Influence of the injection site (L2/3 or L3/4) and the posture of the vertebral column on selective spinal anesthesia for ambulatory knee arthroscopy.

BACKGROUND: We tested the hypothesis that selective spinal anesthesia for ambulatory knee arthroscopy can be accomplished with a small dose of bupivacaine at the L3/4 interspace with or without a head-down tilt of 5 degrees when the patients were in the lateral decubitus position. METHODS: In this double-blind study, 123 patients were randomly allocated to receive spinal anesthesia with 4 mg of hyperbaric bupivacaine inserted at either the L2/3 interspace, while the vertebral column was kept horizontal (L2/3 group), or the L3/4 level, with the vertebral column horizontal (L3/4H) or tilted 5 degrees head-down (L3/4T). At 7 min, an additional head down tilt was used in all groups if the sensory block was inadequate. RESULTS: In the L3/4T group the sensory block (Th8) reached a significantly higher level 30 min after spinal injection, compared with both the L2/3 (Th10) and L3/4H (Th11) groups. In the L3/4H group, 39% of the patients needed an additional tilt for 3 min at 7 min, compared with 10% (P=0.004) in the L3/4T group. Sacral block developed later and recovered faster (P<0.05) in the L3/4T group compared to the L3/4H group. Home-readiness was achieved equally fast in all groups. CONCLUSION: When producing selective spinal anesthesia, the posture of the vertebral column is a major determinant of both sensory and motor segments to be blocked. A 4-mg dose of hyperbaric bupivacaine at the L3/4 interspace with a 5 degrees head-down tilt of the vertebral column for 6 min is recommended for knee arthroscopy.

Ondansetron does not prevent pruritus induced by low-dose intrathecal fentanyl.

BACKGROUND: Addition of an opioid to low-dose spinal anesthesia with bupivacaine improves the quality and success of anesthesia. However, the intrathecal fentanyl-induced pruritus is as high as 75%. We hypothesized that after administration of 4 or 8 mg of prophylactic IV ondansetron, the incidence of pruritus induced by low-dose intrathecal fentanyl would be significantly lower than after placebo. METHODS: In this double-blind study, 90 outpatients undergoing knee arthroscopy received 3 mg of bupivacaine + 10 micro g fentanyl intrathecally. Before spinal puncture, the patients received randomly either saline (P) or ondansetron 4 mg (O4) or 8 mg (O8) IV. They were asked about pruritus frequently, and they estimated its severity on a scale of 0-10. RESULTS: There was no difference in the incidence of pruritus between the three groups: pruritus occurred in 17 (57%), in 21 (75%) and in 19 patients (70%) in P, O4 and O8 groups, respectively. The pruritus was mostly mild. Four patients in the placebo group, three in the O4 and four patients in the O8 groups considered it severe. One patient in each group requested treatment for pruritus; after IV naloxone their pruritus was relieved. Neither time to pruritus nor duration of pruritus differed between the groups. One patient in each group developed a long-lasting (>10 h) pruritus. CONCLUSIONS: After prophylactic administration of 4 or 8 mg of ondansetron IV, the incidence, duration and severity of pruritus were similar to placebo. Ondansetron does not prevent pruritus induced by low-dose intrathecal fentanyl.

Intrathecal hyperbaric bupivacaine 3 mg + fentanyl 10 microg for outpatient knee arthroscopy with tourniquet.

BACKGROUND: Combination of local anesthetic and opioid enables the use of less spinal anesthetic and increases the success of anesthesia. Intrathecal opioid does not prolong motor recovery and thus should not delay discharge home. We hypothesized that 3 mg of hyperbaric bupivacaine with 10 microg of fentanyl permits fast-tracking or shorter stay in post anesthesia care unit (PACU), and earlier discharge home, compared with 4 mg of hyperbaric bupivacaine. METHODS: In this double-blind study, 100 outpatients undergoing knee arthroscopy received randomly either 4 mg of bupivacaine (B4) or 3 mg of bupivacaine + 10 microg fentanyl (B3F) intrathecally. The volume of 0.8 ml was injected at the L2/3 interspace over a 2-min period. A lateral decubitus position was maintained for 10 min. The sensory block was recorded by using thermal stimuli, and motor block was assessed according to a modified Bromage scale. Fast-tracking criteria were complete recovery of motor block, sensory block Th12 or lower and stable vital signs. RESULTS: One block (1%) failed. Motor recovery was faster in the B3F group: 60% of the patients recovered in 80 min or less compared with 28% in group B4 (P = 0.002). The PACU-time was shorter: 36 (10-103) vs. 55 (10-140) min, respectively (P = 0.005). Seventeen (B3F) vs. nine patients (B4) could bypass PACU (NS). Time to discharge home was similar in both groups. In the B3F group, 75% of the patients developed pruritus. CONCLUSION: Both solutions produced reliable spinal anesthesia for outpatient knee arthroscopy. The PACU-time was shorter in the bupivacaine-fentanyl group, but both groups reached home-readiness equally.

Selective spinal anesthesia: a comparison of hyperbaric bupivacaine 4 mg versus 6 mg for outpatient knee arthroscopy.

IMPLICATIONS: A low-dose (4 mg), low-volume (0.8 mL), low-flow (2 min) technique with hyperbaric bupivacaine toward the dependent side oriented injection and maintenance of the lateral decubitus position for 10 min produced selective spinal anesthesia with rapid recession of motor block and early discharge home.

Postoperative nausea and vomiting after sevoflurane with or without ondansetron compared with propofol in female patients undergoing breast surgery.

IMPLICATIONS: We studied 180 female patients undergoing breast surgery. The patients were randomly allocated to receive one of three anesthetic techniques. Compared with either propofol or sevoflurane alone, sevoflurane with ondansetron resulted in a decreased incidence of postoperative nausea and vomiting. Sevoflurane with ondansetron prophylaxis is a good alternative to propofol with respect to avoiding postoperative nausea and vomiting.

Recovery following general anesthesia with isoflurane or enflurane for outpatient dentistry and oral surgery.

Anesthesia was induced in 120 unpremedicated, healthy patients undergoing outpatient dentistry or oral surgery with methohexital, and endotracheal intubation facilitated with succinylcholine. Anesthesia was maintained randomly with either enflurane or isoflurane in nitrous oxide and oxygen (50%) administered in a nonrebreathing circuit using spontaneous respiration. After both enflurane and isoflurane anesthesia, it took 12-13 minutes before the patients were oriented as to time and place. The patients' ability to walk along a straight line normalized significantly (p < .05) more quickly after isoflurane than after enflurane anesthesia. Long enflurane anesthesia (>90 minutes) was associated with a significantly (p < .05-p < .01) slower recovery of walking ability and of psychomotor performance in a perceptual speed test than was short enflurane anesthesia (<40 minutes). With isoflurane the speed of recovery did not depend on the duration of anesthesia. After both anesthetic techniques, 25-26% of the patients had nausea or vomited. We conclude that using spontaneous respiration recovery is faster after isoflurane anesthesia than after enflurane anesthesia and that isoflurane should be preferred to enflurane for long anesthesia of outpatients.

Anaesthesia induction and lower oesophageal sphincter pressure.

The effects of some drugs generally used in premedication for and induction of anaesthesia on the lower oesophageal sphincter (LOS) pressure were investigated in 30 dogs, using the modern oesophageal manometric technique. In thiopental-induced anaesthesia, a distinct pressure gradient was noted between the LOS and gastric pressure. Atropine eliminated this pressure gradient almost completely. Metoclopramide increased the LOS pressure significantly, and subsequent atropine administration was unable to bring it down. Metoclopramide administered after atropine was unable to elevate the LOS pressure reduced by atropine. Succinylcholine had no observable lasting effect on the LOS pressure. The present findings seem to indicate that of the drugs generally used in premedication for and induction of anaesthesia, atropine significantly reduces the LOS competence, thereby creating favourable conditions for gastro-oesophageal reflux (GOR) and consequent postoperative pulmonary complications. Use of metoclopramide in premedication for or induction of anaesthesia to eliminate the depressant effect of atropine on the LOS pressure appears to be indicated.