Donald L. Akers

The value of aortic arch study in the evaluation of cerebrovascular insufficiency

In evaluation of extracranial carotid vascular disease, the use of arteriography has long been considered essential. With increasing expertise in noninvasive testing, the importance of extensive dye studies is being questioned. The data presented herein indicate that proper preangiographic evaluation of the patient population drastically reduces the possibility of missing significant intrathoracic pathologic processes. Two subsets of patients should be recommended routinely for dye studies: those patients with unequal upper-extremity blood pressures and those without pathologic neck findings on noninvasive testing to account for their symptoms. When these patients are recognized as having the potential for intrathoracic disease, dye studies can be performed in situations that will generate the highest yield. Even with the continued use of dye studies in evaluation of cerebrovascular insufficiency, elimination of the aortic arch study will drastically reduce the dye load and, thus, the associated morbidity.

Endothelial cell regrowth and morphology after balloon catheter injury of alloxan-induced diabetic rabbits

Neointimal thickening after catheter injury has been reported to be influenced by the integrity of the vascular endothelium. We have previously shown that neointimal thickening is significantly reduced in alloxan-induced diabetic New Zealand White rabbits after catheter injury compared with euglycemic rabbits. In the present study, it was hypothesized that endothelial cell regrowth, morphology, and endothelium-dependent vasoreactivity after catheter injury are improved in the diabetic rabbit (glucose ≥400 mg/dl) compared with the euglycemic rabbit. Two weeks after catheter injury, the percent endothelial regrowth was significantly increased in diabetic animals compared with euglycemic animals (32.1 ± 2 and 15.6 ± 1, respectively; P < 0.05). The endothelial cell morphology analyzed by scanning electron microscopy was also restored 2 wk after catheter injury in thoracic aortas from the diabetic animals compared with vessels from euglycemic animals. Endothelium-dependent relaxation to ACh in vessels from diabetic and euglycemic rabbits was attenuated 2 wk after injury, and, although improved by 4 and 8 wk, relaxation remained significantly depressed. These results suggest that endothelial cell regrowth and morphology in diabetic animals was improved compared with euglycemic animals; however, endothelium-dependent vasoreactivity remained impaired. Thus the attenuated neointimal thickening seen in the diabetic rabbit may be a function of the rate and degree of regrowth rather than the normalization of ACh-induced relaxation.Neointimal thickening after catheter injury has been reported to be influenced by the integrity of the vascular endothelium. We have previously shown that neointimal thickening is significantly reduced in alloxan-induced diabetic New Zealand White rabbits after catheter injury compared with euglycemic rabbits. In the present study, it was hypothesized that endothelial cell regrowth, morphology, and endothelium-dependent vasoreactivity after catheter injury are improved in the diabetic rabbit (glucose >/=400 mg/dl) compared with the euglycemic rabbit. Two weeks after catheter injury, the percent endothelial regrowth was significantly increased in diabetic animals compared with euglycemic animals (32.1 +/- 2 and 15.6 +/- 1, respectively; P < 0.05). The endothelial cell morphology analyzed by scanning electron microscopy was also restored 2 wk after catheter injury in thoracic aortas from the diabetic animals compared with vessels from euglycemic animals. Endothelium-dependent relaxation to ACh in vessels from diabetic and euglycemic rabbits was attenuated 2 wk after injury, and, although improved by 4 and 8 wk, relaxation remained significantly depressed. These results suggest that endothelial cell regrowth and morphology in diabetic animals was improved compared with euglycemic animals; however, endothelium-dependent vasoreactivity remained impaired. Thus the attenuated neointimal thickening seen in the diabetic rabbit may be a function of the rate and degree of regrowth rather than the normalization of ACh-induced relaxation.

Iliac vein compression syndrome: Case report and review of the literature

Iliac vein compression syndrome is a clinical condition that occurs as a result of compression of the left iliac vein between the right iliac artery and the fifth lumbar vertebrae. Patients usually have marked edema of the left leg. We report a case of a 16-year-old man who sought medical attention with significant left lower leg edema and four previous episodes of left leg cellulitis. Evaluation demonstrated venous hypertension as a result of left iliac vein compression. The patient underwent surgical correction; his symptoms resolved. Details and management of the case are presented and discussed. A review of the current literature regarding this condition also is included.

Safe Extracranial Vascular Evaluation and Surgery Without Preoperative Arteriography

Carotid surgery without preoperative arteriography was performed in 101 consecutive patients with an average age of 68.5 years and almost equal sex distribution. This prospective study analyzed risk factors, operative approach, bruits, indications for surgery, and outcome. All patients were studied by real-time B-mode ultrasound and spectral analysis and none were referred for arteriogram. The majority of patients had a standard carotid endarterectomy, and the findings at surgery correlated with noninvasive imaging. No mortality was recorded in this series of patients; a 1% rate of neurologic morbidity was noted. These results suggest that one can safely operate on the basis of a duplex scan. A preoperative arteriogram is not always necessary for carotid evaluation.

Concurrence of anaphylaxis and acute heparin-induced thrombocytopenia in a patient with heparin-induced antibodies

We report the occurrence of acute heparin-induced thrombocytopenia in a patient with anaphylaxis that began immediately after an intravenous bolus dose of unfractionated heparin. This case report is the first to document the concurrence of these 2 reactions to heparin. An abrupt fall in platelet count was documented immediately after the anaphylactic response. Study results for antibodies characteristic of heparin-induced thrombocytopenia were positive in 2 assays: serotonin release assay and heparin platelet factor 4 enzyme-linked immunosorbent assay. The patients antibody was exclusively immunoglobulin G. Any explanation for the relationship between the antibody response observed and the histamine release remains speculative.

Does intracranial dye study contribute to evaluation of carotid artery disease

One thousand consecutive cerebral arteriograms for suspected carotid artery disease were retrospectively evaluated for the intracranial disease component. Only 784 patients (78 percent) had arteriograms of the intracranial circulation. Forty-six patients (6 percent) had siphon stenosis in the range of 5 to 70 percent. No patient had a lesion encompassing more than 75 percent of the vessel diameter. Thirteen patients (2 percent) had intracranial aneurysms. All patients were asymptomatic from the standpoint of their aneurysms and none required surgical intervention. One additional patient was noted to have an intracranial tumor, which was confirmed by computerized tomography. In this patient population, intracranial dye study did not provide information that altered management.

Analysis of responses to human synthetic adrenomedullin and calcitonin gene-related peptides in the hindlimb vascular bed of the cat

Vasodilator responses to human adrenomedullin (hADM), a newly discovered hypotensive peptide, human calcitonin gene-related peptide-α (hCGRP-α) and hCGRP-β, which share structural homology with hADM, were compared in the hindlimb vascular bed of the cat under constant flow conditions. Injections of hADM (0.003–1 nmol), hCGRP-α, and hCGRP-β (0.003–0.3 nmol) into the perfusion circuit caused dose-related decreases in hindlimb perfusion pressure. Vasodilator responses to hCGRP-α and hCGRP-β were similar in potency and duration, and the doses of hCGRP-α and hCGRP-β required to reduce hindlimb perfusion pressure 40 mm Hg (ED40 mm Hg) were significantly lower than the ED40 mm Hg for hADM. The duration of the hindlimb vasodilator responses to hCGRP-α and hCGRP-β were significantly longer than the duration of the response to hADM. Amylin, a peptide that shares structural homology with ADM and with CGRP, had no significant effect on hindlimb perfusion pressure when injected in doses up to 1 nmol. Decreases in hindlimb perfusion pressure in response to hADM, hCGRP-α, and hCGRP-β were not altered by L-N5-(1-iminoethyl)-ornithine (L-NIO) in a dose of the nitric oxide synthase inhibitor that decreased the vasodilator response to acetylcholine or by the cyclooxygenase inhibitor, meclofenamate, in a dose that decreased the vasodilator response to archidonic acid. The present data demonstrate that hADM, hCGRP-α, and hCGRP-β have potent, but relatively short-lasting, vasodilator activity, and that vasodilator responses are not dependent on the release of nitric oxide or vasodilator prostaglandins in the hindlimb vascular bed of the cat. (Mol Cell Biochem 176: 5–11, 1997)

Transtracheal needle catheter ventilation in complete airway obstruction: An animal model

Transtracheal needle catheter ventilation (TNCV) may be used as an alternative airway when contraindications to endotracheal intubation exist. A feline model tested the efficacy of low-flow oxygen delivery, and initial data were gathered to define proper catheter calibers to effect adequate oxygenation and ventilation. Cats were anesthetized, trachea intubated, and ventilated for 30 minutes with a pressure-regulated ventilator. Arterial and venous pressures were monitored, and a chest tube was inserted to measure intrathoracic pressures. Arterial blood gas analysis was performed every five minutes during the baseline period. The endotracheal tube was then removed, the trachea cross-clamped, and TNCV instituted. Oxygen flow rates of 1, 3, and 5 L/min were varied with catheter sizes of 14, 16, and 18 g. Data demonstrated that TNCV provided adequate oxygenation and ventilation with flow rates of 3 and 5 L/min with the 14- and 16-g catheters. Satisfactory oxygenation could be obtained with these flow rates with the 18-g catheter, but ventilation was inadequate. Ventilation was unsatisfactory with the 1 L/min flow rate in all catheter sizes. These preliminary data indicate that a minimum catheter:trachea cross-sectional area ratio of 0.03 may be required to obtain oxygenation and ventilation with low-flow oxygen rates of 3 to 5 L/min in cats.

Pioglitazone Restores Endothelial Function in Patients with Type 2 Diabetes Treated with Insulin

The primary aim of this study was to evaluate the effect of pioglitazone on endothelial function, as assessed by flow-mediated dilatation (FMD) nitroglycerine-induced dilatation (NID) in patients with type 2 diabetes mellitus treated with insulin. A randomized double-blind placebo-controlled trial involved 20 patients with insulin-treated type 2 diabetes. Patients received either pioglitazone 30 mg or placebo for 4 months. FMD, NID, and HbA1c were measured before and after 4 months of treatment. HbA1c decreased from 10.0 (+/- 2.3) to 8.4 (+/- 2.0) in the pioglitazone group, a statistically significant improvement in glycemic control (p = 0.018). HbA1c was unchanged in the placebo group (p = 0.477). Endothelial function as assessed by FMD significantly improved from 10.1 (+/- 4.0)% to 14.6 (+/- 6.2)% in the pioglitazone group (p = 0.036) as compared to the placebo group (p = 0.705). There was a trend towards improvement in the NID in the pioglitazone group (from 13.3 +/- 8.0% to 18.9 +/- 5.4%; p = 0.056). In insulin-treated patients with type 2 diabetes, the addition of pioglitazone improves endothelial function, as measured by FMD. Addition of pioglitazone to insulin in type 2 diabetes patients may favorably impact vascular function in diabetes, even after many years of insulin resistance and hyperglycemia.

Effect of short-term treatment with a monoclonal antibody to P-selectin on balloon catheter-induced: Intimal hyperplasia, re-endothelialization, and attenuation of endothelial-dependent relaxation

The effects of an anti-P-selectin monoclonal antibody (MAb, PB1.3; Cytel Corporation) on neoendothelialization; neoendothelial function, as evidenced by acetylcholine-induced relaxation (nitric oxide formation); and intimal hyperplasia following embolectomy catheter-induced injury to the rabbit thoracic aorta were investigated. Catheter injury was induced in two groups of New Zealand White rabbits. One group received no treatment, while the second group received short-term treatment with the MAb (i.p., immediately before and 12 h after induction of catheter injury). A third group underwent a sham operation and served as uninjured controls. Following sacrifice at 2 weeks after injury, aortic rings were assessed for degree of intimal hyperplasia, neoendothelial morphology (scanning electron microscopy), and acetylcholine-induced relaxation. Aortic tissue from catheter-injured animals that received treatment exhibited improved neoendothelial morphology, as compared with tissue from untreated but catheterized animals; however, no statistically significant attenuation of the hyperplastic response or improvement in the attenuated neoendothelial-dependent acetylcholine-induced relaxant response that is characteristic of neoendothelium that forms after catheter denudation was observed. These data suggest that short-term attenuation of P-selectin-mediated polymorphonuclear leukocyte (PMN)/endothelium, PMN/platelet interactions, and/or thrombin formation beneficially affects neoendothelialization of the vascular wall following balloon catheter-induced injury.