Peripheral nerve blocks (PNBs) have an increasingly important role in ambulatory anesthesia and have many characteristics of the ideal outpatient anesthetic: surgical anesthesia, prolonged ...postoperative analgesia, and facilitated discharge. Critically evaluating the potential benefits and supporting evidence is essential to appropriate technique selection. When PNBs are used for upper extremity procedures, there is consistent opioid sparing and fewer treatment-related side effects when compared with general anesthesia. This has been demonstrated in the immediate perioperative period but has not been extensively investigated after discharge. Lower extremity PNBs are particularly useful for procedures resulting in greater tissue trauma when the benefits of dense analgesia appear to be magnified, as evidenced by less hospital readmission. The majority of current studies do not support the concept that a patient will have difficulty coping with pain when their block resolves at home. Initial investigations of outpatient continuous peripheral nerve blocks demonstrate analgesic potential beyond that obtained with single-injection blocks and offer promise for extending the duration of postoperative analgesia. The encouraging results of these studies will have to be balanced with the resources needed to safely manage catheters at home. Despite supportive data for ambulatory PNBs, most studies have been either case series or relatively small prospective trials, with a narrow focus on analgesia, opioids, and immediate side effects. Ultimately, having larger prospective data with a broader focus on outcome benefits would be more persuasive for anesthesiologists to perform procedures that are still viewed by many as technically challenging.
Novel anesthetic and analgesic agents are currently under development or investigation to improve anesthetic delivery and patient care. The pharmacokinetic and analgesic profiles of these agents are ...especially tailored to meet the challenges of rapid recovery and opioid minimization associated with ambulatory anesthesia practice.
Clonal cell lines of rat embryonic hippocampal origin have been developed by using retroviral transduction of temperature-sensitive simian virus 40 large tumor antigens. The cell lines undergo ...morphological differentiation at the nonpermissive temperature and in response to differentiating agents. Immunocytochemical analysis indicates that various lines are derived from progenitors of neuronal, glial, and bipotential lineages. Selected neuronal lines differentiate in response to diffusible factors released by primary glia, and one line of glial lineage supports the maturation of primary neurons in culture. Selected cell lines exhibit different patterns of neurotrophin gene expression that change after differentiation. In some lines, the relative levels of neurotrophin 3 and brain-derived neurotrophic factor message expression may reflect the developmental or regional differential expression seen for these genes in the hippocampus in situ. These hippocampal cell lines, which express markers indicative of commitment to neuronal or glial lineages, are valuable for studies of development and plasticity in these lineages, as well as for studies of the regulation of neural trophic interactions.
In a growing outpatient surgical population, postdischarge nausea and vomiting (PDNV) is unfortunately a common and costly anesthetic complication. Identification of risk factors for both ...postoperative nausea and vomiting and PDNV is the hallmark of prevention and management. New pharmacologic interventions with extended duration of action, including palonosetron and aprepritant, may prove to be more efficacious.
Lumbar-plexus and sciatic-nerve blocks are commonly combined for lower-extremity anesthesia using large doses of ropivacaine. Limited information is available about the pharmacokinetics of this ...practice. We analyzed plasma ropivacaine concentrations after single-injection lumbar-plexus blocks with and without sciatic-nerve blocks.
Twenty patients having lower-extremity surgery using a lumbar-plexus block with 0.5% ropivacaine with 1:400,000 epinephrine (35 mL, n = 10) or the same lumbar-plexus block with the addition of a sciatic-nerve block (25 mL, n = 10, 60 mL total) using the same solution were enrolled. Venous blood samples were collected at 5, 15, 30, 45, 60, 120, and 240 minutes after block placement and analyzed for total ropivacaine concentration by use of gas chromatography. Individual timepoints, maximum concentrations (C(max)), and time to C(max) (T(max)) were compared. Values are mean +/- SD.
Both groups demonstrated a rapid increase in plasma concentration over the first 30 to 45 minutes. Concentrations were greater for those who received both blocks (P = .0005) at all timepoints. The lumbar-plexus block C(max) was less (986 +/- 221 ng/mL) than for the combined blocks (1,560 +/- 351 ng/mL, P = .0004). The T(max) was greater for the lumbar plexus (80 +/- 49 min) than for the combined blocks (38 +/- 22 min, P = .03). There was no relationship between the C(max) and patient age, weight, or body mass index.
The results of this study demonstrate that the plasma ropivacaine concentrations increase quicker when a sciatic-nerve block is added to a lumbar-plexus block, but C(max) remains below the toxicity threshold.
The regional and developmental expression of epidermal growth factor (EGF) receptor in rat hippocampus was investigated utilizing immunocytochemical techniques at the light and electron microscopic ...levels. EGF receptor immunoreactivity in adult hippocampus was compared to that found at postnatal day 7 (P7). While the receptor was observed in P7 hippocampus, immunostaining was more prominent in the adult hippocampus, especially in the pyramidal CA2 field. Ultrastructural analysis of this region revealed that the receptor was localized to the cell bodies of both P7 and adult neurons rather than the axons or dendrites. The expression of EGF receptor in selected regions of the adult brain was verified by Western blotting. These results demonstrate the presence of EGF receptor in rat hippocampus as early as P7, localize the receptor to the pyramidal cell body, and establish the hippocampal formation, particularly CA2, as a major site of EGF receptor expression in rat brain.
The physiologic changes that occur with advancing age and their effect on the duration of peripheral nerve blocks have yet to be defined. We prospectively studied the duration of sciatic nerve block ...using mepivacaine in younger and older patients. Eighty ASA physical status I-III patients, aged 18-35 (n = 40) or 55-80 (n = 40) yr, having outpatient knee arthroscopy with a femoral block and a standardized sciatic nerve block were enrolled; 37 in each group completed the study. All patients received a Labat sciatic nerve block using 20 mL of 1.0% mepivacaine with 0.1 mEq/mL sodium bicarbonate and 1:400,000 (2.5 microg/mL) epinephrine and a femoral nerve block. The duration of sensory block (sensation of pinprick, temperature, and vibration), motor block (plantar and dorsi flexion), and complete sensory and motor block in the sciatic nerve distribution of the operative extremity were measured. The time for complete return of both sensory and motor function was longer in the older group, 329 +/- 47 min compared with 306 +/- 46 min (mean +/- sd) in the younger group (P = 0.04). The difference was small under the conditions of this study and would not be perceived clinically. Age also increased the time to return of vibratory sensation (younger = 292 +/- 58 min, older = 257 +/- 50 min; P = 0.007). The other measurements did not differ between groups. We conclude that age may affect peripheral nerve blocks and that more investigation is needed to determine the pharmacologic, physiologic, and chronologic factors behind these findings.
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