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Department of Anaesthesiology and Intensive Care Medicine, Helsinki University Hospital, Helsinki, Finland
Address correspondence and reprint requests to Merja Laisalmi, MD, Department of Anaesthesiology and Intensive Care Medicine, Helsinki University Hospital, Surgical Hospital, PO BOX 263, 00029 HUS, Helsinki, Finland. Address e-mail to merja.laisalmi{at}hus.fi
| Abstract |
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Implications: The different kinetics of N-acetyl-ß-D-glucosaminidase indexed to urinary creatinine and serum inorganic fluoride during and after sevoflurane anesthesia suggest that the observed mild renal tubular function deterioration is not caused by inorganic fluoride. Administration of ketorolac IM is therefore considered safe in adequately hydrated healthy adult patients given sevoflurane anesthesia.
| Introduction |
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Nonsteroidal antiinflammatory drugs (NSAIDs) are commonly given intraoperatively to control postoperative pain (4). By blocking the cyclooxygenase enzymes, the NSAIDs also block the synthesis of prostaglandin E2 and I2, which are important renal vasodilators (5). Clinically, this renal vasoconstrictive effect of NSAIDs is reflected in decreased urine output in the postoperative period (6).
We assume that the combination of two potential renal toxins could be harmful to the kidneys. Sensitive markers of both renal tubular damage and ischemic renal insult were used in the present study to detect even subclinical renal toxicity when ketorolac was given in combination with sevoflurane anesthesia.
| Methods |
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The patients were anesthetized with propofol 2 mg · kg-1, fentanyl 2 µg · kg-1, and glycopyrrolate 0.2 mg IV. Tracheal intubation was facilitated with cisatracurium 0.15 mg · kg-1. Anesthesia was maintained with sevoflurane in oxygen-air mixture (FIO2 0.4). Ventilation was controlled with fresh gas flow of 46 L/min using a semiclosed system (Engström ECS 20; Engström, Stockholm, Sweden) to maintain end-tidal (ET) carbon dioxide tension (ETCO2) at 4.55.0 kPa. The end-tidal concentration of sevoflurane was analyzed with a Capnomac Ultima capnograph (Datex, Helsinki, Finland), which was calibrated immediately before anesthesia. The concentration of sevoflurane was adjusted to maintain mean arterial pressure (MAP) within 20% of baseline and above a minimum of 60 mm Hg. The MAC hours of sevoflurane were calculated from the ET concentration of the anesthetic and duration of the exposure. If the heart rate increased more than 30% of the baseline value or over 90 bpm and did not respond to an increased concentration of sevoflurane, a bolus of alfentanil 0.5 mg IV was given.
The surgical blood loss was measured by weighing the cotton swabs used during surgery. The amount of blood suctioned from the surgical area was measured. A 70-cm catheter was inserted via the basilic vein to the superior caval vein to monitor central venous pressure (CVP) and to obtain blood samples. Correct placement of the catheter was verified recording intraatrial electrocardiogram using AlphaCard®(7) (B. Braun, Melsungen, Germany). Ringers acetated solution (Ringer-Acetat®, Pharmacia 38 Upjohn, Stockholm, Sweden) and 6% hydroxyethyl starch solution (Plasmafusin 6%®, Kabi Pharmacia, Sweden) were used to maintain CVP at 612 mm Hg. A urinary bladder catheter was inserted to measure urine output and to collect urine samples. If the urine output was <0.5 mL/kg/h and CVP was less than 6 mm Hg, an additional bolus of 300500 mL of Ringers acetated solution was given.
Samples for the analyses of serum and urine fluoride, ß2-M, and urine NAG/crea (units of urinary NAG activity per gram of urinary creatinine) were collected preoperatively, after 2 h of anesthesia, 2 and 12 h after the end of anesthesia, as well as on the first and on the second postoperative days (PODs). Samples for the assays of serum and urine sodium, potassium, osmolality, and serum erythropoietin (EPO), serum urea, and creatinine concentrations were taken preoperatively, 12 h after the end of anesthesia, and on the first and second POD. Hemoglobin and hematocrit were measured preoperatively, on the first POD and additionally when needed. Urine oxygen tension (PuO2) was determined every 20 min in the operating room and in the postanesthesia care unit (PACU).
The concentrations of F- were determined by a method modified from that of Fry and Taves (8). A fluoride selective combination electrode Orion model 9609(Orion Research Incorporated, Boston, MA) was used for the measurement on Parafilm "M" (American National Can, Greenwich, CT) placed on 16-mm cell culture wells. Before measurement, 200 µL of acetate buffer (acetate-NaOH 1 mol · L-1, pH 5.2, NaCl 1 mol · L-1), and 10 µL of sodium fluoride 20 µmol · L-1 were added to 190 µL of serum.
The activity of U-NAG was determined by using 3-cresonsulphonphtalein-N-acetyl-ß-glucosamine as a substrate (Boehringer Mannheim Biochemica, Mannheim, Germany). The method was adapted to a Kone Specific® random access analyzer (Kone Instruments, Helsinki, Finland). Kinetic follow-up of the reaction was used instead of determination of end point absorbance. Urine NAG and creatinine values were measured from spot samples. The activity of NAG was normalized to creatinine concentration and expressed as U-NAG/crea (9).
Urine oxygen tension as a marker of renal medullary homeostasis was measured with a blood gas analyzer (Synthesis 35®; Instrumentation Laboratory, Laboratories Scandinavia, Helsinki, Finland) from the samples taken from fresh urine in the urinary catheter. EPO, a marker of tubulointerstitial function was analyzed using an in-house radioimmunologic method with reagents from Medix Diacor (Espoo, Finland) and an international reference standard (second international reference preparation 67/343), and serum and urine ß2-M samples were analyzed using time-resolved fluoroimmunoassay with dissociation enhanced lanthanide fluoroimmunoassay (DELFIA) ß2- microkit® (Wallac, Turku, Finland). The analyses of serum and urine sodium, potassium and creatinine concentrations as well as serum and urine osmolality and serum urea concentration were performed in the clinical laboratory of the hospital.
Postoperatively the patients were observed for two hours in the PACU. Heart rate, MAP and CVP were measured during the anesthesia and the PACU stay. Postoperative pain was scored using a visual analog scale from 110, and if the patient scored
4 she was given morphine 0.05 mg · kg-1 IV. Before discharge to the ward the patients were given a patient-controlled analgesia device programmed to deliver a dose of morphine 2 mg IV when required, with a lock-out time of 8 min and no more than four doses per hour. Postoperative nausea was treated with droperidol and ondansetron as needed.
Data within a group were analyzed using one-way analysis of variance. For differences between the two groups, two-way analysis of variance for repeated measures or Students unpaired t-test were used. Fishers protected least significance difference test was used to test significant changes. Calculations were performed using Stat View 5.0.1(SAS Institute, San Francisco, CA). Data are expressed as mean ± SD (tables) or SEM (figures). A probability value of <0.05 was considered statistically significant.
| Results |
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Urine sodium concentration decreased in Group K on the first POD (P < 0.05 compared with the preanesthetic value) and returned to the preanesthetic level on the second POD. Serum sodium concentration remained within the normal range during the study period. There was a significant decrease in serum potassium in Group C (P < 0.05) although the concentrations remained within the reference limits. Serum osmolality decreased in both groups after 12 h of anesthesia and returned to the preanesthetic levels, urine osmolality remaining reduced during the first and second POD. Serum creatinine and urea decreased in both groups during the first 24 h after anesthesia (Table 3).
There were no significant differences in CVP or urine output during the perioperative period ( Table 4).
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| Discussion |
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The renal toxic threshold for serum F- concentration is considered to be 50 µmol/L based on the experiences of methoxyflurane anesthesia (1). Methoxyflurane is metabolized to F- in the kidneys to a significantly larger extent than sevoflurane (2). This may be one reason that, in studies with sevoflurane, serum F- concentrations exceeding 100 µmol/L have been measured with no clinical renal deterioration. Compound A is another fluorine containing product of reaction between sevoflurane and desiccated carbon dioxide (CO2) absorbent (10). Compound A is toxic in animal tests (11) but there have been no clinical signs of renal toxicity in humans (12). In our study, moderately high fresh gas flows without a CO2 absorber were used, thus eliminating the role of Compound A.
Nonselective cyclooxygenase enzyme-blocking NSAIDs have caused vasoconstriction in the renal vasculature (5), especially renal arterioles. The inhibition of prostaglandin synthesis may compromise renal blood flow and glomerular filtration rate in connection with the effects of surgical stress. These harmful effects have been seen in elderly and hypovolemic patients in connection with hypotensive periods during anesthesia (13). Adequate volume loading protects renal function in connection with the use of radiographic contrast media (14). In our study, special attention was paid to prevention of dehydration and hypotension, the well-known risk factors of NSAID-induced renal damage.
Higuchi et al. (3) showed a significant increase in U-NAG/crea ratio in patients with serum F- concentrations exceeding 50 µmol/L after sevoflurane anesthesia. This change occurred on the second POD. They did not control the intravascular fluid administration of the patients who also received potentially nephrotoxic antibiotics. Intraoperatively, a tourniquet on the thigh or arm was used in the majority of the patients. The unavoidable ischemic and compression tissue injury may also have harmful effects on renal function (15). Thus several factors possibly affecting renal function were present.
We noted an increase in the U-NAG/crea in both groups when the patients had been two hours under anesthesia. At that time the urine NAG/crea was increased. All of the patients were exposed to surgery and 15 of them also to the first dose of ketorolac. The peak serum concentrations of F-, however, were detected two hours after the end of anesthesia. The change in U-NAG/crea returned to the baseline during the first POD. Thus, the high F- concentrations or the administration of ketorolac cannot be the reason for NAG release in the urine. A recent study shows that NAG excreted in urine is a marker of deteriorated tubular function and a marker of increased lysosomal activity in the tubular cells, and not necessarily an indicator of cell death (16). This small increase in U-NAG/crea might be considered a sign of disturbed functional integrity of the tubular cells. The stress attributable to the anesthesia and surgery may explain the increased U-NAG/crea. This speculation warrants further studies.
In our patients PuO2 remained at the preoperative level during the surgery and PACU stay, indicating adequate renal medullary homeostasis in both groups. Hypoxia and hemorrhage stimulate EPO synthesis in humans. In an animal study, ketorolac had no effect on EPO production and release in response to reduced hematocrit (17). An increase in EPO levels paralleled the slight reduction of hemoglobin concentration in our study and the administration of ketorolac had no effect on EPO production. This also indicates that there was no tubulointerstitial renal damage.
Some investigations have shown increases in urinary ß2-M after anesthesia (18,19). In our study changes were seen neither in serum nor urine ß2-M, indicating intact tubular reabsorption and glomerular filtration.
Serum osmolality decreased minimally 12 hours postoperatively but returned to the preoperative level irrespective of urine osmolality, which remained low for the first two days. The hypoosmolar diuresis was the logic consequence of our active hydration policy. Serum osmolality remained stable because of the homeostatic control of serum osmolality by the central nervous system and kidneys.
We did not note any differences in PuO2, serum or urine ß2-M, U-NAG/crea or EPO between the groups. These variables are very sensitive to react to any adverse renal changes. Their use in clinical practice and impact on outcome are under debate. A recent report of renal effects of sevoflurane (20) showed that 3463 patients who underwent sevoflurane anesthesia had no changes in serum creatinine or blood urea nitrogen. This was also the case in our study. From a practical point of view, creatinine and urea can be considered appropriate markers of renal function and clinical outcome when assessing the renal effect of modern inhaled anesthetics.
Intraoperative blood loss was larger in the ketorolac group, which is in agreement with an earlier study of different kinds of surgery (21). However, bleeding after mastectomy in patients given ketorolac IV intraoperatively has not been reported to be more than in a placebo group (4). The lack of an effect of ketorolac on blood loss in the study by Bosek and Cox (4) may be a result of the fact that ketorolac was administered near the end of the surgery. The bolus dose of ketorolac given to the patients was the same as our study.
Day-case surgery has become very popular. The patients are older and may have deteriorated renal function influencing the outcome. With a safe combination of a fast-acting anesthetic and an effective nonopioid analgesic, the number of patients needing hospitalization after day surgery may be reduced. In light of our data, the combination of sevoflurane and ketorolac seems to be safe also in day-case surgery.
In conclusion, in otherwise healthy patients undergoing breast surgery under sevoflurane anesthesia, we noted only a slight increase in U-NAG/crea before the peak serum F- concentrations. The administration of ketorolac 90 mg IM perioperatively within approximately 10 hours did not influence serum creatinine and urea values, nor any of the sensitive renal cellular function markers. In well hydrated patients the combination of ketorolac and moderate doses of sevoflurane (34 MAC hours) appears to be safe to the kidneys.
| Acknowledgments |
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This article has been cited by other articles:
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M. Laisalmi, A.-M. Teppo, A.-M. Koivusalo, E. Honkanen, P. Valta, and L. Lindgren The Effect of Ketorolac and Sevoflurane Anesthesia on Renal Glomerular and Tubular Function Anesth. Analg., November 1, 2001; 93(5): 1210 - 1213. [Abstract] [Full Text] [PDF] |
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