Preconditioning for protection from ischemic injury: discriminating cause from effect from epiphenomenon

The Pringle manoeuvre should be avoided in hepatectomy for cancer patients due to its side effects on tumor recurrence and worse prognosis

Curative hepatectomy is still the best therapeutic strategy for liver cancer treatment up to now. The Pringle manoeuvre has been commonly used to avoid massive blood loss during operation since its advent, which greatly accelerates the advance of liver surgery and oncological surgery. In the past century, more attentions have been paid to different effects of ischemia-reperfusion injury elicited by Pringle manoeuvre. Theses include its impacts on complex metabolic, immunological, and microvascular changes, which altogether might contribute to hepatocellular damage and dysfunction, and contribute to haemodynamic instability. Despite these adverse impacts, the short-term outcome of affected patients under hepatectomy was greatly improved with the advances of surgical techniques and perioperative management in recent years. While the long-term prognosis remains unsatisfactory due to a high incidence of intra/extrahepatic recurrence. The reason for it was not totally elucidated. Furthermore, the effect of the Pringle manoeuvre on the prognosis of oncologic patients and behavior of the tumor cell was not deliberately mentioned. This point was put forward to the front-desk by the specific phenomenon from recent animal studies. It is showed that ischemia-reperfusion injury of the liver remnant may be a significant factor to promote the tumor recurrence and metastasis. If it is a truth in human, there must be a big challenge to the Pringle manoeuvre. So we hypothesized that the long-term prognosis of cancer patients could be worsened by the ischemia-reperfusion injury elicited by Pringle manoeuvre during the hepatectomy and it should be revised, or even, avoided in future hepatectomy for oncologic patients. The less surgical stress including ischemia-reperfusion injury in the hepatic resection without Pringle manoeuvre might contribute to a better prognosis. To get a deeper understanding, prospective randomized clinical trials need to be done. It is surely supposed to provide more important information about the long-term effects of the Pringle manoeuvre, and to our hypothesis.

Effects of ischemic liver preconditioning on hepatic ischemia/reperfusion injury in the rat

To minimize bleeding during major liver resections or liver transplantation, surgical measures have been adopted that induce ischemia-reperfusion injury (I/R) which may significantly contribute to morbidity and mortality of partial liver resections. Several methods have sought to minimize I/R hepatic lesions. The present project assessed the protective role of ischemic preconditioning (IPC) in rat livers. The IPC was accomplished by clamping the hepatic pedicle for 5 minutes, followed by a 5-minute reperfusion (R) period before a 2-hour ischemia. Thereafter, reperfusions of 1, 3, and 24 hours were compared among IPC and control groups without IPC. Liver biopsy and blood samples were measured for mitochondrial respiratory control ratio (RCR), serum aspartate aminotransferase (AST), and alanine aminotransferase (ALT). IPC protected liver mitochondrial function. Serum aminotransferase levels were significantly lower among animals undergoing IPC compared with groups without IPC. Thus, we verified the effects of IPC for hepatocellular protection against I/R lesions.

Ischemic preconditioning versus intermittent vascular occlusion in liver resections performed under selective vascular exclusion: a prospective randomized study

BACKGROUND

The aim of this study was to compare ischemic preconditioning with the intermittent vascular occlusion technique in liver resections performed under inflow and outflow occlusion.

METHODS

Fifty-four patients with resectable liver tumors assigned were randomly to undergo surgery with either ischemic preconditioning (IP group, n = 27) or with intermittent vascular occlusion (IVO group, n = 27). Both groups were compared regarding surgical parameters, aspartate transaminase levels, and apoptosis.

RESULTS

For warm ischemic time less than 40 minutes, no significant difference was noticed between the 2 groups apart from caspase-3 activity, which was higher in the IVO group than in the IP group (17.2 +/- 3.4 vs. 10.3 +/- 5.2, P < .05). When warm ischemia exceeded 40 minutes, the IP group showed higher levels in blood aspartate transaminase levels on day 3 (442 +/- 178 IU/L vs. 305 +/- 104 IU/L, P < .05) and higher caspase-3 levels (26.5 +/- 5.7 count/high-power field [hpf] vs. 20.7 +/- 3.6 count/hpf, P < .05) and apoptotic activity (28.5 +/- 7.5 count/hpf vs. 20.2 +/- 4.1 count/hpf, P < .05), as compared with the IVO group.

CONCLUSIONS

Although both techniques showed comparable efficacy for short ischemic times, intermittent vascular occlusion provided better cytoprotection when ischemia exceeded 40 minutes.

Use of tissue ultrafiltration for treatment of compartment syndrome: a pilot study using porcine hindlimbs

OBJECTIVES

To demonstrate the efficacy of compartment syndrome ultrafiltration for the treatment of acute compartment syndrome in an animal model. Our hypothesis is the removal of interstitial fluid will result in a reduction of intramuscular pressure compared with untreated controls in a model of bilateral induced compartment syndrome.

DESIGN

Controlled experimental model.

SETTING

Animal research facility.

PATIENTS/PARTICIPANTS

Three pairs of porcine hindlimbs.

INTERVENTION

Acute compartment syndrome was created in the pig hindlimb by infusion of saline to maintain the intramuscular pressure 30 mm Hg greater than the animal's mean arterial pressure for 8 hours. After a 2-hour reperfusion interval, ultrafiltration (removal of fluid through 1 mm diameter porous catheters, connected to -500 mm Hg suction) was commenced in 1 limb only and continued for 9.5 hours.

MAIN OUTCOME MEASURES

Intramuscular pressure, ultrafiltrate volume, ultrafiltrate and serum levels of creatine kinase and lactate dehydrogenase, histologic measurement of extracellular and intracellular edema, as well as the degree of cellular necrosis.

RESULTS

Intramuscular pressure tended to be lower on the treated side at the end of the treatment period [treated leg: 9.3 +/- 4.0 mm Hg (+/- SE), control leg: 19.3 +/- 1.4 mm Hg, P = 0.03]. Analysis of ultrafiltrate fluid showed that levels of creatine kinase and lactate dehydrogenase were elevated compared with serum levels. Creatine kinase levels in serum were measured at 4150 +/- 780 U/L, whereas ultrafiltrate levels of creatine kinase were 28,700 +/- 17,700 U/L (+/- SE) (P = 0.1). Lactate dehydrogenase was measured at 1950 +/- 180 U/L in serum, but markedly elevated in ultrafiltrate [160,000 +/- 88,900 U/L (+/- SE), P = 0.05]. Quantification of cellular and interstitial dimensions showed no difference in control and experimental limbs. Quantification of the degree of muscle necrosis revealed 6.1 +/- 2.7% necrosis in the treated limb compared to 11.3 +/- 1.6% necrosis in the control group (P = 0.02, df = 2, 1-tailed paired t test).

CONCLUSION

This pilot study demonstrates the feasibility of tissue ultrafiltration for reduction of intramuscular pressure in this porcine model. Further studies are underway. Compartment syndrome ultrafiltration may be useful prophylactically in patients at risk for acute compartment syndrome. Sampling of interstitial fluid and frequent measurement of intramuscular pressure may allow earlier diagnosis and treatment of acute compartment syndrome, whereas the reduction of tissue pressure by compartment syndrome ultrafiltration may prevent acute compartment syndrome from occurring. Additionally, compartment syndrome ultrafiltration will not hinder the ability of clinicians to use the clinical examination and pressure monitoring as the gold standard.

Hypoxia-reoxygenation-induced chemokine transcription is not prevented by preconditioning or intermittent hypoxia, in mice hepatocytes

Prolonged ischemia used in liver surgery and/or transplantation causes cellular damage resulting in apoptosis and necrosis. Ischemia-reperfusion (I/R) led Kupffer cells to pro-inflammatory cytokines secretion [tumor necrosis factor (TNF)-alpha, interleukin-1] which involve chemokines secretion by hepatocytes. These chemokines have neutrophil chemotactic properties and neutrophils are involved in the development of I/R-induced necrosis. The aim of this study was to specify the consequence of partial oxygen pressure variation on hepatocyte chemokines synthesis and to verify if intermittent hypoxia and/or preconditioning could decrease it. It was performed on primary cultured mice hepatocytes and Kupffer cells, subjected to continuous, intermittent hypoxia or preconditioning phases, mimicking surgical processes. The chemokine secretion was evaluated by RNase protection assay and enzyme-linked immunosorbent assay method. Only monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-2 (MIP-2) mRNA formation were observed, especially after 1-h hypoxia followed by 10-h (for MCP-1) or 24-h reoxygenation (for MIP-2). In conclusion, TNF-alpha and coculture with Kupffer cells increased hepatocyte chemokines mRNA transcription, whereas surgical split up protocols (intermittent hypoxia and preconditioning) had no significant effect.

Tumor necrosis factor suppression and microcirculatory disturbance amelioration in ischemia/reperfusion injury of rat liver after ischemic preconditioning

BACKGROUND

Brief periods of hepatic ischemia produce immediate tolerance for subsequent prolonged ischemia. Although the beneficial effect of this ischemic preconditioning is recognized, the mechanism itself remains poorly understood.

METHODS

Male Wistar rats were divided into two groups: a control group that was subjected to 30 min of ischemia + following reperfusion, and an ischemic preconditioning group that was subjected to 5 min of ischemia + 5 min of reperfusion + 30 min of ischemia + following reperfusion. By using this model, hepatic damage, microcirculatory disturbances, and tumor necrosis factor-alpha protein production and mRNA expression were analyzed during the course of reperfusion in both groups. For the hepatic damage evaluations, hepatic enzyme levels, histology, apoptosis analysis, and intravital microfluorography for dead cells were examined. For the microcirculatory disturbance analysis, an adhesion molecule and intravital microfluorography for endothelial-adherent leukocytes were examined.

RESULTS

In the ischemic preconditioning group, ischemia/reperfusion injuries (shown by hepatic enzymes elevation, histological degeneration, and increases in the number of apoptotic cells and microfluorographic dead cells) were markedly reduced. Moreover, microcirculatory disturbances represented by intercellular adhesion molecule-1 expression and leukocyte adhesion on the endothelium were ameliorated. Tumor necrosis factor-alpha protein production and mRNA expression were also suppressed in the ischemic preconditioning group.

CONCLUSION

The suppression of tumor necrosis factor-alpha and the subsequent amelioration of microcirculatory disturbances were observed, suggesting that the mechanism underlying the protective effect of ischemic preconditioning in hepatic ischemia/reperfusion injuries may involve tumor necrosis factor-alpha and microcirculatory regulation.

Lipopolysaccharide preconditioning and cross-tolerance: the induction of protective mechanisms for rat intestinal ileus

BACKGROUND & AIMS

Endotoxin elicits an inflammatory response within the intestinal muscularis and causes intestinal muscle dysfunction. Our aims were to investigate intestinal muscle recovery after a single or repeated lipopolysaccharide (LPS) injections. We also investigated the ability of LPS to induce cross-tolerance to postoperative ileus.

METHODS

Motility was measured in vivo and in vitro by transit and organ-bath techniques. Nuclear factor kappa-B, nuclear factor interleukin 6, and signal transducer and activator of transcription were quantified by using electrophoretic mobility shift assay, and tumor necrosis factor alpha, interleukin 6, inducible nitric oxide synthase, and cyclooxygenase 2 were measured with reverse-transcription polymerase chain reaction. Myeloperoxidase histochemistry for neutrophils was performed in jejunal muscularis whole mounts.

RESULTS

Endotoxin-induced suppression of in vitro muscle contractility temporally recovered over 7 days with a similar profile whether after a single dose or during the continuous daily injection of LPS. Functional adaptation to continuous LPS was reflected in a significant blunting of transcription factor activation and cytokine messenger RNA up-regulation compared with the naive LPS-stimulated muscularis. Preconditioning of the muscularis showed significant cross-tolerance to the functional, molecular, and leukocytic sequelae of intestinal manipulation.

CONCLUSIONS

The muscularis externa recovered and developed tolerance to endotoxin over 7 days, which conferred cross-tolerance to intestinal manipulation. Thus, preconditioning induces protective mechanisms to a subsequent insult within the muscularis externa.

Comparison of ischemic preconditioning and intermittent and continuous inflow occlusion in the murine liver

OBJECTIVE

To compare protection of the liver by ischemic preconditioning and intermittent inflow occlusion in a mouse model of prolonged periods of ischemia.

SUMMARY BACKGROUND DATA

Preconditioning (short ischemic stress prior to a prolonged period of ischemia) and intermittent inflow occlusion protect the liver against reperfusion injury. This is the first study comparing these two modalities with continuous inflow occlusion (control).

METHODS

Mice were subjected to 75 or 120 minutes of 70% hepatic ischemia and 3 hours of reperfusion. Each ischemic period was evaluated using three different protocols: continuous ischemia (control), preconditioning (10 minutes ischemia and 15 minutes reperfusion) prior to the prolonged ischemic insult, and intermittent clamping (cycles of 15 minutes ischemia and 5 minutes reperfusion). Organ injury was evaluated using serum levels of aspartate aminotransferase (AST), hematoxylin and eosin staining, and specific markers of apoptosis (cytochrome C release, caspase 3 activity, and TUNEL staining). Animal survival was determined using a model of total hepatic ischemia.

RESULTS

Intermittent inflow occlusion and ischemic preconditioning were both protective against ischemic insults of 75 and 120 minutes compared with controls (continuous ischemia only). Protection against 75 minutes of ischemia was comparable in the intermittent clamping and the ischemic preconditioning group, whereas intermittent clamping was superior at 120 minutes of ischemia. One hundred percent animal survival was observed after 75 minutes of total hepatic ischemia using both protective protocols, whereas all animals subjected to continuous ischemia died after surgery. After 120 minutes of ischemia, intermittent inflow occlusion was associated with better animal survival (71%) compared with preconditioning (14%).

CONCLUSIONS

Preconditioning and intermittent clamping are both protective against prolonged periods of ischemia. In the clinical setting, preconditioning is superior for ischemic periods of up to 75 minutes because it is not associated with blood loss during transection of the liver. However, for prolonged ischemic insults exceeding 75 minutes, intermittent clamping is superior to preconditioning.

Aspectos básicos da lesão de isquemia e reperfusão e do pré-condicionamento isquêmico

A isquemia tem papel fundamental em muitas situações clínicas perioperatórias . Apesar da revascularização sanguínea a um órgão isquêmico seja essencial para prevenir a irreversibilidade da lesão celular, a reperfusão pode agravar as lesões produzidas na fase isquêmica isolada. Assim, o dano celular induzido após reperfusão de um órgão isquêmico é denominado de lesão de isquemia-reperfusão (I/R). Aspectos básicos da lesão I/R, são revisados neste artigo.