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Diagnosis of Intestinal Injuries by Computed Tomography and the Use of Oral Contrast Medium
Editorials Diagnosis of Intestinal Injuries by Computed Tomography and the Use of Oral Contrast Medium Michael P Federle, MD
Diagnosis of Intestinal Injuries by Computed Tomography and the Use of Oral Contrast Medium
Department of Radiology Chief, Abdominal Imaging University of Pittsburgh Medical Center Pittsburgh, PA
When Does Hypoglycemia Develop After Sulfonylurea Ingestion? Keith K Burkhart, MD Departments of Medicine and Pharmacology Medical Director, Central Pennsylvania Poison Center Penn State Geisinger Health System Hershey, PA Copyright © 1998 by the American College of Emergency Physicians.
JUNE 1998
31:6
ANNALS OF EMERGENCY MEDICINE
[Federle MP: Diagnosis of intestinal injuries by computed tomography and the use of oral contrast medium. Ann Emerg Med June 1998;31:769-771.] Computed tomography (CT) has become widely accepted as a useful and accurate means of diagnosing most abdominal visceral injuries that result from blunt trauma. The value of intravenous contrast material is also accepted as an aid to recognition of visceral and vascular injuries. More controversial are the utility of oral contrast media and the accuracy of CT in diagnosing bowel, mesenteric, and pancreatic traumatic injuries. Tsang et al.1 recently published a study of the effect of oral contrast administration for abdominal CT evaluation of blunt trauma and reached a number of conclusions and recommendations that merit further discussion. Tsang and colleagues evaluated 248 patients who had CT for abdominal trauma and they chose to review 70 CT scans. These included 21 patients who subsequently had intestinal/mesenteric injuries found at surgery, none of which were diagnosed by the authors on CT. They also failed to diagnose three of six pancreatic injuries. They report a high prevalence of vomiting (23%) and occasional aspiration, which they attribute to the use of oral contrast. They concluded that the use of oral contrast material for CT in the setting of acute abdominal trauma is excessively time-consuming, potentially dangerous, and does not help in diagnosing pancreatic or intestinal/mesenteric injuries. To their credit, Tsang et al1 acknowledge several of the limitations of their retrospective study and also an obvious selection bias on the part of their surgeons. The latter is reflected by the rarity of confirmed bowel injuries that were encountered in patients having CT evaluation for acute blunt abdominal trauma. In most trauma centers one would expect bowel or mesenteric injuries in approximately 3%
7 6 9
EDITORIALS
to 5% of patients with significant blunt abdominal trauma and a similar prevalence of pancreatic injuries.2 Tsang et al1 report a prevalence of only .3% in their patients, and state that their surgeons have a “low threshold” for taking patients to surgery. Although such a policy will probably find and correct many bowel injuries, it will also result in many nontherapeutic laparotomies for blunt solid visceral injuries, most of which are managed nonoperatively in major trauma centers today. The authors do not describe adequately the nature of the pancreatic or intestinal/mesenteric injuries that came to CT evaluation. Undoubtedly, these would constitute a more challenging group to diagnose and we have no way of judging whether these were clinically significant or required specific surgical intervention. Other authors have reported widely divergent results for the CT diagnosis of bowel injuries.3-8 Some discrepancies are clearly related to patient selection. Inclusion of patients with penetrating abdominal injuries, as in some studies, guarantees poor diagnostic results with CT. Performance of abdominal CT after diagnostic peritoneal lavage makes diagnosis of bowel injury difficult because fluid and air may be retained within the abdomen, simulating or obscuring the results of bowel perforation. Simple but often overlooked technical factors in the performance and photographic recording of the CT scan can make a crucial difference. Streak artifacts from excessively dense oral contrast material or overlying ECG leads can render a CT scan uninterpretable but can be avoided, and older CT scanners are particularly prone to streak artifacts. Failure to scan completely through the lower abdomen and pelvis, and failure to view CT sections at wide window settings (extended gray scale or “lung windows”) are well documented but easily avoided pitfalls in the CT diagnosis of bowel injuries. Diagnosis of bowel injuries by CT is challenging and requires more sophistication and experience than diagnosis of liver, spleen, or renal injuries. It is relatively uncommon to encounter unequivocal evidence of bowel perforation, such as free air or extraluminal enteric contents. Tsang et al appear to have relied on these “diagnostic signs” to diagnose bowel trauma, but many additional CT findings have been reported3-6 that allow confident diagnosis of bowel injury even in the absence of free air (eg, the “sentinel clot,” intramural hematoma, interloop or mesenteric fluid collections, abnormal bowel enhancement, free fluid without a solid visceral injury). Radiologic diagnosis is rarely an “all-or-none” phenomenon; rather, we take into consideration a combination of the imaging findings and the clinical presentation to make a reasoned judgment as to the likely diagnosis. In a recent study of blunt intestinal injury in children, Kurkchubasche et al9 found that clinical and CT evaluation
7 7 0
can independently identify the presence of bowel injury in about 25% of cases, and that awareness of some of the more subtle CT signs noted above allowed earlier diagnosis and surgical intervention in many additional cases. They stressed the importance of certain clinical signs (eg, abdominal wall ecchymosis, seat belt abrasion, Chance fracture of the lumbar spine) as having a high correlation with intestinal injury, and they point out that a CT scan that is interpreted as “normal” should not be used to exclude the diagnosis of intestinal injury. Our experience with a much larger number of adults and children with intestinal injuries is similar, and we have also concluded that close physician monitoring coupled with CT evaluation allows confident management, minimizes delays in diagnosis, and should virtually eliminate mortality and severe morbidity as a result of a missed diagnosis of intestinal injury. A repeat CT scan, conventional upper gastrointestinal tract series, diagnostic peritoneal lavage, or even exploratory celiotomy may be considered when the diagnosis remains unclear, but these are necessary uncommonly in our experience. The use of oral contrast material for trauma CT scans is a related issue that is controversial in its own right. Some authors3-6,8 use it routinely and believe that it can improve the accuracy of CT diagnosis of bowel and pancreatic injuries, whereas others1,7 claim that the use of oral contrast is unnecessary and perhaps even dangerous. Tsang and his colleagues are in the latter group and seem to attribute all cases of vomiting or aspiration in the acute trauma setting to the use of oral contrast for CT. Trauma patients are at risk of vomiting and aspiration regardless of whether oral contrast is administered. Trauma patients may vomit and aspirate gastric contents at the scene of the accident or during evaluation and resuscitation, having nothing to do with the performance of a CT scan. We have recently reviewed and published10,11 detailed analyses of more than 1,000 patients who had oral contrast material as part of their acute trauma CT evaluation with virtually no adverse effects that could be related to the use of the contrast medium. As pointed out in our articles, the key factor in avoiding aspiration of gastric contents is adherence to published Advanced Trauma Life Support and American Association for the Surgery of Trauma guidelines for the use of endotracheal and nasogastric intubation in the trauma setting.12-14 Tsang and others claim that the use of oral contrast causes unacceptable delays in evaluation of the abdominal trauma patients, averaging 144 minutes. It would be more accurate to state that the trauma CT protocol used at the authors’ institution required a lengthy delay. As noted by other investigators,3-6 such delays are unwarranted and unnecessary, and we never delay the CT scan for purposes
ANNALS OF EMERGENCY MEDICINE
31:6 JUNE 1998
EDITORIALS
of achieving better bowel opacification. Rather, the oral contrast is administered by nursing personnel in the emergency department as soon as a decision for CT evaluation has been made. Almost invariably, enough time elapses in the course of additional evaluation and resuscitation in the ED to allow for gastric emptying. In fact, we frequently give additional oral contrast in the CT scanning suite because more than 30 minutes have elapsed since the first administration of contrast. The goal is not to opacify the entire luminal gastrointestinal tract, but rather the duodenum and jejunum, which are the segments of bowel most frequently injured in blunt trauma. It is also unnecessary and unwise to administer the large volume of oral contrast (up to 1,000 mL) used by Tsang et al. It should be apparent that many important issues remain unresolved before we can make any definitive statements about the sensitivity and specificity of CT for diagnosing intestinal injuries. Virtually all investigations to date have been unblinded, uncontrolled, retrospective reviews, subject to all of the bias and potential to mislead as other “scanty science” recently addressed in an editorial in this journal.15 Given the nature of clinical trauma practice, it may be difficult or impossible to conduct prospective randomized controlled trials, but there are equally valid methodologies that can be used to test and compare newer imaging technologies against human observer performance (the ability of the “expert” radiologist). These include multiplereader studies with calculation of receiver operating characteristic (ROC) curves.16,17 Use of ROC curves allows analysis of the trade-offs between the sensitivity and specificity of a test with regard to the variable diagnostic criteria used by radiologists and avoids the inaccuracies that arise from assuming that imaging findings are absolutely normal or abnormal. Pending completion and publication of such investigations, radiologists and other physicians caring for patients with abdominal trauma must rely on their own judgment and experience in deciding how to perform, interpret, and rely on the CT diagnosis of intestinal injuries. 1. Tsang BD, Panacek EA, Brant WE, et al: Effect of oral contrast administration for abdominal computed tomography in the evaluation of acute blunt trauma. Ann Emerg Med 1997;30:7-13. 2. Buck G, Dalton M, Neely W: Diagnostic laparotomy for abdominal trauma. Ann Surg 1986;52: 41-43. 3. Donahue J, Federle MP, Griffiths B, et al: Computed tomography in the diagnosis of blunt intestinal and mesenteric injury. J Trauma 1987;27:11-17. 4. Rizzo MJ, Federle MP, Griffiths BG: Bowel and mesenteric injury following blunt abdominal trauma: Evaluation with CT. Radiology 1989;173:143-148. 5. Nghiem HV, Jeffrey RB, Mindelzun RE: CT of blunt trauma to the bowel and mesentery. AJR Am J Roentgenol 1993;160:53-58. 6. Mirvis SE, Geis DR, Shanmuganathan K: Rupture of the bowel after blunt abdominal trauma: Diagnosis with CT. AJR Am J Roentgenol 1992;159:1217-1221. 7. Clancy TV, Raggazzino MW, Ramshau D, et al: Oral contrast is not necessary in the evaluation of blunt abdominal trauma by CT. Am J Surg 1993;166:680-685.
JUNE 1998
31:6
ANNALS OF EMERGENCY MEDICINE
8. Sherck JP, Oakes DD: Intestinal injuries missed by computed tomography. J Trauma 1990;30:1-7. 9. Kurkschubasche AG, Fendya DC, Tracy TFJ, et al: Blunt intestinal injury in children. Arch Surg 1997;132:652-658. 10. Federie MP, Peitzman A, Krugh J: Use of oral contrast material in abdominal trauma CT scans: Is it dangerous? J Trauma 1995;38:51-53. 11. Federie MP, Yagan N, Peitzman AB, et al: Abdominal trauma: Use of oral contrast material for CT is safe. Radiology 1997;205:91-93. 12. Phillips S, Hutchinson S, Davidson T: Preoperative drinking does not affect gastric contents. Br J Anaesth 1991;38:425-429. 13. American College of Surgeons: Advanced trauma life support. Chicago: American College of Surgeons, 1993. 14. Grande CM (ed): Textbook of trauma anesthesia and critical care. St Louis: Mosby–Year Book, 1993. 15. Callahan M: Quantifying the scanty science of prehospital emergency care. Ann Emerg Med 1997;30:785-790. 16. Brismar J: Understanding receiver-operating-characteristic curves: A graphic approach. AJR Am J Roentgenol 1991;157:1119-1121. 17. Obuchowski NA, Zepp RC: Simple steps for improving multiple-reader studies in radiology. AJR Am J Roentgenol 1996;166:517-521.
Reprint no. 47/1/90335 Reprints not available from the author.
When Does Hypoglycemia Develop After Sulfonylurea Ingestion? See related article, p 773. [Burkhart KK: When does hypoglycemia develop after sulfonylurea ingestion? Ann Emerg Med June 1998;31:771-772.] The ingestion of a sulfonylurea medication by a child is a common patient encounter for emergency physicians. Ingestion of a single tablet by a nondiabetic adult or child usually produces clinically significant hypoglycemia.1 Therefore hospital admission appears warranted, if not required. Most poison centers recommend admission until glucose supplementation is no longer required. What should the recommendation be, however, if a child is found playing with an open bottle of tablets and may or may not have ingested one? Must these children be observed for 24 hours? Can a shorter period of observation be justified? The medical literature contains few references on this topic. One of the earliest reports is from 1968.2 A 3-year-old child ingested chlorpropamide, appeared well for 24 hours, but then became symptomatic and was admitted 36 hours after ingestion with a blood sugar level of 28 mg/dL. At what time serial monitoring of the blood sugar level would have detected the onset of hypoglycemia and confirmed the ingestion is not known. This case is the basis of current recommendations for a 24-hour observation period
7 7 1
Diagnosis of Intestinal Injuries by Computed Tomography and the Use of Oral Contrast Medium
Department of Radiology Chief, Abdominal Imaging University of Pittsburgh Medical Center Pittsburgh, PA
When Does Hypoglycemia Develop After Sulfonylurea Ingestion? Keith K Burkhart, MD Departments of Medicine and Pharmacology Medical Director, Central Pennsylvania Poison Center Penn State Geisinger Health System Hershey, PA Copyright © 1998 by the American College of Emergency Physicians.
JUNE 1998
31:6
ANNALS OF EMERGENCY MEDICINE
[Federle MP: Diagnosis of intestinal injuries by computed tomography and the use of oral contrast medium. Ann Emerg Med June 1998;31:769-771.] Computed tomography (CT) has become widely accepted as a useful and accurate means of diagnosing most abdominal visceral injuries that result from blunt trauma. The value of intravenous contrast material is also accepted as an aid to recognition of visceral and vascular injuries. More controversial are the utility of oral contrast media and the accuracy of CT in diagnosing bowel, mesenteric, and pancreatic traumatic injuries. Tsang et al.1 recently published a study of the effect of oral contrast administration for abdominal CT evaluation of blunt trauma and reached a number of conclusions and recommendations that merit further discussion. Tsang and colleagues evaluated 248 patients who had CT for abdominal trauma and they chose to review 70 CT scans. These included 21 patients who subsequently had intestinal/mesenteric injuries found at surgery, none of which were diagnosed by the authors on CT. They also failed to diagnose three of six pancreatic injuries. They report a high prevalence of vomiting (23%) and occasional aspiration, which they attribute to the use of oral contrast. They concluded that the use of oral contrast material for CT in the setting of acute abdominal trauma is excessively time-consuming, potentially dangerous, and does not help in diagnosing pancreatic or intestinal/mesenteric injuries. To their credit, Tsang et al1 acknowledge several of the limitations of their retrospective study and also an obvious selection bias on the part of their surgeons. The latter is reflected by the rarity of confirmed bowel injuries that were encountered in patients having CT evaluation for acute blunt abdominal trauma. In most trauma centers one would expect bowel or mesenteric injuries in approximately 3%
7 6 9
EDITORIALS
to 5% of patients with significant blunt abdominal trauma and a similar prevalence of pancreatic injuries.2 Tsang et al1 report a prevalence of only .3% in their patients, and state that their surgeons have a “low threshold” for taking patients to surgery. Although such a policy will probably find and correct many bowel injuries, it will also result in many nontherapeutic laparotomies for blunt solid visceral injuries, most of which are managed nonoperatively in major trauma centers today. The authors do not describe adequately the nature of the pancreatic or intestinal/mesenteric injuries that came to CT evaluation. Undoubtedly, these would constitute a more challenging group to diagnose and we have no way of judging whether these were clinically significant or required specific surgical intervention. Other authors have reported widely divergent results for the CT diagnosis of bowel injuries.3-8 Some discrepancies are clearly related to patient selection. Inclusion of patients with penetrating abdominal injuries, as in some studies, guarantees poor diagnostic results with CT. Performance of abdominal CT after diagnostic peritoneal lavage makes diagnosis of bowel injury difficult because fluid and air may be retained within the abdomen, simulating or obscuring the results of bowel perforation. Simple but often overlooked technical factors in the performance and photographic recording of the CT scan can make a crucial difference. Streak artifacts from excessively dense oral contrast material or overlying ECG leads can render a CT scan uninterpretable but can be avoided, and older CT scanners are particularly prone to streak artifacts. Failure to scan completely through the lower abdomen and pelvis, and failure to view CT sections at wide window settings (extended gray scale or “lung windows”) are well documented but easily avoided pitfalls in the CT diagnosis of bowel injuries. Diagnosis of bowel injuries by CT is challenging and requires more sophistication and experience than diagnosis of liver, spleen, or renal injuries. It is relatively uncommon to encounter unequivocal evidence of bowel perforation, such as free air or extraluminal enteric contents. Tsang et al appear to have relied on these “diagnostic signs” to diagnose bowel trauma, but many additional CT findings have been reported3-6 that allow confident diagnosis of bowel injury even in the absence of free air (eg, the “sentinel clot,” intramural hematoma, interloop or mesenteric fluid collections, abnormal bowel enhancement, free fluid without a solid visceral injury). Radiologic diagnosis is rarely an “all-or-none” phenomenon; rather, we take into consideration a combination of the imaging findings and the clinical presentation to make a reasoned judgment as to the likely diagnosis. In a recent study of blunt intestinal injury in children, Kurkchubasche et al9 found that clinical and CT evaluation
7 7 0
can independently identify the presence of bowel injury in about 25% of cases, and that awareness of some of the more subtle CT signs noted above allowed earlier diagnosis and surgical intervention in many additional cases. They stressed the importance of certain clinical signs (eg, abdominal wall ecchymosis, seat belt abrasion, Chance fracture of the lumbar spine) as having a high correlation with intestinal injury, and they point out that a CT scan that is interpreted as “normal” should not be used to exclude the diagnosis of intestinal injury. Our experience with a much larger number of adults and children with intestinal injuries is similar, and we have also concluded that close physician monitoring coupled with CT evaluation allows confident management, minimizes delays in diagnosis, and should virtually eliminate mortality and severe morbidity as a result of a missed diagnosis of intestinal injury. A repeat CT scan, conventional upper gastrointestinal tract series, diagnostic peritoneal lavage, or even exploratory celiotomy may be considered when the diagnosis remains unclear, but these are necessary uncommonly in our experience. The use of oral contrast material for trauma CT scans is a related issue that is controversial in its own right. Some authors3-6,8 use it routinely and believe that it can improve the accuracy of CT diagnosis of bowel and pancreatic injuries, whereas others1,7 claim that the use of oral contrast is unnecessary and perhaps even dangerous. Tsang and his colleagues are in the latter group and seem to attribute all cases of vomiting or aspiration in the acute trauma setting to the use of oral contrast for CT. Trauma patients are at risk of vomiting and aspiration regardless of whether oral contrast is administered. Trauma patients may vomit and aspirate gastric contents at the scene of the accident or during evaluation and resuscitation, having nothing to do with the performance of a CT scan. We have recently reviewed and published10,11 detailed analyses of more than 1,000 patients who had oral contrast material as part of their acute trauma CT evaluation with virtually no adverse effects that could be related to the use of the contrast medium. As pointed out in our articles, the key factor in avoiding aspiration of gastric contents is adherence to published Advanced Trauma Life Support and American Association for the Surgery of Trauma guidelines for the use of endotracheal and nasogastric intubation in the trauma setting.12-14 Tsang and others claim that the use of oral contrast causes unacceptable delays in evaluation of the abdominal trauma patients, averaging 144 minutes. It would be more accurate to state that the trauma CT protocol used at the authors’ institution required a lengthy delay. As noted by other investigators,3-6 such delays are unwarranted and unnecessary, and we never delay the CT scan for purposes
ANNALS OF EMERGENCY MEDICINE
31:6 JUNE 1998
EDITORIALS
of achieving better bowel opacification. Rather, the oral contrast is administered by nursing personnel in the emergency department as soon as a decision for CT evaluation has been made. Almost invariably, enough time elapses in the course of additional evaluation and resuscitation in the ED to allow for gastric emptying. In fact, we frequently give additional oral contrast in the CT scanning suite because more than 30 minutes have elapsed since the first administration of contrast. The goal is not to opacify the entire luminal gastrointestinal tract, but rather the duodenum and jejunum, which are the segments of bowel most frequently injured in blunt trauma. It is also unnecessary and unwise to administer the large volume of oral contrast (up to 1,000 mL) used by Tsang et al. It should be apparent that many important issues remain unresolved before we can make any definitive statements about the sensitivity and specificity of CT for diagnosing intestinal injuries. Virtually all investigations to date have been unblinded, uncontrolled, retrospective reviews, subject to all of the bias and potential to mislead as other “scanty science” recently addressed in an editorial in this journal.15 Given the nature of clinical trauma practice, it may be difficult or impossible to conduct prospective randomized controlled trials, but there are equally valid methodologies that can be used to test and compare newer imaging technologies against human observer performance (the ability of the “expert” radiologist). These include multiplereader studies with calculation of receiver operating characteristic (ROC) curves.16,17 Use of ROC curves allows analysis of the trade-offs between the sensitivity and specificity of a test with regard to the variable diagnostic criteria used by radiologists and avoids the inaccuracies that arise from assuming that imaging findings are absolutely normal or abnormal. Pending completion and publication of such investigations, radiologists and other physicians caring for patients with abdominal trauma must rely on their own judgment and experience in deciding how to perform, interpret, and rely on the CT diagnosis of intestinal injuries. 1. Tsang BD, Panacek EA, Brant WE, et al: Effect of oral contrast administration for abdominal computed tomography in the evaluation of acute blunt trauma. Ann Emerg Med 1997;30:7-13. 2. Buck G, Dalton M, Neely W: Diagnostic laparotomy for abdominal trauma. Ann Surg 1986;52: 41-43. 3. Donahue J, Federle MP, Griffiths B, et al: Computed tomography in the diagnosis of blunt intestinal and mesenteric injury. J Trauma 1987;27:11-17. 4. Rizzo MJ, Federle MP, Griffiths BG: Bowel and mesenteric injury following blunt abdominal trauma: Evaluation with CT. Radiology 1989;173:143-148. 5. Nghiem HV, Jeffrey RB, Mindelzun RE: CT of blunt trauma to the bowel and mesentery. AJR Am J Roentgenol 1993;160:53-58. 6. Mirvis SE, Geis DR, Shanmuganathan K: Rupture of the bowel after blunt abdominal trauma: Diagnosis with CT. AJR Am J Roentgenol 1992;159:1217-1221. 7. Clancy TV, Raggazzino MW, Ramshau D, et al: Oral contrast is not necessary in the evaluation of blunt abdominal trauma by CT. Am J Surg 1993;166:680-685.
JUNE 1998
31:6
ANNALS OF EMERGENCY MEDICINE
8. Sherck JP, Oakes DD: Intestinal injuries missed by computed tomography. J Trauma 1990;30:1-7. 9. Kurkschubasche AG, Fendya DC, Tracy TFJ, et al: Blunt intestinal injury in children. Arch Surg 1997;132:652-658. 10. Federie MP, Peitzman A, Krugh J: Use of oral contrast material in abdominal trauma CT scans: Is it dangerous? J Trauma 1995;38:51-53. 11. Federie MP, Yagan N, Peitzman AB, et al: Abdominal trauma: Use of oral contrast material for CT is safe. Radiology 1997;205:91-93. 12. Phillips S, Hutchinson S, Davidson T: Preoperative drinking does not affect gastric contents. Br J Anaesth 1991;38:425-429. 13. American College of Surgeons: Advanced trauma life support. Chicago: American College of Surgeons, 1993. 14. Grande CM (ed): Textbook of trauma anesthesia and critical care. St Louis: Mosby–Year Book, 1993. 15. Callahan M: Quantifying the scanty science of prehospital emergency care. Ann Emerg Med 1997;30:785-790. 16. Brismar J: Understanding receiver-operating-characteristic curves: A graphic approach. AJR Am J Roentgenol 1991;157:1119-1121. 17. Obuchowski NA, Zepp RC: Simple steps for improving multiple-reader studies in radiology. AJR Am J Roentgenol 1996;166:517-521.
Reprint no. 47/1/90335 Reprints not available from the author.
When Does Hypoglycemia Develop After Sulfonylurea Ingestion? See related article, p 773. [Burkhart KK: When does hypoglycemia develop after sulfonylurea ingestion? Ann Emerg Med June 1998;31:771-772.] The ingestion of a sulfonylurea medication by a child is a common patient encounter for emergency physicians. Ingestion of a single tablet by a nondiabetic adult or child usually produces clinically significant hypoglycemia.1 Therefore hospital admission appears warranted, if not required. Most poison centers recommend admission until glucose supplementation is no longer required. What should the recommendation be, however, if a child is found playing with an open bottle of tablets and may or may not have ingested one? Must these children be observed for 24 hours? Can a shorter period of observation be justified? The medical literature contains few references on this topic. One of the earliest reports is from 1968.2 A 3-year-old child ingested chlorpropamide, appeared well for 24 hours, but then became symptomatic and was admitted 36 hours after ingestion with a blood sugar level of 28 mg/dL. At what time serial monitoring of the blood sugar level would have detected the onset of hypoglycemia and confirmed the ingestion is not known. This case is the basis of current recommendations for a 24-hour observation period
7 7 1