Influence of intraoperative fluid replacement on ampicillin serum levels and surgical site infections.

BACKGROUND: Surgical site infections (SSI) occur despite antimicrobial prophylaxis and increase postoperative morbidity and mortality. This could be caused by an intraoperative decrease in antibiotic serum concentrations such as ampicillin after major abdominal surgery due to blood loss and fluid therapy, which possibly promotes SSI. This hypothesis was tested in the present study. METHODS: This pilot study was performed as a prospective observational trial between March 2018 and May 2019. Ampicillin/sulbactam was administered intravenously during anesthesia induction. Fluid replacement was guided based on hemodynamic variables, including analysis of pulse pressure variation. The primary outcome was ampicillin serum level (ASL), measured after administration and hourly within 4 hours. The incidence of SSI at hospital discharge was the secondary outcome. Linear mixed and logistic regression models were used for statistical analyses. RESULTS: After screening of 133 adult patients, 129 were enrolled, and 102 completed the study protocol. No correlation was found between the volume of intraoperative fluids and ASL, nor was any association found between ASL and SSI. Based on 5 SSI cases, SSI were associated with higher intraoperative fluid volume. ASL was sufficient to provide intraoperative coverage for all potential bacterial strains. CONCLUSION: Intraoperative fluid replacement had no effect on ASL up to 4 hours after ampicillin/sulbactam administration. SSI were within an acceptable range, indicating adequate antimicrobial prophylaxis, so intraoperative control of ASL does not seem necessary. In conclusion, contrary to our initial hypothesis, ASL is not influenced by volume turnover or blood loss during major surgery and therefore does not affect SSI.

Analgesic treatment limits surrogate parameters for early stress and pain response after experimental subarachnoid hemorrhage.

BACKGROUND: In animal research, authorities require a classification of anticipated pain levels and a perioperative analgesia protocol prior to approval of the experiments. However, data on this topic is rare and so is the reported use of analgesics. We determined surrogate parameters of pain and general well-being after subarachnoid hemorrhage (SAH), as well as the potential for improvement by different systemic analgesia paradigms. Brain injury was induced by filament perforation to mimic SAH. Sham-operated mice were included as surgical control groups with either neck or no-neck preparation. Mice with controlled cortical impact (CCI) injury were included as a control group with traumatic brain injury (TBI), but without neck preparation. Mice were randomized to buprenorphine, carprofen, meloxicam, or vehicle treatment. 24 h after SAH, CCI or sham surgery, pain and stress levels were assessed with a visual assessment score and the amount of food intake was recorded. RESULTS: Neck preparation, which is required to expose the surgical field for SAH induction, already increased pain/stress levels and sham surgeries for both CCI and SAH reduced food intake. Pain/stress levels were higher and food intake was lower after SAH compared with CCI. Pain/stress levels after CCI without analgesic treatment were similar to levels after SAH sham surgery. Pain treatment with buprenorphine was effective to reduce pain after SAH, whereas lower pain/stress intensity levels after CCI were not improved. CONCLUSION: This study emphasizes the importance of pain and stress assessment after surgeries and the efficacy of buprenorphine to improve pain and comfort levels after experimental SAH.

High membrane protein oxidation in the human cerebral cortex.

Oxidative stress is thought to be one of the main mediators of neuronal damage in human neurodegenerative disease. Still, the dissection of causal relationships has turned out to be remarkably difficult. Here, we have analyzed global protein oxidation in terms of carbonylation of membrane proteins and cytoplasmic proteins in three different mammalian species: aged human cortex and cerebellum from patients with or without Alzheimer's disease, mouse cortex and cerebellum from young and old animals, and adult rat hippocampus and cortex subjected or not subjected to cerebral ischemia. Most tissues showed relatively similar levels of protein oxidation. However, human cortex was affected by severe membrane protein oxidation, while exhibiting lower than average cytoplasmic protein oxidation. In contrast, ex vivo autooxidation of murine cortical tissue primarily induced aqueous protein oxidation, while in vivo biological aging or cerebral ischemia had no major effect on brain protein oxidation. The unusually high levels of membrane protein oxidation in the human cortex were also not predicted by lipid peroxidation, as the levels of isoprostane immunoreactivity in human samples were considerably lower than in rodent tissues. Our results indicate that the aged human cortex is under steady pressure from specific and potentially detrimental membrane protein oxidation. The pronounced difference between humans, mice and rats regarding the primary site of cortical oxidation might have contributed to the unresolved difficulties in translating into therapies the wealth of data describing successful antioxidant neuroprotection in rodents.

The antioxidative, non-psychoactive tricyclic phenothiazine reduces brain damage after experimental traumatic brain injury in mice.

Oxidative stress due to free radical formation is an important mechanism of secondary brain damage following traumatic brain injury (TBI). Phenothiazine has been found to be a strong antioxidant in eukaryotic cells in vitro and in invertebrates in vivo. The present study was designed to determine the neuroprotective potency of unsubstituted phenothiazine in a paradigm of acute brain injury. Thirty minutes after pneumatic, controlled cortical impact (CCI) injury, C57BI6 mice were randomly assigned to "low dose" (3 mg/kg, LD) or "high dose" (30 mg/kg, HD) s.c. phenothiazine or vehicle treatment. Brain lesion, neurofunctional impairment, body weight, and markers of cerebral inflammation were determined 24h after the insult. Phenothiazine treatment dose-dependently reduced brain lesion volume (LD: -19.8%; HD: -26.1%) and posttraumatic body weight loss. There were no significant differences in the neurological function score and in markers of cerebral inflammation (Iba-1 positive cells, TNFα expression), whereas iNOS expression was significantly lower compared to vehicle-treated animals. Phenothiazine appears to modify in a post-treatment protocol certain aspects of secondary brain damage in vivo at unusually low concentrations, in particular the cortical contusion volume after TBI. The potential role of the reduced iNOS expression is unclear at present.

Anesthesia for euthanasia influences mRNA expression in healthy mice and after traumatic brain injury.

Tissue sampling for gene expression analysis is usually performed under general anesthesia. Anesthetics are known to modulate hemodynamics, receptor-mediated signaling cascades, and outcome parameters. The present study determined the influence of anesthetic paradigms typically used for euthanization and tissue sampling on cerebral mRNA expression in mice. Naïve mice and animals with acute traumatic brain injury induced by controlled cortical impact (CCI) were randomized to the following euthanasia protocols (n=10-11/group): no anesthesia (NA), 1 min of 4 vol% isoflurane in room air (ISO), 3 min of a combination of 5 mg/kg midazolam, 0.05 mg/kg fentanyl, and 0.5 mg/kg medetomidine intraperitoneally (COMB), or 3 min of 360 mg/kg chloral hydrate intraperitoneally (CH). mRNA expression of actin-1-related gene (Act1), FBJ murine osteosarcoma viral oncogene homolog B (FosB), tumor necrosis factor alpha (TNFα), heat shock protein beta-1 (HspB1), interleukin (IL)-6, tight junction protein 1 (ZO-1), IL-1ß, cyclophilin A, micro RNA 497 (miR497), and small cajal body-specific RNA 17 were determined by real-time polymerase chain reaction (PCR) in hippocampus samples. In naïve animals, Act1 expression was downregulated in the CH group compared with NA. FosB expression was downregulated in COMB and CH groups compared with NA. CCI reduced Act1 and FosB expression, whereas HspB1 and TNFα expression increased. After CCI, HspB1 expression was significantly higher in ISO, COMB, and CH groups, and TNFα expression was elevated in ISO and COMB groups. MiR497, IL-6, and IL-1ß were upregulated after CCI but not affected by anesthetics. Effects were independent of absolute mRNA copy numbers. The data demonstrate that a few minutes of anesthesia before tissue sampling are sufficient to induce immediate mRNA changes, which seem to predominate in the early-regulated gene cluster. Anesthesia-related effects on gene expression might explain limited reproduciblity of real-time PCR data between studies or research groups and should therefore be considered for quantitative PCR data.

Propofol impairs neurogenesis and neurologic recovery and increases mortality rate in adult rats after traumatic brain injury.

OBJECTIVE: Limited data are available on the influence of sedation for critical care therapy with the widely used anesthetic propofol on recovery from acute traumatic brain injury. To establish the influence of propofol on endogenous neurogenesis and functional recovery after traumatic brain injury, rats were sedated with propofol either during or 2 hours after experimental traumatic brain injury. DESIGN: Randomized controlled animal study. SETTING: University research laboratory. SUBJECTS: One hundred sixteen male Sprague Dawley rats. INTERVENTIONS: Mechanical brain lesion by controlled cortical impact. MEASUREMENTS AND MAIN RESULTS: This study investigated the dose-dependent influence of propofol (36 or 72 mg/kg/hr) either during controlled cortical impact induction or in a delayed application protocol 2 hours after experimental traumatic brain injury. Infusion of propofol resulted in 1) aggravation of neurologic dysfunction, 2) increased 28-day mortality rate, and 3) impaired posttraumatic neurogenesis (5-bromo-2-deoxyuridine + NeuN-positive cells). Application of propofol during trauma induction afforded a significant stronger effect in the high-dose group compared with low-dose propofol. In the posttrauma protocol, animals were sedated with sevoflurane during the controlled cortical impact injury, and propofol was given after an awake phase. In these animals, propofol increased mortality rate and impaired neurologic function and neurogenesis compared with animals without delayed propofol anesthesia. CONCLUSIONS: The results show that propofol may prevent or limit reparative processes in the early-phase postinjury. The results therefore indicate that anesthetics may be potentially harmful not only in very young mammalians but also in adult animals following acute cerebral injuries. The results provide first evidence for an altered sensitivity for anesthesia-related negative effects on neurogenesis, functional outcome, and survival in adult rats with brain lesions.