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Techniques of extracorporeal cytokine removal: a systematic review of the literature on animal experimental studies

Atan R, Crosbie D, Bellomo R

Int J Artif Organs, 2013 Mar;36(3):149-58.
PMID: 23446761 DOI: 10.5301/ijao.5000128

BACKGROUND AND AIMS: Extracorporeal cytokine removal may be desirable. We sought to assess extracorporeal blood purification (EBP) techniques for cytokine removal in experimental animal studies. 
METHODS: We conducted a targeted, systematic search and identified 17 articles. We analyzed cytokine clearance, sieving coefficient (SC), ultrafiltrate (UF) concentration, and percentage removal. As this review concerns technical appraisal of EBP techniques, we made no attempts to appraise the methodology of the studies included. Results are in descriptive terms only. 
RESULTS: Applying predicted clearance for 80 kg human, high volume hemofiltration (HVHF) techniques and plasmafiltration (PF) showed the highest rates of cytokine removal. High cutoff (HCO)/HF and PF techniques showed modest ability to clear cytokines using low to medium flows. Standard hemofiltration had little efficacy. At higher flows, HCO/HF achieved clearances between 30 and 70 ml/min for IL-6 and IL-10. There was essentially no removal of tumor necrosis factor (TNF)-alpha outside of PF. 
CONCLUSIONS: Experimental animal studies indicate that HVHF (especially with HCO filters) and plasmafiltration have the potential to achieve appreciable IL-6 and IL-10 clearances. However, only PF can remove TNF-alpha reliably.
Selection of suitable pedicle screw for degenerated cortical and cancellous bone of human lumbar spine: A finite element study

Jain P, Sing Ngie DC, Lim SF, Lim BH

Int J Artif Organs, 2020 Oct 13.
PMID: 33045876 DOI: 10.1177/0391398820964483

Pedicular arthrodesis is the traditional procedure in terms of increase in the biomechanical stability with higher fixation rate. The current work aims to identify the effect of three spinal pedicle screws considering cortical and cancellous degeneracy condition. Lumbar section L2-L3 is utilized and various load and moment conditions were applied to depict the various biomechanical parameters for selection of suitable screw. Three dimensional model is considered in finite element analysis to identify the various responses of pedicle screw at bone screw juncture. Computed tomography (CT) images of a healthy male were considered to generate the finite element vertebral model. Generated intact model was further utilized to develop the other implanted models of degenerated cortical and cancellous bone models. The three fused instrumented models with different cortical and cancellous degeneracy conditions were analyzed in finite element analysis. The results were obtained as stress pattern at bone screw boundary and intervertebral disc stress. FE simulated results represents significant changes in the von Mises stress due to various load and moment conditions on degenerated bones during different body movement conditions. Results have shown that among all pedicle screws, the 6.0 mm diameter screw reflects very less stress values at the juncture. Multiple results on biomechanical aspects obtained during the FE study can be considered to design a new stabilization device and may be helpful to plan surgery of critical sections.
Effects of conform, non-conform, and hybrid conformity toward stress distribution at the glenoid implant and cement: A finite element study

Abdul Wahab AH, Mohamad Azmi NA, Abdul Kadir MR, Md Saad AP

Int J Artif Organs, 2022 Feb;45(2):200-206.
PMID: 33645338 DOI: 10.1177/0391398821999391

Glenoid conformity is one of the important aspects that could contribute to implant stability. However, the optimal conformity is still being debated among the researchers. Therefore, this study aims to analyze the stress distribution of the implant and cement in three types of conformity (conform, non-conform, and hybrid) in three load conditions (central, anterior, and posterior). Glenoid implant and cement were reconstructed using Solidwork software and a 3D model of scapula bone was done using MIMICS software. Constant load, 750 N, was applied at the central, anterior, and posterior region of the glenoid implant which represents average load for daily living activities for elder people, including, walking with a stick and standing up from a chair. The results showed that, during center load, an implant with dual conformity (hybrid) showed the best (Max Stress-3.93 MPa) and well-distributed stress as compared to other conformity (Non-conform-7.21 MPa, Conform-9.38 MPa). While, during eccentric load (anterior and posterior), high stress was located at the anterior and posterior region with respect to the load applied. Cement stress for non-conform and hybrid implant recorded less than 5 MPa, which indicates it had a very low risk to have cement microcracks, whilst, conform implant was exposed to microcrack of the cement. In conclusion, hybrid conformity showed a promising result that could compromise between conform and non-conform implant. However, further enhancement is required for hybrid implants when dealing with eccentric load (anterior and posterior).
High cut-off hemofiltration versus standard hemofiltration: effect on plasma cytokines

Atan R, Peck L, Visvanathan K, Skinner N, Eastwood G, Bellomo R, et al.

Int J Artif Organs, 2016 Nov 11;39(9):479-486.
PMID: 27834446 DOI: 10.5301/ijao.5000527

PURPOSE: To study the effects of continuous veno-venous hemofiltration (CVVH) with high cut-off filters (CVVH-HCO) on plasma cytokine levels, sieving coefficient and clearance compared to CVVH using standard filters (CVVH-Std) in a nested cohort within a double-blind randomized controlled trial in severe acute kidney injury (AKI) patients.
METHODS: We measured plasma and post-filter levels of IL-6, TNF-alpha, IL-8, IL-1 beta, RANTES, IL-10, IFN-gamma and IFN-alpha in both study groups. We also measured cytokine levels in the ultrafiltrate and calculated sieving coefficients and clearances.
RESULTS: By 72 hours of treatment, IL-6 had decreased during both treatments (p = 0.009 and 0.005 respectively). In contrast, IL-10 had decreased with CVVH-Std (p = 0.03) but not CVVH-HCO (p = 0.135). None of the other cytokines showed changes over time. There were also no significant between group differences in plasma levels for each cytokine over the 72-hour treatment period. For all cytokines combined, however, the median sieving coefficient was higher for CVVH-HCO (0.31 vs. 0.16; p = 0.042) as was the mass removal rate by ultrafiltration (p = 0.027). While overall combined cytokine levels had fallen to 62.2% of baseline at 72 hours for CVVH-HCO (p<0.0001) and to 75.9% of baseline with CVVH-Std (p = 0.008) there were no between group differences.
CONCLUSIONS: CVVH-HCO achieved greater combined sieving coefficient and mass removal rate by ultrafiltration for a group of key cytokines than CVVH-Std. However, this effect did not differentially lower their plasma level over the first 72 hours. Our study does not support the use of CVVH-HCO to lower cytokines in critically ill patients with AKI.