Jamming of prosthetic heart valves by suture trapping: experimental findings

The vulnerability of the Medtronic-Hall, Bj?rk-Shiley Monostrut, Duromedics, and St. Jude Medical valves to occluder immobilization by sutures was determined under static and pulsatile flow conditions. Variables were cardiac output, cross-sectional diameter of suture, type of suture (braided versus monofilament) and position of the offending suture along the circumference of the valve ring. Under static conditions, pressures, ranging from 40 to 340 mmHg and 10 to 170 mmHg, were required to decompress obstructed Medtronic-Hall and Bj?rk-Shiley Monostrut valves, respectively. As a result of different design characteristics and different occluder/orifice clearances the Medtronic-Hall valve showed its maximum opening pressure in case of interference with sutures at the axis of symmetry in both minor and major orifices, whereas for the Bj?rk-Shiley Monostrut valve this was reached in the minor orifice. Under pulsatile flow conditions, in case of interference with Prolene 2-0 suture, the Duromedics valve showed irregularly delayed opening and an opening pressure difference of 50 mmHg at a cardiac output of 8 L/min, whereas leaflet motion and pressure difference in the St. Jude Medical valve were undisturbed under similar conditions. The necessary pressure difference for opening the Medtronic Hall valve reached 44mmHg at a cardiac output of 8 L/min. High and low risk of extrinsic leaflet obstruction in the Duromedics and St. Jude Medical valves, respectively, is related to the design of the hinge mechanisms and the wedge angle of their leaflets (2 degrees versus 25 degrees). Precautionary principles in implantation of prosthetic heart valves are stressed to prevent the potentially lethal complication of occluder immobilization.(ABSTRACT TRUNCATED AT 250 WORDS)     

A randomised controlled trial of the effectiveness of soft silicone multi‐layered foam dressings in the prevention of sacral and heel pressure ulcers in trauma and critically ill patients: the border trial

The prevention of hospital acquired pressure ulcers in critically ill patients remains a significant clinical challenge. The aim of this trial was to investigate the effectiveness of multi‐layered soft silicone foam dressings in preventing intensive care unit (ICU) pressure ulcers when applied in the emergency department to 440 trauma and critically ill patients. Intervention group patients (n = 219) had Mepilex^® Border Sacrum and Mepilex^® Heel dressings applied in the emergency department and maintained throughout their ICU stay. Results revealed that there were significantly fewer patients with pressure ulcers in the intervention group compared to the control group (5 versus 20, P = 0·001). This represented a 10% difference in incidence between the groups (3·1% versus 13·1%) and a number needed to treat of ten patients to prevent one pressure ulcer. Overall there were fewer sacral (2 versus 8, P = 0·05) and heel pressure ulcers (5 versus 19, P = 0·002) and pressure injuries overall (7 versus 27, P = 0·002) in interventions than in controls. The time to injury survival analysis indicated that intervention group patients had a hazard ratio of 0·19 (P = 0·002) compared to control group patients. We conclude that multi‐layered soft silicone foam dressings are effective in preventing pressure ulcers in critically ill patients when applied in the emergency department prior to ICU transfer.     

Influence of parainfluenza-1 respiratory tract viral infection on endothelin receptor-effector systems in mouse and rat tracheal smooth muscle.

1. In this study we have compared the effects of parainfluenza-1 respiratory tract viral infection on the density and function of ETA and ETB receptors in rat and mouse tracheal airway smooth muscle. 2. The bronchoconstrictor effect of inhaled methacholine was significantly enhanced in virus-infected rats, at both 4 and 12 days post-inoculation. That is, the concentration of methacholine causing an increase in resistance of 100% (PC100 methacholine) was significantly lower in virus-infected animals at both 4 and 12 days post-inoculation (n = 6-8; P < 0.05). 3. Total specific binding of [125I]-endothelin-1 and the relative proportions of ETA and ETB binding sites for [125I]-endothelin-1 were assessed in tracheal airway smooth muscle in parainfluenza-1-infected rats and mice at days 2, 4 and 12 post-inoculation using the ligands BQ-123 (1 microM; ETA receptor-selective) and sarafotoxin S6c (100 nM; ETB receptor-selective). Total specific binding in mice was significantly reduced at day 2 post-inoculation (n = 5; P < 0.05) but not at days 4 and 12 post-inoculation (n = 5). In control mice, the proportions of ETA and ETB binding sites were 53%:47% at day 2 and 43%:57% at day 4 and these were significantly altered by parainfluenza-1 infection such that, the ratios were 81%:19% at day 2 and 89%:11% at day 4 (P < 0.05). By day 12 post-inoculation, the proportion of ETA and ETB binding sites in tracheal smooth muscle from mice infected with parainfluenza-1 was not significantly different from control. In rat tracheal airway smooth muscle, neither total specific binding nor the ETA and ETB binding site ratio (64%:36%) were significantly altered in virus-inoculated rats at days 2, 4 or 12 post-inoculation (n = 5). 4. Parainfluenza-1 infection in mice had no effect on the sensitivity or maximal contractile effect of endothelin-1 in tracheal smooth muscle at days 2, 4 or 12 post-inoculation (n = 4). In contrast, contraction in response to the ETB receptor-selective agonist sarafotoxin S6c was attenuated by 39% at day 2 and by 93% at day 4 post-inoculation (P < 0.05). However, by day 12 post-inoculation, contractions to sarafotoxin S6c were not significantly different between control and virus-infected mice. In parainfluenza-1-infected rats, there were small but significant reductions in the sensitivity to carbachol, endothelin-1 and sarafotoxin S6c whilst the maximal responses to the highest concentrations of these agonists were not significantly altered by virus infection (n = 8). 5. BQ-123 (3 microM) had no significant effect on cumulative concentration-effect curves to endothelin-1 in tracheal preparations from control mice (n = 4) or parainfluenza-1-infected rats (n = 8). In contrast, in tissues taken from virus-infected mice at day 4 post-inoculation, BQ-123 caused a marked 9.6 fold rightward shift in the concentration-effect curve to endothelin-1 (n = 4). 6. In summary, we have demonstrated that parainfluenza-1 infection in mice transiently reduced the density of tracheal airway smooth muscle ETB receptors and this was reflected in reduced responsiveness to the ETB receptor-selective agonist sarafotoxin S6c. In contrast, whilst parainfluenza-1 infection in rats was associated with the pathological features and bronchial hyperresponsiveness common to respiratory tract viral infection, there was no selective down-regulation of ETB receptor expression or functional activity. The reasons for these species differences are not clear, but may relate to differences in the airway inflammatory response to parainfluenza-1 virus.