Inter-species differences in hematocrit to blood viscosity ratio.

Hematocrit (Hct) is the major determinant of whole blood viscosity and of its oxygen binding capacity: with increasing Hct, viscosity increases exponentially and oxygen capacity increases linearly. Thus, the theoretical oxygen transport potential of blood, as indexed by the ratio of Hct to viscosity (Hct/viscosity), generally yields a curve concave to the Hct axis with a maximum at an "optimal hematocrit" value. This study analyzed relations between Hct, blood viscosity and shear rate for rats and dogs to explore whether different optima exist for Hct or Hct/viscosity. Our results reveal differences depending on both shear rate and species: at equal Hct, rats had higher blood viscosity and thus lower Hct/viscosity levels. Optimum values for Hct/viscosity were markedly different between the two species at shear rates of 90 and 200 s-1. Conversely, Hct/viscosity data at 10 s-1 did not exhibit an optimum but rather a linear decrease of the ratio with increasing hematocrit. Relations between Hct and blood viscosity thus differ among animal species. Inasmuch as animal studies are often utilized as an aid to understanding hemorheological aspects of clinical conditions and/or therapy, evaluating Hct/viscosity ratios may be a useful supplementary tool for research focused on various physiological and patho-physiological processes.

Hemorheological changes caused by intermittent Pringle (Baron) maneuver in beagle canine model.

In liver resection operations the Pringle (Baron) maneuver can be used for temporary ischemia by clamping the hepatoduodenal ligament intermittently. In this beagle canine model we investigated whether hemorheological parameters may alter in systemic, portal and hepatic venous blood and in arterial samples during-after Pringle maneuvers. In Pringle Group unilateral femoral artery and external jugular vein were cannulated. From median laparotomy the hepatoduodenal ligament was exposed. The portal venous system was catheterized via a mesenteric vein and through the inferior caval vein a catheter was led to the hepatic veins. After stabilization, a 15-minute Pringle maneuver was carried out three times with 5-minute interpolated reperfusion periods. In Control Group Pringle maneuvers were not made. Before and after Pringle maneuvers parallel blood samples were taken from the cannulated vessels for determining hematological parameters and erythrocyte aggregation. Following Pringle maneuvers erythrocyte deformability, blood and plasma viscosity were also tested. The results showed that besides systemic hemorheological effects of the intermittent Pringle maneuver local leukocyte count, hematocrit and erythrocyte aggregation index altered mainly in portal venous blood, depending on the repeating number of the maneuvers. Thus, investigations of hemorheological parameters might be useful to determine the optimal duration of the Pringle maneuver.

Adhesion formation with open versus laparoscopic cholecystectomy: an immunologic and histologic study.

BACKGROUND: This randomized study aimed to compare the reaction of the immune system to the process of postoperative adhesion formation after open and laparoscopic cholecystectomy. METHODS: In this study, 20 mongrel dogs were used: 10 each in the laparoscopic and open cholecystectomy groups. Blood and peritoneal lavage samples were taken up to postoperative day 14, followed by second-look laparoscopy and reoperation to detect the rate of adhesion formation. Also, specimens were obtained from the liver bed for histology. RESULTS: In the open cholecystectomy group, the white blood cell count was higher in blood samples and lower in lavage specimens. Adhesion formation was extensive, and the histologic immune reaction was more intensive in the open cholecystectomy group. CONCLUSION: This randomized study proved that laparoscopic cholecystectomy was associated with less immune suppression, less inflammatory reaction, and therefore less adhesion formation than open cholecystectomy.

The effects of renal ischemia-reperfusion on hemorheological factors: preventive role of allopurinol.

Changes in hemorheological parameters were studied in dogs following unilateral renal artery clamping (45-minute ischemia then reperfusion), with and without preoperative administration of allopurinol. Sham-operated animals were also evaluated. Blood samples were collected preoperatively, at beginning and at 30, 60 and 120 minutes of reperfusion, then on the 1st, 3rd, 5th and 7th days. Filtration properties of erythrocytes (relative cell transit time, RCTT), whole blood and plasma viscosity (WBV, PV), fibrinogen level and hematology parameter were determined. RCTT significantly increased for both ischemic groups at 30 minutes of reperfusion, and remained elevated on the 1st and 2nd postoperative days; these changes were abolished by allopurinol pretreatment. WBV and hematocrit increased on the 1st day, and PV and fibrinogen level showed elevation on 1st-5th postoperative days. We thus conclude that decreases of RBC deformability (i.e., higher RCTT) were characteristic and specific on early postoperative days after renal ischemia-reperfusion and that these alterations were prevented by pre-ischemia administration of allopurinol.

Local and systemic hemorheological effects of cerebral hyper- and hypoperfusion in a porcine model.

Using a well defined pig model, we investigated whether cerebral hypertension and hypotension influence hemorheological factors. After surgical preparation and stabilization, periods of hyperventilation, controlled periods of cerebral perfusion pressure increases and decreases were utilized. After each period, blood samples were collected from the cannulated femoral artery and vein, and from the superior sagittal sinus. Erythrocyte deformability, whole blood and plasma viscosity and hematological parameters were determined. Erythrocyte deformability significantly worsened in arterial samples after hypertension and hypotension, and in sinus samples it was impaired after hypotension period. Hematocrit significantly increased in arterial and sinus samples during hypertensive period, accompanied by similar alterations in whole blood viscosity. We conclude that hemodynamic changes caused by hyperventilation, hyper- or hypotension can influence hemorheological factors, and suggest that the rheological alterations can affect local hemodynamic and metabolic conditions.

Comparison between continuous brain tissue pO2, pCO2, pH, and temperature and simultaneous cerebrovenous measurement using a multisensor probe in a porcine intracranial pressure model.

Local brain tissue oxygenation (p(ti)O2) and global cerebrovenous hemoglobin saturation (SjO2) are increasingly used to continuously monitor patients after severe head injury (SHI). In patients, simultaneous local and global oxygen measurements of these types have shown different results regarding the comparability of the findings during changes in CPP and ICP. This is in contrast to theoretical expectations. The aim of this study was to compare p(ti)O2 measurement with cerebrovenous oxygen partial pressure measurement (p(cv)O2) in an animal intracranial pressure model. To this end, a multisensor probe was placed in the left frontoparietal white matter to measure p(ti)O2, pCO2 (p(ti)CO2), pH (pH[ti]), and temperature (t[ti]) while simultaneously measuring these same parameters (p(cv)O2, p(cv)CO2 pH(cv), t[cv]) in the sagittal sinus of 9 pigs under general anesthesia. By stepwise inflating a balloon catheter, placed in supracerebellar infratentorial compartment, ICP was increased and CPP was decreased. The baseline levels of p(ti)O2, p(ti)CO2, and pH(ti) in the noninjured brain tissue showed more heterogeneity compared to the findings in cerebrovenous blood. Both, p(ti)O2 and p(cv)O2 were significantly correlated to the induced CPP decrease. PCO2 was inversely correlated to the course of CPP in both measurement compartments. Temperature measurement showed a positive correlation with CPP in both compartments. These findings demonstrate that brain tissue oximetry and cerebrovenous PO2 measurement are sensitive to CPP changes. The newly available continuous parameters in multisensor probes could be helpful in interpreting findings of cerebral oxygen measurement in man by analyzing the interrelationship of these parameters.

Continuous monitoring of the partial pressure of oxygen in cerebral venous blood.

OBJECTIVE: Clinical oxygen monitoring in the injured brain is somewhat difficult. However, ischemia is one of the major factors responsible for secondary tissue damage after head injury or subarachnoid hemorrhage. Therefore, the aim of the present study was to investigate the value of continuously monitoring the partial pressure of oxygen in cerebral venous blood (PcvO2) during changes in intracranial pressure (ICP). METHODS: In eight domestic pigs with Clark type probes placed in the posterior third of the superior sagittal sinus, PcvO2 was continuously registered while ICP was stepwise elevated by an inflatable balloon placed below the tentorium. Arterial blood pressure was continuously monitored, cerebral perfusion pressure (CPP) was calculated, and arterial partial carbon dioxide pressure and partial pressure of oxygen were registered intermittently. RESULTS: The mean intraparenchymal ICP before the start of balloon inflation was 5 +/- 1 mm Hg, the mean CPP was 80 +/- 15 mm Hg, and the mean PcvO2 was 36 +/- 3 mm Hg. At maximum ICP elevation, CPP decreased to 20 +/- 12 mm Hg, PcvO2 decreased to 10 +/- 6 mm Hg, and ICP increased to 90 +/- 10 mm Hg. Strong linear correlations between ICP and PcvO2 and between CPP and PcvO2 were revealed, and mean correlation coefficients of 0.89 for ICP/PcvO2 and 0.73 for CPP/PcvO2 were calculated. CONCLUSION: The present study demonstrates that polarographic PcvO2 monitoring in the superior sagittal sinus is a reliable method for the early detection of reduced CPP during ICP elevation. This technique is capable of registering the global oxygen supply and oxygen consumption of the brain. It seems superior to jugular venous oxymetry and is better suited for clinical use because of a somewhat low artifact susceptibility.

The influence of intraoperative complications on adhesion formation during laparoscopic and conventional cholecystectomy in an animal model.

BACKGROUND: The aim of this study was to evaluate the extent of postoperative adhesion formation after laparoscopic and open cholecystectomy. MATERIALS AND METHODS: Qualified surgeons performed 60 experimental laparoscopic cholecystectomies (LC) in dogs with the aim to acquire the laparoscopic technique. To assess the relation between the complications during the operation (bleeding, laceration of the liver bed, or gallbladder perforation) and the formation of adhesions, surviving animals were divided into four groups according to the type of complication occurred. Assessment of the results was made by second-look laparoscopy 4 weeks after LC using the adhesion index (AI; score range, 0-4). The animals then were killed so the extent of adhesion formation could be measured. As a control, open cholecystectomy was performed in 15 dogs without intraoperative complications. The Mann-Whitney rank-sum test and Dunn's method were used for statistical analysis. RESULTS: No adhesion formation or intraoperative complications were registered in the laparoscopic group I. In all the cases wherein bleeding or laceration of the liver bed occurred and was managed with electrocoagulation, adhesions formed. Adhesion formation in these groups was significantly higher than in "ideal LC" or cases of gallbladder perforation alone (p < 0.01). All the animals in the control group developed significantly more adhesions than those in the experimental group (p < 0.05). CONCLUSIONS: It seems that LC has a lower rate of adhesion formation than the conventional open technique. Complications such as bleeding or laceration of the liver bed during LC can enhance adhesion formation. No adhesion formation can be mentioned in relation to gallbladder perforation during LC.

Cerebrovenous blood temperature-influence of cerebral perfusion pressure changes and hyperventilation: evaluation in a porcine study and in man.

The objective of the first part of this study was to use an animal model to investigate the relationship between temperature in the cerebrovenous compartment and cerebral perfusion pressure. In the second part of the study, the objective was to examine the influence of hyperventilation and hypothermia on jugular bulb temperature and body temperature in patients undergoing elective neurosurgery. Intracranial pressure was increased artificially by inflating an infratentorial supracerebellar placed balloon catheter in nine pigs under general anesthesia. Temperature was monitored by thermocouples inserted in the sagittal sinus, white matter of the left lobe and abdominal aorta during the ensuing decrease in cerebral profusion pressure (CPP). Cerebrovenous blood temperature (jugular bulb) and body temperature (urinary bladder) were simultaneously monitored in 24 patients undergoing craniotomy. Moderate hyperventilation was performed in all patients. Cerebrovenous blood and core body temperature were recorded and differences between these two temperatures calculated at the beginning and the end of hyperventilation. At the beginning of the intracranial pressure (ICP), increase mean temperatures of cerebrovenous blood and cerebral tissue (left lobe) were lower than core body temperature. During CPP reduction the difference between core body temperature and cerebrovenous blood temperature increased significantly from 0.86+/-0.44 degrees C prior to ICP rise to 1.19+/-0.58 degrees C at maximum ICP. Before hyperventilation, cerebrovenous blood temperature was higher in 19 patients (+/- difference: 0.34 degrees C +/- 0.27) and equal or lower in five patients (difference: -0.08 degrees C +/- 0.11), than core body temperature. At the end of hyperventilation, the difference between cerebrovenous blood temperature and core body temperature increased (+0.42 degrees C +/- 0.24) in those 19 patients who had started with a higher cerebrovenous blood temperature and decreased (-0.10 degrees C +/- 0. 18) in the other five patients. Both studies demonstrated that the temperature of cerebrovenous blood is influenced by maneuvers which are supposed to decrease cerebral blood flow.

Simultaneous continuous measurement of pO2, pCO2, pH and temperature in brain tissue and sagittal sinus in a porcine model.

INTRODUCTION: The clinical use of brain tissue oxygen measurement in patients with severe head injury is increasing. It is important to compare the findings in brain tissue with cerebrovenous blood oximetry, to obtain normal values and to find out limitations of the method. We evaluated a newly available multisensor probe simultaneously in the brain tissue and in the sagittal sinus in a porcine animal model. METHODS: We placed the Paratrend 7-probe (BSL, High Wycombe, UK) in the left frontoparietal white matter and measured pO2 (PtiO2), pCO2 (ptiCO2), pH and temperature while simultaneously measuring these parameters (pcvO2, pcvCO2) in the sagittal sinus in 7 pigs under general anaesthesia during oxygen enhancement. RESULTS: The relation between oxygen increase in brain tissue and in the sagittal sinus showed a coefficient of correlation (CCmean) rmean = 0.96. The quantitative response in brain tissue was much more sensitive than in the sinus. A close correlation between pCO2 in brain tissue and sagittal sinus and the increase of the inspired oxygen was seen: CC ptiCO2 to arterial oxygen pressure (paO2) - rmean = 0.67, CC pcvCO2 to paO2 - rmean = 0.88. CONCLUSIONS: Measuring partial oxygen pressure in brain tissue is more responsive to physiological variations, and the absolute values are more sensitive than oxygen measurement in the cerebrovenous compartment. This is important for interpreting measured values and introducing new coefficients for patient monitoring.

Protecting effects of intravenous insoluble glycogen treatment on the experimental necrotizing acute pancreatitis of dogs.

BACKGROUND/AIMS: We have studied the effects of insoluble glycogen applied intravenously on the experimental acute pancreatitis of dogs. METHODS: Experimental acute pancreatitis was induced by olive oil injected into the main pancreatic duct. The effects of insoluble glycogen were evaluated histologically and by measurements of levels of amylase, lipase in sera. The binding of endotoxin and secretable phospholipase A2 by insoluble glycogen were tested by isotopically labeled materials. RESULTS: Application of insoluble glycogen had beneficial effects on the experimental acute pancreatitis of dogs. CONCLUSION: The binding capacity on endotoxin and secretable phospholipase A2 could play the main role in the protection offered by insoluble glycogen.

Systemic and regional hemorheological consequences of warm and cold hind limb ischemia-reperfusion in a canine model.

We have studied systemic and regional changes in hemorheological parameters after complete acute limb ischemia and reperfusion (I/R) in 24 mongrel dogs. Unilateral cooled and non-cooled vascular ischemia (3 h)-reperfusion (4 h), and sham-operations were performed. Blood samples were collected from the excluded region, during reperfusion and for 5 days. Whole blood and plasma viscosity (WBV, PV), relative cell transit time (RCTT) of erythrocytes, fibrinogen level and hematological parameters were determined. In I/R groups WBV of excluded blood was significantly higher compared to the base (p < 0.05), and RCTT increased during the reperfusion. On 2nd-3rd days RCTT increased significantly in both I/R groups. In each group PV and fibrinogen showed continuous increase during the postoperative period, prominently in cooled I/R group, and furthermore WBV corrected for hematocrit (40%) was the highest in cooled I/R group. These suggest that surgical acute limb I/R may cause hemorheological changes, which are more serious after cooling. (Grants: OTKA-T032571, 6003/1/2001/ETT.)

Use of absorbable material for the closure of experimental longitudinal nephrotomy.

Large nephrotomy incisions made in 15 dogs were closed by sewing up the cavity system with stitches of 5/0 catgut and by sealing the renal parenchyma with tissue adhesive being pinpointed at the opened vessels. The incision was covered with a preparation of oxidized cellulose which was then likewise impregnated with tissue adhesive. This technique was found rapid and convenient and provided for adequate haemostasis. Its essential advantage lies in eliminating the deep through-and-through sutures involving a major loss of functioning renal parenchyma. All substances used were absorbed in due time.

[Autologous spleen transplantation]. / Lép autotransplantatio.

Splenectomy is known to increase the risk of overwhelming bacterial infection. There is a decrease in immunoglobulin IgM, T-lymphocytes, impaired primary antibody response to antigen challenge, an altered opsonic function and a tuftsin deficiency. Splenic autotransplantation has been suggested as a method of preserving function and this concept is supported by experiments in animals (dogs). The study describes autotransplantation of the traumatized spleen in human beings for the preservation of splenic function. Eleven patients operated on for abdominal trauma in the Kenézy Hospital in Debrecen, required total splenectomy, than splenic autotransplantation. In these patients splenic slides were implanted in between two layers of omental pouch (Furka's "spleen chip"). In 10 patients the follow-up radionuclid imaging, the IgM level, and the tuftsin level unambiguously confirmed the functioning of the splenic tissue.

Sutureless closure of the renal wound surface by extracorporeal renal surgery on dogs.

The authors have elaborated a sutureless method of closing the wound surface in order to preserve the renal parenchyma. They have used oxydized cellulose net (Surgicel) and tissue adhesive (Histoacryl-N-blau) to hold together the cut surface of the kidney at renal hypothermy (bench surgery) on dogs.

[Effect of pentoxifylline on the healing of experimental anastomosis of the left colon in rats]. / A pentoxifyllinum hatása a kísérletes bal colonfél anasztomózis gyógyulására.

The healing of colonic anastomoses is determined by several factors such as microcirculation, the strength of the inflammatory response, and the time required for regeneration. We investigated the effects of pentoxifylline--a drug which improves microcirculation and modulates leukocyte functions--on the healing of experimental anastomosis on the left colon of rats. As a result of drug treatment (0.25 mg/100 g, i.p.) in Group I anastomosis bursting pressure (ABP) was by 56 +/- 17% higher at day 2 than in controls with no pentoxifylline treatment. On the 5th postoperative day in Group I, ABP reached 80 +/- 8% the value for the intact colon (218 +/- 21 mmHg), whereas respective value in the control (untreated) group was only 47 +/- 7%. In Group II (pentoxifylline: 2 mg/100 g, i.p.) ABP was by 55 +/- 10% and by 73 +/- 8% higher than control values at postoperative days 1 and 2, respectively. At day 2, in Group I colonic blood flow measured at the anastomosis line by 86Rb uptake technique was significantly higher than in the untreated controls (0.18 +/- 0.01 ml/min vs. 0.14 +/- 0.01 ml/min, (p < 0.02). Blood flow measured in colon tissue above and below the anastomosis changed differently. Pentoxifylline treatment also suppressed the peritoneal inflammatory response assessed with peritoneal reaction index (2.0 +/- 0.3 vs. 1.1 +/- 0.2, p < 0.01). The results of the present study show that pentoxifylline treatment shortens the time needed for the healing of colonic anastomosis. These observations suggest that pentoxifylline medication can prevent failure of colonic anastomoses.

[How do intraoperative complications effect adhesion formation after laparoscopic cholecystectomy: a comparative animal study]. / Az intraoperatív szövódmények hatása a posztoperatív hasúri adhesiók kialakulására laparoszkópos cholecystectomiát követóen: összehasonlító állatkísérlet.

BACKGROUND: The aim of this study was to evaluate the extent of postoperative formation of adhesions following laparoscopic and open cholecystectomy. MATERIAL AND METHODS: 60 experimental laparoscopic cholecystectomies (LC) were performed in dogs by qualified surgeons to learn laparoscopic technique. To assess the relationship between complications occurred during the operation (bleeding, laceration of the liver bed or gallbladder perforation) and the formation of adhesions surviving animals were divided into 4 groups according to the type of complication. We assessed the results during second-look laparoscopy 4 weeks following LC using the adhesion index (AI: 0-4 score). Animals were then sacrificed to measure the extent of adhesions. As a control group open cholecystectomy was performed in 15 dogs without intraoperative complications. Mann-Whitney Rank Sum test and Dunn's Method were used for statistical analysis. RESULTS: No adhesions were observed in the laparoscopic group without intraoperative complications. In all dogs with bleeding or laceration of the liver bed maintained by electrocoagulation, adhesions developed. Formation of adhesion in these groups was significantly higher than in "ideal LC" or in case of gallbladder perforation (P < 0.01). All animals in the control group developed significantly more adhesions compared to the experimental group (p < 0.05). CONCLUSION: LC produces less adhesion compared to conventional open technique. Complications such as bleeding or laceration of the liver bed during LC can increase the formation of adhesions. No formation of adhesions can be related to gallbladder perforation during LC.

[Heterotopic autotransplantation of the spleen in animal experiments]. / Geterotopicheskaia autotransplantatsiia selezenki v éksperimente.

A new technique of heterotopic autotransplantation of pieces of the spleen is suggested. It differs from the methods used previously in that the pieces of the autologous transplant are placed between the layers of the greater omentum and not on its surface. Not only was the viability of the pieces of the autologous transplant maintained but the hazard of intraabdominal adhesions and their unfavourable consequences was reduced to a great measure.