CD4+ T cell depletion during all stages of HIV disease occurs predominantly in the gastrointestinal tract.

The mechanisms underlying CD4(+) T cell depletion in human immunodeficiency virus (HIV) infection are not well understood. Comparative studies of lymphoid tissues, where the vast majority of T cells reside, and peripheral blood can potentially illuminate the pathogenesis of HIV-associated disease. Here, we studied the effect of HIV infection on the activation and depletion of defined subsets of CD4(+) and CD8(+) T cells in the blood, gastrointestinal (GI) tract, and lymph node (LN). We also measured HIV-specific T cell frequencies in LNs and blood, and LN collagen deposition to define architectural changes associated with chronic inflammation. The major findings to emerge are the following: the GI tract has the most substantial CD4(+) T cell depletion at all stages of HIV disease; this depletion occurs preferentially within CCR5(+) CD4(+) T cells; HIV-associated immune activation results in abnormal accumulation of effector-type T cells within LNs; HIV-specific T cells in LNs do not account for all effector T cells; and T cell activation in LNs is associated with abnormal collagen deposition. Taken together, these findings define the nature and extent of CD4(+) T cell depletion in lymphoid tissue and point to mechanisms of profound depletion of specific T cell subsets related to elimination of CCR5(+) CD4(+) T cell targets and disruption of T cell homeostasis that accompanies chronic immune activation.

Near-infrared spectroscopy in patients with severe sepsis: correlation with invasive hemodynamic measurements.

BACKGROUND: Clinicians have begun using near-infrared spectroscopy (NIRS) to monitor tissue perfusion in hemorrhagic shock, as the technique allows continuous noninvasive monitoring of tissue hemoglobin oxygen saturation (StO(2)) and the tissue hemoglobin index (THI). We hypothesized that StO(2) measurements in patients with severe sepsis would be associated with the severity of their illness and would correlate with invasive hemodynamic measurements. METHODS: We measured mean arterial pressure (MAP), serum lactate concentration, blood hemoglobin concentration, StO(2), and THI in nine healthy volunteers and ten patients with septic shock in a surgical intensive care unit (ICU). Enrolled patients had a pulmonary artery catheter, and had family able to give informed consent. The average Acute Physiology and Chronic Health Evaluation (APACHE) II score at enrollment for the patients was 19 +/- 5 (standard deviation) points. Volunteers and patients were similar with respect to age and sex. To collect NIRS data, we used the InSpectra Tissue Spectrometer, Model 325 (Hutchinson Technology, Inc., Hutchinson, MN). For three consecutive days, we obtained invasive hemodynamic measurements three times daily, simultaneously with NIRS measurements, and metabolic cart measurements once daily. RESULTS: Patients with severe sepsis had significantly lower thenar muscle StO(2) values (p = 0.031) than healthy volunteers. Near-infrared spectroscopy-derived mixed venous oxygen saturation (NIRSvO(2)) and StO(2) measured from the thenar eminence in patients with severe sepsis correlated with SvO(2) from the pulmonary artery catheter (p < 0.05). In this group of patients, StO(2) did not correlate significantly with lactate concentration, base deficit, or APACHE II score. CONCLUSIONS: Near-infrared spectroscopic measurements of StO(2) correlated with invasive hemodynamic measurements in patients with severe sepsis but did not correlate with severity of illness. These findings suggest that NIRStO(2) may be a clinically useful measurement in monitoring patients with severe sepsis. Further study of this device in early resuscitation of patients with sepsis is necessary.

Dynamic near-infrared spectroscopy measurements in patients with severe sepsis.

This study evaluated near-infrared spectroscopy (NIRS)-derived measurements in hemodynamically stable patients with severe sepsis, as compared with similar measurements in healthy age-matched volunteers. Prospective, preliminary, observational study in a surgical intensive care unit and clinical research center at a university health center. We enrolled 10 patients with severe sepsis and 9 healthy age-matched volunteers. For patients with severe sepsis, we obtained pulmonary artery catheter and laboratory values three times daily for 3 days and oxygen consumption values via metabolic cart once daily for 3 days. For healthy volunteers, we obtained all noninvasive measurements during a single session. We found lower values in patients with severe sepsis (versus healthy volunteers), in tissue oxygen saturation (StO2), in the StO2 recovery slope, in the tissue hemoglobin index, and in the total tissue hemoglobin increase on venous occlusion. Patients with severe sepsis had longer StO2 recovery times and lower NIRS-derived local oxygen consumption values versus healthy volunteers. In our preliminary study, NIRS provides a noninvasive continuous method to evaluate peripheral tissue oxygen metabolism in hemodynamically stable patients with severe sepsis. Further research is needed to demonstrate whether these values apply to broader populations of patients with systemic inflammatory response syndrome, sepsis, severe sepsis, and septic shock.

Inguinal lymph node biopsy in patients infected with the human immunodeficiency virus is safe.

BACKGROUND AND PURPOSE: The incidence of postoperative complications in human immunodeficiency virus (HIV)-infected patients remains controversial. Published data suggest that these patients are at higher risk for postoperative surgical site infections (SSIs) than are uninfected patients if the site is contaminated. To determine the incidence of postoperative SSI in HIV-infected patients undergoing aseptic surgery at uncontaminated sites, we performed a prospective case series analysis. We hypothesized that the rate of postoperative SSI would be low for this aseptic procedure, irrespective of CD4(+) lymphocyte counts. Additionally, we monitored the rates of other complications, namely, hematoma, dorsal vein thrombosis, epididymitis, lymphocele, and suture extrusion. METHODS: From May 1, 2000, through January 31, 2006, we performed 137 sterile inguinal lymph node biopsies in 44 HIV-infected patients as part of a funded study evaluating the role of peripheral lymphatic tissue in the pathophysiology of HIV infection. Postoperatively, we followed all patients for a minimum of 30 days. RESULTS: Postoperatively, we noted one instance each (0.7%) of infection, dorsal vein thrombosis with epididymitis (0.7%), and lymphocele and two cases each (1.4%) of hematoma and suture extrusion. The CD4(+) count at the time of biopsy did not correlate with postoperative complications. CONCLUSIONS: Inguinal lymph node biopsy in HIV-infected patients is safe, irrespective of CD4(+) lymphocyte count.

Kinetic therapy beds are associated with more complications in patients with thoracolumbar spinal column injuries.

BACKGROUND AND PURPOSE: Traumatic spine injuries are an important cause of morbidity and mortality. Kinetic therapy (KT) beds were designed to minimize skin breakdown and enhance clearance of pulmonary secretions by rotating the patient from side to side. However, little evidence exists to suggest that fewer complications occur in patients with thoracolumbar spine injuries (TLSIs) treated preoperatively with a KT bed. We investigated the effect of KT bed use on infectious complications and respiratory failure in patients requiring surgery for TLSIs. METHODS: We queried the trauma registry of a Level 1 trauma center for patients who had surgery for a TLSI from January 1, 1994, through June 30, 2001, and performed a retrospective medical record review. Patients were divided into two groups according to whether they were treated with a KT bed preoperatively. Patient data included age, injury severity score (ISS), admission Glasgow Coma Scale score (GCS), time to surgery, narcotics administered in total and during the first 24 h after injury, the lowest recorded systolic blood pressure, and acute resuscitation volume requirement. Outcome data included infectious complications, neurologic deficits, respiratory failure, hospital length of stay (LOS), and number of days of ventilator support. Infectious complications included pneumonia, urinary tract infections, and surgical site infections. RESULTS: Patients treated with a KT bed and patients treated with a conventional bed were similar in age, ISS, admission GCS, time to surgery, total narcotics administered, lowest recorded systolic blood pressure, and resuscitation requirement during the first 24 h. However, patients with neurologic deficits were more frequently treated with a KT bed. Infectious complications were more common in patients receiving KT bed therapy than among those on conventional beds. The incidence of respiratory failure, the number of days of ventilator support, and hospital LOS also were significantly higher in patients treated with KT beds. The variables most predictive of infectious complications were the number of days of ventilator support, the amount of fluid administered during the first 24 h, and KT bed therapy (r2 = 0.459). CONCLUSIONS: Patients with TLSIs treated with a KT bed had a higher incidence of infectious complications and respiratory failure and more days of ventilator support than patients treated with a conventional bed despite similar ISS and time to surgical repair. The longer hospital LOS in patients treated with a KT bed may be secondary to the higher incidence of infectious complications and respiratory failure and the greater number of days of ventilator support.

Ringer's ethyl pyruvate in hemorrhagic shock and resuscitation does not improve early hemodynamics or tissue energetics.

Reactive oxygen species (ROS) have been implicated in the pathogenesis of hemorrhagic shock. Ethyl pyruvate, a derivative of pyruvate and a proposed oxygen radical scavenger, is attractive as a possible resuscitation fluid. We investigated whether resuscitation with lactated Ringer's (LR) containing ethyl pyruvate (REP) had any hemodynamic or tissue energetic benefits compared with LR alone for hemorrhagic shock. Hemorrhagic shock was induced in splenectomized pigs via inferior vena cava cannula. After 90 min of shock, animals were resuscitated in a stepwise fashion with LR or REP (30 mg/kg/dose, given as 1.5 mg/mL in LR) at 20 cc/kg/step for four steps. Data collected during this experiment included physiologic and hemodynamic parameters, near-infrared reflectance spectroscopy measurements of tissue hemoglobin oxygen (StO(2)) of the stomach, liver, and hind limb, and nuclear magnetic resonance phosphorus spectra of the liver and hind limb at each time point. In both resuscitative groups, heart rate, and lactate and pyruvate values increased during shock and began to drop toward baseline values during resuscitation. Mean arterial pressure, oxygen delivery, and oxygen consumption decreased during shock and increased toward baseline levels during the resuscitative process. There were no significant changes in physiologic parameters between the LR- and REP-resuscitated animals. There was a significantly lower stomach StO(2) and hind limb cellular cytoplasmic pH during later resuscitative endpoints in REP-resuscitated animals. The clinical significance of these findings are unclear. There is no short-term hemodynamic or tissue energetic advantage to using REP as a resuscitation fluid when compared with LR. Long-term outcome studies are needed to further evaluate any potential benefits of use of REP in hemorrhagic shock.

Hyperglycemia in the intensive care unit: no longer just a marker of illness severity.

BACKGROUND: Hyperglycemia is a common occurrence in critically ill patients. Recent evidence has demonstrated improved survival in patients in surgical intensive care units (SICUs) receiving "tight glycemic control." The mechanisms of this survival advantage are not well understood. METHODS: A review of the English language literature pertaining to potential mechanisms affecting outcome in critically ill patients receiving insulin therapy, including recently published human trials evaluating mortality outcomes. RESULTS: This review discusses the results of clinical trials of "tight glycemic control," considers mechanisms of hyperglycemia in critical illness, and reviews potential mechanisms of improved outcome related in the critically ill patient. CONCLUSIONS: A number of human studies have demonstrated improved outcomes in critically ill patient populations receiving insulin therapy with a target of euglycemia, suggesting at least part of the benefit of this therapy is normal blood sugar and not the effects of insulin. An important population not studied to date is patients in the medical ICU. However, aggressive control of hyperglycemia now remains an important component of care for all surgical patients in the ICU.

Abdominal complications of ventricular assist device placement.

BACKGROUND: Ventricular assist devices (VADs) provide a bridge to transplantation for patients awaiting heart transplant. Because of its intra-abdominal placement, the potential exists for major abdominal complications. The purpose of this study is to identify VAD-associated abdominal complications and their incidence, and to describe preventive measures. METHODS: Records of patients having had VAD placement were identified from our registry from April 12, 1995, when the first VAD placement occurred, to July 15, 2003. Each patient was evaluated for the occurrence of an abdominal complication, defined as mechanical small bowel obstruction, infection with an abdominal source, hernia, or other abdominal pathology occurring after VAD placement. RESULTS: One hundred twenty-four VADs were implanted in 100 patients. Of these patients, 82 received one VAD, 13 received two devices, four received three devices, and one patient received four devices. Twelve abdominal complications occurred in 11 patients (11%). There was a 36% (4/11) pre-transplant mortality rate in patients with an abdominal complication, compared to 17% (15/89) pre-transplant mortality in patients without an abdominal complication (p = 0.21). Three of five patients with abdominal infection died. CONCLUSIONS: Abdominal complications after VAD placement are common. Intra-abdominal VAD infection is the most common and serious complication, leading to a mortality rate of 60% in our population. Additionally, small bowel obstructions, incisional and inguinal hernias, acalculous cholecystitis, and pancreatitis also occurred. Appropriate preventive measures may decrease the risk of developing many of these complications.

Tissue energetics as measured by nuclear magnetic resonance spectroscopy during hemorrhagic shock.

The defect in energy production in an organism during shock states may be related to the impairment of mitochondrial respiration early in shock. The aim of this study was to investigate the timing and degree of cellular energetic changes during hemorrhagic shock in real time. Instrumented, splenectomized swine were randomized to undergo hemorrhagic shock, induced by a 35% blood volume bleed, for 90 min with (n = 10) or without (n = 9) subsequent resuscitation. Resuscitated animals received shed blood in two increments followed by two normal saline boluses (20 mL/kg/bolus). Throughout experimentation, tissue phosphoenergetics of liver and skeletal muscle were monitored using 31P nuclear magnetic resonance (NMR) spectroscopy via NMR coils on the liver and hindlimb. Near-infrared spectroscopy probes were used to measure liver, stomach, and skeletal muscle oxyhemoglobin saturation (StO2). Hemorrhagic shock induced an increase in phosphomonoesters in skeletal muscle (baseline: 7.09%, 90 min: 9.94% (P < 0.05); expressed as percent total phosphorus). This increase resolved in animals receiving resuscitation (n = 10) but remained elevated in those in unresuscitated shock (n = 9). Inorganic phosphate levels increased and betaATP levels decreased significantly in the liver of animals in shock as compared with baseline. StO2 in skeletal muscle, stomach, and liver correlated with whole organism oxygen delivery (r2 = 0.356, 0.368, and 0.432, respectively). We conclude that hemorrhagic shock induces early elevation of phosphomonoesters in skeletal muscle, which correlates with the severity of shock. This implies an early transition to anaerobic glycolysis during hemorrhagic shock, which may be indicative of early mitochondrial dysfunction.

Mononuclear cell function and energetics in early traumatic injury.

BACKGROUND: The reason for increased infectious complications after traumatic injury is complex and incompletely understood. We propose a relationship between the energetic state of circulating immune cells and immune cell function in traumatic injury. To examine this relationship, cellular adenosine triphosphate (ATP) concentration and cellular functions were measured in peripheral blood mononuclear cells from trauma patients and normal subjects. MATERIALS AND METHODS: Mononuclear cells were isolated within 24 h of injury from trauma patients without (n = 12) or with (n = 10) hypotension (groups 1 and 2, respectively), and a group of normal control subjects (group 3, n = 13). Mononuclear cells were assayed for ATP levels using bioluminescence. Phagocytosis was quantified via flow cytometry after ingestion of fluorescent microspheres and phagocytic index (PI) was calculated (average number of particles ingested per monocyte). Protein synthesis was quantified using incorporation of (35)S-labeled methionine into cultured cells. Comparisons between groups were performed using one-way analysis of variance (ANOVA) with adjustment for multiple comparisons. RESULTS: All but one trauma patient suffered blunt injury. There were significantly more transfusions in group 2 (hypotensive) patients (p = 0.0005). Nosocomial infections, length of stay (LOS), and mortality did not differ between groups 1 and 2. Concentrations of ATP and PI in both groups of traum a patients did not significantly differ from controls. In hypotensive trauma patients, increased duration of hypotension was associated with increased mononuclear cell ATP levels (r(2) = 0.227). A negative correlation between PI and ATP levels in trauma patients was discovered. Incorporation of (35)S was significantly greater in normotensive trauma patients than controls. CONCLUSION: Mononuclear cell ATP levels and measured functions are preserved in early traumatic injury.

Microwave processing for sample preparation to evaluate mitochondrial ultrastructural damage in hemorrhagic shock.

This is a report of the adaptation of microwave processing in the preparation of liver biopsies for transmission electron microscopy (TEM) to examine ultrastructural damage of mitochondria in the setting of metabolic stress. Hemorrhagic shock was induced in pigs via 35% total blood volume bleed and a 90-min period of shock followed by resuscitation. Hepatic biopsies were collected before shock and after resuscitation. Following collection, biopsies were processed for TEM by a rapid method involving microwave irradiation (Giberson, 2001). Samples pre- and postshock of each of two animals were viewed and scored using the mitochondrial ultrastructure scoring system (Crouser et al., 2002), a system used to quantify the severity of ultrastructural damage during shock. Results showed evidence of increased ultrastructural damage in the postshock samples, which scored 4.00 and 3.42, versus their preshock controls, which scored 1.18 and 1.27. The results of this analysis were similar to those obtained in another model of shock (Crouser et al., 2002). However, the amount of time used to process the samples was significantly shortened with methods involving microwave irradiation.

Use of near-infrared spectroscopy in early determination of irreversible hemorrhagic shock.

BACKGROUND: In field situations, patient triage may require early determination of patients progressing to irreversible shock. We investigated the utility of near-infrared spectroscopy (NIRS) in early detection of irreversible hemorrhagic shock. METHODS: Twenty instrumented pigs were treated with a protocol involving 35% blood volume hemorrhage, 90 minutes of shock, and stepwise resuscitation with lactated Ringer's. Hemodynamics and NIRS measurements of skeletal muscle (leg), stomach, and liver tissue oxyhemoglobin saturation (StO2) were measured at baseline, every 30 minutes during shock, and after each resuscitative step. Measurements were compared between animals that expired during resuscitation (unresuscitatable) and animals that survived all resuscitative steps (resuscitatable). RESULTS: Neither global oxygen delivery, oxygen consumption, nor lactate distinguished resuscitatable from unresuscitatable animals. Invasive measurements of SvO2 did distinguish resuscitatable from unresuscitatable animals. After the first fluid bolus, both stomach and leg StO2 differed significantly between resuscitatable and unresuscitatable animals. Regression analysis revealed skeletal muscle (leg) StO2 obtained after the first resuscitative step was a significant mortality predictor despite resuscitation (r2=0.45) (p = 0.005). CONCLUSIONS: Non-invasive NIRS monitoring of leg and stomach StO2 differentiates resuscitatable from unresuscitatable animals after the initial resuscitative bolus. Use of this non-invasive tool may guide appropriate use of resuscitative fluids and has possible point-of-care applications.

Population-based prediction of trauma volumes at a Level 1 trauma centre.

OBJECTIVE: With an ageing US population, the demographics of traumatic injuries are being significantly altered. Census projections predict that the number of Americans over age 65 will double in the next 20 years. We used stochastic methods to forecast trauma admissions in order to predict the effects of such demographic changes at our trauma centre. METHODS: Age- and sex-related rates of traumatic admission were determined using population statistics and trauma registry data from 1994 to 1999. These rates were then projected from 2000 to 2025 based on both the Lee-Carter and random walk with drift methods. Stochastic population projections were made and paired with the projected trauma rates, allowing estimation of total trauma volume. RESULTS: Trauma rates were predicted to increase for most age groups. Trauma admissions are predicted to increase 57% by 2024. By 2019, 50% of trauma admissions will be 60 or older. CONCLUSIONS: Our trauma volume is expected to increase 57% by 2024, an increase of 2% per year. More of this volume will consist of elderly patients, potentially requiring increased health-care resources.

Phosphomonoesters predict early mortality in porcine hemorrhagic shock.

BACKGROUND: Hemodynamic, laboratory, and tissue energetics were measured in a porcine model of hemorrhagic shock to evaluate variables as predictors of early mortality from shock. We hypothesized that elevated phosphomonoesters would predict early mortality in hemorrhagic shock. METHODS: Pigs (n = 36) were subjected to 35% hemorrhage for 90 minutes in a 1.5-T nuclear magnetic resonance (NMR) magnet. Measurements included base deficit (BD); lactate; oxygen consumption/delivery; near-infrared spectroscopy of liver, stomach, and skeletal muscle tissue oxyhemoglobin saturation; and NMR spectroscopic measurements of high-energy phosphates of liver and skeletal muscle. Variables were compared between nonsurvivors and survivors to resuscitation after 90-minute measurements. RESULTS: Ninety-minute mortality was 25%. Muscle phosphomonoesters (PMEs) and oxygen consumption differed significantly between survivors and nonsurvivors at baseline. Regression analysis identified baseline muscle PME levels, baseline BD, and 30-minute BD as early predictors of mortality before resuscitation (r2 = 0.304). CONCLUSION: Baseline elevation in muscle PME levels predicts mortality in an animal model of severe hemorrhagic shock.