Comparison of ropivacaine 0.5% (in glucose 5%) with bupivacaine 0.5% (in glucose 8%) for spinal anaesthesia for elective surgery

Background. Hyperbaric solutions of ropivacaine have been usedsuccessfully to provide spinal anaesthesia. This study was designedto compare the clinical efficacy of hyperbaric ropivacaine withthat of the commercially available hyperbaric preparation ofbupivacaine. Methods. Forty ASA grade I–II patients undergoing lower-abdominal,perineal or lower-limb surgery under spinal anaesthesia wererecruited and randomized to receive ropivacaine 5 mg ml^–1(with glucose 50 mg ml^–1), 3 ml or bupivacaine 5 mg ml^–1(with glucose 80 mg ml^–1), 3 ml. The level and durationof sensory block, intensity and duration of motor block, andtime to mobilize and micturate were recorded. Patients wereinterviewed at 24 h and at 1 week to identify any residual problems. Results. All blocks were adequate for the proposed surgery,but there were significant differences between the two groupsin mean time to onset of sensory block at T10 (ropivacaine 5min; bupivacaine 2 min; P<0.005), median maximum extent (ropivacaineT7; bupivacaine T5; P<0.005) and mean duration of sensoryblock at T10 (ropivacaine 56.5 min; bupivacaine 118 min; P=0.001).Patients receiving ropivacaine mobilized sooner (ropivacainemean 253.5 min; bupivacaine 331 min; P=0.002) and passed urinesooner (ropivacaine mean 276 min; bupivacaine 340.5 min; P=0.01)than those receiving bupivacaine. More patients in the bupivacainegroup required treatment for hypotension (>30% decrease insystolic pressure; P=0.001). Conclusions. Ropivacaine 15 mg in glucose 50 mg ml^–1 providesreliable spinal anaesthesia of shorter duration and with lesshypotension than bupivacaine. The recovery profile for ropivacainemay be of interest given that more surgery is being performedin the day-case setting. Br J Anaesth 2003; 90: 304–8     

Trendelenburg position with hip flexion as a rescue strategy to increase spinal anaesthetic level after spinal block

BACKGROUND: When the level achieved by a spinal anaesthetic is too low toperform surgery, patients are usually placed in the Trendelenburgposition. However, cephalad spread of the hyperbaric spinalanaesthetics may be limited by the lumbar lordosis. The Trendelenburgposition with the lumbar lordosis flattened by hip flexion wasevaluated as a method to extend the analgesic level after theadministration of hyperbaric local anaesthetic. METHODS: When the pinprick block level was lower than T10 5 minafter intrathecal injection of hyperbaric bupivacaine (13 mg),patients were recruited to the study and randomly allocatedto one of the two positions: the Trendelenburg position withhip flexion (hip flexion group, n = 20) and the Trendelenburgposition without hip flexion (control group, n = 20). Each assignedposition was maintained for 5 min and then patients werereturned to the horizontal supine position. Spinal block levelwas assessed by pinprick, cold sensation, and modified Bromagescale at intervals for the following 150 min. RESULTS: The maximum level of pinprick and cold sensory block [median(range)] was higher in the hip flexion group [T4 (T8–C6)and T3 (T6–C2)] compared with the control group [T7 (T12–T4)and T5 (T11–T3)] (P < 0.001). The maximum motor blockademedian (range) was not different between the two groups being3 (3–3) in the hip flexion group vs 3 (0–3) in thecontrol group. CONCLUSIONS: When the level of spinal anaesthesia is lower than required,flexion of the hips in the Trendelenburg position may be usefulas a strategy attempt to increase the level of the block.     

Spinal anaesthesia with 0.5% hyperbaric bupivacaine in elderly patients: effects of duration spent in the sitting position

Sixty patients, aged 65–84 yr, undergoing minor urologicalsurgery under spinal anaesthesia remained sitting for 2 (group1, n=15), 5 (group 2, n=15), 10 (group 3, n=15), or 20 (group4, n=15) min after completion of the subarachnoid administrationof 3 ml of a 0.5% hyperbaric bupivacaine solution. They werethen placed in the supine position. Analgesia levels were assessedbilaterally using pinprick. Motor block was scored using a 12-pointscale. Systolic and diastolic arterial pressures and heart ratewere also recorded. Twenty minutes after the injection the upperanalgesia levels were lower (P<0.05) in group 4 (median T9.0)than in the groups 1–3 (medians T6.6–T8.5). Thehighest obtained levels (medians T5.7–T8.0) did not differbetween the groups, but occurred later (P<0.05) in group4 (median 35 min) than in groups 1–3 (medians 19–24min). There were no significant differences in the maximum degreeof motor block or haemodynamic changes between the four studygroups. Br J Anaesth 2001; 87: 738–42     

Comparison of hyperbaric and plain ropivacaine 15 mg in spinal anaesthesia for lower limb surgery

Background. Previously, plain ropivacaine 15 mg given intrathecallyhas been shown to be feasible for ambulatory surgery of lower-extremities.Hypothetically, hyperbaric solution could improve and shortenthe block. Methods. This prospective, randomized, double-blind study included56 patients undergoing surgery of lower extremities. They receivedintrathecally either 1.5 ml of ropivacaine 10 mg ml^–1and 0.5 ml of glucose 300 mg ml^–1 (HYP) or 2 ml of ropivacaine7.5 mg ml^–1 (PL). Results. All patients in Group HYP achieved T₁₀ dermatome analgesiabut only 64% (18/28) of Group PL. T₁₀ analgesia was reachedin 5 min (median, range 5–20 min) in the HYP group vs10 min (5–45 min) in the PL group (P=0.022), and fullmotor block in 10 min (5–45 min) vs 20 min (5–60min) (P=0.003), respectively. Group HYP had a longer durationof analgesia at T₁₀; 83 min (5–145 min) vs 33 min (0–140min) (P=0.004). Duration of sensory block from injection ofthe anesthetic to complete recovery was shorter in Group HYPthan in Group PL, 210 min (120–270 min) vs 270 min (210–360min) (P<0.001), as was duration of motor block, 120 min (5–150min) vs 210 min (120–330 min) (P<0.001). Patients ofGroup HYP attained discharge criteria earlier than those ofGroup PL (P=0.009). Conclusion. In comparison with the plain solution, 15 mg ofintrathecal hyperbaric ropivacaine produced a faster onset,greater success rate of analgesia at the level of T₁₀ dermatome,and faster recovery of the block.     

Influence of the baricity of a local anaesthetic agent on sedation with propofol during spinal anaesthesia

Background: This study examined the effect of different levels of spinalanaesthesia, induced by solutions of different baricity butcontaining the same amount of local anaesthetic agent, on therequirement for sedation with propofol. Methods: Thirty-six patients undergoing varicose vein surgery under spinalanaesthesia were randomly allocated to receive tetracaine 15mg in 3 ml of either glucose 5% (hyperbaric) or CSF (isobaric).I.V. propofol was started 5 min after the intrathecal injectionand was titrated to maintain a bispectral index (BIS) scoreof 65–75. The propofol requirements to maintain this rangein the two groups were compared every 5 min. Results: The propofol requirement was always lower in the hyperbaricgroup, with the differences becoming statistically significant20 min after the intrathecal injection. Total consumption ofpropofol over the 55 min of the study was also less in the hyperbaricgroup. Conclusion: The known difference in level of spinal anaesthetic block inducedby solutions of different baricity, but the same dose of localanaesthetic, was associated with different requirements forpropofol sedation as determined by BIS assessment.     

Density of spinal anaesthetic solutions of bupivacaine, levobupivacaine, and ropivacaine with and without dextrose

Background. Spread of intrathecal local anaesthetics is determinedprincipally by baricity and position of the patient. Hypobaricsolutions of bupivacaine are characterized by an unpredictablespread of sensory block whereas addition of dextrose 80 mg ml^–1provides a predictable spread but to high thoracic levels. Incontrast, dextrose concentrations between 8 and 30 mg ml^–1have shown reliable and consistent spread for surgery. Hence,the aim of this study was to determine the density of bupivacaine,levobupivacaine, and ropivacaine with and without dextrose atboth 23 and 37°C before embarking on clinical studies. Methods. Density (mg ml^–1) was measured using the methodof mechanical oscillation resonance, accurate to five decimalplaces on 1250 samples. 500 density measurements were performedin a randomized, blind fashion at 23 and 37°C on 10 plainsolutions of bupivacaine (2.5, 5, and 7.5 mg ml^–1) levobupivacaine(2.5, 5, and 7.5 mg ml^–1) and ropivacaine (2, 5, 7.5,and 10 mg ml^–1). Following this, 750 density measurementswere taken at 23 and 37°C on the 5 mg ml^–1 solutionsof bupivacaine, levobupivacaine, and ropivacaine with addeddextrose (10, 20, 30, 50, and 80 mg ml^–1). Results. There was a linear relationship between density anddextrose concentration for all three local anaesthetics (R²=0.99)at 23 and 37°C. The mean density of levobupivacaine 5 mgml^–1 was significantly greater than the densities of bupivacaine5 mg ml^–1 and ropivacaine 5 mg ml^–1 after adjustingfor dextrose concentration using analysis of covariance. Thisdifference existed both at 23 and 37°C. The mean (SD) densityof levobupivacaine 7.5 mg ml^–1 was 1.00056 (0.00003) mgml^–1, the lower 0.5% percentile (1.00047 mg ml^–1)lying above the upper limit of hypobaricity for all patientgroups. Conclusions. The density of local anaesthetics decreases withincreasing temperature and increases in a linear fashion withthe addition of dextrose. Levobupivacaine 5 mg ml^–1 hasa significantly higher density compared with bupivacaine 5 mgml^–1 and ropivacaine 5 mg ml^–1 at 23 and 37°Cboth with and without dextrose. Levobupivacaine 7.5 mg ml^–1is an isobaric solution within all patient groups at 37°C. Br J Anaesth 2004; 92: 547–51     

Spinal anaesthesia with articaine 5% vs bupivacaine 0.5% for day-case lower limb surgery: a double-blind randomized clinical trial

BACKGROUND: A local anaesthetic with fast onset and short reliable duration of anaesthesia may be preferable for out-patient lower limb surgery. Articaine is believed to act faster and to have a shorter duration of action than bupivacaine, but there are no conclusive data available. The purpose of this study was to compare articaine and bupivacaine for day-case lower limb surgery. METHODS: Eighty patients planned for day-case lower limb surgery enrolled in this study. Patients were randomized to receive hyperbaric articaine 80 mg or plain bupivacaine 15 mg intrathecally. Primary outcome variable was recovery time from motor block. Secondary outcomes were: onset of sensory and motor block, maximum spread of sensory block, time to micturition, discharge from the hospital, and complications. RESULTS: The groups were comparable for the medians and the range of the maximum blocks after 30 min. Median time to complete regression of motor block was 101 min (range 80-129) for articaine compared with 307 min (range 225-350) for bupivacaine (P<0.0005). First spontaneous micturition occurred after 257 min (210-293) in the articaine group and after 350 min (304-370) in the bupivacaine group (P<0.0005). In the articaine and bupivacaine groups, patients were discharged after 300 min (273-347) and 380 min (332-431), respectively (P<0.0005). There was no significant difference in the occurrence of complications between the groups. CONCLUSIONS: Spinal anaesthesia with 80 mg of hyperbaric articaine has a shorter duration than a spinal anaesthesia with 15 mg of plain bupivacaine in lower limb surgery of approximately 1 h duration.     

Hyperbaric articaine for day-case spinal anaesthesia

Background. Articaine and lidocaine are clinically very similarsuggesting that articaine could be suitable for day-case spinalanaesthesia. A dose–response study with articaine in ambulatoryspinal anaesthesia was therefore performed. Methods. In this randomized double-blind study, 90 day-casesurgery patients received spinal anaesthesia with 60 mg (A60),84 mg (A84) or 108 mg (A108) of hyperbaric articaine hydrochloride.Sensory block was tested with pinprick and motor block on amodified Bromage scale. A structured interview was performedon the first and seventh postoperative days. Results. Sensory block reached the T₁₀ dermatome in a median(range) of 5 (5–10) and was maintained at this level for70 (35–145), 70 (15–115) and 85 (20–115) minin the A60, A84 and A108 groups, respectively. Six patientsin the A108 group, two in the A84 group and one in the A60 grouphad maximum spread of analgesia to T₁ or higher (NS). Patientsin the A108 group needed more medication for hypotension (P=0.018),had more often nausea and vomiting (P=0.027), took oral fluidslater (P=0.031) and both sensory block recovery [median (range)][2.5 (2–4.5) h] (P=0.017) and motor block recovery [2(1.3–4) h] (P=0.009) were delayed. No patients in theA108 group needed opioid intraoperatively while fentanyl wasneeded in 5 (17%) and 2 (7%) patients in the A60 and A84 groups,respectively. Discharge criteria were attained in approximately4.5 h after articaine injection (NS) and no drug-related sequelaewere observed. Conclusions. Hyperbaric articaine 60 and 84 mg resulted in spinalanaesthesia allowing surgery of the lower extremities for about1 h. Recovery was rapid. Use of 108 mg of articaine is not recommendedbecause of frequent extensive cephalad spread of the block,accompanied by arterial hypotension and nausea.     

Effect of intrathecal diamorphine on block height during spinal anaesthesia for Caesarean section with bupivacaine

Background. Opioid analgesics are commonly added to intrathecalbupivacaine to improve patient comfort during Caesarean sectionunder spinal anaesthesia, and provide post-operative pain relief.We sought to discover if the addition of diamorphine influencedblock height when given with 0.5% w/v hyperbaric bupivacaine. Method. Eighty ASA I and II women of at least 37 weeks gestationand planned for elective Caesarean section under combined spinal–epiduralanaesthesia were recruited. They were randomized into two groupsto receive intrathecal hyperbaric bupivacaine 0.5% at an initialdose of 13 mg, with the next dose determined by the responseof the previous patient (dose interval 1 mg). One group alsoreceived diamorphine 400 µg intrathecally. If a blockheight of T5 to blunt light touch had been achieved after 20min, the block was deemed effective. A difference in the ED₅₀for hyperbaric bupivacaine between the groups would indicatethat diamorphine influenced block height. Intraoperative patientdiscomfort and need for analgesic supplementation was noted. Results. The median effective dose (ED₅₀) to achieve a T5 blockto light touch for Caesarean section using hyperbaric bupivacaine0.5% was 9.95 mg [95% confidence interval (CI) 9.0–10.90]and with the addition of diamorphine it was 9.3 mg (95% CI 8.15–10.40),while the ED₉₅ was 13.55 mg (95% CI 10.10–17.0) and 13.6mg (95% CI 9.15–18.05), respectively. Five women who hadreceived intrathecal diamorphine and 13 who had not receiveddiamorphine needed intraoperative supplementation (not significant). Conclusion. The addition of intrathecal diamorphine does notappear to influence block height.     

Effect of peri- and postoperative epidural anaesthesia on pain and gastrointestinal function after abdominal hysterectomy

In a double blind study we have investigated the effects ofepidural local anaesthesia (LA), when added to general anaesthesia(GA) and postoperative paracetamol and NSAID, on postoperativepain and gastrointestinal function in patients undergoing openhysterectomy. Sixty patients were randomized into three studygroups: GA, and postoperative paracetamol and NSAID (GA, n=20);GA, paracetamol, NSAID, intraoperative epidural lidocaine and24-h postoperative epidural saline (Saline, n=20); or GA, paracetamol,NSAID, intraoperative epidural lidocaine and 24-h postoperativeepidural bupivacaine (Bupi, n=20). Patients were observed for72 h postoperatively. Pain at rest, during cough, and mobilization,request for supplementary morphine, and time to first postoperativeflatus, was reduced in patients receiving 24-h postoperativeepidural anaesthesia, compared with the two other groups. However,these effects of epidural LA, were not sustained beyond theperiod of infusion, and no differences in PONV, time to firstpostoperative defecation, mobilization or time to dischargefrom hospital were observed between groups. A 24 h postoperativeepidural infusion with bupivacaine, when added to postoperativeparacetamol and NSAID, reduces pain and opioid requirements,but has only limited effects on gastrointestinal function andpatient recovery. Br J Anaesth 2001; 87: 577–83     

Efficacy and uptake of ropivacaine and bupivacaine after single intra-articular injection in the knee joint

The efficacy of ropivacaine 100 mg (5 mg ml^–1),150 mg (7.5 mg ml^–1) and 200 mg (10 mg ml^–1)and bupivacaine 100 mg (5 mg ml^–1) givenby intra-articular injection into the knee after the end ofsurgery was studied in 72 ASA I–II patients scheduledfor elective knee arthroscopy under general anaesthesia in arandomized, double-blind study. Kapake (paracetamol 1 gand codeine 60 mg) was given as a supplementary analgesic.Pain scores were assessed 1–4 h after surgery and a verbalrating scale of overall pain severity was assessed on secondpostoperative day. Ropivacaine or bupivacaine concentrationswere determined in peripheral venous plasma up to 3 h afterinjection in eight patients in each group. Verbal rating painscores were lower with ropivacaine 150 mg compared withbupivacaine 100 mg (P<0.05). There was a tendency forlower analgesic consumption and pain scores with all doses ofropivacaine (not significant). The mean (SD) maximum total plasmaconcentrations of ropivacaine were 0.64 (0.25), 0.78 (0.43),and 1.29 (0.46) mg litre^–1 after 100, 150 and200 mg. The corresponding unbound concentrations were 0.018(0.009), 0.024 (0.020) and 0.047 (0.022) mg litre^–1.Both were proportional to the dose. The maximum total concentrationafter bupivacaine 100 mg was 0.57 (0.36) mg litre^–1.The time to reach maximum plasma concentration was similar forall doses and varied between 20 and 180 min. All concentrationswere well below the threshold for systemic toxicity. Br J Anaesth 2001; 87: 570–6     

Articaine versus lidocaine plus bupivacaine for peribulbar anaesthesia in cataract surgery

Background. We compared the efficacy and safety of articaine2% with a mixture of lidocaine 2% and bupivacaine 0.5% withouthyaluronidase for peribulbar anaesthesia in cataract surgery. Method. In this double-blind randomized clinical study, 58 cataractpatients were allocated to receive either articaine 2% withepinephrine 1:200 000 or a mixture of equal parts of lidocaine2% with epinephrine 1.25:100 000 and bupivacaine 0.5%. Ocularand eyelid movement scores, the number of supplementary injections,total volume of solution used and pain and complications duringinjection and surgery were used as clinical end-points. Results. Articaine produced greater akinesia after 5 min (P=0.03).Eighteen patients (60%) in the articaine group and 26 (93%)in the lidocaine/bupivacaine group required a second injection(P=0.003). A third injection was needed by two patients (7%)in the articaine group and 12 (43%) in the lidocaine/bupivacainegroup (P=0.001). The total mean volume of local anaestheticrequired to achieve akinesia was mean 9.4 (SD 1.7) ml in thearticaine group and 11.28 (1.86) ml in the lidocaine/bupivacainegroup (P<0.001). Median pain score was lower in the articainegroup than in lidocaine/bupivacaine group during injection (P=0.004)and surgery (P=0.014). There was no difference between the groupsfor the incidence of complications. Conclusion. Articaine 2% without hyaluronidase is more advantageousthan a mixture of lidocaine 2% and bupivacaine 0.5% withouthyaluronidase for peribulbar anaesthesia in cataract surgery. Br J Anaesth 2004; 92: 231–4     

Laparoscopic cholecystectomy under segmental thoracic spinal anaesthesia: a feasibility study

Background: Laparoscopic surgery is normally performed under general anaesthesia,but regional techniques have been found beneficial, usuallyin the management of patients with major medical problems. Encouragedby such experience, we performed a feasibility study of segmentalspinal anaesthesia in healthy patients. Methods: Twenty ASA I or II patients undergoing elective laparoscopiccholecystectomy received a segmental (T10 injection) spinalanaesthetic using 1 ml of bupivacaine 5 mg ml^–1 mixedwith 0.5 ml of sufentanil 5 µg ml^–1. Other drugswere only given (systemically) to manage patient anxiety, pain,nausea, hypotension, or pruritus during or after surgery. Thepatients were reviewed 3 days postoperatively by telephone. Results: The spinal anaesthetic was performed easily in all patients,although one complained of paraesthesiae which responded toslight needle withdrawal. The block was effective for surgeryin all 20 patients, six experiencing some discomfort which wasreadily treated with small doses of fentanyl, but none requiringconversion to general anaesthesia. Two patients required midazolamfor anxiety and two ephedrine for hypotension. Recovery wasuneventful and without sequelae, only three patients (all forsurgical reasons) not being discharged home on the day of operation. Conclusions: This preliminary study has shown that segmental spinal anaesthesiacan be used successfully and effectively for laparoscopic surgeryin healthy patients. However, the use of an anaesthetic techniqueinvolving needle insertion into the vertebral canal above thelevel of termination of the spinal cord requires great cautionand should be restricted in application until much larger numbersof patients have been studied.     

Spinal anaesthesia for Caesarean section with bupivacaine 5 mg ml(-1) in glucose 8 or 80 mg ml(-1)

The standard spinal preparation of bupivacaine contains a highconcentration of glucose (80 mg ml^–1). However,the addition of only a small amount of glucose (8 mg ml^–1)to plain solutions of bupivacaine results in a solution which,although no more than marginally hyperbaric, produces a morepredictable block when used for spinal anaesthesia in non-pregnantpatients. However, bupivacaine 5 mg ml^–1 inglucose 8 mg ml^–1 has a density [1.00164 (SD0.00008) at 37°C] which is relatively greater than thatof the cerebrospinal fluid (CSF) of the pregnant patient atterm (1.0003 at 37°C) because CSF density decreases duringpregnancy. Therefore, a double-blind, randomized, controlledstudy was carried out to compare intrathecal bupivacaine (glucose8 mg ml^–1) with bupivacaine (glucose 80 mg ml^–1)in 40 pregnant patients at term. Although there was no differencebetween groups in onset of sensory block, dose of ephedrineor patient satisfaction, patients receiving bupivacaine (5 mg ml^–1)with glucose (8 mg ml^–1) had persistently highersensory blocks between 60 and 120 min after intrathecalinjection, suggesting that the spread of spinal solutions inthe pregnant patient at term is not dependent on density. Br J Anaesth 2001; 86: 805–7     

Analgesia and discharge following preincisional ilioinguinal and iliohypogastric nerve block combined with general or spinal anaesthesia for inguinal herniorrhaphy

BACKGROUND: Preincisional ilioinguinal and iliohypogastric nerve block (IINB) reduces postoperative analgesics after inguinal herniorrhaphy. The effect of an IINB on postoperative pain and discharge profile was therefore studied in day-surgery patients undergoing inguinal herniorrhaphy with general or spinal anaesthesia. METHODS: Seventy ASA I-II adult patients scheduled for inguinal herniorrhaphy received an IINB before the surgical incision with 15 ml of 0.5% bupivacaine. In a randomized fashion half of them received general anaesthesia with spontaneous breathing via a laryngeal mask (GA-group) and the other half received spinal anaesthesia with 5 mg of bupivacaine diluted with sterile water to 2.5-ml volume (SPIN-group). In the postanaesthesia care unit (PACU), pain was assessed on a scale from 0 to 10 (VAS) and ketorolac 30 mg i.v. (VAS < 5), or fentanyl 0.05 mg i.v. (VAS > or = 5) was administered as scheduled. In the day surgery unit and at home the analgesic was a tablet of ibuprofen 200 mg + codeine 30 mg (VAS > or = 3). RESULTS: Patients in the SPIN-group reported lower postoperative pain scores at 30, 60 min (P < 0.0001) and 120 min (P < 0.05) after surgery, and longer time to first analgesic use (P < 0.0001). Patients in the GA-group had a shorter time to discharge without voiding (P < 0.001) and with voiding (P < 0.05). After discharge, there were no significant differences between the groups regarding pain scores at rest and at walking, or the doses of analgesic. Adverse events were rare in both groups. CONCLUSION: Only a relatively short immediate analgesic benefit could be demonstrated by a combination of IINB with spinal anaesthesia compared with IINB combined with general anaesthesia. The use of general anaesthesia facilitated an earlier postoperative discharge than spinal anaesthesia.     

Double-blind comparison of ropivacaine 7.5 mg ml(-1) with bupivacaine 5 mg ml(-1) for sciatic nerve block

Two groups of 12 patients had a sciatic nerve block performedwith 20 ml of either ropivacaine 7.5 mg ml^–1 or bupivacaine5 mg ml^–1. There was no statistically significant differencein the mean time to onset of complete anaesthesia of the footor to first request for post-operative analgesia. The qualityof the block was the same in each group. Although there wasno statistically significant difference in the mean time topeak plasma concentrations the mean peak concentration of ropivacainewas significantly higher than that of bupivacaine. There wereno signs of systemic local anaesthetic toxicity in any patientin either group. Br J Anaesth 2001; 86: 674–7     

Spinal anaesthesia indirectly depresses cortical activity associated with electrical stimulation of the reticular formation

Background. Neuraxial blockade reduces the requirements forsedation and general anaesthesia. We investigated whether lidocainespinal anaesthesia affected cortical activity as determinedby EEG desynchronization that occurs following electrical stimulationof the midbrain reticular formation (MRF). Methods. Six goats were anaesthetized with isoflurane, and cervicallaminectomy performed to permit spinal application of lidocaine.The EEG was recorded before, during and after focal electricalstimulation (0.1, 0.2, 0.3 and 0.4 mA) in the MRF while keepingthe isoflurane concentration constant. Results. During lidocaine spinal anaesthesia, the spectral edgefrequency (SEF) after MRF electrical stimulation (13.6 (SD 1.0)Hz, averaged across all stimulus currents) was less than theSEF during control and recovery periods (18.6 (3.6) Hz and 17.2(2.2) Hz, respectively; P<0.05). Bispectral index valueswere similarly affected: 69 (10) at control compared with 55(6) during the spinal block (P<0.05). Conclusions. These results suggest that lidocaine spinal anaesthesiablocks ascending somatosensory transmission to mildly depressthe excitability of reticulo–thalamo–cortical arousalmechanisms. Br J Anaesth 2003; 91: 233–8     

Dose-response in infants receiving caudal anaesthesia with bupivacaine*

Caudal epidural anaesthesia was performed in 25 awake or sedated infants, the sensory levels measured and the dose-response determined (bupivacaine dose [ml kg^?1] v. sensory level). The infants were divided into two groups based on body weight, group 1 (1.9–2.6 kg) and group 2 (3.4–7.0 kg). There was a significant difference between the dose-response when comparing group 1 to group 2 (P < 0.01). Smaller infants require a larger volume (ml kg^?1) of local anaesthetic to achieve mid-thoracic sensory levels than larger infants. In small infants, we recommend increasing the volume of local anaesthetic while still limiting the total bupivacaine dose to 3.25 mg kg^?1 by using 1.6 ml kg^?1 of bupivacaine 0.20% (3.20 mg kg^?1) instead of 1.3 ml kg^?1 of bupivacaine 0.25% (3.25 mg kg^?1).     

Comparison of L-bupivacaine 0.75% and lidocaine 2% with bupivacaine 0.75% and lidocaine 2% for peribulbar anaesthesia

Background. L-Bupivacaine has a safer side-effect profile thanbupivacaine. We compared the efficacy of a mixture of L-bupivacaine0.75% and lidocaine 2% with bupivacaine 0.75% and lidocaine2% for peribulbar anaesthesia in cataract surgery. Methods. Ninety patients were allocated randomly to receive8 ml of a mixture of equal parts of bupivacaine 0.75% and lidocaine2% or an equal volume of L-bupivacaine and lidocaine 2%. Hyaluronidase15 IU ml^–1 was added to both solutions. Results. There were significant differences between the groupsin clinical end-points. The median time at which the block wasadequate to start surgery was 4 min (interquartile range4–8 min) in the bupivacaine group and 8 min (5–12min) in the L-bupivacaine group (P=0.002). Median ocular andeyelid movement scores were similarly significantly decreasedin the bupivacaine group compared with the L-bupivacaine groupat all times (P0.03). There was no difference between groupsin the incidence of minor complications. Conclusions. A mixture of bupivacaine 0.75% and lidocaine 2%provides faster onset time than a mixture of L-bupivacaine 0.75%and lidocaine 2%. Br J Anaesth 2003; 90: 512–14     

Block of the sacral segments in lumbar epidural anaesthesia

Background. Block of the first sacral segment is often delayedin lumbar epidural anaesthesia. The addition of either epinephrineor sodium bicarbonate to the local anaesthetic enhances theefficacy of epidural block. We assessed the block of lumbo-sacralsegments in lumbar epidural anaesthesia adding epinephrine and/orbicarbonate to lidocaine. Methods. Twenty-seven patients undergoing lumbar epidural anaesthesiawith lidocaine 2%, 17 ml at L4-5 or L5-S1 were randomly dividedinto three groups. Plain lidocaine, lidocaine with 1:200 000epinephrine or lidocaine–epinephrine–bicarbonatewas administrated via an epidural catheter. The pain thresholdafter repeated electrical stimulation was used to assess thesensory block at the L2, S1, and S3 segments. Motor block wasevaluated using the Bromage scale. Results. Patient characteristics were comparable between thegroups. The pH of lidocaine in the lidocaine–epinephrine–bicarbonategroup was significantly higher than that in other groups. Painthresholds at the S1 and S3 segments in the lidocaine–epinephrine–bicarbonategroup were significantly higher than those in the lidocaine–epinephrinegroup. However, differences in the pain threshold at the L2segment between groups were insignificant. The time to onsetof sensory block at the S1 and S3 in the lidocaine–epinephrine–bicarbonategroup was significantly shorter than that in the lidocaine group.Pain threshold by pinprick test was approximately within the30–50 mA range. Conclusion. A combination of lidocaine, bicarbonate, and epinephrineincreases the pain threshold over the sacral segments. Br J Anaesth 2003; 90: 173–8