Early warning: End-tidal carbon dioxide is associated with central venous oxygenation under continuous cardiorespiratory monitoring in a porcine model of hemorrhagic shock and resuscitation

BACKGROUND

End-tidal carbon dioxide (ETCO2) has previously shown promise as a predictor of shock severity and mortality in trauma. ETCO2 monitoring is non-invasive, real-time, and readily available in prehospital settings, but the temporal relationship of ETCO2 to systemic oxygen transport has not been thoroughly investigated in the context of hemorrhagic shock.

METHODS

A validated porcine model of hemorrhagic shock and resuscitation was used in male Yorkshire swine (N ​= ​7). Both ETCO2 and central venous oxygenation (SCVO2) were monitored and recorded continuously in addition to other traditional hemodynamic variables.

RESULTS

Linear regression analysis showed that ETCO2 was associated with ScvO2 both throughout the experiment (β ​= ​1.783, 95% confidence interval (CI) [1.552-2.014], p ​< ​0.001) and during the period of most rapid hemorrhage (β ​= ​4.896, 95% CI [2.416-7.377], p ​< ​0.001) when there was a marked decrease in ETCO2.

CONCLUSIONS

ETCO2 and ScvO2 were closely associated during rapid hemorrhage and continued to be temporally associated throughout shock and resuscitation.

Effects of chronic Helicobacter pylori strain PMSS1 infection on whole brain and gastric iron homeostasis in male INS-GAS mice

Iron deficiency, the most common micronutrient deficiency in humans, is associated with long-term deficits in cognition and memory if left untreated. Infection with the gastric pathogen Helicobacter pylori has been linked to iron deficiency anemia (IDA). The H. pylori virulence factor cytotoxin-associated gene A (cagA) is proposed to be especially pertinent in iron deficiency. Male INS-GAS/FVB mice were infected with the CagA⁺ strain pre-murine Sydney strain 1 (PMSS1) for 12-13 or 27-29 weeks to investigate the role of chronic H. pylori infection in iron deficiency and neurological sequelae. Mice at both timepoints demonstrated significantly elevated gastric histopathology scores and inflammatory cytokines compared to sham-dosed controls. However, only mice at 27-29 weeks post infection had changes in hematological parameters, with significantly decreased erythrocyte count, hematocrit, serum hemoglobin, and increased serum total iron binding capacity. Gastric transcription of iron-regulatory genes Hamp and Bmp4 were significantly downregulated at both timepoints. In the brain, iron-dependent myelingergic and synaptic markers were significantly downregulated at 27-29 weeks. These results indicated that long-term infection of the CagA ⁺ PMSS1 strain of H. pylori in this study caused anemia, altered gastric iron homeostasis, and neurological changes similar to those reported in other rodent H. pylori CagA^- strain infection models.

The Epidemiology of Invasive, Multipleantibiotic-resistant Klebsiella pneumoniae Infection in a Breeding Colony of Immunocompromised NSG Mice

Klebsiella pneumoniae (Kp) is a gram-negative opportunistic pathogen that causes severe pneumonia, pyelonephritis, and sepsis in immunocompromised hosts. During a 4-mo interval, several NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) breeders and pups in our facilities were diagnosed with Kp infections. An initial 6 adult and 1 juvenile NSG mice were submitted for necropsy and histologic examination because of acute onset of diarrhea and death. The evaluation revealed typhlocolitis in 2 of the mice and tritrichomoniasis in all 7. Escherichia coli positive for polyketide synthase (pks+) and Kp were isolated from the intestines. Given a history of sepsis due to pks+ E. coli in NSG mice in our facilities and determination of its antimicrobial susceptibility, trimethoprim-sulfamethoxazole (TMP-SMX) was administered to the colony in the drinking water for 4 wk. After this intervention, an additional 21 mice became ill or died; 11 of these mice had suppurative pneumonia, meningoencephalitis, hepatitis, metritis, pyelonephritis, or sepsis. Kp was cultured from pulmonary abscesses or blood of 10 of the mice. Whole-genome sequencing (WGS) indicated that the Kp isolates contained genes associated with phenotypes found in pore-forming Kp isolates cultured from humans with ulcerative colitis and primary sclerosing cholangitis. None of the Kp isolates exhibited a hyperviscous phenotype, but 13 of 14 were resistant to TMP-SMX. Antimicrobial susceptibility testing indicated sensitivity of the Kp to enrofloxacin, which was administered in the drinking water. Antibiotic sensitivity profiles were confirmed by WGS of the Kp strains; key virulence and resistance genes to quaternary ammonia compounds were also identified. Enrofloxacin treatment resulted in a marked reduction in mortality, and the study using the NSG mice was completed successfully. Our findings implicate intestinal translocation of Kp as the cause of pneumonia and systemic infections in NSG mice and highlight the importance of identification of enteric microbial pathogens and targeted antibiotic selection when treating bacterial infections in immunocompromised mice.