An Experimental Hemodynamic Study of the Pelvic Collateral Circulation

Iliac arteries were occluded in adult mongrel dogs to investigate pelvic hemodynamics. When the unilateral common iliac artery was occluded, the blood flow making a &#34;stopover&#34; within the pelvis was found to be significantly less than that of anatomical hemodynamics even under a resting condition. The blood flow decreased more significantly under exercise loading than under a resting condition, which demonstrates the presence of the &#34;steal&#34; phenomenon. This only occurs in the collateral circulation in the pelvis formed by two arterial systems which are related in a series. In deciding the appropriacy of reconstruction for the internal iliac artery in patients with aorto-iliac occlusive disease, this &#34;steal&#34; phenomenon should be kept in mind. In most cases, ischemic symptoms in pelvic organs may be due to a simple decrease of the blood flow supplied to the pelvis, or due to the &#34;steal&#34; phenomenon. If the pelvic region is in the state of ischemia owing to the &#34;steal&#34; phenomenon, reconstruction of the blood vessels flowing into the pelvis is not required.</p

Spinal epidural oxygen partial pressure and evoked spinal cord potential in relation to the severity of spinal ischemia during cross-clamping of the thoracic aorta.

Experiments were undertaken to determine the relationship between evoked spinal cord potential (ESP) and the partial pressure of oxygen in tissue in the epidural space (E-pO2) during aortic clamping. Eighteen adult mongrel dogs were studied as follows. In group I (n = 6), the descending thoracic aorta was clamped partially at the proximal site for 15 min to maintain the distal arterial pressure at 60, 40, and 20 mmHg consecutively at 15 min intervals. In group II (n = 6), the descending thoracic aorta was clamped proximally for 30 min. In group III (n = 6), the descending thoracic aorta was cross-clamped at proximal and distal sites for 30 min. Postoperative complete paraplegia was observed in 4 of 6 dogs in group III, but none in group II. The change in ESP with aorta cross-clamping was very mild in groups I and II. Transient increases and decreases in the ESP amplitude were observed in group III. The decrease of E-pO2 correlated well with the distal arterial pressure, and a rapid return to baseline of the E-pO2 was observed after declamping. The E-pO2 changed in response to spinal ischemia more rapidly than did ESP in all groups. The critical level of E-pO2 was 50 mmHg or a 40% decrease from baseline. Because the ESP reflects spinal function and the E-pO2 reflects spinal blood pressure, we propose that combined recording of ESP and E-pO2 would improve spinal monitoring during thoracic aortic surgery.</p

Cellular immunocompetence in aortitis syndrome.

Cellular immunocompetence was investigated in 17 cases of aortitis syndrome (3 active, 14 inactive stage). Both the active and inactive groups demonstrated significantly lower interleukin-2 (IL-2) production than healthy volunteers. The active aortitis syndrome group produced significantly more interleukin-1 beta (IL-1 beta) than the inactive group. The proportion of CD11b+ CD8+ cells was significantly lower in the active aortitis syndrome group. Further, the proportions of CD11b- CD8+ cells and CD57+ CD16- cells in the aortitis syndrome patients were significantly higher than the healthy volunteers. These results suggest that there are intrinsic qualitative abnormalities in the T cells that produce IL-2 in aortitis syndrome. Pathogenesis of aortitis syndrome is considered as follows: during the active stage, diminished IL-2 production impairs differentiation and proliferation of suppressor T cells, thus creating abnormalities in the inhibitory functions of immunoregulation and promoting the proliferation of cytotoxic T and natural killer (NK) cells. This presumably initiates inflammation of the aorta and/or artery.</p

Correlation between the Layer of an Intimal Tear and the Progression of Aortic Dissection

Thoracic aortas isolated from dogs were evaluated to determine the correlation between the depth of an intimal tear and the progression of aortic dissection. Thoracic aortas obtained from 99 adult mongrel dogs were used. An intimal tear (aortic pocket) was created on the aortic wall and the aorta was connected in series to a closed circuit (150 mmHg/100 mmHg and 60 beats/min). The progression of the dissection was most notable in the aortic pocket prepared in the first one-third of the external media (87.5%). There was no correlation however between the width of the pocket and the progression of dissection. Examinations of samples from surgical patients have shown that dissection usually progresses at the same site. This has been attributed to the diseased media. Our results demonstrated that dissection occurred almost always at the same site without any medial changes suggesting that whether dissection develops or not likely depends upon whether the intimal tear reaches the first one-third of the external media or not

The evaluation of asymptomatic arterial occlusive disease of the legs using an exercise test.

The Doppler-derived ankle pressure index (API) is a useful indicator of the necessity for peripheral vascular reconstruction of the lower extremities. But the API at rest dose not reflect the functional capacity of leg circulation, especially in the early stage of disease. Therefore, an asymptomatic but hemodynamically significant lesion in one leg is sometimes missed by pressure measurement at rest when there is a severe lesion with symptoms in the other leg. In this study, the API not only at rest but also after exercise was measured in twenty normal subjects and thirty-two patients with angiographically proven arteriosclerosis obliterans. About 60% of the patients had unilateral symptoms, although they had significant disease bilaterally. The API after exercise proved to be more sensitive than the API at rest and may be useful in assessing asymptomatic legs of such patients and determining their surgical indication.</p

Intrathecal oxygen concentration as a new indicator of spinal cord ischemia

A number of approaches have been put forward to monitor spinal cord ischemia during thoracic and thoracoabdominal aortic occlusion. However, none of these can ultimately prevent devastating complications which result from ischemic spinal cord injury. A direct measurement of the oxygen content of the spinal cord may accurately indicate the perfusion state, but in practice it is impractical. We surmised that intrathecal and/ or epidural oxygen concentration(I-pO2 and E-pO2, respectively) accurately reflect oxygen content in the spinal cord. So, we examined whether or not I-pO2 and/or E-pO2 correlated with the spinal cord pO2 (S-pO2) in dogs. In nine mongrel dogs, a model of graded spinal cord ischemia was developed by stepwise alternation of the level of aortic occlusion with an intraaortic balloon catheter. I-pO2, E-pO2 and S-pO2 were measured with a mass spectrometer. Our results show that, both I-pO2 and E-pO2 significantly correlated with S-pO2. I-pO2 correlated with S-pO2 better than E-pO2 did. Therefore, I-pO2 can be used as a new indicator for spinal cord ischemia, and I-pO2 monitoring would be useful to prevent paraplegia associated with thoracic aortic surgery.</p

Acute Effect of Aliskiren on Smoking-Induced Endothelial Dysfunction in Smoker

Background: We aimed to examine the acute effect of aliskiren on smoking-induced endothelial dysfunction in smoker.Methods: Nineteen male smokers were enrolled. After all participants smoked a cigarette, their endothelial function was assessed with brachial artery flow mediated dilation (FMD). An hour after the administration of aliskiren, they smoked again, their FMD was assessed again. A month later, all measurements were performed again without the administration of aliskiren as a control. Blood pressure, plasma renin activity, and serum interleukin-6 concentration were also examined at the same time of FMD measurement.Results: A cigarette smoking led to an acute endothelial dysfunction (6.5 ± 1.7% to 3.4 ± 1.0 %, P = 0.02). Aliskiren administration significantly suppressed blood pressure and plasma renin activity, furthermore, improved FMD (6.7 ± 0.5% to 8.1 ± 0.8 %, P = 0.03). Aliskiren significantly reduced serum interleukin-6 concentration, but not in control.Conclusion: Aliskiren has a beneficial effect on smoking-induced acute endothelial dysfunction.</p