Experimental evaluation of respiratory assist and hemodynamic changes by veno-venous bypass

The veno-venous bypass (VVB) with a membrane lung is one of the effective procedures to provide respiratory assistance even in patients with a high mortality rate when assisted only with mechanical ventilation. The purpose of this experimental study was to reveal the efficacy of respiratory assistance and the hemodynamic changes by VVB in acute respiratory failure. VVB was carried out in 22 mongrel dogs with acute respiratory failure induced by intratracheal seawater infusion. The ventilation-perfusion ratio (V/Q) of a membrane lung was changed to 1.0, 2.0 and 3.0 for each of the bypass flow rates of 20%, 40%, 60% and 80% of pre-perfusion cardiac output. For each condition variables indicating blood gas status and hemodynamic parameters were measured. As the indicator evaluating the efficiency of CO2 removal by VVB, the index of VVBCO2R was used, indicating the blood CO2 tension differences between IVC and the pulmonary artery. Arterial oxygen saturation was increased with bypass flow rates greater than 60% compared with pre-VVB, but the change was not marked. VVB was considered to be inadequate as a method of oxygenation. Besides, oxygenation was not able to be controlled by changing V/Q. However, significant reduction of arterial CO2 tension (PaCO2) could be obtained even with a bypass flow rate of 20%. As the blood flow rate increased, PaCO2 was lowered. But no more significant reductions of PaCO2 were obtained even with the flow rate of 60% and 80%. VVBCO2R was increased by changing the bypass flow rate from 20% to 40%, while no further increases were observed even with changes from 40% to 60% and 80%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Low-pressure Pneumoperitoneum for Laparoscopic Surgery Using a Disposable,Flexible Abdominal Wall Retractor

Abstract: Since April 1991, we have studied 160 patients who had had a successful laparoscopic cholecystectomy. Nine patients who presented with chronic cholecystitis with severe local adhesion and who were also considered to require a longer operative time were selected as suitable candidates for this procedure. They were successfully treated under a zero- to four-mmHg low-pressured pneumoperitoneum procedure combined with total abdominal wall lifting using a disposable, flexible vinyl tube retractor. This method enabled exactly the same clear laparoscopic vision as is possible in the routinely-used high-pressure pneumoperitoneum even in the marginal portions of the abdominal cavity. Moreover, it facilitated early reinsufflation after the cauterization-produced smoke was exhausted, which minimized the operative time and reduced the surgeon's anxiety concerning the maintenance of a sufficiently airtight condition. We believe that this low-pressure pneumopeqitoneum procedure also benefits the poor-risk patient who has restricted cardiopulmonary function, especially during advanced laparoscopic surgery which requires a longer operative and anesthetic time.     

Analgesic dose-response relation in cervical epidural block

The relationship between the age and the spread of analgesia from different epidural anesthetic doses was examined by studying analgesic dose responses in cervical epidural analgesia. Two different anesthetic doses (5ml or 10ml) of 2% mepivacaine were injected into the cervical epidural space at a constant pressure (80mmHg) using an intravenous apparatus, and the spread of analgesia to pinprick was assessed. The significant correlation was found between the patients age and the number of spinal segments blocked (5ml:r = 0.8498, P < 0.01, 10ml:r = 0.5988, P < 0.01). The inverse linear relationship was found between the patients age and the segmental dose requirement (5ml:r = –0.6754, P < 0.01, 10ml:r = –0.5784, P < 0.01). Patients under 39 years of age showed a direct relationship between the dose injected and the number of spinal segments blocked, enabling prediction of the number of segments blocked with a given dose of local anesthetic. Doubling the epidural dose approximately doubled the number of spinal segments blocked. The analgesic dose-response relation in patients over 60 years of age differed from that in patients under 39 years of age and doubling the epidural dose did not double the number of spinal segments blocked. Progressively more extensive analgesia was obtained from a given dose of local anesthetic with advancing age. It was difficult to limit the extent of analgesia by injecting a smaller dose of local anaesthetic in the elderly.(Hirabayashi Y, Matsuda I, Inoue S et al.: Analgesic dose-response relation in cervical epidural block. J Anesth 2: 22–27, 1988)     

HLA phenotype in patients with osteosarcoma

Nineteen patients with typical osteosarcoma were studied for evidence of association with human leukocyte antigen (HLA) phenotypes. HLA-A11 was detected in nine of 19 patients (47.4%) compared with 16.9% of 235 controls (chi 2 " 10.861, p less than 0.001), which yielded an odds ratio of 4.523. The positive rate of HLA-A11 was significantly increased in the patients. Interestingly, five of seven patients with poor prognosis had HLA-A11, compared with two of nine disease-free patients, 18 months after the initial treatment. These data suggest that major histocompatibility complex (MHC)-linked genes determines susceptibility to the occurrence of osteosarcoma and its prognosis.     

Transient induction of single GST-P positive hepatocytes by DEN

The single cells positive for placental glutathione S-transferase(GST-P), detectable in livers of rats soon after treatment withhepatocarcinogens, are possible ‘initiated cells’,the hypothesis tested in the present series of experiments.No low dose threshold was observed in male Sprague-Dawley ratsat different single doses of diethylnitrosamine (DEM) althougha plateau was reached between 160 and 200 mg/kg body weight.At the latter single dose 12 400 positive cells/cm³ were observedimmunohistochemically in rat livers after one week, the numbersthen decreasing to week 8 and thereafter rising again. In thenumbers then decreasing to week 8 and thereafter rising again.In the early stages single cells predominated but with timea gradual increase in mini-foci and larger lesions became evident.Application of selection pressure (feeding of diet containing0.02% 2-AAF plus partial hepatectomy) to rats 2–24 weeksafter single DEN-treatment resulted in the formation of largefoci positive for GST-P, especially in the early stages, thegrowth response being less pronounced with time. The numberof foci, on the other hand. was correlated with the number offoci, on the other hand, was correlated with the number ofsingle cells/mini-foci detected inhepatectomy tissue of thesame individuals. These results suggest that the early GST-Ppositive populations could be the precursor for preneoplasticfoci and nodules.     

Diazepam reduces both arterial blood pressure and muscle sympathetic nerve activity in human

It is known that benzodiazepines have a hypotensive effect, but the mechanism has not been well elucidated yet. To clarify whether this effect is due to central or peripheral mechanism, we administered 5 mg of diazepam or saline intravenously to healthy volunteers and assessed the change in blood pressure, heart rate, muscle sympathetic nerve activity and heart rate variability. After diazepam administration, systolic and mean blood pressure decreased significantly. Muscle sympathetic nerve activity was also significantly reduced but heart rate did not change, whereas the variables of spectral analysis of heart rate variability did not show significant change. We concluded that the hypotensive effect of diazepam in human is mainly due to the central mechanism.     

Bruch''s membrane of the brachymorphic mouse

Bruch's membrane exists between the retinal pigment epithelium and the choriocapillary endothelium. Its structure is very complicated, having five sublayers containing basement membranes of retinal pigment epithelium and choriocapillary endothelium, outer and inner collagenous layers, and a central elastic layer. In the development of Bruch's membrane in normal mice, both basement membranes are created first. Secondarily, collagen fibers are accumulated in the space between these basement membranes and then form a collagenous layer. Finally, the elastic layer elaborated in the collagenous layer separates this into outer and inner collagenous layers. Brachymorphic mice have a disorder in the sulfation pathway, resulting in undersulfation. Consequently, in Bruch's membrane of brachymorphic mice, the expression of decorin, a small proteoglycan containing chondroitin sulfate and an indispensable component in collagen assembly, is at a very low level. It is clear that hypoplasia of the collagenous layer in Bruch's membrane of brachymorphic mice induces a disorder in the following formation of the elastic layer. These findings suggest that the formation of the collagenous layer, regulated with acidic glycoconjugates such as decorin, is important in the development of Bruch's membrane.