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Serum bupivacaine concentrations after intraarticular injection for pain relief after knee arthroscopy
Arthroscopy: The Journal of Arthroscopic and Related Surgery 8(1):44-47 Published by Raven Press, Ltd. 0 1992 Arthroscopy Association of North America
Serum Bupivacaine Concentrations After Intraarticular Injection for Pain Relief After Knee Arthroscopy D. R. Solanki, F.F.A.R.C.S., F. K. Enneking, M.D., F. M. Ivey, M.D., M. Scarborough, M.D., and R. V. Johnston, M.D.
Summary: Intraarticular injection of local anesthetic drugs after arthroscopic knee surgery is used to provide postoperative analgesia. Toxic serum levels of bupivacaine have been reported after its use both in regional anesthesia and for intraarticular injection. The toxicity of the former is related to needle misplacement and the latter is presumed to be absorptive. This study evaluates the effect of tourniquet inflation and the addition of epinephrine on serum concentrations of bupivacaine after intraarticular injection. The result shows that the peak serum bupivacaine concentrations can be reduced by adding epinephrine and injecting it after tourniquet inflation. Key Words: BupivacaineTourniquet-Local anesthetic drugs.
whether the addition of epinephrine to bupivacaine and inflation of the tourniquet before the injection, or a combination of both, had affected the serum levels of bupivacaine after an intraarticular injection.
Bupivacaine is a popular local anesthetic drug in arthroscopic surgery that provides postoperative pain relief by intraarticular injection. It is a highly lipid-soluble local anesthetic drug that rapidly binds to the neural tissue. This property provides quick and long-lasting neural blockade. Several investigators have reported the serum levels of bupivacaine when used with a system of continuous pressure irrigation, or as a bolus injection in the knee joint
MATERIALS AND METHODS The study was approved by the institutional Review Board. Forty American Society of Anesthesiologists (ASA) class I or class II patients between the ages of 18-60 years scheduled to undergo elective knee arthroscopic procedures were recruited from the orthopedic surgery schedule. Informed consent was obtained. No premeditation was given. All patients had general anesthesia. An intravenous infusion was started and the vital signs were monitored. Anesthesia was induced with the intravenous injection of a sleep dose of sodium thiopental. The trachea was intubated after muscle relaxation with succinylcholine. Anesthesia was maintained with 50% oxygen, 50% nitrous oxide, and isoflurane. Isoflurane was selected as the agent of choice because it provides rapid induction and rapid emergence from anesthesia. It also has no effect on the postoperative pain because it lacks significant analgesic activity. No narcotic drugs were administered either preoperatively or intraoperatively.
(1,2). The serum levels of 2 l&ml are considered toxic (3). Wasudev et al. (4) reported serum bupivacaine levels of 0.2-3.4 t&ml after a bolus injection of 30 ml of 0.75% bupivacaine into the knee joint. These levels were measured 20-60 min after the release of the tourniquet. Toxicity of bupivacaine is of concern because the majority of these procedures are performed in outpatient surgery, and the patients are expeditiously discharged home. The purpose of our study was to determine
From the Department of Anesthesiology (D.R.S., R.V.J.) and Orthopedic Surgery (F.M.I.), University of Texas Medical Branch at Galveston, Galveston, Texas, and the Department of Anesthesiology (F.K.E.), Brigham and Women’s Hospital, and Department of Orthopedics (M.S.), Massachusetts General Hospital, Boston, Massachusetts, U.S.A. Address correspondence and reprint requests to Dr. D. R. Solanki, at Department of Anesthesiology, University of Texas Medical Branch, Galveston, TX 77550, U.S.A.
44
SERUM BUPIVACAINE
LEVELS
The ipsilateral femoral vein was cannulated with a 4 F Cook catheter using the Seldinger technique after examination of the affected knee. Normal saline was infused at 30 ml/h to maintain its patency. Twenty milliliters ml of 0.25% bupivacaine was injected into the knee joint with a 20-g spinal needle at the end of the arthroscopic procedure. Bupivacaine was injected with or without epinephrine, either in the presence or absence of tourniquet inflation, depending on to which group the patient was assigned. The subjects were assigned randomly to one of the four groups. There were 10 subjects in each group. The study was double blinded and the code was maintained by the nonparticipating pharmacist. The four groups were as follows: group I: bupivacaine without tourniquet inflation (C); group II: bupivacaine after tourniquet inflation (T); group III: bupivacaine with 1:200,000 epinephrine without tourniquet inflation (E); group IV: bupivacaine with 1:200,000 epinephrine after tourniquet inflation (E + T). Unheparinized blood samples in lo-ml aliquots were collected from the femoral vein at 5, 10, 20, 30, and 60 min after the intraarticular injection. Patients in groups II and IV had the tourniquet released after the lo-min sample was collected. The samples were centrifuged and the serum was separated and analyzed. Serum bupivacaine levels were determined by gas chromatography using a technique modified by Park et al. (5). The samples were extracted in ether, reconstituted in hexane, and measured on a Hewlett Packard (Palo Alto, CA, U.S.A.) 579OA gas chromatograph. This is equipped with a nitrogen phosphorus detector and a 6-ft packed column coated with OV 1, a nonpolar dimethylpolysiloxane phase. Lidocaine and bupivacaine were used as the internal and external standards, respectively. Calibration curves were generated using serum with known quantities of bupivacaine. These curves demonstrated a practical level of reliable detection of 10 ng/ml, and a SE for any measurement was +5%. The technique studied consisted of two factors: epinephrine and tourniquet inflation. Each factor was examined in the presence or absence of the other, along with bupivacaine. This resulted in four therapeutic combinations. The contribution of each factor was defined as the difference between the absence or the presence of the other factor. The data were analyzed as a three-factor factorial experiment with repeated measures of time. Effects of
AFTER KNEE ARTHROSCOPY
45
the interactions were assessed at 0.05 levels of significance. All patients were observed in the operating room and in the recovery room for signs of neurotoxicity. Heart rate, blood pressure, electrocardiograms, and oxygen saturations were monitored. The patients were discharged to the ward on recovery from general anesthesia. RESULTS The four groups were comparable in age, sex, height, and weight. The operative procedures for which the arthroscopy was performed are listed in Table 1. The peak serum bupivacaine levels in all groups occurred within 10 min after the intraarticular injection. The levels ranged from 0.05 to 0.55 pg/ml (Fig. 1) None of the patients had levels approaching 2 kg/ml, which is considered toxic. The serum levels stabilized at 10 min and did not change up to 60 min regardless of the treatment combinations. This characteristic of bupivacaine serum levels is consistent with that after intravenous regional anesthesia, and is due to tissue binding (6). No neurotoxicity or cardiac toxicity was noted. Because the bupivacaine level was in a transitional stage at 5 min, these data were excluded from the final analysis. Consequently, each patient had four observations across time (10, 20, 30, and 60 min), resulting in 40 data points for each group. The serum level of each group was in a stationary stage from 10 to 60 min. There was no significant time-to-time difference, so the mean serum level across time was computed for all groups, as presented in Table 2. In addition, no significant interaction existed between epinephrine and tourniquet. This lack of interaction indicated that the effects of epinephrine and tourniquet were additive (i.e., independent of each other). Therefore, the effect of epinephrine was the same regardless of the presence or absence of the tourniquet. The presence of epinephrine lowered the serum bupivacaine levels by 0.16 pg/ml (p = 0.03) whether the tourniquet was inflated or not. Similarly, inflation of the tourTABLE 1. Operative procedures Synovial procedures Lateral release Menisectomy Chondroplasty Debridement Diagnostic scope Removal of foreign body
6 7 12 9 3 2 1
Arthroscopy.
Vd. 8, No. I. 1992
D. R. SOLANKI ET AL.
46 pgm/ml 1.0 4
l
C: Control 0 E: Epinephrine 0 T: Tourniquet 0 T + E: Tourniquet & Epinephrine
FIG. 1. Serum
levels
of bupiv-
acaine.
0.2
-
0 (E)
---------~-----~(~) o--_-_-_-(-J
~~-_-_-_-_-_-_-_-_-_-_-_-_-_-__O(T+~)
0.0-, 0
10
20
30
40
50
60
Time
niquet lowered the serum bupivacaine level by 0.23 l&ml (p = 0.002), regardless of the presence or absence of epinephrine. DISCUSSION Bupivacaine, an amide local anesthetic drug, is a popular choice for intraarticular anesthesia, postoperative pain relief, and arthroscopic surgery because of its long half-life. Absorption rates for all amide local anesthetic drugs vary according to their site of injection. The highest serum levels occur after the intercostal injections, followed by caudal, extradural, brachial plexus, and the sciatic femoral nerve blocks (7). Bupivacaine, despite its advantages, is potentially a neurotoxic and cardiotoxic agent with a toxic threshhold much lower than that of lidocaine. Toxic reactions after bupivacaine are manifested by ringing in the ear, perioral numbness, slurred speech, lightheadedness, convulsions, hypotension, bradycardia, ventricular arrhythmias, and cardiac arrest. Review of the literature provides TABLE 2. Mean serum levels of bupivacaine
(pglmi)
across time (IO, 20, 30, and 60 min) Epinephrine
Absent
Present
Mean
Difference in means
Absent” FVesen+
(40) 0.43 (40) 0.18
(40) 0.24 (40) 0.04
(SO) 0.34 (80) 0.11
0.23
Mean
(80) 0.30
(80) 0.14
Difference in means
0.16
Number of observations are in parentheses.
a Tourniquet absent. b Tourniquet present.
Arthroscopy,
Vol. 8, No. 1, 1992
proof for such episodes when epidural and regional nerve blocks were done with bupivacaine (8). There are no reports of toxic reactions after intraarticular injections of bupivacaine. However, the possibilities of such events are of concern. The highest mean serum level reported by Gerber et al. (9) was 0.15 * 0.03 t&ml after the injection of 20 ml of 0.25% bupivacaine into the knee joint. This peak occurred at 30 min and did not change over time up to 60 min. Our results are in agreement. Yoshiya et al. (10) reported a maximum level of 1.36 kg/ml after injecting a mixture of lidocaine and bupivacaine into the knee joint followed by saline irrigation. A single case report has described generalized seizures and unconsciousness in an otherwise healthy female patient at a serum bupivacaine concentration of 1.1 kg/ml. This occurred after 2 hr of intravenous infusion of bupivacaine at 2 mg/min (11). The serum levels of bupivacaine in our study are lower than those reported in other studies, and did not result in clinical signs of toxicity in any subjects. These lowerperum bupivacaine levels may be related to several factors. The total dose of bupivacaine was limited to 50 mg (20 ml of 0.25%), unlike the study by Wasudev (4) in which 225 mg (30 ml of 0.75%) was used. Addition of epinephrine decreased the serum levels by 0.16 t&ml. Katz et al. (12) state that the peak serum levels can be decreased by minimizing the total tourniquet inflation time and maximizing the time from bupivacaine injection to tourniquet release. A relationship exists between reperfusion hyperemia after prolonged
SERUM BUPIVACAINE
LEVELS
tourniquet &hernia. Hence, sudden release of the tourniquet after bupivacaine injection may cause a surge in serum levels because of the hyperemia. Most of our arthroscopies were done without tourniquet inflation. The mean tourniquet time was 37 min where it was used. Injection to tourniquet de-
flation time was 10 min. Tourniquet inflation decreased the serum bupivacaine levels by 0.23 pg/ml, as indicated by the results. In conclusion, this study demonstrates that intraarticular injection of 20 ml of 0.25% bupivacaine is safe. Peak serum concentrations occur within 10 min and are stable thereafter. The addition of epinephrine and injecting it after the tourniquet inflation decreased the peak serum bupivacaine concentration to 0.09 kg/ml. This is far below the toxic threshhold of 2 pg/ml and did not change over time. This technique allows the injection of bupivacaine into both knees, if needed, still without approaching the toxic levels. Acknowledgment: We thank Noel W. Lawson, M.D., Professor, Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas, for the review and advice in preparation of this article, and Barbara Sanders for her patience and secretarial help. We also thank Diagnostic Systems Laboratories, Inc., Webster, Texas, for providing the specimen tubes for collection of blood samples.
AFTER KNEE ARTHROSCOPY REFERENCES 1. Debruyne D, Moulin M, Cames C, Beguin J-A, Lockes B.
Monitoring serum bupivacaine Eur J Clin Pharmacol
levels during arthroscopy.
1985;27:733-5.
2. Meinig RP, Hottgrewe, Wiedel JD, Cristie D, Kestin KJ. Plasma bupivacaine levels following single dose intraarticular instillation for arthroscopy. Am J Sports Med 1988;16:295-300. 3. Scott DB. Evaluation of toxicity of local anesthetic agents in man. Br J Anaesth 1975;47:5660. 4. Wasudev G, Smith BE, Limbird TJ. Blood levels of bupivacaine after knee arthroscopy of the knee joint. Arthroscopy 1990;6:4&2.
5. Park GB, Erdtmansky PE, Brown RR, Kullberg MP, Edelson J. Analysis of mepivacaine, bupivacaine, etidocaine, lidocaine and tetracaine. J Pharmacie 1980;69:603-5. 6. Evans CJ, Dewar JA, Boyes RN. Residual nerve block following intravenous regional anesthesia. Br J Anaesth 1974;46:668.
7. Tucker GT, Moore DC, Bridenbaugh PO, Bridenbaugh LD, Thompson GE. Systemic absorption of mepivacaine in commonly used regional block procedures. Anesthesiology 1972;37:277.
8. Albright G. Cardiac arrest following regional anesthesia with etidocaine or bupivacaine. Anesrhesiology 1979;51:285-7. 9. Gerber H, Censier K, Gtichter A, Arsuffl A, Romppainen J. Intra-articular absorption of bupivacaine during arthroscopy. Anesthesiology 1985;63:A217. 10. Yoshiya S, Kurakasa M, Hirohata K, Andrish J. Knee arthroscopy using local anesthetic. Arthroscopy 1988;4:86-7. 11. Hasselstrom L, Mogensen T. Toxic reaction of bupivacaine at low plasma concentration. Anesthesiology 1984;61:99100.
12. Katz JA, Keading CS, Hill JR, Henthorn TK. The pharmacokinetics of bupivacaine when injected intra-articularly after knee arthroscopy. Anesth Analg 1988;67:871-5.
Arthroscopy. Vol. 8, No. 1, 1992
Serum Bupivacaine Concentrations After Intraarticular Injection for Pain Relief After Knee Arthroscopy D. R. Solanki, F.F.A.R.C.S., F. K. Enneking, M.D., F. M. Ivey, M.D., M. Scarborough, M.D., and R. V. Johnston, M.D.
Summary: Intraarticular injection of local anesthetic drugs after arthroscopic knee surgery is used to provide postoperative analgesia. Toxic serum levels of bupivacaine have been reported after its use both in regional anesthesia and for intraarticular injection. The toxicity of the former is related to needle misplacement and the latter is presumed to be absorptive. This study evaluates the effect of tourniquet inflation and the addition of epinephrine on serum concentrations of bupivacaine after intraarticular injection. The result shows that the peak serum bupivacaine concentrations can be reduced by adding epinephrine and injecting it after tourniquet inflation. Key Words: BupivacaineTourniquet-Local anesthetic drugs.
whether the addition of epinephrine to bupivacaine and inflation of the tourniquet before the injection, or a combination of both, had affected the serum levels of bupivacaine after an intraarticular injection.
Bupivacaine is a popular local anesthetic drug in arthroscopic surgery that provides postoperative pain relief by intraarticular injection. It is a highly lipid-soluble local anesthetic drug that rapidly binds to the neural tissue. This property provides quick and long-lasting neural blockade. Several investigators have reported the serum levels of bupivacaine when used with a system of continuous pressure irrigation, or as a bolus injection in the knee joint
MATERIALS AND METHODS The study was approved by the institutional Review Board. Forty American Society of Anesthesiologists (ASA) class I or class II patients between the ages of 18-60 years scheduled to undergo elective knee arthroscopic procedures were recruited from the orthopedic surgery schedule. Informed consent was obtained. No premeditation was given. All patients had general anesthesia. An intravenous infusion was started and the vital signs were monitored. Anesthesia was induced with the intravenous injection of a sleep dose of sodium thiopental. The trachea was intubated after muscle relaxation with succinylcholine. Anesthesia was maintained with 50% oxygen, 50% nitrous oxide, and isoflurane. Isoflurane was selected as the agent of choice because it provides rapid induction and rapid emergence from anesthesia. It also has no effect on the postoperative pain because it lacks significant analgesic activity. No narcotic drugs were administered either preoperatively or intraoperatively.
(1,2). The serum levels of 2 l&ml are considered toxic (3). Wasudev et al. (4) reported serum bupivacaine levels of 0.2-3.4 t&ml after a bolus injection of 30 ml of 0.75% bupivacaine into the knee joint. These levels were measured 20-60 min after the release of the tourniquet. Toxicity of bupivacaine is of concern because the majority of these procedures are performed in outpatient surgery, and the patients are expeditiously discharged home. The purpose of our study was to determine
From the Department of Anesthesiology (D.R.S., R.V.J.) and Orthopedic Surgery (F.M.I.), University of Texas Medical Branch at Galveston, Galveston, Texas, and the Department of Anesthesiology (F.K.E.), Brigham and Women’s Hospital, and Department of Orthopedics (M.S.), Massachusetts General Hospital, Boston, Massachusetts, U.S.A. Address correspondence and reprint requests to Dr. D. R. Solanki, at Department of Anesthesiology, University of Texas Medical Branch, Galveston, TX 77550, U.S.A.
44
SERUM BUPIVACAINE
LEVELS
The ipsilateral femoral vein was cannulated with a 4 F Cook catheter using the Seldinger technique after examination of the affected knee. Normal saline was infused at 30 ml/h to maintain its patency. Twenty milliliters ml of 0.25% bupivacaine was injected into the knee joint with a 20-g spinal needle at the end of the arthroscopic procedure. Bupivacaine was injected with or without epinephrine, either in the presence or absence of tourniquet inflation, depending on to which group the patient was assigned. The subjects were assigned randomly to one of the four groups. There were 10 subjects in each group. The study was double blinded and the code was maintained by the nonparticipating pharmacist. The four groups were as follows: group I: bupivacaine without tourniquet inflation (C); group II: bupivacaine after tourniquet inflation (T); group III: bupivacaine with 1:200,000 epinephrine without tourniquet inflation (E); group IV: bupivacaine with 1:200,000 epinephrine after tourniquet inflation (E + T). Unheparinized blood samples in lo-ml aliquots were collected from the femoral vein at 5, 10, 20, 30, and 60 min after the intraarticular injection. Patients in groups II and IV had the tourniquet released after the lo-min sample was collected. The samples were centrifuged and the serum was separated and analyzed. Serum bupivacaine levels were determined by gas chromatography using a technique modified by Park et al. (5). The samples were extracted in ether, reconstituted in hexane, and measured on a Hewlett Packard (Palo Alto, CA, U.S.A.) 579OA gas chromatograph. This is equipped with a nitrogen phosphorus detector and a 6-ft packed column coated with OV 1, a nonpolar dimethylpolysiloxane phase. Lidocaine and bupivacaine were used as the internal and external standards, respectively. Calibration curves were generated using serum with known quantities of bupivacaine. These curves demonstrated a practical level of reliable detection of 10 ng/ml, and a SE for any measurement was +5%. The technique studied consisted of two factors: epinephrine and tourniquet inflation. Each factor was examined in the presence or absence of the other, along with bupivacaine. This resulted in four therapeutic combinations. The contribution of each factor was defined as the difference between the absence or the presence of the other factor. The data were analyzed as a three-factor factorial experiment with repeated measures of time. Effects of
AFTER KNEE ARTHROSCOPY
45
the interactions were assessed at 0.05 levels of significance. All patients were observed in the operating room and in the recovery room for signs of neurotoxicity. Heart rate, blood pressure, electrocardiograms, and oxygen saturations were monitored. The patients were discharged to the ward on recovery from general anesthesia. RESULTS The four groups were comparable in age, sex, height, and weight. The operative procedures for which the arthroscopy was performed are listed in Table 1. The peak serum bupivacaine levels in all groups occurred within 10 min after the intraarticular injection. The levels ranged from 0.05 to 0.55 pg/ml (Fig. 1) None of the patients had levels approaching 2 kg/ml, which is considered toxic. The serum levels stabilized at 10 min and did not change up to 60 min regardless of the treatment combinations. This characteristic of bupivacaine serum levels is consistent with that after intravenous regional anesthesia, and is due to tissue binding (6). No neurotoxicity or cardiac toxicity was noted. Because the bupivacaine level was in a transitional stage at 5 min, these data were excluded from the final analysis. Consequently, each patient had four observations across time (10, 20, 30, and 60 min), resulting in 40 data points for each group. The serum level of each group was in a stationary stage from 10 to 60 min. There was no significant time-to-time difference, so the mean serum level across time was computed for all groups, as presented in Table 2. In addition, no significant interaction existed between epinephrine and tourniquet. This lack of interaction indicated that the effects of epinephrine and tourniquet were additive (i.e., independent of each other). Therefore, the effect of epinephrine was the same regardless of the presence or absence of the tourniquet. The presence of epinephrine lowered the serum bupivacaine levels by 0.16 pg/ml (p = 0.03) whether the tourniquet was inflated or not. Similarly, inflation of the tourTABLE 1. Operative procedures Synovial procedures Lateral release Menisectomy Chondroplasty Debridement Diagnostic scope Removal of foreign body
6 7 12 9 3 2 1
Arthroscopy.
Vd. 8, No. I. 1992
D. R. SOLANKI ET AL.
46 pgm/ml 1.0 4
l
C: Control 0 E: Epinephrine 0 T: Tourniquet 0 T + E: Tourniquet & Epinephrine
FIG. 1. Serum
levels
of bupiv-
acaine.
0.2
-
0 (E)
---------~-----~(~) o--_-_-_-(-J
~~-_-_-_-_-_-_-_-_-_-_-_-_-_-__O(T+~)
0.0-, 0
10
20
30
40
50
60
Time
niquet lowered the serum bupivacaine level by 0.23 l&ml (p = 0.002), regardless of the presence or absence of epinephrine. DISCUSSION Bupivacaine, an amide local anesthetic drug, is a popular choice for intraarticular anesthesia, postoperative pain relief, and arthroscopic surgery because of its long half-life. Absorption rates for all amide local anesthetic drugs vary according to their site of injection. The highest serum levels occur after the intercostal injections, followed by caudal, extradural, brachial plexus, and the sciatic femoral nerve blocks (7). Bupivacaine, despite its advantages, is potentially a neurotoxic and cardiotoxic agent with a toxic threshhold much lower than that of lidocaine. Toxic reactions after bupivacaine are manifested by ringing in the ear, perioral numbness, slurred speech, lightheadedness, convulsions, hypotension, bradycardia, ventricular arrhythmias, and cardiac arrest. Review of the literature provides TABLE 2. Mean serum levels of bupivacaine
(pglmi)
across time (IO, 20, 30, and 60 min) Epinephrine
Absent
Present
Mean
Difference in means
Absent” FVesen+
(40) 0.43 (40) 0.18
(40) 0.24 (40) 0.04
(SO) 0.34 (80) 0.11
0.23
Mean
(80) 0.30
(80) 0.14
Difference in means
0.16
Number of observations are in parentheses.
a Tourniquet absent. b Tourniquet present.
Arthroscopy,
Vol. 8, No. 1, 1992
proof for such episodes when epidural and regional nerve blocks were done with bupivacaine (8). There are no reports of toxic reactions after intraarticular injections of bupivacaine. However, the possibilities of such events are of concern. The highest mean serum level reported by Gerber et al. (9) was 0.15 * 0.03 t&ml after the injection of 20 ml of 0.25% bupivacaine into the knee joint. This peak occurred at 30 min and did not change over time up to 60 min. Our results are in agreement. Yoshiya et al. (10) reported a maximum level of 1.36 kg/ml after injecting a mixture of lidocaine and bupivacaine into the knee joint followed by saline irrigation. A single case report has described generalized seizures and unconsciousness in an otherwise healthy female patient at a serum bupivacaine concentration of 1.1 kg/ml. This occurred after 2 hr of intravenous infusion of bupivacaine at 2 mg/min (11). The serum levels of bupivacaine in our study are lower than those reported in other studies, and did not result in clinical signs of toxicity in any subjects. These lowerperum bupivacaine levels may be related to several factors. The total dose of bupivacaine was limited to 50 mg (20 ml of 0.25%), unlike the study by Wasudev (4) in which 225 mg (30 ml of 0.75%) was used. Addition of epinephrine decreased the serum levels by 0.16 t&ml. Katz et al. (12) state that the peak serum levels can be decreased by minimizing the total tourniquet inflation time and maximizing the time from bupivacaine injection to tourniquet release. A relationship exists between reperfusion hyperemia after prolonged
SERUM BUPIVACAINE
LEVELS
tourniquet &hernia. Hence, sudden release of the tourniquet after bupivacaine injection may cause a surge in serum levels because of the hyperemia. Most of our arthroscopies were done without tourniquet inflation. The mean tourniquet time was 37 min where it was used. Injection to tourniquet de-
flation time was 10 min. Tourniquet inflation decreased the serum bupivacaine levels by 0.23 pg/ml, as indicated by the results. In conclusion, this study demonstrates that intraarticular injection of 20 ml of 0.25% bupivacaine is safe. Peak serum concentrations occur within 10 min and are stable thereafter. The addition of epinephrine and injecting it after the tourniquet inflation decreased the peak serum bupivacaine concentration to 0.09 kg/ml. This is far below the toxic threshhold of 2 pg/ml and did not change over time. This technique allows the injection of bupivacaine into both knees, if needed, still without approaching the toxic levels. Acknowledgment: We thank Noel W. Lawson, M.D., Professor, Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas, for the review and advice in preparation of this article, and Barbara Sanders for her patience and secretarial help. We also thank Diagnostic Systems Laboratories, Inc., Webster, Texas, for providing the specimen tubes for collection of blood samples.
AFTER KNEE ARTHROSCOPY REFERENCES 1. Debruyne D, Moulin M, Cames C, Beguin J-A, Lockes B.
Monitoring serum bupivacaine Eur J Clin Pharmacol
levels during arthroscopy.
1985;27:733-5.
2. Meinig RP, Hottgrewe, Wiedel JD, Cristie D, Kestin KJ. Plasma bupivacaine levels following single dose intraarticular instillation for arthroscopy. Am J Sports Med 1988;16:295-300. 3. Scott DB. Evaluation of toxicity of local anesthetic agents in man. Br J Anaesth 1975;47:5660. 4. Wasudev G, Smith BE, Limbird TJ. Blood levels of bupivacaine after knee arthroscopy of the knee joint. Arthroscopy 1990;6:4&2.
5. Park GB, Erdtmansky PE, Brown RR, Kullberg MP, Edelson J. Analysis of mepivacaine, bupivacaine, etidocaine, lidocaine and tetracaine. J Pharmacie 1980;69:603-5. 6. Evans CJ, Dewar JA, Boyes RN. Residual nerve block following intravenous regional anesthesia. Br J Anaesth 1974;46:668.
7. Tucker GT, Moore DC, Bridenbaugh PO, Bridenbaugh LD, Thompson GE. Systemic absorption of mepivacaine in commonly used regional block procedures. Anesthesiology 1972;37:277.
8. Albright G. Cardiac arrest following regional anesthesia with etidocaine or bupivacaine. Anesrhesiology 1979;51:285-7. 9. Gerber H, Censier K, Gtichter A, Arsuffl A, Romppainen J. Intra-articular absorption of bupivacaine during arthroscopy. Anesthesiology 1985;63:A217. 10. Yoshiya S, Kurakasa M, Hirohata K, Andrish J. Knee arthroscopy using local anesthetic. Arthroscopy 1988;4:86-7. 11. Hasselstrom L, Mogensen T. Toxic reaction of bupivacaine at low plasma concentration. Anesthesiology 1984;61:99100.
12. Katz JA, Keading CS, Hill JR, Henthorn TK. The pharmacokinetics of bupivacaine when injected intra-articularly after knee arthroscopy. Anesth Analg 1988;67:871-5.
Arthroscopy. Vol. 8, No. 1, 1992