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Biomedical subjects

U Brenken

Publications and source records attributed to U Brenken.

At least 19 recordsLinked to original sources
PubMed1994

Alternative perioperative anticoagulation monitoring during cardiopulmonary bypass in aprotinin-treated patients.

Monitoring of anticoagulation during cardiopulmonary bypass by means of the activated coagulation time (ACT) has become questionable due to the prolongation in the clotting time of patients receiving aprotinin. Because the celite-based ACT only indicates intrinsic coagulation, and sufficient anticoagulation is needed to also prevent extrinsic coagulation, the ACT may not be reliable. Three different clotting times, the celite-based ACT, the kaolin-based activated coagulation time (AKT) and the high-dose thrombin time (HITT), were compared in a prospective, double-blind, placebo-controlled study of 20 patients who were to undergo cardiopulmonary bypass. As expected, neither the kaolin-based assay nor the high-dose thrombin time was influenced by aprotinin, whereas the celite-based ACT was significantly prolonged in aprotinin-treated patients as compared to control patients (P < 0.05). This study confirms that both kaolin-based and thrombin-based tests provide a reliable means of determining the degree of heparinization in the presence of aprotinin during cardiopulmonary bypass.

Aprotinin↗
PubMed1991

Postbypass hypothermia and its relationship to the energy balance of cardiopulmonary bypass.

Using a newly developed computerized intraoperative data acquisition system, the apparent adequacy of rewarming and its relation to the energy exchange between the patient and the bypass system was investigated. Retrospective analysis of comparable patients identified two groups that had, at the end of surgery, either a nasopharyngeal temperature (NPT) of 36 degrees C or more ("warm" group, n = 19), or a NPT of 35 degrees C or less ("cold" group, n = 19). Temperatures from the nasopharynx, thenar eminence skin, and bypass pump arterial and venous lines were continually recorded and sent to the computer data base together with the pump flow rate. There were no significant differences between the groups regarding time on perfusion, time taken to cool, time of hypothermia, or the time interval from end of perfusion to the end of surgery. However, rewarming time was greater in the warm group (P less than 0.01). The cold group were subjected to more profound hypothermia (P less than 0.001), and had lower NPTs and skin temperatures at the end of bypass (P less than 0.0001 and P less than 0.01, respectively). However, the difference between NPT and thenar skin temperature in each group at either the end of bypass or the end of surgery was the same. The net energy exchange between patient and pump was significantly different (mean in warm, 130 kJ [SD = 530]; in cold, -389 kJ [SD = 427]; P less than 0.003). In conclusion, the adequacy of rewarming can be expressed in terms of the energy exchanged in the bypass system, and cannot be assessed by the nasopharynx:skin temperature gradient.

Anesthesia, Intravenous↗
PubMed1988

Clinical effect of Bretschneider-HTK and St. Thomas cardioplegia on hemodynamic performance after bypass measured using an automatic datalogging database system.

A prospective consecutive study was undertaken to compare the hemodynamic effect of two cardioplegic solutions in CABG patients after bypass, and in relation to aorta occlusion time with the support of a automatic datalogging database. A total of 249 patients were randomized. One group received Bretschneider cardioplegic HTK solution (132 patients, group I) the other group received St. Thomas cardioplegic solution (117 patients, group II). The data was divided in four periods of aortic clamp time: less than or equal to 40 min (group I 26 patients, group II 32 patients); 41-60 min (group I 49 patients, group II 47 patients); 61-80 min (group I 30 patients, group II 29 patients); and greater than 80 minutes (group I 27 pts, group II 9 patients). Anesthesia regime and therapeutic drugs and infusions were given in both groups in similar dosages. Within both groups HR, CO, PAP, PCWP increased after bypass in relation to prebypass values. SVR decreased in both groups by 30%, MAP and PVR decreased only in group I. Between group I and II differences were found in the CI (3.0 vs. 3.3 l/min/m2), MAP (70 vs. 76 mmHg), PMAR (18 vs. 16 mHg), and SVR (827 vs. 954 dyn.sec.cm-5). In significantly more of the patients in group I, sinus rhythm started spontaneously after the release of the aorta clamp (39.5% vs. 20.4%, p less than 0.005). Patients in group I needed temporarily a pacemaker after bypass in 6.3% cases (in 1.1% of patients in group II,). There was no relation of the hemodynamic data in relation to aorta occlusion time within the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Bicarbonates↗
PubMed1988

[Experiences with an anesthesia protocol written by computer].

Since December 1983, we have used a computer system for charting and data logging in cardiac and thoracic anesthesia. These computers, designed as stand-alone units, were developed at our hospital based on Motorola 6809 microprocessor systems. All measurements derived from anesthetic monitoring, ventilator, and heart-lung machine are automatically sampled at regular intervals and stored for later data management. Laboratory results are automatically received from the hospital computer system. The user communicates with the system via a terminal and a keyboard; this also facilitates the entering of all comments, medications, infusions, and fluid losses. All data are continuously displayed on an A3 format anesthetic chart using a multi-pen, flat-bed plotter. The operation of the system has proved to be simple and needs less time than charting by hand, while the result, the display on the chart, is far clearer and more complete than any handwritten document. Up to now 3,200 operations (corresponding to 12,500 anesthetic h) have been documented. The failure rate of the system, defined as an interruption of the documentation for more than 30 min is 2.1%. Further development of the system is discussed. A data base for processing the stored data has been developed and is being tested at present.

Anesthesia, General↗
PubMed1986

Clinical comparison between four modern membrane oxygenators: Bentley CM 40/50, COBE CML, Sci Med 3500-2A and Travenol LPM 50.

The devices with flat polypropylene membranes can be primed simpler and faster, than devices with the capillary membranes or with silicone rubber membranes. These two devices also offer more protection against venous air admixture and leaking of bubbles across the membrane. From hematologic standpoint there was no clear advantage of one particular device over another.

Carbon Dioxide↗
PubMed1983

The effect of prostaglandin E1 in patients undergoing clinical cardiopulmonary bypass.

The effect of prostaglandin E1 (PGE1) on protection of platelets during cardiopulmonary bypass (CPB) was evaluated in 9 patients, who were compared with an identical control group of 10 patients undergoing coronary artery bypass grafting. To evaluate the hemodynamic side-effects, PGE1 (0.05 micrograms/kg/min) was infused prior to CPB, resulting in a 26% drop in mean systemic arterial pressure. With this dose, no inhibition of the adenosine diphosphate-induced aggregation could be measured in the pulmonary artery sample. During CPB, the same infusion dose resulted in a severe drop in systemic arterial pressure below 50 mm Hg in 7 of the 9 patients. In 5 of these patients, volume load and phenylephrine infusion could not compensate for the pressure drop, and PGE1 had to be reduced to 0.02 micrograms/kg/min. Platelet aggregation was reduced significantly in the PGE1-treated group compared with the control group, but not completely inhibited during CPB. However, in the postbypass period no platelet preservation was seen in the PGE1 group. In both groups, platelet number and function were equally low. No differences were measured in blood loss or blood transfusion requirements. Except for hypotension, no side-effects of the PGE1 treatment were seen. It is concluded that the hypotension caused by minimal doses of PGE1 during CPB precluded using higher doses, which might have had a greater effect on platelet inhibition. These hypotensive side-effects should be reduced or eliminated before PGE1 can be expected to have the same protective effect on platelet damage that has been demonstrated in animal experiments.

Alprostadil↗
PubMed1983

Two membrane oxygenators and a bubbler: a clinical comparison.

We compared the hemocompatibility of the Polystan bubble oxygenator and the Travenol TMO and SciMed spiral-coil membrane oxygenators in 43 patients undergoing aortic valve replacement. In a subgroup of 27 patients, we collected hematological data and correlated platelet behavior with hemostasis. We found no differences in blood loss or blood (product) requirements among the groups. Platelet and erythrocyte damage was less in the membrane oxygenator groups than in the bubble oxygenator group. Differences in adenosine diphosphate-induced platelet aggregation were equivalent. Drops in this function concurred with intensified cardiotomy suction and administration of protamine. Leukocytosis after bypass was most marked in the SciMed group. Duration of bypass correlated with blood loss and blood requirements in the operating theater. Platelet counts shortly after bypass correlated negatively with duration of bypass and blood loss in the intensive care unit. Platelet function correlated with none of the factors just mentioned. We conclude that platelets and erythrocytes are preserved better by the membrane oxygenator than by the bubbler. The TMO system causes more erythrocyte damage than the SciMed oxygenator, probably due to TMO's dual-pump system. Clinical evidence for these improvements was not found, and this will be possible only when the other factors responsible for blood damage can be controlled.

Adult↗
PubMed1982

Successful management of cor triatriatum associated with anomalous pulmonary/systemic venous connection in an infant.

Diagnosis and successful surgical repair of cor triatriatum, associated with anomalous pulmonary/systemic venous connection in a 6-month-old infant, is described. Follow-up at 2 years revealed no abnormalities. The clinical findings, hemodynamics, and surgical treatment are discussed, together with a review of the literature. This is a rare, life-threatening situation presenting significant diagnostic difficulties in infancy. It is, however, amenable to surgery provided that an early diagnosis is achieved.

Arteriovenous Malformations↗
PubMed1982

Is prevention of hypertension after open heart surgery possible by blocking 5HT2-receptors with ketanserin?

Eleven patients undergoing coronary or aortic valve surgery received ketanserin (3 X 10 mg i.v.). When surgery was finished hemodynamic measurements were performed prior to and after cessation of nitrous oxide. The results were compared with those of a control group (n = 30), reported in a previous study. At the end of operation the ketanserin treated patients had significantly lower heart rate (84 +/- 16 vs. 96 +/- 14 min-1; Mean +/- S.D.), lower mean arterial pressure (75 +/- 12 vs. 84 +/- 10 mmHg) and higher skin temperature (31.9 +/- 1.3 vs. 27.7 +/- 2.3 degrees C). However, postoperative hypertension after the withdrawal of nitrous oxide was not prevented: similarly as in the control group blood pressure rose and systemic vascular resistance increased. As the last dose of ketanserin was given 60 minutes before the end of anesthesia it is likely that the effect of ketanserin had already worn off.

Adult↗
PubMed1982

Clinical study of blood trauma during perfusion with membrane and bubble oxygenators.

This clinical study was designed to show differences in hemostasis after perfusion with membrane (MO) or bubble (BO) oxygenators in cardiopulmonary bypass. These differences, however, may be obscured by other damaging factors, such as cardiotomy suction, various perfusion durations, or different types of operations. Therefore, only patients undergoing coronary artery bypass grafting were studied. During such operations, rather equal perfusion durations can be expected and mainly apex vent suction is used. Data on postoperative blood loss and transfusions were collected from two groups: one comprising 49 patients perfused with the Travenol TMO membrane oxygenator (MO group) and the other composed of 25 patients with the Polystan VT 5000 bubble oxygenator (BO group). In 10 patients of each group, blood samples were taken at frequent intervals for blood cell counts, for the determination of platelet function, hematocrit, hemoglobin, and plasma hemoglobin, for several coagulation tests, and for the assessment of kidney and liver function. Significant differences between the two groups were found for postoperative blood loss and transfusions, both higher in the BO group. Platelet function was better maintained in the MO group until the moment of releasing the aortic cross-clamp, after which it decreased concurrently with a doubling of the amount of suction. After protamine administration, an additional drop of platelet function occurred and there was virtually no platelet function left in either groups; however, it recovered 90 minutes after bypass, mainly in the MO group. This study shows that hemostasis is better preserved with MO perfusion. Still further improvements may be achieved by preventing the damage of suction and by a correct protamine dose.

Blood Cell Count↗
PubMed1982

Etomidate-analgesic combinations for the induction of anaesthesia in cardiac patients. Part I: Studies in patients with coronary artery disease.

UNLABELLED: In a total of 150 patients undergoing coronary revascularization procedures etomidate was given for the induction of anaesthesia using 12 different dosages and combinations with piritramide, morphine, fentanyl and nitrous oxide. The aim of this study was to establish a method which would result in the smallest possible changes in arterial blood pressure and heart rate during the whole of the induction period, including the stressful phase of endotracheal intubation. In 68 patients cardiac output and pulmonary artery pressure were also measured. RESULTS: 1. In general, more favourable results were obtained when anaesthetic drugs were administered extremely slowly (e.g. by infusion) and according to a standardized dosetime regime. Conversely, the commonly used method - slow incremental injections according to the estimated requirements of the individual patient - led to much greater variations of arterial pressure, especially when fentanyl was combined with etomidate. 2. Combinations of etomidate and morphine led to unsatisfactory results. Dependent on the dose given, hypertension or hypotension were commonly seen. When piritramide was substituted for morphine much more stable haemodynamic conditions were obtained. 3. Surveying our investigations to find the most suitable dose relationship between the hypnotic, etomidate, and the opioid analgesic, piritramide, only small and negligible differences were found: comparing two procedures for the induction of anaesthesia using either high dose piritramide (3 mg . kg-1 given over 10 min), supplemented by low dose etomidate (0.1 mg . kg-1 given over the first 2 min) or an etomidate infusion (50 gamma . kg-1 . min-1) supplemented by a low dose piritramide (0.3 mg . kg-1 given over 1 min) excellent results were found in both groups. 4. In contrast, studies aimed at achieving equally favourable results using the combination of etomidate-fentanyl suggested that the safe dose-range of fentanyl is very narrow: etomidate-infusion (50 gamma . kg-1 . min-1) together with fentanyl 3 gamma . kg-1 led to unacceptable rises in blood pressure and heart rate after intubation, and the larger dose of 6 gamma . kg-1 fentanyl frequently led to hypotension.

Analgesics↗
PubMed1981

Hemodynamic side effects of prostaglandin E1 in patients before and during cardiopulmonary bypass.

Animal experiments have shown that the administration of prostaglandin E1 (PGE1) during cardiopulmonary bypass (CPB) reduces platelet damage and the tendency to bleeding disorders. Because PGE1 also has a strong vasodilating action, a clinical trial was started to evaluate its hemodynamic side-effects. PGE1 was studied during 3 different periods: 1. a 10-minute period before bypass, 2. a hemodynamically stable period during CPB, 3. during the whole period of CPB. 1. Before CPB, a consistent fall of mean arterial pressure (MAP) was observed (26 mmHg). 2. During the stable period of CPB, the blood pressure fall was dependent on the pre-existing systemic vascular resistance. 3. PGE1 infusion during the whole CPB period was, in general, badly tolerated. Increased perfusion flow was not sufficient to compensate for the resulting blood pressure drop. In most of the 13 cases vasopressors had to be given continuously. In 7 patients PGE1 had to be reduced, and in 4 patients the infusion had to be stopped altogether. Because of the marked vasodilator effects of PGE1 it appears impossible to give patients doses adequate to achieve platelet preservation during clinical CPB with safety.

Adult↗
PubMed1980

Termination of anaesthesia--do we pay enough attention to its consequences? Haemodynamic studies following the use of piritramide, flunitrazepam and nitrous oxide anaesthesia for open heart surgery.

After completion of coronary or valve replacement surgery the haemodynamic changes due to cessation of nitrous oxide were measured. Seventy-four patients received piritramide-nitrous oxide anaesthesia. In 20 patients nitrous oxide was continued after operation and no marked haemodynamic changes occurred. However, when nitrous oxide was discontinued immediately after the operation (n=30) a significant rise in systolic arterial pressure (108+/-15 to 153+/-30 mm Hg), systolic pulmonary artery pressure (35+/-9 to 40+/-16 mm Hg), systemic vascular resistance (111 +/-26 to 148+/-44 MN.s.m-5) and rate pressure product (9,600+/-1,600 to 14,300+/-4,000) occurred. Heart rate (89+/-11 min-1), left artrial pressure (13+/---4 mm Hg) CO2 minute production (125+/-19 ml. min-1.m-2) and cardiac index (2.5+/-0.61.min-1.m-2) rose only moderately. When additional flunisternal closure to 24 patients, marked haemodynamic changes were still noted after N2O withdrawal, even though anaesthesia was prolonged. The sudden rise of arterial pressure and vascular resistance implies risks to patients with myoicardial or coronary insufficiency, therefore close monitoring is necessary, when nitrous oxide has to be stopped, to enable undelayed antihypertensive therapy.

Adult↗