Phenoxybenzamine is more effective and less harmful than papaverine in the prevention of radial artery vasospasm

Analysis and study of the mechanism of narcotic addiction and withdrawal

Narcotic drugs refer to drugs that have anesthetic effects on the central nervous system, and they easily produce physical dependence and mental dependence and can be addictive due to continuous use, abuse or unreasonable use. In this paper, bioinformatics and data analysis and mining techniques were used to analyze the methylation differences in transcriptional and clinical data of narcotic addiction in public databases, to explore the mechanism of narcotic addiction, and to mine some norepinephrine drugs. This study confirmed the possibility of using norepinephrine as an auxiliary drug for drug addiction rehabilitation. In addition, we also conducted a similar analysis on the addiction of three drugs. The results showed that the differences in the body caused by the ingestion of opiates and cocaine were significantly greater than those caused by the ingestion of methamphetamine.

Antioxidants and Vasodilators for the Treatment of Noise-Induced Hearing Loss: Are They Really Effective?

We live in a world continuously immersed in noise, an environmental, recreational, and occupational factor present in almost every daily human activity. Exposure to high-level noise could affect the auditory function of individuals at any age, resulting in a condition called noise-induced hearing loss (NIHL). Given that by 2018, more than 400 million people worldwide were suffering from disabling hearing loss and that about one-third involved noise over-exposure, which represents more than 100 million people, this hearing impairment represents a serious health problem. As of today, there are no therapeutic measures available to treat NIHL. Conventional preventive measures, including public awareness and education and physical barriers to noise, do not seem to suffice, as the population is still being affected by damaging noise levels. Therefore, it is necessary to develop or test pharmacological agents that may prevent and/or diminish the impact of noise on hearing. Data availability about the pathophysiological processes involved in triggering NIHL has allowed researchers to use compounds, that could act as effective therapies, by targeting specific mechanisms such as the excess generation of free radicals and blood flow restriction to the cochlea. In this review, we summarize the advantages/disadvantages of these therapeutic agents, providing a critical view of whether they could be effective in the human clinic.

Intra-Arterial Labetalol and Nitroglycerin in Preventing Radial Artery Spasm Following Transradial Angiography: A New Approach

Background: Radial artery spasm (RAS) resulted from decreasing blood flow and activation of vasomotor system leads to a decrease in artery diameter, perfusion and patency, and increase the risk of procedure failure. In this study, we investigated the effects of intra-arterial administration of nitroglycerin and labetalol on radial artery diameter, RAS, and pain intensity in patients undergoing diagnostic radial angiography. Methods: Sixty-four patients randomly enrolled into one of the nitroglycerin (150 μg) or labetalol (500 μg) groups. The radial artery size, and the incidence of RAS were measured before, immediately after puncture, and at the end of treatment. Pain intensity was evaluated using a visual-analog-scale (VAS) at the end of the procedure. Hemodynamic status before, and during the procedure was also recorded. Results: Labetalol causes a significantly larger increase in radial diameter than nitroglycerin immediately after intra-arterial injection (2.24±0.58 mm vs. 1.65±0.39 mm, P-value<0.001). The rate of RAS immediately after vasodilator administration in the labetalol group was 3.1% vs. 12.5% in the nitroglycerin group (P-value=0.355), but the overall incidence (immediately after administration+ at the end of procedure) did not show a statistically significant difference (53.125% vs 31.25% respectively, P-value=0.076). The VAS score did not show a significant difference between two groups (1.15±0.44 in nitroglycerin vs. 1.50±0.91, P-value=0.063). Conclusion: Labetalol increases radial artery diameter more than nitroglycerin. However, the efficacy of labetalol in terms of RAS incidence, and patients’ pain was similar to nitroglycerin. Therefore, intra-arterial labetalol could be considered as one of the therapeutic options in clinical practice in order to reduce RAS and procedure failure.

Use of nitroglycerin and verapamil solution by organ bath technique in preparation of left internal thoracic artery for coronary artery bypass surgery

Background

The aim of this prospective study was to compare the effect of application of nitroglycerin and verapamil solution (GV) by organ bath technique with other methods of applications and solutions on the free blood flow of LITA. The technique was not described for in situ graft before.

Method

The patients were randomly assigned to four groups: group I (n_32, GV solution by organ bath technique), group II (n_30, papaverine solution by organ bath technique), group III (n_29, topical GV solution) or group IV (n_29, topical papaverine solution). In each patient, pedicled LITA was harvested; thereafter applied with the randomized different methods and solutions. The free flow from the distal end of the divided LITA was measured for 15 s under controlled hemodynamic conditions after harvesting (Flow 1). The flow of LITA was measured again just prior to anastomosing the conduit (Flow 2).

Result

The mean blood flow in LITA was 56.2 ± 5.0 ml/min before application of solutions. After application, the mean blood flow in group I:102.3 ± 7.0 ml/min, in group II: 92.7 ± 3.4 ml/min, and in group III: 88.6 ± 2.2 ml/min and in group IV: 81.4 ± 2.1. Proportional increases in blood flow observed in group I (82.6%) > group II (65.1%) > group III (57.6) > group IV (44.8%) (p < 0.05).

Conclusions

GV solution by organ bath technique is effective and superior in comparison to use of papaverine using organ bath technique or topical spray of GV or papaverine solution.

Relaxant effect of the prostacyclin analogue iloprost on isolated human radial artery: An approach for the reversal of graft spasm

Radial artery graft spasm in the perioperative or postoperative period of coronary bypass surgery necessitates urgent treatment due to risk of graft failure and mortality. Herein, we evaluated the effect of iloprost, a prostacyclin (PGI₂) analogue, against the contractions produced by noradrenaline and potassium chloride on isolated human radial artery. Following the determination of endothelial and vascular relaxing capacities of the arteries, iloprost (10^-9M-10^-6M) was cumulatively applied on rings precontracted submaximally with the spasmogens. In some rings, the response to iloprost was assessed following pretreatment with nitric oxide (NO) synthase inhibitor, l-NAME (3×10^-4M,30min). Iloprost produced complete relaxations on radial artery rings precontracted with noradrenaline whereas, only moderate relaxations against the contractions induced by potassium chloride. Notably, the relaxation to iloprost was remarkably blunted in radial arteries with impaired endothelial function. Moreover, the relaxation to iloprost was unchanged in rings pretreated with l-NAME. Our results demonstrated that iloprost could be a potent relaxant agent in reversing radial artery spasm, particularly initiated by noradrenaline, possibly acting via an endothelium-mediated mechanism unrelated to NO.

Antispastic Management in Arterial Grafts in Coronary Artery Bypass Grafting Surgery

Arterial grafts have long-term patency superior to vein grafts but have a tendency to develop spasm that can lead to potentially life-threatening complications. A perfect antispastic protocol should include advanced surgical technique and adequate pharmacologic methods. All pharmacologic vasodilator drugs relax the vessel through specific mechanisms, and therefore, there is no perfect, single best vasodilator to prevent or treat spasm of the arterial graft against all mechanisms of contraction. One of the choices is to use a combination of pharmacologic vasodilators targeting different mechanisms of spasm to obtain the reliable and best effect.

Radial artery as graft for coronary artery bypass surgery: Advantages and disadvantages for its usage focused on structural and biological characteristics

Radial artery (RA) is the most popular arterial graft after the left internal thoracic artery in both low- and high-risk patients undergoing coronary artery bypass grafting. Various arterial grafts such as the right internal thoracic artery, the right gastroepiploic artery, and the inferior epigastric artery have also gained ground over the past 30 years because of the intimal hyperplasia and atherosclerosis of the saphenous vein leading to late graft occlusion. In this review article we would like to present the utility of the RA as a graft, focused mainly on its structural and biological characteristics.

Effect of DETA-NONOate and papaverine on vasodilation of human internal mammary artery

In this study, the relaxatory effect of DETA-NONOate is compared with that of papaverine on isolated human internal mammary artery. We investigated the inhibitory effects of DETA-NONOate and papaverine on phenylephrine-induced contractile response in internal mammary artery segments. The internal mammary artery segments, taken from methodologically matched patients who underwent coronary artery bypass grafting, were prepared, placed in an organ bath, and contracted with phenylephrine (10−9 to 10−4 mol/L) to investigate their relaxatory response to DETA-NONOate or papaverine. Phenylephrine dose–response contraction was obtained after 1, 2, and 3 h in segments pre-incubated with DETA-NONOate or papaverine for 30 min. The EC50 that presented for internal mammary artery segments incubated with DETA-NONOate was 3.523 ± 1.2696 × 10–7 mol/L, and for papaverine was 3.467 ± 1.2145 × 10–6 mol/L. In segments pre-incubated with DETA-NONOate, the contractile response to phenylephrine was suppressed in the first 2 h post-incubation, compared with control responsive groups (p < 0.05), but this inhibition was revoked after 3 h post-incubation. We showed that DETA-NONOate has a more significant relaxative effect by comparison with papaverine; moreover, continuous and long-lasting nitric oxide production by DETA-NONOate might be of great importance for the outcome from coronary artery bypass grafting, when internal mammary artery is used as a conduit.

Verapamil and Nitroglycerin Improves the Patency Rate of Radial Artery Grafts

The best way to prevent spasm of the radial artery is still under investigation. We retrospectively compared the effectiveness of topical verapamil-nitroglycerin with papaverine in preventing graft spasm in 215 patients who underwent isolated conventional coronary artery bypass using a radial artery. Postoperative angiographic data were successfully collected in 116 patients. Perioperative radial artery graft spasm was observed in 2 patients in the papaverine group and 1 in the verapamil-nitroglycerin group; this difference was not considered significant. Complete or functional occlusion was detected by postoperative angiography in 13 grafts (10 in the papaverine group and 3 in the verapamil-nitroglycerin group). Multivariate regression analysis revealed that topical papaverine and grafting to the right coronary artery significantly increased the rate of occlusion of radial artery grafts. Although further studies are needed, our data support the view that topical verapamil-nitroglycerin reduces the incidence of radial artery graft occlusion.

Phenoxybenzamine treatment can lead to loss of endothelial cell viability

Phenoxybenzamine, an irreversible alpha-adrenoceptor antagonist, is used as a topical treatment against catecholamine-induced contraction in radial artery bypass grafts. Published data suggest that a wide range of phenoxybenzamine doses may be equally effective. This study aimed to investigate whether lower doses of phenoxybenzamine would benefit grafts by better preserving endothelium. To this end human vascular endothelial cells were isolated from sections of radial artery or saphenous vein, and treated with phenoxybenzamine for 30 min. Cells were then washed free of drug and viability assayed using a resazurin-based toxicology assay or returned to culture for assay at 24 h. Phenoxybenzamine treatment showed a dose-dependent effect on cell viability over several clinically employed concentrations. Concentrations above 0.1 mM led to a loss of viability, which became more pronounced with time. The loss of viability was shown to be independent of the carrier used, as results were identical when phenoxybenzamine was dissolved in dimethylsulphoxide, which alone did not affect viability. Changes in pH alone were also not sufficient to affect viability. In conclusion, phenoxybenzamine treatment is likely to cause damage to graft endothelium if employed at concentrations above 0.1 mM (0.03 mg/ml). Phenoxybenzamine may be safely used at lower doses with no potential loss of endothelial cell viability.

Isoprostanes constrict human radial artery by stimulation of thromboxane receptors, Ca2+ release, and RhoA activation

OBJECTIVES

Radial artery vasospasm remains a potential cause of early graft failure after coronary bypass graft surgery, despite pretreatment with alpha-adrenergic or calcium channel blockers. We examined the roles of isoprostanes and prostanoid receptors selective for thromboxane A2 in the vasoconstriction of human radial arteries.

METHODS

Human radial arterial segments were pretreated intraoperatively with verapamil/papaverine or nitroglycerine/phenoxybenzamine, or not treated. In the laboratory, we measured isometric contractions in ring segments, vasoconstriction in pressurized segments, and changes in [Ca2+] and K+ currents in single cells.

RESULTS

Although phenoxybenzamine eliminated adrenergic responses, the isoprostane 15-F(2t)-IsoP and 2 closely related E-ring molecules (15-E(1t)-IsoP and 15-E(2t)-IsoP) still evoked powerful contractions; 15-E(2t)-IsoP was approximately 10-fold more potent than the other 2 agents. Responses were mediated through thromboxane receptors because they were sensitive to ICI-192605. Furthermore, they were sensitive to the Rho-kinase inhibitors Y-27632 or H-1152 (both 10(-5) mol/L) or to cyclopiazonic acid (which depletes the internal Ca2+ pool), but not to nifedipine. In single cells, 15-E(2t)-IsoP elevated [Ca2+]i and suppressed K+ current.

CONCLUSIONS

Isoprostanes accumulate after coronary artery bypass graft surgery, yet none of the currently available antispasm treatments for radial artery grafts is effective against isoprostane-induced vasoconstriction. It is imperative that more specific treatment strategies be developed. We found that isoprostane responses in radial arteries are mediated by prostanoid receptors selective for thromboxane A2 with activation of Rho-kinase and release of Ca2+. Pretreatment of radial artery grafts with Rho-associated kinase inhibitors may potentially reduce postoperative graft spasm. Clinical studies to test this are indicated.

Normothermia is the Key for the Treatment of Internal Thoracic Artery Spasm

BACKGROUND

Free flow of the internal thoracic artery decreases commonly after harvesting because of spasm. Tissue heat loss is inevitable during surgery. The aim of this study was to compare the internal thoracic artery pedicle rewarming method with topical papaverine applications in different thermal conditions.

METHODS

Patients (n = 120) were organized in to 6 equally sized groups. The effects of topical papaverine application at room temperature, topical heated papaverine (at 37 degrees C) application, internal thoracic artery pedicle storage in normothermic conditions, pedicle storage in normothermic conditions combined with topical papaverine application, and pedicle storage in normothermic conditions combined with topical heated papaverine application were investigated. In the control group, no treatment was applied and the pedicle was stored in room temperature conditions. We measured internal thoracic artery free flows at 3 stages: at the initiation of harvesting, after total harvesting, and after antispasmodic treatment. Durations of the stages were recorded. At each stage hemodynamic parameters, tissue and core temperatures were also monitored.

RESULTS

Internal thoracic artery pedicle temperature significantly decreased simultaneously with the free flow after the harvesting procedure. Recovery of the physiologic temperature state, provided by storing the internal thoracic artery pedicle in normothermic conditions, improved the flow and increased the efficiency of topically applied papaverine on the vasospasm of the internal thoracic artery.

CONCLUSION

Topical application of heated papaverine itself does not warm pedicle tissue, but papaverine efficiency increases when the pedicle is stored in normothermic conditions. Preserving internal thoracic artery pedicles in normothermic conditions can be the preferred treatment for spasms.

Radial Artery Graft Treatment With Phenoxybenzamine is Clinically Safe and May Reduce Perioperative Myocardial Injury

BACKGROUND

Phenoxybenzamine effectively reduces radial artery (RA) spasm in vitro, but clinical data supporting its use during coronary revascularization are lacking. Therefore, the purpose of this study was to evaluate the clinical safety and efficacy of RA treatment with phenoxybenzamine.

METHODS

Data were collected prospectively on 698 patients who underwent coronary artery bypass grafting with a RA between 1997 and 2005. Of these, 311 patients received RA grafts incubated in 2 mg/mL phenoxybenzamine for 15 minutes, and 387 patients received RA grafts treated with verapamil and nitroglycerin (VG solution). Demographic, operative, and postoperative data were compared retrospectively using multivariate regression techniques.

RESULTS

The incidence of perioperative myocardial events (defined as either low cardiac output syndrome or perioperative myocardial infarction) was significantly reduced in the phenoxybenzamine group (6.8% vs 11.9%, phenoxybenzamine vs VG solution; p = 0.03). Perioperative myocardial enzyme release, as measured by postoperative maximum creatine kinase, was also reduced in the phenoxybenzamine group (743.0 +/- 677.9 vs 937.2 +/- 1236.8 U/L, phenoxybenzamine vs VG solution; p = 0.014). After adjusting for patient and procedural factors, the use of phenoxybenzamine was independently associated with reductions in peak creatine kinase (by -343.0 +/- 136.7 U/L; p = 0.012) and peak troponin T level (by -0.50 +/- 0.19 ng/mL; p = 0.010). No differences in vasopressor support, length of stay, or other complications were observed.

CONCLUSIONS

Treatment of RA grafts with phenoxybenzamine was associated with a reduction in perioperative myocardial injury and adverse cardiac events in this study population. Investigations to further evaluate the potential benefits of phenoxybenzamine in randomized settings are warranted.

Development of a local vasodilator delivery system using fibrin glue to prevent arterial graft from spasm

The clinical benefits of coronary artery bypass graft operations can be compromised by postoperative vasospasm. Traditionally, local papaverine (PPV) has been employed during the procedure to prevent and counteract vasospasm. But the relatively short action period limited its application. Fibrin glue (FG) might be a potential carrier of PPV for counteracting vasospasm in a longer action period than PPV solution. After FG incorporated with PPV (PPV-FG) was locally administrated in axillary and femoral arteries of dogs, PPV concentrations in artery vessels surrounding the administration sites were compared with the concentrations at the same sites in dogs given PPV solution. The properties of PPV's release in vitro and maintenance in vessel as well as the influence on the mean peripheral blood pressure and drug concentration in peripheral vein after the introduction PPV-FG on the surface of artery in dogs were evaluated. FG was considered to provide a sustained release of PPV and could maintain a high PPV concentration in artery vessel around the administration site. The results suggested that FG was an effective substrate for reserving PPV in the administrated site in a defined period.

Comparison of the pretreatment effects of mixed vasodilators (3-D solution) on radial and internal thoracic arteries by using a 3-dimensional anaglyph electron microscope technique

OBJECTIVE

Currently, internal thoracic arteries (ITA) and radial arteries (RA) are the first choice of conduits for coronary artery bypass grafts (CABG). Because the perioperative vasospasm continues to be a major problem, a number of pharmacologic agents such as papaverine, calcium receptor blockers, nitroglycerine, and phenoxybenzamine have been suggested as topical antispasmodics that may be used in the pre- and postoperative periods. In the present study, we investigated the quantitative efficacies of the mixed solution, which included verapamil, nitroglycerin, and papaverine, on RA and ITA using a scanning electron microscope with a 3-dimensional anaglyph technique.

METHODS

Diameter changes of RA and ITA in response to clinically important vasodilators were measured on 40 RA and 40 ITA rings from patients who had been subjected to coronary artery bypass procedure after 20 minutes of ex vivo incubation with verapamil (45 microg/L), nitroglycerin (45 microg/L), papaverine solution (266 micromol/L or 0.1 micro/mL), and 30 mL autologous heparinized whole blood (individual patient's blood obtained before cardiopulmonary bypass contained 100 IU of heparin per kg of patient weight). The pretreatment action was assessed by measuring the response to vasodilators.

RESULTS

In all cases, we did not observe graft vasospasm in any of the conduits during the intraoperative period between postanastomosis and sternal closure. In the postoperative period, we did not record any evidence of ischemic change in patients' electrocardiographic and myocardial enzyme analyses. None of the cases required inotropic support after the operation. The diameters of the pretreated RA and ITA were: minimum, 2.1 mm; maximum, 4.0 mm; and mean value, 2.80 +/- 0.46 mm. The diameters of the pretreated ITA were: minimum, 1.2 mm; maximum, 2.5 mm; and mean value, 1.76 +/- 0.35 mm. Incubated arterial segment diameters for the RA were: minimum, 2.8 mm; maximum, 5.2 mm; and mean value, 3.95 +/- 0.65 mm. These values for the ITA were: minimum, 1.5 mm; maximum, 3.9 mm; and mean value, 2.37 +/- 0.50 mm. These findings were statistically significant for both arterial grafts (P <.05).

CONCLUSIONS

According to our study findings, the mixed solution demonstrates a broad range of efficacy. We conclude that the described vasodilator solution with heparinized autologous blood seems to be very effective and may be used as a pretreatment agent in CABG conduits. Although papaverine has the shortest duration of action, its efficiency is increased by verapamil and nitroglycerin, in our opinion. To the best of our knowledge, high-quality imaging of CABG conduits with the 3-D anaglyph technique using a scanning electron microscope was a first in the literature. This technical approach may be used for confirming the ultrastructural anatomy and the quantitative vasodilator effects of arterial conduits. We believe that valuable anatomo-pathologic details of the CABG conduit can be obtained by this technique.

Efficacy of Physiologic Temperature on the Spasm of Harvested Radial Artery

BACKGROUND

The potential disadvantage of using the radial artery for coronary artery bypass grafting is its increased tendency to vasospasm. Therefore, different antispastic agents are being used in the perioperative and postoperative period. During the preparation of the radial artery, normal local and systemic temperatures are lost.

METHODS

We investigated the effects of topical normal saline solution at 20 degrees C (group SI), normal saline solution at 36 degrees C (group SII), diltiazem at 20 degrees C (group DI), and diltiazem at 36 degrees C (group DII) on radial artery free flow. Each group contained 10 patients undergoing coronary bypass surgery. Free flow and local temperature were measured at 3 stages: after the exploration and preparation of the distal 3 cm of the radial artery, after total preparation of the radial artery, and a median of 12 minutes after the pedicle had been sprayed with one of the agents.

RESULTS

Parallel to the significant decrease of the second local temperatures (P < .001), the second flow of the 4 groups decreased significantly (P < .001).

CONCLUSION

Hypothermia plays an important role in radial artery vasospasm, and normothermia may be the best perioperative vasodilating agent since the normal radial artery flows were reached with normothermia.

Comparative Effects of Tolazoline and Nitroprusside on Human Isolated Radial Artery

BACKGROUND

The radial artery is increasingly being used in coronary revascularization as an alternative conduit to a saphenous vein graft. Its perfect endothelial capacity provides a high patency rate comparable with the internal mammary artery (IMA). However, its spastic characteristics cause difficulties during its intraoperative preparation and may lead to early postoperative graft failure. Thus, treatment and/or prevention of radial artery spasm with an effective vasodilator agent is essential for its longevity. Endogenous vasoconstrictors, including noradrenaline, endothelin-1, and thromboxane A2, are likely to play a role in the pathogenesis of graft spasm. In the present study, we evaluated the vasorelaxant effect of tolazoline, a nonselective alpha-adrenoceptor blocker, against the contractions induced by various spasmogenic agents in an isolated human radial artery.

METHODS

Tolazoline (10(-9)-10(-4) M) or sodium nitroprusside (SNP, 10(-9)-10(-4) M) were cumulatively applied on radial artery rings precontracted submaximally with noradrenaline, endothelin-1, thromboxane analogue, U46619, or potassium chloride. In addition, some rings were pretreated with tolazoline (4 x 10(-6) M) for 30 minutes and the contractile response curve to noradrenaline was assessed in its presence.

RESULTS

Tolazoline effectively reversed noradrenaline-induced contractions in the radial artery, whereas it failed to produce remarkable relaxations on rings contracted with other spasmogenic agents, while SNP overcame the contractions induced by all spasmogens to a similar extent. In addition, brief pretreatment of radial artery rings with tolazoline significantly inhibited the contractions to noradrenaline.

CONCLUSIONS

Tolazoline is not as broadly effective as SNP against all spasmogens investigated; however, it may be effective in counteracting alpha-adrenoceptor-mediated vasospasm in human radial arteries.

Effects of Papaverine and Glycerilnitrate-Verapamil Solution as Topical and Intraluminal Vasodilators for Internal Thoracic Artery

BACKGROUND

Arterial spasm is described as an event occurring after left internal thoracic artery (LITA) harvesting. Many vasodilators have been used to treat or prevent LITA spasm. The aim of this study is to compare the effects between glyceril-trinitrate/verapamil (GV) solution and papaverine to treat LITA spasm and to determine the best delivery method.

METHODS

One hundred consecutive ischemic patients were randomly assigned to three groups: group GV (n = 34, GV solution), group P (n = 33, papaverine), or group C (n = 33, normal saline). In each patient, pedicled LITA was harvested, thereafter sprayed with the randomized solution, and covered with a sponge. Fifteen minutes after heparin administration, LITA was distally divided; flow per minute was calculated after measuring the free flow for over 15 seconds; this is named "topical free flow." Then, the vasodilator was injected intraluminally and free flow per minute was measured; this is called "intraluminal free flow."

RESULTS

Analysis of variance was applied to detect differences among groups; paired-sample t test was used for LITA topical free flow versus intraluminal free flow within single groups. Mean LITA free flows were as follows: group GV, topical free flow = 38.6 +/- 25.2 mL/min versus intraluminal free flow = 58.8 +/- 29 mL/min (p < 0.0001); group P, topical free flow = 45.4 +/- 38.9 mL/min versus intraluminal free flow mL/min (p < 0.0001); group C, topical free flow = 31.6 +/- 19.9 mL/min versus intraluminal free flow = 34 +/- 19.8 mL/min (p = 0.14). Topical free flow difference among the three groups was not statistically significant (p = 0.1); intraluminal free flow difference was statistically significant (p = 0.001). Intraluminal free flow in group GV and in group P were higher than intraluminal free flow in group C (p = 0.004 and 0.001, respectively). Intraluminal free flow of group P was higher than that of group GV; this difference did not reach statistical significance (p = 1.00).

CONCLUSIONS

Glyceril-trinitrate/verapamil solution and papaverine are able to treat the spasm and increase the flow of the LITA, when they are used intraluminally. When used topically, these vasodilator agents do not ensure an optimal free flow.

Can the Use of the Radial Artery Be Expanded to All Patients with Different Surgical Grafting Techniques? Early Clinical and Angiographic Results in 600 Patients

OBJECTIVE

The use of the radial artery (RA) as a conduit for coronary artery bypass grafting (CABG) is gaining in popularity worldwide and is being increasingly adopted by many cardiac surgeons. Encouraged by our satisfactory early experience with the use of the RA conduit, we have expanded its use to more than 90% of all coronary surgery patients. The aim of the present study was to review our clinical and angiographic results when the use of the RA conduit was expanded to all patients including those aged 65 years and older and diabetics with different surgical grafting techniques.

METHODS

The records of 600 consecutive patients who underwent isolated CABG using the RA graft at Harefield Hospital between January 1999 and August 2002 were reviewed retrospectively. Ninety-three (15.5%) patients consented and underwent angiography before discharge at the earliest on the fourth postoperative day, aiming to look at the quality of anastomoses and the patency of the RA grafts.

RESULTS

The 600 patients had 613 RA grafts to perform 652 distal RA anastomoses. The proximal ends of 515 (84%) RA grafts were anastomosed to the aorta, 98 (16%) RA grafts were constructed as Y-grafts with 49 (8%) RA off a vein graft hood, and 49 (8%) RA grafts were constructed as T- or Y-grafts off an internal thoracic artery (ITA) graft. The proximal ends of 19 (19/294 or 6.5%) vein grafts were constructed as Y-grafts off the RA grafts. Two hundred and sixty-one (43.5%) patients were above the age of 65 years and 111 (18.5%) patients were diabetics. There were four in-hospital deaths (0.6%) among the study patients. Six (1%) patients developed forearm hematoma/seroma postoperatively. The operation time, the hospital stay, and the incidence of conduit harvest site infection for the patients who had vein grafts in addition to the RA grafts were significantly higher than those of patients who had RA grafts only. On postoperative angiography, 86 out of 93 (92.5%) RA grafts were found to be patent with good quality distal anastomoses. The maximum stenosis of the coronary arteries bypassed by the patent 86 RA grafts was 82.6 +/- 6.2%, while it was 56.3 +/- 15.4% for the coronary arteries bypassed by the occluded seven RA grafts, p < 0.001.

CONCLUSION

The use of the RA can be expanded to all patients with different surgical grafting techniques and provides satisfactory clinical and angiographic outcomes.

Effects of hydrostatic distention on in vitro vasoreactivity of radial artery conduits

BACKGROUND

Surgical preparation of coronary conduits may affect early and long-term patency through endothelial and smooth muscle injury. We investigated the effect of hydrostatic distention on the in vitro endothelial function and contractile properties of the human radial artery.

METHODS

Human radial arteries were harvested and distended to physiologic pressure or suprasystemic pressure (>300 mm Hg) by using heparinized whole blood for 2 minutes. Distal segments were retrieved and prepared into 3-mm rings. These were mounted and stretched to optimum resting tension in oxygenated Krebs solution at 37 degrees C. Contraction responses to potassium, norepinephrine, and serotonin and relaxation responses to acetylcholine and nitroprusside were evaluated. Undistended radial artery segments were used as controls.

RESULTS

Vasocontraction to all 3 contractile agonists was significantly different between groups. The radial artery subjected to suprasystemic pressure distention achieved the lowest percentage of maximum contraction (potassium, P <.001; norepinephrine, P <.05; serotonin, P <.05). The median effective concentration was also significantly reduced in this group, indicating increased sensitivity to all 3 agonists. Receptor-mediated contractility was significantly reduced in both distended groups when compared with controls. Relaxation to acetylcholine and nitroprusside was significantly reduced in the suprasystemic pressure-distended group, which had a tendency to vasospasm when exposed to a physiologic concentration of acetylcholine (10(-6) mol/L). Median effective concentrations for both acetylcholine and nitroprusside were not different between groups.

CONCLUSIONS

Excessive distention of the radial artery leads to a significant reduction in vasoreactivity, which may be attributed to a disruption of the vascular endothelium and media, with a propensity for graft spasm with exposure to acetylcholine.

Pharmacological assessment of composite arterial conduits using angiography early in the postoperative period

OBJECTIVES

Muscular arteries are vulnerable to vasospasm unlike elastic arteries. Having developed experimental models of composite arterial grafts, we assessed and compared the responses of the grafts with different pharmacological agents using angiography early in the postoperative period.

SUBJECTS AND METHODS

We harvested the internal thoracic artery (ITA) and brachial-median artery (BMA) from 10 sheep. BMA was used as an alternative to the radial artery. Each vessel was assessed histologically and morphologically. Then, a serial composite graft was constructed so that BMA was interposed. On postoperative day one or two, angiography was performed on the composite graft to measure the diameter of each vessel in response to phenylephrine (alpha-adrenergic receptor agonist), nitroglycerin+phenylephrine, and milrinone+phenylephrine.

RESULTS

The BMA had a wide media layer which consisted of abundant smooth muscle cells. The combined intima and media were thicker in BMA than in ITA (p<0.01). After injection of phenylephrine, the BMA diameter decreased (2.5+/-0.4 mm to 1.9+/-0.3 mm, p<0.01), while the ITA diameter remained unchanged (3.7+/-0.2 mm to 3.6+/-0.2 mm). Continuous infusion of nitroglycerin or milrinone prevented phenylephrine-induced vasoconstriction of the BMA (p<0.05).

CONCLUSIONS

These results suggest that muscular arteries have a more pronounced vasoconstrictive response to alpha-adrenergic receptor agonists than the elastic arteries. To avoid potential decrease in graft flow of muscular artery, it is advisable to use a vasodilator nitroglycerin or milrinone early in the postoperative period.

Duplex ultrasonography predicts safety of radial artery harvest in the presence of an abnormal Allen test

BACKGROUND

The Allen test is commonly used to assess collateral hand circulation before radial artery harvest for coronary artery bypass grafting. However there is no consensus as to whether an abnormal Allen test is an absolute or relative contraindication to radial artery harvesting. We assessed the safety of harvesting the radial artery using arterial duplex ultrasonography in patients with an abnormal Allen test.

METHODS

Two hundred and eighty-seven consecutive patients scheduled for total arterial coronary revascularisation underwent preoperative Allen tests over a 34-month period. Patients with an abnormal Allen test underwent duplex ultrasonography preoperatively to assess the adequacy of the ulnar collateral supply and the suitability of the radial artery for harvesting.

RESULTS

Two hundred and forty-four patients (85%) had a normal left Allen test and proceeded directly to radial artery harvest. Forty-three patients (15%) with an abnormal left Allen test underwent duplex ultrasonography scans and of those, 5 patients had an abnormal scan. These patients underwent scanning of the contralateral forearm. Three patients had a normal right forearm arterial duplex scan and the right radial artery was harvested. The mean diameter of the radial and ulnar arteries was not significantly different between the patients with normal and abnormal duplex ultrasonograms. There were no ischemic hand complications in this series.

CONCLUSIONS

The Allen test is a quick, easy, and reliable screening test before radial artery harvesting in the majority of patients. Duplex ultrasonography predicts safe radial artery harvest in the majority of patients with an abnormal Allen test.

Comparative efficacies and durations of action of phenoxybenzamine, verapamil/nitroglycerin solution, and papaverine as topical antispasmodics for radial artery coronary bypass grafting

OBJECTIVE

Radial arteries are increasingly used as conduits for coronary artery bypass grafts, but perioperative graft vasospasm continues to be a concern. Phenoxybenzamine, verapamil/nitroglycerin solution, and papaverine have been advocated as topical antispasmodic agents. We compared the relative efficacies and durations of action of these agents.

METHODS

Isometric tension developed in response to clinically important vasoconstrictors was measured in 100 radial artery rings (from patients undergoing coronary artery bypass grafting, n = 25) after 15 minutes of ex vivo incubation with phenoxybenzamine, verapamil/nitroglycerin solution, papaverine, or vehicle (control). Duration of action was assessed by measuring responses to vasoconstrictors in antispasmodic pretreated and control rings at intervals through 5 hours.

RESULTS

Verapamil/nitroglycerin solution reduced vasoconstriction in response to epinephrine, angiotensin II, prostaglandin F(2alpha), and phenylephrine but its effect had almost completely waned after 5 hours. Phenoxybenzamine prevented vasoconstriction in response to epinephrine, dopamine, and phenylephrine, with its effect lasting at least 5 hours. Papaverine had limited antispasmodic efficacy and prevented vasoconstriction in response to potassium (60 mmol/L) and phenylephrine for only 1 hour at the longest.

CONCLUSIONS

Verapamil/nitroglycerin solution has a broad efficacy against a range of vasoconstrictors but a limited duration of action. Papaverine has the shortest duration of action. Phenoxybenzamine is an effective agent with a prolonged duration of action, specifically preventing catecholamine mediated vasospasm of radial artery conduits.

Pretreatment with phenoxybenzamine attenuates the radial artery's vasoconstrictor response to α-adrenergic stimuli

BACKGROUND

Although the radial artery bypass conduit has excellent intermediate-term patency, it has a proclivity to vasospasm. We tested the hypothesis that brief pretreatment of a radial artery graft with the irreversible adrenergic antagonist phenoxybenzamine attenuates the vasoconstrictor response to the vasopressors phenylephrine and norepinephrine compared with the currently used papaverine/lidocaine.

METHODS

Segments of human radial artery grafts were obtained after a 30-minute intraoperative pretreatment with a solution containing 20 mL of heparinized blood, 0.4 mL of papaverine (30 mg/mL), and 1.6 mL of lidocaine (1%). The segments were transported to the laboratory and placed into a bath containing Krebs-Henseleit solution and 10, 100, or 1000 micromol/L phenoxybenzamine or vehicle. The segments were tested in organ chambers for contractile responses to increasing concentrations of phenylephrine and norepinephrine (0.5-15 micromol/L).

RESULTS

Contractile responses to 15 micromol/L phenylephrine in control radial artery segments averaged 44.2% +/- 9.1% of the maximal contractile response to 30 mmol/L KCl. Papaverine/lidocaine modestly attenuated contraction to 15 micromol/L phenylephrine (32.1% +/- 5.9%; P =.22), but 1000 micromol/L phenoxybenzamine completely abolished radial artery contraction (-7.2% +/- 4.4%; P <.001). The effect of 10 and 100 micromol/L phenoxybenzamine on attenuating vasocontraction was intermediate between 1000 micromol/L phenoxybenzamine and papaverine/lidocaine. Responses to 15 micromol/L norepinephrine in control radial artery segments averaged 54.7% +/- 7.5% of maximal contraction to 30 mmol/L KCl. Papaverine/lidocaine modestly attenuated the contraction response of radial artery segments (35.6% +/- 5.1%; P =.04). In contrast, 1000 micromol/L phenoxybenzamine showed the greatest attenuation of norepinephrine-induced contraction (-10.5% +/- 2.0%; P <.001).

CONCLUSIONS

A brief pretreatment of the human radial artery bypass conduit with 1000 micromol/L phenoxybenzamine completely attenuates the vasoconstrictor responses to the widely used vasopressors norepinephrine and phenylephrine. Papaverine/lidocaine alone did not block vasoconstriction to these alpha-adrenergic agonists.

Phenoxybenzamine treatment is insufficient to prevent spasm in the radial artery: the effect of other vasodilators

OBJECTIVES

After its reintroduction as an arterial graft in coronary artery surgery, the radial artery is now established as an alternative arterial conduit, with good early and midterm patency. However, because of the concern about its vasospasticity, numerous vasodilator strategies have been used. Recently the use of the irreversible alpha-adrenergic antagonist phenoxybenzamine has been proposed. Although this treatment is effective in eliminating the vasoconstriction mediated by noradrenaline, the contribution of other circulating vasoconstrictors to vasospasm could be as important. This study investigates the response of radial arteries treated with phenoxybenzamine to vasoconstrictor stimuli and possible preventative strategies.

METHODS

In vitro, sections of radial artery, pretreated with phenoxybenzamine after harvesting, were stimulated with maximal concentrations of the vasoconstrictors noradrenaline, vasopressin, angiotensin II, KCl, and endothelin-1. In matched segments of artery, vasoconstrictor responses were recorded in the presence of diltiazem, glyceryl trinitrate, and papaverine and compared with phenoxybenzamine-treated samples.

RESULTS

Phenoxybenzamine-treated radial artery failed to respond to noradrenaline but did respond to vasopressin, angiotensin II, endothelin-1, and KCl. Diltiazem was largely ineffective against contractile stimuli apart from KCl. Glyceryl trinitrate and papaverine significantly reduced responses to all of the vasoconstrictors tested.

CONCLUSION

In phenoxybenzamine-treated sections of radial artery, circulating vasoconstrictor agonists may still contribute to the induction of spasm. Additional vasodilator strategies may be required to completely prevent vasospasm.

Use of radial artery graft reduces the morbidity of coronary artery bypass graft surgery in patients aged 65 years and older

BACKGROUND

The use of the radial artery graft in patients aged 65 years and older could prevent the occurrence of leg wound infection, which is known to increase the morbidity of coronary artery bypass grafting surgery.

METHODS

We reviewed, retrospectively, 261 patients aged 65 years and older (age range 65 to 93 years), who underwent coronary artery bypass grafting surgery between February 1998 and August 2001. All the patients received at least one radial artery graft in addition to either a left internal thoracic artery, right internal thoracic artery, or saphenous vein graft as required. Saphenous vein grafts were used in 141 (54.1%) patients (group 1), and these were compared to 120 (45.9%) patients (group 2) who received only arterial conduits. Angiography was performed on 26 consecutive patients. The aim of the study was to review the clinical and angiographic outcomes in this population.

RESULTS

The mean number of distal anastomoses performed was 2.98. Mean global operating time was 204 minutes. This time dropped to 201 minutes in group 1 versus 231 minutes in group 2; p = 0.009. Sixteen (11.3%) patients receiving saphenous vein grafts had leg wound infection whereas only 1 (0.3%) patient of the global population had a forearm infection. The mean global hospital stay was 9.81 days; this duration increased to 13 days when leg wound infection occurred versus 9.1 days when infection did not occur; p = 0.008. Twenty-six (10%) patients underwent an early angiographic study. Twenty-four (92.3%) radial artery grafts were patent.

CONCLUSIONS

The routine use of radial artery grafts in patients aged 65 years and older is feasible, safe, and does not increase mortality, morbidity, or the complexity of coronary artery bypass grafting surgery.

Usefulness of hydrophilic coating on arterial sheath introducer in transradial coronary intervention

Radial artery spasm is one of the major problems during transradial coronary intervention (TRI). The sheath introducer with hydrophilic coating may reduce the incidence of spasm and reduce the difficulty in removing it from the radial artery under the situation of spasm artery spasm. After we compared the friction resistance between the sheath introducer with hydrophilic coating and that without coating (nine samples each) in vitro, the sheath introducers with and without hydrophilic coating were randomly used in 37 and 36 patients, respectively, who underwent elective TRI with a 6 Fr introducer sheath. Hydrophilic coating of sheath introducer reduced friction resistance by 70% (P < 0.00001) in in vitro model and facilitated sheath removal after finishing TRI (P = 0.0003). Hydrophilic coating of sheath introducer is useful in TRI.

The early clinical and angiographic outcome of sequential coronary artery bypass grafting with the off-pump technique

OBJECTIVE

The emergence of the off-pump coronary artery bypass technique has made surgeons consider combining it with other techniques developed and learned with conventional coronary artery bypass grafting with cardiopulmonary bypass. One of these techniques is the construction of a sequential graft to bypass more than one coronary vessel. The purpose of this study is to review the outcome of combining sequential coronary artery bypass grafting with off-pump techniques.

METHODS

We retrospectively reviewed the records of 45 consecutive patients who underwent isolated coronary bypass surgery with off-pump and sequential grafting techniques at Harefield Hospital (Harefield, UK) between July 1999 and December 2000. The registry database, medical notes and charts were studied for preoperative and postoperative data of the patients. Ten patients consented and underwent early postoperative angiography to check the quality of the grafts and anastomoses.

RESULTS

There were no deaths among the study patients. Morbidity consisted of atrial fibrillation in 6 patients (13.3%), leg wound infection in 2 patients (4.4%), and pleural effusion in 1 patient (2.2%). Early angiography of the 10 consenting patients revealed 10 patent sequential grafts (100%) with 20 satisfactory end-to-side and side-to-side anastomoses (100%).

CONCLUSION

The combination of sequential grafting and off-pump techniques is feasible, is safe, and provides good early clinical and angiographic outcomes.

Brief pretreatment of radial artery conduits with phenoxybenzamine prevents vasoconstriction long term

BACKGROUND

Radial artery bypass conduits are prone to early vasospasm or "string sign" with use of vasopressor therapy intraoperatively and postoperatively, causing increased resistance in coronary artery grafts. Current intraoperative treatment with papaverine fails to provide sustained inhibition of vasoconstriction. We tested the hypothesis that a 30-minute pretreatment of radial artery segments with the alpha-adrenergic antagonist phenoxybenzamine (PB) or the putative protein phosphatase 2,3-butadione monoxime (BDM) attenuates vasoconstriction induced by the vasopressors phenylephrine or norepinephrine for as long as 48 hours compared with papaverine.

METHODS

Canine radial arteries were harvested, incubated in control buffer or solutions of papaverine 10(-6) M, BDM 10(-6) M or phenoxybenzamine 10(-6) M for 30 minutes, washed, and stored in drug-free culture medium for 2, 24, or 48 hours. After storage, constriction was induced by norepinephrine at incremental concentrations ranging from 0.7 to 3.5 micromol/L or by phenylephrine (0.300 to 1.5 micromol/L) with or without the inhibitors, and the degree of vasoconstriction was quantified in organ chambers. Responses to norepinephrine or phenylephrine were compared to constriction with receptor-independent potassium chloride KC1 (30 mmol/L).

RESULTS

Maximum responses to phenylephrine and norepinephrine were comparable at 2, 24, and 48 hours after harvest in the control group (phenylephrine: 67% +/- 4%, 62% +/- 6%, 65% +/- 6% of KC1 response; norepinephrine: 75% +/- 4%, 62% +/- 1%, 58% +/- 7%, respectively). Papaverine failed to attenuate constriction to phenylephrine and norepinephrine 2, 24, or 48 hours posttreatment. Pretreatment with BDM did not reduce vasoconstriction responses to phenylephrine or norepinephrine 2 hours after incubation but did reduce constriction responses thereafter. In contrast, phenoxybenzamine completely attenuated constriction to both phenylephrine (19% +/- 8%, 1% +/- 4%, -12% +/- 4%) and norepinephrine (7.1% +/- 1%, -5% +/- 5%, -20% +/- 5%) at 2, 24, and 48 hours posttreatment, respectively. Phenoxybenzamine did not alter endothelial function relative to controls at any time point.

CONCLUSIONS

Thirty-minute pretreatment of RA conduits with 10(-6) M phenoxybenzamine completely inhibits vasoconstriction to phenylephrine and norepinephrine for as long as 48 hours. Soaking radial artery grafts briefly in phenoxybenzamine solution before implantation may be effective in preventing postoperative vasospasm caused by two common alpha-adrenergic agonists used in postoperative hemodynamic management.