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Biomedical subjects

M Czerny

Publications and source records attributed to M Czerny.

45 records · Page 3Linked to original sources
PubMed1999

Blood flow in distal end-to-side anastomoses with PTFE and a venous patch: results of an in vitro flow visualisation study.

OBJECTIVES: non-physiological flow behaviour plays a significant role in the development of distal anastomotic intimal hyperplasia. To investigate flow patterns in four anastomotic types of femoral end-to-side distal bypass graft anastomoses, a flow visualisation study was performed. METHODS: transparent 1:1 casted replicas of distal vascular graft anastomoses created by conventional technique, Miller-cuff, Taylor- and Linton-patch were fabricated. A pulsatile mock circulation with a high-speed video system was constructed. Flow pattern was determined at mean Reynolds numbers 100-500. Migrations of the stagnation points on the bottom of the anastomoses at mean Reynolds numbers 100, 230, and 350 were measured. RESULTS: a vortex forms during early systole and increases to maximum systole in all anastomoses. During the diastolic phase the vortex moves in the Miller-cuff distally to the toe of the anastomosis and remains standing, while in the other anastomotic types the vortex moves proximally to the heal of the junction and breaks down. The shift of the stagnation point in the Miller-cuff was considerably smaller than in the other anastomoses. CONCLUSION: conventional, Linton and Taylor anastomoses show similar flow patterns. The Miller-cuff with its wider cavity shows lower shift of the bottom stagnation point, but a persistent washout of the anastomotic cavity, which may contribute to its reported good clinical performance.

Anastomosis, Surgical↗
PubMed1999

Systemic blood pressure and cerebral blood flow velocity during carotid surgery.

BACKGROUND: To evaluate the effect of mean arterial blood pressure (MAP) on cerebral perfusion during carotid surgery, we investigated blood flow velocity in the middle cerebral (Vs,mca) using transcranial Doppler ultrasonography (TCD). METHODS: During carotid crossclamping, treatment included either phenylephrine-induced hypertension without shunting (Group XC; n = 11) or insertion of a shunt (Group S; n = 12). RESULTS: Increasing MAP in Group XC before crossclamping (81 + /-13 mmHg to 107 +/- 12 mmHg) caused an increase of Vs,mca (59 +/- 17 cm/s to 75 +/- 20 cm/s; p < 0.001). During crossclamping without a shunt, Vs,mca was not dependent on MAP, and was reduced (mean 47 +/- 24 cm/s) in relation to preclamp values. In Group S, Vs,mca was always dependent on MAP and the preclamp velocity was maintained (before shunt: 75 +/- 26 cm/sec; during shunt: 79 +/- 30 cm/sec). CONCLUSIONS: Although we found an impaired cerebral autoregulation, Vs,mca was independent of MAP during carotid crossclamping. Thus, TCD measurements have to be interpreted with caution during crossclamping, and the effect of induced hypertension has to be confirmed with more invasive measures of cerebral blood flow.

Aged↗
PubMed1998

Monitoring of median nerve somatosensory evoked potentials in carotid surgery.

The purpose of this study was to compare median somatosensory evoked potentials (SEP) in patients undergoing carotid endarterectomy (CEA) with routine shunting and nonshunting (excluding the option of selective shunting) and to evaluate the significance of a decrease in the amplitude of the cortically generated waveforms of the SEP and/or an increase in the central conduction time (CCT) on the one hand, and that of a loss of the cortical SEP, on the other. Somatosensory evoked potentials were recorded in 32 patients before, during, and after CEA with routine shunting or nonshunting. The N13 and N20 latency, the CCT, and the N20/P25 amplitude were evaluated. In addition, a meta-analysis of 15 previous studies was performed comprising a total of 3,136 patients. The intraoperative cortical SEP showed no differences between shunted and nonshunted patients, apart from the preclamping value of the N20/P25 amplitude which was lower in the nonshunted subjects. The number of patients with decreased and/or delayed cortical SEP (findings frequently used as criterion for selective shunting) was similar in the two study groups. A loss of the cortical SEP occurred in one patient operated on without an indwelling shunt. None of these patients had a new neurologic deficit after surgery. In the meta-analysis, the positive predictive value of decreased and/or delayed cortical SEP was extremely poor, that of absent cortical SEP was poor to moderate and the prevalence of new neurologic deficits was similar in patients undergoing CEA with routine shunting-nonshunting and those with selective shunting-nonshunting. Our study suggests that decreased and/or delayed cortical SEP are unreliable predictors of the neurological outcome of CEA patients and consequently an unsuitable criterion for selective shunting. The meta-analysis confirms this finding and shows that the neurologic outcome is not improved by using an indwelling shunt selectively based on SEP monitoring.

Aged↗
PubMed1997

[Acute mesenteric ischemia].

UNLABELLED: Acute mesenteric ischemia is a life-threatening vascular emergency. A retrospective analysis of our patients was performed to describe the development of the various procedures of diagnostic assessment and treatment between 1970 and 1996, to show the influence on survival and to define recent standards. PATIENTS: Between 1970 and 1996, 145 patients, 75 male and 70 female, suffering from acute mesenteric ischemia, have been treated at the Department of Surgery-University Hospital Vienna. RESULTS: In most cases AMI was caused by arterial embolism (64.1%, n = 93) followed by arterial thrombosis (27.6%, n= 40). Venous thrombosis (3.5%, n = 5) and non-occlusive AMI (4.8%, n = 7) were rare events. Serum lactate level has been determined routinely in all patients having been admitted with acute abdomen since 1984 and turned out to be positive in 81.2% (mean value 9.81 (3.21-22.3) mmol/l). Abdominal x-ray gave only in some individual cases special hints to the advanced intestinal gangrene. Abdominal sonography led to the correct diagnostic assessment in 52 patients (= 35.8%). Angiography was in 92% conclusive for the diagnosis. Abdominal CT led to establish the correct diagnosis in > 80%. Our series with revascularisation (thrombectomy/embolectomy or bypass) has resulted in 73.8% patient survival with intestine having been maintained in the most favourable cases. CONCLUSIONS: Early diagnostic assessment and treatment are decisive for survival. Abdominal-CT, angiography and serum-lactate constitute quick and reliable means to provide diagnosis and to judge the stage of AMI in addition to meticulous examination of patients' history, symptoms and physical conditions.

Acute Disease↗
PubMed1977

[Acid-base balance during exchange transfusion (author's transl)].

During exchange transfusion with ACD blood severe metabolic acidosis may occur. ACD blood contains increasing amounts of acid which depends on the age of the blood. The mature newborn infant has different ways to compensate metabolic acidosis: the lungs, the immature kidneys and the conversion of citrate to bicarbonate. In preterm infants as well as in newborns with respiratory distress syndrome and mechanical ventilation the compensatory mechanisms may be reduced or even absent. Therefore ACD blood may lead to severe complications. To prevent acidosis adequate buffering with TRIS is recommended.

Acidosis, Respiratory↗
PubMed1975

[Pyridoxal phosphate and activity of pyridoxalkinase in serum of preterm and term infants (author's transl)].

Vitamin B6 nutriture was measured in 14 preterm infants (born between 30th and 35th week of gestation) by means of determination of pyridoxalphosphate and activity of pyridoxalkinase in serum on the 1st and 4th day of life. 11 term infants were included as control group. At the 1st day pyridoxalphosphate and activity of pyridoxalkinase in preterm infants were significantly decreased in comparison with the control group. 50% of preterm infants--all were delivered before the 33rd week of pregnancy--did not show any activity of pyridoxalkinase in serum. On the 4th day, vitamin B6 nutriture of preterm infants was still decreased in comparison with the control group. Measurable activity of pyridoxalkinase, however, was now found in all preterm infants. There was a positive correlation at the 1st and 4th day of life between pyridoxalphosphate and weight and activity of pyridoxalkinase and weight. According to our results pyridoxalkinase is an enzyme which depends on the gestational age of the newborn. After the 32nd week of gestation the enzyme becomes active. Moreover pyridoxalkinase is an enzyme that can be induced by formulas containing vitamin B6. We consider the administration of vitamin B6 to the preterm infant as necessary.

Gestational Age↗