Background and ObjectivesSurgical procedures previously considered too lengthy for the ambulatory surgery setting are now being performed during spinal anesthesia. The complete recovery profile of tetracaine and bupivacaine are now of interest but are not available in the literature. This study was conducted to compare times to ambulation, voiding, and complete block resolution, as well as the incidence of back and radicular pain, after spinal anesthesia with lidocaine, bupivacaine, and tetracaine.MethodsTwelve adult volunteers underwent spinal anesthesia on three separate occasions with three local anesthetics (lidocaine 100 mg, bupivacaine 15 mg, and tetracaine 15 mg in hyperbaric solutions) in random order and in a double-blind fashion. A 24-gauge Sprotte spinal needle was placed at the L2-3 interspace. The level of analgesia to pinprick was determined moving cephalad in the midclavicular line until a dermatome was reached at which the prick felt as sharp as over an unblocked dermatome. One dermatome caudad to this point was recorded every 5 minutes as the level of analgesia. We also recorded the times to voiding, unassisted ambulation, and complete resolution of sacral anesthesia.ResultsThere was no difference between tetracaine and bupivacaine in time taken for two- and four-segment regression of the analgesia level. However, times to ambulation and complete resolution of the block were significantly shorter with bupivacaine then with tetracaine. With lidocaine, times to four-segment regression, ambulation, voiding, and complete regression of the block were significantly shorter than with bupivacaine and tetracaine. Time to two-segment regression did not differ among local anesthetics. Back and radicular pain symptoms were reported by three subjects after lidocaine subarachnoid block but not after tetracaine or bupivacaine.ConclusionAmong individual subjects, lidocaine exhibited the shortest recovery profile. However, the recovery profiles of the three anesthetics were very variable between subjects. Time to meeting discharge criteria after bupivacaine or tetracaine was faster in a few subjects than that after lidocaine in other subjects. For ambulatory anesthesia, times to two- and four-segment regression do not accurately predict time to readiness for discharge after spinal anesthesia.
To evaluate the effects of induced hypercapnia on the electroretinogram (ERG) in beagle dogs anaesthetized with isoflurane and sevoflurane. Binocular, full-field flash photopic and scotopic ERGs were obtained from six healthy neutered female beagle dogs. In order to determine Vmax and the photopic negative response (PhNR), photopic ERG luminance-response curves were generated with 17 different light stimuli. Photopic flicker ERGs were obtained at 30-Hz temporal frequency. Scotopic ERGs were recorded after 35 min of dark adaptation. For all animals, this procedure was performed once in four different sessions: isoflurane + end-tidal [CO(2)] at 35 mmHg +/- 3 mmHg (ISON), isoflurane + end-tidal [CO(2)] at 65 mmHg +/- 3 mmHg (ISOH), sevoflurane + end-tidal [CO(2)] at 35 mmHg +/- 3 mmHg (SEVON), isoflurane + end-tidal [CO(2)] at 65 mmHg +/- 3 mmHg (SEVOH). In photopic conditions, b-wave amplitudes were significantly smaller in hypercapnic groups (ISON = 170.6 +/- 12.1 microV; ISOH = 132.6 +/- 24.9 microV; SEVON = 170.9 +/- 14.4 microV; SEVOH = 130.2 +/- 22.8 microV). Similarly, in scotopic conditions, b-wave amplitudes were significantly decreased when CO(2) was increased (ISON = 89.4 +/- 14.7 microV; ISOH = 58.2 +/- 17.6 microV; SEVON = 93.4 +/- 24.1 microV; SEVOH = 56.2 +/- 22.2 microV). Flicker peak times were significantly increased in hypercapnic groups (ISON = 25.9 +/- 0.4 ms; ISOH = 27.7 +/- 1.2 ms; SEVON = 25.9 +/- 1.5 ms; SEVOH = 27.2 +/- 0.7 ms). Our results clearly indicate that induced hypercapnia significantly alters the genesis of the electroretinogram at level of ON-pathway and suggest that OFF-pathway is unaffected and that ERGs obtained from isoflurane or sevoflurane anaesthetized dogs are almost identical. Control of hypercapnia must be taken into consideration when ERGs are performed under inhaled anaesthesia in dogs.
This prospective, randomized double-blind study was conducted to examine the effect of intraoperative opioid (fentanyl) supplementation on postoperative analgesia, emesis, and recovery in ambulatory patients receiving propofol-nitrous oxide anesthesia. Eighty patients undergoing ambulatory gynecologic laparoscopy participated. Confounding variables that could influence the incidence of postoperative emesis were controlled. Patients received either fentanyl 100 micrograms (Group I) or ketorolac 60 mg (Group II) intravenously (IV) at the time of anesthetic induction. No further analgesic supplements were given intraoperatively. Anesthesia was induced with propofol and maintained with propofol-nitrous oxide. Atracurium was used for muscle relaxation and reversed with neostigmine and glycopyrrolate. Postoperative pain during early recovery was treated with IV fentanyl 25-50 micrograms (Group I) or IV ketorolac 15-30 mg (Group II). Subsequent breakthrough pain in both groups was treated with IV fentanyl 25 micrograms increments as needed (rescue analgesia). Eighty-four percent of patients in Group I required analgesics during early recovery versus 56% of patients in Group II (P < 0.05). Maintenance dose of propofol was significantly lower in Group I (129 +/- 35 micrograms.kg-1.min-1 than in Group II (170 +/- 63 micrograms.kg-1.min-1. Immediate recovery (emergence) in the two groups was comparable, despite different propofol requirements. Although the incidence of emetic sequelae in the postanesthesia care unit was not significantly different between the two treatment groups, a significantly larger number of patients in Group I (fentanyl group) had emetic sequelae that required therapeutic intervention (Group I 29% versus Group II 10%). Patients in Group I also took a significantly longer time to ambulate and meet criteria for home discharge. These results indicate that, in patients undergoing ambulatory gynecologic laparoscopy, the practice of administering a small dose of fentanyl at the time of anesthetic induction reduces maintenance propofol requirement, but fails to provide effective postoperative analgesia. Fentanyl administration at anesthetic induction increased the need for rescue antiemetics. The relative severity of emetic sequelae could have contributed to delay in ambulation and discharge.
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