Influence of the Compliance of the Pump Housing and Cannulas of a Paracorporeal Pneumatic Ventricular Assist Device on Transient Pressure Characteristics

Abstract: The dependence of transient pressure characteristics of a ventricular assist device (VAD) on the compliance of its housing and cannulas was investigated in a mock circulation. The peak rate of change of pressure ( dP/dt _max) values was greater in the cannulas than other compartments and was associated with valve closure-induced pressure oscillations. When cannula compliance was increased from 0.0057 to 0.0129 cm³/mm Hg, these values decreased by ˜20%, and outflow cannula pressure oscillation frequency decreased from 17.5 Hz by 35%. This trend was also apparent in the inflow. A VAD housing compliance increase from 0.0162 to 0.0483 cm³/mm Hg caused a dP/dt _max decrease of 30% in both the blood chamber and the outflow cannula. The effect of this change on the inflow was weaker implying that housing absorbs the energy associated with outflow deceleration more effectively than the inflow. These findings suggest that increasing VAD housing and cannulas compliance can improve hydrodynamic performance.     

Injection of substance P (SP) N-terminal fragment SP(1-7) into the ventral tegmental area modulates the levels of nucleus accumbens dopamine and dihydroxyphenylacetic acid in male rats during morphine withdrawal

The biologically active substance P (SP) N-terminal metabolite SP_1–7 has been reported to modulate several neural processes such as learning, locomotor activity and reaction to opioid withdrawal. Although all these processes are believed to be associated with dopaminergic transmission no evidence of an interaction between SP_1–7 and dopamine in the case of morphine withdrawal has so far been reported. Therefore, in this work we applied in vivo microdialysis to investigate the effect of SP_1–7 injection into the ventral tegmental area on dopamine release in nucleus accumbens of male rats during naloxone precipitated morphine withdrawal. The result showed that the heptapeptide enhances dopamine release and also elevates the level of the dopamine metabolite dihydroxyphenylacetic acid in this brain area. It was suggested that the observed action of the SP fragment on the dopamine system represents the underlying mechanism for a previously observed ability of SP_1–7 to counteract the aversion response to morphine withdrawal.     

Histamine-induced vasodilations mediated by H1- and H2-receptors in isolated rat common carotid arteries

Summary Using the cannula inserting method, the vasodilatory effects of histamine were analysed employing selective histamine H₁- and H₂-receptor agonists and antagonists in isolated, perfused rat common carotid arterial preparations which were preconstricted by a continuous infusion of phenylephrine with propranolol. Histamine, 2-pyridylethylamine (2-PEA) (a selective H₁-agonist) and dimaprit (a selective H₂-agonist) produced a vasodilation in a dose-related manner. The order of potency was histamine > dimaprit > 2-PEA. Histamine-induced dilations were significantly inhibited by either diphenhydramine (a selective H₁-antagonist) or cimetidine (a selective H₂-antagonist). 2-PEA-induced dilations were significantly inhibited by diphenhydramine but not by cimetidine. Dimaprit-induced dilations were significantly blocked by cimetidine but not by diphenhydramine. ACh-, histamine-, 2-PEA- and dimaprit-induced dilations were significantly suppressed by removal of the endothelium. From these results, it is concluded that (1) isolated rat common carotid arteries have both H₁-and H₂-receptors, (2) there are few vasoconstrictory H₁-receptors, (3) both H₁- and H₂-receptors mediate only vasodilation but not vasoconstriction, and (4) EDRF from the endothelium might participate in histamine-induced vasodilation via not only H₁- but also H₂-receptors.     

预置D-J管分期碎石治疗输尿管嵌顿结石的临床研究

目的比较一期输尿管镜碎石与预置D-J管后二期输尿管镜碎石治疗嵌顿性输尿管结石的临床效果。方法将96例嵌顿性输尿管结石患者按手术方法的不同分为两组,一期碎石组48例,二期碎石组58例。比较两组一次性清石率、手术时间、术后住院时间、并发症发生率等指标。结果两组比较,二期碎石组一次性清石率及手术时间比较并发症发生率、术后住院时间、住院费用等指标均优于一期碎石组,比较差异均有统计学差异(P<0.05)。结论输尿管硬镜联合输尿管软镜钬激光碎石治疗输尿管嵌顿性结石有良好效果,预先置管可进一步提高临床疗效。     

Increased risk of cardiovascular perforation during ECMO with a bicaval,wire-reinforced cannula

Purpose

Cardiac or major vascular perforation is a rare but serious risk of ECMO. We sought to determine if perforation rates are related to cannula design.

Methods

We utilized three methods to evaluate perforation on ECMO. 1. The ELSO registry was queried to establish the historical rate of hemorrhagic pericardial tamponade. 2. ELSO centers were surveyed regarding cannula related perforation events and brands of cannulas used over a four year time period (January 2008–March 2012). 3. The FDA’s MAUDE database was reviewed looking for adverse events related to ECMO cannulas.

Results

The historical rate of hemorrhagic pericardial tamponade in the ELSO registry was 0.53% (~ 1985–2010, ELSO registry). In the survey there were eleven reports of cannula-related perforation, 0.74% (11/1482 p-value = 0.29) at 7 different ELSO centers with 23 ELSO centers responding (17% response rate). The incidence of perforation was much higher for the wire-reinforced bicaval design 3.6% (10/279) as compared to catheters designed for the atrial position, 0.1% (1/1203, p-value < 0.0001). Review of the FDA’s MAUDE database revealed 19 adverse events related to the bicaval cannula design, 16 of which were hemorrhagic pericardial effusions or tamponade.

Conclusion

These findings suggest a relatively high rate of cardiac perforation associated with the dual lumen bicaval cannula. This may be related to inherent differences in cannula design or the IVC positioning required by the design.     

Comparison of vasoconstrictor actions of norepinephrine and potassium chloride before and after damage of endothelium by saponin

Summary Using isolated and perfused mesenteric arterial preparations of dogs, vasoconstrictor responses to intraluminal norepinephrine and potassium chloride were investigated in the presence and absence of the endothelium. Intraluminal administration of saponin readily removed the endothelium. Saponin (1–3 mg) caused an increase in perfusion pressure, and then approximately 20 min later perfusion pressure became stable at a somewhat higher level than that of the control. A larger dose of saponin (10 mg) caused a tremendous but temporary increase of perfusion pressure. KCl-induced vasoconstriction was significantly enhanced by pretreatment with 0.3, 1, and 3 mg saponin, but norepinephrine-induced constriction was not modified significantly. Moreover, it was demonstrated that diltiazem, a potent Ca antagonist, inhibited the KCl-induced vasoconstriction more readily in the absence than in the presence of the endothelium.     

Norepinephrine and serotonin: Specificity of release with rewarding electrical stimulation of the brain

Using a push-pull cannula method the amygdala of rats was perfused to examine the release of labeled norepinephrine (NE) and labeled serotonin (5-HT) during electrical stimulation of the brain (ESB) determined by prior behavioral testing to be rewarding or non-rewarding. Simple sensory stimulation was used during perfusion to examine further the degree of specificity of release of these amines. Highly rewarding ESB, but not the sensory stimulation, was accompanied by release of both NE and 5-HT. Varying current intensity had significant effects on the amount of these amines released. Furthermore, non-rewarding ESB was accompanied by inhibition of release of NE and 5-HT and a control substance, urea, was not significantly released during rewarding ESB. The results were discussed as implicating both noradrenergic and serotonergic mechanisms in the mediation of reinforcement.     

Fast three-dimensional numerical hemolysis approximation

The in vivo implantation of a mechanical device contributes to hemodynamic disturbances, which are responsible for damage to the membranes of red blood cells that in turn can lead to their rupture (hemolysis). It is important to ascertain at the design stage of such mechanical devices that they are innocuous to blood. Because there is no in vivo hemolysis index, we concentrated our efforts on the in vitro hemolysis index of the American Society for Testing and Material (ASTM) standard. We present in this work a framework for minimizing medical device-induced hemolysis by the development of a numerical method for predicting hemolysis similar to that used in in vitro experiments. The method is based on a novel interpretation of the Giersiepen-Wurzinger blood damage correlation that replaces the computation of blood damage along the streamline by a volume integration of a damage function over the computational domain. We assess the behavior and accuracy of this methodology with 3D examples.     

Mechanisms of release of ATP from vascular purinergic nerves

1. The vasoconstrictor response to periarterial nerve electrical stimulation (PNS) and neurotransmission by ATP are discussed and illustrated, using canine isolated and perfused splenic arterial preparations. 2. The conditions for appearance of dominant purinergic constrictor response to PNS are discussed. 3. Modulation of the purinergic vasoconstrictor responses to PNS by several kinds of presynaptic receptor agonists and antagonists is reviewed. 4. Influences of purinergic responses to PNS by guanethidine, reserpine, tetrodotoxin (TTX) or omega-conotoxin GVIA (omegaCTX) are also reviewed. 5. Effects of imipramine and removal of the endothelium are discussed. 6. Evidence is presented for selective inhibition of purinergic responses to PNS by an adequate cold storage of the vessel. 7. The roles of ATP released by PNS in isolated canine splenic arteries are proposed.