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From the *Department of Anesthesiology, General Clinical Research Center, Yale University School of Medicine and Yale-New Haven Hospital, New Haven, Connecticut.
Address correspondence and reprint requests to Paul G. Barash, MD, Department of Anesthesiology, Yale University School of Medicine, 333 Cedar Street, PO Box 208051, New Haven, CT 06520-8051. Address e-mail to paul.barash{at}yale.edu.
Abstract
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.
Prolonged waiting time in health care settings is not desirable, as it generates patient stress and dissatisfaction, increases the cost of seeking medical care, and is a barrier to health care access (1). In the perioperative setting, patients, surgeons and anesthesiologists expect the actual time of start of surgery to be consistent with the start time indicated by the operating room (OR) schedule. Indeed, if individuals distrust the OR schedule, a "snowball effect" may occur and people will be arriving late in reaction to the other people being expected to be late (2). That is, once surgeons realize that the schedule they were provided is inaccurate, they will react by being late to the OR themselves. Consistent with the above, Vitez and Macario (3) found, in a survey study, that surgeons consider "timely starts" as one of the most important factors in satisfaction related to OR activities. In fact, a timely start was rated almost as important by surgeons surveyed as the ability to calmly manage a crisis.
Multiple issues determine whether the actual OR schedule on a given day will follow the planned OR timetable of that day. Although some factors, such as emergency and add-on cases, are unpredictable, other factors, such as the length of various components of anesthesia and surgical cases, should be predictable (4–6). Indeed, scheduling a case in the OR should consider the anesthesia release time (ART), the surgery preparation time (SPT), the surgical procedure time, and the turnover time of an OR. Currently, data are lacking regarding ART and SPT for surgical procedures involving children. Furthermore, all previous studies used computerized databases to address this question (7,8).
This prospective cross-sectional study assessed ART and SPT for surgical procedures involving children ages 3 days to 18 yr. Unlike previous studies, however, this investigation used four trained independent observers to assess the actual ART and SPT and the factors influencing these variables in children undergoing anesthesia and surgery.
METHODS
After protocol review by the Human Investigation Committee, an exemption of informed consent was granted and all guidelines for confidentiality were followed. This observer-based prospective study was performed at Yale-New Haven Children’s Hospital ORs (n = 5) serving both inpatient and outpatient children from August 2002 to December 2002. Inclusion criteria included patients ASA physical status (PS) I through IV scheduled for elective surgical procedures. Exclusion criteria for the study were: emergency surgical procedures, ASA PS V, previously tracheally intubated patients, or those having an artificial airway on arrival to the OR.
Data were recorded on a standardized form by trained observers who were not involved in patient care. These trained observers were instructed by two of the authors (AE, ED) using a formal syllabus and a 2-wk instructional period in the OR. After this initial training period, inter-rater and intra-rater reliability were assessed. Also, to prevent bias, observers were rotated through each of the 5 ORs with an assignment sequence based on the use of a random number generator. The observers were in place for each study before the patient entered the OR and left the OR after skin incision. Observers stationed themselves in the OR so as not to be obtrusive and yet close enough to be able to observe and hear all the events that took place in the OR. A pilot study was used (n = 169 patients) to determine if any logistical or data recording methods required revision. No pilot data were used in the compilation and analysis of the study data.
Overall, definitions of clinical practice were based on the standardized definitions of the Association of Anesthesia Clinical Directors (9). The study period was defined as the point at which the patient was placed on the OR table (time zero) until the skin incision was made or a procedure started by the surgeon (e.g., endoscopy). This time period was subdivided into two phases: ART and SPT. ART was defined as the time at which the patient had a sufficient level of anesthesia established to begin the surgical preparation and the remaining anesthesia tasks did not preclude positioning and surgical preparation. When possible, objective end-points of ART were used to determine the completion of this phase, e.g., endotracheal intubation. SPT was defined as the time from the ART until a skin incision was made or a painful stimulus occurred, such as introduction of a cystoscope. Case length (CL), was defined as the time from skin incision until completion of the application of the dressing in the OR. ART, SPT, and incision time were measured by use of a stopwatch and are reported in minutes with start equal to time zero. Specific time-related details of the study period, such as induction and tracheal intubation time, times for placement of regional anesthetics, times for placement of invasive hemodynamic monitors, teaching time, and the time of various delays were recorded on the data sheet in units (1 U = 5-min time interval). In addition, variables such as age, weight, ASA PS, gender, type of patient admission (i.e., inpatient, outpatient), surgical procedure, and surgical service were documented. Anesthesiologist-related factors such as coverage ratio (i.e., number of ORs per attending), residents’ training level, type of anesthetic technique used, type of artificial airway, and invasive monitoring were recorded.
The sample size for this study met standards for simple random sampling as recommended by the Joint Commission on Accreditation of Healthcare Organizations (10). After data collection, data were read by an optical scanner and stored in Microsoft Access 2000. All data were reviewed sequentially by two investigators before entry and inquiries regarding errors or outliers were resolved on a weekly basis. Data were analyzed using SAS statistical software (version 8.12; Cary, NC). Except where noted, data are expressed as mean ± sd. The entire data set was initially investigated with descriptive statistics including Pearson correlation coefficients. Analysis of variance with Tukey’s HSD was used to determine significant between-group differences. A level of P < 0.05 was considered significant.
RESULTS
Data regarding 656 pediatric patients undergoing a variety of inpatient and outpatient surgical procedures were collected. Table 1 lists demographic characteristics of the study population. The overall ART was 11.0 ± 9.7 min with a 25%–75% semi-interquartile range of 6 to 12 min. The overall SPT was 11.1 ± 10.0 min with a 25%–75% interquartile range of 4 to 15 min. As can be seen from Table 2, there was a strong association between CL and SPT (r = 0.64; P = 0.01) and ART (r = 0.84; P = 0.001). The percentage of ART + SPT of the total CL was 30% ± 14%. The proportion of ART to ART + SPT was 53% ± 19%. That is, ART was approximately equal to SPT.
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We found that there is significant variability in ART as a function of the surgical service. Patients undergoing cardiothoracic surgery required the longest ART (37 ± 21 min) (Table 2). In contrast, patients undergoing otolaryngological operations required the shortest ART (8 ± 4 min) (analysis of variance; P = 0.001). Similar trends were seen with SPT (Table 2). Also, ART in patients classified as ASA PS III–IV differed significantly from the ART of patients with ASA PS I and II (Table 3)(P = 0.0001). Examination of ART as a function of age indicated that younger children had a significantly longer ART as compared with older children (P = 0.001) (Table 3).
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Table 3 also demonstrates the impact of various anesthetic techniques on ART. That is, ART ranges from 7 ± 7 min (for mask anesthesia) to 52 ± 18 min (general anesthesia, tracheal intubation, and invasive monitoring). ART and SPT increase as the CL increases (Table 4). Further, the percentage of ART and SPT decreased significantly as the total CL increases (Table 4). Overall we found that ART was 16% ± 10% (range, 8%–21%) of the CL. This proportion differed significantly based on CL. In cases that lasted longer than 120 min the percentage was 9% ± 6%, whereas the percentage for cases that lasted <15 min was 27% ± 15% (Table 4). ART also differed significantly based on the origin of admission of patient. That is, the ART of inpatients was significantly longer when compared with the ART of same-day admission and outpatients (18 ± 18 min versus 12 ± 12 min versus 11 ± 9 min; P = 0.02).
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ART was significantly longer for the first scheduled case of the day (15.5 ± 6 min versus 10 ± 8 min; P = 0.0001) compared to all subsequent cases. Closer examination revealed that the first case of the day involved more complex cases, as evidenced by longer surgical time (P = 0.001).
Finally, we found that room converge ratio by the attending anesthesiologist did not influence ART (P = not significant). That is, attendings with 1:1 coverage did not differ from attendings with 1:2 coverage (11 ± 10 min versus 11 ± 8 min; P = 0.54). Similarly, year of training of the anesthesia resident did not impact ART (P = not significant), even after controlling for ASA PS and surgical service. It should be noted, however, that only CA2 and CA3 residents rotate through Yale-New Haven Children’s Hospital ORs.
DISCUSSION
The results of this study indicate that ART varies based on the anesthetic technique used, type of surgery performed, age, ASA status, and the category of patient’s admission (inpatient versus outpatient). We found that the semi-interquartile range for ART was 6 to 12 minutes and that ART constitutes on the average 16% of total CL. Contrary to common belief, we found that ART contributes to only 50% of the entire preincision period. Thus, anesthesiologists are not even in total control of the time period before skin incision. We also found that although ART increases as CL increases, the percentage of ART of the total CL decreases. This is the first study that measured ART using an independent observer who collected data regarding potential variables that influence the ART.
Multiple OR scheduling systems have a feature that calculates the average surgical CL based on the record of the particular surgeon. For example, the ORIS® scheduling system calculates the average length of the last 13 surgical procedures performed by an individual surgeon and enters those data automatically into the surgical procedure duration field at the time of scheduling a case. In many ORs, however, the scheduler then adds a "constant" amount of time to allow for anesthesia-controlled time and SPT. This constant is not typically based on any objective data and thus there is a need for reality-based guidelines with regard to ART and SPT in children undergoing surgery (11).
We found that ART varies based on the anesthetic technique used, type of surgery performed, age, ASA PS, and type of patient admission. This is not surprising and is in line with common clinical observations. Also contrary to common belief, we found that ART is only approximately 15% of total CL and ART is only 50% of preincision time. These findings may be of interest to hospital administration, surgeons, and nurses. Indeed, meaningful improvements in OR efficiency can be made only by a multidisciplinary effort among surgeons, anesthesiologists, and nurses. Although SPT correlates with ART, ART has no causal effect on SPT. Other factors such as severity of patient illness or complexity of surgical procedure have affected both ART and SPT.
Finally, methodological issues related to the design of this study have to be addressed. At the onset of this cross-sectional study, four techniques of data collection were considered: self-reporting by the OR personnel, data obtained from an OR information system, video recordings in ORs, and the use of trained observers. Recording of study data by individuals involved in direct clinical care has been shown to cause multiple inaccuracies in data collection (12,13). Self-reporting methodology is reported to be associated with a 23% rate of incorrectly or partially completed forms and an overall compliance rate for completion of the forms of approximately 60%. Videotaping might be considered to be too intrusive in an OR and may actually be less accurate when compared with an observer-based system (14). We considered using the OR database. This method, however, uses data that are collected by caregivers and thus are limited by the issues addressed above. We felt that using trained independent observers combined with the use of a standard curriculum, practice observation sessions, and inter-observer comparisons was the best way to assure of the validity the data collected (15). Other additional limitations of the study need to be noted. That is, we did not collect data on variables such as parental presence or the use of sedative premeditation that may affect the length of induction of anesthesia.
In conclusion, this study has documented ART and SPT in children undergoing surgery. We found that ART ranges from 6 to 12 minutes and that ART constitutes only approximately 16% of total CL. Finally, ART constitutes only approximately 50% of the total time before skin incision. Incorporation of these data into the OR schedule will result in increased accuracy as well as increased surgeon, anesthesiologist, and patient satisfaction.
ACKNOWLEDGMENTS
The authors wish to acknowledge the continuing support of Mr. Norman Roth, Senior Vice President, Yale-New Haven Hospital. In addition, we wish to recognize the assistance of our Operating Room colleagues in the Departments of Anesthesiology, Nursing and Surgery.
Footnotes
Accepted for publication May 30, 2006.
Supported, in part, by Yale-New Haven Hospital: Educational Grant. GSF is supported by the National Institutes of Health (NCRR MO-1 RR00125); Bethesda, Maryland. ZNK is supported by the National Institutes of Health (NICHD, R01HD37007-02), Bethesda, Maryland.
REFERENCES
This article has been cited by other articles:
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  F. Dexter and R. E. Wachtel Economic, Educational, and Policy Perspectives on the Preincision Operating Room Period Anesth. Analg., October 1, 2006; 103(4): 919 - 921. [Full Text] [PDF]
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