TCR independent suppression of CD8(+) T cell cytokine production mediated by IFNγ in vivo

CD8(+) memory T cells produce IFNγ within hours of secondary infection, but this is quickly terminated in vivo despite the presence of stimulatory viral antigen, suggesting that active suppression occurs. Herein, we investigated the in vivo effector function of CD8(+) memory T cells during successive encounters with viral antigen. CD8(+) T cells in immune mice receiving prior viral or peptide challenge failed to reproduce IFNγ during LCMV rechallenge. Surprisingly, this refractory state was induced even in memory cells that had not encountered their cognate antigen, indicating that the silencing of CD8(+) T cell responses is TCR-independent. Direct injection of IFNγ also suppressed the ability of virus-specific memory cells to respond to subsequent viral challenge. We propose the existence of a negative feedback loop whereby IFNγ, produced by memory CD8(+) T cells to combat viral challenge, acts - directly or indirectly - to limit its further production.

Type I IFN Signaling Is Dispensable during Secondary Viral Infection

Innate immune responses in general, and type I interferons (T1IFNs) in particular, play an important and often essential role during primary viral infections, by directly combatting the virus and by maximizing the primary adaptive immune response. Several studies have suggested that T1IFNs also contribute very substantially to the secondary (recall) response; they are thought (i) to be required to drive the early attrition of memory T cells, (ii) to support the subsequent expansion of surviving virus-specific memory cells, and (iii) to assist in the suppression and clearance of the infectious agent. However, many of these observations were predicated upon models in which T1IFN signaling was interrupted prior to a primary immune response, raising the possibility that the resulting memory cells might be intrinsically abnormal. We have directly addressed this by using an inducible-Cre model system in which the host remains genetically-intact during the primary response to infection, and in which T1IFN signaling can be effectively ablated prior to secondary viral challenge. We report that, in stark contrast to primary infection, T1IFN signaling is not required during the recall response. IFNαβR-deficient memory CD8+ and CD4+ memory T cells undergo attrition and expansion with kinetics that are indistinguishable from those of receptor-sufficient cells. Moreover, even in the absence of functional T1IFN signaling, the host's immune capacity to rapidly suppress, and then to eradicate, a secondary infection remains intact. Thus, this study shows that T1IFN signaling is dispensable during the recall response to a virus infection. Moreover, two broader implications may be drawn. First, a T cell's requirement for a cytokine is highly dependent on the cell's maturation / differentiation status. Consequently, second, these data underscore the importance of evaluating a gene's impact by modulating its expression or function in a temporally-controllable manner.

Antigen-specific naive CD8+ T cells produce a single pulse of IFN-γ in vivo within hours of infection, but without antiviral effect

In vitro studies have shown that naive CD8(+) T cells are unable to express most of their effector proteins until after at least one round of cell division has taken place. We have reassessed this issue in vivo and find that naive CD8(+) T cells mount Ag-specific responses within hours of infection, before proliferation has commenced. Newly activated naive Ag-specific CD8(+) T cells produce a rapid pulse of IFN-γ in vivo and begin to accumulate granzyme B and perforin. Later, in vivo cytolytic activity is detectable, coincident with the initiation of cell division. Despite the rapid development of these functional attributes, no antiviral effect was observed early during infection, even when the cells are present in numbers similar to those of virus-specific memory cells. The evolutionary reason for the pulse of IFN-γ synthesis by naive T cells is uncertain, but the lack of antiviral impact suggests that it may be regulatory.

ELR(+) chemokine signaling in host defense and disease in a viral model of central nervous system disease

Intracranial infection of the neurotropic JHM strain of mouse hepatitis virus (JHMV) into the central nervous system (CNS) of susceptible strains of mice results in an acute encephalomyelitis, accompanied by viral replication in glial cells and robust infiltration of virus-specific T cells that contribute to host defense through cytokine secretion and cytolytic activity. Mice surviving the acute stage of disease develop an immune-mediated demyelinating disease, characterized by viral persistence in white matter tracts and a chronic neuroinflammatory response dominated by T cells and macrophages. Chemokines and their corresponding chemokine receptors are dynamically expressed throughout viral infection of the CNS, influencing neuroinflammation by regulating immune cell infltration and glial biology. This review is focused upon the pleiotropic chemokine receptor CXCR2 and its effects upon neutrophils and oligodendrocytes during JHMV infection and a number of other models of CNS inflammation.

CD8+ memory T cells appear exhausted within hours of acute virus infection

CD8(+) memory T cells are abundant and are activated in a near-synchronous manner by infection, thereby providing a unique opportunity to evaluate the coordinate functional and phenotypic changes that occur in vivo within hours of viral challenge. Using two disparate virus challenges of mice, we show that splenic CD8(+) memory T cells rapidly produced IFN-γ in vivo; however, within 18-24 h, IFN-γ synthesis was terminated and remained undetectable for ≥ 48 h. A similar on/off response was observed in CD8(+) memory T cells in the peritoneal cavity. Cessation of IFN-γ production in vivo occurred despite the continued presence of immunostimulatory viral Ag, indicating that the initial IFN-γ response had been actively downregulated and that the cells had been rendered refractory to subsequent in vivo Ag contact. Downregulation of IFN-γ synthesis was accompanied by the upregulation of inhibitory receptor expression on the T cells, and ex vivo analyses using synthetic peptides revealed a concurrent hierarchical loss of cytokine responsiveness (IL-2, then TNF, then IFN-γ) taking place during the first 24 h following Ag contact. Thus, within hours of virus challenge, CD8(+) memory T cells display the standard hallmarks of T cell exhaustion, a phenotype that previously was associated only with chronic diseases and that is generally viewed as a gradually developing and pathological change in T cell function. Our data suggest that, instead, the "exhaustion" phenotype is a rapid and normal physiological T cell response.

The chemokine receptor CXCR2 and coronavirus-induced neurologic disease

Inoculation with the neurotropic JHM strain of mouse hepatitis virus (MHV) into the central nervous system (CNS) of susceptible strains of mice results in an acute encephalomyelitis in which virus preferentially replicates within glial cells while excluding neurons. Control of viral replication during acute disease is mediated by infiltrating virus-specific T cells via cytokine secretion and cytolytic activity, however sterile immunity is not achieved and virus persists resulting in chronic neuroinflammation associated with demyelination. CXCR2 is a chemokine receptor that upon binding to specific ligands promotes host defense through recruitment of myeloid cells to the CNS as well as protecting oligodendroglia from cytokine-mediated death in response to MHV infection. These findings highlight growing evidence of the diverse and important role of CXCR2 in regulating neuroinflammatory diseases.

Zinc sequestration by the neutrophil protein calprotectin enhances Salmonella growth in the inflamed gut

Neutrophils are innate immune cells that counter pathogens by many mechanisms, including release of antimicrobial proteins such as calprotectin to inhibit bacterial growth. Calprotectin sequesters essential micronutrient metals such as zinc, thereby limiting their availability to microbes, a process termed nutritional immunity. We find that while calprotectin is induced by neutrophils during infection with the gut pathogen Salmonella Typhimurium, calprotectin-mediated metal sequestration does not inhibit S. Typhimurium proliferation. Remarkably, S. Typhimurium overcomes calprotectin-mediated zinc chelation by expressing a high affinity zinc transporter (ZnuABC). A S. Typhimurium znuA mutant impaired for growth in the inflamed gut was rescued in the absence of calprotectin. ZnuABC was also required to promote the growth of S. Typhimurium over that of competing commensal bacteria. Thus, our findings indicate that Salmonella thrives in the inflamed gut by overcoming the zinc sequestration of calprotectin and highlight the importance of zinc acquisition in bacterial intestinal colonization.

Wild-type coxsackievirus infection dramatically alters the abundance, heterogeneity, and immunostimulatory capacity of conventional dendritic cells in vivo

In vitro studies have shown that enteroviruses employ strategies that may impair the ability of DCs to trigger T cell immunity, but it is unclear how these viruses affect DCs in vivo. Here, we evaluate the effects of wild-type (wt) coxsackievirus B3 on DCs in vitro and in a murine model in vivo. Although CVB3 does not productively infect the vast majority of DCs, virus infection profoundly reduces splenic conventional DC numbers and diminishes their capacity to prime naïve CD8(+) T cells in vitro. In contrast to recombinant CVB3, highly pathogenic wt virus infection significantly diminishes the host's capacity to mount T cell responses, which is temporally associated with the loss of CD8α(+) DCs. Our findings demonstrate that enterovirus infection substantially alters the number, heterogeneity, and stimulatory capacity of DCs in vivo, and these dramatic immunomodulatory effects may weaken the host's capacity to mount antiviral T cell responses.

CXCR2 signaling and host defense following coronavirus-induced encephalomyelitis

Inoculation of the neurotropic JHM strain of mouse hepatitis virus (JHMV) into the central nervous system (CNS) of susceptible strains of mice results in wide-spread replication within glial cells accompanied by infiltration of virus-specific T lymphocytes that control virus through cytokine secretion and cytolytic activity. Virus persists within white matter tracts of surviving mice resulting in demyelination that is amplified by inflammatory T cells and macrophages. In response to infection, numerous cytokines/chemokines are secreted by resident cells of the CNS and inflammatory leukocytes that participate in both host defense and disease. Among these are the ELR-positive chemokines that are able to signal through CXC chemokine receptors including CXCR2. Early following JHMV infection, ELR-positive chemokines contribute to host defense by attracting CXCR2-expressing cells including polymorphonuclear cells to the CNS that aid in host defense through increasing the permeability the blood-brain-barrier (BBB). During chronic disease, CXCR2 signaling on oligodendroglia protects these cells from apoptosis and restricts the severity of demyelination. This review covers aspects related to host defense and disease in response to JHMV infection and highlights the different roles of CXCR2 signaling in these processes.

The pathogenesis of murine coronavirus infection of the central nervous system

Mouse hepatitis virus (MHV) is a positive-strand RNA virus that causes an acute encephalomyelitis that later resolves into a chronic fulminating demyelinating disease. Cytokine production, chemokine secretion, and immune cell infiltration into the central nervous system are critical to control viral replication during acute infection. Despite potent antiviral T-lymphocyte activity, sterile immunity is not achieved, and MHV chronically persists within oligodendrocytes. Continued infiltration and activation of the immune system, a result of the lingering viral antigen and RNA within oligodendrocytes, lead directly to the development of an immune-mediated demyelination that bears remarkable similarities, both clinically and histologically, to the human demyelinating disease multiple sclerosis. MHV offers a unique model system for studying host defense during acute viral infection and immune-mediated demyelination during chronic infection.

CXCR2 signaling protects oligodendrocytes and restricts demyelination in a mouse model of viral-induced demyelination

BACKGROUND

The functional role of ELR-positive CXC chemokines during viral-induced demyelination was assessed. Inoculation of the neuroattenuated JHM strain of mouse hepatitis virus (JHMV) into the CNS of susceptible mice results in an acute encephalomyelitis that evolves into a chronic demyelinating disease, modeling white matter pathology observed in the human demyelinating disease Multiple Sclerosis.

METHODOLOGY/PRINCIPAL FINDINGS

JHMV infection induced the rapid and sustained expression of transcripts specific for the ELR+ chemokine ligands CXCL1 and CXCL2, as well as their binding receptor CXCR2, which was enriched within the spinal cord during chronic infection. Inhibiting CXCR2 signaling with neutralizing antiserum significantly (p<0.03) delayed clinical recovery. Moreover, CXCR2 neutralization was associated with an increase in the severity of demyelination that was independent of viral recrudescence or modulation of neuroinflammation. Rather, blocking CXCR2 was associated with increased numbers of apoptotic cells primarily within white matter tracts, suggesting that oligodendrocytes were affected. JHMV infection of enriched oligodendrocyte progenitor cell (OPC) cultures revealed that apoptosis was associated with elevated expression of cleaved caspase 3 and muted Bcl-2 expression. Inclusion of CXCL1 within JHMV infected cultures restricted caspase 3 cleavage and increased Bcl-2 expression that was associated with a significant (p<0.001) decrease in apoptosis. CXCR2 deficient oligodendrocytes were refractory to CXCL1 mediated protection from JHMV-induced apoptosis, readily activating caspase 3 and down regulating Bcl-2.

CONCLUSION/SIGNIFICANCE

These findings highlight a previously unappreciated role for CXCR2 signaling in protecting oligodendrocyte lineage cells from apoptosis during inflammatory demyelination initiated by viral infection of the CNS.

A protective role for ELR+ chemokines during acute viral encephalomyelitis

The functional role of ELR-positive CXC chemokines in host defense during acute viral-induced encephalomyelitis was determined. Inoculation of the neurotropic JHM strain of mouse hepatitis virus (JHMV) into the central nervous system (CNS) of mice resulted in the rapid mobilization of PMNs expressing the chemokine receptor CXCR2 into the blood. Migration of PMNs to the CNS coincided with increased expression of transcripts specific for the CXCR2 ELR-positive chemokine ligands CXCL1, CXCL2, and CXCL5 within the brain. Treatment of JHMV-infected mice with anti-CXCR2 blocking antibody reduced PMN trafficking into the CNS by >95%, dampened MMP-9 activity, and abrogated blood-brain-barrier (BBB) breakdown. Correspondingly, CXCR2 neutralization resulted in diminished infiltration of virus-specific T cells, an inability to control viral replication within the brain, and 100% mortality. Blocking CXCR2 signaling did not impair the generation of virus-specific T cells, indicating that CXCR2 is not required to tailor anti-JHMV T cell responses. Evaluation of mice in which CXCR2 is genetically silenced (CXCR2−/− mice) confirmed that PMNs neither expressed CXCR2 nor migrated in response to ligands CXCL1, CXCL2, or CXCL5 in an in vitro chemotaxis assay. Moreover, JHMV infection of CXCR2−/− mice resulted in an approximate 60% reduction of PMN migration into the CNS, yet these mice survived infection and controlled viral replication within the brain. Treatment of JHMV-infected CXCR2−/− mice with anti-CXCR2 antibody did not modulate PMN migration nor alter viral clearance or mortality, indicating the existence of compensatory mechanisms that facilitate sufficient migration of PMNs into the CNS in the absence of CXCR2. Collectively, these findings highlight a previously unappreciated role for ELR-positive chemokines in enhancing host defense during acute viral infections of the CNS.

Consequences of viral infection of the central nervous system (CNS) can range from encephalitis and paralytic poliomyelitis to relatively benign infections with limited clinical outcomes. The localized expression of proinflammatory chemokines within the CNS in response to viral infection has been shown to be important in host defense by attracting antigen-specific lymphocytes from the microvasculature into the parenchyma that control and eventually eliminate the replicating pathogen. However, the relationship between chemokine expression and recruitment of myeloid cells, e.g. neutrophils, to the CNS following infection with a neurotropic virus is not well characterized. Emerging evidence has indicated that the mobilization of neutrophils into the blood and recruitment to the CNS following microbial infection or injury contributes to permeabilization of the blood-brain-barrier that subsequently allows entry of inflammatory leukocytes. Therefore, we have defined the chemokines involved in promoting the directional migration of neutrophils to the CNS in response to viral infection. Using the neurotropic JHM strain of mouse hepatitis virus (JHMV) as a model of acute viral encephalomyelitis, we demonstrate a previously unappreciated role for members of the ELR-positive CXC chemokine family in host defense by attracting PMNs bearing the receptor CXCR2 to the CNS in response to viral infection.

The Biology of Persistent Infection: Inflammation and Demyelination following Murine Coronavirus Infection of the Central Nervous System

Multiple Sclerosis (MS) is an immune-mediated demyelinating disease of humans. Although causes of MS are enigmatic, underlying elements contributing to disease development include both genetic and environmental factors. Recent epidemiological evidence has pointed to viral infection as a trigger to initiating white matter damage in humans. Mouse hepatitis virus (MHV) is a positive strand RNA virus that, following intracranial infection of susceptible mice, induces an acute encephalomyelitis that later resolves into a chronic fulminating demyelinating disease. Immune cell infiltration into the central nervous system is critical both to quell viral replication and instigate demyelination. Recent efforts by our laboratory and others have focused upon strategies capable of enhancing remyelination in response to viral-induced demyelination, both by dampening chronic inflammation and by surgical engraftment of remyelination - competent neural precursor cells.

Differential roles for CXCR3 in CD4+ and CD8+ T cell trafficking following viral infection of the CNS

Lymphocyte infiltration into the central nervous system (CNS) following viral infection represents an important component of host defense and is required for control of viral replication. However, the mechanisms governing inflammation in response to viral infection of the CNS are not well understood. Following intracranial (i.c.) infection of susceptible mice with mouse hepatitis virus (MHV), mice develop an acute encephalomyelitis followed by a chronic demyelinating disease. The CXC chemokine ligand 10 (CXCL10) is expressed following MHV infection and signals T cells to migrate into the CNS. The functional contribution of the CXCL10 receptor CXCR3 in host defense and disease in response to MHV infection was evaluated. The majority of CD4+ and CD8+ T cells infiltrating the CNS following MHV infection express CXCR3. Administration of anti-CXCR3 antibody reduced CD4+ T cell infiltration (p<or=0.05), while CD8+ T cell trafficking was not affected. Anti-CXCR3 treatment during chronic disease correlated with improved motor skills and reduced demyelination. The selective effect of anti-CXCR3 treatment on CD4+ T cells was not the result of either reduced proliferation or modulation in chemokine receptor gene expression. Therefore, CXCR3 signaling has a non-redundant role in T cell subset trafficking in response to viral infection.

Anesthetic management of patients receiving calculus therapy with a third-generation extracorporeal lithotripsy machine

We reviewed the anesthetic requirements for satisfactory use of a third-generation electromagnetic-source design for extracorporeal shockwave lithotripsy (SWL). Medical records were reviewed for a period of 9 months on all patients receiving anesthesia care for SWL with and without other urologic procedures. The Modulith SL20 was used on 56 ASA Class I-III patients having 87 SWL treatments. Demographic and anesthetic variables were recorded. Complications documented included dysrhythmias, nausea necessitating treatment, and conversion from sedation to regional or general anesthesia. The majority of procedures (83%) were performed on an outpatient basis. Patients were classified as ASA physical status I (27%), II (63%), or III (10%). Monitored anesthesia care with intravenous sedation was utilized in 93% of cases. Of these cases, 78 involved a combination of intravenous propofol, fentanyl, and midazolam; the remaining 3 involved propofol, alfentanil, and/or midazolam. The mean treatment duration was 36 minutes. Patients were discharged within 1 hour after procedure completion in 77 cases (89%). Nausea necessitating treatment was rare (3%). The mean dose of propofol administered with SWL as the only procedure was 272 +/- 112 mg. When SWL was combined with other urologic procedures, the mean dose of propofol was 334 +/- 121 mg. Continuous intravenous propofol infusion provides excellent procedural conditions for SWL on the Modulith SL120, a third-generation lithotripter.

The anesthetic management of a patient with chromosome 10qter deletion syndrome

Terminal deletions of chromosome 10q are uncommon. The resulting syndrome includes cardiac and facial anomalies, urogenital abnormalities, limb defects, and mental retardation. Most affected infants require surgical correction of these anomalies. Presented are features inherent in the syndrome that will aid the anesthesiologist in the perioperative management of such patients.

An assessment of the duration of cephapirin-induced coagulation abnormalities as measured by thromboelastography

Cephalosporin antibiotics are used prophylactically in cardiothoracic surgery to prevent postoperative infection. In 30 patients undergoing primary elective coronary artery bypass grafting, the whole blood coagulation system was prospectively evaluated before, and 10 and 30 minutes after administration of 1 g of cephapirin (Cefadyl, Bristol Laboratory, Evansville, IN). All patients had normal preoperative coagulation studies and had not received anticoagulant or antiplatelet therapy within 7 days of surgery. At 10 minutes after cephapirin administration, 23 of 30 patients had a significant change in all phases of whole blood coagulation as monitored by thromboelastography (TEG). Thirty minutes after cephapirin administration there was no statistical difference compared with the baseline TEG. It is concluded that cephapirin can cause a significant but transient change in the viscoelastic properties of blood. Coagulation parameters of the TEG should be measured prior to cephapirin administration to prevent errors in establishing baseline values prior to cardiopulmonary bypass.

Effect of partial neuromuscular blockade on intraoperative electromyography in patients undergoing resection of acoustic neuromas

Intraoperative electromyographic monitoring of the facial nerve during acoustic neuroma excision provides early detection of nerve injury and improved outcome. To determine whether a useful level of peripheral neuromuscular blockade could be achieved without compromise of facial electromyographic monitoring, we studied 10 patients undergoing resection of acoustic neuroma. Facial nerve monitoring was accomplished by placement of wire electrodes in the orbicularis oris, orbicularis occuli, and mentalis muscles. Peripheral neuromuscular blockade was assessed by recording unprocessed hypothenar compound muscle action potentials (CMAPs). After induction of anesthesia, an infusion of atracurium (1.0 micrograms.kg-1.min-1) accompanied by a bolus dose of 50 micrograms/kg was administered. The infusion was then increased in increments of 0.5 micrograms.kg-1.min-1 until a 50% reduction in hypothenar single-twitch CMAP was obtained. Facial nerve function was continuously monitored by comparison of facial CMAPs produced by stimulation of the nerve proximal and distal to the tumor bed. The mean (+/- SD) infusion rate of atracurium was 2.55 +/- 0.75 micrograms.kg-1.min-1. Decrements in facial nerve CMAPs were detected in 6 of 10 patients, and all demonstrated moderate to severe facial nerve dysfunction. In no patient was an unexpected deficit present postoperatively. Moderate degrees of peripheral neuromuscular blockade can be achieved without compromising facial nerve electromyographic monitoring.

The modified Fontan procedure: physiology and anesthetic implications

The modified Fontan operation has gained wide acceptance as a functional corrective procedure for patients with CHD with single ventricle physiology. Long-term survival and palliation of symptoms are excellent with most patients able to lead normal lives. The absence of a pulmonary contractile ventricle means that the single ventricle is responsible for perfusion of both the pulmonary and systemic circulations. Elevated systemic venous pressure is required to overcome PVR and this state of systemic venous hypertension has a significant impact on the anesthetic and postoperative care of these patients.

Method of intraoperative monitoring of neuromuscular function and residual blockade in the recovery room

We evaluated the method used intraoperatively to assess the degree of neuromuscular blockade prior to pharmacologic reversal to determine its role in preventing residual blockade in the postanesthesia care unit (PACU). We studied 38 patients who received a nondepolarizing muscle relaxant during general anesthesia for carotid endarterectomy or thoracotomy. The anesthesiologist assessed the degree of neuromuscular blockade intraoperatively prior to pharmacologic reversal either by the standard method of visually counting the number of evoked thumb twitches elicited by supramaximal train-of-four stimulation of the ulnar nerve (i.e., thumb train-of-four count), or by an alternative method such as 1) visually counting the number of evoked orbicularis oculi muscle twitches elicited by supramaximal train-of-four stimulation of the facial nerve, or 2) observing the patient for clinical evidence of partial recovery (e.g., swallowing or attempts to breathe). Residual blockade in the PACU was defined as 1) a train-of-four ratio less than 0.70 (measured by a mechanomyograph), or 2) the inability of the patient to perform clinical tests of neuromuscular function (e.g., a sustained head lift for 5 seconds) and evidence of neuromuscular weakness that was resolved following administration of edrophonium. Five of the 22 patients (23%) in whom one of the alternative methods was used had residual blockade in the PACU; none of the 16 patients with a thumb train-of-four count of 3 or 4 before pharmacologic reversal of NMB had residual blockade in the PACU (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of desmopressin acetate in patients undergoing coronary artery bypass surgery. A controlled clinical trial with thromboelastographic risk stratification

The role of desmopressin acetate in attenuating blood loss and reducing homologous blood component therapy after cardiopulmonary bypass is unclear. The purpose of this investigation was to identify a subgroup of patients that may benefit from desmopressin acetate therapy. One hundred fifteen patients completed a prospective randomized double-blind, placebo-controlled trial designed to evaluate the effect of desmopressin acetate (0.3 microgram.kg-1) on mediastinal chest tube drainage after elective coronary artery bypass grafting surgery in patients with normal and abnormal platelet-fibrinogen function as diagnosed by the maximal amplitude (MA) on thromboelastographic (TEG) evaluation. The 115 patients evaluated were divided into two groups based on the MA of the post-cardiopulmonary bypass TEG tracing. Group 1 (TEG:MA greater than 50 mm) consisted of 86 patients, of whom 44 received desmopressin and 42 received placebo. Twenty-nine patients had abnormal platelet function (TEG:MA less than 50 mm) and were designated as group 2. In group 2, 13 received desmopressin and 16 placebo. During the first 24 h after cardiopulmonary bypass, the placebo-treated patients in group 2 had significantly greater mediastinal chest tube drainage when compared to placebo patients in group 1 (1,352.6 +/- 773.1 ml vs. 865.3 +/- 384.4 ml, P = 0.002). In addition to increases in blood loss, group 2 placebo patients also were administered an increased number of blood products (P less than 0.05). The desmopressin-treated patients in group 2 neither experienced increased mediastinal chest tube drainage nor received increased amounts of homologous blood products when compared to those in group 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Narcotic-induced histamine release: a comparison of morphine, oxymorphone, and fentanyl infusions

This study, using an improved histamine assay, repeated previous studies that demonstrated large doses of morphine for induction of anesthesia in patients undergoing coronary artery bypass grafting were associated with histamine release. Thirty randomized patients received infusions of either morphine, 1 mg/kg, oxymorphone, 0.2 mg/kg, or fentanyl, 50 micrograms/kg, over a 10-minute period for induction of anesthesia prior to surgery. There were no significant changes in plasma histamine levels in individual patients or among drug groups. The discrepancy between the present histamine results and those previously reported using similar protocols is due, in part, to variations in plasma histamine measurements that can occur using the less reproducible, older assays for histamine. During routine inductions, large doses of morphine, oxymorphone, or fentanyl administered by infusion do not appear to stimulate release of clinically significant plasma levels of histamine.

Effects of referral bias on surgical outcomes: a population-based study of surgical patients 90 years of age or older

During the 11-year period 1975 through 1985, 1,063 surgical procedures were performed on 795 Mayo Clinic patients 90 years of age or older. Preoperative conditions, surgical setting, and perioperative morbidity and mortality were analyzed in a comparison of the local residents of Olmsted County, Minnesota (N = 224), with patients from outside the county but within 250 miles (N = 456) or referrals from a distance of 250 miles or further (N = 115). In comparison with non-Olmsted County patients, Olmsted County patients were generally older, had more preoperative chronic diseases, and underwent more emergency operations. Patients who had traveled 250 miles or more to the Mayo Clinic were more likely to be men and referred for cancer-related surgical procedures. The risks of major morbidity and mortality within 48 hours postoperatively were increased in patients with more preoperative chronic diseases and those undergoing emergency procedures, characteristics most common in Olmsted County patients. Because of differences in these factors between groups, perioperative risks averaged over our entire patient series underestimated risks that would be expected from a population-based cohort such as Olmsted County residents. In general, data from tertiary medical centers probably do not accurately reflect overall practice or outcomes in community settings.

Right ventricular outflow construction for complex congenital cardiac malformations without cardiopulmonary bypass: management and outcome of 44 patients

A review of surgical and anesthetic techniques used in 44 consecutive patients to establish continuity between the right ventricle and pulmonary circulation, without extracorporeal circulation, as a first-stage repair in a variety of selected complex congenital cardiac lesions with right ventricular outflow obstruction, is presented. The overall operative mortality rate was 9% (four deaths), but no deaths occurred in the last 24 patients. Eleven patients (27.5%) have subsequently undergone complete repair and one patient (2.5%) underwent a Fontan repair. The advantages, anesthetic concerns, complications, and outcome are discussed.

A comparison of washed red blood cells versus packed red blood cells (AS-1) for cardiopulmonary bypass prime and their effects on blood glucose concentration in children

The effects on blood glucose concentrations of packed red blood cells (AS-1) (group I) versus washed red blood cells (group II) for cardiopulmonary bypass prime were compared in 20 infants weighing less than 10 kg undergoing cardiac surgical procedures. All patients were anesthetized with N2O/O2/isoflurane/fentanyl and received lactated Ringer's solution prior to bypass. Blood glucose concentrations prior to bypass were 85 +/- 15 mg/dl (mean +/- SD) in group I and 81 +/- 14 mg/dl in group II. Blood glucose concentrations were 210 +/- 21 mg/dl versus 78 +/- 14 mg/dl (P less than 0.001) 10 min after initiation of bypass, 241 +/- 48 mg/dl versus 107 +/- 28 mg/dl (P less than 0.001) prior to separation from bypass, and 214 +/- 52 mg/dl versus 97 +/- 19 mg/dl (P less than 0.001) after protamine administration in group I and group II, respectively. The use of washed red blood cells for cardiopulmonary bypass priming solution in infants significantly attenuates the increase in blood glucose concentration otherwise observed during cardiopulmonary bypass.

Evaluation of a forced-air system for warming hypothermic postoperative patients

Thirty adult surgical patients admitted to the recovery room with an oral temperature less than or equal to 35.0 degrees C were randomized into two groups. Group 1 patients were covered with cotton blankets warmed to 37.0 degrees C, and group 2 patients were treated with a forced-air warming system. Mean oral temperature on admission to the recovery room was the same in both groups (34.3 degrees C). Oral temperature and the presence or absence of shivering were recorded at 15-min intervals. After application of the selected warming method, patients in group 2 were warmer at all time intervals. Mean temperatures in the forced-air heating group and in group 1 were, respectively, 34.8 degrees C and 34.3 degrees C (P less than 0.05) at 15 min; 35.0 degrees C and 34.2 degrees C (P less than 0.01) at 30 min; 35.2 degrees C and 34.5 degrees C (P less than 0.05) at 45 min; 35.8 degrees C and 34.7 degrees C (P less than 0.001) at 60 min; 36.0 degrees C and 35.0 degrees C (P less than 0.01) at 75 min; and 36.0 degrees C and 35.0 degrees C (P less than 0.01) at 90 min. The incidence of shivering was significantly greater in group 1 at 15 and 45 min. In addition, time spent in the recovery room was significantly greater in group 1 than in group 2, 156.0 min versus 99.7 min (P less than 0.003).

Outcomes of surgery in patients 90 years of age and older

During the 11-year period 1975 through 1985, seven hundred ninety-five patients 90 years of age and older underwent operative procedures at the Mayo Clinic, Rochester, Minn. Overall serious morbidity within 48 hours after surgery was 9.4%, and the mortality was 1.6%. The 30-day, 1-year, and 5-year mortality rates were 8.4%, 31.4%, and 78.8%, respectively. Short-term morbidity and both short- and long-term mortality were highly associated with the American Society of Anesthesiologists physical status classification of the patient. Emergency procedures carried a significantly higher risk for morbidity and mortality within the 48-hour period and, to a lesser extent, for long-term mortality. Overall, poorer patient survival was associated with higher American Society of Anesthesiologists class; male sex; preoperative renal, liver, and central nervous system impairment; and surgery on the mouth, nose, or pharynx. When compared with age-, sex-, and calendar year--matched peers from the general population, there was a modest decrease in patient survival at 1 year that reversed by 2 years, with observed survival at 5 years comparable to the rate expected.

Doxacurium chloride for neuromuscular blockade before tracheal intubation and surgery during nitrous oxide-oxygen-narcotic-enflurane anesthesia

The neuromuscular effects of doxacurium (BW A938U) were studied in 36 patients, divided into four groups of 9 patients each, given doxacurium either 50 micrograms/kg (2 x ED95) 5 or 4 minutes or 80 micrograms/kg (3 x ED95) 4 or 3 minutes before tracheal intubation. Adequate neuromuscular relaxation permitted successful intubation at 5 minutes for doxacurium 50 micrograms/kg and at 4 minutes for 80 micrograms/kg. Time to 90% blockade was 5.4 +/- 1.5 minutes for doxacurium 50 micrograms/kg and 3.5 +/- 1.2 minutes for 80 micrograms/kg. Time to 25% spontaneous recovery was 84.7 +/- 54.3 minutes for doxacurium 50 micrograms/kg and 164.4 +/- 85.2 minutes for 80 micrograms/kg. Either neostigmine 45 micrograms/kg, neostigmine 60 micrograms/kg, or edrophonium 1000 micrograms/kg was given for reversal when T1 had spontaneously recovered to 25% of baseline level, T1 being the first response to repetitive train-of-four (TOF) stimuli (2 Hz for 2 seconds at 10-second intervals) expressed as percent of baseline level. The T4:T1 ratio is the amplitude of the fourth twitch relative to the first twitch in a TOF stimulus expressed as a ratio. T1 rapidly achieved 90% of baseline in 5-10 minutes after reversal of neuromuscular blockade. In contrast, the T4:T1 ratio lagged, recovering to a mean of 0.6 at 20 minutes when T1 was over 90% of baseline. Recovery patterns were not statistically significantly different (unpaired t-test) among the three reversal regimens. Therefore, the reversal data were pooled. No clinically significant hemodynamic effects occurred in any group.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaesthesia for patients over 90 years of age. Outcomes after regional and general anaesthetic techniques for two common surgical procedures

Peri-operative morbidity and mortality and long term outcome of patients over 90 years of age who underwent either total hip arthroplasty or transurethral prostate resection were studied retrospectively. The outcomes of patients who received regional or general anaesthesia were compared. One hundred and forty-one patients underwent total hip arthroplasty and 44 patients underwent transurethral prostate resection during the study period (1975-1985). Overall in-hospital mortality was 4.9% Mortality at 30 days was 5.3% in patients who underwent hip arthroplasty during regional anaesthesia, compared with 6.8% in those who received general anaesthesia. Long term survival was similar for these two groups and was longer than projected for age and gender-matched general population cohorts. The 30-day mortality rate was 3.2% for patients who underwent prostatic resection under regional anaesthesia; no deaths occurred in the general anaesthesia group. This difference was not statistically significant. Long term survival was similar for patients in both groups and was better than predicted. Anaesthetic technique did not influence short term morbidity and mortality or long term outcome for these procedures.

Combined H1 and H2 receptor blockade attenuates the cardiovascular effects of high dose atracurium in rabbits

Large doses of atracurium (1.5 mg/kg) (six times the ED95) have been reported to provide adequate conditions for rapid sequence endotracheal intubation within 60 seconds in humans. However, this dose can result in significant histamine release and systemic hypotension. We therefore studied the efficacy of histamine receptor blockade in attenuating this response. Four groups of five rabbits were pretreated as follows: Group I--control, Group II--H1 blockade (1 mg/kg diphenhydramine), Group III--H2 blockade (cimetidine 4 mg/kg), and Group IV--H1 and H2 blockade (diphenhydramine 1 mg/kg and cimetidine 4 mg/kg). All rabbits were anesthetized and then 1.8 mg/kg (six times the rabbit ED95) atracurium was administered. Group I rabbits experienced a decrease in MAP of 12.2 mmHg after one minute, a change that was significantly greater than Group IV in which MAP decreased by 0.8 mmHg (p less than 0.001). H1 or H2 receptor blockade alone was associated with intermediate changes in MAP not significantly different from control. We conclude that combined H1 and H2 receptor blockade attenuates the cardiovascular effects associated with large doses of atracurium in the rabbit and that this combination of antagonist drugs might have similar effectiveness in humans.

Combined H1 and H2 receptor blockade attenuates the cardiovascular effects of high-dose atracurium for rapid sequence endotracheal intubation

Large doses of atracurium (1.5 mg/kg) (six times the ED95) can result in significant histamine release, resulting in systemic hypotension. The efficacy of histamine receptor blockade in attenuating atracurium induced hypotension was therefore studied. Four groups of seven patients each were studied: group I, control; group II, H1 blockade (1 mg/kg diphenhydramine); group III, H2 blockade (cimetidine 4 mg/kg); and group IV, H1 and H2 blockade (diphenhydramine 1 mg/kg and cimetidine 4 mg/kg). All patients were anesthetized with an intravenous narcotic-nitrous oxide technique and then given 1.5 mg/kg atracurium. In group I, mean arterial pressure (MAP) decreased 30 mm Hg after 2 minutes and remained 25 mm Hg below baseline at 3 minutes, a change significantly greater than that in group IV, in which MAP decreased 8 and 7 mm Hg, respectively. H1 receptor blockade was associated with no significant attenuation of changes in MAP. H2 receptor blockade alone was associated with significant decreases in MAP, possibly secondary to enhanced release of histamine via an antagonist effect on recently described H3 receptors. Plasma histamine levels increased significantly 2 minutes after atracurium administration and correlated with hemodynamic changes. It is concluded that combined H1 and H2 receptor blockade attenuates cardiovascular effects associated with large doses of atracurium in humans. Histamine-releasing agents may be contraindicated in patients subject to chronic H2 receptor blockade.

Surgical procedures among those greater than or equal to 90 years of age. A population-based study in Olmsted County, Minnesota, 1975-1985

Persons greater than or equal to 90 years of age represent a rapidly growing subset of the population, but little data exist on their utilization of the health care system. Population-based data capabilities of the Rochester/Olmsted County Epidemiology Project were used to study the performance of surgery among persons greater than or equal to 90 years of age for the 11-year period, 1975-1985. During this time, 224 residents of Olmsted County, Minnesota underwent 301 separate operations. The annual operation rate increased over the course of the study (trend test, p less than 0.001), reaching a plateau of 89.0 per 1000 person-years. This suggests a potential for nearly 91,000 operations annually in this age group based on 1987 U.S. Census estimates. Ninety-two per cent were discharged from the hospital alive, and 5-year survival was consistent with that expected (23% vs. 17%). Increased longevity of the general population, combined with increased performance of surgery in this rapidly growing segment of the population, may have significant implications for health care planning.

The effects of intraoperative blood salvage and induced hypotension on transfusion requirements during spinal surgical procedures

Spinal surgical procedures, such as placement of Harrington rods for correction of scoliosis, are associated with considerable perioperative blood loss and, hence, with the risks associated with homologous blood transfusions. To test the hypothesis that intraoperative autologous blood transfusions could decrease the amount of homologous blood needed in such operations, we conducted a two-part study: (1) a retrospective review of 142 patients in whom blood salvage was not used and (2) a prospective review of 28 patients who received autologous transfusions. Intraoperative autologous transfusion reduced the amount of homologous blood required by more than 50% (5.1 versus 2.0 units; P less than 0.001). The total amount of homologous blood required during the hospital stay was also significantly reduced by intraoperative autologous transfusion (6.0 versus 3.4 units; P less than 0.001). Induced hypotension in 81 of the 142 patients who did not receive autologous transfusions did not decrease the homologous blood transfusion requirements from those needed by the normotensive patients. We conclude that intraoperative autologous transfusion significantly reduces the need for homologous blood products in patients who undergo spinal surgical procedures. Induced hypotension, which did not affect transfusion requirements in our study, should be further evaluated in a blinded, prospective study.

Monitoring and analysis of oxygenation and ventilation during rigid bronchoscopic neodymium-YAG laser resection of airway tumors

Neodymium-YAG (yttrium-aluminum-garnet) laser resection of obstructing and inoperable tumors of the large airways is used as palliative therapy to improve the quality of survival in patients by alleviating airway obstruction. Rapid changes in oxygenation and ventilation can occur during these procedures. In a study of 14 patients, transcutaneous oxygen (PtcO2) and carbon dioxide (PtcCO2) monitors responded slowly to these changes and frequently provided misleading values. Pulse oximetry (SNO2) accurately reflected arterial oxygen saturation but did not indicate severe desaturation until arterial oxygen tension approached dangerously low values. Thus, we did not find PtcO2 or PtcCO2 monitoring to be clinically useful during neodymium-YAG laser resection of airway tumors through a rigid bronchoscope. SNO2 was clinically useful and accurate; however, a large decrement in oxygenation may occur before changes in oxygen saturation ensue and are detected.