Tammy Y. Euliano

Monitoring uterine activity during labor: a comparison of 3 methods

OBJECTIVE Tocodynamometry (Toco; strain gauge technology) provides contraction frequency and approximate duration of labor contractions but suffers frequent signal dropout, necessitating repositioning by a nurse, and may fail in obese patients. The alternative invasive intrauterine pressure catheter (IUPC) is more reliable and adds contraction pressure information but requires ruptured membranes and introduces small risks of infection and abruption. Electrohysterography (EHG) reports the electrical activity of the uterus through electrodes placed on the maternal abdomen. This study compared all 3 methods of contraction detection simultaneously in laboring women. STUDY DESIGN Upon consent, laboring women were monitored simultaneously with Toco, EHG, and IUPC. Contraction curves were generated in real-time for the EHG, and all 3 curves were stored electronically. A contraction detection algorithm was used to compare frequency and timing between methods. Seventy-three subjects were enrolled in the study; 14 were excluded due to hardware failure of 1 or more of the devices (n = 12) or inadequate data collection duration (n = 2). RESULTS In comparison with the gold-standard IUPC, EHG performed significantly better than Toco with regard to the Contractions Consistency Index (CCI). The mean CCI for EHG was 0.88 ± 0.17 compared with 0.69 ± 0.27 for Toco (P < .0001). In contrast to Toco, EHG was not significantly affected by obesity. CONCLUSION Toco does not correlate well with the gold-standard IUPC and fails more frequently in obese patients. EHG provides a reliable noninvasive alternative, regardless of body habitus.

Monitoring Contractions in Obese Parturients : Electrohysterography Compared With Traditional Monitoring

OBJECTIVE: To compare electrohysterogram-derived contractions with both tocodynamometry and intrauterine pressure monitoring in obese laboring women. METHODS: From a large database of laboring patients with electrohysterogram monitoring, obese subjects were selected in whom data were recorded for at least 30 minutes before and after intrauterine pressure catheter placement for obstetric indication. Using a contraction detection algorithm, the relationship between the methods was determined with regard to both frequency and contraction duration. RESULTS: Of the 25 subjects (median body mass index 39.6 [25th percentile 36.5, 75th percentile 46.3]), seven underwent amniotomy at the time of intrauterine pressure catheter placement. Tocodynamometry identified 248 contractions compared with 336 by electrohysterography, whereas intrauterine pressure catheter monitoring identified 319 contractions compared with 342 by electrohysterography. Using the Contractions Consistency Index, electrohysterogram contraction detection correlated better with the intrauterine pressure catheter (0.94±0.06) than with tocodynamometry (0.77±0.25), P=.004. Electrohysterogram-derived contraction lengths closely approximated those calculated from the intrauterine pressure catheter signal. CONCLUSION: Contraction monitoring routinely is employed for managing labor, and tocodynamometry may be unreliable in obese parturients. In the obese women in this study, the electrohysterogram-derived contraction pattern correlated better with the intrauterine pressure catheter than tocodynamometry. Electrohysterography may provide another noninvasive means of monitoring labor, particularly for those women in whom tocodynamometry is inadequate. LEVEL OF EVIDENCE: II

Spatiotemporal electrohysterography patterns in normal and arrested labor

OBJECTIVE The purpose of this study was to investigate the spatiotemporal patterns of uterine electrical activity in normal and arrested labors. STUDY DESIGN From a database of electrohysterograms, 12 subjects who underwent cesarean delivery for active-phase arrest were each matched with 2 vaginally delivered controls. Using 30-minute segments of the electrohysterogram during the arrest, or the same dilation in controls, the center of uterine electrical activity was derived. The vertical motion of this center of uterine activity was determined for each contraction and the frequencies of movement patterns analyzed. RESULTS Predominantly upward movement of the center of uterine activity (longer and/or stronger contraction at the fundus) was more common with normal dilation (P = .003). Receiver operating characteristic curve analysis gave an area under the curve of 0.91 for predicting outcome (vaginal vs cesarean delivery). CONCLUSION There is a significant correlation between upward movement of the center of uterine activity (fundal dominance) and current labor progress.

Prediction of Intrauterine Pressure From Electrohysterography Using Optimal Linear Filtering

We propose a method of predicting intrauterine pressure (IUP) from external electrohysterograms (EHG) using a causal FIR Wiener filter. IUP and 8-channel EHG data were collected simultaneously from 14 laboring patients at term, and prediction models were trained and tested using 10-min windows for each patient and channel. RMS prediction error varied between 5-14 mmHg across all patients. We performed a 4-way analysis of variance on the RMS error, which varied across patients, channels, time (test window) and model (train window). The patient-channel interaction was the most significant factor while channel alone was not significant, indicating that different channels produced significantly different RMS errors depending on the patient. The channel-time factor was significant due to single-channel bursty noise, while time was a significant factor due to multichannel bursty noise. The time-model interaction was not significant, supporting the assumption that the random process generating the IUP and EHG signals was stationary. The results demonstrate the capabilities of optimal linear filter in predicting IUP from external EHG and offer insight into the factors that affect prediction error of IUP from multichannel EHG recordings

Anesthesia for childbirth: Controversy and change☆☆☆

First introduced to medical practice in 1847, anesthesia for childbirth has undergone constant changes. Current practice reflects evolving social values as well as new discoveries in science and medicine.

Influence of Pulse Oximetry and Capnography on Time to Diagnosis of Critical Incidents in Anesthesia: A Pilot Study Using a Full-Scale Patient Simulator

Objective. Many studies (outcome, epidemiological) have tested the hypothesis that pulse oximetry and capnography affect the outcome of anesthetic care. Uncontrollable variables in clinical studies make it difficult to generate statistically conclusive data. In the present study, we eliminated the variability among patients and operative procedures by using a full-scale patient simulator. We tested the hypothesis that pulse oximetry and capnography shorten the time to diagnosis of critical incidents. Methods. A simulator was programmed to represent a patient undergoing medullary nailing of a fractured femur under general anesthesia and suffering either malignant hyperthermia, a pneumothorax, a pulmonary embolism or an anoxic oxygen supply. One hundred thirteen anesthesiologists were randomly assigned to one of two groups of equal size, one with access to pulse oximetry and capnography data and the other without. Each anesthesiologist was further randomized to one of the four critical incidents. Each anesthetic procedure was videotaped. The time to correct diagnosis was measured and analyzed. Results. Based on analysis of 91 of the subjects, time to diagnosis was significantly shorter (median of 432 s vs. >480 s) for the anoxic oxygen supply scenario (p = 0.019) with pulse oximetry and capnography than without. No statistical difference in time to diagnosis was obtained between groups for the other three critical incidents. Conclusions. Simulation may offer new approaches to the study of monitoring technology. However, the limitations of current simulators and the resources required to perform simulator-based research are impediments to wide-spread use of this tool.

A single dose of fentanyl and midazolam prior to cesarean section have no adverse neontal effects

PurposeAnalgesia and sedation, routinely used as adjunct medications for regional anesthesia, are rarely used in the pregnant patient because of concerns about adverse neonatal effects. In an effort to obtain more information about maternal analgesia and sedation we studied neonatal and maternal effects of iv fentanyl and midazolam prior to spinal anesthesia for elective Cesarean section.MethodsIn this double-blinded, randomized, placebo-controlled trial, 60 healthy women received either a combination of 1 µg·kg-1 fentanyl and 0.02 mg·kg-1 midazolam intravenously or an equal volume of iv saline at the time of their skin preparation for a bupivacaine spinal anesthetic. Sample size was based on a non-parametric power analysis (power > 0.80 and alpha = 0.05) for clinically important differences in Apgar scores. Fetal outcome measures included Apgar scores, continuous pulse oximetry for three hours, and neurobehavioural scores. Maternal outcomes included catecholamine levels, and recall of anesthesia and delivery.ResultsThere were no between-group differences of neonatal outcome variables (Apgar score, neurobehavioural scores, continuous oxygen saturation). Mothers in both groups showed no difference in their ability to recall the birth of their babies.ConclusionsMaternal analgesia and sedation with fentanyl (1 µg·kg-1) and midazolam (0.02 mg·kg-1) immediately prior to spinal anesthesia is not associated with adverse neonatal effects.RésuméObjectifĽanalgésie et la sédation, complément habituel à ľanesthésie régionale, sont rarement utilisées chez la femme enceinte parce qu’on craint les effets néonatals indésirables. Pour en savoir davantage sur ľanalgésie et la sédation de la mère, nous avons étudié les effets sur la mère et ľenfant du fentanyl et du midazolam iv administrés avant la rachianesthésie pour césarienne.MéthodePour ľétude randomisée, à double insu et contrôlée contre placebo, 60 femmes en santé ont reçu une combinaison intraveineuse de 1 µg·kg-1 de fentanyl et 0,02 mg·kg-1 de midazolam ou un volume égal de solution saline iv au moment de préparer à la rachianesthésie avec bupivacaine. La taille de ľéchantillon reposait sur une analyse de puissance non paramétrique (puissance > 0,80 et alpha = 0,05) pour des différences cliniquement importantes ďindices ďApgar. Les mesures de ľévolution du fœtus comprenaient ľindice ďApgar, la sphygmo-oxymétrie continue pendant trois heures et les scores neurocomportementaux. Ľévaluation de la mère incluait les niveaux de catécholamine et la présence de souvenir de ľanesthésie et de ľaccouchement.RésultatsIl n’y a pas eu de différence intergroupe des variables mesurées chez le nouveau-né (indice ďApgar, comportement neurologique, mesure continue de la saturation en oxygène). Les mères des deux groupes ont montré la même capacité à se rappeler la naissance de leurs enfants.ConclusionĽanalgésie et la sédation maternelles avec du fentanyl (1 µg·kg-1) et du midazolam (0,02 mg·kg-1) administrées immédiatement avant la rachianesthésie ne sont pas associées à des effets néonatals indésirables.

Modeling obstetric cardiovascular physiology on a full-scale patient simulator.

To our knowledge, this is the first attempt at adapting an existing cardiovascular model to simulate the hemodynamics of a particular patient population. Despite attempts to define the physiologic alterations in advance, we discovered there were critical parameters not completely defined in the literature. These were discovered through the iterative process of testing, comparing resulting vital signs with targets, and literature review. A list of the parameters that should be sought for future modeling efforts is provided (Table 3), but this list is by no means exhaustive. As further work is performed in this area, additional independent and essential parameters will be identified (pressure characteristics of valvular anomalies, for example). To define a physiology that is less well described in the literature, empirical alterations and best-guess estimates of parameter changes will be required with significantly more iterations. Finally, we have described only modeling of cardiovascular physiology, modeling the respiratory system will require a similar process.

Teaching respiratory physiology: clinical correlation with a human patient simulator.

In recent years students have increasingly objected to laboratory exercises involving animal subjects. We have replaced the valuable animal experiments with demonstrations using a full-scale human patient simulator. In small groups first-year medical students observe realistic clinical situations such as opioid-induced hypoventilation, pneumothorax, and pulmonary edema. Students obtain information through physical examination, arterial blood gas analysis and chest radiography. They practice interventions such as providing supplemental oxygen and mask ventilation, monitor the results, and develop a basic differential diagnosis and treatment plan. We utilize the clinical context to review fundamental concepts of respiratory physiology including the alveolar air equation and oxyhemoglobin dissociation curve. The students give these laboratory exercises uniformly superior evaluations.

Problem-Based Learning in Residency Education: A Novel Implementation Using a Simulator

Background. We developed a problem-based learning exercise with a full-scale human patient simulator to teach residents the emergency management and differential diagnosis of acute intraoperative hypotension. Methods.We developed the exercise through the following steps: clear definition of learning objectives, preparation of an appropriate case stem, development of clinically realistic scenarios to illustrate objectives, and an interactive instructor to stimulate discussion. Results. The exercise focused on the differential diagnosis of intraoperative hypotension, and the acute treatment of hypovolemia, cardiac tamponade, tension pneumothorax, and anaphylaxis. Conclusions. Exercises on a full-scale patient simulator are a natural extension of problem-based learning. Recent research in learning theory provides the rationale for this teaching modalitys potential as a learning tool.