Patrick M. Reilly

PHARMACOLOGIC APPROACH TO TISSUE INJURY MEDIATED BY FREE-RADICALS AND OTHER REACTIVE OXYGEN METABOLITES

Highly toxic metabolites of oxygen are generated normally by aerobic metabolism in most cells, and this generation is often greatly increased in pathologic conditions. When this oxidant flux exceeds the capability of the multiple endogenous antioxidant mechanisms, tissue injury ensues. The pharmacologic modification of this injury process, with agents that scavenge these reactive oxygen metabolites, block their generation, or enhance the endogenous antioxidant capability, has shown great promise in animal models of common clinical conditions, and has already been successfully applied in controlled clinical trials. This approach represents an interruption of tissue injury at its most basic level.

Both primary and secondary abdominal compartment syndrome can be predicted early and are harbingers of multiple organ failure

BACKGROUND Primary abdominal compartment syndrome (ACS) is a known complication of damage control. Recently secondary ACS has been reported in patients without abdominal injury who require aggressive resuscitation. The purpose of this study was to compare the epidemiology of primary and secondary ACS and develop early prediction models in a high-risk cohort who were treated in a similar fashion. METHODS Major torso trauma patients underwent standardized resuscitation and had prospective data collected including occurrence of ACS, demographics, ISS, urinary bladder pressure, gastric tonometry (GAP(CO2) = gastric regional CO(2) minus end tidal CO(2)), laboratory, respiratory, and hemodynamic data. With primary and secondary ACS as endpoints, variables were tested by uni- and multivariate logistic analysis (MLA). RESULTS From 188 study patients during the 44-month period, 26 (14%) developed ACS-11 (6%) were primary ACS and 15 (8%) secondary ACS. Primary and secondary ACS had similar demographics, shock, and injury severity. Significant univariate differences included: time to decompression from ICU admit (600 +/- 112 vs. 360 +/- 48 min), Emergency Department (ED) crystalloid (4 +/- 1 vs. 7 +/- 1 L), preICU crystalloid (8 +/- 1 vs. 12 +/- 1L), ED blood administration (2 +/- 1 vs. 6 +/- 1 U), GAP(CO2) (24 +/- 3 vs. 36 +/- 3 mmHg), requiring pelvic embolization (9 vs. 47%), and emergency operation (82% vs. 40%). Early predictors identified by MLA of primary ACS included hemoglobin concentration, GAP(CO2), temperature, and base deficit; and for secondary ACS they included crystalloid, urinary output, and GAP(CO2). The areas under the receiver-operator characteristic curves calculated upon ICU admission are primary= 0.977 and secondary= 0.983. Primary and secondary ACS patients had similar poor outcomes compared with nonACS patients including ventilator days (primary= 13 +/- 3 vs. secondary= 14 +/- 3 vs. nonACS = 8 +/- 2), multiple organ failure (55% vs. 53% vs. 12%), and mortality (64% vs. 53% vs. 17%). CONCLUSION Primary and secondary ACS have similar demographics, injury severity, time to decompression from hospital admit, and bad outcome. 2 degrees ACS is an earlier ICU event preceded by more crystalloid administration. With appropriate monitoring both could be accurately predicted upon ICU admission.

Evolution in damage control for exsanguinating penetrating abdominal injury.

OBJECTIVE Damage control (DC) has proven valuable in exsanguinated patients. The purpose of this study was to quantify and qualify the impact of current damage control principles applied in a penetrating abdominal injury (PAI) population. METHODS Over a 3-year period (June 1997-May 2000), of 271 laparotomies for PAI, 24 patients underwent DC (8.9%). Demographics, injury grade, resuscitative and operative parameters, acid-base status, coagulation profiles, fluid/transfusion requirements, definitive repairs, abdominal closure, complications, and outcomes were reviewed. Data were compared with our DC experience a decade earlier. Fishers exact test was used for comparisons. RESULTS Overall survival improved for equivalent Injury Severity Score, Revised Trauma Score, TRISS, admission systolic blood pressure, operating room systolic blood pressure, and Penetrating Abdominal Trauma Index score. Solids (1.2 vs. 1.3), hollow organ (1.5 vs. 1.7), and major vascular injuries (0.5 vs. 0.8) per patient remain unchanged. Currently, there was less hypothermia with equivalent operating room times. In intensive care unit survivors, acid-base status was similar but coagulopathy and hypothermia were less severe. Definitive colon management has shifted from ostomies to anastomoses. Eventual fascial closure occurred in 14 of 19 (74%) compared with 12 of 14 (86%) in the historical group. There were three gastrointestinal fistulae (one pancreatic), one anastomotic leak, and three intra-abdominal abscesses. CONCLUSION Continued application of DC principles has led to improved survival with PAI. Better control of temperature, experience with the open abdomen, and intensive care unit care may be causative.

Effects of an organized critical care service on outcomes and resource utilization: A cohort study

OBJECTIVE To determine whether the presence of an on-site, organized, supervised critical service improves care and decreases resource utilization. DESIGN The study compared two patient cohorts admitted to a surgical intensive care unit during the same period of time. The study cohort was cared for by an on-site critical care team supervised by an intensivist. The control cohort was cared for by a team with patient care responsibilities in multiple sites supervised by a general surgeon. The main outcome measures were duration of stay, resource utilization, and complication rate. SETTING Study patients were general surgical patients in an academic medical center. RESULTS Despite having higher Acute Physiology and Chronic Health Evaluation II scores, patients cared for by the critical care service spent less time in the surgical intensive care unit, used fewer resources, had fewer complications and had lower total hospital charges. The difference between the two cohorts was most evident in patients with the worst APACHE II score. CONCLUSIONS Critical care interventions are expensive and have a narrow safety margin. It is essential to develop structured and validated approaches to study the delivery of this resource. In this study, the critical care service model performed favorably both in terms of quality and cost.

Vasoactive mediators and splanchnic perfusion

ObjectiveTo provide an overview of the splanchnic hemodynamic response to circulatory shock. Data SourcesPrevious studies performed in our own laboratory, as well as a computerassisted search of the English language literature (MEDLINE, 1966 to 1991), followed by a selective review of pertinent articles. Study SelectionStudies were selected that demonstrated relevance to the splanchnic hemodynamic response to circulatory shock, either by investigating the pathophysiology or documenting the sequelae. Article selection included clinical studies as well as studies in appropriate animal models. Data ExtractionPertinent data were abstracted from the cited articles. Results of Data SynthesisThe splanchnic hemodynamic response to circulatory shock is characterized by a selective vasoconstriction of the mesenteric vasculature mediated largely by the renin-angiotensin axis. This vasospasm, while providing a natural selective advantage to the organism in mild-to-moderate shock (preserving relative perfusion of the heart, kidneys, and brain), may, in more severe shock, cause consequent loss of the gut epithelial barrier, or even hemorrhagic gastritis, ischemic colitis, or ischemic hepatitis. From a physiologic standpoint, nonpulsatile cardiopulmonary bypass, a controlled form of circulatory shock, has been found experimentally to significantly increase circulating levels of angiotensin II, the hormone responsible for this selective splanchnic vasoconstriction. ConclusionsWhile angiotensin II has been viewed primarily as the mediator responsible for the increased total vascular resistance seen during (and after) cardiopulmonary bypass, it may also cause the disproportionate decrease in mesenteric perfusion, as measured in human subjects by intraluminal gastric tonometry and galactose clearance by the liver, as well as the consequent development of the multiple organ failure syndrome seen in 1% to 5% of patients after cardiac surgery. (Crit Care Med 1993; 21:S55-S68)

The mesenteric hemodynamic response to circulatory shock: an overview.

ABSTRACT— The mesenteric hemodynamic response to circulatory shock is characteristic and profound; this vasoconstrictive response disproportionately affects both the mesenteric organs and the organism as a whole. Vasoconstriction of post‐capillary mesenteric venules and veins, mediated largely by the &agr;‐adrenergic receptors of the sympathetic nervous system, can effect an “autotransfusion” of up to 30% of the total circulating blood volume, supporting cardiac filling pressures (“preload”), and thereby sustaining cardiac output at virtually no cost in nutrient flow to the mesenteric organs. Under conditions of decreased cardiac output caused by cardiogenic or hypovolemic shock, selective vasoconstriction of the afferent mesenteric arterioles serves to sustain total systemic vascular resistance (“afterload”), thereby maintaining systemic arterial pressure and sustaining the perfusion of non‐mesenteric organs at the expense of mesenteric organ perfusion (Cannons “flight or fight” response). This markedly disproportionate response of the mesenteric resistance vessels is largely independent of the sympathetic nervous system and variably related to vasopressin, but mediated primarily by the renin‐angiotensin axis. The extreme of this response can lead to gastric stress erosions, nonocclusive mesenteric ischemia, ischemic colitis, ischemic hepatitis, ischemic cholecystitis, and/or ischemic pancreatitis. Septic shock can produce decreased or increased mesenteric perfusion, but is characterized by an increased oxygen consumption that exceeds the capacity of mesenteric oxygen delivery, resulting in net ischemia and consequent tissue injury. Mesenteric organ injury from ischemia/reperfusion due to any form of shock can lead to a triggering of systemic inflammatory response syndrome, and ultimately to multiple organ dysfunction syndrome. The mesenteric vasculature is therefore a major target and a primary determinant of the systemic response to circulatory shock.

National Survey of the Incidence of Cervical Spine Injury and Approach to Cervical Spine Clearance in U.s. Trauma Centers

BACKGROUND The overall incidence of cervical spine injury (CSI) has been estimated from small studies; the incidence of specific injury types is less well established. The approach to screening for CSI has not been well studied; variation may exist based on Trauma Center (TC) level and type (academic vs. nonacademic). We attempted to define the incidence of different types of CSI and determine whether a national standard for cervical spine clearance (CSC) could be identified. We hypothesized a significant variation in incidence of CSI and approach to CSC based on TC level and type. METHODS In a survey of 615 TC, institutions were asked to describe themselves as academic/nonacademic and provide a Level I-IV. Questions concerned demographics, Injury Severity Score, incidence of CSI, clinical resources, and approach to CSC. Methods of CSC included protocols, use of flexion-extension films, computed tomography, magnetic resonance imaging, and cervical collars. Clinical scenarios examined indications and technique for CSC. RESULTS A total of 637 surveys were sent to 615 TC (25 follow-ups), and 165 TC (25%) responded. A total of 156 TC provided data for type: academic 44 (28%), nonacademic 112 (72%). A total of 142 TC provided data for level: 49 (34%) Level I, 75 (53%), Level II, 18 (13%), Level III. A total of 111,219 patients were entered into the trauma registries of these TC. The overall incidence of all types of CSI was 4.3%, CSI without spinal cord injury was 3.0%, spinal cord injury without fracture was 0.70%, and delayed diagnosis of all types of CSI was 0.01%. There was no difference in the incidence of CSI overall or by subtype based on TC level or type. Injury Severity Score correlated with incidence of CSI without cord injury (r = 0.387, p < 0.01). Regarding approach to CSC, differences existed by TC level and type for responsibility for CSC and protocols for CSC (p < 0.05). Level II TC felt early flexion-extension views were potentially harmful (60%); Level I TC did not (39%) (p < 0.05). Regarding indications for CSC, there was agreement on 10 of 11 clinical scenarios. For three of five clinical scenarios examining radiographic approach to CSC there was a broad distribution of approaches to patients with normal radiographs and cervical pain, altered mental status, coma. CONCLUSION Incidence of CSI is uniform by TC level and type. Incidence of spinal cord injury without fracture is low: 0.7%. Reported rate of missed CSI is very low: 0.01%. There is good agreement (>78%) among TC on indications for CSC but less agreement on radiographic approach to CSC.

An Acute Care Surgery Model Improves Outcomes in Patients With Appendicitis

Objective:To compare outcomes of appendectomy in an Acute Care Surgery (ACS) model to that of a traditional home-call attending surgeon model. Summary Background Data:Acute care surgery (ACS, a combination of trauma surgery, emergency surgery, and surgical critical care) has been proposed as a practice model for the future of general surgery. To date, there are few data regarding outcomes of surgical emergencies in the ACS model. Methods:Between September 1999 and August 2002, surgical emergencies were staffed at the faculty level by either an in-house trauma/emergency surgeon (ACS model) or a non-trauma general surgeon taking home call (traditional [TRAD] model). Coverage alternated monthly. Other aspects of hospital care, including resident complement, remained unchanged. We retrospectively reviewed key time intervals (emergency department [ED] presentation to surgical consultation; surgical consultation to operation [OR]; and ED presentation to OR) and outcomes (rupture rate, negative appendectomy rate, complication rate, and hospital length of stay [LOS]) for patients treated in the ACS and TRAD models. Questions of interest were examined using χ2 tests for discrete variables and independent sample t test for comparison of means. Results:During the study period, 294 appendectomies were performed. In-house ACS surgeons performed 167 procedures, and the home-call TRAD surgeons performed 127 procedures. No difference was found in the time from ED presentation to surgical consultation; however, the time interval from consultation to OR was significantly decreased in the ACS model (TRAD 7.6 hours vs. ACS 3.5 hours, P < 0.05). As a result, the total time from ED presentation to OR was significantly shorter in the ACS model (TRAD 14.0 hours vs. ACS 10.1 hour, P < 0.05). Rupture rates were decreased in the ACS model (TRAD 23.3% vs. ACS 12.3%, P < 0.05); negative appendectomy rates were similar. The complication rate in the ACS model was decreased (TRAD 17.4% vs. ACS 7.7%, P < 0.05), as was the hospital LOS (TRAD 3.5 days vs. ACS 2.3 days, P < 0.001). Conclusions:In patients with acute appendicitis, the presence of an in-house acute care surgeon significantly decreased the time to operation, rupture rate, complication rate, and hospital length of stay. The ACS model appears to improve outcomes of acute appendicitis compared with a TRAD home-call model. This study supports the efficacy and efficiency of the ACS model in the management of surgical emergencies.

Experience with the recovery filter as a retrievable inferior vena cava filter.

PURPOSE This study evaluates clinical experience with the Recovery filter as a retrievable inferior vena cava (IVC) filter. MATERIALS AND METHODS One hundred seven Recovery filters were placed in 106 patients with an initial clinical indication for temporary caval filtration. Patients were followed up to assess filter efficacy, complications, eventual need for filter removal, time to retrieval, and ability to remove the filter. RESULTS The patient cohort consisted of 62 men and 44 women with a mean age of 48 years (range, 18-90 y). Mean implantation time was 165 days. Indications for filter placement in patients with deep vein thrombosis (DVT) and/or pulmonary embolism (PE) included contraindication to anticoagulation (n = 33), complications of anticoagulation (n = 8), poor cardiopulmonary reserve (n = 6), large clot burden (n = 3), and PE while receiving anticoagulation (n = 1). Indications for filter placement in patients without proven PE or DVT included immobility after trauma (n = 35); recent intracranial hemorrhage, neurosurgery, or brain tumor (n = 18); and other surgical or invasive procedure (n = 3). Three patients (2.8%) had symptomatic PE after placement of the Recovery filter. No caval thromboses were detected. No symptomatic filter migrations occurred. Recovery filter removal was attempted in 15 of 106 patients (14%) at a mean of 150 days after placement. The Recovery filter was successfully retrieved in 14 of 15 patients (93%); one removal was unsuccessful at 210 days after placement. Ninety-two filters (87%) currently remain in place. CONCLUSIONS Although all the filters were placed with the intention of being removed, a large percentage of filters were not retrieved. The Recovery filter was safe and effective in preventing PE when used as a retrievable IVC filter.

Hypercarbia during tracheostomy: a comparison of percutaneous endoscopic, percutaneous Doppler, and standard surgical tracheostomy

Objective: Tracheostomy is one of the most commonly performed surgical procedures in the critical care setting. The early use of tracheostomy as a method of primary airway management has been proposed as a means to decrease pulmonary morbidity and to shorten the number of ventilator, intensive care unit, and hospital days. We set out to (1) determine whether hypercarbia occurs during tracheostomy of the critically ill patient and (2) determine the extent to which the partial pressure of carbon dioxide in arterial blood (PaCO2) rises during percutaneous endoscopic, percutaneous Doppler, and standard surgical tracheostomy. Design: Prospective, open clinical trial. Setting: Surgical intensive care unit and operating room in teaching hospitals. Patients: During mechanical ventilation, patients underwent either percutaneous endoscopic (PET), percutaneous Doppler (PDT), or standard surgical tracheostomy (ST), based on surgeon preference. Arterial blood gas readings were obtained approximately every 4 min throughout each procedure. Measurements and results: All tracheostomies were successfully performed. No serious complications (including hypoxia) occurred during the study. Significant (p < 0.05 vs PDT and ST) hypercarbia (maximum Δ PaCO2 24 ± 3 mmHg) and acidosis (maximum Δ pH – 0.16 ± 0.02) developed during PET. The changes in PaCO2 and pH during PDT (maximum Δ PaCO2 8 ± 2 mmHg; maximum Δ pH – 0.07 ± 0.02) and ST (maximum Δ PaCO2 3 ± 1 mmHg; maximum ΔpH – 0.04 ± 0.01) were markedly less pronounced. Conclusions: Continuous bronchoscopy during percutaneous tracheostomy contributes significantly to early hypoventilation, hypercarbia, and respiratory acidosis during the procedure. Percutaneous tracheostomy, when performed using the Doppler ultrasound method to position the endotracheal tube, significantly reduces CO2 retention when compared to PET. Because of a possible rise in intracranial pressure, the potential for hypercarbia should be considered when choosing the method of tracheostomy in the critically ill and/or head-injured patient, where hypercarbia may be detrimental. If PET is to be performed, steps to minimize occult hypercarbia, such as using the smallest bronchoscope available, minimizing suctioning during bronchoscopy, and minimizing the length of time the bronchoscope is in the endotracheal tube, should be undertaken.