Defining the critical limit of oxygen extraction in the human small intestine

AbstractAlthough animal models have been used to characterize the relation between oxygen consumption and blood flow, reliable data have not been generated in the human small intestine. We perfused segments of human small intestine by using an ex vivo perfusion circuit that allowed precise manipulation of blood flow and perfusion pressure. Our goal was to define the critical level of intestinal blood flow necessary to maintain the metabolic needs of the tissue. Human small intestine (n = 5) tissue obtained at transplantation harvest was transported on ice to the laboratory. A 40-cm mid-jejunal segment was selected for perfusion, and appropriate inflow and outflow vessels were identified and cannulated. Perfusion with an autologous blood solution was initiated through an extracorporeal membrane oxygenation circuit. After a 30-minute equilibration period, arterial and venous blood gases were measured at varying flow rates while maintaining a constant hematocrit level. Arterial and venous oxygen content, arteriovenous oxygen difference (A-VO2 diff), and oxygen consumption (O 2 ) were then calculated. Our results demonstrated that at blood flows >30 ml/min/100 g, O 2 is independent of blood flow (1.6 ± 0.06 ml/min/100 g), and oxygen extraction is inversely related to flow. Below this blood flow rate of 30 ml/min/100 g, oxygen extraction does not increase further (6.3 ± 0.3 vol%), and O 2 becomes flow dependent. This ex vivo preparation defines for the first time a threshold value of blood flow for small intestine below which oxygen consumption decreases (30 ml/min/100 g). Previous animal studies have correlated such a decrease in oxygen consumption with functional and histologic evidence of tissue injury. This “critical” flow rate in human intestine is similar to that found previously in canine and feline intestine, but lower than that of rodent species. (J Vasc Surg 1996;23:832-8.

Rapid Detection of Traumatic Effusion Using Surgeon-Performed Ultrasonography

BACKGROUNDIn the injured patient, rapid assessment of the thorax can yield critical information for patient management and triage. OBJECTIVESThe objectives of this prospective study were (1) to determine if experienced surgeon sonographers could successfully use a focused thoracic ultrasonographic examination to detect traumatic effusion, and (2) to compare the accuracy and efficiency of ultrasonography with supine portable chest radiography. METHODSSurgeon-sonographers performed thoracic ultrasonographic examinations on patients with blunt and penetrating torso injuries during the Advanced Trauma Life Support secondary survey. All patients also underwent portable chest radiography. Performance times for ultrasonography and chest radiography were recorded. Comparisons were made of the performance times and accuracy of both tests in detecting traumatic effusion. RESULTSIn 360 patients, there were 40 effusions, 39 of which were detected by ultrasonography and 37 of which were detected by chest radiography. The 97.5% sensitivity and 99.7% specificity observed for thoracic ultrasonography were similar to the 92.5% sensitivity and 99.7% specificity for portable chest radiography. Performance time for ultrasonography was significantly faster than that for chest radiography (1.30 +/- 0.08 vs. 14.18 +/- 0.91 minutes, p < 0.0001). CONCLUSIONSurgeons can accurately perform and interpret a focused thoracic ultrasonographic examination to detect traumatic effusion. Surgeon-performed thoracic ultrasonography is as accurate but is significantly faster than supine portable chest radiography for the detection of traumatic effusion

Video-based training increases sterile-technique compliance during central venous catheter insertion.

OBJECTIVE: To evaluate the effect of an online training course containing video clips of central venous catheter insertions on compliance with sterile practice. DESIGN: Prospective randomized controlled study. SETTING: Admitting area of a university-based high-volume trauma center. SUBJECTS: Surgical and emergency medicine residents rotating through the trauma services. INTERVENTIONS: An online training course on recommended sterile practices during central venous catheter insertion was developed. The course contained short video clips from actual patient care demonstrating common noncompliant behaviors and breaks regarding recommended sterile practices. A 4-month study with a counterbalanced design compared residents trained by the video-based online training course (video group) with those trained with a paper version of the course (paper group). Residents who inserted central venous catheters but received neither the paper nor video training were used as a control group. Consecutive central venous catheter insertions from 12 noon to 12 midnight except Sundays were video recorded. MEASUREMENTS AND MAIN RESULTS: Sterile-practice compliance was judged through video review by two surgeons blinded to the training status of the residents. Fifty residents inserted 73 elective central venous catheters (19, 31, and 23 by the video, paper, and control group operators, respectively) into 68 patients. Overall compliance with proper operator preparation, skin preparation, and draping was 49% (36 of 73 procedures). The training had no effect on selection of site and skin preparation agent. The video group was significantly more likely than the other two groups to fully comply with sterile practices (74% vs. 33%; odds ratio, 6.1; 95% confidence interval, 2.0-22.0). Even after we controlled for the number of years in residency training, specialty, number of central venous catheters inserted, and central venous catheter site chosen, the video group was more likely to comply with recommended sterile practices (p = .003). CONCLUSIONS: An online training course, with short video clips of actual patient care demonstrating noncompliant behaviors, improved sterile-practice compliance for central venous catheter insertion. Paper handouts with equivalent content did not improve compliance

The Role of Surgeon-Performed Ultrasound in Patients with Possible Cardiac Wounds.

OBJECTIVE: The authors evaluate surgeon-performed ultrasound in determining the need for operation in patients with possible cardiac wounds. BACKGROUND DATA: Ultrasound quickly is becoming part of the surgeon\u27s diagnostic armamentarium; however, its role for the patient with penetrating injury is less well-defined. Although accurate for the detection of hemopericardium, the lack of immediate availability of the cardiologist to perform the test may delay the diagnosis, adversely affecting patient outcome. To be an effective diagnostic test in trauma centers, ultrasound must be immediately available in the resuscitation area and performed and interpreted by surgeons. METHODS: Surgeons performed pericardial ultrasound examinations on patients with penetrating truncal wounds but no immediate indication for operation. The subcostal view detected hemopericardium, and patients with positive examinations underwent immediate operation by the same surgeon. Vital signs, base deficit, time from examination to operation, operative findings, treatment, and outcome were recorded. RESULTS: During 13 months, 247 patients had surgeon-performed ultrasound. There were 236 true-negative and 10 true-positive results, and no false-negative or false-positive results; however, the pericardial region could not be visualized in one patient. Sensitivity, specificity, and accuracy were 100%; mean examination time was 0.8 minute (246 patients). Of the ten true-positive examinations, three were hypotensive. The mean time (8 patients) from ultrasound to operation was 12.1 minutes; all survived. Operative findings (site of cardiac wounds) were: left ventricle (4), right ventricle (3), right atrium (2), right atrium/superior vena cava (1), and right atrium/inferior vena cava (1). CONCLUSIONS: Surgeon-performed ultrasound is a rapid and accurate technique for diagnosing hemopericardium. Delay times from admission to operating room are minimized when the surgeon performs the ultrasound examination