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Biomedical subjects

K Iwatsuki

Publications and source records attributed to K Iwatsuki.

At least 253 records · Page 14Linked to original sources
PubMed1977

Autoregulation of renal blood flow during ether, halothane and methoxyflurane anesthesia in dogs.

The effects of ether, halothane and methoxyflurane (0.5-1.5 MAC) on renal blood flow and its autoregulation were studied in 24 dogs. The left renal artery was perfused with the animals' own blood by a constant pressure perfusion system. The perfusion pressure ranged from 60 to 200 mmHg. Renal blood flow at the perfusion pressure of 100 mmHg was changed neither by ether nor by halothane, while it was decreased dose-dependently by methoxyflurane. At equipotent anesthetic concentrations the autoregulation of renal blood flow was only slightly impaired by ether, but significantly by halothane and methoxyflurane. Adenosine (100 mug/min) or calcium chloride (10 mg/min) which was infused directly into the renal artery resulted in a restoration of autoregulation impaired by MAC-1 of each anesthetic when perfusion pressure was raised stepwise from 100 to 200 mmHg, but no restoration was observed at low perfusion pressure below 100 mmHg. The results indicate that methoxyflurane exerts a direct constrictive effect on the renal vasculature. Adenosine and calcium may play a significant role on the response of the renal vasculature to raised perfusion pressure.

Adenosine↗
PubMed1976

Effects of pentazocine on coronary hemodynamics under pentobarbital or chloralose-urethane anesthesia in dogs.

The effect of pentazocine on the coronary hemodynamics was studied in anesthetized dogs. Under pentobarbital anesthesia pentazocine did not cause any significant changes in the coronary hemodynamics. Under chloralose-urethane anesthesia, however, it produced a statistically significant increase in heart rate, left coronary blood flow rate, myocardial oxygen consumption as well as myocardial oxygen extraction rate, but a decrease in coronary vascular resistance. These results indicate that the effects of pentazocine on the coronary hemodynamics are modified significantly by the drugs used for basal anesthesia.

Anesthesia, Intravenous↗
PubMed1976

Effects of combined use of droperidol with pentazocine and with fentanyl on pulmonary hemodynamics.

The effects of droperidol combined with pentazocine and with fentanyl on the pulmonary hemodynamics were investigated in intact dogs anesthetized with urethanechloralose, and the results were compared with those of each analgesic alone. Mean pulmonary arterial pressure and pulmonary driving pressure remained almost unchanged after droperidol and pentazocine. Pulmonary vascular resistance decreased significantly, and pulmonary vascular compliance and its radium tended to increase. These results indicate that droperidol counteracts the vasoconstrictive action of pentazocine on the pulmonary hemodynamics. On the contrary, almost all the parameters of the pulmonary hemodynamics after droperidol and fentanyl changed to similar directions to those after fentanyl alone. Droperidol seemed not to modify but to exaggerate the pulmonary circulatory effects of fentanyl.

Animals↗
PubMed1976

Effects of change in concentration of calcium on myocardial contractility depressed by thiamylal and halothane.

The effects of change in the concentration of Ca++ on myocardial contractility depressed by thiamylal and halothane were studied in isolated dog heart muscle. The concentration of Ca++ in the bathing medium was increased stepwise from 1.9 to 20.9 mM. An increase in Ca++ concentration resulted in an increase both in net-shortening (delta1) and in maximum velocity of shortening at 0.4 g preload (V'max) which reached the maximum values at 11.4mM of Ca++. A further increase in Ca++ concentration rather decreased delta1 and V'max. The concentration-response relation curves in the presence of thiamylal (3.3 mg%) shifted to the right almost parallel to the control curve, with the peaks at 15.2 mM of Ca++. The result indicates that the depression of myocardial contractility produced by thiamylal is counteracted competitively by Ca++. However, the curves in the presence of halothane (5.0 +/- 0.4 mg%) were kept lower than those of the control, with the peaks at 7.6 mM of Ca++. The result shows that the counteraction of Ca++ to the depression of myocardial contractility was limited in the presence of halothane. A similar tendency was observed in maximum force of isometric contraction (Fm). Moreover, in the presence of halothane, the administration of higher concentrations of Ca++ almost always accompanied "after-contraction". From the result obtained and the literature concerned it was suggested that the mechanism for producing the depression of myocardial contractility might be different between thiamylal and halothane in relation to Ca++ movements at the Ca++ storage sites within the myocardium.

Animals↗
PubMed1976

Effect of dibutyryl cyclic AMP on neuromuscular transmission in myasthenia gravis.

The effect of dibutyryl 3',5'-cyclic monophosphate (D-cAMP) on the neuromuscular transmission was studied in a patient with myasthenia gravis during anesthesia. D-cAMP caused a slight increase in single twitch tension, and an initial transient decrease in tension which resulted from the trains of 2 Hz stimuli disappeared after D-cAMP. The finding of the present study suggests that D-cAMP has an anti-fatigue effect in patients with myasthenia gravis.

Adult↗
PubMed1976

[Treatment of spinal cord arteriovenous malformation by surgical excision combined with afferent vessel coagulation-report of a case (author's transl)].

A case of spinal cord arteriovenous malformation was reported, in whom serial selective spinal angiogram and pantopaque myelogram showed a successful demonstration of intramedullary nidus. A 25-year-old male was admitted with paraparesis, impotence, hypesthesia and hypalgesia in his legs in 1974. He was diagnosed to have a spinal cord arteriovenous malformation of so-called "glomus type" with intramedullary nidus by the selective spinal angiogram and pantopaque myelogram. The nidus was fed by the anterior spinal artery through the 8th intercostal artery, from which a major draining vein extended caudally, but there was also some cranial drainage. The arteriovenous malformation was treated by surgical excision combined with afferent vessels coagulation in order to prevent the rupture of the remaining intramedullary nidus. After operation the patient develop a transient analgesia and girdle pain at T9-10 level, but after 42 days he regained full muscle power in his legs and could run by himself, while sensory disturbance remained about the same as before surgery.

Adult↗