Jan Ehrenwerth

Facilitation of fiberoptic orotracheal intubation with a flexible tracheal tube

Advancement of a tracheal tube (TT) over a flexible fiberoptic bronchoscope (FOB) is often impeded by obstruction at the arytenoid cartilage or epiglottis. We tested the hypothesis that the use of a flexible, spiral-wound TT, rather than the standard, preformed TT would facilitate tube passage into the trachea over the FOB. Forty patients scheduled to undergo general anesthesia with tracheal intubation were randomized to two groups. Then the trachea was intubated with a FOB, followed by passage of either a standard, preformed TT or a flexible, spiral-wound TT over the FOB. Ease of TT advancement over the FOB into the trachea was graded on a 1 (easy) to 3 (difficult) scale, and differences between the two groups were compared with X1 analysis. The overall scores were compared with Wilcoxons ranked sum test. Statistical significance was defined as P < 0.05. In patients randomized to the regular TT, only 35% (7/20) of first attempts to advance the TT over the FOB were successful. In the patients randomized to the spiral-wound TT, 95% (19/20) of first attempts were successful (P < 0.0001). Of the 13 regular TTs that were not successfully advanced on the first attempt, seven could not be passed after the second or third attempt (necessitating the use of the cross-over spiral-wound TT). In the only instance in which a spiral-wound tube was not successfully passed into the trachea on the first attempt, passage also was not achieved after the second or third attempt. The median scores for ease of tracheal passage (and 25–75 percentiles) were 2 (1–3) when the initial attempt was with the regular TT and 1 (1–1) when the initial attempt was with the spiral-wound TT (P < 0.0002). The authors conclude that a spiral-wound, wire-reinforced TT is less likely to encounter obstruction on glottic structures than its preformed counterpart. We attribute this difference to the greater side-to-side flexibility of the spiral-wound tube when compared with the preformed tube. This increased flexibility allows the spiral-wound tube to bend more easily and thus conform to the acute angle which the stenting FOB may develop in the posterior pharynx. An additional advantage may be conferred by the more obtuse angle of the wire-reinforced TTs distal end, making it less likely to impinge on pharyngeal soft tissue during its advancement into the trachea.

Anesthesia equipment : principles and applications

Design features system monitors patient monitors hazards and safety features maintenance/quality assurance special situations.

Stimulation with submaximal current for train-of-four monitoring.

The present study evaluated responses to train-of-four (TOF) stimulation at a range of stimulating currents. Traditionally TOF has been applied with a supramaximal stimulus but this may be quite uncomfortable for the awake patient. In the first part of this study, 12 healthy volunteers quantified (by 10-cm visual analog scale) the discomfort associated with TOF stimulation at 20, 30, and 50 mA. The median VAS scores were 2, 3, and 6, respectively (P less than 0.05 for differences between each group). In the second part, single twitch and TOF responses were compared at 20, 30, and 50 mA in 64 postoperative and in 19 intraoperative patients who had ratios of the fourth to the first twitch (T4/T1) ranging from 0.15-1.03. In all patients, neuromuscular responses to nerve stimulation were recorded by a mechanogram, and the T4/T1 ratios were calculated. Although single twitch heights increased significantly as amperage was increased, there was no statistical difference in the T4/T1 ratios at the three different currents. The mean +/- SD T4/T1 ratios at 20, 30, and 50 mA were 0.795 +/- 0.247, 0.798 +/- 0.237, and 0.802 +/- 0.233, respectively (P = ns). It is concluded that TOF monitoring using a submaximal stimulus is more comfortable for the awake patient who is suspected of residual weakness, and that T4/T1 testing can be reliably accomplished intraoperatively as well as postoperatively using submaximal stimuli.

Assessment of residual curarization using low-current stimulation.

The present study employed train-of-four (TOF) stimulation at à current of 20 mA to assess the incidence and degree of residual neuromuscular blockade in 64 randomly selected Post Anesthesia Care Unit (PACU) patients. Group C (Control, n = 10) had received anaesthesia without nondepolarizing muscle relaxant; Group V (n = 25) had received vecuronium; and Group P (n = 29) had received pancuronium. At the end of surgery, each patient had been considéréd by his anaesthetist to have adequate neuromuscular function on the basis of clinical signs and tactile or visual evaluation of responses to TOF stimulation. However, upon testing in the PACU 15 min later, 45% (13 of 29) of Group P patients and 8% (2 of 25) of Group V patients had à TOF ratio < 0.70. This study indicates that residual curarization may be commonly encountered following long-acting relaxants despite qualitative intraoperative TOF monitoring. The present incidence, detected at à current of 20 mA, is consistent with previous reports which employed supramaximal TOF stimulation. We conclude that despite intraoperative monitoring, residual curarization following long-acting nondepolarizing agents is common and that it may be detected with TOF at à low stimulating current (20 mA).RésuméLa présente étude à utilisé l’ondée-de-quatre (TOF) avec des courants de 20 mA afin d’évaluer l’incidence et le degré de blocage neuromusculaire résiduel chez 64 patients choisis au hasard dans l’unité des soins postanesthésiques (PACU). Le groupe C (Contrôle, n = 10) à reçu de l’anesthésie sans relaxant musculaire nondépolarisant; le Groupe V (n = 25) à reçu du vécuronium; et le Groupe P (n = 29) à reçu du pancuronium. A la fin de la chirurgie, chaque patient fut considéré par son anesthésiste comme ayant une fonction neuromusculaire adéquate sur la base des signes cliniques tacliles et les évaluations visuelles des réponses de la stimulation avec une ondée-de-quatre. Cependant, lors de la stimulation au PACU 15 minutes plus tard, 45% (13 de 29) du Groupe de patients P et 8% (2 de 25) avaient un ratio de TOF < 0,70. Cette étude indique que la curarisation résiduelle peut survenir fréquémment après les relaxants à tongue action malgré une surveillance qualitative intraopératoire du TOF. L’ incidence trouvée, détectée avec un courant de 20 mA, est en accord avéc des études antérieures qui émploient la stimulation supramaximale de TOF. On conclut que malgré une surveillance intraopératoire, la curarisation résiduelle après des agents non-dépolarisants à longue action est fréquente et qu’elle pourrait être détectée par une stimulation avec un TOF avec un courant de 20 mA.

Task analysis of the preincision surgical period: an independent observer-based study of 1558 cases.

Intense production pressure has focused on the preincision period (from patient-on-table to incision) as an important component of overall operating room efficiency. We conducted a prospective study in which trained independent observers measured the performance of anesthesiologists, surgeons, and nursing staff to determine anesthesia release time (ART, patient-on-table until release for surgical preparation) and surgical preparation time (SPT, start surgical preparation to incision) and the factors, including delays, that affect their duration. We enrolled 1558 patients undergoing elective surgery in a tertiary medical center. The mean ART was 21 ± 16 min. Mean SPT was 22 ± 13 min, and mean case length was 207 ± 123 min. Significant variation was seen in both ART (range, 1–115 min) and SPT (range, 1–130 min). Multivariate regression analysis revealed ASA physical status, age, level of resident training, invasive monitoring, case length, and case number in the room were all positive predictors of ART duration (P < 0.05). In contrast, gender, body mass index, number of anesthesia personnel concurrently in the room, and number of rooms covered per anesthesia attending were not predictors for ART (P > 0.05). Delays affected both ART and SPT and were encountered in 24.5% of all procedures (surgery 66.8%, anesthesiology 21.7%, and logistical 11.5%). For operating room scheduling purposes, we conclude that assigning a constant fixed duration for anesthetic induction is inappropriate and will result in creating erroneous administrative expectations.

Resident Teaching Versus the Operating Room Schedule: An Independent Observer-Based Study of 1558 Cases

Efforts to improve operating room efficiency may threaten clinician training. Therefore, we designed a prospective, observational study to determine the actual time spent teaching anesthesiology residents during the interval from patient-on-table to skin incision and to determine whether anesthesia teaching in the peri-induction period increases the time to surgical incision. This study was conducted in an inpatient operating room suite of a tertiary academic medical center. Of 1558 cases examined, 75% had an element of teaching (mean percent teaching per case = 46.4). A 33% decrease in teaching occurs when the attending anesthesiologist concurrently directed care in 2 rooms (P < 0.001). The percent teaching significantly increased as a function of ASA physical status classification and time of day of surgical case (P = 0.001). Teaching accounted for a mean increase of time to incision of 4.5 ± 3.2 min, but represented only 3% of the mean surgical case length (207 ± 132 min). We conclude that teaching occurs in the majority of cases in the operating room and although it contributes to increased time to incision, this increase is insignificant compared with the time required to complete the surgical procedure.

Can the attending anesthesiologist accurately predict the duration of anesthesia induction

In a prospective, observational study, the attending anesthesiologists’ prediction of anesthesia release time (ART) of the patient to the surgical team was highly correlated with actual ART (r = 0.77; P ≤ 0.001). However, this was true only in the aggregate (n = 1265 patients). Indeed, offsetting degrees of under- and over-predicting (24% each) reduced accuracy to only 53% per individual case. For example, under-prediction was associated with ASA physical status IV, a regional anesthetic technique, age >65 yr, and the use of invasive hemodynamic monitoring (P = 0.006). In fact, as the degree of case difficulty increased, the correlation coefficient between predicted and actual ART decreased, indicating a poor predictive value with more difficult inductions (r = 0.82 to r = 0.44; P ≤ 0.004). We conclude that knowledge of the presence of specific factors that lead to inaccurate predictions of time required for induction of anesthesia may enhance the accuracy of the operating room schedule.

Electrical safety in the operating room: important old wine, disguised new bottles

A nesthesia and surgery are conducted in technologically intense environments that are always potentially hazardous. Despite this, anesthesiologists are rarely forced intraoperatively to confront electrical safety problems, especially microshock. However, in this issue McNulty et al. (1) report two cases of microshock conducted via a pulmonary artery (PA) catheter. The authors deserve commendation for their rapid diagnosis and treatment of two situations of cardiac microshock, whose occurrence is rare but whose nature is very well known. Anesthesiologists are commonly concerned about fibrillation and dysrhythmia occurring during unipolar electrosurgery in patients with implanted, programmable cardiac pacemakers. Indeed, the most common piece of medical equipment to affect pacemaker function is unipolar electrosurgery (2). McNulty et al. emphasize, however, that patients having a PA catheter in place are always potentially susceptible to electrosurgically caused cardiac microshock, because of the PA catheter’s wire (on the way to the thermistor) that passes through the heart. The type of emergency that McNulty et al. dealt with probably occurs less frequently than intraoperative malignant hyperthermia (MH). However, both MH and cardiac microshock are examples of crises that anesthesiologists are expected to recognize and treat, although many will never encounter either one. Curiously, although many anesthesiologists have no trouble becoming interested in new concepts related to the diagnosis and treatment of malignant hyperthermia, few anesthesiologists exhibit excitement about being refreshed with new aspects of electrical safety. The vaison d‘2tre for this editorial should now be apparent. Anesthesiologists should be encouraged to benefit from the observations of McNulty et al. and use these two cases as reminders of old and new issues in operating room electrical safety (3-9). Microshock current was induced in the PA catheters of McNulty et al. because of capacitive coupling (a

Task analysis of the preincision period in a pediatric operating suite: an independent observer-based study of 656 cases.

We designed this cross-sectional investigation to assess anesthesia release time (ART = patient-on-table until release for surgical preparation) and surgical preparation time (start of surgical preparation to incision) of children undergoing anesthesia and surgery (n = 656). Data collected by trained independent observers included variables such as age, ASA physical status, anesthetic technique, and placement of invasive monitoring. We found that mean ART was 11.0 ± 9.7 min and the mean surgical preparation time was 11.1 ± 10.0 min. Also, ART ranged from 7 ± 7 min (for mask anesthesia) to 52 ± 18 min (general anesthesia/endotracheal tube and invasive hemodynamic monitoring). The percentage of ART of the total case length was 15% ± 7%, with a wide variability depending on the total case length. We also found that there is a significant variability in ART as a function of the surgical service involved (analysis of variance; P = 0.0001), ASA physical status (P = 0.0001), and age. For example, younger children had a significantly longer ART as compared with older children (P = 0.001). Room coverage ratio by the attending anesthesiologist and training level of the anesthesia resident did not impact ART (P = not significant). We conclude that ART in children undergoing surgery is highly variable and is a function of factors such as the surgical service involved, age of the child, and ASA physical status of the child. These factors should be considered when scheduling a surgical case.

Pressure-support ventilation in the operating room: do we need it?

UNDOUBTEDLY, many readers will find it curious to see an article summarizing perceptions of teamwork in the operating room (OR) in ANESTHESIOLOGY, a journal typically filled with anesthesia-related clinical and biomedical science. Although we would hopefully all agree that teamwork is important in the increasingly complex OR environment, many will wonder how subjective perceptions of teamwork can be turned into a metric useful in improving care. And, most important, how can such seemingly vague assessments of teamwork ultimately benefit our patients? Concern about teamwork in complex healthcare settings is not new. The now-familiar 1999 Institute of Medicine report, which highlighted anesthesiology’s progress and leadership in patient safety, recommended that healthcare organizations enhance their patient safety culture, in which “effective team functioning” was identified as one of five principles for creating safe hospital systems. In response, at least nine surveys purporting to measure patient safety climate have emerged, of which the Safety Attitudes Questionnaire (SAQ) seems most robust. A modification of a survey developed for critical care settings from an aviation survey, SAQ is a 30-question survey designed for intrainstitutional and interinstitutional comparisons. Its six domains—teamwork climate, safety climate, job satisfaction, perceptions of management, stress recognition, and working conditions—reflect distinct dimensions based on studies in aviation and health care. Higher SAQ scores have been associated with shorter duration of stay, fewer medication errors, and lower bloodstream infection and ventilator-associated pneumonia rates, as well as lower nurse turnover and risk-adjusted patient mortality rates. The article in this issue of ANESTHESIOLOGY evaluates how well the teamwork climate domain in an SAQ version enhanced for OR personnel reflects the personnel’s perceptions of teamwork climate, which is defined here as the quality of collaboration among those in the work setting. Measuring teamwork climate is challenging principally because it is a concept or construct that cannot be measured directly; instead, it is assessed indirectly by asking, in this case, 6 of the 30 questions (or “items”) in the SAQ survey (or “instrument”). The responses to the 6 questions are converted to numerical scores that, in turn, are combined and arrayed on a 0–100 scale as a “domain score.” Although the methodology presented may seem arcane, it relies on the same item-measurement theory on which more familiar generic and disorder-specific quality-of-life scales (e.g., Medical Outcomes Study Short Form-36 Health Survey, visual analog scale for pain) are based. If the items have been selected appropriately and the scaling has been done properly, the resulting domain scores should reflect the underlying construct, should differ in a given circumstance by only random error of measurement, and should have important properties that provide the basis for the evaluation. Among those properties is coverage of the construct: All aspects of teamwork climate that are meaningful to OR personnel should be addressed. This seems to have been satisfied in the development of the modified SAQ through the use of literature review, focus groups, behavioral observation of OR personnel, and critiques of the draft survey by OR personnel. A second property is reliability, which in its most general usage is the consistency of a measurement under constant conditions. For this instrument, two specific types of reliability were tested: Internal reliability, or the consistency with which raters used the 6 items in making their assessments of teamwork climate, was evaluated using Cronbach’s , whose values were uniformly high for the different caregiver types. Consistency with which personnel of each type made their assessments was determined with an intraclass correlation coefficient, whose values were similarly high. The third property is validity, a multidimensional characteristic that, overall, means the domain measures what it is claimed to measure. Given the absence of an existing teamwork metric for use as a comparator, it is not possible to explore correlations with other ways to measure teamwork; therefore, we cannot assess convergent, criterion, or discriminant validity. Potential users of this instrument will be especially interested in its ability to satisfy a fourth property, sensitivity: the instrument’s ability to reflect true differences in teamwork climate. The investigators used the instrument in 60 hospitals in a large health system, achieved high participation rates among all OR personnel types, and found widely varying perceptions of “good teamwork climate” by hospital. All respondents in 6 hospitals agreed that a good teamwork climate was present, whereas in the majority of study hospitals, less than 50% of respondents shared that assessment. Given aforementioned psychometric characteristics, this pheThis Editorial View accompanies the following article: Sexton JB, Makary MA, Tersigni AR, Pryor D, Hendrich A, Thomas EJ, Holzmueller CG, Knight AP, Wu Y, Pronovost PJ: Teamwork in the operating room: Frontline perspectives among hospitals and operating room personnel. ANESTHESIOLOGY 2006; 105:877–84.