Radiological comparison of a FDNPP waste storage site during and after construction

The clean-up effort that is occurring across the region affected by the 2011 Fukushima Daiichi Nuclear Power Plant accident is unprecedented in its magnitude as well as the financial cost that will eventually result. A major component of this remediation is the stripping of large volumes of material from the land surface, depositing this into large waste storage bags before placing these 1 cubic meter bags into specially constructed stores across Fukushima Prefecture. In this work, using an unmanned aerial vehicle to perform radiological surveys of a site, the time-resolved distribution of contamination during the construction of one of these waste storage sites was assessed. The results indicated that radioactive material was progressively leaching from the store into the surrounding environment. A subsequent survey of the site conducted eight months later revealed that in response to this survey and remedial actions, the contamination issue once existing on this site had been successfully resolved. Such results highlight the potential of low-altitude unmanned aerial systems to easily and rapidly assess site-wide changes over time - providing highly-visual results; therefore, permitting for prompt remedial actions to be undertaken as required. Use of UAV radiation mapping and airborne photogrammetry to produce a time-resolved assessment of remediation efforts within a Fukushima temporary storage facility.

Application of airborne photogrammetry for the visualisation and assessment of contamination migration arising from a Fukushima waste storage facility

Airborne systems such as lightweight and highly portable unmanned aerial vehicles (UAVs) are becoming increasingly widespread in both academia and industry - with an ever-increasing range of applications, including (but not limited to), air quality sampling, wildlife monitoring and land-use mapping. In this work, high-resolution airborne photogrammetry obtained using a multi-rotor system operating at low survey altitudes, is combined with ground-based radiation mapping data acquired at an interim storage facility for wastes removed as part of the large-scale Fukushima clean-up program. The investigation aimed to assess the extent to which the remediation program at a specific site has contained the stored contaminants, as well as present a new methodology for rapidly surveying radiological sites globally. From the three-dimensional rendering of the site of interest, it was possible to not only generate a powerful graphic confirming the elevated radiological intensity existing at the location of the waste bags, but also to also illustrate the downslope movement of contamination due to species leakage from the large 1m³ storage bags. The entire survey took less than 1 h to perform, and was subsequently post-processed using graphical information software to obtain the renderings. The conclusions within this study not only highlight the usefulness of incorporating three-dimensional renderings within radiation mapping protocols, but also conclude that current methods of monitoring these storage facilities in the long term could be improved through the integration of UAVs within the standard protocol.

A comparison of cardiac output derived from the arterial pressure wave against thermodilution in cardiac surgery patients

In three clinical centres, we compared a new method for measuring cardiac output with conventional thermodilution. The new method computes beat-to-beat cardiac output from radial artery pressure by simulating a three-element model of aortic input impedance, and includes non-linear aortic mechanical properties and a self-adapting systemic vascular resistance. We compared cardiac output by continuous model simulation (MF) with thermodilution cardiac output (TD) in 54 patients (18 female, 36 male) undergoing coronary artery bypass surgery. We made three or four conventional thermodilution estimates spread equally over the ventilatory cycle. In 490 series of measurements, thermodilution cardiac output ranged from 2.1 to 9.3, mean 5.0 litre min(-1). MF differed +0.32 (1.0) litre min(-1) on average with limits of agreement of -1.68 and +2.32 litre min(-1). Differences decreased when the first series of measurements in a patient was used to calibrate the model. In 436 remaining series, the mean difference became -0.13 (0.47) litre min(-1) with limits of agreement of -1.05 and +0.79 litre min(-1). When consecutive measurements were made, the change was greater than 0.5 litre min(-1), on 204 occasions. The direction of change was the same with both methods in 199. The difference between the methods remained near zero during surgery suggesting that a single calibration per patient was adequate. Aortic model simulation with radial artery pressure as input reliably monitors changes in cardiac output in cardiac surgery patients. Before calibration, the model cannot replace thermodilution, but after calibration the model method can quantitatively replace further thermodilution estimates.

Brain metastasis from a primary liposarcoma of the digit: case report

Soft-tissue sarcomas of the digit are uncommon. We herein report on a patient with a de-novo subungual right thumb liposarcoma with subsequent failure in the brain. The pertinent literature and recommendations for management are presented.

Simulation in anesthesia: the merits of large simulators versus small simulators

Anesthesia simulation is generally perceived as involving large simulators that provide a limited number of operating room scenarios, especially crisis management. The scope of both anesthesia and flight simulation is much wider, and this review summarizes the range of the former. The areas where simulation has been used include training, education and science. The diversity of its uses may surprise the reader. The models that are used in simulations are important, and these are discussed in part of the discussion. As a result of the current imbalance in perception, I emphasize the merits of small simulators at the expense of large simulators.

Craniofacial electromyogram activation response: another indicator of anesthetic depth

OBJECTIVE

After finding that craniofacial EMG preceding a stimulus was a poor predictor of movement response to that stimulus, we evaluated an alternative relation between EMG and movement: the difference in anesthetic depth between the endpoint of EMG responsiveness to a stimulus and endpoint of movement responsiveness to that stimulus. We expressed this relation as the increment of isoflurane between the two endpoints.

METHODS

We measured EMG over the frontalis muscle, over the corrugator muscle, and between the Fp2 and the mastoid process as patients emerged from general anesthesia during suture closing of the surgical incision. Anesthesia was decreased by controlled washout of isoflurane while maintaining 70% N2O, and brain isoflurane concentrations ((C)isoBrain) were calculated. We studied a control group of 10 patients who received only surgical stimulation, and 30 experimental patients who intermittently received test stimuli in addition to the surgical stimulation. Patients were observed for movement responses and EMG records were evaluated for EMG activation responses. We defined an EMG activation response to be a rapid voltage increase of at least 1.0 microV RMS above baseline, with a duration of at least 30 s, in at least one of the three EMG channels. Patient responses to stimuli were classified as either an EMG activation response without a move response (EMG+), a move response without an EMG activation response (MV+), both an EMG activation response and a move response (EMG+MV+), or no response. We defined the EMG+ endpoint to be the threshold between EMG+ response and nonresponse to a stimulus, and estimated (C)isoBrain at this endpoint. We similarly defined the move endpoint and estimated the move endpoint (C)isoBrain. We then calculated the increment of (C)isoBrain at the EMG+ endpoint relative to the move endpoint.

MAIN RESULTS

For the 30 experimental patients, the initial response to a test stimulus was an EMG+ in 14 patients (47%), an EMG+MV+ in 12 patients (40%), and a MV+ in 1 patient (3%); no response occurred by the time surgery was completed in 3 patients (10%). No response occurred in 7 of the control patients (70%). Of the 14 patients with an initial EMG+ response to a test stimulus, 9 patients later had a move response. For these 9 patients, the increment of (C)isoBrain between the EMG+ endpoint and move endpoint was 0.11 +/- 0.04 vol%, (mean +/- SD).

CONCLUSIONS

Our results suggest that, given the circumstances of our study, an EMG activation response by a nonmoving patient indicates that the patient is at an anesthetic level close to that at which movement could occur. However, because the first EMG activation response may occur simultaneously with movement, the EMG activation response cannot be relied upon to always herald a move response before it occurs. Our results also suggest that EMG responsiveness to a test stimulus may be used to estimate the anesthetic depth of an individual patient.

Virtual medical trainer. Patient assessment and trauma care simulator

The Virtual Medical Trainer (VMET) combines multimedia sound and graphics with physiological engines, medical-procedures databases, and 3-D patients to produce an interactive environment that can mimic the cognitive pre-hospital assessment and care demands of a real emergency. VMET uses a reconfigurable component software and training framework that allows a uniform user interface, ease of increasing training complexity, and expansion of the software components. VMET provides an opportunity to experience a range of trauma scenarios prior to the challenge of an actual trauma situation.

A multicenter study of bispectral electroencephalogram analysis for monitoring anesthetic effect

Bispectral analysis (BIS) of the electroencephalogram (EEG) has been shown in retrospective studies to predict whether patients will move in response to skin incision. This prospective multicenter study was designed to evaluate the real-time utility of BIS in predicting movement response to skin incision using a variety of general anesthetic techniques. Three hundred patients from seven study sites received an anesthetic regimen expected to give an approximately 50% movement response at skin incision. EEG was continuously recorded via an Aspect B-500 monitor and BIS was calculated in real time from bilateral frontocentral channels displayed on the monitor. Half of the patients were randomized to a treatment group in which anesthetic drug doses were increased to produce a lower BIS. In the control group, BIS was recorded, but no action taken on the data displayed. A determination of movement in response to skin incision was made in the 2 min succeeding incision. Retrospective pharmacodynamic modeling was performed using STANPUMP to estimate effect-site concentrations of intravenously administered anesthetics. BIS values were significantly higher in the control group (66 +/- 19) versus the BIS-guided group, in which additional anesthesia was administered to produce a lower BIS (51 +/- 19). The movement response rate was significantly higher in the control group at 43% compared with 13% in the BIS-guided group, but response rates were low at sites which used larger doses of opioids. Logistic regression analysis showed that BIS, estimated opioid effect-site concentrations, and heart rate (in that order) were the best predictors of movement at skin incision. This study demonstrates that dosing anesthetic drugs to lower BIS values achieves a lower probability of movement in response to surgical stimulation. BIS is a significant predictor of patient response to incision, but the utility of the BIS depends on the anesthetic technique being used. When drugs such as propofol or isoflurane are used as the primary anesthetic, changes in BIS correlate with the probability of response to skin incision. When opioid analgesics are used, the correlation to patient movement becomes much less significant, so that patients with apparently "light" EEG profiles may not move or otherwise respond to incision. Therefore, the adjunctive use of opioid analgesics confounds the use of BIS as a measure of anesthetic adequacy when movement response to skin incision is used as the primary end point.

A measure of association for assessing prediction accuracy that is a generalization of non-parametric ROC area

There is a need for a measure of prediction accuracy that generalizes non-parametric receiver operating characteristic (ROC) area to polytomous ordinal patient state. We describe such a measure, prediction probability PK derived from Kim's measure of association. We show that the value of PK equals the value of non-parametric ROC area for dichotomous patient state and is a meaningful generalization of non-parametric ROC area for polytomous state.

EEG Predicts movement response to surgical stimuli during general anesthesia with combinations of isoflurane, 70% N2O, and fentanyl

OBJECTIVE

Our objective was to evaluate the performance of the EEG as an indicator of anesthetic depth by measuring EEG prediction of movement response to surgical stimuli.

METHODS

While using 5 different combinations of isoflurane, 70% N2O, and fentanyl, we measured the EEG of 246 patients during pelvic laparoscopy and observed their movement responses to opening stimuli (defined as skin incision, CO2 needle insertion, or trocar insertion) and also to closing stimuli (defined as sutures during incision closure). The EEG was expressed as F95, the frequency in hertz below which resides 95% of the power in the EEG frequency spectrum. The relations between F95 and movement response were expressed as logistic regression curves. F95-response logistic regression curves, which are analogous to dose-response curves, were calculated for each of the 2 stimuli administered during each of the 5 anesthetic techniques. The prediction of patient responsiveness by F95 was tested using beta (beta), a measure of the slope of an F95-response logistic curve. The presence of shifts among the F95-response logistic curves was tested using the differences in F95 values between curves. Hypothesis tests used a level of significance of P = 0.05.

MAIN RESULTS

The slopes of the F95-response logistic regression curves showed a statistically significant ability to predict movement response to stimuli for 9 of the 10 combinations of stimuli and anesthetic techniques. We did not calculate an F95-response logistic curve for the tenth combination because it contained burst suppression, which our EEG analysis method was not designed to process. The F95-response logistic curves were shifted relative to each other, and the shifts were affected by the type of stimulus and the combination of anesthetic agents. Referenced to opening curves, the mean shift of the closing curves was +4.2 +/- 0.3 Hz (mean +/- SD). With increasing doses of fentanyl, the use of 70% N2O, or both, the curves shifted to higher values of F95; the range in shifts was 0.2 to 8.1 Hz. The slope beta values of the F95-response logistic curves and the shifts among the curves were similar to the beta values and shifts that might be expected from changes in anesthetic agent doses.

CONCLUSIONS

The EEG, expressed as F95, predicted movement response to surgical stimuli during combinations of isoflurane, 70% N2O, and fentanyl. The F95-response curves shifted upward on the frequency scale for the less intense stimuli and for anesthetic techniques using 70% N2O, fentanyl, or both. F95 prediction of movement response appeared to be related to anesthetic agent doses. Our F95-response curves may provide helpful guidelines for using F95 to titrate the administration of anesthetic agents and for assessing the depth of general anesthesia.

Measuring the performance of anesthetic depth indicators

BACKGROUND

An appropriate measure of performance is needed to identify anesthetic depth indicators that are promising for use in clinical monitoring. To avoid misleading results, the measure must take into account both desired indicator performance and the nature of available performance data. Ideally, anesthetic depth indicator value should correlate perfectly with anesthetic depth along a lighter-deeper anesthesia continuum. Experimentally, however, a candidate anesthetic depth indicator is judged against a "gold standard" indicator that provides only quantal observations of anesthetic depth. The standard anesthetic depth indicator is the patient's response to a specified stimulus. The resulting observed anesthetic depth scale may consist only of patient "response" versus "no response," or it may have multiple levels. The measurement scales for both the candidate anesthetic depth indicator and observed anesthetic depth are no more than ordinal; that is, only the relative rankings of values on these scales are meaningful.

METHODS

Criteria were established for a measure of anesthetic depth indicator performance and the performance measure that best met these criteria was found.

RESULTS

The performance measure recommended by the authors is prediction probability PK, a rescaled variant of Kim's dy.x measure of association. This performance measure shows the correlation between anesthetic depth indicator value and observed anesthetic depth, taking into account both desired performance and the limitations of the data. Prediction probability has a value of 1 when the indicator predicts observed anesthetic depth perfectly, and a value of 0.5 when the indicator predicts no better than a 50:50 chance. Prediction probability avoids the shortcomings of other measures. For example, as a nonparametric measure, PK is independent of scale units and does not require knowledge of underlying distributions or efforts to linearize or to otherwise transform scales. Furthermore, PK can be computed for any degree of coarseness or fineness of the scales for anesthetic depth indicator value and observed anesthetic depth; thus, PK fully uses the available data without imposing additional arbitrary constraints, such as the dichotomization of either scale. And finally, PK can be used to perform both grouped- and paired-data statistical comparisons of anesthetic depth indicator performance. Data for comparing depth indicators, however, must be gathered via the same response-to-stimulus test procedure and over the same distribution of anesthetic depths.

CONCLUSIONS

Prediction probability PK is an appropriate measure for evaluating and comparing the performance of anesthetic depth indicators.

A role for CNS alpha-2 adrenergic receptors in opiate-induced muscle rigidity in the rat

A number of potential neurochemical mediators of opiate-induced muscle rigidity have been proposed based on the results of systemic drug studies and on knowledge of the brain sites implicated in opiate rigidity. The effects of i.c.v. pretreatment with selected opioidergic, alpha adrenergic and serotonergic drugs on muscle rigidity induced with systemic injection of the potent opiate agonist alfentanil (ALF) were investigated in spontaneously ventilating rats. The opiate antagonist methylnaloxonium (MN; 0.2-14 nmol), alpha-2 adrenergic agonists dexmedetomidine (DEX; 0.4-42 nmol) or 2-(2,6-diethylphenylamino)-2-imidazoline hydrochloride (ST91; 4-400 nmol), alpha-1 adrenergic antagonist prazosin (PRZ; 7-70 nmol) or serotonergic antagonist ketanserin (KET; 18-550 nmol) were injected i.c.v. (10 microliters) and ALF (500 micrograms/kg s.c.) was administered 10 min later. S.c. electrodes were used to record gastrocnemius electromyographic activity. Both MN and DEX dose-dependently and potently antagonized ALF-induced rigidity. ST91 produced shorter-lived, less profound, antagonism of ALF rigidity. PRZ, at the highest dose tested, produced a delayed and modest reduction in ALF rigidity. A large, non-selective, dose of KET incompletely attenuated ALF rigidity. These results lend support to the hypothesis that central opioid and alpha-2 adrenergic receptors mediate opiate-induced muscle rigidity in the rat.

Brief wakeful response to command indicates wakefulness with suppression of memory formation during surgical anesthesia

OBJECTIVE

In a previous study of patients emerging from anesthesia following surgery, we found that a brief wakeful response to command of an eye opening or single hand squeeze or count was not associated with memory formation, while the response of four hand squeezes or counts was associated with memory. We wanted to determine the anesthetic requirements for obtaining this brief wakeful response endpoint during surgery and to determine if memory occurred at this endpoint during surgical anesthesia.

METHODS

Six different combinations of isoflurane, 70% N2O, and fentanyl were administered to 326 patients undergoing pelvic laparoscopy. After insertion of the trocar, anesthesia was reduced while patients were given verbal commands, and they were observed for movement responses to surgery and to command. Patients were classified as either not arousing, arousing with a movement response to surgery, or arousing with a wakeful response to command. For the patients who aroused, we calculated the percentage of arousal responses that were wakeful responses to command. The effect of fentanyl dosage upon the percentage of arousal responses that were wakeful responses to command was determined by using a Mann-Whitney test to compare a group of patients receiving fentanyl 2 micrograms/kg or less, with a group receiving fentanyl 4 micrograms/kg. In a subset of 39 patients, the potential for memory formation was evaluated by presenting a target sound to 29 patients during a period of either no arousal, movement response to surgery, or wakeful response to command; for a control group of 10 patients, no target sound was presented. All 39 patients were tested for memory of the target sound; the results from each group receiving a target sound were compared with the results of the control group, using a Mann-Whitney test.

MAIN RESULTS

A total of 68 patients aroused with either a movement response or a wakeful response to command. Wakeful responses occurred with only 1 of 39 patients (3%) receiving fentanyl 2 micrograms/kg or less; but, wakeful responses occurred with 17 of 29 patients (59%) receiving fentanyl 4 micrograms/kg. The difference between the groups was significant at p = 0.01. None of the 68 patients had recall of intraoperative events or unpleasant dreams. None of these patients who were in the multiple-choice memory subset recalled the target sound. There were no statistically significant differences on the multiple-choice memory test between the groups presented with the target sound and the control group. Patient anecdotes suggested that some patients may have had memory of the target sound; but, memory was no more likely in patients with a brief wakeful response to command than in those who responded with a movement to surgical stimulation or those who did not have an arousal response.

CONCLUSIONS

A brief wakeful response to a command of opening the eyes or squeezing the hand was not associated with increased memory formation during surgery. A brief wakeful response to command was found during surgery when patients received fentanyl 4 micrograms/kg; but it was rarely found at fentanyl dosages of 2 micrograms/kg or less.

Wakeful response to command indicates memory potential during emergence from general anesthesia

OBJECTIVE

An important aspect of assessing anesthetic depth is determining whether a patient will remember events during surgery. We looked for a clinical sign that would indicate a patient's potential for memory formation during emergence from anesthesia. A clinical sign indicating memory potential could be a useful endpoint for measuring the performance of anesthetic depth monitors and for titrating administration of anesthetic agents.

METHODS

We evaluated patients' responses to commands to open the eyes, squeeze the hand four times, and count 20 numbers. These responses were correlated with results on recall, cued recall, and multiple-choice memory tests.

MAIN RESULTS

Patients did not have evidence of memory formation until they sustained wakefulness sufficiently long to complete at least four hand squeezes or count four numbers. Of 28 patients, 13 (46%) with this sustained wakeful response had memory. Of 22 patients, 0 (0%) had evidence of memory formation when they demonstrated a brief wakeful response, defined as being responsive to command but unable to complete more than one hand squeeze or count, or an intermediate response, defined as two or three hand squeezes or counts.

CONCLUSIONS

We conclude that a brief wakeful response to command indicates that a patient is unlikely to form memories, while a sustained wakeful response indicates that a patient may form memories. Thus, a patient's wakeful response to command could be a useful indicator of potential for memory.

Pretreatment with sedative-hypnotics, but not with nondepolarizing muscle relaxants, attenuates alfentanil-induced muscle rigidity

STUDY OBJECTIVE

To evaluate and compare the efficacy of various pretreatment agents to attenuate or prevent opioid-induced muscle rigidity using a well-established, previously described clinical protocol.

DESIGN

Prospective, controlled, single-blind, partially randomized study.

SETTING

Large medical center.

PATIENTS

ASA physical status I-III patients undergoing elective surgical procedures of at least 3 hours' duration.

INTERVENTIONS

The effect of pretreatment with nondepolarizing muscle relaxants (atracurium 40 micrograms/kg or metocurine 50 micrograms/kg), benzodiazepine agonists (diazepam 5 mg or midazolam 2.5 mg), or thiopental sodium 1 mg/kg on the increased muscle tone produced by alfentanil 175 micrograms/kg was compared with a control group (given no pretreatment).

MEASUREMENTS AND MAIN RESULTS

Rigidity was assessed quantitatively by measuring the electromyographic activity of five muscle groups (biceps, intercostals, abdominals, quadriceps, and gastrocnemius). Rigidity also was rated qualitatively by attempts to initiate and maintain mask ventilation, attempts to flex an extremity, and the occurrence of myoclonic movements. Pretreatment with the two nondepolarizing muscle relaxants had no effect on the severe muscle rigidity produced by high-dose alfentanil. Whereas thiopental was only mildly effective, the benzodiazepines midazolam and diazepam significantly attenuated alfentanil rigidity (p < 0.05).

CONCLUSION

This study suggests that benzodiazepine pretreatment is frequently, but not always, effective in preventing opioid-induced muscle rigidity.

Improved safety and efficacy in adaptive control of arterial blood pressure through the use of a supervisor

This paper presents a dual approach to adaptive control of arterial blood pressure using sodium nitroprusside. In the clinical environment, a controller must be aggressive to achieve specific step response characteristics (less than 10 min settling time, less than 10 mm Hg overshoot), yet conservative enough to prevent overreactions to large disturbances, which are common in both the operating room and the intensive care unit. These mutually exclusive requirements make it difficult to design a closed-loop controller for this environment. To prevent possible overreactions, while maintaining proper step response, an aggressive adaptive controller has been designed to achieve the desired step response, and a SUPERVISOR has been designed around the adaptive controller to limit potential overreactions in the presence of disturbances. Simulations and dog experiments demonstrate the potential for increased safety and efficacy using this dual approach to the control of a complex physiological system.

Supervisory adaptive control of arterial pressure during cardiac surgery

A supervisory adaptive controller has been designed for the closed-loop control of mean arterial pressure during cardiac surgery, using sodium nitroprusside. This controller consists of a pole-placement and proportional-plus-integral feedback regulator, multiple-model adaptation, and a supervisor. The pole-placement and proportional-plus-integral regulator was designed to meet aggressive step response characteristics. Multiple-model adaptation was chosen to ensure rapid and stable adjustments for changes in key patients parameters. The supervisor was designed to provide safety and efficacy of control during disturbances that are common during cardiac surgery. We studied the ability of this supervisory adaptive controller to regulate arterial pressure during cardiac surgery on nineteen patients. The controller, through the action of the supervisor, detected and responded appropriately to the great majority of disturbances. This study demonstrated that supervisory adaptive control has the potential to provide clinically acceptable regulation of arterial pressure.

Cardiovascular simulation using a multiple modeling method on a digital computer--simulation of interaction between the cardiovascular system and angiotensin II

A cardiovascular system model that simulates interactive responses to drugs has been developed on a small digital computer. The overall model basically consists of three models. The first is a momentum transport model that represents relations between blood pressure and flow in the cardiovascular system. In this model, the cardiovascular system is divided into 14 components and modeled by using equivalent electrical circuits. The second is a mass transport model comprising 14 compartments corresponding to the respective components of the cardiovascular system. This model represents the distribution of the administered drug in the various cardiovascular components. The third is an interaction model that represents the relationships between the momentum and mass transport models. This model causes variations in the resistance and capacitance parameters of the momentum transport model as a function of the current drug concentrations in the appropriate compartments of the mass transport model. The capacitances representing the ventricles are varied in a time-dependent fashion to simulate the beat of the heart. Simulation is performed by using the Euler method to solve a system of 28 ordinary differential equations governing the momentum and mass transport models on a 32-bit microcomputer, a Macintosh II. The model was assessed by performing two demonstrations of the cardiovascular response to the vasopressor angiotensin II (AT II). They first examined the interaction between the cardiovascular system and AT II. The effect of AT II on the cardiovascular system was incorporated into the interaction model. Administration of AT II as a constant infusion (200 micrograms/hr) resulted in an elevation of mean arterial pressure from approximately 100 to 150 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain sites mediating opiate-induced muscle rigidity in the rat: methylnaloxonium mapping study

Previous work has demonstrated that direct injections of methylnaloxonium (MN), a hydrophilic quaternary opiate antagonist, in the area of the nucleus raphe pontis (RPn) significantly attenuated alfentanil-induced muscle rigidity in the rat. To extend these observations and to explore further the regions important for opiate-induced rigidity, rats were implanted with chronic guide cannulae aimed at discrete brain sites with an emphasis on the region from the periaqueductal grey (PAG) to the RPn. Each animal was pretreated by a blinded observer with an intracerebral injection of MN (125 ng total dose) or saline, and electromyographic (EMG) activity was recorded from the gastrocnemius muscle. Alfentanil (ALF; 500 micrograms/kg) was then administered subcutaneously and the magnitude of tonic EMG activity was assessed as a measure of hindlimb rigidity. The administration of MN into the pontine raphe nucleus (RPn) and also into the more lateral nucleus reticularis tegmenti pontis significantly attenuated ALF rigidity compared with saline-pretreated controls. Within the midbrain, MN selectively reversed rigidity when injected into the periaqueductal grey (PAG). The dorsal PAG appeared to be a more important site than the ventral PAG. There was no significant effect on ALF rigidity of MN injections into brain regions between the ventral PAG and the RPn while MN injections into the deep layers of the superior colliculus, lateral to the dorsal PAG, partially attenuated ALF rigidity. In contrast, rigidity was not consistently reversed after MN injections into the basal ganglia, the dorsal superior colliculus, or the region of the decussation of the dorsal tegmentum. This study provides strong evidence that nuclei of the reticular formation, specifically the PAG, raphe pontis, and reticularis tegmenti pontis that are known to play a role in other opioid-mediated behaviors, are important in opiate-induced muscle rigidity in the rat. These results could have implications for the prevention of this undesirable effect of high-dose opiate administration.

Recognition accuracy with a voice-recognition system designed for anesthesia record keeping

We tested on three occasions, with anesthetists as subjects, the accuracy of two voice-recognition systems designed for anesthetic record keeping. Initially, a prototype system was tested (10 subjects); several years later the resulting commercial system was tested in a quiet environment (11 subjects) and in noisy operating rooms (10 subjects). For each test an anesthetist first trained the system to recognize his or her voice by reading aloud a list of common anesthetic terms. To determine recognition accuracy, the percentage of words recognized correctly by the computer, each subject repeated the vocabulary words ten times. Although accuracy was similar during the three tests, it was slightly higher with the laboratory test (mean percent of words recognized correctly, 96.5%; range of accuracy for individual anesthetists, 91.6 to 98.8%) than with the prototype test (95.9%; range, 89.1 to 99.6%). Accuracy was lowest with the operating room test (95.3%; range, 87.8 to 98.4%). Twenty-four words caused particular difficulty during the laboratory test and were eliminated from the vocabulary of the subsequent operating room test. Omitting these 24 words from the laboratory vocabulary list allowed a more nearly direct comparison with the results from the operating room list; recognition accuracy improved in the former to 97.5% (range, 92.1 to 98.9%). Two anesthetists--one each from the laboratory and operating room tests--performed poorly, and eliminating their scores changed the respective overall scores to 98.2% (range, 96.7 to 98.9%) and 96.5% (range, 94.3 to 98.4%). Thus, the corrected difference between the laboratory accuracy and the operating room accuracy was 1.7%.(ABSTRACT TRUNCATED AT 250 WORDS)

Seizures during opioid anesthetic induction--are they opioid-induced rigidity?

The tape recorded EEGs of 127 patients anesthetized with large doses of opioids were retrospectively analyzed for evidence of opioid-induced seizures, and in particular, correlated with movements that occurred during induction and could be clinically interpreted as seizures. Bilateral EEG leads in patients receiving fentanyl (20), sufentanil (20), or alfentanil (87) were recorded. Forty-six of these patients from all opioid groups manifested intense rigidity, as assessed both clinically and by EMGs recorded from eight muscles in 69 of the patients receiving alfentanil. This intense rigidity often resembled seizures, in that the phenomenon entailed severe stiffness of both limbs and trunk, with an explosive onset of myoclonic limb movements, and associated vertical nystagmus. Electroencephalographic observations were extensive, entailing 69 h of paper recordings played back from the tapes, at paper speeds of 30 or 60 mm/s, with detailed annotations from the voice track. These paper recordings were examined in detail independently by three of the investigators, who were unaware of the clinical phenomena that had occurred. The only observed EEG activity that could have been interpreted as epileptiform consisted of small sharp waves related to muscle activity or other artifact. The EEG never indicated seizure activity during these drug-induced movements and rigidity. Reports of opioid-induced seizures are reviewed and a set of criteria is offered to help achieve future consistency and credibility in evaluating this phenomenon. The available evidence does not support the existence of opioid-induced seizures in the clinical setting.

Pulse oximetry and finger blood pressure measurement during open-heart surgery

Pulse oximeter arterial hemoglobin oxygen saturation (SpO2) and finger arterial pressure (FINAP) were continuously monitored before, during, and after cardiopulmonary bypass in 15 male patients. SpO2 was monitored simultaneously with two pulse oximeters, a Nellcor N-100 and an Ohmeda Biox III. The readings obtained from the two pulse oximeters were compared with arterial blood measurements obtained using a CO-oximeter. FINAP was monitored by a prototype device (Finapres) based on the Penaz volume-clamp method. FINAP was correlated with intraarterial pressure (IAP). Both pulse oximeters functioned well before cardiopulmonary bypass. The correlations with CO-oximeter values were 0.927 for the N-100 and 0.921 for the Biox III. Immediately after the onset of cardiopulmonary bypass, the N-100 pulse oximeter stopped displaying values. The Biox III pulse oximeter continued to display values during the cardiopulmonary bypass period; the correlation with CO-oximeter values was 0.813. After cardiopulmonary bypass, the N-100 began displaying values in 2 to 10 minutes. After cardiopulmonary bypass the correlation with CO-oximeter values was 0.792 for the N-100 and 0.828 for the Biox III pulse oximeter. The Finapres finger blood pressure device functioned well in 13 of 15 patients before cardiopulmonary bypass. The mean bias +/- precision of FINAP-IAP for mean pressure was 8.3 +/- 10.2 mm Hg (SD) and the correlation coefficient was 0.814. During cardiopulmonary bypass, the Finapres device functioned well in 10 of 15 patients. The mean bias precision of FINAP-IAP, for mean pressure in these 10 patients was 6.6 +/- 8.7 mm Hg and the correlation coefficient was 0.902.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging and alfentanil disposition in healthy volunteers and surgical patients

We studied the pharmacokinetic disposition of alfentanil in 20 volunteers and in 15 surgical patients 20-72 years old. Pharmacokinetic disposition was first order and was well described by a two-compartment open model. Central-compartment volume of distribution was 0.131 +/- 0.087 L.kg-1 (mean +/- SD) in young healthy volunteers and decreased modestly with increasing age (r = -0.32, P less than 0.05). However, apparent volume of distribution at steady-state, 0.404 +/- 0.205 L.kg-1 for the whole study cohort, was not age-related. Plasma clearance of alfentanil in young healthy subjects, 9.3 +/- 6.3 ml.kg-1.min-1, also showed an inverse relationship with age (r = -0.54, P less than 0.001), and was not affected by surgical stress in subjects older than 60 years. Cigarette smoking and sex of the subjects did not contribute to interindividual differences in the kinetic disposition of this drug. Our finding that interindividual differences in disposition of alfentanil were the least in older subjects suggests that its pharmacological effects related to pharmacokinetic disposition should be most predictable in the elderly.

Prebypass hemodynamic stability of sufentanil-O2, fentanyl-O2, and morphine-O2 anesthesia during cardiac surgery: A comparison of cardiovascular profiles

Cardiovascular responses and the need for intervention with vasoactive agents were measured prospectively in a randomized study of 50 adult patients receiving sufentanil (n = 20), fentanyl (n = 20), or morphine (n = 10) anesthesia for cardiac surgery. Measurements were recorded and compared during induction and prebypass at intervals during which airway or surgically induced stress responses were likely to be greatest. Randomized, double-blinded doses of opioids were administered slowly and titrated according to clinical responses (hemodynamics) and the electroencephalogram. Mean doses were as follows: from induction until time of incision, sufentanil, 9.1 microg/kg; fentanyl, 58 microg/kg; and morphine, 2.5 mg/kg; and total dose for surgery; sufentanil, 18.9 microg/kg; fentanyl, 95.4 microg/kg; and morphine, 4.4 mg/kg. Equi-anesthetic depth in patients receiving sufentanil or fentanyl was confirmed by continuous electroencephalographic monitoring. Patients anesthetized with sufentanil and fentanyl showed marked cardiovascular stability and rarely responded to stimuli. Systolic arterial pressure, mean arterial pressure, heart rate, cardiac index, systemic vascular resistance index, pulmonary vascular resistance index, stroke volume index, and stroke work index values were similar in the two groups. Patients receiving morphine experienced large changes in several variables. Pharmacologic intervention was made when systolic arterial pressure deviated more than 30% from pre-event values and was uncontrolled by additional opioids. Interventions were necessary more often in patients receiving morphine (nine of ten) or fentanyl (12 of 20) than in patients receiving sufentanil (six of 20), P < 0.05. Results from this study suggest that morphine is a relatively unsatisfactory anesthetic, while sufentanil and fentanyl, at equi-anesthetic depths, provide stable and satisfactory hemodynamics.

Localization of brainstem sites which mediate alfentanil-induced muscle rigidity in the rat

Previous work has demonstrated that direct injections of methylnaloxonium (MN), a relatively lipophobic quaternary opiate antagonist, in the area of the nucleus raphe pontis (RPn) significantly attenuated alfentanil-induced rigidity. It was hypothesized that other hindbrain sites, particularly the other raphe nuclei, might play a role in this rigidity. Therefore, a study was performed in which 57 rats, divided into four groups, were implanted with chronic guide cannulae directed at brain sites anterior, lateral, or posterior to the RPn. After each animal was pretreated with intracerebral injections of MN, alfentanil (0.5 mg/kg) was administered subcutaneously. Electromyographic activity was recorded from the gastrocnemius muscle as a measure of hindlimb rigidity. Each animal was subsequently injected at 4 to 5 day intervals with MN two additional times at sites 1 and 2 mm deeper, respectively, than the initial injection. Data were thus obtained on animals treated with either MN or saline at 3 successive histologically identified sites which were either anterior, lateral or posterior to the RPn. The administration of MN into two specific sites in the region just lateral to the nucleus raphe pontis significantly [F(1,38) = 18.68 and 5.02 respectively, p less than 0.05] reversed the rigidity produced by systemic alfentanil administration. There was a weak effect of MN injections anterior to the RPn but this could not be localized to any one site. These results suggest that discrete brainstem regions involved in opiate action can be sensitively and selectively identified by direct intracranial injections of a lipophobic opiate antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer model analysis of the radial artery pressure waveform

Simultaneous measurements of aortic and radial artery pressures are reviewed, and a model of the cardiovascular system is presented. The model is based on resonant networks for the aorta and axillo-brachial-radial arterial system. The model chosen is a simple one, in order to make interpretation of the observed relationships clear. Despite its simplicity, the model produces realistic aortic and radial artery pressure waveforms. It demonstrates that the resonant properties of the arterial wall significantly alter the pressure waveform as it is propagated from the aorta to the radial artery. Although the mean and end-diastolic radial pressures are usually accurate estimates of the corresponding aortic pressures, the systolic pressure at the radial artery is often much higher than that of the aorta due to overshoot caused by the resonant behavior of the radial artery. The radial artery dicrotic notch is predominantly dependent on the axillo-brachial-radial arterial wall properties, rather than on the aortic valve or peripheral resistance. Hence the use of the radial artery dicrotic notch as an estimate of end systole is unreliable. The rate of systolic upstroke, dP/dt, of the radial artery waveform is a function of many factors, making it difficult to interpret. The radial artery waveform usually provides accurate estimates for mean and diastolic aortic pressures; for all other measurements it is an inadequate substitute for the aortic pressure waveform. In the presence of low forearm peripheral resistance the mean radial artery pressure may significantly underestimate the mean aortic pressure, as explained by a voltage divider model.

Ketanserin pretreatment reverses alfentanil-induced muscle rigidity

Systemic pretreatment with ketanserin, a relatively specific type-2 serotonin receptor antagonist, significantly attenuated the muscle rigidity produced in rats by the potent short-acting opiate agonist alfentanil. Following placement of subcutaneous electrodes in each animal's left gastrocnemius muscle, rigidity was assessed by analyzing root-mean-square electromyographic activity. Intraperitoneal ketanserin administration at doses of 0.63 and 2.5 mg/kg prevented the alfentanil-induced increase in electromyographic activity compared with animals pretreated with saline. Chlordiazepoxide at doses up to 10 mg/kg failed to significantly influence the rigidity produced by alfentanil. Despite the absence of rigidity, animals that received ketanserin (greater than 0.31 mg/kg i.p.) followed by alfentanil were motionless, flaccid, and less responsive to external stimuli than were animals receiving alfentanil alone. Rats that received ketanserin and alfentanil exhibited less rearing and exploratory behavior at the end of the 60-min recording period than did animals that received ketanserin alone. These results, in combination with previous work, suggest that muscle rigidity, a clinically relevant side-effect of parenteral narcotic administration, may be partly mediated via serotonergic pathways. Pretreatment with type-2 serotonin antagonists may be clinically useful in attenuating opiate-induced rigidity, although further studies will be necessary to assess the interaction of possibly enhanced CNS, cardiovascular, and respiratory depression.

Noninvasive continuous blood pressure measurement from the finger: optimal measurement conditions and factors affecting reliability

We recorded finger arterial blood pressure (FINAP) in 50 male patients during various types of surgical operations. Three different types of cuffs were used on four fingers of each patient. Measurements were made by the arterial volume-clamp method of Penaz. The FINAP measurements were compared with pressure data obtained ipsilaterally from a radial artery catheter-transducer system (intraarterial pressure [IAP]) to find optimal recording conditions and to document factors affecting FINAP readings. The thumb, with a specially designed cuff, gave the most accurate results. The mean FINAP - IAP difference for the thumb was -4.8 mm Hg for systolic pressure, 1.49 mm Hg for diastolic pressure, and 0.29 mm Hg for mean pressure. The differences were statistically significant for systolic and diastolic pressure but not for mean pressure. The regression slope for thumb systolic FINAP/IAP was 0.979, that for thumb diastolic FINAP/IAP was 0.963, and that for mean thumb FINAP/IAP was 0.996, whereas the intercepts were 7.499 for systolic pressure, 0.802 for diastolic pressure, and 0.083 for mean pressure. The correlation coefficients were 0.945 (systolic), 0.884 (diastolic), and 0.949 (mean). The correlation coefficients with the other fingers ranged from 0.502 to 0.922 for systolic pressure, 0.757 to 0.932 for diastolic pressure, and 0.767 to 0.892 for mean pressure. The slopes for the various finger-cuff combinations ranged from 0.537 to 0.996, and the intercepts ranged from 0.083 to 32.387 from mean pressure. In 3 patients (6%) the FINAP measurement was not possible because of insufficient peripheral circulation. In 9 other patients (18%) the FINAP measurements were not accurate during some periods of time.(ABSTRACT TRUNCATED AT 250 WORDS)

'Catatonia' produced by alfentanil is reversed by methylnaloxonium microinjections into the brain

Alfentanil, a short-acting and powerful analgesic, when injected peripherally to rats (0.5 mg/kg) produced a catatonic state characterized by a rigid akinesia. The present study was designed to explore the neuroanatomical location of the opiate receptors mediating the alfentanil induced catatonia. The catatonic effect of alfentanil was measured using a bar test and depression of locomotor activity in rats tested in photocell cages during an active nocturnal phase of their cycle. Methylnaloxonium HCl (MN), a quaternary derivative of naloxone which does not readily cross the blood-brain barrier, injected into the lateral ventricle significantly reduced the catatonia at doses of 0.125-2.0 micrograms as measured in both the locomotor and bar test. MN perfusion of similar doses directly into the nucleus raphe pontis, but not in the caudate nucleus significantly antagonized the catatonia. These data complement results on alfentanil-induced muscular rigidity (Blasco et al., see companion paper) where EMG indices of rigidity in rats were reversed by microinjections of low doses of MN (0.125 and 0.5 microgram) in the nucleus raphe pontis, but not the caudate nucleus even at a high dose (4.0 micrograms). Together these results suggest that the region of the nucleus raphe pontis is an important neural substrate for opiate-induced muscular rigidity, and that the catatonic state produced by opiates depends on more diffuse opiate receptor activation of which one important component may be the nucleus raphe pontis.

The role of the nucleus raphe pontis and the caudate nucleus in alfentanil rigidity in the rat

Attempts to eliminate or reduce the rigidity induced with high-dose narcotic anesthesia in the operating room have been only partially successful. Previous investigations of opioid receptor sites mediating this rigidity have implicated two central regions: the nucleus raphe pontis (NRP) within the reticular formation and the caudate nucleus (CN) within the basal ganglia. The present study used systemically administered alfentanil (ALF), a potent, short-acting fentanyl analog, and intracerebrally infused methylnaloxonium (MN), a quaternary derivative of naloxone, to elucidate further the functional role of the NRP and CN in rigidity. ALF (0.5 mg/kg s.c.) produced a reliable model of rigidity, as documented by gastrocnemius electromyography. The onset of this rigidity was within 60 s of ALF administration, with a total duration of approximately 40-50 min. Intracerebroventricular (i.c.v.) injections of 2.0 or 4.0 micrograms of MN 15 min prior to ALF treatment prevented rigidity, while 0.125 or 0.5 microgram had no significant effect on rigidity. MN injected directly into the NRP at doses as low as 0.125 microgram significantly antagonized ALF-induced rigidity, while injections of MN into the caudate nucleus at doses as high as 4.0 micrograms failed to antagonize ALF-induced rigidity. These observations demonstrate that injection of MN into the NRP is at least 16-fold more effective in blocking ALF-induced rigidity than MN injected into the ventricle and, more importantly, at least 32-fold more effective than MN injected into the CN. The results suggest that the NRP may be an important site for the neural control of muscular rigidity associated with high-dose narcotic administration.

Physiology of alfentanil-induced rigidity

The authors investigated the hemodynamic, metabolic, electroencephalographic (EEG), and electromyographic (EMG) characteristics of narcotic-induced rigidity during induction of anesthesia with alfentanil (175 micrograms/kg) in 10 patients. Thiopental (4 mg/kg) was administered to a ten-patient control group. Rigidity was quantified in eight muscle groups (sternocleidomastoid, deltoid, biceps, forearm flexors, intercostal, rectus abdominus, vastus medialis/lateralis, and gastrocnemius). Marked rigidity was observed in all muscle groups in all patients receiving alfentanil and in none receiving thiopental. Central venous pressure increased with onset of rigidity, while mean arterial pressure and cardiac index remained unchanged. Manual ventilation was extremely difficult during alfentanil-induced rigidity. Arterial oxygen tension decreased more rapidly during rigidity than during the same time interval in the control group, while patients experiencing rigidity were more acidotic, as reflected by greater increases in base deficit. The EEG demonstrated an anesthetic state without seizure activity. The immediate increase in central venous pressure with the onset of rigidity, along with occasional simultaneous parallel variations in central venous pressure and the EMG, strongly suggest a mechanical mechanism for the change in central venous pressure. The metabolic changes during rigidity may be partly related to the absence of the normal cardiovascular reflexes that are reported to occur during voluntary isometric muscle contractions. A neurochemical mechanism of narcotic-induced rigidity is briefly reviewed.

A comparison of morphine, fentanyl, and sufentanil anesthesia for cardiac surgery: induction, emergence, and extubation

We compared anesthetic doses of three popular opiates, morphine (n = 10), fentanyl (n = 9), and sufentanil (n = 9) in patients undergoing cardiac surgery. Opiate administration after induction was based upon EEG and cardiovascular signs of the depth of anesthesia. Total doses were morphine, 4.4 +/- 0.71 mg/kg, fentanyl, 95.4 +/- 9.9 micrograms/kg, and sufentanil, 18.9 +/- 2.2 micrograms/kg. Comparisons among opiates included times for induction of anesthesia, return of consciousness, return of spontaneous ventilation, return of adequate cardiovascular status, and extubation. The following times (mean and SEM) were significantly (P less than 0.05) shorter for sufentanil than for fentanyl or morphine: induction (15 +/- 2.3 min, 5.9 +/- 0.7 min, and 3.0 +/- 0.2 min for morphine, fentanyl, and sufentanil, respectively); return of consciousness (morphine 109.7 +/- 34.4 min, fentanyl 62.3 +/- 17.9 min, sufentanil 17 +/- 8.7 min); return of acceptable and stable cardiovascular status (morphine 587.3 +/- 139.3 min, fentanyl 537.9 +/- 144.8 min, sufentanil 173.7 +/- 56.8 min); and extubation (morphine 1121.3 +/- 61.8 min, fentanyl 1005.7 +/- 77.7 min, sufentanil 533.3 +/- 67.8 min). We conclude that sufentanil administered in the dosage range of 19 micrograms/kg allows more rapid induction, earlier emergence from anesthesia, and faster extubation of patients than either morphine or fentanyl.

The effect of muscle movement on the electroencephalogram during anesthesia with alfentanil

Using aperiodic analysis, we examined the impact on the electroencephalogram (EEG) of muscle activity from opiate-induced rigidity with alfentanil. We compared two groups of patients, one receiving alfentanil with neuromuscular blocking agents and the other group receiving no relaxants. The alfentanil-induced muscle rigidity exerted a noticeable effect on the EEG, with a moderate effect on total power at 1 Hz; a marked effect on the total number of waves, cumulative percent power at 3 Hz, and average power at 17 to 19 Hz; and a striking effect on F90, the frequency below which 90% of the power resides. The presence of electromyographic (EMG) noise in the EEG consistently altered the variables derived from the EEG, so that anesthetic depth appeared less than it actually was. This was true in spite of the fact that we gave slightly more alfentanil in the group not receiving a relaxant. Although the observed muscle activity was greater than that usually seen clinically, and may have differed qualitatively, the results do serve as a warning that muscle noise can interfere with the EEG. Currently, there is no computerized technique that will reject or account for this noise, and we must depend on observation to recognize the EMG patterns within the EEG, either with the raw recording or with a detailed analysis (such as aperiodic analysis), and to compensate for this noise if possible. Techniques that average the EEG or that present a single number have difficulty providing this information. These results do not detract from the usefulness of the EMG contained in EEG recordings as a supplementary or complementary indicator of anesthetic lightness.

An electroencephalographic comparison of alfentanil with other narcotics and with thiopental

Using aperiodic analysis, we compared the EEG produced by alfentanil with the EEGs produced by two other opiates--fentanyl and sufentanil--on the one hand and with the EEG produced by a barbiturate--thiopental--on the other hand. Alfentanil and thiopental were injected over 1 minute; fentanyl and sufentanil were injected over 10 to 15 minutes. From the aperiodic analysis we derived up to seven single-number variables computed over 30- or 60-second epochs. All the opiates induced EEGs that were qualitatively similar to each other, although the maximum or minimum values tended to be greater and the time course more rapid with alfentanil than with the other two opiates. This finding may have been related to the fact that we injected relatively more alfentanil and administered it more rapidly. The EEGs produced by alfentanil and thiopental differed markedly, both qualitatively and quantitatively. The total power at 1 Hz and cumulative power at 3 Hz went to higher peak values with alfentanil, the latter tending to decrease with thiopental. The total number of waves per epoch went to lower peak values with alfentanil; there was little change with thiopental. The frequency below which 90% of the power resides went to considerably lower peak values with alfentanil than with thiopental. Finally, total power at 10 to 12 Hz (alpha waves) and average power at 17 to 19 Hz (beta waves) went to very high peak values with thiopental, but decreased with alfentanil.(ABSTRACT TRUNCATED AT 250 WORDS)

Availability of intraarterial pressure waveforms from catheter-manometer systems during surgery

We determined how often and for how long usable pressure waveforms were unavailable from a radial intraarterial pressure cannula during anesthesia and surgery in 41 patients. During cardiac surgery with a continuous flush system, usable arterial pressure was unavailable 8.7% of the time. It was unavailable 9.1% of the time during noncardiac surgical procedures with a continuous flush system, and 14.7% of the time in system without continuous flush. Thus, the use of a continuous flush device improves intraarterial pressure availability. Artifact is the principal contributor to unavailability, followed by flushing and blood sampling. With rare exceptions the use of a Riva-Rocci cuff for occasional return-to-flow maneuvers on the same arm as the intraarterial cannula reduces intraarterial pressure availability only slightly, certainly not enough to detract from its usefulness in providing an estimation of systolic pressure during intraarterial pressure monitoring.

Evaluation of two prototype devices producing noninvasive, pulsatile, calibrated blood pressure measurement from a finger

We evaluated two prototype instruments that measure pulsatile blood pressure continuously and noninvasively and compared the mean arterial pressure obtained from these devices with that obtained invasively in 17 male surgical patients. Each prototype consisted of an infrared photoplethysmograph mounted inside a finger cuff. The cuff was connected to a pressure control valve, which rapidly changed the cuff pressure so as to maintain a null pressure difference across the finger arterial wall. The resultant cuff pressure rapidly tracked the pulsatile intraarterial pressure. The prototypes reproduced absolute pressure, as well as pressure changes, accurately and linearly over a wide range of mean arterial pressures (from 2 to 164 mm Hg), with an average offset error of 0.8 mm Hg (SD +/- 3.8; range, -4.6 to 7.9), a mean scatter error of 5.3 mm Hg (range, 3.6 to 8.6), a mean regression slope of 0.97 (range, 0.79 to 1.22) and a mean correlation coefficient of the regression of 0.96 (range, 0.89 to 0.98). Both prototypes worked satisfactorily on all 17 patients, but not all the time on all patients. In 7 patients, probable arterial spasm prevented measurement of finger blood pressure 12.1% of the time, or 5.4% of the time for all patients. Ninety-six percent of the lost samples occurred with prototype 2, suggesting an instrument-related cause, rather than one related to the principle itself. The prototypes were simple to use and were almost free from artifact. Continuous monitoring for up to 7 hours on a single finger caused no harm to the finger.

Automatic control in anesthesia: a comparison in performance between the anesthetist and the machine

This report is divided into two parts. First, we developed two new servo control systems by modifying an existing one. The original system was designed to control inspired halothane concentration using mean arterial pressure; the two new systems were designed to control inspired halothane concentration using end-tidal concentration or to control mean arterial pressure using the automated infusion of nitroprusside. Second, we compared the performance of experienced physician and nurse anesthetists (nine, six, and six experiments, respectively). The experiments incorporated a standardized testing sequence of two changes in desired blood pressure (set point) and two pharmacologically induced disturbances in blood pressure (perturbations). The scoring was designed to examine how fast blood pressure changed (90% response time), how far past the set point it went (overshoot), how long it took to eliminate most of the fluctuations in blood pressure (settling time), and the degree of fluctuation of blood pressure after settling (stability). Given three systems to be tested, there were (3 X 14) 42 possible mean scores for the machine and 42 for the anesthetists. The machine scored better than the anesthetists in 38 out of 42 of the mean scores; the differences were statistically significant in 19 out of 42 scores. The wide scatter in performances of the anesthetists prevented the achievement of significance in nine cases with large differences between means. Thus when the scores from the three systems were combined to achieve a larger n value, the machine outperformed the anesthetist in 12 out of 14 scores.(ABSTRACT TRUNCATED AT 250 WORDS)

EEGs during high-dose fentanyl-, sufentanil-, or morphine-oxygen anesthesia

In 49 patients undergoing open-heart surgery we compared the electroencephalographic (EEG) effects of high-dose morphine, fentanyl, or sufentanil with O2, using two computerized analysis and display techniques: a period analysis (the Klein method) and an aperiodic analysis (the Neurometrics monitor). During fentanyl or sufentanil anesthesia, both techniques revealed a general decrease in frequency, shown by the aperiodic analysis primarily as a marked increase in the very low frequency range: an increase in the 1-Hz bin (TP1, in muv2) from 2.80 X 10(4) +/- 3.20 X 10(4) (SD) to 45.1 X 10(4) +/- 27.2 X 10(4) for fentanyl and from 3.11 X 10(4) +/- 2.83 X 10(4) to 52.8 X 10(4) for sufentanil. The cumulative percent power at 3 Hz (CP3) increased from 27.2 +/- 6.8 to 83.0 +/- 11.0 for fentanyl and from 22.7 +/- 5.2 to 85.1 +/- 10.4 for sufentanil, while the frequency at 90% cumulative percent power (F90, in Hz) decreased from 17.8 +/- 2.9 to 7.9 +/- 2.8 for fentanyl and 16.4 +/- 5.2 to 5.6 +/- 4.3 for sufentanil. The changes with morphine were less obvious, with some attenuation of high-frequency power shown by the Klein method, and an increase from 24.1 +/- 8.6 to 59.3 +/- 20.7 with CP3, but no change in TP1. Low-frequency power with the period analysis and TP1 with the aperiodic analysis decreased between laryngoscopy and the incisions with fentanyl and sufentanil.(ABSTRACT TRUNCATED AT 250 WORDS)