Is lower esophageal contractility a reliable indicator of the adequacy of opioid anesthesia?

Assessing the adequacy of anesthesia in the patient who is without neuromuscular blockade is usually based on somatic as well as sympathetic and hemodynamic responses to stimulation. Because somatic responses are lost in the patient with neuromuscular blockade, a method is needed to replace these signs as an indicator of inadequate anesthesia. This study attempted to determine the relationship between lower esophageal contractility and somatic signs in detecting inadequate fentanyl anesthesia in 20 patients who were undergoing coronary artery surgery and who were hemodynamically stable in the preoperative period. Premedication included midazolam, 0.05 mg/kg intramuscularly, and ranitidine, 2 mg/kg orally. Anesthesia was induced with fentanyl, 50 µg/kg, and maintained by an infusion of fentanyl, 0.2 µg · kg^–1 · min^–1. After endotracheal intubation, a disposable 24-F esophageal monitoring probe equipped with provoking and measuring balloons was inserted, and both the amplitude of provoked and the rate of spontaneous lower esophageal contractions were displayed and recorded. Inadequate anesthesia was indicated by defined somatic signs in response to noxious stimulation. The presence of these responses was correlated with the amplitude of the provoked and the rate of the spontaneous contractions at five specific times during the period preceding initiation of cardiopulmonary bypass. A total of 208 episodes of stimulation were recorded: at insertion of the nasal temperature probe (n=8), at skin penetration by towel clips (n=25), at skin incision (n=20), at sternotomy (n=20), and during multiple episodes of electrocauterization (n=135). These provoked 23 somatic responses. The fentanyl concentration in plasma of the 20 patients during the study period was 30±10 ng/ml (mean±SD). The rate of the spontaneous contractions at times of response (6.0±4.8 contractions per 3-minuteperiod, mean±SD) was significantly greater than that at times of no response (2.6±3.0 contractions per 3-minute period), whereas there was no significant difference in the amplitude of provoked contractions (18.2±11.4 versus 16.2±8.5 mm Hg). The most favorable cutoff point was determined to be a rate of 6 contractions per 3-minute period. This produced a false-positive rate of 11.9% and a sensitivity (true-positive rate) of 52.2%. We conclude that the use of lower esophageal contractility is not reliable for detection of inadequate anesthesia when an opioid (fentanyl) is used as the primary anesthetic agent.     

Effect of sevoflurane on P50 and on measurement of oxygen tension

Fresh samples of heparinized human blood from 10 healthy nonsmoking volunteers were used to study the effect of the inhaled anesthetic sevoflurane on the oxygen half-saturation pressure of hemoglobin (P₅₀) and on polarographic measurements of oxygen tension at low values. Control samples had a baseline P₅₀ of 26.9±0.2 mm Hg. When the blood samples were exposed to 1.75% (1 minimum alveolar concentration, MAC), 2.75%, and 3.5% (2 MAC) of sevoflurane, the P₅₀ values were 27.0±0.5 mm Hg, 27.1±0.4 mm Hg, and 26.9±0.5 mm Hg, respectively. Our present data show that 1 to 2 MAC sevoflurane has no significant effect on P₅₀ (P>0.05). Our data also show that sevoflurane did not interfere with polarographic measurements of oxygen tension (P>0.05). Other inhaled agents—halothane, enflurane, and isoflurane—do interfere with these measurements, and we cannot explain the difference.Presented at the annual meeting of the American Society of Anesthesiologists, Atlanta, GA, October 1987.     

Electroencephalogram spectral edge frequency,lower esophageal contractility,and autonomic responsiveness during general anesthesia

Both the electroencephalogram (EEG) spectral edge frequency (SEF) and lower esophageal contractility (LEC) indices have been reported to be useful indicators of anesthetic depth. We designed a prospective study to evaluate the relationship between changes in these two variables and objective measurements of physiologic responsiveness to surgical stress (i.e., changes in hemódynamic variables and plasma levels of norepinephrine, epinephrine, total catecholamines, and vasopressin). Eighty-nine consenting adult males undergoing radical prostatectomy procedures under a standardized general anesthetic technique were studied according to a randomized, single-blinded protocol. General anesthesia was induced with 30 µg/kg intravenous (IV) alfentanil, 2.5 mg/kg IV thiopental, and 0.1 mg/kg IV vecuronium, and subsequently maintained with 0.5 µg/kg/min alfentanil, nitrous oxide (N₂O) 67% in oxygen, and 0.8 µg/kg/min vecuronium. Following retropubic dissection, 81 patients (92%) manifested acute hypertensive responses, with mean arterial pressure increasing from 90±14 to 122±14 mm Hg (mean ± SD). This acute hypertensive response was treated with one of three different treatment modalities (20 to 60 µg/kg IV alfentanil, 0.5 to 2.0% inspired isoflurane, or 0.05 to 0.15 mg/kg IV trimethaphan) to return the mean arterial pressure to within 10% of the preincisional (baseline) value within 5 to 10 minutes. Although the mean arterial pressure, heart rate, and plasma levels of catecholamines and vasopressin significantly increased following the surgical stimulus, and decreased after adjunctive therapy, the EEG-SEF and LEC index (LECI) values did not significantly change during these study intervals. Furthermore, using a logistic regression analysis, we observed that preincision EEG-SEF and LECI values could not predict whether patients would manifest a hypertensive response. Therefore, the EEG-SEF and LECI were unreliable indicators of anesthetic depth.This study was supported in part by a grant from the Ambulatory Anesthesia Research Foundation, Los Altos, CA. (Dr White is a member of the Board of Directors.)The authors would like to thank Dan Kuni (Baxter Healthcare) for his assistance in obtaining the equipment used to perform the study; Vinod Kothapa, MD, for his valuable assistance with the anesthetic management of the study patients; Alex K. Mills, MD, for his assistance with the EEG interpretation; and Steven A. Bai, PhD, for his assistance with the plasma alfentanil analyses.     

Comparing the relaxing effects of desflurane and sevoflurane on oxytocin-induced contractions of isolated myometrium in both pregnant and nonpregnant rats

In this study, the effects of 2 volatile anesthetics, desflurane and sevoflurane, on oxytocin-induced contractions of isolated myometrium in pregnant and nonpregnant rats were compared. Twenty pregnant and 20 nonpregnant Wistar albino rats were studied at 19 to 20 days’ gestation (term, 22 days). A total of 40 myometrial strips were obtained from pregnant and nonpregnant rats, and each of these was randomly assigned to 1 of 4 groups (n=10, each group). After spontaneous myometrial contractions were induced in the De Jalon solution, the effects of 0.5, 1, and 2 minimum alveolar anesthetic concentrations (MAC) of desflurane or sevoflurane, in the absence and presence of oxytocin (2×10⁻⁹ M), were investigated. Oxytocin significantly increased the amplitude and duration of spontaneous contractions in longitudinal myometrial strips (P < .05), but not the frequency. Both agents (except for 0.5 MAC in the nonpregnant group) inhibited the duration, amplitude, and frequency of induced contractions in a dose-dependent manner. The inhibitory potencies of desflurane and sevoflurane were similar. It was found that isolated strips of pregnant rat myometrium were more sensitive to the inhibitory effects of both agents than were the nonpregnant rat myometrial strips.     

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 asF95, the frequency in hertz below which resides 95% of the power in the EEG frequency spectrum. The relations betweenF95 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 byF95 was tested using (beta), a measure of the slope of anF95-response logistic curve. The presence of shifts among theF95-response logistic curves was tested using the differences inF95 values between curves. Hypothesis tests used a level of significance ofP = 0.05.Main Results. The slopes of theF95-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 anF95-response logistic curve for the tenth combination because it contained burst suppression, which our EEG analysis method was not designed to process. TheF95-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 ofF95; the range in shifts was 0.2 to 8.1 Hz. The slope values of theF95-response logistic curves and the shifts among the curves were similar to the values and shifts that might be expected from changes in anesthetic agent doses.Conclusions. The EEG, expressed asF95, predicted movement response to surgical stimuli during combinations of isoflurane, 70% N₂O, and fentanyl. TheF95-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. OurF95-response curves may provide helpful guidelines for usingF95 to titrate the administration of anesthetic agents and for assessing the depth of general anesthesia.     

Comparative accuracies of a finger blood pressure monitor and an oscillometric blood pressure monitor

A noninvasive blood pressure monitor (Finapres) that uses the methodology of Peaz to continuously display the arterial waveform from the finger has been introduced recently. The Finapres monitor overestimated systolic pressure by 5.8±11.9 mm Hg, while the Dinamap monitor underestimated systolic pressure by –6.9±9.2 mm Hg (P=0.003). Dinamap mean and diastolic pressure biases were less than 2 mm Hg, while the Finapres biases for these variables were significantly greater (7.7±10.0 and 8.2±9.8 mm Hg, respectively). There was no difference in systolic or mean pressure precision between the two devices (approximately 10 mm Hg), but the diastolic precision of the Dinamap unit was superior to that of the Finapres. While in most patients the Finapres monitor provided continuous blood pressure data equivalent to the data from the radial artery, marked bias (>15 mm Hg) was exhibited in 2 patients for all three pressure variables. Despite this bias, blood pressure changes were tracked closely in these 2 patients. We conclude that, in its current form, the Finapres monitor cannot be relied upon independently to accurately measure blood pressure in patients undergoing general anesthesia. Since the Dinamap monitor measures mean pressure reliably and accurately, we suggest that mean blood pressure values between the Finapres and Dinamap monitors be compared to guide one in interpreting Finapres data.Supported in part by a grant from Ohmeda Company, Boulder, CO.Presented in part at the annual meeting of the American Society of Anesthesiologists, New Orleans, October 1989.     

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 F_p2 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 (^Ciso_Brain) 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 µV 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 iso_Brain at this endpoint. We similarly defined the move endpoint and estimated the move endpoint^C iso_Brain. We then calculated the increment of^C iso_Brain 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 ^Ciso_Brain 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.     

The contractility of the lower portion of the esophagus as a criterion of the adequacy of anesthesia]

It has been found that narcotic analgesics (morphine, fentanyl and dipidolor), inhalation anesthetics (phthorothan and frilen) and an intravenous anesthetic calypsol suppress lower esophageal contractility. Comparison of lower esophageal contractility with hemodynamic parameters and ACTH and cortisol blood plasma content have revealed a direct correlation. It is concluded that the method of dynamic control over lower esophageal contractility may be an objective test controlling the adequacy of anesthesia during various surgical interventions.     

Normal fluctuation of physiologic cardiovascular variables during anesthesia and the phenomenon of “smoothing”

With the advent of automated anesthesia record keeping devices, concern has arisen that “abnormal” values will appear in the record and possibly lead to medicolegal compromise. A retrospective review of automated records from a series of anesthesia cases was undertaken to determine if abnormal values do occur, how frequent they are, and whether they cause problems. A total of 14,826 (4,942 each) noninvasive heart rate, systolic, and diastolic blood pressure readings from 118 case printouts generated by a Diatek Arkive Patient Information Management System (63 cases) or a Data-scope Datatrac record keeper (55 cases) were recorded. The study sample covered a broad range of surgical operations, anesthetic procedures, and patient ages and medical histories. During these 118 anesthetics, the majority of readings of all three variables fell within normal ranges (defined for this study as 80 to 180 and 50 to 110 mm Hg for systolic and diastolic blood pressures, respectively, and 60 to 140 beats/min for heart rate). During the anesthetics, 3.6% of the systolic pressure readings, 13.25% of the diastolic readings, and 4.25% of the heart rate readings were recorded outside these ranges. No serious intraoperative or postoperative anesthesia complications were associated with these out-of-range readings, nor would they be expected in a sample of this size, since serious anesthetic complications are rare. This preliminary observation of one person's experience may help address the concern associated with allowing high and low blood pressure and heart rate readings to be automatically recorded “unsmoothed.” In medicolegal situations, it should also begin to demonstrate that such fluctuations are neither uncommon nor abnormal, and that a true record of these readings should be neither a cause for concern nor an opportunity for medicolegal exploitation.     

Automated measurements of isolated heart muscle contractions: Effects of halothane,calcium, and magnesium on guinea pig left atrial muscle

An in vitro method for automatically measuring muscle contraction force has been demonstrated in a study of the effects of the inhalation anesthetic halothane followed by calcium chloride or magnesium sulfate on isolated guinea pig left atrial muscle. An automated computer-controlled system was used to collect muscle contraction force waveforms and to analyze contraction waveforms for comparison of variables before and after drug administration. Two concentrations of halothane (0.5 and 1.5%) were administered to the atrial preparation for 30 minutes and followed by calcium chloride or magnesium sulfate. Six variables (latency, time to peak tension, peak tension, maximum rate of change of pressure, force time integral, and relaxation time) were automatically determined from averaged stimulus-response curves. Results were normalized and compared with controls administered only calcium and magnesium and with controls administered no drugs. The automated system greatly simplified data collection and accumulation and statistical analysis of multiple responses. The system made possible averaging and analysis of more data with less variability than is normally obtained with manual systems. The results confirm several known actions of these agents. Halothane prolongs latency (9 and 21% for 0.5 and 1.5% halothane, respectively) and shortens time to peak tension (6 and 17% for 0.5 and 1.5% halothane, respectively) and relaxation time (17 and 39% for 0.5 and 1.5% halothane, respectively). At high halothane concentrations (1.5%), calcium chloride shortens latency (10%) and prolongs time to peak tension (11%); magnesium sulfate prolongs latency (14%) and shortens time to peak tension (10%).     

Automated measurements of isolated heart muscle contractions: Effects of halothane, calcium, and magnesium on guinea pig left atrial muscle

An in vitro method for automatically measuring muscle contraction force has been demonstrated in a study of the effects of the inhalation anesthetic halothane followed by calcium chloride or magnesium sulfate on isolated guinea pig left atrial muscle. An automated computer-controlled system was used to collect muscle contraction force waveforms and to analyze contraction waveforms for comparison of variables before and after drug administration. Two concentrations of halothane (0.5 and 1.5%) were administered to the atrial preparation for 30 minutes and followed by calcium chloride or magnesium sulfate. Six variables (latency, time to peak tension, peak tension, maximum rate of change of pressure, force time integral, and relaxation time) were automatically determined from averaged stimulus-response curves. Results were normalized and compared with controls administered only calcium and magnesium and with controls administered no drugs. The automated system greatly simplified data collection and accumulation and statistical analysis of multiple responses. The system made possible averaging and analysis of more data with less variability than is normally obtained with manual systems. The results confirm several known actions of these agents. Halothane prolongs latency (9 and 21% for 0.5 and 1.5% halothane, respectively) and shortens time to peak tension (6 and 17% for 0.5 and 1.5% halothane, respectively) and relaxation time (17 and 39% for 0.5 and 1.5% halothane, respectively). At high halothane concentrations (1.5%), calcium chloride shortens latency (10%) and prolongs time to peak tension (11%); magnesium sulfate prolongs latency (14%) and shortens time to peak tension (10%).     

Comparison of the Level of Free Hexafluoro-isopropanol in Adults’ Blood and the Incidence of Emergence Agitation After Anesthesia With Different Concentrations of Sevoflurane in Laparoscopic Gastrointestinal Surgery: A Randomized Controlled Clinical Trial

PurposeThe aim of the study is to compare the free hexafluoro-isopropanol (HFIP) concentration in adults' blood and the incidence of emergence agitation (EA) after inhaled different concentrations of sevoflurane.MethodsSixty adult patients planning to undergo laparoscopic gastrointestinal surgery were randomly assigned to 3 groups. Each group received sevoflurane as the volatile anesthetic at different concentrations: 0.5 minimum alveolar concentration (MAC), 1.0 MAC, and 1.5 MAC. The use of sevoflurane was continued until the end of surgery. Venous blood samples were obtained at 30, 60, 120, and 180 minutes after starting the use of sevoflurane and subsequently at 60, 180, and 300 minutes after discontinuation of volatile anesthetic administration. Blood concentrations of sevoflurane and free HFIP were determined using gas chromatography. The recovery time and the incidence of EA at different time points were evaluated among the 3 groups.FindingsChanges in the blood concentrations of sevoflurane and free HFIP during and after the use of sevoflurane were similar in all 3 groups. The peak blood concentration of free HFIP occurred 60 minutes after onset of sevoflurane anesthesia in all 3 groups (P < 0.05). The lowest level of free HFIP and the longest recovery time were found in the 1.5-MAC group (P < 0.05). No significant difference was found in the incidence of EA or moderate pain among the 3 groups during recovery.ImplicationsThe generation of HFIP would be inhibited when the inhaled sevoflurane concentration increased to 1.5 MAC. However, the incidence of EA during recovery had nothing to do with the inhaled different sevoflurane concentrations (within 1.5 MAC) in adults. ChicCTR.org identifier: ChiCTR-IPD-17011558.     

Noninvasive Doppler blood pressure monitoring in the monoplace hyperbaric chamber

We describe a noninvasive method of monitoring blood pressure in the monoplace hyperbaric chamber. A standard blood pressure cuff was placed on the patient's arm. A Doppler probe, linked to an ultrasonic Doppler flow detector outside the chamber, was secured over the patient's radial artery. Cuff inflation tubing and the Doppler probe wires were passed into the chamber by modifying a standard disposable hyperbaric intravenous pass-through. Blood pressure readings were determined by inflating and slowly deflating the cuff from outside the chamber while observing the sphygmomanometer within the chamber and listening for the first audible flow signal from the Doppler detector, corresponding to the systolic blood pressure. To minimize the risk of fire in the oxygen-filled monoplace hyperbaric chamber, the patient, Doppler detector, and chamber were grounded. Doppler readings obtained from nine normal subjects whose arterial pressures were being measured with indwelling radial arterial catheters (approved as part of another study by the hospital's Investigational Review Board) compare closely with the subject's blood pressures measured with this noninvasive method: 114±7.6 mm Hg (mean±1 SD) compared to 112±8.1 mm Hg, respectively (n=92 measurements in 8 subjects). We conclude that this noninvasive method of monitoring blood pressure within the monoplace hyperbaric chamber is accurate and suitable for monoplace clinical purposes.This study was supported by a grant from the Deseret Foundation of the LDS Hospital, Salt Lake City, UT.We wish to thank the subjects who volunteered for this investigation, and we appreciate the help of Pam Evans, RRT, and the rest of the hyperbaric staff who assisted in the data collection.     

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.This work was supported by the Kaiser Foundation Research Institute. Elements of this work were presented at the Society for Technology in Anesthesia, January 1992, San Diego, CA.     

Fuzzy-logic control of blood pressure through enflurane anesthesia

Objective. The objective of our study was to construct a closed-loop blood pressure control system using fuzzy logic during enflurane anesthesia.Methods. Direct systolic blood pressure (SBP), the input variable, was assessed by a special fuzzy-logic membership function—that is, a triangulate continuum of grades between 0 and 1. We also set up the output membership function for the inhaled enflurane concentration. Four fuzzy-rule maps, or matrices, which determined the relationship between the changes of input variables and output values, were constructed based on published anesthetic values. The first map was based on the end-tidal anesthetic concentration known to block an adrenergic response. The fourth map was derived from the anesthetic effective dose (AD₉₅). Fuzzy inference, arrived at by using fuzzy logic, followed the minimum-maximum center of gravity method. Anesthetic control started with the first map and was maintained with the succeeding maps.Results. During anesthesia, the SBP remained within ±20% of the preanesthetic SBPs in 82% of the fuzzy control cases and within 83% during manual control. The difference was not significant.Conclusion. The anesthetist’s management of the administration of the inhaled anesthetic enflurane was imitated by fuzzy-logic control of the blood pressure. This paper was presented in part at the Proceedings of the International Conference on Fuzzy Logic & Neural Networks IIZUKA ’90.     

Physiological vital sign differences between well newborns greater than 34 weeks gestation: A pilot study

BackgroundNewborns have their vital signs measured as part of routine care. However, there is inconsistency in accepted physiological ranges for well newborns beyond the post-delivery stabilisation period which has implications for the identification of illness.ObjectiveTo explore differences in physiological vital signs between three gestational age groups: late preterm (34⁺⁰ - 36⁺⁶), early term (37⁺⁰–38⁺⁶) and term (≥39⁺⁰) weeks gestation.DesignA single site prospective observational study.SettingA postnatal ward and special care baby unit in a major tertiary hospital in Australia.ParticipantsNewborns from 34 weeks gestation admitted to either the postnatal ward or special care baby unit.MethodsHeart rate, respiratory rate and oxygen saturation were continuously monitored for up to 6 h. Newborn temperature and blood pressure were measured twice during the monitoring period.ResultsContinuous monitoring resulted in 284,542 heart rate, 275,826 respiratory rate, 287,572 SpO₂ values, and 60 temperature and 60 blood pressure data points. Heart rate was significantly different between gestational age groups with late preterm heart rates 13.4 bpm (95% CI 6.5–20.4) higher than term newborns. Early term heart rates were 2.3 bpm (95% CI -4.6 – 9.3) higher than term newborns, although not statistically significantly different. Heart rate was significantly different based on sex with females on average 7.7 beats per minute (bpm) (95% CI 1.9–13.5) higher than males.Respiratory rate was not significantly different between gestational age groups however, on average, was −2.0 respiration rate per minute (rpm) (95% CI -6.8 – 2.7) lower for late preterm babies and −1.3 rpm (95% CI -6.0 – 3.4) lower for early term babies compared to term newborns. SpO₂ was not significantly different between gestational age groups, however, on average was −1.17 log units (95% CI -2.32 to −0.01) lower for late preterm newborns and −1.00 log units (95% CI -2.16 – 0.15) lower for early term newborns compared to term newborns. Respiratory rate and SpO₂ were neither clinically nor statistically significantly different by sex.There were no significant differences between gestational age groups for temperature (p = 0.38) or blood pressure (systolic p = 0.93, diastolic p = 0.54). No significant mean differences were observed based on sex for temperature (p = 0.57) or blood pressure (systolic p = 0.98, diastolic p = 0.40).ConclusionsThis study demonstrated a clinically significant higher heart rate in those born late preterm. This may have implications for current “one-size fits all” newborn early warning tools, as well as care of well late preterm infants in maternity units.     

Parameters influencing the response time of volatile anesthetics monitors

Summary In a given inhalational anesthetic analyzer, response (RT) is usually thought to be a constant value, however, several factors may influence RT. RT's measured under ideal conditions for the Beckman LB2, the Normac (Datex), the Servo S 120 (Siemens) and the Irina (Dräger) were 107±5, 589±14, 538±30, and 166±15 msec, respectively. In addition, we investigated the RT of a Beckman LB 2 analyzer under conditions which may occur in clinical practice (non ideal conditions).Increasing aspirating flow (AF) resulted in shorter RT's, the effect being most pronounced when AF was below 200 ml/min. Interposing a filter prolonged RT by 80%. The type of the inhalational anesthetic (halothane or isoflurane), humidity and temperature of the carrier gas as well as size and direction of the concentration step change did not influence RT.Increasing lenght or internal diameter (ID) of the sample tube resulted in longer RT's. Changing the sample tube material from glass to Teflon or polyethylene resulted in a slight increase of RT, but the increase was dramatic when rubber or silicone tubes were used. The partition coefficient of halothane in the material of a particular sample tube was directly correlated to the corresponding RT in this sample tube.The influence of different sampling places was studied by interposing copper or corrugated rubber tubing between the place where the concentration step change occurred and the place where the gas was sampled, the measured time was called total response time (TRT). Using corrugated rubber tubes instead of copper tubes increased TRT two to four times. More distal gas sampling and/or lower flow rates caused longer TRT's. Compared with sampling in its center, gas sampling near the walls of the tube resulted in an increase in TRT of 13–45%.It is concluded that the response time of an infrared inhalational anesthetic analyzer is not a constant parameter, but varies between 100 and 4000 msec depending on the characteristics of the analyzer, the sample line, and the place of gas sampling.Technical assistance: J. Maertens.     

Effect of antihypertensive treatment on the prevalence of ventricular arrhythmias among patients with isolated systolic hypertension without left ventricular hypertrophy

Background: The high incidence of ventricular arrhythmias in patients with hypertension and left ventricular hypertrophy (LVH) is well documented. However, few studies have been conducted on the prevalence of ventricular arrhythmias in patients with isolated systolic hypertension without LVH.Objectives: The objectives of this study were to (1) determine the prevalence of ventricular arrhythmias in patients with systolic hypertension without LVH and (2) estimate the effect of a perindopril/indapamide combination, which does not have an antiarrhythmic effect, on the incidence of ventricular arrhythmias.Methods: Patients with newly diagnosed isolated systolic hypertension (systolic blood pressure [SBP] >160 mm Hg) and a control group of normotensive patients were enrolled. During the 2-week washout period, patients underwent physical examination (including blood pressure measurements), ambulatory electrocardiography monitoring, echocardiography, and laboratory urine and blood tests. Absence of LVH was confirmed by echocardiographic examination. The group of hypertensive patients received 1 tablet of 2 mg perindopril/0.625 mg indapamide per day for a total of 4 weeks. Physical examinations and ambulatory electrocardiographic monitoring were repeated after treatment.Results: A total of 60 hypertensive (mean age, 63.1 years; mean SBP, 176.8 ± 3.1 mm Hg; mean diastolic blood pressure, 82.6 ± 2.9 mm Hg) and 60 normotensive patients were enrolled. Ambulatory electrocardiographic monitoring indicated that 18 of the 60 hypertensive patients (30%) had ventricular arrhythmias: 17 had ventricular premature contractions (>100/24 h) and 1 had ventricular tachycardia plus ventricular premature contractions. In the control group, 7 of 60 subjects (11.7%) had ventricular premature contractions. The difference between the 2 groups in incidence of ventricular arrhythmias was significant (P < 0.01). After treatment, mean SBP decreased to 136.1 ± 3.2 mm Hg, and ventricular premature contractions were found in 9 of 60 hypertensive patients (15%) (P < 0.02 vs pretreatment).Conclusions: The results of this study suggest that in patients with isolated systolic hypertension without LVH, (1) the prevalence of ventricular arrhythmia is higher than in normotensive patients and (2) treatment with perindopril/indapamide decreases the incidence of ventricular arrhythmias.     

经口内镜下肌切开术治疗贲门失弛缓症的疗效分析（附30例报告）

目的观察分析经口内镜下肌切开术(POEM)治疗贲门失弛缓症(AC)的临床疗效。方法收集2013年3月-2017年6月实施POEM的30例AC患者,评估手术前后Eckardt评分,记录食管动力测压结果、体质指数(BMI),总结手术完成情况、术后并发症及随访过程等资料。结果 30例患者行POEM治疗成功率100.0%,3例患者发现皮下气肿,2例有轻微胸骨后不适,4例有术后发热,1例发生迟发的上消化道出血。术后Eckardt评分(1.1±0.6)分与术前(5.2±1.3)分对比明显降低(P0.05),术后BMI(22.6±2.9)kg/m~2与术前(19.2±1.8)kg/m~2相比较前增加(P0.05)。食管动力学指标中,食管下括约肌静息压(LESP)术后(18.2±9.5)mm Hg对比术前(46.7±15.8)mm Hg明显降低(P0.05),食管下括约肌完整松弛压(IRP)术后(10.5±2.5)mm Hg对比术前(22.8±8.3)mm Hg也明显下降(P0.05),食管下括约肌长度(LESL)术后(2.5±0.5)cm对比术前(2.9±0.8)cm明显缩短(P0.05)。食管上括约肌静息压(UESP)和食管上括约肌长度(UESL),手术前后差异均无统计学意义(P0.05)。结论 POEM是治疗AC的有效手段,其短期疗效确切,且安全性相对较高,部分食管动力学指标较前改善,但其远期并发症及有效性还需大样本进一步随访。     

Noninvasive blood pressure monitoring from the supraorbital artery using an artificial neural network oscillometric algorithm

Objective. Our objective was to overcome the limitations of linear models of oscillometric blood pressure determination by using a nonlinear technique to model the relationship between the oscillometric envelope and systolic and diastolic blood pressures, and then to use that technique for near-continuous arterial pressure monitoring at the supraorbital artery.Methods. An adhesive pressure pad and transducer were used to collect oscillometric data from the supraorbital artery of 85 subjects. These data were then used to train an artificial neural network (ANN) to report diastolic or systolic pressure. Arterial pressure measurements defined by brachial artery auscultation were used as a reference. ANN results were compared with those obtained using a standard oscillometric algorithm that determined pressures based on fixed percentages of the maximum oscillometric amplitude.Results. The ANN produced better estimates of reference blood pressures than the standard oscillometric algorithm. Mean difference between target and actual output for the ANN was 0.50±5.73 mm Hg for systolic pressures, compared to the mean difference of the standard algorithm of 2.78±19.38 mm Hg. For diastolic pressures, the ANN had a mean difference of 0.04±4.70 mm Hg, while the mean difference of the standard algorithm was –0.34±9.75 mm Hg.Conclusions. The ANN produced a better model of the relationship between the oscillometric envelope and reference systolic and diastolic pressures than did the standard oscillometric algorithm. Noninvasive blood pressure measured from the supraorbital artery agreed with pressure measured by auscultation in the brachial artery, and may sometimes be more clinically useful than an arm cuff device.This research was supported, in part, by a grant from Baxter Healthcare Corporation (Santa Ana, CA), and Innerspace Medical (Irvine, CA). A grant of computer time from the Utah Supercomputer Institute, which is funded by the State of Utah and the IBM Corporation, is gratefully acknowledged.