An in-depth analysis of the polyvagal theory in light of current findings in neuroscience and clinical research.

The polyvagal theory has led to the understanding of the functions of the autonomic nervous system in biological development in humans, since the vagal system, a key structure within the polyvagal theory, plays a significant role in addressing challenges of the mother-child dyad. This article aims to summarize the neurobiological aspects of the polyvagal theory, highlighting some of its strengths and limitations through the lens of new evidence emerging in several research fields-including comparative anatomy, embryology, epigenetics, psychology, and neuroscience-in the 25 years since the theory's inception. Rereading and incorporating the polyvagal idea in light of modern scientific findings helps to interpret the role of the vagus nerve through the temporal dimension (beginning with intrauterine life) and spatial dimension (due to the numerous connections of the vagus with various structures and systems) in the achievement and maintenance of biopsychosocial well-being, from the uterus to adulthood.

Adding clonidine to the induction bolus and postoperative infusion during continuous femoral nerve block delays recovery of motor function after total knee arthroplasty.

We evaluated the effects of adding clonidine for continuous peripheral nerve infusions. Sixty patients undergoing total knee arthroplasty under combined single-injection sciatic block and continuous femoral infusion were randomly allocated to three groups: block induction with 0.75% ropivacaine followed by 0.2% ropivacaine (group control; n = 20); block induction with 0.75% ropivacaine and 1 microg/kg clonidine followed by 0.2% ropivacaine (group cloni-bolus; n = 20), and block induction with 0.75% ropivacaine and 1 microg/kg clonidine followed by 0.2% ropivacaine with 1 microg/mL clonidine (group cloni-infusion; n = 20). After surgery, continuous femoral infusion was provided with a patient-controlled infusion pump (basal infusion rate, 6 mL/h; incremental dose, 2 mL; lockout time, 15 min). The median (range) onset time of surgical block was 15 min (5-30 min) in group control, 10 min (5-35 min) in group cloni-bolus, and 10 min (5-30 min) in group cloni-infusion (P = 0.07). No differences were reported among groups in the degree of pain measured with the visual analog scale. The total consumption of local anesthetic solution after a 24-h infusion was 170 mL (144-220 mL) in group control, 169 mL (144-260 mL) in group cloni-bolus, and 164 mL (144-248 mL) in group cloni-infusion (P = 0.51); after the second day of infusion, total consumption was 168 mL (144-200 mL) in group control, 156 mL (144-288 mL) in group cloni-bolus, and 150 mL (144-210 mL) in group cloni-infusion (P = 0.48). Hemodynamic profiles and sedation were similar in the three groups. Motor function impairment after 48 h of infusion was observed in 27% of cloni-infusion patients but in only 6% of both the control and cloni-bolus groups (P = 0.05). We conclude that adding clonidine 1 microg/mL to local anesthetic for continuous femoral nerve block does not improve the quality of pain relief but has the potential for delaying recovery of motor function.

A prospective, randomized, double-blind comparison of unilateral spinal anesthesia with hyperbaric bupivacaine, ropivacaine, or levobupivacaine for inguinal herniorrhaphy.

In 60 patients undergoing inguinal hernia repair, we compared the clinical profile of unilateral spinal anesthesia produced with either 8 mg of hyperbaric bupivacaine 0.5% (n = 20), 8 mg of hyperbaric levobupivacaine 0.5% (n = 20), or 12 mg of hyperbaric ropivacaine 0.5% (n = 20). The study drug was injected slowly through a 25-gauge Whitacre directional needle and patients maintained the lateral decubitus position for 15 min. The onset time and intraoperative efficacy were similar in the three groups. The maximal level of sensory block on the operative and nonoperative sides was T6 (T12-5) and L3 (/[no sensory level detectable]-T4) with bupivacaine, T8 (T12-5) and L3 (/-T3) with levobupivacaine, T5 (T10-2) and T11 (/-T3) with ropivacaine (P = 0.11, P = 0.23, respectively). Complete regression of spinal anesthesia occurred after 166 +/- 42 min with ropivacaine, 210 +/- 63 min with levobupivacaine, and 190 +/- 51 min with bupivacaine (P = 0.03 and P = 0.04, respectively); however, no differences were observed in time for home discharge (329 +/- 89 min with bupivacaine, 261 +/- 112 min with levobupivacaine, and 332 +/- 57 min with ropivacaine [P = 0.28]). We conclude that 8 mg of levobupivacaine or 12 mg of ropivacaine are acceptable alternatives to 8 mg of bupivacaine when limiting spinal block at the operative side for inguinal hernia repair.

Cardiovascular changes after extraglottic airway insertion: a prospective, randomized comparison between the laryngeal mask or the new PAXpress.

STUDY OBJECTIVE: To compare hemodynamic responses induced with the new extraglottic airway, PAXpress, and the classic Laryngeal Mask Airway (LMA). DESIGN: Prospective, randomized study. SETTING: Anesthesia department of a university teaching hospital. PATIENTS: 70 ASA physical status I and II patients, aged 18 to 65 years, scheduled to receive general anesthesia for extraabdominal procedures of short duration. INTERVENTIONS: Patients were randomly allocated to receive either a LMA (n = 35) or a PAXpress (n = 35) placement. After midazolam premedication (0.05 mg kg-1) and general anesthesia induction (propofol 2.5 mg kg-1, and fentanyl 1 microg kg-1) the airways were placed according to manufacturer instructions; then general anesthesia was maintained with a 2% sevoflurane concentration and an air/oxygen mixture. MEASUREMENTS AND MAIN RESULTS: Arterial blood pressure [both systolic (SBP) and diastolic (DBP)] and heart rate (HR) values were recorded immediately before airway placement, immediately after airway placement, then every 1 minute during the first 5 minutes. During the first 5 minutes after airway insertion, both SBP and DBP values were higher with the PAXpress than the LMA (repeated measures analysis of variance:p = 0.02 and p = 0.006, respectively), whereas no differences were reported in HR values. Also, the maximum percentage increase in both SBP and DBP values was larger with PAXpress [+19% (range: -19% to +80%) for SBP and +26% (range: -17% to +96%) for DBP] than the LMA [+9% (range: -30% to +90%) for SBP and +10% (range: -30% to +92%) for DBP] (p = 0.006 and p = 0.001, respectively). CONCLUSIONS: Although further studies are required to evaluate safety and airway trauma of this new extraglottic airway, placing the PAXpress produces more marked changes in hemodynamic variables as compared with those produced by the LMA.

Levobupivacaine 0.2% or 0.125% for continuous sciatic nerve block: a prospective, randomized, double-blind comparison with 0.2% ropivacaine.

In 60 patients receiving elective hallux valgus repair, we compared the efficacy of continuous popliteal sciatic nerve block produced with 0.2% ropivacaine (n = 20), 0.2% levobupivacaine (n = 20), or 0.125% levobupivacaine (n = 20) infused with a patient-controlled system starting 3 h after a 30-mL bolus of the 0.5% concentration of the study drug and for 48 h (baseline infusion rate, 6 mL/h; incremental dose, 2 mL; lockout time, 15 min; maximum incremental doses per hour, 3). No differences were reported in the intraoperative efficacy of the nerve block. The degree of pain was similar in the three groups throughout the study period, both at rest and during motion. Total consumption of local anesthetic solution during the first 24 h was 148 mL (range, 144-228 mL) with 0.2% ropivacaine, 150 mL (range, 144-200 mL) with 0.2% levobupivacaine, and 148 mL (range, 144-164 mL) with 0.125% levobupivacaine (P = 0.59). The volume of local anesthetic consumed during the second postoperative day was 150 mL (range, 144-164 mL) with 0.2% ropivacaine, 154 mL (range, 144-176 mL) with 0.2% levobupivacaine, and 151 mL (range, 144-216 mL) with 0.125% levobupivacaine (P = 0.14). A smaller proportion of patients receiving 0.2% levobupivacaine showed complete recovery of foot motor function as compared with 0.2% ropivacaine and 0.125% levobupivacaine, both at 24 h (35% vs 85% and 95%; P = 0.0005) and at 48 h (60% vs 100% and 100%; P = 0.001). We conclude that sciatic infusion with both 0.125% and 0.2% levobupivacaine provides adequate postoperative analgesia after hallux valgus repair, clinically similar to that provided by 0.2% ropivacaine; however, the 0.125% concentration is preferred if early mobilization of the operated foot is required.

Interscalene brachial plexus anesthesia and analgesia for open shoulder surgery: a randomized, double-blinded comparison between levobupivacaine and ropivacaine.

UNLABELLED: We compared the onset time and quality of interscalene brachial plexus block produced with levobupivacaine and ropivacaine in 50 patients undergoing open shoulder surgery randomly allocated to receive 30 mL of 0.5% levobupivacaine (n = 25) or 0.5% ropivacaine (n = 25) injected through a 20-gauge catheter placed into the interscalene sheath using a 18-gauge insulated and stimulating Tuohy introducer. The block was also prolonged after surgery using a patient-controlled interscalene analgesia with 0.125% levobupivacaine or 0.2% ropivacaine, respectively (basal infusion rate, 6 mL/h; bolus, 2 mL; lockout period, 15 min; maximum boluses per hour, three). Three patients (two with levobupivacaine [8%] and one with ropivacaine [4%]) failed to achieve surgical block within 45 min after the injection and were excluded. The onset time of surgical block was 20 min (10-40 min) with levobupivacaine and 20 min (5-45 min) with ropivacaine (P = 0.53). Rescue intraoperative analgesia (0.1 mg of fentanyl IV) was required in eight patients in each group (34%) (P = 0.99). Forty-two patients completed the 24-h postoperative infusion (22 with levobupivacaine and 20 with ropivacaine). Postoperative analgesia was similarly effective in both groups. Total consumption of local anesthetic infused during the first 24 h was 147 mL (144-196 mL) with levobupivacaine and 162 mL (144-248 mL) with ropivacaine (P = 0.019), with a ratio between boluses received and requested of 0.8 (0.4-1.0) and 0.7 (0.4-1.0), respectively (P = 0.004). The degree of motor block of the operated limb was deeper with levobupivacaine than ropivacaine when starting postoperative analgesia; however, no further differences in degree of motor function were observed between the two groups. We conclude that 30 mL of levobupivacaine 0.5% induces an interscalene brachial plexus anesthesia of similar onset and intensity as the one produced by the same volume and concentration of ropivacaine. Postoperative interscalene analgesia with 0.125% levobupivacaine results in similar pain relief and recovery of motor function with less volume of local anesthetic than with 0.2% ropivacaine. IMPLICATIONS: This prospective, randomized, double-blinded study demonstrates that 30 mL of 0.5% levobupivacaine produces an interscalene brachial plexus block of similar onset and quality as the one produced by the same volume of 0.5% ropivacaine. When prolonging the block after surgery, 0.125% levobupivacaine provides adequate pain relief and recovery of motor function after open shoulder surgery, with less volume infused during the first 24 h after surgery than 0.2% ropivacaine.

Intrathecal anesthesia.

PURPOSE OF REVIEW: Development of new drugs and special techniques, as well as changes in health care organization have markedly influenced the use of spinal block and its indications. The present review overviews recent developments in local anesthetic drugs, side effects and special techniques for intrathecal anesthesia. RECENT FINDINGS: Severe complications after spinal anesthesia are acceptably rare. The cardiovascular effects associated with sympathetic block are more frequent but may successfully be treated with volume expansion and administration of vasoactive drugs while the multimodal approach to prevention of such side effects can also reduce the incidence. Based on recent magnetic resonance imaging studies the volume of cerebrospinal fluid at the lumbosacral level is the main determinant of the effects produced by intrathecal injection of local anesthetic solutions. Unfortunately, it is not possible to estimate the volume of cerebrospinal fluid at the lumbosacral region in clinical practice, but it is clear that the total dose of local anesthetic injected into the subarachnoid space is the primary determinant of both therapeutic and unwanted effects of spinal anesthesia. There is overwhelming evidence of the potential risk for neurological dysfunction associated with spinal lidocaine. This evidence is even more relevant in outpatients, in whom lidocaine is primarily indicated. On the other hand, several studies have demonstrated the efficacy and safety of using small doses of long-acting agents, such as bupivacaine or ropivacaine, to produce a short spinal block. The addition of small doses of opioids further helps to minimize the dose of local anesthetic solution required, without affecting the recovery profile from spinal block. The extensive use of pencil-point designs for spinal needles, and the availability of needles of very small size have allowed a significant reduction in the incidence of postdural puncture headache. SUMMARY: The changes in health care organization observed during the past few years have forced us to change the indications for and clinical uses of intrathecal anesthesia techniques in accordance with the changing needs of surgery. The development of new drugs and special techniques for spinal anesthesia will further improve the clinical use of this old but trusted technique.