Lawrence N. Diebel

Effect of Increased Intra-Abdominal Pressure on Hepatic Arterial, Portal Venous, and Hepatic Microcirculatory Blood Flow

The effects of increased intra-abdominal pressure (IAP) on hepatic perfusion were studied in five anesthetized pigs. Doppler flow probes were used to measure hepatic artery blood flow (HABF) and portal venous blood flow (PVBF), and laser Doppler flowmetry was used to assess changes in hepatic microvascular blood flow (HMVBF). Hepatic blood flow responses to 10, 20, 30 and 40 mm Hg increases in IAP were assessed while the mean arterial BP (MAP) was maintained at baseline levels with IV crystalloid infusions. Although cardiac output and MAP were normal, HABF and HMVBF fell significantly with 10 mm IAP, and at 20 mm Hg IAP, HABF was 45% of the control value, PVBF was 65% of the control value, and HMVBF was 71% of the control value (p less than 0.05). At 30 and 40 mm Hg, hepatic blood flow was reduced even more. Thus, modest increases in IAP can cause significant impairment of hepatic perfusion despite a normal BP and cardiac output.

EFFECT OF INCREASED INTRA-ABDOMINAL PRESSURE ON MESENTERIC ARTERIAL AND INTESTINAL MUCOSAL BLOOD FLOW

The effects of increased intra-abdominal pressure (IAP) on intestinal blood flow were studied in eight anesthetized pigs. Mesenteric artery blood flow (MABF), intestinal mucosal blood flow (IMBP), tonometric intramucosal pH (pHi), mean BP (MAP), cardiac output (CO), and pulmonary artery wedge pressure (PAWP) were measured as IAP was raised to 10, 20, 30, and 40 mm Hg by infusing lactated Ringers solution (LR) into the peritoneal cavity. The MAP was kept constant with IV LR. Cardiac output fell slightly from 5.4 +/- 1.1 at baseline to 4.0 +/- 1.2 L/min at an IAP of 40 mm Hg (p less than 0.05). An IAP of 20 mm Hg caused significant decreases in MABF (73% +/- 22% of baseline) (p less than 0.05) and IMBF (61% + 12% of baseline) (p less than 0.05). These changes became progressively greater as the IAP was increased to 40 mm Hg. The pHi fell to 6.98 +/- 0.14 at 40 mm Hg IAP (p less than 0.01), indicating severe mucosal ischemia. Thus increased IAP can cause severe intestinal ischemia, which may be more important than the cardiac, pulmonary, and renal changes usually described.

INTRA-ABDOMINAL HYPERTENSION AND THE ABDOMINAL COMPARTMENT SYNDROME

IAH causes multiple and profound physiologic abnormalities both within and outside the abdomen. IAP monitoring is easily performed by bladder measurements. Careful monitoring and prompt recognition and treatment of IAP are critical in patients after damage control surgery because IAH is extremely common in these patients. Use of mesh fascial prostheses at the initial celiotomy in high-risk patients may prevent the deleterious effects of IAH. IAH should be considered an earlier manifestation of ACS. Surgical intervention should be indicated by IAH and not delayed until ACS is clinically apparent.

Splanchnic ischemia and bacterial translocation in the abdominal compartment syndrome

BACKGROUND AND METHODS Major trauma or abdominal injury may lead to the development of increased intra-abdominal pressure (IAP) and the onset of the abdominal compartment syndrome. Although the effect of raised IAP on systemic and splanchnic hemodynamics have been described, the consequences of the resultant gut hypoperfusion in this setting are unknown. Bacterial translocation (BT) occurs after a period of splanchnic ischemia and may contribute to later organ failure. A rodent model was used to examine the effect of raised IAP on ileal mucosal blood flow (MBF) and BT. IAP was increased to 25 mm Hg for 60 minutes and mean arterial blood pressure was maintained with fluid. Animals were killed 24 hours later and examined for BT. RESULTS Increased IAP resulted in a decrease of MBF to 63% of baseline despite maintaining normal mean arterial blood pressure. BT occurred principally to the mesenteric lymph nodes after 60 minutes of IAP at 25 mm Hg. CONCLUSIONS Increased IAP leads to decreased MBF and to BT, which may contribute to later septic complications and organ failure.

Blunt cerebrovascular injury practice management guidelines: the Eastern Association for the Surgery of Trauma.

BACKGROUND Blunt injury to the carotid or vertebral vessels (blunt cerebrovascular injury [BCVI]) is diagnosed in approximately 1 of 1,000 (0.1%) patients hospitalized for trauma in the United States with the majority of these injuries diagnosed after the development of symptoms secondary to central nervous system ischemia, with a resultant neurologic morbidity of up to 80% and associated mortality of up to 40%. With screening, the incidence rises to 1% of all blunt trauma patients and as high as 2.7% in patients with an Injury Severity Score of >or=16. The Eastern Association for the Surgery of Trauma organization Practice Management Guidelines committee set out to develop an EBM guideline for the screening, diagnosis, and treatment of BCVI. METHODS A computerized search of the National Library of Medicine/National Institute of Health, Medline database was performed using citations from 1965 to 2005 inclusive. Titles and abstracts were reviewed to determine relevance, and isolated case reports, small case series, editorials, letters to the editor, and review articles were eliminated. The bibliographies of the resulting full-text articles were searched for other relevant citations, and these were obtained as needed. These papers were reviewed based on the following questions: 1. What patients are of high enough risk, so that diagnostic evaluation should be pursued for the screening and diagnosis of BCVI? 2. What is the appropriate modality for the screening and diagnosis of BCVI? 3. How should BCVI be treated? 4. If indicated, for how long should antithrombotic therapy be administered? 5. How should one monitor the response to therapy? RESULTS One hundred seventy-nine articles were selected for review, and of these, 68 met inclusion criteria and are excerpted in the attached evidentiary table and used to make recommendations. CONCLUSIONS The East Practice Management Guidelines Committee suggests guidelines that should be safe and efficacious for the screening, diagnosis, and treatment of BCVI. Risk factors for screening are identified (see ), screening modalities are reviewed indicating that although angiography remains the gold standard, multi-planar (>or==8 slice) CT angiography may be equivalent, and treatment algorithms are evaluated. It is noted that change in the diagnosis and management of this injury constellation is rapid due to technological advancement and the difficulties inherent in performing randomized prospective trials in this patient population.

Clinical Practice Guideline: Endpoints of Resuscitation

STATEMENT OF THE PROBLEM Severely injured trauma victims are at high risk of development of the multiple organ dysfunction syndrome (MODS) or death. To maximize chances for survival, treatment priorities must focus on resuscitation from shock (defined as inadequate tissue oxygenation to meet tissue O2 requirements), including appropriate fluid resuscitation and rapid hemostasis. Inadequate tissue oxygenation leads to anaerobic metabolism and resultant tissue acidosis. The depth and duration of shock leads to a cumulative oxygen debt. Resuscitation is complete when the oxygen debt has been repaid, tissue acidosis eliminated, and normal aerobic metabolism restored in all tissue beds. Many patients may appear to be adequately resuscitated based on normalization of vital signs, but have occult hypoperfusion and ongoing tissue acidosis (compensated shock), which may lead to organ dysfunction and death. Use of the endpoints discussed in this guideline may allow early detection and reversal of this state, with the potential to decrease morbidity and mortality from trauma. Without doubt, resuscitation from hemorrhagic shock is impossible without hemostasis. Fluid resuscitation strategies before obtaining hemostasis in patients with uncontrolled hemorrhage, usually victims of penetrating trauma, remain controversial. Withholding fluid resuscitation may lead to death from exsanguination, whereas aggressive fluid resuscitation may disrupt the clot and lead to more bleeding. “Limited,” “hypotensive,” and/or “delayed” fluid resuscitation may be beneficial, but clinical trials have yielded conflicting results. This clinical practice guideline will focus on resuscitation after achieving hemostasis and will not address the issue of uncontrolled hemorrhage further. Use of the traditional markers of successful resuscitation, including restoration of normal blood pressure, heart rate, and urine output, remain the standard of care per the Advanced Trauma Life Support Course. When these parameters remain abnormal, i.e., uncompensated shock, the need for additional resuscitation is clear. After normalization of these parameters, up to 85% of severely injured trauma victims still have evidence of inadequate tissue oxygenation based on findings of an ongoing metabolic acidosis or evidence of gastric mucosal ischemia. This condition has been described as compensated shock. Recognition of this state and its rapid reversal are critical to minimize risk of MODS or death. Consequently, better markers of adequate resuscitation for severely injured trauma victims are needed. This guideline committee sought to evaluate the current state of the literature regarding use of potential markers and related goals of resuscitation, focusing on those that have been tested in human trauma victims. This manuscript is part of an ongoing process of guideline development that includes periodic (every 3–4 years) review of the topic and the recommendations in light of new data. The goal is for these guidelines to assist clinicians in assuring adequate resuscitation of trauma patients, ultimately improving patient outcomes.

Clinical practice guideline: Red blood cell transfusion in adult trauma and critical care*

STATEMENT OF THE PROBLEMRed blood cell (RBC) transfusion is common in critically ill and injured patients. Many studies1–6 have documented the widespread use of RBC transfusion in critically ill patients and the data from these studies from diverse locations in Western Europe, Canada, the United Kin

Advanced Ultrasonic Diagnosis of Extremity Trauma: The FASTER Examination

BACKGROUND Ultrasound is of proven accuracy in abdominal and thoracic trauma and may be useful for diagnosing extremity injury in situations where radiography is not available such as military and space applications. We prospectively evaluated the utility of extremity ultrasound performed by trained, nonphysician personnel in patients with extremity trauma to simulate remote aerospace or military applications. METHODS Patients with extremity trauma were identified by history, physical examination, and radiographic studies. Ultrasound examination was performed bilaterally by nonphysician personnel, blinded to radiographic results, with a portable ultrasound device using a 10- to 5-MHz linear probe. Images were videorecorded for later analysis against radiography by Fishers exact test. RESULTS There were 158 examinations performed in 95 patients. The average time of examination was 4 minutes. Ultrasound accurately diagnosed extremity injury in 94% of patients with no false-positive examinations; accuracy was greater in midshaft locations and least in the metacarpal/metatarsals. Soft tissue/tendon injury was readily visualized. CONCLUSION Extremity ultrasound can be performed quickly and accurately by nonphysician personnel with excellent accuracy. Pulmonary ultrasound appears promising; blinded verification of the utility of ultrasound in patients with extremity injury should be performed to determine whether extremity and respiratory evaluation should be added to the FAST examination (the FASTER examination) and to verify the technique in remote locations such as military and aerospace applications.

Gallbladder and biliary tract candidiasis

BACKGROUND The clinical significance of Candida spp isolated from the gallbladder on the biliary tract is relatively unknown. METHODS To provide this information, patients with Candida spp isolated from gallbladder and other biliary tract sources during a 10-year period were identified through the records of our clinical microbiology laboratory. Medical records were analyzed for biliary disease causes, culture data, treatment, and outcome. RESULTS Twenty-seven patients were identified. Five of seven patients with cholecystitis were critically ill intensive care unit (ICU) patients in whom the mortality rate was 100%. Gallstone pancreatitis was found in four patients and was fatal in one patient with a pancreatic abscess and ongoing retroperitoneal sepsis. An external biliary shunt/endoprosthesis was placed in 16 patients to relieve biliary obstruction. Cholangitis was present in 14 patients, and most bile cultures contained Candida as part of a mixed flora. Only 3 of 27 patients had candidemia, and 22 of 27 patients were colonized with Candida at other sites. CONCLUSIONS (1) The ICU patient with Candida cholecystitis has a grave prognosis. (2) Patients with Candida isolated from biliary stents placed for obstruction and cholangitis should be treated with both antifungal and broad spectrum antimicrobial agents. (3) Candidemia is not frequently seen in this setting.

Effects of Increasing Airway Pressure and Peep on the Assessment of Cardiac Preload

BACKGROUND Cardiac preload is most commonly assessed by pulmonary artery wedge pressure. It was postulated that the right ventricular end-diastolic volume index (RVEDVI) derived by thermodilution would be a better predictor of preload in trauma patients with high airway pressures associated with positive pressure ventilation and positive end-expiratory pressure. METHODS Volumetric thermodilution catheters were placed in 52 mechanically ventilated trauma patients. Regression analysis was performed on 986 sets of hemodynamic data comparing pulmonary artery wedge pressure and RVEDVI to cardiac index (CI) at various airway pressures. RESULTS There was much better correlation between RVEDVI and CI (r = 0.41) than with pulmonary artery wedge pressure and CI (r = -0.06). This was true of all levels of airway pressure tested. When analyzed by the degree of right ventricular dysfunction, as indexed by right ventricular ejection fraction, the strongest correlation between RVEDVI and CI was noted when right ventricular ejection fraction was > 30%. CONCLUSIONS Unlike the pulmonary artery wedge pressure, RVEDVI is as reliable indicator of preload in the mechanically ventilated trauma patient. This is especially true when the right ventricular ejection fraction is not severely depressed.