Pulmonary oxygen transfer deficits of diabetic origin in patients undergoing coronary artery bypass grafting

The objective of this study was to determine the effects of a diabetic disposition on pulmonary gas exchange by examining 72 patients who underwent coronary artery bypass grafting (CABG), using the arterial/alveolar oxygen tension ratio [(a/a)Po ₂] as a criterion. Patients were divided into a diabetic (DM) group and a nondiabetic (non-DM) group. The postoperative blood gases and hemodynamic data measured when the blood glucose level was at a maximum on the day of CABG were used as the postoperative pulmonary gas exchange indices, and the physicians who managed these patients were unaware of this study. The preoperative (a/a)Po ₂ ratio was 0.66±0.03 (SE) in the DM group and 0.78±0.02 in the non-DM group (P<0.01), while the postoperative ratios were 0.42±0.03 and 0.52±0.03, respectively (P=0.01). The correlation coefficient (r) for regression analysis of the relation between the postoperative Pao ₂/Fio ₂ ratio and the postoperative (a/a)Po ₂ ratio was 0.99 in the DM group (P<0.01) and 0.88 in the non-DM group (P<0.01). The r values of the relation between (a/a)Po ₂ and (a-a)Po ₂ were –0.68 (P<0.00) and –0.84 (P<0.01), while those for the respiratory index were –0.87 (P<0.01), and –0.93 (P<0.01), respectively. Thus, pulmonary oxygen transfer was compromised before and after CABG in the DM group compared to the non-DM group. Moreover, the Pao ₂/Fio ₂, being the simplest pulmonary gas exchange index to calculate, was a reliable substitute for the (a/a)Po ₂ ratio during the early postoperative management of CABG patients.     

Graft size-matching in living related partial liver transplantation in relation to tissue oxygenation and metabolic capacity

The influence of graft size-matching on tissue oxygenation and metabolic capability was studied in living related partial liver transplantations for 47 pediatric patients. Their age ranged from 4 months to 17 years 3 months, their body weight from 4.0 to 58.0 kg, graft weight from 191 to 440 g, and graft weight/recipient body weight ratio from 0.61% to 6.0%. Tissue oxygenation and its heterogeneity were investigated by measuring oxygen saturation of hemoglobin in the liver sinusoid (SO₂), coefficient of variation of SO₂, and arterial ketone body ratio. The metabolic capacity of the graft was investigated by measuring bilirubin clearance, recovery of cholesterol esterification, and ketone body production. In infants with a relatively large liver graft, both intra- and extracellular oxygenation remained low soon after reperfusion but recovered to the control value by the end of the operation. In adolescent recipients of a relatively small graft, by contrast, synthetic and detoxification capacities were relatively deficient; however, these improved with time. These results indicate that sufficient tissue oxygenation and liver regeneration are essential for successful liver transplantation with relatively large and small grafts, respectively.     

Prognostic value of intraoperative renal tissue oxygenation measurement on early renal transplant function

Ischemia time is a prognostic factor in renal transplantation for postoperative graft function and survival. Kidney transplants from living donors have a higher survival rate than deceased donor kidneys probably because of shorter ischemia time. We hypothesized that measurement of intraoperative kidney oxygenation (μHbO₂) and microvascular perfusion predicts postoperative graft function. We measured microvascular hemoglobin oxygen saturation by reflectance spectrophotometry and microcirculatory kidney perfusion by laser Doppler flowmetry 5 and 30 min after kidney reperfusion on the organ surface in 53 renal transplant patients including 19 grafts from living donors. These values were related to systemic hemodynamics, cold ischemia time (cit), early postoperative graft function and length of hospital stay. μHbO₂ improved 30 min after reperfusion compared to 5 min (from 67% to 71%, P < 0.05). μHbO₂ correlated with mean arterial blood pressure and central venous pH (P < 0.01). Most importantly, μHbO₂ was significantly higher in kidneys from living compared with deceased donors (74% vs. 63%) and in kidneys without vs. with biopsy‐proven postoperative rejection (71% vs. 45%, P < 0.001). Finally, μHbO₂ correlated positively with cit and postoperative creatinine clearance and negatively with postoperative plasma creatinine, need for hemodialysis and length of hospital stay. Our results suggest higher oxygen extraction and thus oxygen demand of the grafts shortly after reperfusion. The intraoperative measurement of tissue oxygenation in kidney transplants is predictive of early postoperative graft function. Future studies should evaluate the potential effect of intraoperative therapeutic maneuvers to improve organ tissue oxygenation in renal transplantation.     

Intraoperative measurement of the graft oxygenation state in living related liver transplantation by near infrared spectroscopy

Graft oxygenation plays an important role in successful liver transplantation. Intraoperative changes in the oxygenation state of the liver graft were measured by near infrared spectroscopy in 28 cases of living related liver transplantation. Oxygen saturation of hemoglobin in the liver (hepatic SO₂) changed from 81.2%±1.5% (mean±SEM) before donation (in the donor) to 49.7%±4.2% after portal reflow, to 58.4%±5.0% after arterial reflow, and then to 71.4%±3.9% before closure. Mean hepatic SO₂ was positively correlated with portal flow rate as measured by duplex Doppler sonography. Cases with low portal flow rate showed a high coefficient of variation (SD/mean) of hepatic SO₂, indicating heterogeneous tissue oxygenation. Though graft size was expected to affect the graft oxygenation state, hepatic SO₂ was fairly independent of the graft-to-recipient weight ratio. In two cases with markedly low hepatic SO₂, postoperative graft dysfunction occurred. This study suggest that the method of near infrared spectroscopy is reliable and useful for assessing the graft oxygenation state in liver transplantation.     

Intraoperative reperfusion assessment of human pancreas allografts using hyperspectral imaging (HSI)

BackgroundThe most common causes of early graft loss in pancreas transplantation are insufficient blood supply and leakage of the intestinal anastomosis. Therefore, it is critical to monitor graft perfusion and oxygenation during the early post-transplant period. The goal of our pilot study was to evaluate the utility of hyperspectral imaging (HSI) in monitoring the microcirculation of the graft and adequate perfusion of the intestinal anastomosis during pancreatic allotransplantation.MethodsWe imaged pancreatic grafts and intestinal anastomosis in real-time in three consecutive, simultaneous pancreas-kidney transplantations using the TIVITA^® HSI system. Further, the intraoperative oxygen saturation (StO₂), tissue perfusion (near-infrared perfusion index, NIR), organ hemoglobin index (OHI), and tissue water index (TWI) were measured 15 minutes after reperfusion by HSI.ResultsAll pancreas grafts showed a high and homogeneous StO₂ (92.6%±10.45%). Intraoperative HSI analysis of the intestinal anastomosis displayed significant differences of StO₂ (graft duodenum 67.46%±5.60% vs. recipient jejunum: 75.93%±4.71%, P<0.001) and TWI {graft duodenum: 0.63±0.09 [I (Index)] vs. recipient jejunum: 0.72±0.09 [I], P<0.001}. NIR and OHI did not display remarkable differences {NIR duodenum: 0.68±0.06 [I] vs. NIR jejunum: 0.69±0.04 [I], P=0.747; OHI duodenum: 0.70±0.12 [I] vs. OHI jejunum: 0.68±0.13 [I], P=0.449}. All 3 patients had an uneventful postoperative course with one displaying a Banff 1a rejection which was responsive to steroid treatment.ConclusionsOur study shows that contact-free HSI has potential utility as a novel tool for real-time monitoring of human pancreatic grafts after reperfusion, which could improve the outcome of pancreas transplantation. Further investigations are required to determine the predictive value of intraoperative HSI imaging.     

Microcirculatory changes in right lobe grafts in living-donor liver transplantation: a near-infrared spectrometry study

BACKGROUND: A continuing shortage of cadaveric liver even for adult patients has motivated not a few centers to proceed to living-donor liver transplantation using right lobe grafts. One of controversies is potential congestion in the graft anterior segment by the deprivation of the middle hepatic vein. METHODS: Hepatic tissue oxygenation and hemoglobin concentration were investigated with a near-infrared spectroscopy in the course of harvesting and implantation in living-donor liver transplantation. Twenty adult recipients of right lobe graft were involved in the study. The aim of the analysis was to detect tissue congestion or ischemia. RESULTS: No significant change in mean hepatic tissue oxygenation and hemoglobin was noted in the right lobe during donor operation even after hepatic parenchymal transection, although some trend for relative congestion, i.e., increased tissue hemoglobin, compared with the left lobe was observed. After graft reperfusion in the recipient, both mean hepatic tissue oxygen saturation and hemoglobin decreased significantly in the anterior segment, which was accompanied by increased heterogeneity of tissue hemoglobin and oxygenation. Increased heterogeneity of oxygenation and decreased tissue hemoglobin were observed also in the posterior segment. CONCLUSIONS: The anterior segment in right lobe living-donor liver transplantation is sensitive to ischemia, rather than congestion, at least in the immediate phase after graft reperfusion. The anterior segment seems to be also more prone to circulatory disturbance than the other part of the graft.     

Kidney transplantation from non-heart-beating donors after oxygenated low-flow machine perfusion preservation with histidine–tryptophan–ketoglutarate solution

The aim of this study was to determine the potential benefit of aerobic machine preservation (MP) with non-colloidal histidine–tryptophan–ketoglutarate (HTK) solution compared with MP with Belzer machine perfusion solution (MPS) and standard cold storage, after marginal kidneys had been obtained from non-heart-beating donors. Cardiac arrest was electrically induced in anaesthetized German landrace pigs (20–25 kg bw). Their kidneys were harvested 40 min thereafter, flushed with HTK by gravity of 100 cm H₂O via the renal artery and then stored in HTK for 18 h at 4°C. Other organs were subjected to oxygenated (pO₂>500 mmHg) hypothermic pulsatile low-flow machine perfusion with HTK or MP with Belzer MPS at P_max=40 mmHg, yielding transrenal flow values of 0.2–0.3 ml/min per g with HTK and approximately twice that amount with Belzer MPS. A well-preserved vascular endothelium and intact tubular epithelium were documented by electron microscopy at the end of perfusion preservation in both solutions as well as after cold storage. Concentrations of ATP (in micromoles per gramme) in tissue homogenates at the end of perfusion preservation with HTK were 1.18±0.12 vs 0.16±0.02 (P<0.05) after simple cold storage and 2.43±0.23 after perfusion with Belzer MPS, thus documenting a relevant effect of low-flow perfusion on tissue oxygenation. Viability of the grafts was followed for 1 week after heterotopic transplantation and bilateral nephrectomy in the recipient pigs. Machine perfusion with HTK significantly improved cortical microcirculation upon early reperfusion in vivo, as well as maximal serum levels of urea and creatinine, compared to recipients receiving cold-stored grafts. No differences could be found between MP with HTK or Belzer MPS. In conclusion, provision of oxygen during storage is possible by low-flow perfusion with HTK as with Belzer MPS and apparently improves graft viability after transplantation.     

Metabolic monitoring during continuous warm- and cold-blood cardioplegia by means of myocardial tissue pH and Po2

Objectives

To study the changes in myocardial tissue pH and Po₂ during cold- and warm-blood cardioplegic arrests.

Design

An experimental study in dogs.

Methods

Nine dogs underwent the following procedures: 30 minutes with an empty heart beating under cardiopulmonary bypass (control period); 30 minutes of warm (33 °C) cardioplegic arrest with a 1:4 mix of crystalloid in blood solution administered continuously at 150 mL/min; 30 minutes of cold (15 °C) cardioplegic arrest; and 30 minutes of myocardial reperfusion. The cardioplegic blood solution was administered antegradely through the ascending aorta.

Main outcome measures

Tissue pH and Po₂. Arterial and coronary sinus oxygen content and myocardial consumption calculated.

Results

There was a modest but significant increase in the left anterior descending (LAD) and circumflex (Cx) tissue pH throughout the experiment. Pmo₂ in the LAD territory averaged 44 (7) mm Hg (mean and standard error of the mean) during the bypass period, 123 (23) mm Hg at the termination of warm cardioplegic arrest, 146 (28) mm Hg at the end of cold arrest and 66 (17) mm Hg after reperfusion. Oxygen consumption averaged 0.65 (0.15) mL/min during the bypass period, 0.3 (0.18) mL/min at the end of warm arrest, 0.25 (0.16) mL/min at the end of cold arrest and 0.45 (0.08) mL/min after reperfusion (p < 0.05). Oxygen delivery to the LAD territory was greater than myocardial oxygen consumption by an average of 2.02 (0.4) mL/min during bypass, 2.02 (0.62) mL/min after warm arrest, 2.12 (0.5) mL/min after cold arrest and 1.55 (0.25) mL/min after reperfusion (p > 0.05).

Conclusions

During cardioplegic arrest, tissue Po₂ increased and oxygen consumption decreased significantly, whereas tissue pH remained normal, suggesting that continuous warm- and cold-blood cardioplegia maintained aerobic glycolysis during myocardial arrest. Thus, the increase in myocardial tissue Pmo₂ during cardioplegic arrest reflects the decrease in myocardial oxygen consumption while maintaining oxygen supply.     

Effects of lumbar puncture position on arterial blood gases

We observed the changes in partial pressure of arterial oxygen (Pao ₂) and carbon dioxide (Paco ₂) before and during assumption of the lateral position prior to lumbar puncture in 81 patients to investigate whether lung volume decreased and ventilation was suppressed. Pao ₂ significantly decreased while the patients were in the lateral position, while Paco ₂ remained unchanged. There was a negative correlation between the change in Pao ₂ and age [change in Pao ₂ (mmHg)=−0.13×age (years)+4.28,P<0.01]. The fact that closing volume increases with age implies that the decrease in functional residual capacity in the lateral position could have caused the decrease in Pao ₂. It is therefore advisable to continuously monitor arterial oxygenation using a noninvasive monitor, such as a pulse oximeter, while performing spinal or epidural block, especially in elderly patients.     

Hypothermic reconditioning after cold storage improves postischemic graft function in isolated porcine kidneys

Delayed graft function still represents a major complication in clinical kidney transplantation. Here we tested the possibility to improve functional outcome of cold stored kidneys a posteriori by short‐term hypothermic machine perfusion immediately prior to reperfusion. A total of 18 kidneys from female German Landrace pigs was flushed with Histidine‐Tryptophan‐Ketoglutarate solution and cold‐stored for 18 h (control). Some grafts were subsequently subjected to 90 min of hypothermic reconditioning by hypothermic machine perfusion with (HR+O₂) or without (HR?O₂) oxygenation of the perfusate. Early graft function of all kidneys was assessed thereafter by warm reperfusion in vitro (n = 6, respectively). Renal function upon reperfusion was significantly enhanced by HR+O₂ with more than threefold increase in renal clearances of creatinine and urea. HR+O₂ also led to significantly higher urinary flow rates and abrogated the activation of caspase 3. By contrast, HR?O₂ was far less effective and only resulted in minor differences compared to control. It is derived from the present data that initial graft function can be significantly improved by 2 h of oxygenated machine perfusion after arrival of the preserved organ in the transplantation clinic.     

Effects of halothane and hypoxia on hepatic oxygen metabolism in the dog

Hepatic oxygen delivery and consumption were assessed in mongrel dogs receiving 2MAC of halothane combined with graded hypoxic hypoxemia (21–8% oxygen). Hepatic blood flow was measured using electromagnetic flowmetry; hepatic oxygen delivery and consumption were calculated from measured hepatic blood flow and oxygen content in hepatic arterial, portal venous and hepatic venous blood. In hypoxia-halothane group, total hepatic blood flow decreased at mild hypoxia (15% O₂) from control value, but recovered to control level at moderate hypoxia (10% O₂), then again decreased at 8% O₂. Oxygen supply to the liver was decreased with the augmentation of hypoxia in hypoxia-halothane and hypoxia-alone groups, and it was significantly lower in the hypoxia-halothane group at 15 and 12% O₂. Hepatic oxygen consumption also decreased from air control values with the increment of hypoxia, but there was no significant difference between the groups. Arterial ketone body ratio, which indicates mitochondrial energy charge level, decreased with the development of hypoxia but there was no significant difference in this ratio between the groups. These results show that halothane aggravated oxygen supply to the liver at mild to moderate hypoxia (15–12% O₂), but did not worsen it specifically at more serious hypoxia (10–8% O₂) compared with hypoxia alone. Hepatic hypoxia itself could not thus be a main cause of halothane hepatotoxicity.(Matsumoto N, Hori T, Miyazaki T et al.: Effects of halothane and hypoxia on hepatic oxygen metabolism in the dog. J Anesth 3: 27–34, 1989)     

Administration of prostacyclin after liver transplantation: a placebo controlled randomized trial

The shortage of suitable organs for liver grafts is responsible for the use of marginal donors for liver transplantation (OLT). If these liver grafts function poorly initially after OLT, a supportive therapy is necessary. The purpose of this study was to evaluate the effects of prostacyclin (PGI2) on postoperative liver graft function after OLT. A total of 30 adult recipients of primary OLT were randomized to either receive PGI2 (4 ng/kg per min body weight, n = 15) or a placebo for 6 d. To evaluate regional splanchnic oxygenation a fiberoptic pulmonary-artery catheter was inserted into a hepatic vein and the difference between mixed venous oxygen content and hepatic venous oxygen content was determined (deltaO2). Measurements were performed directly after transplantation and at 6, 12, 24 and 48 h postoperatively. A significant correlation between deltaO2 and the level of transaminases (ALT/AST) was observed 24 and 48 h after transplantation (p < 0.05). PGI2 treatment induced a significant decrease in deltaO2 after 24 and 48 h after reperfusion (p < 0.05). Peak AST levels tended to be lower in the PGI2 treatment group (418 +/- 99 vs. 638 +/- 156 U/L, p < 0.1). These results suggest that administration of PGI2 after OLT improves hepatic-splanchnic oxygenation and may thereby reduce reperfusion injury after OLT.     

Hydrogen Gas Ameliorates Hepatic Reperfusion Injury After Prolonged Cold Preservation in Isolated Perfused Rat Liver

Hydrogen gas reduces ischemia and reperfusion injury (IRI) in the liver and other organs. However, the precise mechanism remains elusive. We investigated whether hydrogen gas ameliorated hepatic I/R injury after cold preservation. Rat liver was subjected to 48‐h cold storage in University of Wisconsin solution. The graft was reperfused with oxygenated buffer with or without hydrogen at 37° for 90 min on an isolated perfusion apparatus, comprising the H₂(+) and H₂(?) groups, respectively. In the control group (CT), grafts were reperfused immediately without preservation. Graft function, injury, and circulatory status were assessed throughout the perfusion. Tissue samples at the end of perfusion were collected to determine histopathology, oxidative stress, and apoptosis. In the H₂(?) group, IRI was indicated by a higher aspartate aminotransferase (AST), alanine aminotransferase (ALT) leakage, portal resistance, 8‐hydroxy‐2‐deoxyguanosine‐positive cell rate, apoptotic index, and endothelial endothelin‐1 expression, together with reduced bile production, oxygen consumption, and GSH/GSSG ratio (vs. CT). In the H₂(+) group, these harmful changes were significantly suppressed [vs. H₂(?)]. Hydrogen gas reduced hepatic reperfusion injury after prolonged cold preservation via the maintenance of portal flow, by protecting mitochondrial function during the early phase of reperfusion, and via the suppression of oxidative stress and inflammatory cascades thereafter.     

Donation After Cardiac Death: Dynamic Graft Reconditioning During or After Ischemic Preservation?

The benefit of gaseous oxygenation during storage of liver grafts from donors after cardiac death should be investigated as applied either during the whole period of preservation or only for the last 2 h prior to reperfusion. Rat livers were explanted 30 min after cardiac arrest of the donor and cold-stored (CS) for 20 h. Some grafts were subjected to venous systemic oxygen persufflation (VSOP) either for 20 h or for only 2 h subsequent to 18 h of CS. Viability of the livers was assessed thereafter by warm reperfusion in vitro. Twenty hours VSOP and 18 h CS + 2 h VSOP prevented mitochondrial protein breakdown of mitochondrial heat shock protein 70 and promoted a significant and approximately twofold increase in hepatic oxygen consumption, bile production, and energetic recovery upon warm reperfusion. No differences were seen whether VSOP was performed for 20 h or for only 2 h prior to reperfusion. Both techniques significantly abrogated parenchymal enzyme loss (alanine aminotransferase, aspartate aminotransferase) upon reperfusion compared with simple 20 h CS. An increase in perfusate levels of the mitochondrial enzyme glutamate dehydrogenase was observed only in the 20 h VSOP group. In conclusion, viability of donation after cardiac death liver grafts can still be augmented, similarly to continuous aerobic storage, by only endischemic reconditioning, both protocols preventing initial mitochondrial dysfunction and subsequent tissue injury.     

Bosentan, an endothelin antagonist, augments hepatic graft function by reducing graft circulatory impairment following ischemia/reperfusion injury

Endothelin is a potent hepatic vasoconstrictor. We evaluated the role of an endothelin antagonist in hepatic ischemia/reperfusion injury. Bosentan, a novel endothelin receptor antagonist, was infused directly into the portal vein prior to cold ischemia and immediately on reperfusion, in five porcine livers. Five other pigs underwent routine liver harvest and reperfusion without bosentan treatment. Hepatic vascular resistance and liver tissue blood flow, as measured by thermistor flow probes, were determined following reperfusion. Hepatocellular damage was assessed through hepatic venous levels of sorbitol dehydrogenase and lactate dehydrogenase. Endothelial cell damage was determined in sections immunostained for factor VIII. Graft function was determined through oxygen consumption, bile production, and response to bile acid challenge. Organs treated with bosentan demonstrated lower vascular resistance and enhanced tissue blood flow (P <0.05) as compared to untreated organs. Portal vein inflow to hepatic tissue was significantly enhanced (4.4-fold) in the bosentan-treated organs (P <0.05). No difference was observed in hepatocellular damage. Pathology scores for factor VIII immunohistochemical staining were 2.3-fold higher in the bosentan-treated livers as compared to untreated livers (P <0.05). The bosentantreated livers also demonstrated enhanced oxygen consumption, increased bile production, and augmented biliary response to a bile acid challenge (P <0.05). These results indicate that administration of bosentan before and after ischemia/reperfusion reduces hepatic circulatory disturbances, diminishes endothelial cell damage, and augments hepatic graft function. Presented at the Forty-First Annual Meeting of The Society for Surgery of the Alimentary Tract, San Diego, Calif., May 2l–24, 2000.     

Brain tissue pO2 in relation to cerebral perfusion pressure,TCD findings and TCD-CO2-reactivity after severe head injury

Summary As a reliable continuous monitoring of cerebral blood flow and/or cerebral oxygen metabolism is necessary to prevent secondary ischaemic events after severe head injury (SHI) the authors introduced brain tissue pO₂ (ptiO₂) monitoring and compared this new parameter with TCD-findings, cerebral perfusion pressure (CPP) and CO₂-reactivity over time on 17 patients with a SHI. PtiO₂ reflects the balance between the oxygen offered by the cerebral blood flow and the oxygen consumption by the brain tissue. According to TCD-CO₂reactivity PtiO₂-CO₂-reactivity was introduced.After initally (day 0) low mean values (ptiO₂ 7.7 +/–2.6 mmHg, TCD 60.5 +/–32.0 cm/sec and CPP 64.5 +/–16.0 mmHg/, ptiO₂ increased together with an increase in blood flow velocity of the middle cerebral artery and CPP. The relative hyperaemic phase on days 3 and 4 was followed by a decrease of all three parameters. Although TCD-CO₂-reactivity was except for day 0 (1.4+/–1.5%), sufficient. ptiO₂-CO₂-reactivity sometimes showed so-called paradox reactions from day 0 till day 3, meaning an increase of ptiO₂ on hyperventilation. Thereafter ptiO₂-CO₂-reactivity increased, increasing the risk of inducing ischaemia by hyperventilation.The authors concluded that ptiO₂-monitoring might become an important tool in our treatment regime for patients requiring haemodynamic monitoring.     

Effect of halothane and enflurane on hepatic blood flow and oxygen consumption in dogs

We investigated the relative effects of 0.5, 1.0, 1.5, 2.0 MAC halothane and enflurane, and concurrent noxious stimulus on hepatic blood flow and oxygen consumption in 14 mongrel dogs randomly divided into groups of seven each. Hepatic arterial and portal venous blood flow (HABF and PVBF, respectively) were measured continuously using ultrasonic transit time flow meter. Mean arterial blood pressure (MAP), cardiac index (CI), hepatic oxygen supply, and hepatic oxygen consumption (H _{O 2}) were measured. Halothane significantly deceased HABF, but not PVBF in a dose dependent manner. Enflurane did not affect HABF and PVBF significantly. MAP and CI decreased in both groups, with halothane producing more marked decreases than enflurane. H _{O 2} did not change with enflurane, but did with halothane, producing significant differences, with halothane being greater at 1.5, 2.0 MAC. A noxious stimulus only caused minor change in blood flow. The results suggest that liver blood flow and oxygen consumption are affected differently by halothane and enflurane and that halothane has a stronger tendency to cause an imbalance between liver oxygen supply and consumption than dose enflurane.(Masaki E, Yasuda N, Tanifuji Y et al.: Effect of halothane and enflurane on hepatic blood flow and oxygen consumption in dogs. J Anesth 3: 118–122, 1989)     

Role of erythrocytes in short‐term rewarming kidney perfusion after cold storage

Short term normothermic reconditioning by machine perfusion after cold storage has shown beneficial effects in renal transplantation models. Systematic investigations concerning the inclusion of washed erythrocytes as oxygen carriers are lacking in this context. Porcine kidneys were subjected to 20 h of static cold storage. Prior to reperfusion, grafts were put on a machine for 2 h of oxygenated (95% O₂; 5% CO₂) rewarming perfusion. In one group (n = 6) washed erythrocytes were added to the perfusate after temperature has reached 20°C; the other group (n = 6) was run without additives. Control kidneys (n = 6) were immediately reperfused without treatment. Upon reperfusion in vitro, a more than twofold improvement of renal clearance of creatinine, urinary protein loss, fractional excretion of sodium, efficiency of oxygen utilization (TNa/VO₂) and a significant reduction of innate immune activation (HMGB1, tenascin C, expression of TLR4) was seen after machine perfusion, compared with the controls. However, no advantage could be obtained by the addition of erythrocytes and inner cortical tissue pO₂ always remained above normal values during cell‐free machine perfusion. Our data strongly argue in favor of a rewarming perfusion of cold stored donor kidneys but do not substantiate an indication for adding oxygen carriers in this particular setting.     

A comparison of the effects of hyperbaric oxygen culture on survival of murine and canine thyroid gland grafts

Canine thyroid tissue (CTy) was subjected to hyperbaric oxygen culture (HOC) under conditions that affect immunoalteration in murine thyroid tissue (MTy). Survival of autografts and allografts implanted under the kidney capsule was determined after 21 days by ¹²⁵I uptake and histology. Unlike MTy, autograft CTy subjected to normothermic HOC (95% O₂, 5% CO₂; 1.76kg/cm²) for 48 h did not survive (0/8) whereas decrease of culture duration to 24 h resulted in autograft CTy survival (3/3). Under hypothermia (5°C), HOC could be extended to 7 days with autograft CTy survival (3/3 after 4 days and 3/3 after 7 days). Allograft CTy after 24 h of normothermic HOC and 7 days of hypothermic HOC was rejected. Indicators of oxygen free radical injury were determined: catalase activity was comparable in MTy and CTy (means 14.82 and 6.3–10.8 mm/mg protein, respectively) but superoxide dismutase activity was low in CTy (means 0.01–0.29 and 4.75 U/mg protein, respectively). Malondialdehyde content after 48 h of normothermic HOC was higher in CTy than in MTy (means 2215 and 1275 nmol/g, respectively). The results show that CTy is injured by HOC under conditions tolerated by MTy, and that this difference is related to the greater sensitivity of CTy to oxygen free radical injury.     

Effects ofl-arginine andN-nitro-l-arginine treatment on hemodynamics, DO2, VO2, and extravascular lung water in a dog endotoxin shock model

To verify the effect of nitric oxide pathway modification during sepsis, experiments were conducted in four groups of anesthetized dogs which received lipopolysaccharide (LPS) intravenously (group 1), 300 mg·kg⁻¹ ofl-arginine plus LPS (group 2), 20 mg·kg⁻¹ ofN-nitro-l-arginine plus LPS (l-NNA, group 3), and normal saline as the control group. Hemodynamic and oxygenation data as well as extravascular lung water (EVLW) were measured or calculated. The results showed thatl-arginine increases cardiac output index (CI) and decreased the peripheral vascular resistance index (PVRI) without a significant influence on oxygen extraction ratio (O₂ER), oxygen delivery (DO₂), or oxygen consumption (VO₂). All of the untoward hemodynamic effects of LPS were exacerbated by the addition ofl-NNA. Therefore, as DO₂ was significantlys decreased byl-NNA, and although O₂ER was increased (insufficiently), VO₂ was still decreased significantly. EVLW was markedly increased byl-NNA. These results support the hypothesis that inhibition of nitric oxide synthesis may exacerbate hemodynamic and oxygenation consequences in septic shock.