JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
Although plain x-rays of the abdomen were usually diagnostic in gastrointestinal perforations and obstructions, psoas abscess, and renal colic, they only demonstrated an overall predictive accuracy of 4.1% and sensitivity of 60%.¹¹-¹⁵ The high accuracy of cross sectional CT imaging and ultrasound with fast throughput has identifiedbothCT andultrasound as the preferredmodalities in imaging patients with acute abdominal pain. Nevertheless, there are limitations to bedside US. Visualization of gastric contents may be reduced if air is either in the stomach or intervening soft tissues. Postoperative stomach remnants or intervening soft tissues. Postoperative stomach remnants following subtotal gastrectomy and hiatal hernia repairs may also make gastric contents difficult to visualize. Lastly, technical skill is needed to perform a valid ultrasound study. MRI is the latest modality for imaging of the acute abdomen. MRI avoids the hazards associated with radiation and iodinated contrast agents. MRI also affords superior soft tissue visualization compared to CT and ultrasound. Although MRI has been used to study gastric distention and emptying, its use in an urgent setting is not cost-effective as compared to abdominal CT and ultrasound imaging.¹⁹-²⁴ In addition, MRI applications are limited in patients with pacemakers, prosthetic joints, and vertebral hardware. Lastly, MRI studies are poorly tolerated by patients with claustrophobia. In summary, gastric distension is a high-risk factor for pulmonary aspiration and may often go undetected preoperatively. In this case report, a patient with gastric distension was identified preoperatively by review of the diagnostic abdominal CT scans. The preoperative CT scan may provide a better assessment of pulmonary aspiration risks from gastric distension than just suspicion and clinical assessment.
Awake flexible fiberoptic tracheal intubation is the gold standard for management of anticipated difficult tracheal intubation, but the maintenance of the necessary psychomotor skills for fiberoptic intubation may pose a significant problem.⁷ Closed claims analysis has found poor outcomes in two clinical scenarios of awake intubation: (1) sedation/airway instrumentation in the presence of pharyngeal infection; and (2) induction of anesthesia after unsuccessful attempts at awake intubation due to technical problems or lack of patient cooperation.⁸ Gastric decompression by preoperative NG tube placement affords another way to avoid pulmonary aspiration without the need to resort to RSI or awake fiberoptic endotracheal intubation. In order to use NG tube placement to its greatest advantages, preoperative abdominal imaging should be reviewed in order to confirm gastric distension and benefit from the decompression of retained gastric contents. As in the case reported, patients with acute abdominal pain are likely to have a recent cross sectional imaging study that will demonstratethe presence or absence of gastric distention. Radiographic imaging is important in the diagnostic work up of acute abdominal pain. Imaging can identify which patients will most likely benefit from conservative therapy and which patients will benefit from surgical management. Conventional radiography is often the initial imaging examination ordered because it is available and easy to perform, however, CT and ultrasound imaging frequently yield more useful information across more potential diagnoses than conventional radiography. In a study by Ahn et al.,⁹ CT specificities approached 100% for bowel obstruction, urolithiasis, appendicitis, pyelonephritis, pancreatitis, and diverticulitis. In another study by McKersie,¹⁰ nonenhanced helical CT yielded a higher sensitivity, specificity, and accuracy compared with a three view acute abdominal series (96% vs 30%, 95.1% vs 87.8% and 95.6% vs 56%, p<0.5). Bedside ultrasound is another option in the event that a pre-intubation conventional X-ray or CT imaging does not demonstrate the stomach contents well. Bedside ultrasound has recently been proposed as useful in the following common clinical scenarios: (1) patients who have not followed fasting guidelines because of either noncompliance or urgency of the medical condition; and (2) patients with delayed gastric emptying due to a comorbidity and patients with unreliable histories.¹¹-¹⁶ In order to perform a bedside US exam, the gastric antrum is imaged with a curved array 2- to 5- MHz transducer (patient weight >40 kg) in the epigastric sagittal plane. The best images are obtained with patients in either the right lateral decubitus or supine position. Thin and thick fluids as well as solid food can be differentiated and volumes can be discerned thus putting forward a potential for aspiration risk.¹⁶-¹⁹
Gupta et al.¹¹ confirmed ultrasound to be highly accurate in diagnosing the exact cause of acute abdomen with high overall predictive accuracy of 98.3% and sensitivity of 90% compared to conventional X-rays.
100 La State Med Soc VOL 170 JULY/AUG 2018
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