Liposome‐Encapsulated Hemoglobin Ameliorates Ischemic Stroke in Nonhuman Primates: Longitudinal Observation

Liposome‐encapsulated hemoglobin (LEH) is protective early after brain ischemia in rats and nonhuman primates, but it remains unclear whether the protection persists and confers any benefits beyond the acute phase of brain ischemia and reperfusion. Ten monkeys underwent middle cerebral artery occlusion, received LEH (2 mL/kg, n = 5) or saline (2 mL/kg, n = 5) 5 min later, and reperfusion 3 h later. Positron emission tomography studies were repeated for the cerebral metabolic rate of O₂ (CMRO₂) as well as glucose (CMRglc) up to 8 days after reperfusion, when the animals were euthanized for morphological studies. There was no difference in O₂ metabolism until 3 h after reperfusion, when CMRO₂ was significantly better preserved in the cortex, but not in basal ganglia, on Day 0 in LEH‐treated monkeys. The extent of cortical infarction (saline 68 ± 10% vs. LEH 38 ± 9%, P < 0.05) and CMRO₂ (mild suppression: saline 34 ± 10% vs. LEH 14 ± 4%, P < 0.05) remained significantly better preserved 8 days later, when CMRglc showed a similar pattern of cortical protection (mild suppression: saline 49 ± 15% vs. LEH 37 ± 4%, P < 0.05) in LEH‐treated monkeys, together with regained body weight. Somatic weight control, morphological integrity, CMRO₂, and CMRglc were better preserved immediately, as well as 8 days after occlusion and reperfusion of the middle cerebral artery in monkeys receiving LEH early after onset of ischemia.     

Liposome-encapsulated hemoglobin alleviates hearing loss after transient cochlear ischemia and reperfusion in the gerbil

To test liposome‐encapsulated hemoglobin (LEH) in transient cochlear ischemia/reperfusion as a model of sudden deafness, Mongolian gerbils were randomly assigned to receive 2 mL/kg of either low‐affinity LEH (l‐LEH, P₅₀O₂ = 40 mm Hg), high‐affinity LEH (h‐LEH, P₅₀O₂ = 10 mm Hg), homologous red blood cells (RBCs), or saline (each group n = 6) 30 min before 15‐min occlusion of the bilateral vertebral arteries and reperfusion. Sequential changes in hearing were assessed by auditory brain response 1, 4, and 7 days after ischemia/reperfusion, when the animals were sacrificed for pathological studies. h‐LEH was significantly more protective than l‐LEH in suppressing hearing loss, in contrast to RBC or saline treatment, at 8, 16, and 32 kHz, where hearing loss was most severe (P < 0.05 between any two groups) on the first day after cochlear ischemia/reperfusion. Thereafter, hearing loss improved gradually in all groups, with a significant difference among groups up to 7 days, when morphological studies revealed that the inner hair cells but not the outer hair cells, were significantly lost in the groups in the same order. The results suggest that pretreatment with h‐LEH is significantly more protective than l‐LEH in mitigating hearing loss and underlying pathological damage, in contrast to transfusion or saline infusion 7 days after transient cochlear ischemia/reperfusion.     

Liposome‐Encapsulated Hemoglobin Improves Tumor Oxygenation as Detected by Near‐Infrared Spectroscopy in Colon Carcinoma in Mice

Liposome‐encapsulated hemoglobin (LEH) with high (h‐LEH, P₅₀O₂ = 10 mm Hg) or low O₂ affinity (l‐LEH, P₅₀O₂ = 40 mm Hg) may improve O₂ delivery to sensitize tumor tissues for radiotherapy. A total of 10 mL/kg of h‐LEH, l‐LEH, red blood cells (RBCs), or saline was infused in mice transplanted with murine colon carcinoma with near‐infrared spectroscopy (NIRS) detectors set at the tumor (right leg) and intact muscle (left leg). NIRS recorded changes in the amount of oxyhemoglobin (oxyHb), deoxyhemoglobin (deoxyHb), and their sum (tHb) with the animals spontaneously breathing room air (10 min), pure O₂ (5 min), and then back to room air. The tumor was finally excised for histological examination. In mice treated with h‐LEH, tHb significantly increased compared to mice receiving other solutions. The magnitude was significantly attenuated in the tumor compared to the intact muscle under room air. Reciprocal changes in oxyHb and deoxyHb between intact muscle and tumor in response to infused solutions allowed assumption of average tissue PO₂ between 30 and 40 mm Hg in muscle and at around 10 mm Hg in tumor. While O₂ respiration increased oxyHb and decreased deoxyHb both in muscle and tumor, their sum or tHb consistently decreased in muscle and increased in tumor regardless of preceding infusion. Such responses were totally reversed when mice were placed under hypoxia (10% O₂), suggesting that a lack of physiological circulatory regulation in tumor may account for heavier immunohistochemical staining for human hemoglobin in tumors of mice treated with h‐LEH than with l‐LEH. The results suggest that h‐LEH may cause significant tumor oxygenation compared to RBC, l‐LEH, or saline probably due to its nanometer size (vs. RBC) and high O₂ affinity (vs. l‐LEH) without increasing O₂ content in the intact tissue (vs. O₂ respiration) probably due to a lack of physiological circulatory regulation.     

Effects of Liposome‐Encapsulated Hemoglobin on Gastric Wound Healing in the Rat

Liposome‐encapsulated hemoglobin (LEH) may improve microcirculation and oxygen (O₂) metabolism at a surgical wound to accelerate its healing. Ten mL/kg of LEH with high (h‐LEH) or low O₂‐affinity (l‐LEH), homologous red blood cells (RBC), empty liposome or saline as a control was infused before a 10‐mm incision and interrupted suture closure of the gastric wall in a total of 110 rats. Two and 4 days later, the stomach was excised for bursting pressure determination and histological sampling. The dose–response relationship was examined in 70 additional rats receiving progressively reduced doses of h‐LEH. Hypoxia‐inducible factor‐1α (HIF‐1α) was stained immunohistochemically in 54 other rats to examine its accumulation at the anastomotic sites. Bursting pressure of the surgical wound was significantly higher 2 days after surgery only in the h‐LEH‐treated rats (P < 0.05), but not at 4 days after surgery, when other rats showed increased bursting pressure to a nonsignificant level. Histological examination revealed less granulocyte infiltration, better granulation, and more macrophage infiltration in h‐LEH‐treated rats at 2 days, but no longer at 4 days postsurgery. Dose–response study revealed that 0.4 mL/kg of h‐LEH (hemoglobin 24 mg/kg) was effective for elevating bursting pressure at 2 days. h‐LEH‐treated rats had significantly suppressed HIF‐1α accumulation in the wound 6, 24, and 48 h after surgery as compared with control animals treated with homologous RBC or saline. In conclusion, the results suggest that h‐LEH, but not l‐LEH or homologous transfusion, may accelerate wound healing early after gastric incision and anastomosis in the rat. The mechanism(s) appears to be related to improved O₂ supply, aerobic metabolism, and suppressed inflammation in the wound.     

Liposome-encapsulated hemoglobin ameliorates tumor hypoxia and enhances radiation therapy to suppress tumor growth in mice

We hypothesize that liposome‐encapsulated hemoglobin with high O₂ affinity (P₅₀0₂ = 12 mm Hg, h‐LEH) may increase O₂ delivery to hypoxic tumors and enhance radiation therapy synergistically to suppress tumor growth. First, h‐LEH (5, 10, and 20 mL/kg) was intravenously infused 30 min before radiation (20 Gy) of SCCVII tumor grown in C3H/HeN mice. Second, 10 mL/kg of h‐LEH was administered 30, 60, 90, and 120 min prior to radiation to determine optimal timing. Tumor size was monitored thereafter to titrate tumor growth suppression. Third, additional mice with SCCVII tumor were infused with h‐LEH or empty liposome (EL), and tumors were excised at various time points for immunohistochemical examination of h‐LEH and hypoxia‐inducible factor‐1α (HIF‐1α). h‐LEH was most effective at 10 mL/kg in comparison to 5 or 20 mL/kg of h‐LEH or EL. Tumor growth was most suppressed when the interval between h‐LEH infusion and radiation was shortest, 30 min. As a result, 10 mL/kg of h‐LEH infusion 30 min prior to radiation prolonged 5‐fold tumor‐growth time from 20.0 days (radiation and EL) to 26.5 days, P < 0.01, synergy ratio 1.42. While human hemoglobin (h‐LEH) was detected in tumors 0.5 to 24 h after administration, HIF‐1α accumulation was sparse and became significantly reduced compared to controls 48 and 72 h after h‐LEH infusion. h‐LEH (10 mL/kg) was highly effective in enhancing radiation therapy synergistically under ambient respiration against tumor growth in mice. Decreased accumulation of HIF‐1α in h‐LEH‐treated tumor may suggest targeted tumor oxygenation as a potential mechanism.     

Hydrogen Gas Does Not Ameliorate Renal Ischemia Reperfusion Injury in a Preclinical Model

In renal transplantation, ischemia reperfusion injury impairs early graft function and can reduce long term graft survival. Hydrogen has antioxidant and anti‐inflammatory properties that can reduce the effects of ischemic injury. The aim of this study was to examine the effects of hydrogen gas administered during reperfusion in a preclinical model of kidney ischemia reperfusion injury. Porcine kidneys underwent 15 min of warm ischemia followed by 22 h of cold ischemia. They were then reperfused for 6 h with whole autologous blood on an ex vivo reperfusion circuit. Paired kidneys were randomized to control (n = 6) (25% oxygen, 5% carbon dioxide, 70% nitrogen) or hydrogen (n = 6) (2% hydrogen, 25% oxygen, 5% carbon dioxide, 68% nitrogen) groups. Tissue, urine, and blood samples were collected at baseline and hourly throughout the reperfusion period. Baseline measurements were similar across groups. Following perfusion, there was no significant difference between control and hydrogen groups in urine output (693 mL vs. 608 mL, P = 0.86), renal blood flow (105.9 vs. 108 mL/min/100g, P = 0.89), acid‐base homeostasis, or creatinine clearance. There was a significant increase in cytokine levels from baseline to 6 h in both groups (IL‐1β P = 0.002; IL‐6 P = 0.004; IL‐8 P = 0.002). However, there were no significant differences in levels of inflammatory cytokines (IL1β, IL‐6, and IL‐8) between the groups. The administration of hydrogen gas did not improve renal function, reduce oxidative damage, or inflammation during the reperfusion of ischemically damaged kidneys.     

Liposome-Encapsulated Hemoglobin Alleviates Brain Edema After Permanent Occlusion of the Middle Cerebral Artery in Rats

Liposome-encapsulated hemoglobin (LEH) was proven to be protective in cerebral ischemia/reperfusion injury. The present study evaluated LEH in a rat model of permanent middle cerebral artery (MCA) occlusion to clarify its effect during ischemia and reperfusion. Five minutes after thread occlusion of the MCA, rats were infused with 10 mL/kg of LEH (LEH, n  = 13), and compared with normal controls ( n  = 11). Additional animals received the same MCA occlusion with no treatment (CT, n  = 11), saline (saline, n  = 10), empty liposome solution (EL, n  = 13), or washed red blood cells (RBC, n  = 7). Severity of brain edema was determined 24 h later by signal strength in T2-weighted magnetic resonance imaging of the cortex, striatum, hippocampus, and pyriform lobe. The results showed that brain edema/infarction observed in any vehicle-infused control was significantly more severe than in LEH-treated rats. There was a tendency toward aggravated edema in rats receiving ELs. LEH infusion at a dose of 10 mL/kg significantly reduced edema formation as compared to other treatments in a wide area of the brain 24 h after permanent occlusion of the MCA. Low oncotic pressure of EL and LEH solution (vehicle solution) appeared to cause nonsignificant aggravation of edema and reduced protective effects of LEH.     

Refractory Pulmonary Edema and Upper Body Hypoxemia During Veno‐Arterial Extracorporeal Membrane Oxygenation—A Case for Atrial Septostomy

Veno‐arterial extracorporeal membrane oxygenation (VA‐ECMO) provides mechanical circulatory support for patients with advanced cardiogenic shock, facilitating myocardial recovery and limiting multi‐organ failure. In patients with severely limited left ventricular ejection, peripheral VA‐ECMO can further increase left ventricular and left atrial pressures (LAP). Failure to decompress the left heart under these circumstances can result in pulmonary edema and upper body hypoxemia, that is, myocardial and cerebral ischemia. Atrial septostomy can decrease LAP in these situations. However, the effects of atrial septostomy on upper body oxygenation remain unknown. After IRB approval, we identified 9 out of 242 adult VA‐ECMO patients between January 2011 and June 2016 who also underwent atrial septostomy for refractory pulmonary edema/upper body hypoxemia. We analyzed LAP/pulmonary capillary wedge pressure (PCWP), right atrial pressures (RAPs), P_aO₂/F_iO₂ ratios (blood samples from right radial artery), intrathoracic volume status, and resolution of pulmonary edema before and up to 48 h after septostomy. There were no procedure‐related complications. Thirty‐day survival was 44%. LAP/PCWP decreased by approximately 40% immediately following septostomy and remained so for at least 24 h. P_aO₂/F_iO₂ ratios significantly increased from 0.49 (0.38–2.12) before to 5.35 (3.01–7.69) immediately after septostomy and continued so for 24 h, 6.6 (4.49–10.93). Radiographic measurements also indicated a significant improvement in thoracic intravascular volume status after atrial septostomy. Atrial septostomy reduces LAP and improves upper body oxygenation and intrathoracic vascular volume status in patients developing severe refractory pulmonary edema while undergoing peripheral VA‐ECMO. Atrial septostomy therefore appears safe and suitable to reduce the risk of upper body ischemia under these circumstances.     

Effects of Liposome‐Encapsulated Hemoglobin on Learning Ability in Tokai High‐Avoider Rat After Total Brain Ischemia and Reperfusion

Liposome‐encapsulated hemoglobin with low O₂‐affinity (l‐LEH) was shown to be protective in focal brain ischemia and reperfusion (I/R) in rats and primates. We tested l‐LEH in the transient whole brain ischemia in the Tokai high‐avoider rat (THA), which has been selected, mated, and bred over 77 generations for a high and consistent learning ability determined by the Sidman avoidance test (SAT). Young/naïve (before SAT) and adult/parent (after SAT) THA rats underwent acute and complete four‐vessel occlusion in the chest for 3 or 5 min, administration of 2 mL/kg of l‐LEH, saline, or homologous washed red blood cells (RBCs), reperfusion, and resuscitation. One week later, all rats underwent SAT, open‐field behavioral observation, Morris water maze tests, and morphological study. Whereas young/naïve rats treated with l‐LEH retained a rapid and consistent learning curve as in nonischemic controls, THA rats treated with RBCs or saline had retarded learning response on SAT as well as reduced cellularity in the amygdala. Adult/parent rats with established memory on SAT maintained perfect achievement even after I/R. In contrast, l‐LEH‐treated rats showed no better performance on Morris water maze (function) or cellularity of the CA1 sector of the hippocampus (morphology) compared with the rats treated with RBCs. Although task performance on SAT and Morris water maze appeared antithetical, morphological observations corresponded to the respective functions, suggesting that l‐LEH was protective only for the amygdala on SAT tasks but not for the CA1 sector of the hippocampus on spatial orientation as in our previous studies on focal brain I/R, where the cortex was preserved better than basal ganglia.     

The effect of ketanserin on cerebral blood flow and oxygen metabolism in healthy volunteers

Summary The effect of the anti-hypertensive agent ketanserin on average global cerebral blood flow (CBF) and average global cerebral oxygen metabolism (CMRO₂) was examined in 8 healthy volunteers. CBF and CMRO₂ were measured with the Kety-Schmidt technique before ketanserin administration (baseline) and after administration of 2 different doses of ketanserin intravenously (dose I: 10 mg bolus and an infusion of 6 mg/h; dose II: 20 mg bolus and an ifusion of 20 mg/ h). Baseline CBF and CMRO₂ were 60 and 3.6 ml/100 g/min, respectively, and were not changed by administration of ketanserin dose I. During administration of dose II, however, CBF fell to 52 ml/ 100 g/min (p=0.05) and CMRO₂ was reduced to 3.2 ml/100 g/min (p < 0.05).We conclude that when administered in a high dose, ketanserin has the ability to depress cerebral oxygen metabolism, but when administered in a clinically relevant dose ketanserin does not influence average global CBF or average global CMRO₂. Ketanserin could be a safe antihypertensive drug in neuroanaesthesia or in the neuro-intesive care unit.     

Liposome-encapsulated hemoglobin accelerates skin wound healing in mice

Effects of liposome‐encapsulated hemoglobin with high O₂ affinity (m‐LEH, P₅₀O₂ = 17 mm Hg) on skin wound healing in mice were examined. Two full‐thickness dorsal wounds 6 mm in diameter encompassed by silicone stents were created in Balb/c mice. Two days later (day 2), the animals randomly received intravenous m‐LEH (2 mL/kg, n = 12), homologous blood transfusion (red blood cell [RBC], n = 11), or saline (n = 12). The same treatment was repeated 4 days after wounding (day 4), and the sizes of the skin defects and ulcers were monitored on days 0, 2, 4, and 7, when all animals were euthanized for morphological studies. While the size of the skin defect in relation to the stent ring remained the same in all groups, the size of the ulcer compared with the skin defect (or silicone stent) became significantly reduced on days 4 and 7 in mice treated with m‐LEH (46 ± 10% of pretreatment size, P < 0.01) compared with mice treated with RBC transfusion (73 ± 6%) or saline (76 ± 7%). m‐LEH treatment significantly accelerated granulation, increased epithelial thickness, suppressed early granulocyte infiltration, and increased Ki67 expression in accordance with the ulcer size reduction, while there was no difference in surface blood flow or CD31 expression among the groups. The results suggest that m‐LEH (2 mL/kg) may accelerate skin wound healing in Balb/c mice via mechanism(s) involving reduced inflammation and increased metabolism, but not by improved hemodynamics or endothelial regeneration.     

Cerebral oxygen metabolism during total body flow and antegrade cerebral perfusion at deep and moderate hypothermia

The aim of this study is to evaluate the effect of temperature on cerebral oxygen metabolism at total body flow bypass and antegrade cerebral perfusion (ACP). Neonatal piglets were put on cardiopulmonary bypass (CPB) with the initial flow rate of 200 mL/kg/min. After cooling to 18°C (n = 6) or 25°C (n = 7), flow was reduced to 100 mL/kg/min (half‐flow, HF) for 15 min and ACP was initiated at 40 mL/kg/min for 45 min. Following rewarming, animals were weaned from bypass and survived for 4 h. At baseline, HF, ACP, and 4 h post‐CPB, cerebral blood flow (CBF) was measured using fluorescent microspheres. Cerebral oxygen extraction (CEO₂) and cerebral metabolic rate of oxygen (CMRO₂) were monitored. Regional cranial oxygen saturation (rSO₂) was continuously recorded throughout the procedure using near‐infrared spectroscopy. At 18°C, CBF trended lower at HF and ACP and matched baseline after CPB. CEO₂ trended lower at HF and ACP, and trended higher after CPB compared with baseline. CMRO₂ at ACP matched that at HF. Cranial rSO₂ was significantly greater at HF and ACP (P < 0.001, P < 0.001) and matched baseline after CPB. At 25°C, CBF trended lower at HF, rebounded and trended higher at ACP, and matched baseline after CPB. CEO₂ was equal at HF and ACP and trended higher after CPB compared with baseline. CMRO₂ at ACP was greater than that at HF (P = 0.001). Cranial rSO₂ was significantly greater at HF (P = 0.01), equal at ACP, and lower after CPB (P = 0.03). Lactate was significantly higher at all time points (P = 0.036, P < 0.001, and P < 0.001). ACP provided sufficient oxygen to the brain at a total body flow rate of 100 mL/kg/min at deep hypothermia. Although ACP provided minimum oxygenation to the brain which met the oxygen requirement, oxygen metabolism was altered during ACP at moderate hypothermia. ACP strategy at moderate hypothermia needs further investigation.     

Mechanisms of Hypothermic Machine Perfusion to Decrease Donation After Cardiac Death Graft Inflammation: Through the Pathway of Upregulating Expression of KLF2 and Inhibiting TGF‐β Signaling

Hypothermic machine perfusion (HMP) has been known as an efficient way to improve kidney graft function, but the underlying mechanisms remain unclear. Here, we adopt a rabbit reperfusion mode to investigate the upstream mechanisms of end‐ischemic HMP of kidneys from donors after cardiac death (DCD), with static cold storage (CS) as a control. Eighteen New Zealand healthy male rabbits (12 weeks old, with a weight of 3.0 ± 0.2 kg) were randomly divided into three groups: HMP group, CS group, and Normal group (n = 6). The left kidney of rabbits underwent warm ischemia for 25 min through clamping the left renal pedicle and then reperfusion for 1 h. Then the left kidneys were preserved by CS or HMP (4°C for 4 h) ex vivo respectively, after they were autotransplanted and rabbits were submitted to a right nephrectomy. Twenty‐four hours after reperfusion, all left renal specimens were collected. Finally, the expression of Krüppel‐like factor 2 (KLF2), transforming growth factor‐β (TGF‐β) and SMAD4 protein in renal cortical tissue were detected by immunoblotting, and the TGF‐β and SMAD4 expressions were further confirmed by immunohistochemistry analysis. We found that expression of KLF2 in HMP group was significantly higher than CS group (P = 0.011), while expression of TGF‐β and SMAD4 in HMP group were significantly lower than CS group (P = 0.002, P = 0.01, respectively); Compared with normal group, the expression of TGF‐β and SMAD4 in HMP and CS group significantly increased (P<0.05). Compared with CS group, TGF‐β and SMAD4 protein were equally down‐regulated in glomerular and the tubular epithelial cells in HMP group confirmed by immunohistochemistry. In conclusion, HMP may decrease DCD kidneys inflammation through the pathway of upregulating expression of KLF2 and inhibiting TGF‐β signaling after transplantation.     

Liposome‐Encapsulated Hemoglobin Accelerates Bronchial Healing After Pneumonectomy in the Rat With or Without Preoperative Radiotherapy

Liposome‐encapsulated hemoglobin (LEH) has been reported to accelerate wound healing in the stomach and skin in an experimental setting. LEH was tested in bronchial anastomotic healing after radiation and pneumonectomy in the rat. Sprague‐Dawley rats (n = 61) received preoperative radiation (20 Gy) to the chest and underwent left pneumonectomy with bronchial stump closure using the Sweet method 4 days later, when they were randomized to receive intravenous infusion of LEH with high O₂ affinity (P₅₀O₂ = 17 mm Hg, 10 mL/kg, n = 32) or saline (n = 29). Additional rats (n = 18) were treated in the same way without preoperative radiation. Bronchial anastomotic healing was evaluated 2 days after surgery by determining the bursting pressure and infiltration of neutrophils, monocytes, and macrophages. Bronchial bursting pressure was elevated in the rats receiving LEH both in the unirradiated group (LEH 212 ± 78 vs. saline 135 ± 63 mm Hg, P < 0.05) and in rats with preoperative radiation (LEH 162 ± 48 vs. saline 116 ± 56 mm Hg, P < 0.01). Moreover, the percentage of rats with bursting pressure <100 mm Hg tended to be smaller in the unirradiated group (LEH 1/9 [11.1%] vs. saline 4/9 [44.4%], NS) and was significantly reduced in irradiated animals (LEH 3/32 [9.4%] vs. saline 11/29 [38%], P < 0.05). There were no morphological differences except for macrophage infiltration to the anastomotic area, which was significantly prominent in the LEH‐treated rats (P < 0.05) regardless of the presence or absence of preoperative irradiation (IR). The results suggest that LEH with high O₂ affinity may improve mechanical strength and morphological findings in bronchial anastomosis in rats regardless of the presence or absence of preoperative IR. The irradiated rats later treated with LEH had equivalent or better bronchial healing than that of saline‐treated naïve animals undergoing pneumonectomy alone.     

Transplantation of Cold Stored Porcine Kidneys After Controlled Oxygenated Rewarming

The concept of “controlled oxygenated rewarming” (COR) using ex vivo machine perfusion after cold storage was evaluated as tool to improve renal graft function after transplantation. Renal function after 20 min warm ischemia and 21 h cold storage was studied in an auto‐transplant model in pigs (25–30 kg, n = 6 per group). In the study group, preimplant ex vivo machine perfusion for 90 min was added after cold storage, including gentle warming up of the graft to 20°C (COR). Kidneys that were only cold stored for 21 h served as controls. In vivo follow up was one week; the remaining native kidney was removed during transplantation. COR significantly improved cortical microcirculation upon early reperfusion and reduced free radical mediated injury and cellular apoptosis. Post‐transplant kidney function (peak levels in serum) was also largely and significantly improved in comparison to the control group. A weak inverse correlation was found between renal flow during COR and later peak creatinine after transplantation (r² = 0.5), better values were seen for oxygen consumption, measured during machine perfusion at 20°C (r² = 0.81). Gentle graft rewarming prior to transplantation by COR improves post‐transplant graft outcome and may also be a valuable adjunct in pretransplant graft assessment.     

Liposome‐Encapsulated Hemoglobin Enhances Chemotherapy to Suppress Metastasis in Mice

Liposome‐encapsulated hemoglobin with high O₂‐affinity (P₅₀O₂ = 10 mm Hg, h‐LEH) was reported to enhance tumor radiosensitivity. We hypothesize that targeted O₂ delivery to tumor hypoxia by h‐LEH may also enhance chemotherapy to suppress tumor growth and metastasis in mice. Doxorubicin (DXR; 0.5 or 2 mg/kg i.p.) or S‐1 (4 or 8 mg/kg orally) alone or in combination with h‐LEH (5 mL/kg i.v.) was administered for 2 weeks to C57BL/6N mice inoculated with Lewis Lung Carcinoma (LLC) in the leg. After the 2‐week therapy in six treatment groups, mice were sacrificed for quantitative assessment of tumor growth and lung metastasis. The tumor was then evaluated for its expression of hypoxia‐inducible factor‐1α (HIF‐1α) and matrix metallopoteinase‐2 (MMP‐2) activity. Combined use of h‐LEH and chemotherapeutic agents (DXR or S‐1) showed no additional enhancement on suppression of the tumor growth over the chemotherapeutic agent alone. However, the combination use of h‐LEH significantly suppressed the number and total area of metastatic colonies in the lung compared with each chemotherapeutic agent alone. Although HIF‐1α expression and MMP‐2 activity in the original tumor was significantly suppressed in the groups of mice treated with either DXR or S‐1 alone, the addition of h‐LEH to either agent showed further enhancement of oxygen‐mediated degradation of HIF‐1α and suppression of MMP‐2 activity. Although the addition of h‐LEH to DXR or S‐1 had little effect on original LLC tumor growth, it significantly enhanced suppression of lung metastasis in mice.     

Clinical significance of STA-MCA double anastomosis for hemodynamic compromise in post-JET/COSS era

Background

Even after the recent randomized clinical trials JET and COSS, it is still unclear that impaired cerebrovascular reactivity (CVR) to acetazolamide and oxygen extraction fraction (OEF) can identify the candidates for superficial temporal artery to middle cerebral artery (STA-MCA) anastomosis. This prospective study was aimed to evaluate the benefits of STA-MCA “double” anastomosis on long-term outcome in patients with reduced cerebral blood flow (CBF) and CVR (Type 3 ischemia) and elevated OEF attributable to occlusive carotid diseases.

Methods

This study included 49 patients with reduced CBF and CVR on SPECT in the ipsilateral MCA area. Using ¹⁵O-gas PET, OEF was also measured in all patients. STA-MCA double anastomosis was recommended to the patients with Type 3 and elevated OEF. Those with Type 3 but normal OEF were medically treated.

Results

Of 36 patients with Type 3 and elevated OEF, 25 consented to surgery. No perioperative morbidity or mortality were noted. The other 11 patients with Type 3 and elevated OEF were medically treated. Annual incidence of ipsilateral stroke was 0.7 % and 6.5 % in surgically and medically treated patients with Type 3 and elevated OEF, respectively (P?=?0.0188). None of patients with Type 3 but normal OEF developed ipsilateral stroke during follow-up periods. STA-MCA “double” anastomosis significantly decreased OEF.

Conclusions

STA-MCA “double” anastomosis may still have the potential to reduce the risk of recurrent ipsilateral stroke in hemodynamically compromised patients. Further studies would be essential to advance diagnosis, surgical procedures, and perioperative managements to bring out maximal effects of bypass surgery.     

Contemporary Oxygenator Design: Shear Stress‐Related Oxygen and Carbon Dioxide Transfer

Design of contemporary oxygenators requires better understanding of the influence of hydrodynamic patterns on gas exchange. A decrease in blood path width or an increase in intraoxygenator turbulence for instance, might increase gas transfer efficiency but it will increase shear stress as well. The aim of this clinical study was to examine the association between shear stress and oxygen and carbon dioxide transfer in different contemporary oxygenators during cardiopulmonary bypass (CPB). The effect of additional parameters related to gas transfer efficiency, that is, blood flow, gas flow, sweep gas oxygen fraction (FiO₂), hemoglobin concentration, the amount of hemoglobin pumped through the oxygenator per minute—Qhb, and shunt fraction were contemplated as well. Data from 50 adult patients who underwent elective CPB for coronary artery bypass grafting or aortic valve replacement were retrospectively analyzed. Data included five different oxygenator types with an integrated arterial filter. Relationships were determined using Pearson bivariate correlation analysis and scatterplots with LOESS curves. In the Capiox FX25, Fusion, Inspire 8F, Paragon, and Quadrox‐i groups, mean blood flows were 4.8 ± 0.9, 5.3 ± 0.7, 4.9 ± 0.7, 5.0 ± 0.6, and 5.7 ± 0.6 L/min, respectively. The mean O₂ transfer/m² membrane surface area was 44 ± 14, 51 ± 9, 60 ± 10, 63 ± 14, and 77 ± 18, respectively, whereas the mean CO₂ transfer/m² was 26 ± 14, 60 ± 22, 73 ± 29, 74 ± 19, and 96 ± 20, respectively. Associations between oxygen transfer/m² and shear stress differed per oxygenator, depending on oxygenator design and the level of shear stress (r = 0.249, r = 0.562, r = 0.402, r = 0.465, and r = 0.275 for Capiox FX25, Fusion, Inspire 8F, Paragon, and Quadrox‐i, respectively, P < 0.001 for all). Similar associations were noted between CO₂ transfer/m² and shear stress (r = 0.303, r = 0.439, r = 0.540, r = 0.392, and r = 0.538 for Capiox FX25, Fusion, Inspire 8F, Paragon, and Quadrox‐i, respectively, P < 0.001 for all). In addition, O₂ transfer/m² was strongly correlated with FiO₂ (r = 0.633, P < 0.001), blood flow (r = 0.529, P < 0.001), and Qhb (r = 0.589, P < 0.001). CO₂ transfer/m² in contrast was predominately correlated to sweep gas flow (r = 0.567, P < 0.001). The design‐dependent relationship between shear stress and gas transfer revealed that every oxygenator has an optimal range of blood flow and thus shear stress at which gas transfer is most efficient. Gas transfer is further affected by factors influencing the O₂ or CO₂ concentration gradient between the blood and the gas compartment.     

Comparison of moderate hyperventilation and mannitol for control of intracranial pressure control in patients with severe traumatic brain injury – a study of cerebral blood flow and metabolism

Summary Objective. To compare the respective effects of established measures used for management of traumatic brain injury (TBI) patients on cerebral blood flow (CBF) and cerebral metabolic rates of oxygen (CMRO₂), glucose (CMRGlc) and lactate (CMRLct). Methods. Thirty-six patients suffering from severe traumatic brain injury (TBI) were prospectively evaluated. In all patients baseline assessments were compared with that following moderate hyperventilation (reducing PaCO₂ from 36 ± 4 to 32 ± 4 mmHg) and with that produced by administration of 0.5 gr/kg mannitol 20% intravenously. Intracranial and cerebral perfusion pressure (ICP, CPP), CBF and arterial jugular differences in oxygen, glucose and lactate contents were measured for calculation of CMRO₂, CMRGlc and CMRLct. Results. Following hyperventilation, CBF was significantly reduced (P < 0.0001). CBF remained most often above the ischemic range although values less than 30 ml·100 gr⁻¹·min⁻¹ were found in 27.8% of patients. CBF reduction was associated with concurrent decrease in CMRO₂, anaerobic hyperglycolysis and subsequent lactate production. In contrast, mannitol resulted in significant albeit moderate improvement of cerebral perfusion. However, administration of mannitol had no ostensible effect either on oxidative or glucose metabolism and lactate balance remained mostly unaffected. Conclusions. Moderate hyperventilation may exacerbate pre-existing impairment of cerebral blood flow and metabolism in TBI patients and should be therefore carefully used under appropriate monitoring. Our findings rather support the use of mannitol for ICP control.     

Ist die hirnvenöse Sauerstoffsättigung ein Maß für die zerebrale Durchblutung?

The arteriovenous oxygen content difference (avDO₂) of the brain is dependent on O₂ consumption (CMRO₂) and cerebral blood flow (CBF). With unchanging arterial O₂ content, avDO₂ is inversely related to cerebral venous O₂ saturation (SO₂). Measurement of SO₂ in the jugular bulb not only provides information about the O₂ balance of the brain, but may give an important estimation of CBF if a clinically useful correlation is proven. The aim of the present study was to verify this aspect. Methods. Sixty-two male patients undergoing coronary revascularisation were investigated. The study was approved by the local Ethical Committee and each patient gave written informed consent on the preoperative day. At four points during the perioperative course arterial and cerebral venous SO₂ and CBF were measured. Cerebral venous blood was sampled from a catheter in the superior bulb of the right internal jugular vein. CBF was measured using the argon wash-in technique. All sampled data were pooled and evaluated. Results. As expected from theory, cerebral venous SO₂ and avDO₂ showed a close linear relationship (r=?0.892). However, only a weak hyperbolic relationship was found between cerebral venous SO₂ and CBF. In addition, no direct correlation between CMRO₂ and SO₂ in the jugular bulb could be demonstrated. Conclusions. In this clinical study, a close relationship between cerebral venous SO₂ and CBF was not found. This was primarily due to the high variability of cerebral O₂ uptake. Changes in cerebral venous SO₂ may therefore not be used as an estimate of perioperative changes in CBF.