Pediatr Radiol (1995) 25:344-346

Pediatric Radiology 9 Springer-Verlag 1995

Reduced need for sedation in patients undergoing helical CT of the chest and abdomen K. S. White University of Washington School of Medicine, Children's Hospital and Medical Center, Seattle, Washington, USA Received: 18 May 1994/Accepted: 22 June 1994

Abstract. Since 15 July 1993, we have used helical CT

exclusively in chest and abdomen exams. The purpose of this study was to compare sedation rates in children undergoing conventional and helical CT of the chest and abdomen. Data for all CT examinations of the head (n=1121), chest (n=427), and abdomen (n = 315) performed between 1 April 1993 and 31 October 1993 were evaluated. Examinations were divided by anatomic site, patient age, date, whether motion was noted in the radiology report, and whether or not sedation was used. The oldest patient requiring sedation was 5 years old. All examinations in patients 5 years old or less (n = 1048) formed the study group. Because no head CT examinations were done helically, this constituted a control group. Comparisons of motion and sedation rates before and after 15 July 1993 were made with the )~2 test. There was no statistically significant difference in the sedation rate in the control group (patients having conventional head CT examinations). In contrast, the use of helical technique for chest and abdomen CT coincided with a reduction of the sedation rate from 18 % to 10 % (P = 0.3). There was no statistically significant difference in reported motion for either head or chest/abdomen examinations over the study period. The implementation of helical CT coincided with a 45 % reduction in the sedation rate of patients undergoing CT of the chest and abdomen. At the current volume of CT examinations at our institution, this decrease would result in an estimated 60 fewer sedations per year. The use of oral and intravenous sedation has become standard practice in many diagnostic imaging departments that care for children. The administration of sedation in CT, MRI, nuclear medicine and interventional/ vascular radiology allows most diagnostic imaging procedures to be performed without the need for general Correspondence to: K. S. White, Department of Radiology, Primary Children's Medical Center, 100 North Medical Drive, Salt Lake City, UT 84113, USA

anesthesia. The widespread adaptation of this approach to imaging uncooperative children has not been without controversy. Concerns over the lack of standards for patient assessment, drug choice and dosage, patient monitoring, and follow-up have recently appeared in the literature [1-5]. Although sedation is generally considered safe when administered under appropriate guidelines, there is a small risk of adverse effects including allergic reaction, respiratory depression, aspiration and death. Administration of sedation significantly increases time requirements and costs of diagnostic procedures and is generally associated with some added discomfort to the child. Therefore, reduction in sedation rates is an important area of investigation in pediatric imaging. The recent development of helical, spiral or volumetric CT scanning has been considered a potential means of reducing sedation requirements in pediatric CT. Although there have been reports of a subjective decrease in sedation requirements in imaging the head [6] and temporal bone [7] with helical CT, no objective assessment of this effect has ever appeared in the literature. Since July 1993, we have routinely applied the helical technique in all CTexaminations of the chest and abdomen. The purpose of this retrospective study was to quantitate the effect of using helical technique on sedation rate in children undergoing CT examinations of the chest and abdomen. We hypothesized that the use of helical CT would be associated with a decreased rate of sedation as compared with a group of age matched controls undergoing conventional CT. Materials and methods Records for all children undergoing CT of the head, chest and abdomen between I April 1993 and 31 October 1993 were retrospectively reviewed. All examinations were performed on a GE High Speed Advantage helical CT scanner (GE Medical Systems, Milwaukee, Wisc.). Patient age, examination type, examination date and whether sedation was used were recorded in a database using Excel software (Microsoft, Redmond, Wash.). Under departmen-

345 tal protocol, all head CT exams were performed with conventional technique over the entire study period. Between 1 April 1993 and 15 July 1993 all chest and abdomen CT studies were done conventionally as well. On 16 July 1993 departmental protocol was changed and all examinations of the chest and abdomen were performed with helical technique. All patients were imaged under the same departmental sedation policy. This sedation protocol was established in collaboration with the department of anesthesia. Patients were selected to receive sedation following a trial of having the patient lie on the CT table in preparation for the study. If the patient could hold still for the estimated duration of~the acquisition phase of the scan, no sedation was given. All sedation candidates with a history of airway occlusive disease or congenital airway anomaly were referred to anesthesia for evaluation. All other patients who were unable to hold still for the estimated duration of the scan were sedated with either oral chloral hydrate (50-100 mg/kg) or intravenous pentobarbital (2-3 mg/kg bolused to a maximum of 8 mg/kg total dose). Prior to administration of sedation, a baseline blood pressure, heart rate, respiratory rate and history and physical examination were performed. The patients were to have nothing by mouth for the 6 h preceding the sedation. While sedated, patients underwent continuous monitoring of heart rate, respiratory rate and oxygen saturation with pulse oximetry. All CTreports were archived on an ADAC MARS II radiology information system (ADAC Laboratories, Milpitas, Calif.). A computer search was conducted to identify all studies in which the words "artifact", "suboptimal", "movement" or "motion" were encountered in the body or impression of the report. These reports were then printed and reviewed to identify cases in which the quality of the examination was compromised by patient motion. Examinations were grouped by anatomic location (head or chest/abdomen) and date of study (before 16July 1993, after 16 July 1993). The age distribution of each group was compared with an unpaired t-test. Sedation rates and rates of motion-related artifacts were compared with the Xz test. Statistical analysis was performed with Statview software (Abacus Concepts, Inc.) running on a Macintosh personal computer (Apple Computer, Cupertino, Calif.).

Results A total of 1121 CT examinations of the head and 742 exams of the chest or a b d o m e n were performed over the 6-month study period. The oldest patient requiring sedation was 5 years old. O f patients 5 years and under, 697 underwent head CT and 351 had chest or a b d o m e n CT. This subset of 1048 patients under 6 years of age constitutes the study group. There was no statistically significant difference between m e a n age of patients studied before (mean age 17 months) and after (mean age 16 months) the protocol change (P = 0.4). As expected, patients requiring sedation were younger (mean 6 months) than patients not requiring sedation (mean 17 months) (P < 0.0001). The incidence of motion artifacts and sedation rates for patients undergoing CT examinations are given in Table 1. Using the X2 distribution there was a statistically significant difference in sedation rates before and after the protocol change for patients undergoing chest/ a b d o m e n CT (P = 0.03). In contrast, there was no statistically significant change in the sedation rate for patients undergoing head CT over the same time interval (P = 0.43). There was no statistically significant difference in rates of reported motion artifacts in any group.

Table 1. Motion and sedation rates for patients undergoing CT before and after protocol change on 16 July 1993 Before n

After %

n

%

Head studies Conventional technique

Conventional technique

Sedated No sedation Motion No motion Total (n) Chest / abdomen

29 9 309 91 3 1 335 99 338 100 conventional technique

25 7 334 93 3 1 356 99 359 100 Helicaltechnique

Sedated No sedation Motion No motion Total (n)

33 146 0 179 179

18 154 4 168 172

18 82 0 100 100

10 90 2 98 100

Discussion The results of this study indicate that there was a statistically significant decrease in the sedation rate for chest and abdominal CT coincident with changing from conventional to helical technique. With helical CT, the table is m o v e d through the gantry as the anode and detector continuously rotate. Because there is no need to stop gantry rotation for incremental table movement, there is a 50 % reduction in scan time as compared to conventional CT scanning. We believe that the observed difference in sedation rate was a result of decreased scan time with helical CT. The fact that there was no corresponding drop in sedation rate observed in patients undergoing heat C T o v e r the same time period supports this conclusion because this group of patients did not have helical examinations. One alternative to helical scanning as a means of decreasing scan time and sedation requirements is the ultrafast CT scanner [8]. A l t h o u g h these scanners are capable of scan times on the order of 0.05 s, they have not gained as widespread acceptance as helical CT scanning. Helical scanners have been installed in many sites and continue to proliferate as older generation CT scanners are replaced. Although there was no statistically significant difference in reports of motion artifacts between groups, there was a trend for more motion to be reported for helical as compared to conventional chest CT. We recently conducted a study in which we compared motion artifacts and visibility of anatomic structures in young patients who were unable to breath hold for chest CT examinations [9]. This study demonstrated no statistically significant increase in motion when standard reconstruction algorithms were used. However, the use of the bone algorithm to reconstruct the same helical scans resulted in an increase in detected motion and improved anatomic definition. Prior to our using helical CT, were routinely performed 0.6-s scanning in the breathing, uncooperative infant. This technique would not allow use of the bone

346 algorithm for reconstruction. After switching to routine helical CT we began using the bone algorithm. The increased reporting of motion on helical chest CT in this study is likely due to the improved edge definition afforded with the bone algorithm. There is no evidence that the reduced sedation rate for the helical scans resulted in decrease in examination quality due to gross body motion. ~-Selection criteria for sedation in CT are not universally standardized. Sedation for diagnostic radiographic procedures at our hospital was, however, formalized 3 years ago. In conjunction with the department of anesthesia, a sedation protocol was established to standardize selection criteria, presedation dietary constraints, medication delivery, and monitoring and discharge of patients in the radiology department. This protocol is rigidly followed. Over the time course of this study, there were no changes made in the protocol. The most subjective aspect of the majority of sedation protocol are the selection criteria. In our protocol, we attempt to minimize this by giving every patient a trial at completing the study without sedation prior to administering the medication. Despite this approach, there is still a subjective decision that r~ust be made as to whether sedation will be given. Th< fore, the results of this study do not conclusively demonstrate that helical CT reduces the absolute need for sedation. Nonetheless, as clinically practiced at our site the faster scan speed resulted in a 45 % decrease (10 % versus 18 %) in sedation rates. In other words, only an estimated 55 % of patients receiving sedation for conventional CT of the chest and abdomen would have probably required sedation had helical CT been done. The impact of using helical scanning as a means of reducing sedation requirements will probably vary, depending on the particular sedation policies followed by individual sites.

The most compelling argument for reducing the sedation requirements in patients undergoing radiographic procedures is the fact that there is a small risk of significant morbidity from hypoxemia, aspiration and drug allergy. The results of this study indicate that in our setting we expect that the use of helical CT in the chest and abdomen will obviate the sedation of approximately 60 patients per year. In addition to the savings in patient morbidity, there is a potential for cost savings from decreased nursing requirements and increased scanner throughput. This effect will in part ameliorate the added cost of the helical scanner.

References

1. Broennie AM, Cohen DE (1993) Pediatric anesthesia and sedation. Curr Opin Pediatr 5:310-314 2. Hubbard AM, Markowitz RI, Kimmel B, Kroger M, Bartko MB (1992) Sedation for pediatric patients undergoing CT and MRI. J Comput Assist Tomogr 16:3-6 3. Bisset GS, Ball WS (1991) Preparation, sedation, and monitoring of the pediatric patient in the magnetic resonance suite. Semin Ultrasound CT MR 12:376-378 4. Keeter S, Benator RM, Weinberg SM, Hartenberg MA (1990) Sedation in pediatric CT: national survey of current practice. Radiology 175:745-752 5. Fisher DM (1990) Sedation of pediatric patients: an anesthesiologist's perspective. Radiology 175:613-615 6. Zimmerman RA, Gusnard DA, Bilaniuk LT (1992) Pediatric craniocervical spiral CT. Neuroradiology 34:112-116 7. Luker GD, Lee BC, Erickson KK (1993) Spiral CT of the temporal bone in unsedated pediatric patients. Am J Neuroradiol 14:1145-1150 8. Brasch RC (1988) Ultrafast computed tomography for infants and children. Radiol Clin North Am 26:277-286 9. Cox TD, White KS, Weinberger E, Effmann EL (1994) Comparison of helical and conventional chest CT in the uncooperative pediatric patient. Abstract, 37th Annual Meetlng, Society for Pediatric Radiology, Colorado Springs, Colo., 28 April-1 May