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Biomedical subjects

M Karck

Publications and source records attributed to M Karck.

At least 37 records · Page 2Linked to original sources
PubMed1997

Ischemic preconditioning prior to myocardial protection with cold blood cardioplegia in coronary surgery.

OBJECTIVE: Encouraging results on myocardial preconditioning in experimental models of infarction, stunning or prolonged ischemia raise the question whether preconditioning techniques may enhance conventional cardioplegic protection used for routine coronary surgery. METHODS: A prospective clinical trial was conducted to investigate the effect of additional ischemic normothermic preconditioning prior to cardioplegic arrest applying cold blood cardioplegia in patients scheduled for routine coronary surgery (3 vessel disease, left ventricular ejection fraction > 50%). Two cross clamp periods of 5 min with the hearts beating in sinus rhythm were applied followed by 10 min of reperfusion, each (n = 7, group I). Inducing moderate hypothermia cold blood cardioplegia was delivered antegradely. In control groups, cold intermittent blood cardioplegia (n = 7, group II) was used alone. Coronary sinus effluents were analyzed for release of creatine kinase (CK), CK-MB, lactate, and troponin T at 1, 3, 6, 9, and 12 h. In addition, postoperative catecholamine requirements were monitored. RESULTS: The procedure was tolerated well, and no perioperative myocardial infarction in any of the groups studied occurred. Concentrations of lactate tended to be higher in group I, but this difference was not significant. In addition, no significant differences for concentrations of CK, CK-MB, and troponin T were found. Following ischemic preconditioning an increased dosage of dopamine was required within the first 12 h postoperatively (group I: 2.63 +/- 1.44 microg/kg/min, group II: 0.89 +/- 1.06 microg/kg/min). CONCLUSIONS: Combining ischemic preconditioning and cardioplegic protection with cold blood cardioplegia does not appear to ameliorate myocardial protection when compared to cardioplegic protection applying cold blood cardioplegia alone. Inversely, contractile function seemed to be impaired when applying this protocol of ischemic preconditioning.

Biomarkers↗
PubMed1996

Ischemic preconditioning enhances donor heart preservation.

Ischemic preconditioning has not been assessed in an experimental model for myocardial preservation during heart transplantation. Using isolated working rat hearts, ischemic preconditioning was investigated as an adjunct to isolated hypothermic (group 1), crystalloid (group 2: University of Wisconsin solution; group 3: St. Thomas' Hospital cardioplegic solution II; group 4: Bretschneiders' cardioplegic solution), and noncrystalloid (group 5: cold blood cardioplegia) preservation during a 10-hr period of global ischemia at 4 degrees C. After acquisition of functional baseline data, ischemic preconditioning was induced with one cycle of 5 min of normothermic ischemia and 5 min of reperfusion before induction of global hypothermic ischemia (n= 10/group). Nonpreconditioned hearts (n= 10/group) were assessed for control. Ischemic preconditioning improved postischemic: functional recovery. Thus, aortic flow after 60 min of reperfusion recovered to 0%, 8%, 0%, 1% and 0% in control groups 1 to 5 without ischemic preconditioning and 21%, 25%, 10%, 8%, and 3% in groups 1 to 5 with ischemic preconditioning. The same pattern of recovery was observed in regard to postischemic maximum developed left ventricular pressure, which recovered to 21%, 56%, 30%, 36%, and 19% in groups 1 to 5 without preconditioning and 46%, 75%, 49%, 40%, and 47% in the corresponding groups with ischemic preconditioning. High-energy phosphate contents were not significantly different between preconditioned hearts and corresponding nonpreconditioned control hearts. Creatine kinase leakage during early reperfusion was found to be reduced with ischemic preconditioning. Thus, we have demonstrated that ischemic preconditioning can improve contractile function after global hypothermic ischemia in the isolated rat heart and we have shown that this protection is additive to that of hypothermia-induced protection during global ischemia at 4 degrees C. This endogenous mechanism of cardioprotection was effective regardless of whether preservation was accomplished using cardioplegic solution or topical hypothermia alone. This may have clinical implications in myocardial preservation for heart transplantation.

Adenosine↗
PubMed1996

Adverse effects of crystalloid cardioplegia and slow cooling for protection of immature rat hearts.

BACKGROUND: Studies on the benefit of methods for protection of the hypertrophied immature myocardium are rare and controversial. METHODS: We assessed the effects of (1) rapid cooling by topical hypothermia alone, (2) slow prearrest cooling by coronary perfusion hypothermia, and (3) cardioplegic cardiac arrest with St. Thomas' Hospital solution no. 2 for protection of isolated immature rat hearts (age, 28 days) during 8 hours of global ischemia at 10 degrees C. Myocardial hypertrophy was induced noninvasively by lifelong feeding of a low iron diet. Recovery of left ventricular function, metabolism, and myocardial fine structure were assessed. RESULTS: In hypertrophied hearts, protection by topical hypothermia alone resulted in significantly improved postischemic recoveries of maximum left ventricular pressure and rate of pressure rise compared with the method of slow cooling or application of cardioplegia (40.6% +/- 5.0% and 38.1% +/- 5.9%, mean +/- standard error of the mean; p < 0.05). The same pattern of recovery was observed among nonhypertrophied control hearts. Regardless of the method of protection, hypertrophied hearts revealed a significantly larger interstitial space at the end of reperfusion than control hearts. In hypertrophied hearts, postischemic adenosine triphosphate concentrations were higher with topical hypothermia alone for protection than with the other methods. CONCLUSIONS: Rapid cooling by topical hypothermia alone provides superior protection of hypertrophied immature rat hearts as compared with slow prearrest cooling. Application of St. Thomas' Hospital cardioplegic solution no. 2 does not improve protection and even hinders postischemic functional recovery.

Adenosine Triphosphate↗
PubMed1996

Myocardial protection in chronic volume-overload hypertrophy of immature rat hearts.

OBJECTIVE: The benefit of cardioplegic cardiac arrest for protection of the immature myocardium is controversial. We therefore investigated the efficacy of (1) topical hypothermia alone (2) slow cooling by coronary perfusion hypothermia and (3) cardioplegic cardiac arrest plus topical cooling for protection of isolated immature rat hearts (age: 28 days). METHODS: The isolated perfused rat heart model was used. Hearts were subjected to 8 h of global ischemia at 10 degrees C. The study was conducted after clinically relevant conditions of volume-overload myocardial hypertrophy had been established non-invasively by lifelong feeding of a diet low in iron. Parameters of left ventricular function, endothelial function, the metabolic status and myocardial injury were measured. RESULTS: Topical hypothermia provided superior protection of hypertrophied hearts with recovery of maximum developed left ventricular pressure and rate of pressure rise at 41.2% +/- 22.3% and 34.5% +/- 20.7% (mean +/- standard deviation) of preischemic values (P < 0.05 versus slow cooling and versus cardioplegia plus topical hypothermia). The same pattern of recovery was observed among control hearts. The recovery of endothelial function following protection by topical hypothermia alone measured 55% +/- 41% in hypertrophied hearts and 62% +/- 37% in control hearts, but was not recordable in all other groups. In hypertrophied hearts post-ischemic myocardial high energy content was significantly improved with topical hypothermia alone for protection when compared to the other methods. Creatine kinase leakage during reperfusion did not differ significantly among the experimental groups. CONCLUSION: Rapid cooling by topical hypothermia along provides superior protection of hypertrophied- and non-hypertrophied-immature rat hearts to additional slow pre-arrest cooling. Use of St. Thomas' Hospital cardioplegic solution No.2 (STS 2) does not improve protection, and even hinders functional recovery in hypertrophied immature hearts. Endothelial injury caused by cold asanguinous perfusates, including cardioplegia, interferes with the recovery of vascular function, which in turn, may limit mechanical function.

Age Factors↗
PubMed1996

[Exogenous adenosine in cardioplegia].

The nucleoside adenosine is used clinically for the treatment of paroxysmal atrioventricular junctional tachycardia. Surgically oriented experimental studies indicate an improvement of myocardial protection when adenosine is administered as an adjunct to cardioplegic protection. This regards both postischemic functional recovery and the regeneration of myocardial energy-rich phosphates. However, as yet it remains to be determined which of the various effects of adenosine is truly protective. Likewise it is still unclear if the beneficial effects of "ischemic preconditioning" may be simulated by administration of adenosine. Current knowledge about this substance warrants careful evaluation of its protective capabilities in clinical studies during open-heart surgery.

Adenosine↗
PubMed1995

Protection of the chronic hypoxic immature rat heart during global ischemia.

The benefit of cardioplegic cardiac arrest for the protection of immature myocardium is controversial. We therefore investigated the efficacy of (1) topical hypothermia alone, (2) slow cooling by coronary perfusion hypothermia, and (3) cardioplegic cardiac arrest for the protection of isolated immature rats hearts (28 days) during 8 hours of global ischemia at 10 degrees C. The study was conducted in hearts from rats that were kept hypoxemic by lifelong exposure to simulated high altitude. Left ventricular function, endothelial function, the metabolic status, and the extent of myocardial injury were all assessed. Topical hypothermia provided superior protection in hypoxic hearts, with recovery of the maximum developed left ventricular pressure by 70.6% +/- 18.0% (mean +/- standard deviation) of its preischemic value (p < 0.01 versus slow cooling and versus cardioplegic protection). The same pattern of recovery was observed among control hearts. The degree of recovery of endothelial function after sole topical hypothermia measured 54% +/- 36% in hypoxic hearts and 62% +/- 37% in control hearts, but was not recordable in any of the other groups. Creatine kinase leakage and the myocardial high-energy content did not differ significantly among any of the groups. Rapid cooling by topical hypothermia alone provides superior protection in chronic hypoxic, immature rat hearts versus the protection conferred by slow cooling. St. Thomas' Hospital cardioplegic solution II does not afford additional protection. Endothelial injury caused by cold asanguineous perfusates, including cardioplegia, interferes with the recovery of vascular function, which, in turn, may limit mechanical function.

Adenosine Triphosphate↗
PubMed1995

[Prevention and therapy of prosthesis infections in the thoracic area].

Infections of vascular prostheses following replacement of the thoracic aorta remain a rare complication, fortunately. The incidence of prosthetic infection amounts to approximately 1.6%, however, there is only limited information from single center studies, and linearized actuarial data for more exact estimations are not available. Experience with prophylaxis and treatment of bacterial endocarditis as well as data available from peripheral vascular reconstruction nevertheless allow the development of treatment strategies concerning this complication. Experimentally, there is clear evidence that pretreatment of Dacron-grafts using the fibrin sealant-antibiotic compound results in a significant protection from infection, created by artificial contamination with staphylococcus aureus. This concept could clearly be confirmed in clinical series involving treatment of prosthetic valve endocarditis. Currently, the concept of implantation of cryopreserved human vascular allografts is studied clinically. Its efficiency in infected areas and following prosthetic replacement of the thoracic aorta has not been proven. Some preliminary results as well as studies on treatment for bacterial endocarditis would suggest a clear advantage of this strategy, however statistically significant improvements have not been published. Currently available data, however, appear to be sufficient to advocate potentially successful techniques as a prophylaxis in routine thoracic aortic replacement as well as for treatment in case of a vascular prosthetic infection following such procedures.

Animals↗
PubMed1994

Patterns of donor-type microchimerism after heart transplantation.

Allogeneic microchimerism of donor-type has been demonstrated in stable patients in the long-term after organ transplantation. We have analysed microchimerism in skin and blood of 47 heart-transplanted patients after transplantation with polymerase-chain-reaction amplification specific for donor HLA-DRB1. Microchimerism was detectable in 50% of the patients in the first 6 months, in 100% between 6 months and 2 years, and in 58% in the third postoperative year or later. The state of chimerism was not related to acute or chronic rejections. Patterns of microchimerism after heart transplantation may be dynamic, but any association with clinical and immunological variables remains to be elucidated.

Gene Amplification↗
PubMed1994

[Mediastinal tumor and airway obstruction in general anesthesia. Case report and review of the literature].

Case report of an acute airway obstruction during general anaesthesia by compression of the left main bronchus in an asymptomatic patient with unknown mediastinal mass. The patient was scheduled for a relief of a thyroid gland cyst. The compression occurred after uneventful induction of anaesthesia during the patient's positioning with flexed neck and elevated upper thorax on a pad. Increasing FiO2 from 0.5 to 1.0, repeated fiberoptic bronchoscopic examination and changing of the position of the endotracheal tube facilitated the operation. After reversal of the flexed neck position ventilation was normal. The intraoperatively suspected mediastinal tumour was confirmed by postoperative computerised tomography of thorax and neck. The teratoma was removed in toto in a second operation. In a review of the literature pathophysiological changes, preoperative assessment and anaesthetic management of patients with mediastinal tumour are discussed.

Adult↗
PubMed1994

Heart transplantation under coumarin therapy: friend or foe?

Thirty-six patients were included in a retrospective study of the effect of pre-operative anticoagulant therapy on peri-operative blood loss and haemostatic changes after heart transplantation. Eleven patients (group H) had received intravenous heparin for at least 3 weeks before cardiac transplantation. Twelve patients (group P) had been transplanted when fully anticoagulated with phenprocoumon. A control group of 13 patients (group C) had undergone bypass grafting of their coronary arteries with no pre-operative anticoagulant therapy. Post-operative drainage from the chest drains was 700 ml (median) in group H, 425 ml in group P, and 360 ml in group C (group H vs. group C: P < 0.05). After heparinization for cardiopulmonary bypass, activated clotting time was 462 s (median) in group H, 1500 s in group P, and 727 s in group C (P < 0.003 vs. groups H and P). Post-operatively, patients in group P were given more units of fresh frozen plasma (median 2.5 units; P < 0.01), prothrombin complex concentrate (median 1000 I.U.; P < 0.05) and vitamin K (median 10 mg; P < 0.05) than groups H and C. Heart transplantation under full phenprocoumon therapy does not increase the likelihood of complications caused by peri-operative bleeding.

Adult↗
PubMed1994

[The value of myocardia protection in chronic hypoxic immature rat hearts].

This study examines the efficacy of three methods for myocardial protection during 8 hours of global ischema at 10 degrees C in immature (28 days) rat hearts subjected to lifelong hypoxia afforded by exposure to simulated high altitude. Hearts in group 1 were protected by rapid topical cooling alone, in group 2 by slow pre-arrest cooling with Krebs-Henseleit solution plus topical cooling and in group 3 by coronary perfusion with St. Thomas' Hospital cardioplegia No 2 (STS 2) plus topical cooling. Hearts in groups 4-6 served as controls without hypoxia and were protected accordingly. Parameters of myocardial function (left ventricular pressure, LVP), the metabolic status (myocardial concentration of ATP and creatine phosphate) and endothelial function (response to the vasodilator acetylcholine) were measured. Myocardial protection by rapid topical cooling alone resulted in equal--or significantly improved--postischemic recovery of LVP and endothelial function compared with slow pre-arrest cooling or additional protection with STS 2. The data advocate topical cooling for myocardial protection during surgical correction of cyanotic congenital cardiac disease in early infancy. In this age group, coronary perfusion with cold crystalloid solutions appears to aggravate ischemic endothelial injury.

Animals↗
PubMed1993

The efficacy of controlled antibiotic release for prevention of polyethyleneterephthalate- (Dacron-) related infection in cardiovascular surgery.

Infection of prostheses containing polyethyleneterephthalate (Dacron) remains a dreaded complication in cardiovascular surgery despite perioperative antibiotic (AB) prophylaxis. Dacron, which is widely applied as a fabric for manufacturing vascular prostheses and also the sewing rings of artificial heart valves, remains a source for infection once implanted in the body. In order to increase the AB concentration in Dacron, an experimental study including topical application of the gentamicin derivative EMD 46/217 and fibrin sealant (F) as AB carrier was initiated. In-vitro pretreatment of Dacron with the gentamicin derivative and F was followed by constant AB release for three weeks. In a subsequent animal study, four Dacron rings with different pretreatments were implanted in the descending aorta of ten pigs after direct contamination with 10 8 Staph. aureus solution. One ring was pretreated with the AB/F compound, a second ring with the AB alone. Ring 3 (no pretreatment) and ring 4 (F alone) served as controls. After one week, the Dacron rings and their corresponding implantation sites were asserved for measurement of AB content and for culture. The AB content of AB/F rings was 24.99 +/- 7.16 mug/g wet weight, while Dacron rings pretreated with the AB alone contained no measurable drug amounts, with the exception of one specimen (0.5 mug/g)(AB/F versus AB rings: P less than 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗
PubMed1992

Introducing a selectively biodegradable filament wound arterial prosthesis: a short-term implantation study.

This article introduces a new compliant and selectively biodegradable filament wound vascular graft and reports the findings of a short-term implantation study. A basic feature of filament winding is its ability to tailor and better control the mechanical properties of the prosthesis, so that a closer match with the anisotropic properties of native arteries is achieved. The elastomeric vascular grafts comprise poly(ether urethane urea) fibers (Lycra) embedded in a two-component matrix consisting of poly(ether urethane) (Pellethane) and a highly flexible poly(ethylene glycol)/poly(lactic acid) biodegradable segmented copolymer (PELA). Typical tensile modulus values fall in the few megapascals (MPa) range, this being comparable to that of natural arteries. The wound graft exhibits excellent handling and suturability characteristics as well as enhanced burst strength. Furthermore, due to its biodegradable constituent, the prosthesis combines minimal intraoperative blood loss and high healing porosity. The graft displays initially negligible in vitro water permeation, which increases gradually with time. In this short-term study, the prostheses were implanted in the canine carotid, and their biological performance was compared to that of expanded Gore-Tex. The luminal surface of the wound grafts was coated with a thin layer of pseudointima, strongly adhered to the prosthesis surface. Contrasting with the very stiff Gore-Tex grafts, the filament wound prostheses retained their high compliance, being highly pulsatile upon explanation. Histological studies fully corroborated these findings, underscoring the healing properties of these new filament wound vascular prostheses.

Animals↗
PubMed1992

Nifedipine and diltiazem reduce pulmonary edema formation during postischemic reperfusion of the rabbit lung.

A protective effect of calcium antagonists in pulmonary preservation for transplantation has been observed recently. This report focuses on the potential use of diltiazem and nifedipine in the early phase of reperfusion after normothermic pulmonary ischemia. Rabbits weighing 4-5 kg were tracheotomized and ventilated with 50% oxygen. In a control group (group I, n = 7), the hilus of the right lung was clamped for 210 min without ischemia of the left lung. Lung ischemia was created in a second group (n = 7) by clamping the left hilum for 2 h. Subsequently, reperfusion of the left lung was maintained for 210 min, while the right hilus was kept occluded. In group III (n = 6) and group IV (n = 8) the conditions were the same as in group II, but either diltiazem (62.5 micrograms/kg i.v., group III) or nifedipine (3 micrograms/kg i.v., group IV) was administered during the first 20 min of reperfusion. After 210 min of reperfusion, the pulmonary vascular resistance was elevated in group II (mean: 5120 dyn.sec.cm-5), group III (5518 dyn.sec.cm-5), and group IV (4324 dyn.sec.cm-5) compared with group I (3390; n.s.). Arterial oxygenation showed no significant differences among group I (mean: 257 mmHg), group II (261 mmHg), group III (208 mmHg), and group IV (247 mmHg). Pulmonary ischemia resulted in an increased extravascular lung water content in group II as compared to group I (73 and 64 g/g wet weight; P less than 0.0125 vs group I). No such increase was seen in groups III and IV (53 and 54 g/g wet weight respectively; P less than 0.001 vs group II).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Optimal level of hypothermia for prolonged myocardial protection assessed by 31P nuclear magnetic resonance.

The optimal level of hypothermia during myocardial preservation for cardiac transplantation is not known. Phosphorus 31 nuclear magnetic resonance spectroscopy was used to assess the effect of different preservation temperatures (15 degrees C in group 1, 4 degrees C in group 2) on the myocardial high-energy phosphate profiles during prolonged global ischemia and subsequent reperfusion of isolated rat hearts. Adenosine triphosphate depletion during ischemia was more gradual in group 2, leading to significant differences in myocardial adenosine triphosphate concentrations between the two groups after 3 hours of ischemia. The fall in intracellular pH during ischemia was significantly less pronounced in hearts preserved at 4 degrees C as compared with those at 15 degrees C. The postischemic recovery of both the left ventricular peak systolic pressure and the maximum rate of increase of left ventricular pressure was enhanced in group 2, although the ischemic period was 3 hours longer than in group 1. Hypothermia at 4 degrees C as compared with 15 degrees C appears to prolong myocardial protection with respect to adenosine triphosphate preservation, prevention of the fall in intracellular pH, and the enhancement of postischemic hemodynamic recovery.

Adenosine Triphosphate↗