The effects of propofol or halothane on free radical production after tourniquet induced ischaemia-reperfusion injury during knee arthroplasty

A reproducible method for biochemical, histological and functional assessment of the effects of ischaemia-reperfusion syndrome in the lower limbs

Current methodology described to mimic lower limb ischaemia-reperfusion injury (LL-IRI) does not accurately define the procedures and pressures exerted to induce and maintain ischaemia. In this piece of work, we propose a well-defined and detailed rat model that simulates the conditions established in clinical practice guidelines for tourniquet application and allows us to test treatments that aim to prevent/reduce LL-IRI. Eighty-six male WAG/RijHsd rats were subjected to hind limb IRI (LL-IRI), using a mechanical system applying a 1 kg tension to induce and maintain ischemia for 2 or 3 h, and assessed the damage caused by reperfusion at biochemical and muscular levels at different time points. At the biochemical level, both 2 and 3 h of ischemia induced changes (except for electrolyte levels); 3 h of ischemia induced greater changes in specific markers of muscular damage: creatine kinase (CK) and lactate dehydrogenase (LDH). At the histopathological level, 3 h of ischemia and 24 h of reperfusion was associated with an increase in hind limb girth, cross-sectional area, and weight and presence of neutrophils, as well as histological damage in more than 60% of muscle fibres. Our model allows to reliably reproduce the damage associated with the use of a pneumatic tourniquet. CK and LDH, as well as measures of tissue damage, allow to define and characterize the response to LL-IRI-related damage. A period of 3 h of ischemia followed by 3 h of reperfusion caused only local damage but showed greater sensitivity to detect differences in future studies on prophylactic treatments against LL-IRI.

One-lung ventilation duration-dependent stress response in thoracotomies and the effect of a low-volume, high-frequency differentiated ventilation strategy on this response

Background

This study aims to investigate the effect of ventilation of the non-ventilated lung in patients undergoing one-lung ventilation by a separate low-tidal-volume (1 mL/kg) ventilator at high frequency (30/min) on preventing the effect of one-lung ventilation-associated oxidative damage.

Methods

The study included 45 patients (24 males, 21 females; mean age 54.6±7.7 years; range, 18 to 65 years) with an American Society of Anesthesiologists risk group of 1 to 2 and scheduled for elective thoracotomy. Patients were randomly divided into three groups as those due for thoracotomy without one-lung ventilation (group 1, n=15), those due for thoracotomy with one-lung ventilation (group 2, n=15), and those due for thoracotomy in whom both lungs were ventilated (group 3, n=15). Blood specimens were collected for ischemia-modified albumin, malondialdehyde, and lactate measurements one minute before one-lung ventilation (t0), 30 minutes after one-lung ventilation (t1), 60 minutes after one-lung ventilation (t2), and at postoperative 24th hour (t3). For group 1, t0 was defined as the time at which the thorax was opened.

Results

A statistically significant increase in ischemia-modified albumin, malondialdehyde, and lactate levels occurred in group 2 as the duration of one-lung ventilation increased (p<0.01). Plasma ischemia-modified albumin and malondialdehyde levels in group 3 were statistically significantly lower at t1, t2, and t3 compared with group 2 (p<0.01). Plasma lactate levels were significantly lower in group 3 at t1 (p<0.05) and t3 compared with group 2 (p<0.01).

Conclusion

Separate ventilation of the non-ventilated lung with low tidal volume and high frequency reduces the response to one-lung ventilation-associated oxidative stress in thoracic surgery.

The Possible Pathophysiological Outcomes and Mechanisms of Tourniquet-Induced Ischemia-Reperfusion Injury during Total Knee Arthroplasty

Ischemia and reperfusion (I/R) injury induced by tourniquet (TQ) application leads to the release of both oxygen free radicals and inflammatory cytokines. The skeletal muscle I/R may contribute to local skeletal muscle and remote organ damage affecting outcomes after total knee arthroplasty (TKA). The aim of the study is to summarize the current findings associated with I/R injury following TKA using a thigh TQ, which include cellular alterations and protective therapeutic interventions. The PubMed database was searched using the keywords "ischemia reperfusion injury," "oxidative stress," "tourniquet," and "knee arthroplasty." The search was limited to research articles published in the English language. Twenty-eight clinical studies were included in this qualitative review. Skeletal muscle I/R reduces protein synthesis, increases protein degradation, and upregulates genes in cell stress pathways. The I/R of the lower extremity elevates local and systemic oxidative stress as well as inflammatory reactions and impairs renal function. Propofol reduces oxidative injury in this I/R model. Ischemic preconditioning (IPC) and vitamin C may prevent oxygen free radical production. However, a high dose of N-acetylcysteine possibly induces kidney injury. In summary, TQ-related I/R during TKA leads to muscle protein metabolism alteration, endothelial dysfunction, oxidative stress, inflammatory response, and renal function disturbance. Propofol, IPC, and vitamin C show protective effects on oxidative and inflammatory markers. However, a relationship between biochemical parameters and postoperative clinical outcomes has not been validated.

Effect of Propofol, Sevoflurane and Desflurane on Systemic Redox Balance

We studied the effects of Propofol, Desflurane, and Sevoflurane on the systemic redox balance in patients undergoing laparohysterectomy. We measured blood concentration of glutathione (GSH), plasma antioxidant capacity (Trolox Equivalent Antioxidant Capacity-TEAC), and lipid peroxidation products (malondialdehyde (aMDA) and 4-hydroxynonenal (aHNE) protein adducts). Sixty patients were randomly placed into three groups of twenty people each. In Group P anesthesia was induced with Propofol 2 mg/kg and maintained with 12–10–8 mg/kg/min; in Groups S and D anesthesia was induced with 3 mg/kg Sodium Thiopental and maintained with 2% Sevoflurane and 6% Desflurane, respectively. Blood samples were collected prior to induction (T0bas), 60min and 24h postoperatively (T160' and T224 h). In Group P, GSH increased on T160' (p<0.02) and returned to baseline on T24h, while TEAC remained unmodified; in Groups S, GSH and TEAC decreased on T160' (p<0.01 vs. T0bas, p<0.03 vs. T0bas, respectively); in Group D, on T160' there was a slight decrease of GSH and TEAC. The levels of aMDA slightly decreased throughout the study periods in Group P, increased in Group D, and remained stable in Group S. Propofol showed antioxidant properties, while Sevoflurane and Desflurane seemed to shift the redox balance towards oxidation, yet without inducing overt oxidative damage.

Influence of total intravenous anesthesia, entropy and laparoscopy on oxidative stress

BACKGROUND AND OBJECTIVES

Recent studies have correlated postoperative mortality with anesthetic mortality, especially with the depth of anesthesia and systolic blood pressure (SBP). The aim of this study is to evaluate the effects of the depth of total intravenous anesthesia (TIVA) using remifentanil and propofol, performed with monitoring of response entropy (RE) on blood concentrations of oxidative stress markers (TBARS and glutathione) during laparoscopic operations.

METHOD

Twenty adult patients, ASA I, BMI 20-26 kg.m(-2), aged 20 to 40 years, were randomly distributed into two groups: Group I underwent anesthetic-surgical procedure with RE maintained between 45 and 59, and Group II underwent anesthetic-surgical procedure with RE between 30 and 44. In both groups, the remifentanil and propofol infusion was controlled by the effector site (Es), adjusted to maintain RE desired values (Groups I and II) and always assessing the suppression rate (SR). Patients were evaluated in six periods: M1 (immediately before anesthesia), M2 (before tracheal intubation [TI]), M3 (5-minutes after TI), M4 (immediately before pneumoperitoneum [PPT]), M5 (1-minute after PPT), and M6 (1-hour after the operation). The following parameters were assessed at all times: SBP, DBP, HR, RE, SR, TBARS, and glutathione.

RESULTS

We found increases in TBARS and glutathione in M5, both in Group I and Group II (p<0.05), with higher values in Group II, and SR in three patients in Group II, immediately after PPT.

CONCLUSIONS

Increased markers in Group I (M5) suggests an increase in anaerobic metabolism (AM) in the splanchnic circulation while the highest values seen in Group II (GII > GI in M5, p<0.05%) suggest interference of another factor (deep anesthesia) responsible for the increase in AM, probably as a result of increased autonomic nervous system depression and minor splanchnic self-regulation.

[Effects of various anesthesia maintenance on serum levels of selenium, copper, zinc, iron and antioxidant capacity]

BACKGROUND AND OBJECTIVES

In this study, we aimed to investigate the effects of sevoflurane, desflurane and propofol maintenances on serum levels of selenium, copper, zinc, iron, malondialdehyde, and glutathion peroxidase measurements, and antioxidant capacity.

METHODS

60 patients scheduled for unilateral lower extremity surgery which would be performed with tourniquet under general anesthesia were divided into three groups. Blood samples were collected to determine the baseline serum levels of selenium, copper, zinc, iron, malondialdehyde and glutathion peroxidase. Anesthesia was induced using 2-2.5mgkg(-1) propofol, 1mgkg(-1) lidocaine and 0.6mgkg(-1) rocuronium. In the maintenance of anesthesia, under carrier gas of 50:50% O2:N2O 4Lmin(-1), 1 MAC sevoflorane was administered to Group S and 1 MAC desflurane to Group D; and under carrier gas of 50:50% O2:air 4Lmin(-1) 6mgkgh(-1) propofol and 1μgkgh(-1) fentanyl infusion were administered to Group P. At postoperative blood specimens were collected again.

RESULTS

It was observed that only in Group S and P, levels of MDA decreased at postoperative 48th hour; levels of glutathion peroxidase increased in comparison to the baseline values. Selenium levels decreased in Group S and Group P, zinc levels decreased in Group P, and iron levels decreased in all three groups, and copper levels did not change in any groups in the postoperative period.

CONCLUSION

According to the markers of malondialdehyde and glutathion peroxidase, it was concluded that maintenance of general anesthesia using propofol and sevoflurane activated the antioxidant system against oxidative stress and using desflurane had no effects on oxidative stress and antioxidant system.

Lower limb ischaemia and reperfusion injury in healthy volunteers measured by oxidative and inflammatory biomarkers

Objective:

Ischaemia-reperfusion (IR) injury is partly caused by the release of reactive oxygen species and cytokines and may result in remote organ injury. Surgical patients are exposed to surgical stress and anaesthesia, both of which can influence the IR response. An IR model without these interfering factors of surgery is, therefore, useful to test the potential of antioxidant and cytokine-modulatory treatments. The aim of this study was to characterize a human ischaemia-reperfusion model with respect to oxidative and inflammatory biomarkers.

Materials and methods:

Ten male volunteers were exposed to 20 minutes of lower limb ischaemia. Muscle biopsies and blood samples were taken at baseline and 5, 15, 30, 60 and 90 minutes after tourniquet release and analysed for malondialdehyde (MDA), ascorbic acid, dehydroascorbic acid, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-1 receptor antagonist (IL-1Ra), IL-6, IL-10, TNF-receptor (TNF-R)I, TNF-RII and YKL-40.

Results:

We found no significant increase in MDA in the muscle biopsies after reperfusion. Plasma levels of oxidative and pro- and anti-inflammatory parameters showed no significant differences between baseline and after reperfusion at any sampling time.

Conclusion:

Twenty minutes of lower limb ischaemia does not result in an ischaemia-reperfusion injury in healthy volunteers, measurable by oxidative and pro- and anti-inflammatory biomarkers in muscle biopsies and in the systemic circulation.

Ischemia-reperfusion injury and volatile anesthetics

Ischemia-reperfusion injury (IRI) is induced as a result of reentry of the blood and oxygen to ischemic tissue. Antioxidant and some other drugs have protective effect on IRI. In many surgeries and clinical conditions IRI is counteract inevitable. Some anesthetic agents may have a protective role in this procedure. It is known that inhalational anesthetics possess protective effects against IRI. In this review the mechanism of preventive effects of volatile anesthetics and different ischemia-reperfusion models are discussed.

Therapeutic effects of thymoquinone in a model of neuropathic pain

Background

The goal of our study was to determine the therapeutic effects of thymoquinone in a dose-dependent manner in a model of neuropathic pain following an experimentally applied spinal cord injury (SCI).

Methods

Fifty female adult Wistar albino rats weighing between 220 and 260 g were included in the study and were divided into 5 groups as follows: Group S (sham), Group C (control), Group T100 (100 mg/kg thymoquinone), Group T200 (200 mg/kg thymoquinone), and Group T400 (400 mg/kg thymoquinone). To begin the experiment, SCI was applied to all groups (with the exception of the sham group) following a mechanical and heat–cold test. Two weeks later, the mechanical and heat–cold tests were repeated, and a single normal saline dose was given to the sham and control groups, whereas 3 varying doses of thymoquinone were given to the other groups. The mechanical and heat–cold tests were repeated at 30, 60, 120, and 180 minutes after receiving thymoquinone. Finally, the animals were put to death via the removal of intracardiac blood. The levels of nitric oxide, total oxidant status, total antioxidant status, paraoxonase, malondialdehyde, tumor necrosis factor-α, and interleukin-1β were determined in all of the blood samples.

Results

The withdrawal threshold and withdrawal latency values recorded from the mechanical and heat–cold allodynia measurements for all 3 thymoquinone groups were higher than that of the control group at all time points (ie, 30, 60, 120, and 180 minutes). There were no differences in these results between the 3 thymoquinone groups. The paraoxonase and total antioxidant status serum levels of all 3 thymoquinone groups were higher than those of the control group, whereas total oxidant status, nitric oxide, malondialdehyde, interleuken-1β, and tumor necrosis factor-α levels were lower in the 3 thymoquinone groups than in the control group.

Conclusions

Thymoquinone is beneficial for decreasing experimental neuropathic pain following SCI. However, increasing the dose does not change the effect.

The effects of spinal, inhalation, and total intravenous anesthetic techniques on ischemia-reperfusion injury in arthroscopic knee surgery

PURPOSE

To compare the effects of different anesthesia techniques on tourniquet-related ischemia-reperfusion by measuring the levels of malondialdehyde (MDA), ischemia-modified albumin (IMA) and neuromuscular side effects.

METHODS

Sixty ASAI-II patients undergoing arthroscopic knee surgery were randomised to three groups. In Group S, intrathecal anesthesia was administered using levobupivacaine. Anesthesia was induced and maintained with sevoflurane in Group I and TIVA with propofol in Group T. Blood samples were obtained before the induction of anesthesia (t1), 30 min after tourniquet inflation (t2), immediately before (t3), and 5 min (t4), 15 min (t5), 30 min (t 6), 1 h (t7), 2 h (t8), and 6 h (t9) after tourniquet release.

RESULTS

MDA and IMA levels increased significantly compared with baseline values in Group S at t2-t 9 and t2-t7. MDA levels in Group T and Group I were significantly lower than those in Group S at t2-t8 and t2-t9. IMA levels in Group T were significantly lower than those in Group S at t2-t7. Postoperatively, a temporary 1/5 loss of strength in dorsiflexion of the ankle was observed in 3 patients in Group S and 1 in Group I.

CONCLUSIONS

TIVA with propofol can make a positive contribution in tourniquet-related ischemia-reperfusion.

Propofol Protects against Ischemia/Reperfusion Injury Associated with Reduced Apoptosis in Rat Liver

Propofol is an intravenous anesthetic, reported to have a protective effect against ischemia/reperfusion (I/R) injury in heart and brain, but no definite data are available concerning its effect in hepatic I/R. This work investigated the effect of propofol anesthesia on hepatic I/R injury using in vivo rat model. Four groups of rats were included: sham operated, I/R (30 min ischemia and 2 h reperfusion), I/R treated with propofol (10 mg/kg/h), and I/R treated with propofol (20 mg/kg/h). Liver enzyme leakage, TNF-α and caspase-3 levels, and antiapoptotic Bcl-xL/apoptotic Bax gene expression, together with histopathological changes, were used to evaluate the extent of hepatic I/R injury. Compared with sham-operated group, I/R group showed significant increase in serum levels of liver enzymes (ALT, AST), TNF-α, and caspase-3 and significant decrease in the Bcl-xL/Bax ratio, associated with histopathologic damage in liver. Propofol infusion significantly attenuated these changes with reduced hepatic histopathologic lesions compared with nonpreconditioned I/R group. However, no significant differences were found between two groups treated with different doses of propofol. In conclusion, propofol infusion reduced hepatic I/R injury with decreased markers of cellular apoptosis. Therefore, propofol anesthesia may provide a useful hepatic protection during liver surgery.

The comparison of neuroprotective effects of intrathecal dexmedetomidine and metilprednisolone in spinal cord injury

BACKGROUND

The purpose of this study is the investigation of the effects of intrathecally injected dexmedetomidine and methylprednisolone and their dominancy over one another in rats with generated Spinal Cord Injury (SCI).

METHODS

40, female, adult Wistar Albino rats weighing 220-260 g were included in the study. The rats were fixed with Intrathecal catheter (IT) and divided into four groups. All subjects were applied T7-10 laminectomy after catheter. Group S (n:10) was injected with IT 10 μL isotonic saline; Group C (n:10) with IT 10 μL isotonic saline after SCI; Group D (n:10) with IT one doze 10 μL of dexmedetomidine after SCI; Group M (n:10) IT one dose 10 μL of methylprednisolone. The subjects were sacrificed 72 h after this operation. The damaged area was removed biochemically and histopathologically examined.

RESULTS

Antioxidant and inflammatory parameters searched for in all damages tissue were statistically different in all groups from group S. They were different in group M and group D than group C (p < 0.001). After the comparison of group D and group M, PON and IL6 values were higher in group D (p = 0.003, p = 0.035) while the other two biochemical parameters were similar in both groups (Table 1). After histopathologic trials, edemas, bleeding and necrosis were found less in group S while at the most in group C (p < 0.001). In group M and group D, however, they were higher than group S and lower than group C (p < 0.001). After the comparison of group D and group M, while there was no difference in terms of edema necrosis, the amount of bleeding was lower in group D (p < 0.001) (Table 2).

CONCLUSIONS

It has been discovered that intrathecal use of dexmedetomidine caused neuroprotective effects similar to methylprednisolone.

Dexmedetomidine did not reduce the effects of tourniquet-induced ischemia-reperfusion injury during general anesthesia

Ischemia reperfusion injury causes the release of free oxygen radicals. Free oxygen radicals initiate the production of toxic metabolites, such as malondialdehyde (MDA), through the lipid peroxidation of cellular membranes. Following lipid peroxidation, the antioxidant enzyme system is activated against reactive oxygen species (ROS) and attempts to protect cells from oxidative damage. There is a balance between the scavenging capacity of antioxidant enzymes and ROS. Because of this balance, the total antioxidant capacity (TAC) measurement is a sensitive indicator of the overall protective effects of the antioxidants. Alpha(2) receptor agonists are effective in preventing hemodynamic reactions during extremity surgeries by preventing the release of catecholamines secondary to tourniquet application. They have also been shown to possess preventive effects in various ischemia-reperfusion injury models. In our study, we examined the effects of dexmedetomidine on tourniquet-induced ischemia-reperfusion injury in lower extremity surgeries performed under general anesthesia. The effects of dexmedetomidine were measured with serum MDA and TAC levels. We studied 60 adult American Society of Anesthesiologists (ASA) physical status I or II patients undergoing one-sided lower extremity surgery with tourniquet. The patients were randomly divided into two groups. Group D was administered a dexmedetomidine infusion at a rate of 0.1μg/kg/minute(-1) for 10 minutes prior to induction and then at 0.7μg/kg/hour(-1) until 10 minutes before the end of the operation. The control group (Group C) received a saline infusion of the same amount and for the same period of time. General anesthesia was induced with thiopental, fentanyl, and rocuronium and maintained with nitrous oxide and sevoflurane in both groups. Venous blood samples were obtained before the administration of the study drugs (basal) at 1 minute before tourniquet release and at 5 and 20 minutes after tourniquet release (ATR). In both groups, MDA levels decreased at 5 and 20 minutes ATR when compared with the basal values (p<0.05). TAC levels decreased at 1 and 5 minutes ATR and then returned to basal values at 20 minutes ATR (p<0.05). In reference to the prevention of lipid peroxidation in tourniquet-induced ischemia-reperfusion injury, the results from the two groups in our study showed that dexmedetomidine did not have an additional protective role during routine general anesthesia.

Different oxidative stress marker levels in blood from the operated knee or the antecubital vein in patients undergoing knee surgery: a tourniquet-induced ischemia-reperfusion model

BACKGROUND

In knee surgery a tourniquet is usually applied in order to provide a bloodless surgical field. This study aims to compare, in a tourniquet-induced ischemia-reperfusion model, the glutathione oxidation and lipid peroxidation in two different blood sources: an operated knee drainage tube or the antecubital vein.

METHODS

Thirty-two patients undergoing total knee replacement were studied. We measured reduced glutathione (GSH), oxidized glutathione (GSSG), malondialdehyde (MDA) and other metabolic parameters in the blood from the operated knee (17 patients), or from the antecubital vein (15 patients) before tourniquet inflation (T(0)) and after tourniquet release at different times: 3, 10, and 60 minutes (T(1), T(2), and T(3), respectively).

RESULTS

We have found an early increase of approximately 100% in GSSG and MDA blood levels coinciding with a decrease in GSH levels at T(1)-T(3) in blood from the operated knee. These changes were also observed in blood from the antecubital vein at T(1) and T(2), but at lower levels than in blood from the operated knee.

CONCLUSIONS

There is an intense glutathione oxidation and lipid peroxidation in the operated knee after tourniquet deflation. The surgical drainage is a good source of blood for the determination of biomarkers in a tourniquet-induced ischemia-reperfusion model, because changes are observed more early and it is more direct than another source of systemic blood.

XPD and hOGG1 gene polymorphisms in reperfusion oxidative stress

Knee replacement surgery is an ischemia/reperfusion model, as it uses tourniquet applied to the knee area to stop the blood flow during the operation. Fifty patients that were undergoing elective arthroscopic knee surgery were included in our study. Human 8-oxoguanine glycosylase 1 (hOGG1) is an enzyme to repair specific DNA lesions and a good marker of hydroxyl radical damage to DNA. XPD is another DNA repair gene. We investigated the effect of hOGG1 (Ser326Cys) and XPD (Lys751Gln) polymorphisms on the oxidative stress level after reperfusion. To evaluate oxidative stress conditions, we measured 8-hydroxyguanosine and malondialdehyde (MDA) levels. Polymorphism analyses were done by PCR-RFLP; serum 8-hydroxyguanosine and MDA levels were determined by enzyme-linked immunoassay. There were no significant differences between serum MDA and 8-hydroxyguanosine levels in the samples taken before and after tourniquet application; none of these parameters were related with hOGG1 genotypes. However, we observed increased MDA levels after tourniquet application in M allele carriers for the XPD gene; this could mean that M allele carriers are more prone to DNA damage due to oxidative activity.

Antioxidant effects of propofol on tourniquet-induced ischemia-reperfusion injury: an experimental study

PURPOSE

This experimental study aimed to investigate the antioxidant effects of propofol anesthesia at induction doses in a rat skeletal muscle ischemia/reperfusion injury model.

METHODS

Twenty-six rats were randomly divided into three groups to receive one of the following interventions: sham operation (n = 6), ischemia/reperfusion (I/R) injury (n = 10), or propofol administration in addition to I/R injury (n = 10). I/R injury was attained by 2-h clamping of femoral artery followed by 3-h perfusion. Then blood and tissue samples were collected for biochemical analysis and histopathologic examination. Glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) enzyme activities and nitric oxide (NO) and malondialdehyde (MDA) levels were measured in both plasma and muscle tissue. In addition, catalase (CAT) activity and protein carbonyl (PC) content were measured in muscle tissue.

RESULTS

I/R group had significantly higher SOD activity (9.05 versus 5.63 and 6.18 U/mL, P < 0.05) and NO level (46.77 versus 30.62 and 33.90 μmol/L, P < 0.05) compared with sham-operated group and I/R plus propofol group. In addition, GSH-Px activity of the I/R group was significantly higher than sham-operated group (1.26 versus 1.05 U/mL, P < 0.05). I/R group had significantly higher tissue activities of CAT (0.11 versus 0.06 and 0.04 k/g protein, P < 0.05) and SOD (0.12 versus 0.08 and 0.07 U/mg protein, P < 0.05) compared with the sham and I/R plus propofol group. Histopathologic examination showed that I/R plus propofol group had significantly lower degeneration (P = 0.021) and inflammation (P = 0.028) scores compared with I/R group.

CONCLUSION

Propofol anesthesia seems to enhance the antioxidant capacity against tourniquet induced ischemia-reperfusion injury.

Hemoglobin attenuates the effects of inspired oxygen on plasma isofurans in humans during upper-limb surgery

Reperfusion injury is characterized by significant oxidative stress. F(2)-isoprostanes (F(2)-IsoP's) and isofurans (IsoF's), the latter preferentially produced during increased oxygen tension, are recognized markers of in vivo oxidative stress. We aimed to determine whether increasing oxygen tension during reperfusion modified levels of plasma total IsoF's and F(2)-IsoP's. Forty-five patients undergoing upper-limb surgery were randomized to receive inspired oxygen concentrations of 30, 50, or 80% during the last 15 min of surgery. Venous blood samples were taken before the change in inspired oxygen, after 10 min (before reperfusion), and after 15 min (5 min after reperfusion). IsoF's and F(2)-IsoP's were measured by gas chromatography-mass spectrometry. Venous oxygen tension and hemoglobin concentrations were also measured. Plasma IsoF and F(2)-IsoP levels in the 50 and 80% O(2) groups were not significantly different from those of the 30% O(2) group. In secondary analyses, using data combining all groups, levels of IsoF's, but not F(2)-IsoP's, associated with higher venous oxygen tension (P=0.038). Hemoglobin negatively modified the influence of oxygen tension on levels of IsoF's (P=0.014). This study has shown, for the first time, that plasma IsoF levels associate with higher oxygen tension in a human model of reperfusion, and this effect is significantly attenuated by hemoglobin.

Effect of an anesthesia with propofol compared with desflurane on free radical production and liver function after partial hepatectomy

Propofol has shown antioxidant properties, but no study has focused on liver resection surgery. The aim of this study was to investigate the effect of an anesthesia with propofol compared with desflurane on oxidative stress and hepatic function during and after partial hepatectomy. This was a prospective randomized study performed on two parallel groups. The primary endpoint was malondialdehyde (MDA) plasma concentration 30 min after hepatic vascular unclamping. Hepatic damages were evaluated by plasma levels of alpha-glutathione S-transferase (α-GST) 120 min after hepatic vascular unclamping and of aminotransferases at 120 min and on days 1, 2, 5, and 10. Liver function recovery was assessed by monoethylglycinexylidide (MEGX) formation 15 min after lidocaine injection on day 2 and by prothrombin time and plasma factor V at 120 min and on days 1, 2, 5, and 10. Thirty patients were analyzed (propofol group: 17; desflurane group: 13). There was no significant difference between groups for MDA plasma concentration 30 min after hepatic vascular unclamping (mean ± standard-deviation: 1.28 ± 0.40 and 1.21 ± 0.29 in propofol and desflurane groups, respectively, P = 0.608). Plasma levels of α-GST at 120 min were lower in propofol than in desflurane group (142.2 ± 75.4 vs. 205.7 ± 66.5, P = 0.023), and MEGX on day 2 was higher (0.092 ± 0.096 vs. 0.036 ± 0.020, P = 0.007). No differences between groups were observed with regard to plasma levels of aminotransferases, prothrombin time, and plasma factor V. Our study showed that in patients undergoing partial hepatectomy, propofol did not reduce MDA formation but seemed to display a protective effect on hepatic damages and liver function when compared to desflurane.

Cytogenetic damage after ischemia and reperfusion

Tourniquets are often used to provide a bloodless operating field. However, they carry the risk of adverse effects caused by DNA damage from the free radicals generated during postischemic reperfusion of the blood. The aim of this study was to evaluate the cytogenetic damage caused by postischemic reperfusion on peripheral lymphocytes of five women and six men undergoing total knee arthroplasty "bloodless" operation using samples received before, during, immediately, and 1 h after the operations. The sister chromatid exchange assay was applied to peripheral blood lymphocyte cultures and the levels of sister chromatid exchanges were analyzed as a quantitative index of genotoxicity, along with the values of mitotic index and proliferation rate index as qualitative indices of cytotoxicity and cytostaticity, respectively. We observed that postischemic reperfusion induced cytogenetic damages specifically through reperfusion. DNA effects were most pronounced after tourniquet release and declined afterward without returning to preischemic baseline values. Our findings suggest the presence of a functional association between postischemic reperfusion and cytogenetic damage that may have important clinical implications.

Protective effects of propofol against ischemia/reperfusion injury in rat kidneys

AIM

The purpose of this study was to investigate and compare the efficiency of propofol in the reduction of injury induced by free radicals in a rat model of renal ischemia/reperfusion (I/R).

METHOD

Twenty-four Wistar rats were divided into four groups in our study. Rats in the sham group underwent laparotomy and were made to wait for 120 min without ischemia. Rats in the control group were given nothing with ischemia-reperfusion. Rats in the I/R groups were given propofol (25 mg/kg) and 10% intralipid (250 mg/kg) ip, respectively, 15 min before the ischemia for 60 min followed by reperfusion for 60 min. The kidney tissues of the rats were taken under anesthesia at the end of the reperfusion period. Evaluation of biochemical malondialdehyde (MDA), superoxide dismutase, and catalase activities and histopathological analysis were performed with these samples.

RESULTS

I/R significantly increased MDA levels (p < 0.05). Histopathological findings of the control group confirmed that there was renal impairment by tubular cell swelling, interstitial edema, medullary congestion, and tubular dilatation. MDA levels were lower in the propofol group compared to control group (p < 0.05). In the propofol group, the level of histopathological scores is significantly decreased than control and intralipid groups in ischemia-reperfusion.

CONCLUSION

Our results demonstrate that I/R injury was significantly reduced in the presence of propofol. The protective effects of propofol may be due to their antioxidant properties. These results may indicate that propofol anesthesia protects against functional, biochemical, and morphological damage better than control in renal I/R injury.

Evaluation of DNA damage after tourniquet-induced ischaemia/reperfusion injury during lower extremity surgery

Ischemia/reperfusion (I/R) injury represents a source of substantial morbidity and mortality in various statuses that is, coronary bypass, myocardial infarction, and so on. Oxygen free radicals, formed during I/R, have been proposed as one of the main causes of tissue injury and play important role in I/R injury. Leucocytes have been shown to play an important role in the development of tissue injury after I/R. Accordingly, numerous studies have shown that even short-time I/R-induced DNA damage can be investigated in human peripheral leucocytes using the alkaline single-cell gel-electrophoresis assay (comet assay). After ischaemia, the genotoxic damage detected in human peripheral leucocytes locally in the reperfused tissue results in numerical, morphologic and biochemical alterations of all circulating white blood cells in the human organism. It leads particularly to the release of substantial amounts of oxygen radicals and other reactive agents. Simultaneously, local ischaemia in the reperfused tissue is extended to the whole body systemically through these activated inflammatory cells and, possibly, results in secondary detectable tissue damage in endothelial cells of the systemic circulation inducing prolonged DNA damage even in the early reperfusion period. Thus, we aimed to investigate whether the I/R during the routinely practised operation causes DNA damage, since other published studies were on animal and in vitro models and did not exactly reflect the operation procedure in the clinic. We measured DNA damage (single-strand breaks, oxidised purines and pyrimidines) by modified alkaline comet assay using two bacterial enzymes (formamidopyrimidine glycosylase (Fpg), endonuclease III (EndoIII)), which recognise oxidised purines and pyrimidine bases, in patients who had lower extremity surgery. There was no statistically significant difference in DNA damage between time periods (before surgery, after I/R; T1, T2 and T3). According to our findings, we indicate that at the molecular level DNA is damaged due to the I/R during the routinely practised operation; however, this effect could not be determined phenotypically. Thus, we may suggest that the surgeons and anaesthetist/operation room personnel could be informed about that fact and encouraged to use antioxidants and/or apply prophylaxis. Our findings showed that I/R injury did not induce DNA damage. Further studies of this approach are needed.

Total hip and knee replacement surgery results in changes in leukocyte and endothelial markers

BACKGROUND

It is estimated that over 8 million people in the United Kingdom suffer from osteoarthritis. These patients may require orthopaedic surgical intervention to help alleviate their clinical condition. Investigations presented here was to test the hypothesis that total hip replacement (THR) and total knee replacement (TKR) orthopaedic surgery result in changes to leukocyte and endothelial markers thus increasing inflammatory reactions postoperatively.

METHODS

During this 'pilot study', ten test subjects were all scheduled for THR or TKR elective surgery due to osteoarthritis. Leukocyte concentrations were measured using an automated full blood count analyser. Leukocyte CD11b (Mac-1) and CD62L cell surface expression, intracellular production of H(2)O(2 )and elastase were measured as markers of leukocyte function. Von Willebrand factor (vWF) and soluble intercellular adhesion molecule-1 (sICAM-1) were measured as markers of endothelial activation.

RESULTS

The results obtained during this study demonstrate that THR and TKR orthopaedic surgery result in similar changes of leukocyte and endothelial markers, suggestive of increased inflammatory reactions postoperatively. Specifically, THR and TKR surgery resulted in a leukocytosis, this being demonstrated by an increase in the total leukocyte concentration following surgery. Evidence of leukocyte activation was demonstrated by a decrease in CD62L expression and an increase in CD11b expression by neutrophils and monocytes respectively. An increase in the intracellular H(2)O(2 )production by neutrophils and monocytes and in the leukocyte elastase concentrations was also evident of leukocyte activation following orthopaedic surgery. With respect to endothelial activation, increases in vWF and sICAM-1 concentrations were demonstrated following surgery.

CONCLUSION

In general it appeared that most of the leukocyte and endothelial markers measured during these studies peaked between days 1-3 postoperatively. It is proposed that by allowing orthopaedic surgeons access to alternative laboratory markers such as CD11b, H(2)O(2 )and elastase, CD62L, vWF and sICAM-1, an accurate assessment of the extent of inflammation due to surgery per se could be made. Ultimately, the leukocyte and endothelial markers assessed during this investigation may have a role in monitoring potential infectious complications that can occur during the postoperative period.

The comparison of the effects of anesthetic doses of ketamine, propofol, and etomidate on ischemia-reperfusion injury in skeletal muscle

The fact that a considerable amount of clinical conditions suffering from ischemia-reperfusion injury (IRI) occur under general anesthesia has triggered researchers to focus on the effects of anesthetic drugs on IRI. Hence, the aim of this study was to compare the use of different anesthetic drugs in a skeletal IRI model. Tourniquet IRI method was performed and two experimental groups were established as sham-control and IRI group. Rats in each group were anesthetized either with thiopental, ketamine, propofol or etomidate. Malondialdehyde, superoxide dismutase, catalase, and glutathione peroxidase were measured in skeletal muscle via a spectrophotometer. Zinc, iron, copper, and selenium were evaluated by atomic absorption spectrophotometer. In rats anesthetized with thiopental (40 mg/kg, i.p.), malondialdehyde values in IRI group were higher and glutathion peroxidase levels were lower compared to sham-control group. However, superoxide dismutase and catalase activities were identical. On the other hand, while the level of zinc in IRI group attenuated, no differences in iron and copper values were determined. Rats anesthetized with ketamine (60 mg/kg), propofol (100 mg/kg), or etomidate (20 mg/kg) did not show increased malondialdehyde levels in comparison with control levels. While the drugs did not cause a distinction in the levels of superoxide dismutase, catalase, glutathion peroxidase, iron, and copper, zinc was in a lower level in IRI group compared to sham-control. In conclusion, ketamine, propofol, and etomidate, with anesthetic doses, denoted efficacious effects on IRI; hence the drugs might be preferred in certain operations with the risk of IRI.

Comparison of the effect of propofol and N-acetyl cysteine in preventing ischaemia-reperfusion injury

BACKGROUND AND OBJECTIVE

The aim of this study was to compare the effects of propofol and N-acetyl cysteine (NAC) on tourniquet-induced ischaemia-reperfusion injury by determining malonyldialdehyde, ischaemia-modified albumin, lactate, blood gas and haemodynamic levels in arthroscopic knee surgery.

METHODS

Sixty ASA I or II patients were randomized into three groups. Intrathecal anaesthesia was administered using 0.5% heavy bupivacaine in all patients. In group P, propofol was administered in a 0.2 mg kg(-1) bolus, followed by infusion at a rate of 2 mg kg(-1) h(-1); in group NAC, NAC was administered as an infusion at a rate of 5 mg kg(-1) h(-1), and, in group C (the control group), an equal volume of isotonic saline was administered to patients until 30 min after reperfusion. Blood samplings were obtained immediately before intrathecal anaesthesia (t1), 1 min before tourniquet release (t2), 5 min after tourniquet release (t3) and 30 min after tourniquet release (t4).

RESULTS

Plasma malonyldialdehyde, ischaemia-modified albumin and lactate levels increased significantly in group C at t3 and t4 compared with the baseline values. Plasma concentrations of malonyldialdehyde, ischaemia-modified albumin and lactate in groups P and NAC were significantly lower than those in group C at t3 and t4. In blood gas analyses, pH, HCO3 and base excess were found to be significantly lower at t3 and t4 compared with t1 and t2 in group C. Comparisons between groups P and NAC revealed no significant differences.

CONCLUSION

Small-dose infusions of both propofol and NAC appear to provide similar protection against ischaemia-reperfusion injury in arthroscopic knee surgery.

Mild episodes of tourniquet-induced forearm ischaemia-reperfusion injury results in leukocyte activation and changes in inflammatory and coagulation markers

Background

Monocytes and neutrophils are examples of phagocytic leukocytes, with neutrophils being considered as the 'chief' phagocytic leukocyte. Both monocytes and neutrophils have been implicated to play a key role in the development of ischaemia-reperfusion injury, where they are intrinsically involved in leukocyte-endothelial cell interactions. In this pilot study we hypothesised that mild episodes of tourniquet induced forearm ischaemia-reperfusion injury results in leukocyte activation and changes in inflammatory and coagulation markers.

Methods

Ten healthy human volunteers were recruited after informed consent. None had any history of cardiovascular disease with each subject volunteer participating in the study for a 24 hour period. Six venous blood samples were collected from each subject volunteer at baseline, 10 minutes ischaemia, 5, 15, 30, 60 minutes and 24 hours reperfusion, by means of a cannula from the ante-cubital fossa. Monocyte and neutrophil leukocyte sub-populations were isolated by density gradient centrifugation techniques. Leukocyte trapping was investigated by measuring the concentration of leukocytes in venous blood leaving the arm. The cell surface expression of CD62L (L-selectin), CD11b and the intracellular production of hydrogen peroxide (H₂O₂) were measured via flow cytometry. C-reactive protein (CRP) was measured using a clinical chemistry analyser. Plasma concentrations of D-dimer and von Willebrand factor (vWF) were measured using enzyme-linked fluorescent assays (ELFA).

Results

During ischaemia-reperfusion injury, there was a decrease in CD62L and an increase in CD11b cell surface expression for both monocytes and neutrophils, with changes in the measured parameters reaching statistical significance (p =< 0.05). A significant decrease in peripheral blood leukocyte concentration was observed during this process, which was measured to assess the degree of leukocyte trapping in the micro-circulation (p =< 0.001). There was an increase in the intracellular production of H₂O₂ production by leukocyte sub-populations, which was measured as a marker of leukocyte activation. Intracellular production of H₂O₂ in monocytes during ischaemia-reperfusion injury reached statistical significance (p = 0.014), although similar trends were observed with neutrophils these did not reach statistical significance. CRP was measured to assess the inflammatory response following mild episodes of ischaemia-reperfusion injury and resulted in a significant increase in the CRP concentration (p =< 0.001). There were also increased plasma concentrations of D-dimer and a trend towards elevated vWF levels, which were measured as markers of coagulation activation and endothelial damage respectively. Although significant changes in D-dimer concentrations were observed during ischaemia-reperfusion injury (p = 0.007), measurement of the vWF did not reach statistical significance.

Conclusion

Tourniquet induced forearm ischaemia-reperfusion injury results in increased adhesiveness, trapping and activation of leukocytes. We report that, even following a mild ischaemic insult, this leukocyte response is immediately followed by evidence of increased inflammatory response, coagulation activity and endothelial damage. These results may have important implications and this pilot study may lead to a series of trials that shed light on the mechanisms of ischaemia-reperfusion injury, including potential points of therapeutic intervention for pathophysiological conditions.

Effects of sevoflurane and propofol on ischaemia–reperfusion injury after thoracic-aortic occlusion in pigs

BACKGROUND

Thoraco-abdominal-aneurysm surgery predicts high mortality. Propofol and sevoflurane are commonly used anaesthetics for this procedure. Halogenated anaesthetics induce organ protection similar to ischaemic preconditioning. We investigated which anaesthetic regimen would lead to a better protection against ischaemia-reperfusion injury induced by temporary thoracic-aortic occlusion.

METHODS

Following initial fentanyl-midazolam anaesthesia for surgical preparation, 18 pigs were randomly assigned to two groups: group one received propofol (n=9) and group two sevoflurane (n=9) before, during, and after lower body ischaemia in an investigator blinded fashion. Ten animals without aortic occlusion served as time controls (propofol, n=5; sevoflurane, n=5). For induction of ischaemia, the thoracic aorta was occluded by a balloon-catheter for 90 min. After 120 min of reperfusion, the study anaesthetics were discontinued and fentanyl-midazolam re-established for an additional 180 min. Goal-directed therapy was performed during reperfusion. Fluid and catecholamine requirements were assessed. Serum samples and intestinal tissue specimens were obtained.

RESULTS

Severe declamping shock occurred in both study groups. While norepinephrine requirements in the sevoflurane group were significantly reduced during reperfusion (P<0.05), allowing cessation of catecholamine support in 4/9 animals, all 9/9 animals were still catecholamine dependent at the end of the experiment in the propofol group. Serum activities of lactate dehydrogenase, aspartate transaminase, and alanine aminotransferase were lower with sevoflurane (P<0.05). Small intestine tissue specimens did not differ histologically.

CONCLUSIONS

Use of sevoflurane compared with propofol attenuated the haemodynamic sequelae of reperfusion injury in our model. Release of serum markers of cellular injury was also attenuated.

Propofol and tourniquet induced ischaemia reperfusion injury in lower extremity operations

BACKGROUND AND OBJECTIVE

Extremity surgery with tourniquet to provide a bloodless field may be a good human model for ischaemia reperfusion (IR) injury. The aim of this study was to investigate the effects of three different modes of propofol use on tourniquet induced IR injury in lower extremity operations.

METHODS

Thirty-three consecutive ASA Grade I and II patients were randomized into three groups of 11 patients each. In the spinal group (Group S), after intrathecal anaesthesia, sedation was given with a propofol infusion at 2 mg kg-1 h-1 after a 0.2 mg kg-1 bolus dose and fentanyl 100 microg. In the general (Group G) and TIVA (Group T) groups, general anaesthesia was induced with propofol 2 mg kg-1 with fentanyl 100 microg and maintained with inhalation of halothane or infusion of propofol respectively. Venous blood samples were obtained at different time points for measurements of plasma malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) levels.

RESULTS

Plasma MDA levels were increased significantly in the Group G at 1 min before tourniquet release and 5 and 20 min after tourniquet release compared with before induction of general anaesthesia (baseline). Before intrathecal anaesthesia and before induction of general anaesthesia significantly decreased levels of MDA were observed both before and after tourniquet release compared to baseline. Plasma SOD and CAT concentrations were decreased significantly only at tourniquet release in the Group G compared with baseline. In the Groups S and T these enzymes were not changed significantly. Plasma GPx levels were not altered in any groups.

CONCLUSION

Propofol administration may inhibit lipid peroxidation and restore antioxidant enzyme levels in extremity surgery requiring tourniquet application.

Effects of acetylcysteine and ischaemic preconditioning on muscular function and postoperative pain after orthopaedic surgery using a pneumatic tourniquet

BACKGROUND AND OBJECTIVE

The use of a pneumatic tourniquet can induce muscular and neurological complications in the operated limb. The genesis of these injuries could involve an ischaemia/reperfusion phenomenon and a compression under the cuff. We evaluated effects of an antioxidant, acetylcysteine and ischaemic preconditioning on the rhabdomyolysis and postoperative pain following a knee ligamentoplasty using a pneumatic tourniquet.

METHODS

We included 31 patients scheduled for a knee ligamentoplasty randomly assigned in three groups (control, acetylcysteine 1200 mg the day before and 600 mg at the operative day, ischaemic preconditioning).

RESULTS

There was a moderate rise in myoglobin and creatinine phosphokinase with no significant difference between the three groups. The muscular functional parameters were similar in all the groups. However, the morphine consumption within the first 48 h was smaller in the treatment groups (0.22 +/- 0.31 mg kg-1 and 0.22 +/- 0.23 mg kg-1 in the preconditioning and antioxidant groups, respectively) than in the control group (0.47 +/- 0.33 mg kg-1, P <0.05).

CONCLUSIONS

Acetylcysteine and ischaemic preconditioning do not decrease the extent of rhabdomyolysis related to the use of a pneumatic tourniquet and do not improve the postoperative muscle recovery. On the other hand, they allow a significant reduction in the postoperative morphine consumption.

Enhanced lipid peroxidation in tourniquet-release mice

BACKGROUND

The pathogenesis of ischemia-reperfusion involves generation of reactive oxygen and resulting lipid peroxidation. However, investigation that ischemia-reperfusion following tourniquet release enhances lipid peroxidation is insufficient.

METHODS

Tourniquet was applied to a unilateral hind limb of mice for 3h followed by 5-, 15-, 30- and 60-min release. To examine superoxide production immunohistochemically in ischemia-reperfusion muscles, a primary antibody directed to 4-hydroxy-nonenal (HNE) was used. Furthermore, we analyzed 7alpha- and 7beta-hydroperoxycholest-5-en-3beta-ol, 7alpha- and 7beta-hydroxycholesterol, and 7-ketocholesterol by HPLC in the gastrocnemius muscles, kidneys, liver, heart and lungs of mice after 1-h reperfusion.

RESULTS

Increased HNE immunoreactivitiy was observed in the tourniquet-applied side of gastrocnemius muscles of hind limb particularly after 5-min reperfusion. All the oxysterols were significantly higher in the gastrocnemius muscles of the tourniquet-applied side than of the contralateral muscles. Oxysterols were elevated in the kidneys and the liver. Together with the presence of high blood urea nitrogen, these data indicate that the kidney is vulnerable to ischemia-reperfusion.

CONCLUSIONS

The enhanced oxidative stress due to ischemia-reperfusion appears to increase HNE in muscle and oxysterols by peroxidation not only in the gastrocnemius muscles but also in the kidneys and liver.

Reactive oxygen species as mediators of cardiac injury and protection: the relevance to anesthesia practice

Reactive oxygen species (ROS) are central to cardiac ischemic and reperfusion injury. They contribute to myocardial stunning, infarction and apoptosis, and possibly to the genesis of arrhythmias. Multiple laboratory studies and clinical trials have evaluated the use of scavengers of ROS to protect the heart from the effects of ischemia and reperfusion. Generally, studies in animal models have shown such effects. Clinical trials have also shown protective effects of scavengers, but whether this protection confers meaningful clinical benefits is uncertain. Several IV anesthetic drugs act as ROS scavengers. In contrast, volatile anesthetics have recently been demonstrated to generate ROS in the heart, most likely because of inhibitory effects on cardiac mitochondria. ROS are involved in the signaling cascade for cardioprotection induced by brief exposure to a volatile anesthetic (termed "anesthetic preconditioning"). ROS, therefore, although injurious in large quantities, can have a paradoxical protective effect within the heart. In this review we provide background information on ROS formation and elimination relevant to anesthetic and adjuvant drugs with particular reference to the heart. The sources of ROS, the means by which they induce cardiac injury or activate protective signaling pathways, the results of clinical studies evaluating ROS scavengers, and the effects of anesthetic drugs on ROS are each discussed.

Effect of low-dose N-acetyl-cysteine infusion on tourniquet-induced ischaemia-reperfusion injury in arthroscopic knee surgery

BACKGROUND

Temporary occlusion of blood flow is used during arthroscopic knee surgery in order to provide a bloodless surgical field. The resulting ischaemia-reperfusion causes lipid peroxidation, which contributes to tissue injury. The aim of the study was to investigate the effect of low-dose n-acetyl cysteine (NAC) infusion on oxidative stress by determining malondialdehyde (MDA) levels during arthroscopic knee surgery.

METHODS

Thirty patients, ASA I - II, undergoing arthroscopic knee debridement under a tourniquet were divided into NAC and control groups. Anaesthesia was induced with propofol, fentanyl and vecuronium bromide and maintained with desflurane in an equal parts O(2)-N(2)O mixture. In the NAC group, an infusion of NAC, 5 mg kg(-1).h(-1), was started after intubation, and continued until extubation. An equal volume of saline was infused to the control group. Duration of ischaemia, anaesthesia time, total dose of NAC infused were also recorded. Venous blood and synovial membrane tissue samples were obtained 10 min after the onset of NAC infusion but before tourniquet inflation (t1), after 30 min of ischaemia (t2), and after 5 min of reperfusion following tourniquet release (t3).

RESULTS

Plasma MDA levels were significantly lower in the NAC group on reperfusion. There were no differences between the groups in tissue MDA levels at ischaemia and reperfusion times.

CONCLUSION

Low-dose n-acetyl cysteine infusion attenuates lipid peroxidation and ischaemia-reperfusion injury in arthroscopic knee surgery requiring tourniquet application.

Effects of tourniquet-induced ischemia on the release of proopiomelanocortin derivatives determined in peripheral blood plasma

Proopiomelanocortin (POMC) is expressed in pituitary, central nervous system, and in a few peripheral tissues. This study addresses the hypothesis that metabolic stressors, such as acidosis, may induce the release of POMC derivatives into the cardiovascular system not only from the pituitary but also from other sites of POMC expression. In our study, we investigated the liberation of POMC derivatives from peripheral tissues under a state of acidosis achieved by tourniquet-induced ischemia, alteration of lactate concentration, and base excess. In eight patients undergoing knee arthroplasty under spinal anesthesia, catheters were inserted into the femoral vein proximally to thigh tourniquet location. Blood was drawn from these catheters 5 min before and 40 s, 5 min, and 10 min after tourniquet deflation to measure plasma concentrations of N-acetyl-beta-endorphin immunoreactive material (IRM), beta-endorphin IRM, authentic beta-endorphin, adrenocorticotropin, lactate, pH, and base excess. In five of eight patients, we found a significant increase of beta-endorphin IRM levels 40 s after tourniquet deflation compared with predeflation levels; 5 and 10 min after tourniquet deflation, the beta-endorphin IRM levels were below the detection limit. Thus beta-endorphin IRM was released from ischemic limb tissues into the cardiovascular system. Only a small part of the determined beta-endorphin IRM corresponded to authentic beta-endorphin. Forty seconds after tourniquet deflation, the beta-endorphin IRM concentration correlated with base excess (r < 0.71; P < 0.05); no significant correlations were found with pH or lactate levels. Thus it was shown here for the first time that ischemic stress may induce the release of beta-endorphin IRM from nonpituitary tissues.

Propofol displays no protective effect against hypoxia/reoxygenation injury in rat liver slices

Using precision-cut liver slices (20-25 mg wet weight) from male Wistar rats, we examined whether clinically relevant propofol concentrations have hepatoprotective or -toxic effects during hypoxia/reoxygenation. Slices were preincubated for 2 h in sealed roller vials (three slices per vial) containing Waymouth's medium (37 degrees C; 95% oxygen/5% CO(2)). Then, propofol or Intralipid was added to create four different groups (control, Intralipid, small-concentration propofol [0.5-1.5 micro g/mL], and large-concentration propofol [2.0-6.0 micro g/mL]). Thereafter, each group was incubated for 4 h under 95% oxygen/5% CO(2) (no hypoxia) or for 2 h under 100% nitrogen plus 2 h under 95% oxygen/5% CO(2) (hypoxia/reoxygenation). Slice viability and hypoxia/reoxygenation injury were assessed at 2, 3, and 4 h after incubation began by using the slice intracellular K(+) concentration, energy status (adenosine triphosphate content, total adenine nucleotides content, and energy charge), and liver enzyme leakage (aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase). Propofol and Intralipid caused a significant delay in energy charge recovery in comparison with the control. There were no significant differences between the propofol groups and the other two groups in intracellular K(+) content or liver enzyme leakage. Propofol had no hepatotoxic effect under no-hypoxia conditions in rat liver slices, nor did it have a protective effect against hypoxia/reoxygenation-induced hepatic injury.

IMPLICATIONS

Propofol had no hepatotoxic effect under no-hypoxia conditions in rat liver slices, nor did it have a protective effect against hypoxia/reoxygenation-induced hepatic injury.