Wash-in and wash-out curves of sevoflurane and isoflurane in morbidly obese patients

BACKGROUND

The aim of this prospective, randomized study is to compare sevoflurane and isoflurane pharmacokinetics in morbidly obese patients.

METHODS

With Ethical Committee approval and written informed consent, 14 obese patients (BMI >35 kg/m2), ASA physical status II, undergoing laparoscopic, silicone-adjustable gastric banding were randomly allocated to receive either sevoflurane (n=7) or isoflurane (n=7) as main anesthetic agents. General anesthesia was induced with 1 mg x kg-1 fentanyl, 6 mg x kg-1 sodium thiopental, and 1 mg x kg-1 succinylcholine followed by 0.4 mg kg-1 x h-1 atracurium bromide (doses were referred to ideal body weight). Intermittent positive pressure ventilation (IPPV) was applied using a Servo-900C ventilator with a nonrebreathing circuit and a 15 l x min-1 fresh gas flow (tidal volume: of 10 ml x kg-1; respiratory rate: 12 breaths/min; inspiratory to expiratory time ratio of 1:2) using an oxygen/air mixture (FiO2=50%), while supplemental boluses of thiopental or fentanyl were given as indicated in order to maintain blood pressure and heart rate values within +/-20% from baseline. After adequate placement of tracheal tube and stabilization of the ventilation parameters, 2% sevoflurane or 1.2% isoflurane was given for 30 min via a nonrebreathing circuit. End-tidal samples were collected at 1, 5, 10, 15, 20, 25 and 30 min, and measured using a calibrated infrared gas analyzer. General anesthesia was then maintained with the same inhalational agents, while supplemental fentanyl was given as indicated. After the last skin suture the inhalational agents were suspended, and the end tidal samples were collected at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5 min. Then the lungs were manually ventilated until extubation.

RESULTS

No differences in age, gender and body mass index were reported between the two groups. Surgical procedure required 91+/-13 in the sevoflurane group and 83+/-32 min in the isoflurane group. The FA/FI ratio was higher in the sevoflurane group from the 5th to the 30th min. Also the washout curve was faster in the sevoflurane group during the observation period; however, the observed differences were statistically significant only 30 and 60 sec after discontinuation of the inhalational agents.

CONCLUSIONS

The results of this prospective, randomized study confirmed that sevoflurane provides more rapid wash-in and wash-out curves than isoflurane also in the morbid obese patient.

[Epidural vs general anaesthesia]

BACKGROUND

Aim of this study is to determine if and how the anaesthesia technique can significantly influence the outcome in patients after major orthopaedic surgery in terms of: patrimony of red blood cells (blood loss and erythropoiesis), incidence of intra and postoperative complications, postoperative pain control and hospital stay.

METHODS

210 patients, ASA physical status I-III, undergoing elective primary total hip replacement were randomly allocated in three groups of 70 patients to receive either epidural anaesthesia (Group EA), general anaesthesia (GA), or epidural anaesthesia integrated with mild general anaesthesia (IA).

RESULTS

Data show a significant difference between the amount of pain measured by VRS immediately after surgery: prevalently absent in groups IA (84.3%) and EA (85.7%) and prevalently severe and moderate in group AG (34.3%). The measurement of the basic circulating erythrocyte mass in the first, third and fifth postoperative day, calculated by the Mercuriali formula, which considers blood loss, autologous and homologous transfusions and erythropoiesis, showed that general anaesthesia leads to a significant delay in the resumption of haemopoiesis. This result was attenuated by its combination with epidural anaesthesia.

CONCLUSIONS

On the basis of the literature and the results of our study, epidural anaesthesia seems to be the most appropriate technique for patients scheduled for total hip replacement: due to its simpler analgesic cover, its tendency to be associated with a lower incidence of complications in the first 24 hours after surgery. The incidence of relevant hypotension is minor compared to integrated anaesthesia. General anaesthesia produced a significant decrease in postoperative erythropoiesis.

Randomized comparison of remifentanil-propofol with a sciatic-femoral nerve block for out-patient knee arthroscopy

BACKGROUND AND OBJECTIVE

To evaluate preparation and discharge times as well as the anaesthesia-related costs of out-patient knee arthroscopy performed with a combined sciatic-femoral nerve block, or a propofol-remifentanil general anaesthetic.

METHODS

With Ethics Committee approval and written informed consent, 40 healthy patients were pre-medicated with intravenous midazolam (0.05 mg kg(-1)) and ketoprofen (50 mg). They were then randomly allocated to receive either a combined sciatic-femoral nerve block with 25 mL mepivacaine 2% (15 mL for the femoral nerve, 10 mL for the sciatic nerve) (PNB group, n = 20), or a general anaesthetic with a continuous intravenous infusion of remifentanil (0.1-0.3 microgkg(-1) min(-1)) and propofol (target plasma concentration 2-4 microg mL(-1)) with a laryngeal mask airway (GA group, n = 20).

RESULTS

The median (range) preparation time was 16 (10-28)min in the PNB group and 13 (8-22)min in the GA group (P = 0.015). Ten PNB patients were directly discharged to the day-surgery unit after the procedure as compared with one GA patient (P = 0.003). Discharge from the postanaesthesia care unit (PACU) required 5 (5-20) min in the PNB group and 23 (7-95) min in the GA group (P = 0.001). Home discharge criteria were fulfilled after 277 (150-485) min in the PNB group and 170 (100-400) min in the GA group (P = 0.005). Costs related to the time spent in the PACU were lower for the PNB group (1.10 euro, range Euro 0-22 euro) compared with the GA group (30 euro, range 0-176 euro) (P = 0.0005). There were no differences in total costs: PNB group 158 euro (range 105-194 euro) versus GA group 160 euro (range 101-238 euro) (P = 0.61).

CONCLUSIONS

In patients undergoing out-patient knee arthroscopy, the length of stay in the PACU can be shorter after a sciatic-femoral nerve block with a small volume of mepivacaine 2% compared with a propofol-remifentanil anaesthetic, and there is an increased likelihood that they will bypass the first phase of the postoperative recovery.

Unilateral spinal anesthesia. State of the art

The possibility to control the spread of intrathecal drugs, restricting the distribution of spinal block to the operated side is still controversial. Various authors reported that we can not predict the distribution of spinal block; however, other authors described how to restrict spinal block at the operated side in patients receiving surgical procedures involving one lower limb. Therefore, we reviewed clinical studies on this topic trying to outline the feasibility and potential clinical benefits of unilateral spinal anesthesia. The main results of studies recently published on peer reviewed journals concerning the clinical use of unilateral spinal anesthesia are reviewed. The main factors we must consider when attempting a unilateral spinal block are the use of small doses of local anesthetic solution injected through directional, pencil-point needles, together with a 15-20 min lateral decubitus position and the use of either hypo- or hyperbaric anesthetic solution. Using 6-8 mg of either hyper- or hypobaric bupivacaine provides a unilateral distribution of sympathetic and sensory blocks in 50 to 70% of patients, while unilateral motor block can be observed in up to 80% of cases. Attempting a unilateral spinal block results in a four-fold reduction in the incidence of clinically relevant hypotension with more stable cardiovascular parameters as compared with conventional bilateral spinal block. The small amount of local anesthetic solution injected, as well as the reduced extent of spinal block, also provide a favourable profile of the resolution of spinal block, which can be useful in the ambulatory setting. With simple technical skill we can reliably provide a preferential distribution of spinal block to the operated side. This results in a minimal delay in preparation time, but provides less hemodynamic side effects with higher cardiovascular stability, and increased autonomy after surgery with better patient acceptance.

Randomized comparison of isoflurane and sevoflurane for laparoscopic gastric banding in morbidly obese patients

STUDY OBJECTIVE

To compare the efficacy and recovery profile of sevoflurane and isoflurane as the main anesthetics for morbidly obese patients.

DESIGN

Randomized, blinded study.

SETTING

Inpatients.

PATIENTS

30 ASA physical status II and III obese patients [body mass index (BMI) > 35 kg/m(2)] undergoing laparoscopic gastric banding for morbid obesity.

INTERVENTIONS

After standard intravenous induction of general anesthesia and tracheal intubation, anesthesia was maintained with either sevoflurane or isoflurane as the main anesthetics. The end-tidal concentrations of the volatile drugs were adjusted to maintain systolic arterial blood pressure within +/-20% from baseline values. When the surgeon started the skin suture, the end-tidal concentration of the inhalational drug was reduced to 0.5 minimum alveolar concentration in both groups. At the last skin suture, the inhalational drug was discontinued and the vaporizator was removed to allow blinded evaluation of the emergence times.

MEASUREMENTS AND MAIN RESULTS

No differences in anesthetic exposure, hemodynamic parameters, incidence of untoward events, or postoperative pain relief were reported between the two groups. Extubation, emergence, and response times were shorter after sevoflurane [6 min (3-15 min), 8 min (5-18 min), and 12 (6-25 min)] than isoflurane [10 min (6-26 min), 14 min (6-21 min), and 21 min (14-41 min)] (p = 0.001, p = 0.03, and p = 0.0005, respectively). The median time for postanesthesia care unit discharge was 15 minutes (25th-75th percentiles: 10-18 min) after sevoflurane and 27 minutes (25th-75th percentiles: 20-30 min) after isoflurane (p = 0.0005).

CONCLUSIONS

Sevoflurane provides a safe and effective intraoperative control of cardiovascular homeostasis in morbidly obese patients undergoing laparoscopic gastric banding, with the advantage of a faster recovery and earlier discharge from the postanesthesia care unit than isoflurane.

Pattern of cardiovascular anomalies associated with esophageal atresia: support for a caudal pharyngeal arch neurocristopathy

Patients with cephalic neurocristopathy (an abnormality of neural crest differentiation) present a striking pattern of associated cardiovascular anomalies (CVA). Therefore, to support the hypothesis that esophageal atresia (EA) may be related to a defective contribution from the cephalic neural crest, we studied the pattern of CVA associated with EA. Medical records of 99 patients with isolated EA, 101 with isolated anorectal malformations (ARM) and 15 with both EA and ARM, consecutively admitted to our unit, were reviewed. The prevalence and pattern of CVA associated with isolated EA or isolated ARM were compared on the assumption that the cranial or caudal location of a major malformation is related to a different regional patterning of associated anomalies. The prevalence of CVA was 39% in patients with isolated EA and 7% in those with isolated ARM (p < 0.01). Neural crest-related CVA (aortic arch anomalies, conotruncal defects, and superior vena cava malformations) accounted for 72% of all CVA in patients with isolated EA versus 14% in those with isolated ARM (p < 0.02). In patients with isolated EA, anomalies of the fourth and sixth aortic arch derivatives accounted for 75% of all neural crest related CVA. The present pattern of CVA in infants with EA supports the concept that EA may be related to an abnormal contribution from caudal portion of cephalic neural crest.

A new posterior approach to the sciatic nerve block: a prospective, randomized comparison with the classic posterior approach

To evaluate the efficacy and acceptance of a new posterior subgluteus approach to the sciatic nerve, as compared with the classic posterior approach, 128 patients undergoing foot orthopedic procedures were randomly allocated to receive either the classic posterior sciatic nerve block (Group Labat, n = 64) or a modified subgluteus posterior approach (Group subgluteus, n = 64). All blocks were performed with the use of a nerve stimulator (stimulation frequency, 2 Hz; intensity, 1-0.5 mA). In Group subgluteus, a line was drawn from the greater trochanter to the ischial tuberosity; then, from the midpoint of this line, a second line was drawn perpendicularly and extended caudally for 4 cm. The end of this line represented the needle entry. In both groups, a proper sciatic stimulation was elicited at 0.5 mA; then 20 mL of 0.75% ropivacaine was injected. The time from needle insertion to successful sciatic nerve stimulation was 60 s (range, 10-180 s) with the Labat's approach and 32 s (range, 5-120 s) with the new subgluteus approach (P = 0.0005). The depth of appropriate sciatic stimulation was 45 +/- 13 mm (mean +/- SD) after 2 (range, 1-7) needle redirections in Group subgluteus and 67 +/- 12 mm after 4 (range, 1-10) needle redirections in Group Labat (P = 0.0001 and P = 0.00001, respectively). The failure rate was similar in both groups. Severe discomfort during the procedure was less frequent and acceptance better in Group subgluteus (5 patients [8%] and 60 patients [94%], respectively) than in Group Labat (20 patients [31%] and 49 patients [77%], respectively) (P = 0.0005 and P = 0.005, respectively). We conclude that this new subgluteus posterior approach to the sciatic nerve is an easy and reliable technique and can be considered an effective alternative to the more traditional Labat's approach.

IMPLICATIONS

Evaluating the efficacy and acceptance of a new approach to the sciatic nerve block, this prospective, randomized study demonstrated that the new subgluteus posterior approach is an easy and reliable technique and can be considered an useful alternative to the more traditional Labat's approach in patients undergoing foot surgery, facilitating the performance of the sciatic nerve blocks.

[Levobupivacaine for peripheral blocks of the lower limb: a clinical comparison with bupivacaine and ropivacaine]

BACKGROUND

The aim of this study was the comparison of clinical profile of sciatic nerve block performed with either 0,5% levobupivacaine, 0,5% bupivacaine, or 0,5% ropivacaine.

METHODS

With ethical committee approval and written informed consent 45 ASA physical status I-II patients, undergoing elective hallux valgus repair received intravenous premedication with midazolam (0,05 mg/kg) followed by femoral nerve block with 15 ml of 2% mepivacaine. Then patients were randomly allocated to receive a sciatic nerve block with 20 ml of either 0,5% levobupivacaine (n=15), 0,5% bupivacaine (n=15), or 0,5% ropivacaine (n=15). An independent blind observer evaluated the onset time and duration of nerve block and postoperative analgesia. Postoperative analgesia consisted of 100 mg IV ketoprofen every 8 hours with the first administration at request.

RESULTS

The onset time of sciatic nerve block was 15 (5-60) min with levobupivacaine, 30 (5-60) min with bupivacaine, and 15 (5-60) min with ropivacaine (P = NS). No differences in the quality of nerve block as well as in the nerve block resolution times were observed among the three groups. The duration of postoperative analgesia was 16 (8-24) hours with levobupivacaine, 14 (8-24) hours with bupivacaine, and 17 (8-24) hours with ropivacaine (P=NS).

CONCLUSIONS

Using 0,5% levobupivacaine for sciatic nerve block results in similar clinical effects as those produced by using the same volume and concentration of either bupivacaine or ropivacaine.

Ropivacaine

BACKGROUND

Ropivacaine is a relatively new long-acting local anesthetic. It is a pure S(-) isomer, with a high pKa and low lipid solubility. Because of its physical and chemical properties, ropivacaine produces a marked differential in sensory and motor blockades, with a toxic potential lower than other long-acting anesthetic solutions. The purpose of this paper was the evaluation of the literature concerning indications and advantages of ropivacaine for different regional anesthesia techniques.

METHODS

We have evaluated results of prospective, randomized, controlled trials evaluating clinical use of ropivacaine for epidural anesthesia and analgesia, as well as spinal and peripheral nerve blocks.

RESULTS

The literature clearly demonstrates both efficacy and safety of ropivacaine used for epidural anesthesia and analgesia as well as for upper and lower limb peripheral nerve blocks, both single-shot and continuous peripheral blocks. Although ropivacaine has not been registered yet for spinal anesthesia, various studies show its efficacy and safety also in this field. Because of its pharmacodynamic properties, intrathecal ropivacaine seems also interesting for outpatient procedures.

CONCLUSIONS

Ropivacaine is a long-acting local anesthetic with a marked differential blockade between sensory and motor fibres, overall at the low concentrations used for postoperative analgesia. It probably has a slightly lower potency as compared with bupivacaine, but provides similar clinical efficacy in the different fields of regional anesthesia. Ropivacaine is less cardiotoxic and causes less central nervous system toxicity than bupivacaine, and this lower toxic potential has been reported not only with equivalent but also with equipotent concentrations and doses. For this reason, ropivacaine represents a useful alternative to bupivacaine for central and peripheral nerve blocks as well as for the management of postoperative pain relief.

[Peripheral blocks for the lower limb: lumbar plexus]

BACKGROUND

The techniques of continuous peripheral blockades have shown to be efficient in postoperative pain control, in the various orthopaedic procedures of the limbs. The aim of this study is to evaluate the existing data about the use of a continuous blockade of the lumbar plexus or femoral nerve, together with the indications for technique and therapy.

METHODS

We considered the principal results of prospective, randomised studies described in literature about the assessment of a continuous peripheral blockade of the lumbar plexus or the femoral nerve in limb surgery. Furthermore we described the principal techniques for positioning the perinerval catheters in the considered sites, and the advised dosage regimen.

RESULTS

The various studies report an adequate costs/benefits relation concerning the used techniques. The analysed studies not only report an adequate efficacy of the postoperative pain control, but often show an important benefit in terms of functional recovery of the operated limbs and on final outcome of the patient.

CONCLUSIONS

The use of continuous blockades of the lumbar plexus or femoral nerve shows to be an important and effective instrument not only in terms of positive effects on postoperative pain control, but also in terms of relevant advantages concerning final outcome after surgery. Nevertheless these techniques should not be considered as the only approach to postoperative pain in the orthopaedic patient, but have to be included in a global, multidisciplinary and multimodal approach.

Continuous peripheral block in foot surgery

Peripheral neural blockade techniques are commonly used procedures to provide perioperative anesthesia and analgesia. Several continuous infusion catheter techniques have been described to extend the use of peripheral neural blockade into the postoperative period as an effective method of providing pain management. The analgesic benefit of continuous local anesthetic peripheral block in the management of postoperative pain is primarily related to the properties of providing intense analgesia thereby reducing perioperative opioid requirements and opioid-related side effects and promoting early recovery of postoperative activity. Continuous peripheral nerve blockade seems to be effective in allowing major foot and ankle surgery to be done particularly on an outpatient basis with greater pain relief. The sciatic nerve is the largest nerve in the body and it lies deep in the posterior thigh. According to its anatomy, the sciatic nerve can then be reached at different levels from the parasacral space to the popliteal fossa, ideally identifying a sciatic line running from the inferior border of the gluteus maximus muscle between the greater throcanter and the ischiatic tuberosity to the popliteal fossa. A variety of continuous peripheral blocks have been described in this paper including continuous sciatic block at several levels (para-sacral nerve block, subgluteal sciatic nerve block) and popliteal nerve block.

Implementing sevoflurane anesthesia with small doses opioid for upper abdominal surgery. Postoperative respiratory function after either remifentanil or fentanyl

BACKGROUND

The aim of this prospective, randomized study was to compare the effects on intraoperative cardiovascular homeostasis, recovery profile and postoperative oxygen saturation after sevoflurane anesthesia with small doses of either remifentanil or fentanyl in combination with postoperative epidural analgesia.

METHODS

With Ethical Committee approval and written patient consent, 30 ASA physical status I-II patients scheduled for elective upper abdominal surgery were randomly allocated to receive sevoflurane general anesthesia implemented with small doses of either remifentanil (n = 15) or fentanyl (n = 15), followed by postoperative epidural analgesia. Remifentanil group patients received a 1 mg kg-1 bolus infused during a 60 sec period followed by a 0.15 mg kg-1 min-1 infusion; while patients of Fentanyl group were given a 3 mg kg-1 initial dose followed by 50 mg boluses as requested (according to the time to peak effect of the two drugs, the initial dose was given 5 min before induction in Fentanyl group, and 1 min before induction in Remifentanil group). Postoperatively, oxygen saturation was continuously recorded and stored on a computer during the first 12 h after surgery. SpO2 decrease < 90% for more than one minute was considered as a minor respiratory complication.

RESULTS

The median sevoflurane's MAC-hour was 2.7 (1.4 - 4.9) in patients receiving remifentanil infusion and 4.1 (2.2 - 5.7) in those patients receiving fentanyl during surgery (P = 0.005). However, no differences in the recovery times were observed between the two groups. Similar pain relief was reported during coughing in the two studied groups at discharge from the recovery area and during the following study period. No major respiratory complication was observed throughout the study. Oxygen therapy was required in three patients of Fentanyl group only 20% (P = 0.22); however, 11 patients in the same group (73%) showed at least one minor respiratory complication (SpO2 < 90% for more than 1 min), with a median of 1 (range 0 - 12) episode per patient, compared with no episode in Remifentanil group (P = 0.0005).

CONCLUSIONS

Implementing sevoflurane anesthesia with very small remifentanil infusion provides a safe and effective hemodynamic control reducing sevoflurane consumption during the procedure, and produces less respiratory effects postoperatively as compared with intermittent bolus administration of fentanyl.

[Continuous brachial plexus blockade for shoulder surgery]

Continuous brachial plexus block is the technique of choice for postoperative shoulder pain treatment. The localization of the plexus is usually obtained drawing landmarks on the skin and using the electrical nerve stimulator; these and other different modalities are applied in order to reach safely and precisely nerve roots to be blocked with an anaesthetic solution. The Author presents a new anatomical perspective to guide the localization of the brachial plexus. It is shown how it is possible to detect the pathway of the brachial plexus from the cutaneous surface, linking between each other various landmarks: a) the apex of the scalene triangle, at the cross of a line leaving from the cricoid process and directed posterior to the posterior border of the sternocleidomastoid muscle, b) the midline of the clavicle c)the deltoid-pectoral sulcus d) the midpoint between the coracoid process and the chest profile e) the pulsation of the artery in the axylla. Following the guide of the so formed anesthetic line, is possible to place the needle, with a direction from distal to proximal, in a tangential route towards the interscalenic groove, thus allowing to perform a block of the plexus in a simple and efficacious way.

The effects of single or multiple injections on the volume of 0.5% ropivacaine required for femoral nerve blockade

We compared the effects of using a single- or multiple-injection technique on the volume of 0.5% ropivacaine required to block the femoral nerve, in a prospective, randomized, blinded fashion in which 50 premedicated patients received a femoral nerve block with 0.5% ropivacaine by use of a nerve stimulator and either a single- (n = 25) or multiple- (n = 25) injection technique. Muscular twitches were elicited at < or =0.5 mA before anesthetic injection. The designated volume of local anesthetic was equally divided among contraction of the vastus medialis, vastus intermedius, and vastus lateralis for the multiple injections, or it was injected at the contraction of the vastus intermedius with motion of the patella for the single injection. The local anesthetic volumes were varied for consecutive patients by using an up-and-down staircase method; a blinded observer determined the adequacy of nerve blockade (loss of pinprick sensation in the medial, patellar, and lateral portions of the knee, with concomitant block of the quadriceps muscle) 20 min after injection. The mean (95% confidence interval) volume required for blocking the femoral nerve with the multiple-injection technique (14 [12-16] mL) was significantly smaller than that observed with the single injection (23 [20-26] mL) (P = 0.001). According to logistic regression analyses, the 95% effective volumes of ropivacaine required to block the femoral nerve within 20 min after injection were 29 and 21 mL with a single or multiple injection, respectively. We conclude that searching for multiple muscular twitches reduces the volume of 0.5% ropivacaine required to produce blockade of the femoral nerve.

IMPLICATIONS

We evaluated the effects of using a single- or multiple-injection technique on the volume of 0.5% ropivacaine required to block the femoral nerve. The 95%effective concentration values for producing the same degree of sensory and motor blockade of the femoral nerve within 20 min after injection were 29 mL after elicitation of a patella twitch and 21 mL when the three main branches of the femoral nerve were identified, potentially leading to an important benefit for patients receiving peripheral nerve blocks.

The minimum effective dose of 0.5% hyperbaric spinal bupivacaine for cesarean section

BACKGROUND

The aim of this prospective, blind study was to determine the minimum effective dose of hyperbaric bupivacaine required for cesarean section.

METHODS

With Ethical Committee approval and written consent, 24 healthy women undergoing elective cesarean section received a combined spinal epidural anesthesia. We sought to determine the minimum effective dose of spinal bupivacaine using a staircase method. In each patient an arbitrary dose of 0.5% hyperbaric bupivacaine in relation to patient height was used. The initial dose was 0.075 mg/cm height, while the outcome of each patient's response determined the dose for the subsequent patient. When successful spinal block (sensory level = or < T4 with complete motor blockade) was achieved within 20 min from spinal injection, the dose of spinal bupivacaine for the next patient was decreased by 0.01 mg/cm height. Conversely, when successful spinal block was not observed, the dose of spinal bupivacaine for the next patient was increased by 0.01 mg/cm height. Sensory and motor blocks were evaluated every 5 min by an independent, blinded observer. If successful spinal block was not achieved within the designed period, a 5-8 ml epidural bolus of 2% lidocaine was given to achieve adequate surgical anesthesia.

RESULTS

No complications were reported during the study, and all women delivered their baby uneventfully (APGAR scores 5 min after delivery ranged from 9 to 10) within 5 min from uterus incision. The duration of surgical procedure ranged from 30 to 48 minutes. The dose of hyperbaric bupivacaine providing adequate surgical anesthesia within 20 min from spinal injection in 50% of subjects was 0.036 mg/cm height (95% confidence intervals: 0.031-0.041 mg/cm height). The ED95 calculated from the probit transformation to provide effective spinal anesthesia for cesarean section was 0.06 mg/cm height.

CONCLUSIONS

This prospective, blind study demonstrated that a dose as low as 0.06 mg/cm height represents the dose of intrathecal bupivacaine providing effective spinal block in 95% of women undergoing elective cesarean section.

Improving postoperative analgesia after axillary brachial plexus anesthesia with 0.75% ropivacaine. A double-blind evaluation of adding clonidine

BACKGROUND

The aim of this prospective, randomized, double-blind study was to evaluate the effects of adding 1 microg/kg clonidine to 20 ml of ropivacaine 0.75% for axillary brachial plexus anesthesia.

METHODS

With Ethical Committee approval and written consent, 30 ASA physical status I-II in-patients, undergoing upper extremity orthopedic procedures were randomly allocated to receive axillary brachial plexus block with 20 ml of 0.75% ropivacaine alone (group ropivacaine, n = 15) or 0.75% ropivacaine + 1 microg/kg clonidine (group ropivacaine-clonidine, n = 15). Nerve blocks were placed using a nerve stimulator with the multiple injection technique (stimulation frequency was 2 Hz; stimulation intensity was decreased to < or = 0.5 mA after each muscular twitch; the anesthetic volume was equally divided among arm flexion, arm extension, wrist flexion, and thumb adduction). A blinded observer recorded the time required to achieve surgical block [loss of pinprick sensation in the innervation areas of the hand (C6-C8) with concomitant inability to move the wrist and hand] and first analgesic request.

RESULTS

No differences in demography, degree of sedation, peripheral oxygen saturation, and hemodynamic variables were observed between the two groups. Readiness for surgery required 15 min (5-36 min) with 0.75% ropivacaine and 20 min (5-30 min) with the ropivacaine-clonidine mixture. The degree of pain measured at first analgesic request, and consumption of postoperative analgesics were similar in the two groups; while first postoperative analgesic request occurred after 13.8 h (25th-75th percentiles: 9.1-13 h) in the ropivacaine group and 15.2 h (25th-75th percentiles: 10.7-16 h) in the ropivacaine-clonidine group (p = 0.04).

CONCLUSIONS

Adding 1 microg/kg clonidine to 20 ml of ropivacaine 0.75% for axillary brachial plexus anesthesia provided a 3 h delay in first analgesic request postoperatively, without clinically relevant effects on the degree of sedation and cardiovascular homeostasis.

Fentanyl does not improve the nerve block characteristics of axillary brachial plexus anaesthesia performed with ropivacaine

BACKGROUND

The aim of this prospective, randomized, double-blind study was to evaluate the effects of adding 1 microg. kg-1 fentanyl to ropivacaine 7.5 mg. ml-1 for axillary brachial plexus anaesthesia.

METHODS

With Ethics Committee approval and written consent, 30 ASA physical status I-II in-patients, scheduled for orthopaedic hand procedures were randomly allocated to receive axillary brachial plexus block with 20 ml of either ropivacaine 7.5 mg. ml-1 (n=15) or ropivacaine 7.5 mg. ml-1+1 microg. ml-1 fentanyl (n=15). Nerve blocks were placed using a nerve stimulator with the multiple injection technique. A blinded observer recorded the time to onset of surgical block (loss of pinprick sensation in the innervation areas of the hand (C6-C8) with concomitant inability to flex the wrist against gravity and move the fingers when squeezing the hand) and first request for pain medication after surgery.

RESULTS

No differences in demography, degree of sedation or peripheral oxygen saturation were observed between the two groups. Median (range) time required to achieve readiness for surgery was 15 min (5-36 min) with ropivacaine alone and 15 min (5-40 min) with the ropivacaine-fentanyl mixture. No differences in the intraoperative quality of nerve block were reported between the two groups. Four patients receiving ropivacaine plain and two patients receiving the ropivacaine-fentanyl mixture did not require analgesics during the first 24 h after surgery (P=0.62). The degree of pain experienced at first analgesic request in those patients asking for pain medication, as well as median consumption of postoperative analgesics, were similar in the two groups. First postoperative analgesic request was made at 11 h (25th-75th percentiles: 9.1-14 h) in patients receiving ropivacaine alone and at 11.8 h (25th-75th percentiles: 9.8-15 h) in patients receiving the ropivacaine-fentanyl mixture (P=0.99).

CONCLUSION

The addition of fentanyl 1 microg. ml-1 to ropivacaine 7.5 mg. ml-1 does not improve the nerve block characteristics of axillary brachial plexus anaesthesia for orthopaedic procedures involving the hand.

End tidal carbon dioxide monitoring in spontaneously breathing, nonintubated patients. A clinical comparison between conventional sidestream and microstream capnometers

BACKGROUND

To evaluate the end tidal carbon dioxide estimation in nonintubated, spontaneously breathing patients using either conventional sidestream or microstream capnometers.

METHODS

Patients received a regional anesthesia technique, while the end tidal carbon dioxide partial pressure (EtCO2) was sampled through a nasal cannula (Nasal FilterLine, Nellcor, Plesanton, CA, USA) and measured using either a conventional sidestream capnometer with a 200 ml.min-1 aspiration flow rate, or a microstream capnometer (NBP-75, Nellcor Puritan Bennett, Plesanton, CA, USA) with an aspiration flow rate of 30 ml.min-1. After a 20 min period with stable hemodynamic variables (systolic arterial blood pressure within +/- 20% from baseline values), the EtCO2 was randomly recorded using one of the two capnometer while arterial blood was simultaneously drawn from the radial artery and analyzed for measurement of arterial CO2 partial pressure. Afterwards the nasal cannula was connected to the other capnometer and the procedure repeated. Both the capnometer and arterial blood gas analyzer were calibrated before each studied patient according to the manufacturer instructions. The same procedure was repeated at least two times in each patient.

RESULTS

A total of 120 pairs of EtCO2 and PaCO2 measurements were drawn from 30 adults (age: 69 +/- 5 years; weight: 70 +/- 10 kg; height: 160 +/- 10 cm): 60 using the conventional sidestream capnometer and 60 with the microstream one. The median arterial to end tidal CO2 tension difference was 4.4 mmHg (range: 0.28 mmHg) with the microstream capnometer and 7 mm Hg (range: 0-22 mmHg) with the conventional capnometer (p = 0.02).

CONCLUSION

The microstream capnometer provides a more accurate end tidal CO2 partial pressure measurement in nonintubated, spontaneously breathing patients than conventional sidestream capnometers, allowing for adequate monitoring of the respiratory function in nonintubated patients.

Small doses of remifentanil or sufentanil for blunting cardiovascular changes induced by tracheal intubation: a double-blind comparison

BACKGROUND AND OBJECTIVE

To compare the effects on cardiovascular changes induced by tracheal intubation when small doses of either remifentanil or sufentanil are used in the presence of midazolam.

METHODS

Thirty normotensive, ASA physical status I-II patients, receiving general anaesthesia for major abdominal surgery, received an intravenous midazolam premedication (0.05 mg kg-1) 10 min before induction. They were randomly allocated to receive in a double-blind fashion an intravenous bolus of either (a) remifentanil given as a bolus dose 1 microgram kg-1 (n = 15), or else (b) sufentanil 0.1 microgram kg-1 infused over 60 s (n = 15). In each instance this loading dose was followed by a continuous intravenous infusion (0.1 microgram kg-1 min-1 or 0.01 microgram kg-1 min-1 of remifentanil or sufentanil, respectively). General anaesthesia was induced with propofol (2 mg kg-1), followed by atracurium besilate (0.5 mg kg-1) to facilitate tracheal intubation. Following intubation, the lungs were mechanically ventilated with a 60% nitrous oxide in oxygen mixture and a 1% inspired sevoflurane.

RESULTS

Arterial pressure and heart rate were recorded before induction of anaesthesia (baseline), immediately before intubation, immediately after tracheal intubation and every minute for the first five minutes thereafter. No differences in systolic and diastolic arterial pressures were observed between the two groups. At the end of the study period, systolic and diastolic pressures slightly decreased from preinduction values in both groups. Four patients in the remifentanil group (26%) and five patients in sufentanil group (33%) showed at least one systolic pressure value < 90 mmHg during the study period (P = not significant); however, the observed decreases in systolic pressure were transient and did not require treatment. Heart rate values were not affected by tracheal intubation in either group.

CONCLUSIONS

In healthy normotensive patients without cardiovascular disease the use of a relatively small dose of either remifentanil or sufentanil after standard midazolam premedication results in a similar and clinically acceptable effectiveness in blunting the cardiovascular changes induced by tracheal intubation.

Minimum local anesthetic volume blocking the femoral nerve in 50% of cases: a double-blinded comparison between 0.5% ropivacaine and 0.5% bupivacaine

Recent studies demonstrated that ropivacaine was nearly 40% less potent than bupivacaine in the first stage of labor, but contrasting results have been reported. We, therefore, conducted a prospective, randomized, double-blinded study to determine the effects of the ropivacaine/bupivacaine potency ratio on the minimum volume of local anesthetic required to produce effective block of the femoral nerve in 50% of patients. Fifty adults premedicated with IV midazolam, 0.05 mg/kg, undergoing elective knee arthroscopy received femoral nerve blocks with a multiple-injection technique with a nerve stimulator (contractions of vastus medialis, vastus intermedius, and vastus lateralis were elicited with a 0.5-mA stimulating current). Patients randomly received either 0.5% ropivacaine (n = 25) or 0.5% bupivacaine (n = 25). The anesthetic volume was decided according to Dixon's up-and-down method, starting from 12 mL and being equally divided among the three elicited twitches. Successful nerve block was loss of pinprick sensation in the femoral nerve distribution with concomitant block of the quadriceps muscle within 20 min after injection, as assessed by a blinded observer. Positive or negative responses determined a 3-mL decrease or increase for the next patient, respectively. According to the up-and-down sequences, the minimum local anesthetic volume providing successful nerve block in 50% of cases was 14 +/- 2 mL in the ropivacaine group (95% CI: 12-16 mL) and 15 +/- 2 mL (95% CI: 13-17 mL) in the bupivacaine group (P: = 0.155). We conclude that the volume of 0.5% ropivacaine required to produce effective block of the femoral nerve in 50% of patients is similar to that required when using 0.5% bupivacaine.

IMPLICATIONS

Considering the risk for drug-related systemic toxicity, the equipotency ratio between ropivacaine and bupivacaine is crucial for daily practice. Despite the 40% reduction in the analgesic potency of ropivacaine reported during epidural analgesia for labor pain, results of this prospective, randomized, double-blinded study demonstrated that the same volume of 0.5% ropivacaine or 0.5% bupivacaine is required to produce an effective block of the femoral nerve in 50% of cases.

Interscalene brachial plexus anaesthesia with small volumes of ropivacaine 0.75%: effects of the injection technique on the onset time of nerve blockade

BACKGROUND AND AIM

We evaluated the effect of the injection technique on the onset time and efficacy of interscalene brachial plexus anaesthesia.

METHODS

With Ethical Committee approval and written consent, 30 patients undergoing elective shoulder acromioplasty or capsuloplasty were randomly allocated to receive interscalene brachial plexus block with 20 mL of ropivacaine 0.75% by using either a single injection (Single group, n = 15) or multiple injection (Multiple group, n = 15). Nerve blocks were placed with the aid of a nerve stimulator using short bevelled, Teflon coated needles. The stimulation frequency was set at 2 Hz and the intensity of stimulating current, initially set at 1 mA, was gradually decreased to < or = 0.5 mA after each muscular twitch was observed. In the Single group, the anaesthetic solution was slowly injected after the first muscular twitch had been observed. In the Multiple group, 8 mL were injected at shoulder abduction, 6 mL were injected at arm flexion, and 6 mL at the extension of the arm.

RESULTS

Placing the block required 5 min (4-8 min) in the Multiple group and 3 min (1-10 min) in the Single group (P = 0.001); however, total preoperative time (from skin disinfection to complete loss of pinprick sensation from C4 to C7 with inability to elevate the limb from the operating table) was shorter in the Multiple group (15 min; range 10-28 min) than in the Single group (23 min; range 14-60 min) (P = 0.03). Additional intravenous fentanyl supplementation was required in two patients of the Multiple group (13%) and eight patients of the Single group (53%) (P = 0.05).

CONCLUSION

We conclude that using a multiple injection technique shortened the preparation time and improved the quality of interscalene brachial plexus anaesthesia performed with small volumes of ropivacaine 0.75%.

Italian experience with the cuffed oropharyngeal airway (COPA). A prospective, observational study

BACKGROUND

The cuffed oropharyngeal airway (COPA) has been recently introduced into the market, but few is known about its clinical use in Italy. We therefore conducted a prospective, observational investigation to evaluate the use of this new extra-tracheal airway in clinical practice.

METHODS

Anesthesiologists participating in the study received a simple questionnaire where data concerning anthropometric variables, surgical procedure, type and doses of drugs used to induce and maintain general anesthesia, type of ventilation during the procedure, and occurrence of untoward events during either COPA placement, general anesthesia maintenance, or postoperative period were prospectively recorded. The number of previously placed COPA, and the adequacy of airway control (subjective four point scale: excellent, good, fair, and poor) were also assessed.

RESULTS

A total of 210 patients (139 female and 71 male) were prospectively studied. General anesthesia was induced with propofol in 204 patients (98%), sodium thiopental in 3 patients (1.5%), and midazolam in 1 patient (0.5%); while only one patient received muscle relaxants (0.5%); 126 patients (64%) were spontaneously breathing while 71 patients (36%) received positive pressure mechanical ventilation. No differences in the incidence of untoward events was reported between spontaneously breathing and mechanically ventilated patients. No differences in the incidence of untoward events were reported according to the number of previously placed COPA. Difficulties in COPA placement were reported in 7 patients with normal dentiture (5%) and 9 patients (39%) with dental prosthesis (p = 0.003), (Odds Ratio: 5.1; Cl95%: 3.0-8.7). Furthermore, airway obstruction was more frequently reported in patients with dental prosthesis (8% vs 0%; p = 0.002). The seal pressure was higher in mechanically ventilated (17 +/- 10 cm H2O) than spontaneously breathing patients (10 +/- 8 cm H2O), (p = 0.0005), while a sealing pressure higher than 12 cm H2O was associated with an increased risk for postoperative sore throat (Odds ratio: 4.3; Cl95%: 2.6-7.1; p = 0.002). Airway control was graded as excellent in 61.4% of cases by physician previously placing more than 50 COPA, compared with only 26.5% when less than 50 COPA had been previously placed (p = 0.0005).

CONCLUSIONS

COPA provided as safe and effective airway management in mechanically ventilated patients as that observed during spontaneous breathing. Experience with COPA placement had no effects on the placement success rate or incidence of untoward events, but improved the quality of airway control.

A comparison of remifentanil and sufentanil as adjuvants during sevoflurane anesthesia with epidural analgesia for upper abdominal surgery: effects on postoperative recovery and respiratory function

We compared the recovery profile and postoperative SpO(2) after the administration of general anesthesia with either sevoflurane-remifentanil or sevoflurane-sufentanil in 30 healthy patients undergoing upper abdominal surgery. They were randomly allocated to receive general anesthesia with sevoflurane and small doses of either remifentanil (n = 15) or sufentanil (n = 15), followed by postoperative epidural analgesia. The median sevoflurane minimum alveolar anesthetic concentration-hour was 2.3 (1.2-6.3) in group Remifentanil and 2.6 (1.4-5.2) in group Sufentanil (P: = 0.39), while the median consumption of remifentanil was 1.3 mg (0.7-3.4 mg) and sufentanil 0.09 mg (0.05-0.6 mg). Tracheal extubation required 10 min (6-18 min) with remifentanil and 14 min (8-24 min) with sufentanil (P: = 0.05); however, no differences in time to discharge from the recovery area were reported (24 min [12-75 min] with remifentanil and 30 min [12-135 min] with sufentanil; P: = 0. 35). From the first to seventh hour after surgery, SpO(2) was decreased more in the sufentanil than in the remifentanil group (P: = 0.001), and seven patients in the sufentanil group showed at least one episode with SpO(2) < or = 90% for more than 1 min (P: = 0.006) (median: 1 episode; range: 0-17 episodes; P: = 0.003). When added to sevoflurane, remifentanil is as effective as sufentanil during the intraoperative period, but provides shorter time to tracheal extubation and fewer effects on postoperative SpO(2) in the first 7 h after surgery.

IMPLICATIONS

In this double-blinded study, we evaluated the effects of adding small infusions of either remifentanil or sufentanil to sevoflurane in combination with postoperative epidural analgesia for upper abdominal surgery. We demonstrated that remifentanil is as effective as sufentanil during the intraoperative period, but that it provides shorter time to extubation and fewer effects on postoperative SpO(2) in the first 7 h after surgery.