G. Kehrer

Construction and experimental application of a catheter for selective arterial kidney perfusion in situ

SummaryIn order to improve dog kidney perfusion in situ with a protective solution, a perfusion catheter was constructed which allowed continuous pressure measurement in the center of the catheter tip during perfusion. Using this catheter, the equilibration of the extracellular space with a protective solution (HTK solution) was found to be pressure dependent. Continuous pressure and resistance control is therefore a prerequisite for reliable organ protection.

Post-ischemic renal function after kidney protection with the HTK-solution of Bretschneider

SummaryThe cardioplegic solution HTK of Bretschneider was used for canine kidney protection. The kidneys were perfused with this solution for 6–10 min prior to the induction of ischemia. The kidneys were left in-situ for 60, 90, 120 and 135 min ischemia time at a temperature of 25–34°C (n=13). As a control group we used unilateral nephrectomized dogs (n=9). After unilateral nephrectomy an elevated plasma creatinine in comparison to preoperative values was observed. After 60 and 90 min under HTK-protection the postoperative plasma creatinine was not elevated compared to the control group. After 120 min of ischemia creatinine level was slightly increased to an average of 2.1 mg% on the first and second postoperative day. These experiments indicate the protective effect of the cardioplegic solution for canine kidney preservation in situ.

Metabolic, energetic and structural changes in protected and unprotected kidneys at temperatures of 1 °C and 25 °C

SummaryIn 110 canine kidneys, we examined the time course of energy rich phosphates, lactate, intrarenal ph and renal morphology with Euro-Collins-or with HTK-protection of Bretschneider and compared these findings with unprotected kidneys during complete ischemia at 1 °C and at 25 °C. Both kidney protective solutions prolonged energyrich phosphate-decline by a factor of 3–4 compared with that of unprotected kidneys. The lactate increase was greater in Euro-Collins-protected kidneys than in HTK-protected and in unprotected kidneys, leading to pH values of 6.5 in Euro-Collins and to 6.4 in unprotected kidneys after 24 hours, in contrast to a pH-value of 7.3 with HTK-protection. This may be the reason for structural deterioration seen in unprotected and in Euro-Collins-protected kidneys after 12, and 48 h of ischemia at 1 °C, whereas in HTK-protected kidneys a sufficient preservation of structure can be seen. In one human kidney, protected with Euro-Collins-solution, we were able to show that at 1 °C intrarenal pH and lactate accumulation is similiar to the levels in canine kidneys. In Euro-Collins preserved kidneys lactate accumulation at 25 °C is even greater than at 1 °C, leading to inhibition of energy metabolism and to structural deterioration, whereas HTK-solution, because of its high buffer concentration, is able to maintain ischemic metabolism leading to sufficient protection of intrarenal pH and of adenine nucleotides as well as structural protection at 1 °C and at 25 °C.

Urinary LDH-release for evaluation of postischemic renal function

SummaryFollowing renal ischemia under protection, the perfusion of the tubular system increases concomitant to the rise of GFR. The transport into urine of enzymes entering the tubular lumen due to ischemic injury is dependent on tubular flow. Thus, we examined if in the early post-ischemic phase urinary enzyme determinations can contribute to the evaluation of a changing tubular washout. Canine kidneys were perfused with different protective solutions and subsequently rendered ischemic. From the beginning of reperfusion the endogenous creatinine clearance, the urine minute volume and the urinary LDH-concentration were determined. The urinary LDH-concentration allowed only a rough assessment of renal ischemic damage. The adjustment of the urinary LDH amounts to the GFR resulted in a better graduation according to the ischemic stress. With such a standardized LDH parameter the urinary LDH release was somewhat lower on the average when L-aspartate was added to the HTK solution in place of chloride. In conclusion, during the early postischemic recovery after renal protection the examination of the urinary enzyme release may be a useful diagnostic means for the assessment of the extent of the ischemic injury if an appropriate frame of reference is applied.

A new method for conservative renal surgery — experimental and first clinical results

ZusammenfassungZur Verlängerung der renalen Ischämie stehen bisher zwei Verfahren zur Verfügung: 1) eine Oberflächenkilhlüng mit Eis and 2) eine Perfusionskühlung mit einer extrazellulären Losung. Beide Methoden nutzen nur das Prinzip der Stoffwechselsenkung durch Kühlung. Während der Wiedererwärmung bei der Operation geht der Ischämieschutz verloren oder die Niere muß erneut gekiihlt werden. Deshalb sollte eine neue Protektionslösung den Energieverbrauch zusätzlich zur Kühlung auch durch ihre Zusammensetzung senken. Bei offenen Herzoperationen wird die HTK-Lösung nach Bretschneider bereits klinisch angewendet. In 71 Experimenten an Hundenieren wurde die Ischämiezeit durch diese Lösung von 15 auf 120 min bei 35°C and von 45 auf 360 min bei 25°C. verlängert. Nach 120 min Ischämie bei 30°C betrug die glomeruläre Filtrationsrate ca. 20 ml/min 100gFG innerhalb von 3 h Reperfusion. Nach 6 Tagen postoperativ war die GFR wieder 40 ml/min 100gFG. Es konnte kein ischämischer Schaden durch histologische Untersuchungen mehr festgestellt werden. Der klinische Nutzen dieser Methode konnte in 7 klinischen Anwendungen gezeigt werden. Die Ischamiezeit betrug bis zu 113 min and das Kreatinin lag zwischen 0,8 and 2,4 mg% am 6. postoperativen Tag. Dieses Protektionsverfahren führt also zu einer verbesserten Nierenfunktion in der postoperativen Phase. Eine längere Ischämiezeit wird von der Niere vertragen, and unter Anwendung dieser Technik wird eine ausgezeichnete Übersichtlichkeit während der Nierenoperation erreicht, was eine radikale Tumorexzision erleichtert.SummarySo far two methods for prolonging the tolerance of renal ischemia are available: 1) surface cooling with crushed ice and 2) perfusion cooling with an extracellular-like solution. Both methods use only the principle of reducing metabolism through cooling. While rewarming during surgery the ischemic protection is lost, or the kidney must be cooled once again. Therefore, a new preservation solution should reduce energy consumption due to its composition in addition to cooling. For open heart surgery, the HTK solution by Bretschneider is already used clinically. In 71 dog kidney experiments, the ischemic time kidneys could tolerate was prolonged by this solution from 15 to 120 min at 35°C and from 45 to 360 min at 25°C. After 2h of ischemia at 30°C glomerular filtration rate was about 20 ml/min · 100 gww within 3 h of reperfusion. After six postoperative days the filtration rate was 40 ml/min · 100 gww. No ischemic damage could be recognized by histological investigations. The clinical effectiveness of this method was shown in 7 clinical applications. Ischemic duration lasted up to 113 min, and blood creatinine was between 0.8 and 2.4 mg% at the 6th postoperative day. Use of this preservation technique thus leads to improved kidney function immediately following operation. Longer ischemia can be tolerated by a kidney thus protected, and using this technique excellent visibility can be achieved during intrarenal surgery, simplifying, for example, tumor extirpation.

Contribution of amino acids in protective solutions to postischemic functional recovery of canine kidneys

SummaryAmino acids are known to increase glomerular filtration rate (GFR). There is also an early resumption of filtration following 2-h renal ischemic stress under protection by histidine-buffered histidine-tryptophanketoglutarate solution (HTK), possibly due in part to an amino acid effect. Hence, we have examined the possibility of further enhancing the postischemic GFR by adding 32 (ASP I; 4 mM Mg2+) or 36 (ASP II; 6 mM Mg2+) mMl-aspartate (asp) or 32 mMdl-aspartate (ASP III) to the HTK solution in place of chloride. After infusion of 500 ml 5% glucose, canine kidneys were protected by an 8-min perfusion with HTK (n = 5), ASP I (n = 4), ASP II (n = 5) or ASP III-solution (n = 3). The subsequent ischemia lasted for 2 h at 27–31°C. During reperfusion, both GFR and filtration fraction (FF) were higher in kidneys protected byl-aspartate-containing solutions. ASP III showed no improvement against HTK. An additional preischemic intraaortal application of HTK or ASP I solution just above the exit of the renal arteries prior to the intrinsic protective perfusion further raised the postischemic GFR. The present results suggest thatl-aspartate but also histidine may have favorable amino acid effects in renal protective solutions in addition to known positive effects of histidine.

Morphologische Untersuchungen von Schweinelebern nach Konservierung mit Euro-Collins Lösung, University of Wisconsin-Lösung und der HTK-Lösung nach Bretschneider

Zur Klarung der Frage, ob unter der Anwendung verschiedener Verfahren zur Leberkonservierung strukturell nachweisbare perfusionsbedingte Schaden auftreten konnen, wurden Lebern von Schweinen mit a) HTK-Losung nach Bretschneider (Histidin-Tryptophan-Ketoglutarat), b) Euro-Collins-Losung (EC), c) “University of Wisconsin”-Losung (UW) entsprechend den Anweisungen des Herstellers perfundiert. Anschliesend wurden alle Organe zusammen mit unprotelctionierten Lebern licht- und elektronenmikroskopisch unter Einschlus computergestutzter morphometrischer Analysen untersucht. Die Kontinuitat der Sinusendothelzellen, die Weite des Disseschen Raumes sowie die Ultrastruktur der Hepatozyten wurden primar durch keines der protektiven Verfahren beeintrdchtigt. Betrachtliche Unterschiede wurden aber hinsichtlich der Ausspulung des Blutes festgestellt. Die mit der HTK-Losung perfundierten lebern waren mit Abstand am besten von korpuskularen Blutbestandteilen befreit, gefolgt von EC-und UW-Lebern. Mittels eines computerunterstutzten Morphometrieverfahrens konnten keine signifikanten Grosenunterschiede zwischen den Hepatozyten der EC-, UW- and HTK-Gruppe festgestellt wurden. Lediglich die Hepatozyten der normothermen Kontrollebern waren um 10% groser als diejenigen in den mit den 3 protektiven Losungen perfundierten Organen. Es ergaben sich unter keinem der drei Protektionsverfahren strukturelle Anhaltspunkte fur einen Perfusionsschaden.ZusammenfassungZur Klärung der Frage, ob unter der Anwendung verschiedener Verfahren zur Leberkonservierung strukturell nachweisbare perfusionsbedingte Schäden auftreten können, wurden Lebern von Schweinen mit a) HTK-Lösung nach Bretschneider (Histidin-Tryptophan-Ketoglutarat), b) Euro-Collins-Lösung (EC), c) “University of Wisconsin”-Lösung (UW) entsprechend den Anweisungen des Herstellers perfundiert. Anschließend wurden alle Organe zusammen mit unprotelctionierten Lebern licht- und elektronenmikroskopisch unter Einschluß computergestutzter morphometrischer Analysen untersucht. Die Kontinuität der Sinusendothelzellen, die Weite des Disseschen Raumes sowie die Ultrastruktur der Hepatozyten wurden primär durch keines der protektiven Verfahren beeintrdchtigt. Beträchtliche Unterschiede wurden aber hinsichtlich der Ausspülung des Blutes festgestellt. Die mit der HTK-Lösung perfundierten lebern waren mit Abstand am besten von korpuskulären Blutbestandteilen befreit, gefolgt von EC-und UW-Lebern. Mittels eines computerunterstützten Morphometrieverfahrens konnten keine signifikanten Größenunterschiede zwischen den Hepatozyten der EC-, UW- and HTK-Gruppe festgestellt wurden. Lediglich die Hepatozyten der normothermen Kontrollebern waren um 10% größer als diejenigen in den mit den 3 protektiven Lösungen perfundierten Organen. Es ergaben sich unter keinem der drei Protektionsverfahren strukturelle Anhaltspunkte für einen Perfusionsschaden.SummaryIn order to study perfusion effects of different liver preservation methods on liver structure, porcine livers were perfused with either Bretschneiders HTK (Histidine Tryptophane Ketoglutarat) solution, Euro-Collins (EC) solution or University of Wisconsin solution (UW) according to the respective recommended protocols. Subsequently, together with a group of unprotected livers, all organs were examined by light and electron microscopy including computer assisted morphometry. The width of the space of Disse, the continuity of endothelial cells and the ultrastructure of the hepatocytes were not impaired after cold perfusion with any of the 3 solutions. However, we found considerable differences between the groups with respect to removal of blood cells from liver sinusoids. Livers flushed according to the HTK-protocol had the lowest residual blood cell content followed by the livers of the EC- and the UW-group. Centrilobular regions of the liver lobules were generally better washed free of blood than periportal zones. Computer assisted morphometry did not reveal any significant difference. between the size of hepatocytes of EC-, UW- and HTK livers. Only the hepatocytes of normothermic control livers (biopsy samples) were 10% larger than hepatocytes of cold flushed groups. None of the protective perfusion protocols showed structural signs of perfusion injury.

Postischemic diagnostic localization of tubular lesions

SummarySeveral functional parameters were applied in an experimental model of ischemia to test the ability to localize the distribution of tubular lesions. Canine kidneys were perfused with protective solutions and rendered ischemic for definite periods. Renal function was determined during a subsequent 3-h reperfusion. The pattern and the extent of renal injury were influenced by varying the duration of ischemia and by modifying the protective solution used. The results suggest that by employing an appropriate selection of parameters it is possible to allocate renal injury to definite sections of the tubules. According to such an evaluation, under protection with HTK-solution, the proximal tubule limits the tolerance of renal ischemia. The thick ascending limb shows some vulnerability that is aggravated by disadvantageous modifications of the protective solution and that may become more pronounced in the course of reperfusion. In contrast, more distal parts of the nephron retain a remarkable reserve transport capacity after a tolerable level of ischemia.

Short-term perfusion and "equilibration" of canine kidneys with protective solutions.

SummaryKidneys were perfused either with Euro-Collinssolution or with HTK-solution of Bretschneider. The perfusion pressure as well as the perfusion flow were measured during a six-minute perfusion. The perfusion resistance was higher in Euro-Collins-kidneys than during HTK-perfusion. The venous outflow of the kidney as well as the ureteral outflow was measured during each minute of the perfusion and has analysed for osmolality, and for sodium and potassium concentrations. In Euro-Collins-kidneys a complete “equilibration” of the extracellular space was not achieved, while during HTK-perfusion concentrations in the venous as in the tubular outflow, similar to those in the HTK-solution itself, could be reached. At the end of the different perfusions, tissue was analysed for biochemical parameters such as ATP, ADP, AMP and lactate as well as for morphological features. Lactate had increased and ATP had decreased during perfusion with Euro-Collins-solution, while ATP had not changed and lactate had decreased during perfusion with HTK-solution. Normal glomerular, tubular and dilated vascular structures can be seen after HTK-perfusion, while a glomerular and vascular contraction takes place during Euro-Collins-perfusion.

In-situ-Protektion der Leber mit der HTK-Lösung nach Bretschneider

SummaryLiver resections are usually performed under occlusion of the hepatoduodenal ligament (Pringle manoevre) in order to limit operative blood loss. The maximal ischemic tolerance, although individually different, is generally accepted to be 60 min. Resections of centrally located tumors require precise preparation, sometimes combined with vascular reconstructions. In such cases a prolonged ischemic time is inevitable. A save prolongation of the ischemic tolerance could be useful for extensive liver resections. In an experimental study in pigs ischemic tolerance of the liver was studied under hypothermic protection with the HTK solution of Bretschneider during 2 and 3 h. Deterioration of liver function was compared with a warm ischemia during 2 h. Results showed significantly less serum transaminase activities and better hepatic blood flow (ICG test) after an ischemia under protection with the HTK solution compared to a warm ischemia during 2 h. A prolonged ischemia during 3 h under protection with the HTK solution was well tolerated. First clinical applications of hypothermic hepatic protection during resection were successful.ZusammenfassungLeberresektionen werden zur Vermeidung größerer Blutverluste unter Okklusion des Ligamentum hepatoduodenale (Pringle manoevre) durchgeführt. Die maximale Ischämietoleranz, wenngleich individuell verschieden, wird in der Regel mit 60 min angegeben. Die Resektion von ungünstig gelegenen Tumoren erfordert eine präzise Präparation gegebenenfalls mit Gefäßrekonstruktionen, wodurch die Grenzbereiche der Ischämietoleranz häufiger erreicht werden. Eine sichere Ischämietoleranz gewinnt mit dem Resektionsausmaß zunehmende Bedeutung. Im Rahmen einer tierexperimentellen Studie wurde die Ischämietoleranz der Leber unter in-situ Protektion mit der HTK-Lösung nach Bretschneider während 2 bzw. 3 h untersucht und mit den funktionellen Auswirkungen einer 2-h warmen Ischämie verglichen. Die Ergebnisse ergaben nach einer Protektion mit der HTK-Lösung signifikant niedrigere Transaminaseaktivitäten und bessere Durchblutungsparameter (ICG-Test) gegenüber einer warmen Ischämie bei gleicher Ischämiezeit (2 h). Die Ischämietoleranz konnte durch die Protektion auf 3 h ausgeweitet werden. Erste klinische Anwendungen einer Resektion der Leber unter hypothermer Protektion mit der HTK-Lösung waren erfolgreich.