Impact of race on infrainguinal angioplasty and stenting.

BACKGROUND: Over the last decade, catheter-based interventions on lower extremity arteries have been used with increasing frequency. However, the effect of racial background on the outcome of lower extremity endovascular interventions for peripheral arterial disease is unknown. The purpose of this study was to determine the effect of patients' race on the durability of angioplasty and stenting performed on the superficial femoral and popliteal arteries. METHODS: The records of all patients undergoing percutaneous intervention on the lower extremity arteries during a 14-year period were reviewed. During a 44-month period (2003-2007), all patients underwent primary stenting as part of a prospective study protocol. Indication for intervention, TransAtlantic InterSociety Consensus II classification, runoff anatomy, site of intervention, and the placement of stents were noted. Results were analyzed by race. Kaplan-Meier life survival curves were plotted and differences between groups tested by log-rank method. Cox proportional hazards regression model was used to perform the multivariate analysis. RESULTS: Between 1994 and 2007, a total of 374 percutaneous interventions were performed on the superficial femoral and popliteal arteries in 280 patients. Of these, 182 procedures were angioplasties and 192 included both angioplasty and stenting. The study group consisted of 60% Caucasians, 23% Hispanics, 12% African Americans, and 5% Asians. No difference in primary patency rates was noted between individuals belonging to different races. However, in those undergoing angioplasty alone, Caucasians had the highest rate of failure, followed by Hispanics, African Americans, and then Asians (p < 0.002). No difference in patency rates between races was seen in patients undergoing angioplasty with stenting. For the entire group, dyslipidemia, TransAtlantic InterSociety Consensus II C and D lesions, and angioplasty without stenting negatively affected primary patency. CONCLUSIONS: Race does not appear to influence the durability of catheter-based procedures performed on the superficial femoral and popliteal arteries. However, in patients who underwent angioplasty alone, it was noted that Caucasians had the highest rates of failure and Asians the lowest. However, this difference was no longer apparent when stents were used.

Endothelin 1 and prostacyclin attenuate increases in hydraulic permeability caused by platelet-activating factor in rats.

We have previously documented that endothelin 1 (ET-1) and prostacyclin (PGI2) decrease basal state hydraulic permeability (Lp). The aim of this study was to investigate the ability of ET-1 and PGI2 to modulate transendothelial fluid flux during situations in which Lp was artificially elevated with platelet-activating factor (PAF). We hypothesized that ET-1 and PGI2 administration before PAF exposure would prevent the increase in Lp secondary to PAF. In addition, in a potentially more clinically relevant situation, we also hypothesized that ET-1 and PGI2 administration after PAF exposure would attenuate the increase in Lp secondary to PAF. Microvascular Lp was measured in rat mesenteric postcapillary venules. Exposure to 10 nM PAF increased Lp 4-fold (P < 0.001). If the administration of 80 pM ET-1 or 10 microM PGI2 was completed before PAF exposure, no PAF-associated increase in Lp was observed (P < 0.001). The administration of ET-1 or PGI2 after PAF exposure attenuated the peak increase in Lp caused by PAF alone by 55% and 57%, respectively (P < 0.001). We conclude that ET-1 and PGI2 administration before PAF exposure prevents PAF-induced elevations in Lp, and in a more clinically relevant situation, ET-1 and PGI2 administered after PAF exposure attenuate the PAF-induced increase in Lp. Endothelin 1 and PGI2 receptors may provide important therapeutic targets for decreasing the microvascular fluid leak-associated morbidity resulting from shock and sepsis.

The effect of hypoxia, reoxygenation, ischemia, and reperfusion on hydraulic permeability in rat mesenteric venules.

Little is known regarding the effects of I/R on hydraulic permeability (Lp). We sought to compare the individual influences of hypoxia, ischemia, reoxygenation, and reperfusion on Lp. We hypothesized that (1) hypoxia increases Lp; (2) reoxygenation further increases Lp; (3) ischemia results in greater increases in Lp compared with hypoxia; (4) reperfusion causes additional increases in Lp compared with hypoxia, ischemia, and reoxygenation; and (5) xanthine oxidase (XO) and white blood cell adherence play important roles in hypoxia, ischemia, and reperfusion. Hydraulic permeability was measured by an in vivo microcannulation technique during hypoxia, reoxygenation, ischemia, and reperfusion in rat mesenteric postcapillary venules. Additional rats were fed a Tungsten-enriched diet to inhibit XO activity, and the studies were repeated. White blood cell adherence was also documented. Hypoxia and ischemia both increased Lp 2-fold from baseline levels (P < 0.001). Reoxygenation did not alter Lp compared with 15 min of hypoxia alone (P > 0.07). Reperfusion after hypoxia increased Lp 6-fold (P < 0.001). Reperfusion after ischemia also increased Lp 6-fold (P < 0.001). Inhibition of XO had no effect on the increase in Lp after both hypoxia and ischemia. However, inhibition of XO attenuated the 6-fold increase in Lp observed during reperfusion after both hypoxia and ischemia by approximately 50% (P < 0.001). White blood cell adherence increased during reperfusion but not hypoxia or ischemia. The complexity of I/R injury makes it a difficult clinical scenario to model for research. We have demonstrated in an in vivo model that hypoxia and ischemia increase Lp similarly, and that reperfusion has a profound deleterious effect on Lp. These changes in Lp seem to be XO and white blood cell dependent.

Ischemia-reperfusion injury in rats affects hydraulic conductivity in two phases that are temporally and mechanistically separate.

Ischemia-reperfusion (IR) injury is a major insult to postcapillary venules. We hypothesized that IR increases postcapillary venular hydraulic conductivity and that IR-mediated changes in hydraulic conductivity result from temporally and mechanistically separate processes. A microcannulation technique was used to determine hydraulic conductivity (Lp) in rat mesenteric postcapillary venules serially throughout ischemia (45 min) and reperfusion (5 h) induced by superior mesenteric artery occlusion and release. Mesenteric IR resulted in a biphasic increase in Lp. White blood cell (WBC) adhesion slowly increased with maximal adhesion corresponding to the second peak (P < 0.005). After IR, tissue was harvested for RT-PCR analysis of ICAM-1, E-selectin, and P-selectin mRNA. Intercellular adhesion molecule-1 (ICAM-1) mRNA in the gut showed the most significant upregulation. Quantitative real-time PCR revealed that ICAM-1 mRNA was upregulated 60-fold in the gut. An ICAM-1 antibody was therefore used to determine the effect of WBC adhesion on Lp during IR. ICAM-1 inhibition attenuated Lp during the first peak and completely blocked the second peak (P < 0.005). When rats were fed a tungsten diet to inhibit xanthine oxidase and then underwent IR, Lp was dramatically attenuated during the first peak and mildly decreased the second peak (P < 0.005). Inhibition of xanthine oxidase by oxypurinol decreased Lp during IR by over 60% (P < 0.002). Tempol, a superoxide dismutase mimetic, decreased Lp during IR by over 30% (P < 0.01). We conclude that IR induces a biphasic increase in postcapillary hydraulic conductivity. Reactive oxygen species impact both the first transient peak and the sustained second peak. However, the second peak is also dependent on WBC-endothelial cell adhesion. These serial measurements of postcapillary hydraulic conductivity may lead the way for optimal timing of pharmaceutical therapies in IR injury.

Endothelin-1 reduces mesenteric microvascular hydraulic permeability via cyclic AMP and protein kinase A signal transduction.

We have previously shown that endothelin-1 (ET-1) decreases microvascular hydraulic permeability. In this study, we tested the hypothesis that ET-1 exerts its permeability-decreasing effect through cAMP, cGMP, and protein kinase A (PKA) by determining the effect of ET-1 on venular fluid leak during inhibition of cAMP synthesis, inhibition of cGMP degredation, and inhibition of PKA. Rat mesenteric venules were cannulated to measure hydraulic permeability, L(p) (units x 10(-7)cm/(s cmH(2)O)). L(p) was measured during continuous perfusion of 80 pM ET-1 and either (1) an inhibitor of cAMP synthesis (10 microM 2',5'ddA), (2) an inhibitor of cGMP degradation (100 microM Zaprinast), or (3) an inhibitor of PKA (10 microM H-89). Inhibition of cAMP synthesis blocked the permeability decreasing effects of ET-1. The peak L(p) of the cAMP inhibitor alone and with ET-1 was 4.11+/-0.53 and 3.86+/-0.19, respectively (p=0.36, n=6). Inhibition of cGMP degradation did not block the permeability decreasing effects of ET-1. The peak L(p) during inhibition of cGMP degradation alone and with ET-1 was 2.26+/-0.15 and 1.44+/-0.09, respectively (p<0.001, n=6). Inhibition of PKA activation blocked the permeability decreasing effects of ET-1. The peak L(p) of the PKA inhibitor alone and with ET-1 was 2.70+/-0.15 and 2.59+/-0.15, respectively (p=0.38, n=6). The data support the notion that the signal transduction mechanism of ET-1 with regard to decreasing microvascular fluid leak involves cAMP production and PKA activation, but not cGMP degradation. Further understanding of intracellular mechanisms that control microvascular fluid leak could lead to the development of a pharmacologic therapy to control third space fluid loss in severely injured or septic patients.

Angiotensin II subtype AT1 and AT2 receptors regulate microvascular hydraulic permeability via cAMP and cGMP.

INTRODUCTION: Angiotensin II receptor subtypes (AT1 and AT2) have been shown to modulate microvascular fluid leak. However, their intracellular signal transduction pathways have not been elucidated. We hypothesized that AT1 activation exerts its permeability-increasing effect by provoking cGMP synthesis and inducing cAMP degradation and that AT2 activation decreases fluid leak by stimulating cAMP synthesis and enhancing cGMP degradation. METHODS: Using a microcannulation technique, hydraulic permeability (Lp) was measured in rat mesenteric venules. The messenger signal transduction of ATI was studied during continuous perfusion with the AT1 agonist, Sar1 plus either 1) a cGMP synthesis inhibitor, LY83583, or 2) an inhibitor of cAMP degradation, Rolipram. Likewise, AT2 signal transduction was studied with the AT2 agonist, CGP42112A, plus either 1) a cAMP synthesis inhibitor, dideoxyadenosine, or 2) an inhibitor of cGMP degradation, Zaprinast. Lp values are represented as mean +/- SEM x 10(-7) cm/s/cm H2O. For each group n = 6. RESULTS: Inhibition of cGMP synthesis blunted the permeability-increasing effect of AT1 agonism and decreased the peak Lp from 4.91 +/- 0.25 to 2.30 +/- 0.10 (P < 0.001). Inhibition of cAMP degradation also reduced the effect of AT1 agonism on peak L(p) from 2.25 +/- 0.22 to 1.30 +/- 0.13 (P < 0.001). Meanwhile, cAMP synthesis inhibition completely blocked the permeability-decreasing effect of AT2 agonism during which Lp increased from a baseline of 0.92 +/- 0.08 to a peak of 4.38 +/- 0.20 (P < 0.001). During inhibition of cGMP degradation, AT2 activation was able to decrease peak Lp from 2.26 +/- 0.15 to 1.46 +/- 0.05 (P < 0.001). CONCLUSIONS: When cGMP synthesis and cAMP degradation were inhibited, the effect on fluid leak by AT1 activation was blunted. Inhibition of cAMP synthesis completely blocked the effect of AT2 activation on fluid leak, while AT2 activation continued to decrease fluid leak despite inhibition of cGMP degradation. The AT1 receptor appears to increase fluid leak by stimulating both cGMP synthesis and cAMP degradation, while the AT2 receptor decreases fluid leak by stimulating cAMP synthesis, but not cGMP degradation.

Cyclic nucleotide second messengers (cAMP and cGMP) play a central role in signal transduction and regulation of mesenteric postcapillary fluid leak.

BACKGROUND: Endothelial cell receptors involved in post-injury/sepsis fluid extravasation are coupled to G-proteins that stimulate production of cGMP and cAMP. We hypothesize that cGMP and cAMP are endothelial second messengers that control microvascular permeability. The purposes of this series of experiments are to determine microvascular permeability under the following conditions: 1) reduced cGMP levels, 2) elevated cGMP levels, 3) reduced cAMP levels, and 4) elevated cAMP levels. METHODS: Rat mesenteric venules were cannulated and hydraulic permeability (Lp) was measured at 3 to 5 minute intervals during 1) cGMP synthesis inhibition, 2) inhibition of cGMP degradation, 3) cAMP synthesis inhibition, and 4) inhibition of cAMP degradation (n = 6 in each study group). Lp units are x10 cm(-7)/sec/cmH2O and represented as mean +/- SEM. RESULTS: Compared with baseline Lp (1.10 +/- 0.06), reduced cGMP levels by inhibiting its synthesis decreased Lp by over 50% (0.50 +/- 0.02, p < 0.001), while elevated cGMP levels by preventing its degradation increased Lp by more than 2-fold (0.91 +/- 0.10 to 2.26 +/- 0.15, p < 0.001). The reduction of cAMP levels by synthesis inhibition elevated Lp over 400% from 0.92 +/- 0.04 to 4.11 +/- 0.54 (p < 0.001), and elevation of cAMP level by blocking its degradation reduced Lp almost 50% from 1.11 +/- 0.04 to 0.59 +/- 0.06 (p < 0.001). CONCLUSIONS: The second messengers, cGMP and cAMP, contribute to the control mechanisms that govern fluid leak across the endothelial barrier: cGMP increases microvascular permeability, while cAMP decreases microvascular permeability. Endothelial cell cyclic nucleotide second messengers are pharmacologically accessible and may be targeted during post-injury/sepsis-associated microvascular fluid leak.

Quantification of surgical resident stress "on call".

BACKGROUND: We hypothesized that surgical resident stress involves both psychologic and physiologic components that manifest as changes in heart rate (HR) and circulating white blood cell (WBC) count. The purposes of this series of experiments were to monitor HR as a measure of stress "on call"; to monitor WBC count (1,000 cells/microL) during "on call" periods as a measure of stress; and to relate maximum HR and WBC count "on call" to surgical resident training level. STUDY DESIGN: HR was continuously documented by Holter monitor for 24hours "on call" in interns (n = 6), junior residents (n = 5), and senior residents (n = 5). Interns (n = 4), junior residents (n = 4), and senior residents (n = 4) during periods devoid of clinical responsibilities served as controls. WBC counts were obtained from residents "off" and "on call" for interns (n = 5) and junior residents (n = 5). RESULTS: Mean HR "on call" increased in all resident groups as compared with controls: intern mean HR increased from 71 +/- 3 to 87 +/- 2 beats per minute (bpm) (p = 0.003), junior resident mean HR increased from 74 +/- 3 to 88 +/- 4 bpm (p = 0.03), and senior resident mean HR increased from 69 +/- 2 to 80 +/- 2 bpm (p = 0.004). Intern maximum control HR was 119 +/- 3 and increased to 149 +/- 6 bpm (p = 0.005). The increase in maximum HR (control versus "on call") did not reach significance in junior residents (123 +/- 5 to 136 +/- 6 bpm, p = 0.14) and senior residents (115 +/- 6 to 116 +/- 3 bpm, p = 0.9). WBC count in interns increased from control values of 5.2 +/- 0.6 x 1,000 cells/microL to 7.5 +/- 0.9 x 1,000 cells/microL"on call" (p = 0.005). The WBC change in juniors was not significant (control: 6.8 +/- 0.7 x 1,000 cells/microL, "on call": 7.1 +/- 0.7 x 1,000 cells/microL; p = 0.37). CONCLUSIONS: When heart rate is used as an indicator of combined physiologic and psychologic stress, surgical residents achieve stress levels of tachycardia "on call." Surgical residents also exhibit an increase in circulating WBC count "on call." Both the degree of tachycardia and the increase in WBC count are inversely related to the level of training. Senior residents cope better with stress "on call" than junior residents and interns.

Albumin impacts the effects of tonicity on microvascular hydraulic permeability.

BACKGROUND: An increase in tonicity shrinks endothelial cells. This cell shrinkage may open inter-endothelial gaps and allow more fluid to escape from the microvasculature. This increase in microvascular permeability is not supported by clinical studies suggesting that water is pulled into the vascular space, not lost into the interstitium. We hypothesized that albumin influences the change in trans-endothelial water movement caused by alterations in tonicity by a mechanism other than oncotic pressure. MATERIALS AND METHODS: Hydraulic permeability (L(p)) was measured in rat mesenteric venules using the Landis micro-occlusion model. Measures of L(p) were obtained after successive perfusions with 1% albumin solution (BSA) of varying sodium chloride (NaCl) concentrations (85, 135, 185, and 235 mm) (n = 6). Additional venules were perfused with 7% NaCl followed by 7% NaCl + BSA and L(p) measured (n = 6). Units for L(p) are x10(-7) cm/sec(-1) cm/H(2)O(-1). RESULTS: As the NaCl concentration in BSA increased from 85 mm to 235 mm, L(p) decreased from 1.93 +/- 0.41 to 0.97 +/- 0.11. Compared to results without albumin, BSA with 185 mm NaCl decreased L(p) from 3.93 +/- 0.08 to 1.25 +/- 0.18 (P = 0.04), and BSA with 235 mm NaCl decreased L(p) from 6.14 +/- 0.05 to 0.96 +/- 0.11 (P = 0.002). There was a three-fold decrease in L(p) when BSA was added to the 7% NaCl solution (P = 0.02). CONCLUSIONS: Albumin attenuated the increase in L(p) that is associated with higher NaCl concentrations. Because this model controls for oncotic pressure, albumin may impact L(p) by a mechanism other than oncotic force. Albumin appears to stabilize the endothelial barrier during HS perfusion and prevents the loss of intravascular fluid. Appropriate albumin levels may play an important clinical role in modulating trans-endothelial fluid efflux during HS administration.

Endothelin-1 decreases postcapillary fluid efflux via prostacyclin release.

BACKGROUND: Endothelin-1 (ET-1) decreases water efflux across the endothelial barrier (Lp). ET-1 may exert this permeability-decreasing effect by stimulating prostacyclin (PGI2) release. The purposes of this study were to (1) examine the effect of PGI2 on Lp, (2) measure Lp after inhibition of PGI(2) synthesis, and (3) determine the effect of ET-1 on Lp during inhibition of PGI2 production. METHODS: After microscopic cannulation of mesenteric venules, Lp was measured during PGI2 infusion (0.1 micromol/L, 1 micromol/L, and 10 micromol/L; n = 6 in each group). Lp was also measured after 100 micromol/L of the PGI2 synthase inhibitor, tranylcypromine (TCPN) (n = 6). Finally, the influence of ET-1 on Lp during PGI2 synthase inhibition was assessed (n = 6). RESULTS: Compared to baseline Lp of 1.05 +/- 0.06, PGI2 decreased Lp at 1 micromol/L (Lp = 0.63 +/- 0.03, P < .003) and 10 micromol/L (Lp = 0.52 +/- 0.04, P < .0001). TCPN increased Lp compared to baseline (P < .0001). Compared to ET-1 alone, venules perfused with TCPN + ET-1 increased Lp (P < .005). Units for Lp ) are 10(-7) cm x sec(-1) x cmH2O(-1). CONCLUSIONS: We found that (1) PGI2 decreases Lp, (2) inhibition of PGI2 synthesis increases Lp, and (3) permeability-decreasing effects of ET-1 can be blocked by inhibiting PGI2 synthesis. These data suggest that constitutive production of PGI2 modulates basal microvessel permeability and that ET-1 may exert its permeability-decreasing effect via the stimulation of PGI2 release.