9S301). Linkage analysis with a high density of chromosome 9 markers generated a maximum two-point LOD score of 9.29 for D9S1791, with a maximum multipoint LOD score of 12.24 between D9S304 and D9S1788. Subsequent evaluation of three additional families demonstrating similar clinical characteristics confirmed this locus, refined the critical region, and further delineated clinical features of this unique disorder. Hence, autosomal dominant inclusion body myopathy (HIBM), Paget disease of bone (PDB), and frontotemporal dementia (FTD) localizes to a 1.08-6.46 cM critical interval on 9p13.3-12 in the region of autosomal recessive IBM2.

Adult↗
PubMed2000

Indocyanine green kinetics characterize blood volume and flow distribution and their alteration by propranolol.

BACKGROUND AND OBJECTIVES: Although indocyanine green can be used to estimate cardiac output and blood volume independently, a recirculatory multicompartmental indocyanine green model enables description of these and additional intravascular events. Our model was used to describe the effect of propranolol on blood volume and flow distribution in humans. METHODS: Indocyanine green disposition was determined twice in four healthy adult men, once during a propranolol infusion that decreased cardiac output. After injection of indocyanine green, arterial blood was collected frequently for 2 minutes and less frequently thereafter. Plasma indocyanine green concentrations were measured by HPLC. The recirculatory pharmacokinetic model incorporates data from both the initial transient oscillations and the later post-mixing portions of the blood indocyanine green concentration versus time curves to characterize not only blood volume and cardiac output but also their distribution among a central blood volume and fast and slow peripheral volumes in lumped parallel circuits. Flow through the central circulation (cardiac output) is described by two parallel Erlang distribution functions generated by two linear chains of compartments in parallel. RESULTS: Propranolol reduced cardiac output from 10.6 to 4.1 L/min. Most of the decrease in cardiac output was at the expense of blood flow to the fast peripheral circuit, which represented nonsplanchnic circulation. Propranolol also reduced the blood volume of the fast peripheral circuit by more than half. CONCLUSION: Our indocyanine green model is able to derive estimates of blood volume and cardiac output, as well as their systemic distribution during different physiologic conditions.

Adrenergic beta-Antagonists↗
PubMed2000

Isoflurane alters the recirculatory pharmacokinetics of physiologic markers.

BACKGROUND: Earlier studies have demonstrated that physiologic marker blood concentrations in the first minutes after administration, when intravenous anesthetics exert their maximum effect, are determined by both cardiac output and its distribution. Given the reported vasodilating properties of isoflurane, we studied the effects of isoflurane anesthesia on marker disposition as another paradigm of altered cardiac output and regional blood flow distribution. METHODS: The dispositions of markers of intravascular space and blood flow (indocyanine green), extracellular space and free water diffusion (inulin), and total body water and tissue perfusion (antipyrine) were determined in four purpose-bred coonhounds. The dogs were studied while awake and while anesthetized with 1.7%, 2.6%, and 3.5% isoflurane (1.15, 1.7, and 2.3 minimum alveolar concentration, respectively) in a randomized order determined by a Latin square experimental design. Marker dispositions were described by recirculatory pharmacokinetic models based on very frequent early, and less frequent later, arterial blood samples. These models characterize the role of cardiac output and regional blood flow distribution on drug disposition. RESULTS: Isoflurane caused a significant and dose-dependent decrease in cardiac output. Antipyrine disposition was profoundly affected by isoflurane anesthesia, during which nondistributive blood flow was maintained despite decreases in cardiac output, and the balance between fast and slow tissue volumes and blood flows was altered. CONCLUSIONS: The isoflurane-induced changes in marker disposition were different than those the authors reported previously for halothane anesthesia, volume loading, or hypovolemia. These data provide further evidence that not only cardiac output but also its peripheral distribution affect early drug concentration history after rapid intravenous administration.

Anesthetics, Inhalation↗
PubMed1999

Ketamine distribution described by a recirculatory pharmacokinetic model is not stereoselective.

BACKGROUND: Differences in the pharmacokinetics of the enantiomers of ketamine have been reported. The authors sought to determine whether these differences extend to pulmonary uptake and peripheral tissue distribution and to test the hypothesis that tissue distribution of the stereoisomers differs because of carrier-mediated drug transport. METHODS: The dispositions of markers of intravascular space and blood flow (indocyanine green, ICG) and total body water and tissue perfusion (antipyrine) were determined along with S-(+)- and R-(-)-ketamine in five mongrel dogs. The dogs were studied while anesthetized with 2.0% halothane. Marker and drug dispositions were described by recirculatory pharmacokinetic models based on frequent early and less-frequent later arterial blood samples. These models characterize pulmonary uptake and the distribution of cardiac output into parallel peripheral circuits. RESULTS: Plasma elimination clearance of the S-(+)-ketamine enantiomer, 29.9 ml x min(-1) x kg(-1), was higher than that of the R-(-)-enantiomer, 22.2 ml x min(-1) x kg(-1). The apparent pulmonary tissue volumes of the ketamine S-(+) and R-(-)-enantiomers (0.31 l) did not differ and was approximately twice that of antipyrine (0.16 l). The peripheral tissue distribution volumes and clearances and the total volume of distribution (2.1 l/kg) were the same for both stereoisomers when elimination clearances were modeled from the rapidly equilibrating peripheral compartment. CONCLUSIONS: Although the elimination clearance of S-(+)-ketamine is 35% greater than that of the R-(-)-enantiomer, there is no difference in the apparent pulmonary tissue volume or peripheral tissue distribution between the stereoisomers, suggesting that physicochemical properties of ketamine other than stereoisomerism determine its perfusion-limited tissue distribution.

Algorithms↗
PubMed1999

Modifications of blood volume alter the disposition of markers of blood volume, extracellular fluid, and total body water.

Recirculatory pharmacokinetic models for indocyanine green (ICG), inulin, and antipyrine describe intravascular mixing and tissue distribution after i.v. administration. These models characterized physiologic marker disposition in four awake, splenectomized dogs while they were normovolemic, volume loaded (15% of estimated blood volume added as a starch solution), and mildly and moderately hypovolemic (15 and 30% of estimated blood volume removed). ICG-determined blood volumes increased 20% during volume loading and decreased 9 and 22% during mild and moderate hypovolemia. Dye (ICG) dilution cardiac output (CO) increased 31% during volume loading and decreased 27 and 38% during mild and moderate hypovolemia. ICG-defined central and fast peripheral intravascular circuits accommodated blood volume alterations and the fast peripheral circuit accommodated blood flow changes. Inulin-defined extracellular fluid volume contracted 14 and 21% during hypovolemia. Early inulin disposition changes reflected those of ICG. The ICG and inulin elimination clearances were unaffected by altered blood volume. Neither antipyrine-defined total body water volume nor antipyrine elimination clearance changed with altered blood volume. The fraction of CO not involved in drug distribution had a significant effect on the area under the antipyrine concentration-versus-time relationships (AUC) in the first minutes after drug administration. Hypovolemia increased the fraction of CO represented by nondistributive blood flow and increased the antipyrine AUC up to 60% because nondistributive blood flow did not change, despite decreased CO. Volume loading resulted in a smaller (less than 20%) antipyrine AUC decrease despite increased fast tissue distributive flow because nondistributive flow also increased with increased CO.

Animals↗
PubMed1997

The train-of-four count and kinetic-dynamic modelling.

The intraoperative monitoring of neuromuscular blockade usually involves measurement of the muscular responses to motor nerve stimulation. Although researchers have the time and technology to obtain predrug control measurements of the twitch responses, these are seldom available to the clinician. During surgically useful relaxation, there is progressive inhibition of responses to train-of-four (TOF) stimulation in the presence of a nondepolarizing relaxant, and the clinician can count the number of responses to predict the likely time-course of paralysis. At the extremes, a count of four (of four) responses may indicate a need for further relaxant, whereas with profound paralysis, the absence of responses may suggest that reversal with an anticholinesterase may be ineffective. Concentrations in the effect compartment associated with these two extremes of the TOF count are combined with concentration-time profiles of vecuronium with various dose regimens. This study models the effect compartment concentrations associated with vecuronium-induced paralysis, combining them explicitly with the range of concentrations associated with the TOF count to demonstrate the kinetic mechanisms underlying the time-course of paralysis.

Computer Simulation↗
PubMed1997

Dose-ranging study in younger adult and elderly patients of ORG 9487, a new, rapid-onset, short-duration muscle relaxant.

The purpose of this multicenter, randomized, assessorblind placebo-controlled study was to determine which of five doses of the new, rapid-onset neuromuscular relaxant, ORG 9487, provided both good to excellent tracheal intubating conditions 60 s after administration and a clinical duration of action < 20 min in 120 younger (aged 18-64 yr) and 61 elderly (aged 65-85 yr) adult patients. Anesthesia was induced with fentanyl (2-5 micrograms/kg) and thiopental (3-6 mg/kg) and maintained with N2O/O2 and a propofol infusion (50-300 micrograms.kg-1.min-1). Neuromuscular train-of-four (TOF) monitoring by electromyography (Datex Relaxograph) commenced immediately after anesthetic induction and was followed, within 30 s, by one of five doses of ORG 9487 (0.5, 1.0, 1.5, 2.0, 2.5 mg/kg) or a placebo. Tracheal intubation was attempted at 60 s and again, in the case of failure, at 90 s. Conditions were assessed with a 4-point scale. Maximum block, clinical duration (time to 25% T1 recovery), and recovery (TOF > or = 0.7) were measured. Dose-dependent changes were observed in tracheal intubating conditions and neuromuscular block. Good to excellent intubating conditions at 60 s were present in most younger adult (52 of 60) and elderly (26 of 31) patients administered doses > or = 1.5 mg/kg. Mean clinical durations < 20 min were observed in adult patients at doses up to 2.0 mg/kg and in geriatric patients up to 1.5 mg/kg. Thus, doses of 1.5-2.0 mg/kg ORG 9487 enabled both rapid tracheal intubation and a short clinical duration of action in adult and elderly patients.

Adolescent↗
PubMed1997

The effect of halothane on the recirculatory pharmacokinetics of physiologic markers.

BACKGROUND: The cardiovascular effects of halothane are well recognized, but little is known of how this affects drug distribution. The effect of halothane anesthesia on physiologic factors that affect drug disposition from the moment of injection was investigated. METHODS: The dispositions of markers of intravascular space and blood flow (indocyanine green), extracellular space and free water diffusion (inulin), and total body water and tissue perfusion (antipyrine) were determined in four purpose-bred coonhounds. The dogs were studied while awake and while anesthetized with 1%, 1.5%, and 2% halothane in a randomized order determined by a repeated measures Latin square experimental design. Marker dispositions were described by recirculatory pharmacokinetic models based on frequent early and less frequent later arterial blood samples. These models characterize the role of cardiac output and its distribution on drug disposition. RESULTS: Halothane caused a significant and dose-dependent decrease in cardiac output. The disposition of antipyrine was most profoundly affected by halothane anesthesia, which increased both nondistributive intercompartmental clearance and volume while decreasing fast and slow tissue clearances and elimination clearance in a halothane dose-dependent manner. CONCLUSIONS: Halothane-induced changes in blood flow to the compartments of the antipyrine recirculatory model were not proportional to changes in cardiac output. Halothane anesthesia significantly increased (to more than double) the area under the drug concentration versus time curve due to an increase in the apparent peripheral blood flow not involved in drug distribution, despite a dose-dependent cardiac output decrease. Recirculatory pharmacokinetic models include the best aspects of traditional compartmental and physiologic pharmacokinetic models while offering advantages over both.

Anesthesia, Inhalation↗
PubMed1996

Use of parallel Erlang density functions to analyze first-pass pulmonary uptake of multiple indicators in dogs.

The gamma and Erlang density functions describe a large class of lagged, right-skewed distributions. The Erlang distribution has been shown to be the analytic solution for a chain of compartments with identical rate constants. This relationship makes it useful for the analysis of first-pass pulmonary drug uptake data following intravenous bolus administration and the incorporation of this analysis into an overall systemic drug disposition model. However, others have shown that one Erlang density function characterizes the residence time distribution of solutes in single tissues with significant systematic error. We propose a model of two Erlang density functions in parallel that does characterize well the arterial appearance of indocyanine green, antipyrine, and alfentanil administered simultaneously by right atrial bolus injection. We derive the equations that permit calculation of the higher order moments of a system consisting of two parallel Erlang density functions and use the results of these calculations from the data for all three indicators to estimate pulmonary capillary blood volume and mean transit time in the dog.

Alfentanil↗
PubMed1996

Recirculatory pharmacokinetic models of markers of blood, extracellular fluid and total body water administered concomitantly.

Pharmacokinetic models were developed to describe the disposition of markers of extracellular fluid (inulin) and total body water (antipyrine) from the moment of injection to incorporate the intravascular mixing component, determined by a marker of intravascular space (indocyanine green, ICG). The simultaneous dispositions of these markers were characterized in four halothane-anesthetized dogs. After injection of ICG, [14C]-inulin, and antipyrine into the right atrium, femoral arterial blood samples were collected every 3 sec for 1 min and less frequently to 20 min for ICG and to 360 min for inulin and antipyrine. ICG and antipyrine concentrations were measured by high-performance liquid chromatography and [14C]-inulin concentrations were measured by liquid scintillation counting. The marker concentration histories were characterized completely by fully identifiable recirculatory compartmental models. Because neither ICG nor inulin distribute beyond intravascular space before recirculation, their first-pass data were modelled simultaneously to improve confidence in central circulation model parameters. This central circulation model included an estimate of cardiac output that was retained in the recirculatory models of all markers. Three tissue compartments were identified for antipyrine, a lipid soluble marker that equilibrates with tissue (including the lung) and estimates total body water and tissue blood flow. The hydrophilic marker, inulin, diffuses into interstitial fluid so slowly that only two extravascular compartments were identified. These models may be used to determine how cardiac output and its distribution, pulmonary drug uptake, and nondistributive blood flow contribute to variability in patient response to drugs with a rapid onset of effect.

Animals↗
PubMed1995

Calculation of an effect compartment rate constant using recovery indices obtained with an isolated arm technique.

We have examined the implications of the theoretical single pharmacokinetic compartment associated with blocker-induced paralysis, in relation to the isolated arm technique. It is assumed that the blocker concentration-effect relationship can be characterized by a sigmoid curve, which incorporates an exponent, s. After tourniquet release, the concentration gradient between the effect compartment and plasma should be large, and elimination related to the rate constant, keo. The major measurement of spontaneous recovery with the isolated arm is the time interval between 75% and 25% twitch depression, T25-T75. The general equation relating these three variables is developed: keo = 2.2/(s x (T25-T75)). Insertion of published values for T25-T75 with isolated arm studies into this equation gave estimates for an intrinsic keo for atracurium, vecuronium, rocuronium and pancuronium.

Androstanols↗
PubMed1994

Effect of infusion rate on thiopental dose-response relationships. Assessment of a pharmacokinetic-pharmacodynamic model.

BACKGROUND: The rate of administration of an intravenous anesthetic induction agent is an important variable determining the total dose required to reach a given endpoint, such as loss of consciousness (LOC). The influence of infusion rate on the dose-response relationship has not been described rigorously. In this study we characterized the effect of different thiopental infusion rates on the times and doses required to reach a clinical (induction) endpoint. METHODS: Fifty-six healthy, non-premedicated men, aged 19-59 yr, were randomly assigned to receive one of seven different thiopental infusion rates (40, 60, 75, 150, 300, 600, and 1,200 mg/min). The infusion was continued until the patient dropped a held object, indicating LOC. The infusion rates were selected using a simulation which predicted the relationship between the rate of administration and cumulative dose administered at the time of LOC. Average population pharmacokinetic parameters from a three-compartment thiopental model were combined with an effect-site rate constant for thiopental equilibration of 0.58 min-1 and a median effect-site concentration of 13.8 mg/l from previously published pharmacokinetic and pharmacodynamic models for thiopental. This derived model was used to predict the total amount of thiopental required, at each infusion rate, to produce LOC. RESULTS: The observed median effective doses for infusion rates of 40-150 mg/min were similar and ranged from 296 to 318 mg. Dose requirements increased significantly with increasing infusion rates greater than 150 mg/min; median effective doses for infusion rates of 300, 600, and 1,200 mg/min were significantly different from each other (436, 555, and 711 mg, respectively). The original simulation underestimated the observed thiopental doses at all but the lowest infusion rate. A new simulation was performed using a recently developed combined pharmacokinetic-pharmacodynamic model. This model incorporated a four-compartment thiopental pharmacokinetic model with quantal dose-response data to derive an effect-site rate constant for thiopental equilibration of 0.29 min-1 and a median effect-site concentration for LOC of 11.3 mg/l. The median thiopental doses predicted by this new simulation under the extreme conditions of a 30-fold range of infusion rates were within 13% of the observed doses. CONCLUSIONS: In this study we quantified the relationship between the rate of thiopental administration and the resultant cumulative thiopental dose necessary to produce LOC. This study validated a novel pharmacokinetic-pharmacodynamic model based on a four-compartment pharmacokinetic model and infusion quantal dose-response data. Finally, we demonstrated that thiopental dose-response relationships are dependent on drug administration rate, and found that the ability to predict this dependence accurately is influenced by the pharmacokinetics, pharmacodynamics, and median effect-site concentration used to simulate the dose-response relationships.

Adult↗
PubMed1994

A recirculatory pharmacokinetic model describing the circulatory mixing, tissue distribution and elimination of antipyrine in dogs.

A model of antipyrine disposition from the moment of its injection was developed incorporating the intravascular mixing component as determined by indocyanine green (ICG) kinetics. The simultaneous dispositions of antipyrine and ICG were characterized in five dogs anesthetized with halothane. After injecting antipyrine and ICG into the right atrium, femoral arterial blood samples were collected every 3 sec for the 1st min and less frequently to 20 min for ICG and to 360 min for antipyrine. ICG and antipyrine concentrations were measured by high-performance liquid chromatography and modeled with SAAM 30.1. A fully identifiable recirculatory compartmental model, incorporating the ICG recirculatory model with blood flows and time delays, was used to describe antipyrine disposition. Four distinct antipyrine pharmacokinetic tissue compartments and the distribution clearances assigned to them could be estimated: a pulmonary tissue (0.13 +/- 0.05 I, and 2.51 +/- 0.39 liters/min), a very fast equilibrating tissue (0.12 +/- 0.08 I, and 1.33 +/- 0.22 liters/min), a fast equilibrating tissue (3.21 +/- 0.45 I, and 0.74 +/- 0.09 liters/min) and a slow equilibrating tissue (15.94 +/- 1.8 I, and 0.44 +/- 0.13 liters/min). Although this recirculatory model retains the predominant attributes of traditional pharmacokinetic models, it also can describe completely drug concentrations during the mixing transient when many drugs reach peak effect as well as ascertain the role of cardiac output and its distribution in drug disposition.

Animals↗
PubMed1993

A pharmacokinetic-pharmacodynamic model for quantal responses with thiopental.

The pharmacokinetic-pharmacodynamic model developed here characterizes the relationship between simulated plasma concentrations of thiopental and two dichotomous endpoints determined at induction of anesthesia: loss of voluntary motor power (clinical endpoint), and burst suppression of the electroencephalogram (EEG endpoint). The model incorporated data from two separate thiopental patient studies: a pharmacokinetic study with 21 males, and a pharmacodynamic study with 30 males. In the pharmacodynamic study, cumulative quantal dose-response curves for the clinical and EEG endpoints were developed from observations made during a constant-rate infusion of thiopental. Population mean parameters, derived from the bolus pharmacokinetic thiopental study, were used to simulate concentration-time data for the 150 mg.min-1 thiopental infusion rate used in the dose-response study. A single biophase model incorporating the two endpoints was generated, combining the pharmacokinetic and pharmacodynamic data from the two groups. Estimates of the mean effective thiopental concentrations affecting 50% of the population (EC50S) for the clinical and EEG endpoints were 11.3 and 33.9 micrograms.ml-1, respectively. The half-time for equilibration between arterial thiopental and the effect compartment was 2.6 min. These results are in reasonable agreement with previously described quantal concentration-response data, and with pharmacodynamic models developed for graded EEG responses. Simulation of bolus doses of thiopental with the new model provided ED50s for the clinical and EEG endpoints of 265 mg and 796 mg, respectively; the dose predicted to produce loss of voluntary motor power in 90% of an adult male population was 403 mg. A model combining population pharmacokinetics with cumulative dose-response relationships could prove useful in predicting dosage regimens for those drugs with responses that are categorical.

Adolescent↗
PubMed1993

Continuous intravenous infusion of rocuronium (ORG 9426) in patients receiving balanced, enflurane, or isoflurane anesthesia.

BACKGROUND: Rocuronium (ORG 9426) is a new nondepolarizing neuromuscular blocking agent with a rapid onset and an intermediate duration of action. This study obtains the infusion requirements of rocuronium in 30 patients in whom anesthesia was maintained with barbiturate-nitrous oxide-opioid, nitrous oxide and enflurane, or nitrous oxide and isoflurane. METHODS: For all 30 patients, anesthesia was induced with intravenous thiopental and fentanyl, followed by 0.45 mg/kg rocuronium. Patients were randomly allocated to receive either: 1) nitrous oxide in 40% oxygen supplemented with fentanyl, thiopental, and droperidol (balanced anesthesia), 2) 1.25 MAC enflurane-nitrous oxide, or 3) 1.25 MAC isoflurane-nitrous oxide. Once blockade had recovered to 95% depression of twitch height, muscle relaxation was maintained by continuous infusion of rocuronium, adjusted to maintain mechanical twitch response at 95% depression. RESULTS: At 90 and 120 min, the enflurane and isoflurane groups had lower infusion requirements than those receiving barbiturate-nitrous oxide-opioid anesthesia (P < 0.02), but these did not differ significantly between the two volatile agents. Final infusion requirements (mean +/- SD) were 9.8 +/- 3.7, 5.9 +/- 3.1, and 6.1 +/- 2.7 micrograms.kg-1.min-1 for the groups receiving barbiturate-nitrous oxide-opioid, enflurane, and isoflurane anesthesia, respectively. Spontaneous recovery began soon after termination of the infusion; in all patients, twitch tension equaled 10% of control within 5 min. CONCLUSIONS: The infusion requirements to maintain 95% twitch depression approximated 10 micrograms.kg-1.min-1 during barbiturate-nitrous oxide-opioid anesthesia. These requirements were reduced by 40% during anesthesia involving enflurane or isoflurane.

Adult↗
PubMed1993

Determinants of thiopental induction dose requirements.

Dose requirements for thiopental anesthetic induction have significant age- and gender-related variability. We studied the association of the patient characteristics age, gender, weight, lean body mass, and cardiac output with thiopental requirements. Doses of thiopental, infused at 150 mg/min, required to reach both a clinical end-point and an electroencephalographic (EEG) end-point were determined in 30 males and 30 females, aged 18-83 yr. Univariate least squares linear regression analysis revealed outliers in the relationships of age, weight, lean body mass, and cardiac output to thiopental dose at clinical and EEG endpoints. Differential weighting of data points minimized the effect of outliers in the construction of a robust multiple linear regression model of the relationship between several selected independent variables and the dependent variables thiopental dose at clinical and EEG endpoints. The multiple linear regression model for thiopental dose at the clinical end-point selecting the regressor variables age, weight, and gender (R2 = 0.76) was similar to that for age, lean body mass, and gender (R2 = 0.75). Thiopental dose at the EEG endpoint was better described by models selecting the variables age, weight, and cardiac output (R2 = 0.88) or age, lean body mass, and cardiac output (R2 = 0.87). Although cardiac output varied with age, age always remained a selected variable. Because weight and lean body mass differed with gender, their selection as variables in the model eliminated gender as a selected variable or minimized its importance.

Adult↗
PubMed1993

Reevaluation of a maneuver to visualize the anterior larynx after intubation.

Confirmation of translaryngeal placement of the tracheal tube can be unexpectedly difficult. This study examined the usefulness of displacing the larynx posteriorly with the tracheal tube during laryngoscopy with a straight laryngoscope blade to confirm tracheal tube placement. One hundred ASA Classes I, II, or III patients presenting for elective surgery whose normal anesthetic care included placement of an orotracheal tube via direct laryngoscopy were enrolled in this institutionally approved study after giving their written, informed consent. The view of the larynx at laryngoscopy was graded, and the tracheal tube was then inserted. When the larynx was incompletely exposed, the tracheal tube was displaced posteriorly while the laryngoscope was maintained in the intubating position in an attempt to better visualize the larynx. The effect of the maneuver on Mallampati grade for laryngeal exposure was noted. During laryngoscopy with a Miller blade none of the glottis was initially visualized in 17 patients (Mallampati laryngeal Grades 3 and 4). Thus, the tracheal tube actually was not seen to pass between these patients' vocal cords. Use of the maneuver resulted in improved visualization of the intubated larynx in 12 of these patients, and confirmed tracheal intubation. This maneuver is recommended as an aid to the anesthesiologist in the confirmation of tracheal intubation.

Adult↗