The effect of a low-dose naloxone infusion on the incidence of respiratory depression after intrathecal morphine administration for major open hepatobiliary surgery: a randomised controlled trial.

Intrathecal morphine is an analgesic option for major hepatopancreaticobiliary procedures but is associated with a risk of respiratory depression. We hypothesised that a postoperative low-dose naloxone infusion would reduce the incidence of respiratory depression without an increase in pain scores. Patients scheduled for major open hepatopancreaticobiliary surgery and who were receiving 10 µg.kg-1 intrathecal morphine were eligible for inclusion. Patients were allocated randomly to receive a postoperative infusion of naloxone 5 µg.kg-1 .h-1 (naloxone group) or saline at an identical infusion rate (control group) until the morning after surgery. Clinicians, nursing staff and patients were blinded to group allocation. The primary outcome measure was the incidence of respiratory depression (respiratory rate < 10 breaths.min-1 and/or oxygen saturation < 90%). Secondary outcome measures included: arterial partial pressure of carbon dioxide; pain score; requirement for supplemental analgesic; and incidence of nausea and vomiting, pruritus and sedation. In total, data from 95 patients (48 in the naloxone group and 47 in the control group) were analysed. The incidence of respiratory depression was lower in the naloxone group compared with the control group (10/48 vs. 21/47 patients, respectively; p = 0.037, relative risk 0.47 (95%CI 0.25-0.87). Maximum pain scores were greater for patients allocated to the naloxone group compared with control (median 5 (95%CI 4-6) vs. 4 (95%CI 2-4), respectively; p < 0.001). A low-dose naloxone infusion decreases the incidence of respiratory depression following intrathecal morphine administration in patients having major hepatopancreaticobiliary surgery at the expense of a small increase in postoperative pain.

Assessment of the reliability and validity of a novel point-of-care fibrinogen (F-Point) device against an industry standard at fibrinogen levels >2 g/L in non-haemorrhage scenarios.

INTRODUCTION: A diagnostic accuracy study assessing the reliability and validity of a novel plasma fibrinogen point-of-care (F-Point) device compared with the von Clauss method of assay. METHODS: Forty-one women presenting for elective caesarean delivery and 43 non-pregnant female patients presenting for elective gynaecological surgery were recruited to assess agreement at normal fibrinogen levels (elective gynaecological cohort) and high fibrinogen levels (elective caesarean section cohort). Validity was assessed by comparing the F-Point results with the gold standard of von Clauss fibrinogen assay performed on the ACL Top 500. Reliability (test-retest) and validity were assessed using the intraclass correlation to control for operator variance (two-way random absolute agreement method), presented as intra class correlation coefficients (ICCs) and 95% confidence interval, and Bland-Altman analysis, presented as mean bias and 95% limits of agreement and coefficient of variation (COV). RESULTS: The results demonstrated a high test-retest reliability demonstrated in the paired F-Point measurements with an intraclass correlation coefficient (ICC) of 0.95, a bias of 0 (-00.69 to 0.69) and a COV of 9%. Similarly, there was acceptable agreement demonstrated between F-Point and von Clauss assay with an ICC of 0.91, a bias of -0.1 (-0.96 to 0.75) and a COV of 11%. CONCLUSIONS: Our novel plasma fibrinogen point-of-care device has been shown to be reliable and valid when testing fibrinogen levels as low as 2 g/L. Future studies investigating the correlation at lower fibrinogen levels, for example during haemorrhage and in patients with coagulopathies, are required.

Extreme leukoreduction of major histocompatibility complex class II positive B cells enhances allogeneic platelet immunity.

In a murine model of platelet alloimmunization, we examined the definitive role that mononuclear cells (MC) have in modulating platelet immunity by using platelets from severe combined immunodeficient (SCID) mice. CB.17 (H-2(d)) SCID or BALB/c (H-2(d)) mouse platelets were transfused weekly into fully allogeneic CBA (H-2(k)) mice and antidonor antibodies measured by flow cytometry. MC levels in BALB/c platelets were 1.1 +/- 0.6/microL and SCID mouse platelets could be prepared to have significantly lower (<0. 05/microL) MC numbers. Transfusions with 10(8) BALB/c platelets (containing approximately 100 MC/transfusion) stimulated IgG antidonor antibodies in 100% of the recipients by the fifth transfusion, whereas 10(8) SCID mouse platelets (containing approximately 5 MC/transfusion) stimulated higher-titered IgG alloantibodies by the second transfusion. When titrations of BALB/c peripheral blood MC were added to the SCID mouse platelets, levels approaching 1 MC/microL reduced SCID platelet immunity to levels similar to BALB/c platelets. Characterization of the alloantibodies showed that the low levels of MC significantly influenced the isotype of the antidonor IgG; the presence of 1 MC/microL was associated with induction of noncomplement fixing IgG1 antidonor antibodies, whereas platelet transfusions, devoid of MC (<0. 05/microL), were responsible for complement-fixing IgG2a production. When magnetically sorted defined subpopulations of MC were added to the SCID platelets, major histocompatability complex (MHC) class II positive populations, particularly B cells, were found to be primarily responsible for the reduced SCID mouse platelet immunity. The presence of low numbers of MC within the platelets was also associated with an age-dependent reduction in platelet immunogenicity; this relationship however, was not observed with SCID mouse platelets devoid of MC. The results suggest that a residual number of MHC class II positive B cells within allogeneic platelets are required for maximally reducing alloimmunization.

Differences in serum cytokine levels in acute and chronic autoimmune thrombocytopenic purpura: relationship to platelet phenotype and antiplatelet T-cell reactivity.

Patients with both acute and chronic autoimmune thrombocytopenic purpura (AITP) have in vitro lymphocyte defects in the form of platelet-stimulated proliferation and cytokine secretion. A blinded study was performed to determine if these defects are related to serum cytokine levels and/or platelet antigen expression. Compared with controls, 53% of children with chronic AITP, but only 9% of those with acute AITP, had increased serum interleukin-2 (IL-2), interferon-gamma, and/or IL-10; however, none of the patients had detectible serum levels of IL-4 or IL-6, cytokine patterns suggesting and early CD4+ Th0 and Th1 cell activation. In children with chronic AITP, the levels of serum IL-2 correlated with in vitro platelet-stimulated IL-2 production. Few (17%) patients with AITP showed platelet activation, as measured by CD62 expression, or abnormal expression levels of platelet membrane glycoprotein (GP) IIbIIIa, but abnormal GPIb levels were observed in one-third of children with AITP. In contrast to normal controls and patients with nonimmune thrombocytopenia, a significant number of children with acute (80%), chronic (71%), or chronic-complex (55%) AITP and GPIb+ peripheral blood cells expressing HLA-DR. HLA-DR was variably coexpressed on distinct smaller and larger-sized GPIb+ cell populations with CD41, CD45, CD14, CD80, and/or glycophorin molecules. GPIb+ cells isolated from spleens of patients with chronic AITP had high expression (49% +/- 30%) of HLA-DR and splenic T cells had a high level of in vitro platelet-stimulated IL-2 secretion compared with controls. Platelet HLA-DR expression correlated inversely with platelet count, but not with therapy, serum cytokines, or in vitro lymphocyte antiplatelet reactivity. The results indicate that platelet HLA-DR expression is a common occurrence in patients with immune thrombocytopenia, whereas a large subpopulation of children with chronic AITP can be identified by increased serum cytokine levels and in vitro platelet-stimulated IL-2 secretion by lymphocytes, suggesting that differences exist in the immune pathogenesis of acute and chronic AITP, particularly at the level of platelet reactive T cells.

Induction of a secondary human anti-HLA alloimmune response in severe combined immunodeficient mice engrafted with human lymphocytes.

BACKGROUND: Experimental manipulation of transfusion-induced alloimmunization is limited in humans by ethical considerations. Conversely, studies of alloimmunization in animal models may not reflect the human immune system closely enough to be of optimal benefit. The development of an in vivo model of human alloimmunization that is amenable to experimental manipulation is thus desirable. STUDY DESIGN AND METHODS: An in vivo model of human alloimmunization was evaluated by using mice with severe combined immunodeficiency (SCID). SCID mice underwent gamma-radiation (200 cGy) and received an intraperitoneal injection of human peripheral blood lymphocytes (PBLs) from donors immunized to HLA antigens by prior pregnancy (reconstitution). These Hu [human]-PBL-SCID mice were then challenged with HLA-mismatched PBLs. Alloantibodies were evaluated by flow cytometry and a standard two-stage microlymphocytotoxicity assay. RESULTS: Hu-PBL-SCID mice (n = 22) that were challenged with PBLs expressing the HLA antigens to which the donors had previously been immunized, made significantly more IgM and IgG alloantibodies than did the unchallenged mice. Responses were measurable by 1 week after reconstitution and challenge. Prior treatment of SCID mice with anti-asialo GM1, which depletes murine natural killer cells and macrophages, further increased the alloantibody response of challenged mice. The human alloantibodies generated were specific to the challenge HLA antigens as assessed by microlymphocytotoxicity assay. CONCLUSION: Hu-PBL-SCID mice are a useful model system in which to study and manipulate the induction of secondary human alloimmune responses against cellular HLA class I antigens. This model will be valuable for testing the in vivo effect of novel immunotherapies on the inhibition of the human alloantibody response.