Thermal Injury Prediction During Cryoplasty Through <Emphasis Type="Italic">In Vitro</Emphasis> Characterization of Smooth Muscle Cell Biophysics and Viability

Restenosis in peripheral arteries is a major health care problem in the United States. Typically, 30–40% of angioplasties result in restenosis and hence alternative treatment techniques are being actively investigated. Cryoplasty, a novel technique involving simultaneous stretching and freezing of the peripheral arteries (e.g., femoral, iliac, popliteal) using a cryogen-filled balloon catheter, has shown the potential to combat restenosis. However, evaluation of the thermal and biophysical mechanisms that affect cellular survival during cryoplasty is lacking. To achieve this, the thermal history in arteries was predicted for different balloon temperatures using a thermal model. Cellular biophysical responses (water transport (WT) and intracellular ice formation (IIF)) were then characterized, using in vitro model systems, based on the thermal model predictions. The thermal and biophysical effects on cell survival were eventually determined. For this study, smooth muscle cells (SMC) isolated from porcine femoral arteries were used in suspensions and attached in vitro systems (monolayer and fibrin gel). Results showed that for different balloon temperatures, the thermal model predicted cooling rates from 2200 to 5 °C/min in the artery. Biophysical parameters (WT & IIF) were higher for SMCs in attached systems as compared to suspensions. The “combined” fit WT parameters for SMCs in suspension (at 5, 10, and 25 °C/min) are L _pg = 0.12 μm/(min atm) and E _Lp = 24.1 kcal/mol. Individual WT parameters for SMCs in attached cell systems at higher cooling rates are approximately an order of magnitude higher compared to suspensions (e.g., at 130 °C/min, WT parameters in monolayer and fibrin TE systems are L _pg = 18.6, 19.4 μm/(min atm) and E _Lp = 112, 127 kcal/mol, respectively). Similarly, IIF parameters assessed at 130 °C/min are higher for SMCs in attached systems than suspensions ( = 1.1, 354, 378 (× 10⁸ (1/m² s)) and κ_o = 1.6, 1.8, 2.1 (× 10⁹ K⁵) for suspensions, monolayer, and fibrin TE, respectively). One possible reason for the differences in IIF kinetics was verified to be the presence of gap junctions, which facilitate cell–cell connections through which ice can propagate. This is reflected by the change in the predicted IIF parameters when a gap junction inhibitor was added and tested in monolayer ( (1/m² s)); κ_o = 2.1 × 10⁹ K⁵). SMC viability was affected by the model system (lower viability in attached systems), the thermal conditions and the biophysics. For e.g., IIF is lethal to cells and SMC viability was verified to be the least in fibrin TE (most % IIF) and the most in suspensions (least % IIF) at all cooling rates. Using the results from the fibrin TE (suggested as the best in vitro system to mimic a restenosis environment), conservative estimates of injury regimes in the artery during cryoplasty is predicted. The results can be used to suggest future optimizations and modifications during cryoplasty and also to design future in vivo studies.

Human immunodeficiency virus-1 infection protects against a Tc1-to-Tc2 shift in CD8(+) T cells

Despite the reports of dysfunction of the lytic abilities of CD8(+) T cells during human immunodeficiency virus-1 (HIV-1) disease progression, the effects of infection on the noncytolytic functions of CD8(+) T cells have not been well characterized to date. We examined the effect of HIV-1 infection on the cytokine and chemokine responses of peripheral blood-derived CD8(+) T cells in an in vitro system. Activation of HIV-1-infected CD8(+) T cells with phytohemagglutinin resulted in a 4- to 8-fold increase in the production of macrophage inflammatory protein (MIP)-1α, MIP-1β, regulated on activation normal T-cell expressed and secreted, and interleukin (IL)-16. Treatment of activated HIV-1-infected CD8(+) T cells with anti-CD3 monoclonal (M) antibody (Ab) and IL-15 induced strong production of interferon-γ (IFN-γ). Treatment of cells with anti-IL-12 MAb and IL-4 to induce a Tc1-to-Tc2 shift resulted in no change in viral production levels or IFN-γ production within the HIV-1-infected CD8(+) T cell population. Initiation of a Tc2-to-Tc1 shift resulted in a 6-fold increase in HIV-1 replication and 2- to 3-fold higher levels of IFN-γ, demonstrating that infection can protect against a Tc1-to-Tc2 shift in CD8(+) T cells.     

Salvage topical therapy for upper tract urothelial carcinoma

Purpose

Topical therapy (TT) for upper tract urothelial carcinoma (UTUC) has been explored as a kidney sparing approach to treat carcinoma in situ (CIS) and as adjuvant for endoscopically treated Ta/T1 tumors. In bladder cancer, data support use of salvage TT for repeat induction. We investigate the outcomes of salvage TT for UTUC in patients ineligible for or refusing nephroureterectomy.

Methods

A single-center retrospective review on patients receiving salvage TT via percutaneous nephrostomy tube or cystoscopically placed ureteral catheters was performed. Primary outcome was response to therapy based on International Bladder Cancer Group criteria.

Results

51 patients with 58 renal units (RUs) received TT. Of these, 17 patients with 18 RUs received the second-line TT, with a median follow-up of 36.5 months (IQR 24.5–67 months). 44% (8/18) received salvage TT for refractory disease and 56% (10/18) as reinduction. 5 RUs with CIS were unresponsive to initial TT and went on to receive salvage TT, of which 20% (1/5) responded. 13 RUs recurred or relapsed following initial TT and received salvage TT for papillary tumors, with 62% (8/13) responding.

Conclusion

Our data provide preliminary clinical rationale for the second-line TT for refractory and recurrent, endoscopically managed papillary UTUC in patients ineligible for or refusing nephroureterectomy. However, refractory upper tract CIS appears to have poor response to salvage TT.

     

A retrospective analysis of loss of reduction in operated supracondylar humerus fractures

Background:

Loss of reduction following closed or open reduction of displaced supracondylar fractures of the humerus in children varies widely and is considered dependent on stability of the fracture pattern, Gartland type, number and configuration of pins for fixation, technical errors, adequacy of initial reduction, and timing of the surgery. This study was aimed to evaluate the factors responsible for failure of reduction in operated pediatric supracondylar fracture humerus.

Materials and Methods:

We retrospectively assessed loss of reduction by evaluating changes in Baumann''s angle, change in lateral rotation percentage, and anterior humeral line in 77 consecutive children who were treated with multiple Kirschner wire fixation and were available for followup. The intraoperative radiographs were compared with those taken immediately after surgery and 3 weeks postoperatively. Multivariate logistic regression analysis was performed by STATA 10.

Results:

Reduction was lost in 18.2% of the patients. Technical errors were significantly higher in those who lost reduction (P = 0.001; Odds Ratio: 57.63). Lateral pins had a significantly higher risk of losing reduction than cross pins (P = 0.029; Odds Ratio: 7.73). Other factors including stability of fracture configuration were not significantly different in the two groups.

Conclusions:

The stability of fracture fixation in supracondylar fractures in children is dependent on a technically good pinning. Cross pinning provides a more stable fixation than lateral entry pins. Fracture pattern and accuracy of reduction were not important factors in determining the stability of fixation.     

Low-dose hydrocortisone in patients with COVID-19 and severe hypoxia (COVID STEROID) trial—Protocol and statistical analysis plan

Introduction

Severe acute respiratory syndrome coronavirus-2 has caused a pandemic of coronavirus disease (COVID-19) with many patients developing hypoxic respiratory failure. Corticosteroids reduce the time on mechanical ventilation, length of stay in the intensive care unit and potentially also mortality in similar patient populations. However, corticosteroids have undesirable effects, including longer time to viral clearance. Clinical equipoise on the use of corticosteroids for COVID-19 exists.

Methods

The COVID STEROID trial is an international, randomised, stratified, blinded clinical trial. We will allocate 1000 adult patients with COVID-19 receiving ≥10 L/min of oxygen or on mechanical ventilation to intravenous hydrocortisone 200 mg daily vs placebo (0.9% saline) for 7 days. The primary outcome is days alive without life support (ie mechanical ventilation, circulatory support, and renal replacement therapy) at day 28. Secondary outcomes are serious adverse reactions at day 14; days alive without life support at day 90; days alive and out of hospital at day 90; all-cause mortality at day 28, day 90, and 1 year; and health-related quality of life at 1 year. We will conduct the statistical analyses according to this protocol, including interim analyses for every 250 patients followed for 28 days. The primary outcome will be compared using the Kryger Jensen and Lange test in the intention to treat population and reported as differences in means and medians with 95% confidence intervals.

Discussion

The COVID STEROID trial will provide important evidence to guide the use of corticosteroids in COVID-19 and severe hypoxia.

     

Slower Onset of Low Shear Stress Leads to Less Neointimal Thickening in Experimental Vein Grafts

Vein grafts respond to low flow and shear stress (τ_w) by generating thicker walls and smaller lumens through the processes of neointimal hyperplasia and remodeling. Clinically, however, vein grafts with obviously low τ_w, such as those distal to high-grade proximal obstructions, are not infrequently found to be widely patent and pliable. One possible explanation for this phenomenon may be that vein grafts remodel more favorably in response to changes in shear that occur gradually over time compared to abruptly. This hypothesis was tested in an experimental animal model in this report. Two separate models of experimental vein graft failure were created, causing either immediate exposure to ultralow τ_w (<1 dyne/cm²) or delayed exposure to ultralow τ_w. Under general anesthesia and using a sterile technique, the right external jugular (EJ) veins of 28 New Zealand white rabbits were surgically exposed and isolated. An end-to-side distal EJ/common carotid artery anastomosis was created, resulting in a widely patent arteriovenous fistula. For the immediate exposure group (n = 5), the EJ was suture-ligated just proximal to the thoracic inlet, distal to a small 10-50 μm venous tributary. This created a reversed vein segment immediately and abruptly exposed to high wall tension (2.0 ± 0.3 × 10⁴ dyne/cm) and ultralow τ_w (0.15 ± 0.08 dyne/cm²). For the delayed exposure group (n = 22), the EJ was ligated over a 0.035 guidewire, leaving a small aperture to sustain some measure of blood flow and τ_w. This predictably resulted in slightly less wall tension (1.4 ± 0.2 × 10⁴ dyne/cm) and higher τ_w (0.68 ± 0.21 dyne/cm²) than the immediate exposure group. During the first week, the small outflow aperture in the delayed exposure grafts thrombosed, eventually exposing them to the same low level of τ_w as the immediate exposure grafts. Thus, the only difference in the two models was that delayed exposure grafts enjoyed a slower decline in τ_w than immediate exposure grafts. Fourteen rabbits in the delayed exposure group were harvested over the first 7 days to define the patency curve of the restricted outflow channel. As expected, the small aperture had thrombosed in all animals by 7 days. The remaining 14 grafts were harvested after 4 weeks, and 13/14 remained patent. Examination of the hemodynamic parameters at the time of death confirmed that wall tension and τ_w had equalized (wall tension 0.9 ± 0.1 vs. 1.1 ± 0.1 × 10⁴ dyne/cm, τ_w 0.45 ± 0.12 vs. 0.30 ± 0.08 dyne/cm²). Histological examination revealed less neointimal hyperplasia in the delayed exposure group compared to the immediate exposure group (wall thickness 266 ± 16 vs. 180 ± 24 μm, p = 0.025) as well as a slightly greater luminal diameter (0.30 ± 0.02 vs. 0.40 ± 0.02 cm, p = 0.038). The results of this experiment suggest that slow exposure to reduced τ_w results in more favorable remodeling (less thickening) than abrupt exposure. This finding may explain the occasional clinical observation of a widely patent vein graft even in the face of proximal arterial obstruction and very low flow; the change in τ_w presumably occurred slowly mitigating the remodeling response. Presented at the Vascular Society 2004 Annual Meeting, Anaheim, CA, June 5, 2004.