Continuous Alfentanil Infusion for Extracorporeal Shock Wave Lithotripsy of Gallbladder Stones Neil Roy Connelly,
MD
and Alan D. Weinstock,
CONNELLY NR, WEINSTOCK AD. Continuous alfentanil infusion for extracorporeal shock wave lithotripsy of gallbladder stones. Anesth Analg 1990;70:299-302.
Extracorporeal shock zipave lithotripsy has recently been introduced in clinical trials for the treatment of cholelithiasis. General anesthesia, epidural anesthesia, and intravenous opiates haoe been used in the anesthetic management of patients undergoing this procedure. This report details our anesthetic management, which was used in 23 patients who underwent 27 procedures, and presents three illustrative cases. A continuous infusion of alfentanil and a 0.625-2.5-mg dose of droperidol were administered to the patients who were easily arousable during the procedure,
Extracorporeal shock wave lithotripsy (ECSWL) is used in the treatment of renal calculi, and has recently been introduced in the United States, through clinical trials, for the treatment of radiolucent cholelithiasis (1,2), with the possible benefits of avoiding surgery and postoperative morbidity. Patients are placed in contact with an electrode-containing water cushion that produces a shock wave. The wave is transmitted through body tissues and when it reaches the stone, shearing forces are produced, and the stone is disintegrated. The shocks are triggered by the electrocardiogram. Many different methods of anesthesia, including general anesthesia, epidural anesthesia, spinal anesthesia, intercostal blocks (3), and, most recently, interpleural anesthesia (4), have been described for renal ECSWL. General anesthesia, epidural anesthesia, and intravenous opiates have been used in the anesthetic management of patients undergoing biliary lithotripsy (2), a procedure that can be quite uncomfortable (5). At our institution, biliary lithotripReceived from the Department of Anesthesiology, Yale University School of Medicine, Yale-New Haven Hospital, New Haven, Connecticut. Accepted for publication November 1, 1989. Address correspondence to Dr. Connelly, Department of Anesthesiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510. 91990 by the International Anesthesia Research Society
MD
and were able to cooperate with positioning change requests. Our patients did not develop apnea, hernodynamically significant bradycardia, or chest wall rigidity. One patient became nauseated, and one patient experienced a hypotensive episode that was unheralded by a change in respiratory rate, heart rate, or oxygen saturation. The patients were comfortable throughout the procedure, alert upon arrival to the postanesthesia care unit, and satisfied with this technique. A continuous infusion of alfentanil can be successfully used for the management of patients undergoing biliary lithotripsy.
Key Words: ANESTHETICS, INTRAVENOUS. ANESTHESIA, BILIARY TRACT LITHOTRIPSY.
sy is under investigation for the treatment of cholelithiasis. To facilitate successful gallstone localization by ultrasound, methods of anesthesia must limit patient movement, as well as maintain patient comfort. Alfentanil, a narcotic with a rapid onset and short duration of action (6,7), offers some advantages over other possible methods of anesthesia for the management of patients undergoing biliary lithotripsy. We present here the data from 23 patients treated with this technique who underwent 27 ECSWL procedures, and detail three illustrative cases.
Case Reports Case 2 A 45-yr-old man presented for biliary lithotripsy. The patient had no significant past medical history aside from symptomatic cholelithiasis. The physical and laboratory examinations were normal. The patient received no premedication, was brought to the lithotripsy van (a trailer connected to the hospital that is equipped with an anesthesia machine and capabilities for full invasive monitoring), and placed in the prone position. Intravenous access was established and oxygen via nasal cannula was administered. Monitors included electrocardiography, noninvasive
CONNELLY A N D WEINSTOCK
blood pressure, and pulse oximetry. Droperidol (0.625 mg) and alfentanil (5 pg/kg) were administered. An alfentanil infusion was begun at 1 p g k g - ' . min-'. The patient required an additional two boluses of 5 pglkg, at 15 and 45 min, and was very comfortable throughout the 3.5-h procedure. The infusion was discontinued 10 min before the end of the procedure. Upon moving from the lithotripsy machine to the stretcher, the patient experienced nausea which was successfully treated with an additional 1.25 mg of droperidol. The patient was alert and comfortable upon arrival in the postanesthesia care unit.
Case 2 A 45-yr-old man, with no significant past medical history, was brought to the lithotripsy van for ECSWL. Monitoring, as in case 1, was applied and intravenous access was securcd. Droperidol (1.25 mg) was given, alfentanil (5 pgikg) was given as a bolus, and an alfentanil infusion was begun at 0.5 pg.kg-'. min-I. Because of dif?iculty in localizing the galIstones by ultrasound, the procedure took 4.5 h. The patient required two additional boluses of 5 pg/kg at 1 and 2 h into the procedure because of generalized discomfort. He also received a total of 3 mg of midazolam at the beginning of the procedure, in I-mg increments, because of agitation. The infusion was stopped 15 min before the end of the procedure, and the patient stated that he was comfortable throughout the entire procedure.
Case 3 A 46-yr-old man presented with a 1-yr history of right upper quadrant colic. He had a history of hypercholesterolemia and hypertension, for which he was taking 50 mg of metoprolol twice a day (baseline treated blood pressure was 110/80 mm Hg). The patient was positioned, an intravenous cannula was placed, and monitors were applied. The end-tidal C 0 2monitor was connected, via a plastic connection, to the nasal cannula. The patient was given 2.5 mg of droperidol and 5 pg/kg of alfentanil, and then begun on an alfentanil infusion of 0.5 pg-kg-'.min-'. Because of discomfort, thc patient required two additional boluses: one of 5 pglkg with the infusion increased to 1 pg.kg-'.min-' at 45 min into the procedure; and a second bolus 30 min later of 2.5 pgikg with the infusion remaining at 1 pg.kg-'. min-'. Forty-five minutcas after the second bolus, the
patient's blood pressure was noted to be 65/45 mm Hg, and the patient was minimally arousable. Immediately before this, the patient's oxygen saturation ~ 54 mm Hg, and the respiwas 97%, the P E T C Owas ratory rate was 11 breathdmin. The patient was placed in the Trendelenberg position, the alfentanil infusion was discontinued, and 400 pg of intravenous naloxone was given, while 100% 0, was administered via a facemask. The oxygen saturation remained above 94%, while 400 mL of lactated Ringer's solution was administered intravenously over a 10min period. The blood pressure returned to normal, the patient regained full consciousness, and the few remaining shocks were administered without restarting the alfentanil infusion. Shortly after arrival in the postanesthesia care unit, the patient's systolic blood pressure was 65 mm Hg. The patient was comfortable and responsive to commands, was breathing at a rate of 12 breathdmin, and was maintaining an oxygen saturation of 100%. One liter of lactated Ringer's solution was administered intravenously for 0.5 h, with a subsequent rise in the blood pressure. A 12-lead electrocardiogram was obtained, and was unchanged from the pre-ECSWL electrocardiogram. The patient did well after this episode, and was discharged from the hospital on the day after the ECSWL.
Discussion Biliary lithotripsy is performed with the use of three different types of devices (1). At our institution, the Dornier multipurpose lithotripter (MPL 9000), located some distance from the main operating room, is utilized. A maximum number of 1500 electrocardiogram-triggered shocks is given per treatment, with each session lasting from 1.25 to 4.5 h. Although a number of anesthetic approaches can be used, each has relative disadvantages. Because the technique mandates the patient being placed in the prone position, most anesthesiologists administer general anesthesia to these patients via a tracheal tube. This has the potential for both the adverse pulmonary effects of mechanical ventilation in the prone position and dislodgement of the tracheal tube when changing patient position. Regional techniques necessitate a high sensory level, with the possible complications of hypotension, local anesthetic toxicity, and too high a level. To limit patient motion, regional techniques would require additional intravenous supplementation. We were able to manage these patients successfully using solely intravenous sedation and analgesia. To maintain this level of comfort, a continuous infu-
ALFENTANIL FOR BlLlARY LITHOTRIPSY
ANtSTH ANALC 1990.70:2YY-30?
Table 1. Dose of Alfentanil Used
0%)
Duration of ECSWL (h)
125 98 80 97 96 70 107 90 125 90 72 61 66 57 65 88 89 89 97 89 100 70 85 50 75 72 57
3.5 4.5 2.25 1.25 4.5 2 1.25 1.75 3.25 1.5 1.5 1.5 1.5 1.5 1.5 1.5 2 1.5 2.5 2.25 2.25 2.5 2.25 1.5 1.5 2 1.5
Weight Patient 1'' 2 3
4 5 6 7 8" 9' 10" 11 12 13
14 15 16
17' 18' 19 20 21 22 23 24 25 26 27
Alfentanil total dose (A%)
11,000 12,250 7,000 2,750 11,000 2,950 7,200 3,700 11.000 5,500 1,500 4,600 6,500 2,075 2,000 2,650 5,500 3,650 2,500 1,450 7,200 2,950 7,500 3,000 2,125 5,000 4,600
( K g kg-' h ')
25 28 38 23 25 21 53 24 27 41 14 50 65 24 21 20 31 27 12 6 32 17 39 40 19 35 53
ECSWL, extracorporeal shockwave lithohipsy. '' " ' Identical superscripts indicate repeat procedures in the same patient.
sion technique seemed ideal. Alfentanil infusions have been previously used in spontaneously breathing patients (8,9), and have been shown to provide hemodynamic stability (10). Because of its quick onset and short duration of action (11,12), we chose to use alfentanil in this setting. After positioning the patient and placement of monitors, droperidol (0.625-2.5 mg) and a loading dose of 5 pg/kg of alfentanil were administered. Simultaneously, an alfentanil infusion of 0.5 pgkg-'. min-' was begun. If the patient became uncomfortable, an additional bolus of 2.5-5 pglkg was given, and the infusion was increased in increments of 0.25-0.5 pg.kg-'.min-'. The alfentanil infusion did not need to be turned higher than 1 pg-kg-'.min-' in any of our patients, and can be discontinued 5 1 5 min before the end of the procedure. The dosages of alfentanil given to the patients in our series are shown in Table 1. A continuous infusion technique offers the benefit of a steady plasma concentration with maintenance of patient comfort and the ability to adjust the plasma level rapidly as the level of stimulation changes (13). An infusion pump (Bard Harvard Mini Infusor, Har-
301
vard Apparatus Co., Inc., South Natick, Mass.) was used to administer the drug, which enables the user to adjust the infusion in increments of 0.25 pg.kg-'. min-' and alerts the user to the total amount of drug administered. Dose-dependent ventilatory depression occurs with alfentanil. Delayed respiratory depression has also been reported with alfentanil infusion techniques (14,15). The respiratory rate was maintained above 10 breathslmin in all of our patients and the oxygen saturation was maintained above 94%. The addition of droperidol to alfentanil has not been studied, although droperidol does not appear to increase the depressant effect upon ventilation when used in combination with fentanyl (16,17). Biliary tract spasm has been associated with the use of narcotics (18). Given the nature of the underlying disease process in these patients, if an episode of biliary colic occurs, the narcotics must be considered as a possible etiologic agent. However, none of the patients in our series experienced biliary spasm related to the alfentanil infusion. As both biliary tract manipulation and alfentanil itself can cause nausea and vomiting, patients were given droperidol (19) (0.625-2.5 mg) at the beginning of the procedure. None of the patients experienced nausea during the procedure. One patient became nauseated upon moving from the lithotripsy machine to the stretcher; this was successfully treated with an additional 1.25-mg dose of droperidol. The vagotonic effects of alfentanil can cause a slowing of the pulse rate. As ECSWL is triggered by the electrocardiogram if the heart rate becomes excessively slow, the duration of the procedure will be prolonged. If this is the case, and if no contraindications exist, the administration of an anticholinergic drug will decrease the time required for the lithotripsy. An occasional patient in our series, approximately 596, received 0.2 mg of glycopyrrolate for this reason. In summary, a continuous infusion of alfentanil can be successfully used for the management of patients undergoing biliary lithotripsy. Patients were easily arousable throughout the procedure, and were able to cooperate with positioning change requests. Our patients did not develop apnea, bradycardia, or chest wall rigidity. One patient became nauseated upon moving to the stretcher. One patient experienced a hypotensive episode unheralded by a change in respiratory rate, heart rate, or oxygen saturation. Possible explanations for this hypotension include intravascular volume depletion secondary to the patient's m n per os status, alfentanil-induced vagal tone, a-blockade from the droperidol administration, increased vagal tone induced by the lithotripsy shock
302
ANESTH ANALG 1990;70:299-302
waves on the peritoneum, or a combination of the above-mentioned factors. The patients were very alert upon arrival to the postanesthesia care unit and stated that they were comfortable during the procedure. The patients were satisfied with the level of analgesia, and were pleased that they were able to avoid general anesthesia. As with all administrations of anesthesia, this method requires a high level of vigilance. We present this report at a time when biliary lithotripsy is in its infancy in this country, and has the potential to become an important noninvasive method of treating gallstones. As this practice becomes more popular, anesthesiologists will be increasingly called upon to participate in the care of these patients. We thank Raymond Sinatra. MD, PhD, and Paul Barash, MD, for their help in the preparation of this report.
CONNELLY AND WEINSTOCK
6. White PF, Coe V, Shafer A, Sung ML. Comparison of alfentanil with fentanyl for outpatient anesthesia. Anesthesiology 1986; 64:99-106. 7. Ausems ME, Hug CC, Stanski DR, Burm AGL. Plasma concentrations of alfentanil required to supplement nitrous oxide anesthesia for general surgery. Anesthesiology 1986;65:362-73. 8. Welling EC, Donegan J . Neuroleptanalgesia using alfentanil for awake craniotomy. Anesth Analg 1989;68:57-60.
9. Andrews CJH, Robertson JA, Chapman JM. Postoperative analgesia with intravenous infusion of alfentanil. Lancet 1985; ii:671. 10. Sebel PS, Bovill JG, Van der Haven A. Cardiovascular effects of alfentanil anaesthesia. Br J Anaesth 1982;54:1185-90.
11. Maitre PO, Vozeh S, Heykants J, Thomson DA, Stanski DR. Population pharmacokinetics of alfentanil: the average doseplasma concentration relationship and interindividual variability in patients. Anesthesiology 1986;66:>12. 12. Bovill JG, Sebel PS, Blackburn CL, Heykants J. The pharmacokinetics of alfentanil (R39209):a new opioid analgesic. Anesthesiology 1982;57:43943. 13. White PF. Clinical uses of intravenous anesthetic and analgesic infusions. Anesth Analg 1989;68:161-71. 14. Jaffe RS, Coalson D. Recurrent respiratory depression after alfentanil administration. Anesthesiology 1989;70:151-3.
References 1. Abramowicz M, ed. Exti acorporeal shock-wave lithotripsy for gallbladder stones. Med Lett Drugs Ther 1989;31:9-10. 2. Sackmann M, Delius hl, Sauerbruch T, et al. Shock-wave lithotripsy of gallbladder stones: the first 175 patients. N Engl J Med 1988;318:393-7. 3. Abbot MA, Samuel JR, \$e' bb DR. Anaesthesia for extracorporeal shock wave lithotripsy. Anaesthesia 1985;40:1065-72. 4. Stromskag KE, Steen PA. Comparison of interpleural and epidural anesthesia for cxtracorporeal shock wave lithotripsy. Anesth Analg 1988;67:1181-3. 5. Staritz M. Is extracorpcbreal biliary lithotripsy painless? My experience with three .hock-wave sources. N Engl J Med 1989;320:811.
15. Mahla ME, White SE, Moneta MD. Delayed respiratory depression after alfentanil. Anesthesiology 1988;69:59%5. 16. Harper MH, Hickey RF, Cromwell TH, Linwood S. The magnitude and duration of respiratory depression produced by fentanyl and fentanyl plus droperidol in man. J Pharmacol Exp Ther 1976;199:464-8. 17. Becker LB, Paulson BA, Miller RD, Severinghaus JW, Eger EI. Biphasic respiratory depression after fentanyl-droperidol or fentanyl alone used to supplement nitrous oxide anesthesia. Anesthesiology 1976;44:291-5. 18. Hynynen MJ, Turunen MT, Korttila KT. Effects of alfentanil and fentanyl on common bile duct pressure. Anesth Analg 1986;65:370-2. 19. Cohen SE, Woods WA, Wyner J. Antiemetic effect of droperido1 and metoclopramide. Anesthesiology 1984;60:67-9.
MD
and Alan D. Weinstock,
CONNELLY NR, WEINSTOCK AD. Continuous alfentanil infusion for extracorporeal shock wave lithotripsy of gallbladder stones. Anesth Analg 1990;70:299-302.
Extracorporeal shock zipave lithotripsy has recently been introduced in clinical trials for the treatment of cholelithiasis. General anesthesia, epidural anesthesia, and intravenous opiates haoe been used in the anesthetic management of patients undergoing this procedure. This report details our anesthetic management, which was used in 23 patients who underwent 27 procedures, and presents three illustrative cases. A continuous infusion of alfentanil and a 0.625-2.5-mg dose of droperidol were administered to the patients who were easily arousable during the procedure,
Extracorporeal shock wave lithotripsy (ECSWL) is used in the treatment of renal calculi, and has recently been introduced in the United States, through clinical trials, for the treatment of radiolucent cholelithiasis (1,2), with the possible benefits of avoiding surgery and postoperative morbidity. Patients are placed in contact with an electrode-containing water cushion that produces a shock wave. The wave is transmitted through body tissues and when it reaches the stone, shearing forces are produced, and the stone is disintegrated. The shocks are triggered by the electrocardiogram. Many different methods of anesthesia, including general anesthesia, epidural anesthesia, spinal anesthesia, intercostal blocks (3), and, most recently, interpleural anesthesia (4), have been described for renal ECSWL. General anesthesia, epidural anesthesia, and intravenous opiates have been used in the anesthetic management of patients undergoing biliary lithotripsy (2), a procedure that can be quite uncomfortable (5). At our institution, biliary lithotripReceived from the Department of Anesthesiology, Yale University School of Medicine, Yale-New Haven Hospital, New Haven, Connecticut. Accepted for publication November 1, 1989. Address correspondence to Dr. Connelly, Department of Anesthesiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510. 91990 by the International Anesthesia Research Society
MD
and were able to cooperate with positioning change requests. Our patients did not develop apnea, hernodynamically significant bradycardia, or chest wall rigidity. One patient became nauseated, and one patient experienced a hypotensive episode that was unheralded by a change in respiratory rate, heart rate, or oxygen saturation. The patients were comfortable throughout the procedure, alert upon arrival to the postanesthesia care unit, and satisfied with this technique. A continuous infusion of alfentanil can be successfully used for the management of patients undergoing biliary lithotripsy.
Key Words: ANESTHETICS, INTRAVENOUS. ANESTHESIA, BILIARY TRACT LITHOTRIPSY.
sy is under investigation for the treatment of cholelithiasis. To facilitate successful gallstone localization by ultrasound, methods of anesthesia must limit patient movement, as well as maintain patient comfort. Alfentanil, a narcotic with a rapid onset and short duration of action (6,7), offers some advantages over other possible methods of anesthesia for the management of patients undergoing biliary lithotripsy. We present here the data from 23 patients treated with this technique who underwent 27 ECSWL procedures, and detail three illustrative cases.
Case Reports Case 2 A 45-yr-old man presented for biliary lithotripsy. The patient had no significant past medical history aside from symptomatic cholelithiasis. The physical and laboratory examinations were normal. The patient received no premedication, was brought to the lithotripsy van (a trailer connected to the hospital that is equipped with an anesthesia machine and capabilities for full invasive monitoring), and placed in the prone position. Intravenous access was established and oxygen via nasal cannula was administered. Monitors included electrocardiography, noninvasive
CONNELLY A N D WEINSTOCK
blood pressure, and pulse oximetry. Droperidol (0.625 mg) and alfentanil (5 pg/kg) were administered. An alfentanil infusion was begun at 1 p g k g - ' . min-'. The patient required an additional two boluses of 5 pglkg, at 15 and 45 min, and was very comfortable throughout the 3.5-h procedure. The infusion was discontinued 10 min before the end of the procedure. Upon moving from the lithotripsy machine to the stretcher, the patient experienced nausea which was successfully treated with an additional 1.25 mg of droperidol. The patient was alert and comfortable upon arrival in the postanesthesia care unit.
Case 2 A 45-yr-old man, with no significant past medical history, was brought to the lithotripsy van for ECSWL. Monitoring, as in case 1, was applied and intravenous access was securcd. Droperidol (1.25 mg) was given, alfentanil (5 pgikg) was given as a bolus, and an alfentanil infusion was begun at 0.5 pg.kg-'. min-I. Because of dif?iculty in localizing the galIstones by ultrasound, the procedure took 4.5 h. The patient required two additional boluses of 5 pg/kg at 1 and 2 h into the procedure because of generalized discomfort. He also received a total of 3 mg of midazolam at the beginning of the procedure, in I-mg increments, because of agitation. The infusion was stopped 15 min before the end of the procedure, and the patient stated that he was comfortable throughout the entire procedure.
Case 3 A 46-yr-old man presented with a 1-yr history of right upper quadrant colic. He had a history of hypercholesterolemia and hypertension, for which he was taking 50 mg of metoprolol twice a day (baseline treated blood pressure was 110/80 mm Hg). The patient was positioned, an intravenous cannula was placed, and monitors were applied. The end-tidal C 0 2monitor was connected, via a plastic connection, to the nasal cannula. The patient was given 2.5 mg of droperidol and 5 pg/kg of alfentanil, and then begun on an alfentanil infusion of 0.5 pg-kg-'.min-'. Because of discomfort, thc patient required two additional boluses: one of 5 pglkg with the infusion increased to 1 pg.kg-'.min-' at 45 min into the procedure; and a second bolus 30 min later of 2.5 pgikg with the infusion remaining at 1 pg.kg-'. min-'. Forty-five minutcas after the second bolus, the
patient's blood pressure was noted to be 65/45 mm Hg, and the patient was minimally arousable. Immediately before this, the patient's oxygen saturation ~ 54 mm Hg, and the respiwas 97%, the P E T C Owas ratory rate was 11 breathdmin. The patient was placed in the Trendelenberg position, the alfentanil infusion was discontinued, and 400 pg of intravenous naloxone was given, while 100% 0, was administered via a facemask. The oxygen saturation remained above 94%, while 400 mL of lactated Ringer's solution was administered intravenously over a 10min period. The blood pressure returned to normal, the patient regained full consciousness, and the few remaining shocks were administered without restarting the alfentanil infusion. Shortly after arrival in the postanesthesia care unit, the patient's systolic blood pressure was 65 mm Hg. The patient was comfortable and responsive to commands, was breathing at a rate of 12 breathdmin, and was maintaining an oxygen saturation of 100%. One liter of lactated Ringer's solution was administered intravenously for 0.5 h, with a subsequent rise in the blood pressure. A 12-lead electrocardiogram was obtained, and was unchanged from the pre-ECSWL electrocardiogram. The patient did well after this episode, and was discharged from the hospital on the day after the ECSWL.
Discussion Biliary lithotripsy is performed with the use of three different types of devices (1). At our institution, the Dornier multipurpose lithotripter (MPL 9000), located some distance from the main operating room, is utilized. A maximum number of 1500 electrocardiogram-triggered shocks is given per treatment, with each session lasting from 1.25 to 4.5 h. Although a number of anesthetic approaches can be used, each has relative disadvantages. Because the technique mandates the patient being placed in the prone position, most anesthesiologists administer general anesthesia to these patients via a tracheal tube. This has the potential for both the adverse pulmonary effects of mechanical ventilation in the prone position and dislodgement of the tracheal tube when changing patient position. Regional techniques necessitate a high sensory level, with the possible complications of hypotension, local anesthetic toxicity, and too high a level. To limit patient motion, regional techniques would require additional intravenous supplementation. We were able to manage these patients successfully using solely intravenous sedation and analgesia. To maintain this level of comfort, a continuous infu-
ALFENTANIL FOR BlLlARY LITHOTRIPSY
ANtSTH ANALC 1990.70:2YY-30?
Table 1. Dose of Alfentanil Used
0%)
Duration of ECSWL (h)
125 98 80 97 96 70 107 90 125 90 72 61 66 57 65 88 89 89 97 89 100 70 85 50 75 72 57
3.5 4.5 2.25 1.25 4.5 2 1.25 1.75 3.25 1.5 1.5 1.5 1.5 1.5 1.5 1.5 2 1.5 2.5 2.25 2.25 2.5 2.25 1.5 1.5 2 1.5
Weight Patient 1'' 2 3
4 5 6 7 8" 9' 10" 11 12 13
14 15 16
17' 18' 19 20 21 22 23 24 25 26 27
Alfentanil total dose (A%)
11,000 12,250 7,000 2,750 11,000 2,950 7,200 3,700 11.000 5,500 1,500 4,600 6,500 2,075 2,000 2,650 5,500 3,650 2,500 1,450 7,200 2,950 7,500 3,000 2,125 5,000 4,600
( K g kg-' h ')
25 28 38 23 25 21 53 24 27 41 14 50 65 24 21 20 31 27 12 6 32 17 39 40 19 35 53
ECSWL, extracorporeal shockwave lithohipsy. '' " ' Identical superscripts indicate repeat procedures in the same patient.
sion technique seemed ideal. Alfentanil infusions have been previously used in spontaneously breathing patients (8,9), and have been shown to provide hemodynamic stability (10). Because of its quick onset and short duration of action (11,12), we chose to use alfentanil in this setting. After positioning the patient and placement of monitors, droperidol (0.625-2.5 mg) and a loading dose of 5 pg/kg of alfentanil were administered. Simultaneously, an alfentanil infusion of 0.5 pgkg-'. min-' was begun. If the patient became uncomfortable, an additional bolus of 2.5-5 pglkg was given, and the infusion was increased in increments of 0.25-0.5 pg.kg-'.min-'. The alfentanil infusion did not need to be turned higher than 1 pg-kg-'.min-' in any of our patients, and can be discontinued 5 1 5 min before the end of the procedure. The dosages of alfentanil given to the patients in our series are shown in Table 1. A continuous infusion technique offers the benefit of a steady plasma concentration with maintenance of patient comfort and the ability to adjust the plasma level rapidly as the level of stimulation changes (13). An infusion pump (Bard Harvard Mini Infusor, Har-
301
vard Apparatus Co., Inc., South Natick, Mass.) was used to administer the drug, which enables the user to adjust the infusion in increments of 0.25 pg.kg-'. min-' and alerts the user to the total amount of drug administered. Dose-dependent ventilatory depression occurs with alfentanil. Delayed respiratory depression has also been reported with alfentanil infusion techniques (14,15). The respiratory rate was maintained above 10 breathslmin in all of our patients and the oxygen saturation was maintained above 94%. The addition of droperidol to alfentanil has not been studied, although droperidol does not appear to increase the depressant effect upon ventilation when used in combination with fentanyl (16,17). Biliary tract spasm has been associated with the use of narcotics (18). Given the nature of the underlying disease process in these patients, if an episode of biliary colic occurs, the narcotics must be considered as a possible etiologic agent. However, none of the patients in our series experienced biliary spasm related to the alfentanil infusion. As both biliary tract manipulation and alfentanil itself can cause nausea and vomiting, patients were given droperidol (19) (0.625-2.5 mg) at the beginning of the procedure. None of the patients experienced nausea during the procedure. One patient became nauseated upon moving from the lithotripsy machine to the stretcher; this was successfully treated with an additional 1.25-mg dose of droperidol. The vagotonic effects of alfentanil can cause a slowing of the pulse rate. As ECSWL is triggered by the electrocardiogram if the heart rate becomes excessively slow, the duration of the procedure will be prolonged. If this is the case, and if no contraindications exist, the administration of an anticholinergic drug will decrease the time required for the lithotripsy. An occasional patient in our series, approximately 596, received 0.2 mg of glycopyrrolate for this reason. In summary, a continuous infusion of alfentanil can be successfully used for the management of patients undergoing biliary lithotripsy. Patients were easily arousable throughout the procedure, and were able to cooperate with positioning change requests. Our patients did not develop apnea, bradycardia, or chest wall rigidity. One patient became nauseated upon moving to the stretcher. One patient experienced a hypotensive episode unheralded by a change in respiratory rate, heart rate, or oxygen saturation. Possible explanations for this hypotension include intravascular volume depletion secondary to the patient's m n per os status, alfentanil-induced vagal tone, a-blockade from the droperidol administration, increased vagal tone induced by the lithotripsy shock
302
ANESTH ANALG 1990;70:299-302
waves on the peritoneum, or a combination of the above-mentioned factors. The patients were very alert upon arrival to the postanesthesia care unit and stated that they were comfortable during the procedure. The patients were satisfied with the level of analgesia, and were pleased that they were able to avoid general anesthesia. As with all administrations of anesthesia, this method requires a high level of vigilance. We present this report at a time when biliary lithotripsy is in its infancy in this country, and has the potential to become an important noninvasive method of treating gallstones. As this practice becomes more popular, anesthesiologists will be increasingly called upon to participate in the care of these patients. We thank Raymond Sinatra. MD, PhD, and Paul Barash, MD, for their help in the preparation of this report.
CONNELLY AND WEINSTOCK
6. White PF, Coe V, Shafer A, Sung ML. Comparison of alfentanil with fentanyl for outpatient anesthesia. Anesthesiology 1986; 64:99-106. 7. Ausems ME, Hug CC, Stanski DR, Burm AGL. Plasma concentrations of alfentanil required to supplement nitrous oxide anesthesia for general surgery. Anesthesiology 1986;65:362-73. 8. Welling EC, Donegan J . Neuroleptanalgesia using alfentanil for awake craniotomy. Anesth Analg 1989;68:57-60.
9. Andrews CJH, Robertson JA, Chapman JM. Postoperative analgesia with intravenous infusion of alfentanil. Lancet 1985; ii:671. 10. Sebel PS, Bovill JG, Van der Haven A. Cardiovascular effects of alfentanil anaesthesia. Br J Anaesth 1982;54:1185-90.
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