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REGIONAL ANESTHESIA

Ketamine Sedation During Spinal Anesthesia for Arthroscopic Knee Surgery Reduced the Ischemia-Reperfusion Injury Markers

Fatma Saricaoglu, MD^*, Didem Dal, MD^*, Akgün Ebru Salman, MD^*, Mahmut Nedim Doral, MD, Kamer Klnç, MD, and Ülkü Aypar, MD^*

*Department of Anaesthesiology and Reanimation, Department of Sports Medicine and Orthopaedics, and the Department of Biochemistry, Hacettepe University Faculty of Medicine, Ankara, Turkey

Address correspondence and reprint requests to Fatma Saricaoglu, Hacettepe University Medical Faculty, Department of Anaesthesiology and Reanimation, 06100 Sihhiye/Ankara Turkey. Address e-mail to fatmasaricao{at}yahoo.com.

	Abstract

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We studied the effect of ketamine sedation on oxidative stress during arthroscopic knee surgery with tourniquet application by determining blood and tissue malonyldialdehyde (MDA) and hypoxanthine (HPX) levels. Thirty ASA I–II patients undergoing arthroscopic knee surgery with tourniquet were randomly divided into two groups. Spinal anesthesia induced with 12.5 mg bupivacaine was administered to all patients. In the ketamine group, after IV administration of 0.01 mg/kg midazolam, a continuous infusion of ketamine (0.5 mg · kg^–1 · h^–1) was used until the end of surgery whereas the placebo group received a volume-equivalent placebo infusion. Ramsey Sedation Scale (RSS) was used for assessing the sedation level. Venous blood and synovial membrane tissue samples were obtained before ketamine infusion, at 30 min of tourniquet ischemia, and at 5 min after tourniquet deflation for MDA and HPX measurements. Tissue MDA and HPX levels were significantly less in the ketamine group than the control group after reperfusion. RSS scores were higher in the ketamine group without any adverse effect. We conclude that ketamine sedation attenuates lipid peroxidation markers in arthroscopic knee surgery with tourniquet application.

	Introduction

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Arthroscopic knee surgery requires a bloodless field, usually obtained by tourniquet application. However, tourniquet application causes metabolic changes that depend on the tourniquet phase (inflation = ischemia, deflation = reperfusion), the time duration of tourniquet inflation, and the anesthetic technique (1–3). Prolonged ischemia with tourniquet inflation and subsequent reperfusion causes lipid peroxidation, resulting in tissue injury (4). Lipid peroxidation occurring during ischemia-reperfusion (I/R) is a chain reaction leading to oxidation of polyunsaturated fatty acids that, in turn, disrupts the structure of biological membranes and produces toxic metabolites such as malonyldialdehyde (MDA) (5). The hypoxia produced during ischemia leads to the degradation of adenosine triphosphate to adenosine monophosphate (AMP) and to the subsequent cellular energy depletion. AMP is further degraded to adenosine or inosine monophosphate, then to inosine, and finally to xanthine and hypoxanthine (HPX). When oxygen is reintroduced with perfusion, the HPX concentration is increased with high activity of the enzyme xanthine oxidase (XO). The irreversible transformation of xanthine dehydrogenase (XD) into XO during ischemia results in increased reactive oxygen species production and subsequent injury (6,7). Therefore, HPX and MDA have been described as sensitive markers for I/R injury.

The time-dependent depletion of adenine nucleotide and the rate of conversion of XD to XO associated with widespread tissue damage in skeletal muscle during I/R were first reported by Lindsay et al. (8). Concannon et al. (4) showed a significant increase in MDA production within 2 h in a rabbit model of tourniquet-induced skeletal muscle I/R injury.

Ketamine, a dissociative anesthetic, protects neurons against I/R-induced lipid peroxidation (9,10). Intraoperative ketamine was also found to be effective against postarthroscopy hyperalgesia and tourniquet-induced increase in arterial blood pressure in two studies (11,12). However, the role of ketamine in muscular I/R injury has not been evaluated.

This study investigated the effect of ketamine infusion on tourniquet induced I/R injury during arthroscopic knee surgery by measuring MDA and HPX levels.

	Methods

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The study was approved by the Hospital Ethics Committee and written informed consent was obtained from each of the participants. Thirty ASA physical status I–II patients undergoing arthroscopic anterior cruciate ligament reconstruction (ACLR) were enrolled in this study.

Patients were randomized using a sequential number list to enter either group ketamine (n = 15) or group control (n = 15). Patients with metabolic, renal, or hepatic disturbances, a recent history of any antioxidant drug use, or a history of chronic pain were excluded from the study. Total protein, albumin, C-reactive protein, and sedimentation rate were all within normal ranges in preoperative measurements.

All patients were instructed about the use of the patient-controlled analgesia (PCA) device (Abbott life care 4200; Abbott Critical Care Systems, Morgan Hill, CA) and 10-cm visual analog scale (VAS; 0 = no pain and 10 = the worst possible pain) preoperatively. All patients were premedicated with 10 mg diazepam orally 45 min before surgery. With noninvasive standard monitoring in the operating room, spinal anesthesia (L3-4) was performed for all patients with 12.5 mg bupivacaine. The maximum upper levels of sensory block were Thoracal 9 or above at the beginning of the operation. Midazolam (F. Hoffmann-La Roche Ltd., Basel, Switzerland) 0.01 mg/kg was administered IV to all patients before surgery. In the ketamine group, a ketamine (Parke-Davis, Pfizer) IV infusion was started immediately after the midazolam at a dose of 0.5 mg · kg^–1 · h^–1 and continued until the end of the operation. The ketamine solution was prepared by diluting ketamine with saline to a final concentration of 5 mg/mL. The equivalent volume of saline was infused in the control group. The Ramsey Sedation Scale (RSS; 1 = anxious and agitated, 2 = cooperative and tranquil, 3 = drowsy but responsive to command, 4 = asleep but responsive to glabellar tap, 5 = asleep with a sluggish response to tactile stimulation, 6 = asleep and no response) was used to measure sedation before and at 5, 10, 20, 30, 45, 60, and 80 min after administration of ketamine sedation. We also evaluated potential side effects of ketamine assessing respiratory depression (sedation score >4 and respiration <10 breaths/min), nausea, vomiting, pruritus, and dysphoria (including hallucinations and dreams) (13).

The tourniquet was applied at a pressure approximately twice the systolic arterial blood pressure. No blood transfusions were used; the fluid deficits were corrected with normal saline during the operation.

Sequential venous blood samples were obtained from the antecubital vein of the contralateral arm. The dorsal vein of the other hand was used for IV fluid and ketamine infusions. Blood samples and synovial tissue samples for lipid peroxidation analysis were obtained immediately before ketamine administration (t1), at 30 min of tourniquet inflation (t2), and 5 min after tourniquet deflation (t3). Because the tourniquet was not inflated at t1, synovial fluid was obtained in the same manner as tissue for basal measurement at this time point.

After surgery, the patients were observed in the recovery room until the motor block resolved. Time to the first morphine demand delivered by PCA (1 mg mL of normal saline, 1 mL bolus, 5-min lockout period and no continuous infusion) and VAS score at the time of analgesic requirement were recorded. Age, sex, weight, and tourniquet time were recorded for each patient at the time of study.

Blood samples were immediately centrifuged at 8000g for 5 min. Blood and tissue samples were placed on ice and the supernatant and synovial membrane tissue samples were stored at –20°C until analysis. Frozen tissues were immediately weighed and homogenized in 10 volumes of ice-cold phosphate buffer (50 mmol^–1L^–1; pH 7.4) using a glass-glass homogenizer. The homogenate (0.5 mL) was mixed with 3 mL of 1% H₃PO. After the addition of 1 mL thiobarbutiric acid reagent (0.67%), the tubes were heated in boiling water for 45 min. The color formed was extracted into 4 mL of n-butanol. After centrifugation the color intensity of the butanol layer was measured at 532 nm using a Shimadzu UV-120–02 model spectrophotometer. Tetramethoxypropane was used as the standard and concentrations of thiobarbutiric acid reacting substance were calculated as nanomoles of MDA per gram of wet tissue. For detecting lipid peroxide concentrations of plasma thiobarbutiric acid reacting substance, 0.1 mL of trichloroacetic acid (25 g trichloroacetic acid in 10 mL distilled water) was added to 0.5 mL plasma by vigorous shaking. The resulting mixture was reacted with 1 mL of thiobarbutiric acid 0.67% and then heated in boiling water for 30 min. The samples were centrifuged at 2000g for 15 min and the absorption was measured at 532 nm. Plasma levels of lipid peroxides were calculated as micromoles per liter.

All data are presented as mean ± sd. Tissue MDA levels at the ischemia period were used to calculate the statistical power. In our previous study, a sample size estimate indicated that 15 patients per group would give a power of 100% level () of 0.01.

A one-sample Kolmogorov-Smirnov test was used to analyze the normal distribution of the variables obtained. Nonparametric tests were performed for data that did not demonstrate a normal distribution. Age was compared between groups with the Mann-Whitney U-test. Gender was compared between groups with the ² test. Student’s t-test was used for comparing weight and duration of ischemia. Repeated-measures analysis of variance was performed for comparing the time effect and the differences between groups in plasma and tissue MDA and HPX levels. P < 0.05 was considered as statistically significant. Bonferroni correction was used when performing post hoc analysis of the repeated measures.

	Results

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There were no significant differences between the groups in age, sex, weight, or duration of tourniquet application (Table 1). All patients underwent ACLR performed by the same surgeon. No patient was excluded from the study because of inadequate spinal anesthesia. The maximum upper levels of sensory block were T9 at the beginning of the operation and T12-L5 after the operation. Hemodynamic measurements were not significantly different between groups or within time (Table 2). The first analgesic need occurred at 40 ± 15 min and 60 ± 18 min in the control and ketamine groups, respectively (P < 0.05). The VAS pain score was 3.0 ± 0.6 at the first analgesia request in the ketamine group whereas it was 6.0 ± 0.6 in the control group (P < 0.001).

The ketamine group RSS scores were higher than the control group RSS scores (Table 3). After the ketamine infusion was discontinued the RSS scores returned to 2–3 within 10 min and the patients were transferred to the recovery room. There was no respiratory depression, nausea, vomiting, nightmares or hallucinations in the ketamine or control groups.

There was no significant difference in baseline serum MDA, tissue MDA, or tissue HPX levels between groups. There was a significant increase in serum MDA levels at ischemia compared with basal values in both groups (P = 0.001 control group; P = 0.008 ketamine group). However, 5 min after reperfusion (t3) serum MDA levels were not significantly different than ischemia levels (t2) (P = 0.049 control group; P = 0.009 ketamine group), but they remained significantly higher compared with baseline values (t1) (P = 0.002 control group; P = 0.049 ketamine group) (Fig. 1).

View larger version (32K): [in this window] [in a new window]   Figure 1. Plasma malonyldialdehyde (MDA) concentration levels of groups. *P < 0.05 compared with basal values.

Tissue MDA levels were also increased significantly in the ischemia period (t2) in both groups (P = 0.001). However, 5 min after reperfusion, although tissue MDA levels were increased almost eightfold in the control group (141.09 ± 22.93 at t2 versus 986.2 ± 108.32 (nmol g^–1) at t3, P = 0.0001), they were slightly decreased in the ketamine group (118.74 ± 23.44, at t2 versus 100.11 ± 23.64 at t3, P = 0.053). There was a significant difference in tissue MDA levels between groups in the I/R period (Fig. 2).

View larger version (21K): [in this window] [in a new window]   Figure 2. Tissue malonyldialdehyde (MDA) concentration levels of groups. #P < 0.05 for differences between groups; *P < 0.05 compared with basal values.

In both groups, synovial tissue HPX concentrations varied little from their respective baselines during ischemia (22.45 ± 5.67 versus 23.66 ± 6.00 nmol/g in the control group, 22.33 ± 5.34 versus 23.50 ± 6.01 nmol/g in the ketamine group). In contrast, reperfusion caused a marked increase in tissue HPX concentration in both groups (Fig. 3). This increase was markedly less in the ketamine group (52.00 ± 6.68 versus 32.41 ± 7.03 nmol/g).

View larger version (33K): [in this window] [in a new window]   Figure 3. Tissue hypoxanthine (HPX) concentration levels of groups. #P < 0.05 for differences between groups; *P < 0.05 compared with basal values.

	Discussion

Top Abstract Introduction Methods Results Discussion References

 
We hypothesized that ketamine could play a beneficial role in reducing injury from acute muscular ischemia and reperfusion produced by tourniquet application during ACLR. In this model of acute muscular I/R injury, we examined the effect of ketamine on lipid peroxide formation. Our main finding was that ketamine at a sedation dose attenuated synovial tissue MDA and HPX production in the early reperfusion period. Ketamine also was associated with higher sedation levels but without any adverse effects.

ACLR surgery with tourniquet is a good human model for excessive production of oxidants. Tourniquet time is moderate and, despite an arthroscopic technique, this surgery is painful postoperatively. We prefer to administer ketamine by infusion for sedation using half of the dose that had been proven effective in a study by Deng et al. (14). While determining the protective effect of ketamine against I/R injury in this study, we evaluated the side effects as well. The reason for choosing spinal anesthesia was that less hemodynamic and metabolic changes were seen with the tourniquet in patients undergoing spinal anesthesia compared with general anesthesia.

Previous studies have reported improved postoperative analgesia after ketamine administration. Menigaux et al. (12) demonstrated that adding preemptive intraoperative small-dose ketamine improves postoperative analgesia. In another study, Menigaux et al. (15) used IV ketamine preoperatively or postoperatively as a single dose and showed that the analgesic effect of ketamine is not dependent on the timing of administration. In our study, the first analgesic request in the ketamine group was significantly longer and VAS scores were lower than in the control group after motor function had returned while in the recovery room.

Although skeletal muscle is thought to be relatively insensitive to the deleterious effects of ischemia and subsequent reperfusion, injury can occur as a result of ischemia such as tourniquet application (7). Ischemia of the extremities is associated with lipid peroxidation, an autocatalytic mechanism leading to oxidative destruction of cell membranes, which may lead to the production of toxic reactive metabolites and cell death. Lipid peroxidation, as a free radical generating system, may be closely related to I/R-induced tissue damage; MDA is a good indicator of the degree of lipid peroxidation (5). We also used HPX as another lipid peroxidation degradation product in our study. Other markers that can be measured for lipid peroxidation are enzymes and oxygen-free radicals in a chain reaction, although measurements of these markers are not as easily evaluated. Oxygen-free radicals or lipid peroxides are short=-lived and difficult to measure directly. Thus, MDA, a more stable and longer-living degradative product of lipid peroxides, is often assayed as reflecting lipid peroxidation level (4,8,9).

Indstrom et al. (16) reported that in a rat hindlimb tourniquet ischemia model, a several-fold increase of intracellular HPX occurred during ischemia, whereas uric acid formation is observed only after reperfusion. Also Kawasaki et al. (17) and Korth et al. (18) demonstrated that HPX is a valuable marker for I/R injury, especially in the ischemia period. MDA is a marker that increases at reperfusion as an indicator of free radicals with larger concentrations of free radicals.

The role of anesthetics in I/R injury is of interest. The effect of another IV anesthetic, propofol, in attenuating lipid peroxidation as a consequence of tourniquet-induced I/R injury has been demonstrated (19). The ability of ketamine to inhibit retinal membrane lipid peroxidation has been demonstrated in bovines in vitro (20). The basis for the protective effect of ketamine against neuronal I/R injury may relate to its ability to prevent calcium influx by antagonizing N-methyl-d-aspartate receptors (21). Another possibility that has been suggested is that by increasing blood flow of the target tissue, ketamine minimizes ischemia and its associated damage (21). However in our study, despite the lower levels of tissue MDA in the ketamine group during ischemia, there were no significant differences in serum MDA levels between groups.

Roytblat et al. (22) reported that a single dose of ketamine 0.25 mg/kg administered before cardiopulmonary bypass suppressed the increase in serum interleukin-6 levels. Ketamine also inhibited tumor necrosis factor- production (in a dose-dependent manner) and attenuated leukocyte adherence and neutrophil oxygen radical production in vitro. One mechanism for not being able to demonstrate a decrease in plasma MDA in our study may have been the migration of neutrophils to the injured muscle. If the main action of ketamine in reducing reperfusion injury is by attenuating neutrophil adherence, this effect might be greater in the muscle than in the plasma. However, further studies are required to evaluate the mechanism.

Like MDA, HPX concentrations were also increased in the reperfusion period. The relatively low levels of tissue MDA and HPX levels after reperfusion in the ketamine group were not accompanied by the concurrent plasma MDA levels. This might have been a result of the lack of time required for MDA to increase in plasma samples because the reperfusion period in our model was quite short.

Although these findings suggest that a continuous ketamine infusion in combination with midazolam can provide effective sedation and less lipid peroxidation injury, there were limitations in the study design. First, the reperfusion period was short because of the nature of the surgery. Second, we did not evaluate longer outcome variables such as mobility of the operated knee or first walking time and thus may have missed the delayed beneficial effect. Moreover, we did not assess immune function and infection markers after the operation.

In conclusion, ketamine infusion with midazolam provided satisfactory intraoperative sedation without adverse effect and attenuated markers of I/R injury in arthroscopic knee surgery requiring tourniquet application under spinal anesthesia.

	Footnotes

 
Accepted for publication February 1, 2005.

	References

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Saricaoglu, F. Articles by Aypar, U. Search for Related Content PubMed PubMed Citation Articles by Saricaoglu, F. Articles by Aypar, U. Related Collections Anesthetic Techniques Pain Pharmacology