Current issues in spinal anesthesia

Abstract

PINAL anesthesia is a venerable and simple technique. Technical competence is achieved early during training (> 90% technical success rate) after only 40-70 supervised attempts. 1 Although the ease and long history of spinal anesthesia may give the impression that it is an unsophisticated technique, much has been recently learned regarding the anatomy, physiology, pharmacology, and applications of spinal anesthesia.A An na at to om my y The arachnoid membrane is an important structure, as spinal agents must be delivered within its confines. The arachnoid membrane is composed of overlapping layers of epithelial cells connected by tight junctions. This anatomic arrangement allows the arachnoid membrane, not the dura, to function as the principal meningeal barrier (90% of resistance) to materials crossing in and out of the cerebrospinal fluid (CSF). The arachnoid membrane serves not only as a passive container of CSF but also actively processes and transports agents attempting to cross the meninges. Recent studies demonstrate that metabolic enzymes are expressed in the arachnoid membrane that can affect agents (e.g., epinephrine) and neurotransmitters important for spinal anesthesia (e.g., acetylcholine). 2 Active transport of compounds across the arachnoid membrane occurs in the area of the neural root cuffs where unidirectional transport of materials from the CSF into the epidural space occurs and may contribute to clearance of spinal anesthesia agents. After injection of spinal anesthetics, dilution with the CSF occurs prior to arrival at effector sites in the CNS. Thus, individual variation in lumbosacral volumes of CSF and distribution within this volume will affect spinal anesthesia. Recent imaging with magnetic resonance demonstrates great variability between individuals in volume of lumbosacral CSF with a range of 28-81 mL. Interestingly, obese individuals have substantially less CSF (~10 mL less) that is partly due to compression of the neural foramina. Clinical correlation between volume of lumbosacral CSF and spinal anesthesia with hyperbaric lidocaine and isobaric bupivacaine is excellent with CSF accounting for 80% of the variability for peak block height and regression of sensory and motor block. 3 Unfortunately, volume of lumbosacral CSF does not correlate with external physical measurements other than weight. Thus, CSF volume cannot be easily estimated from physical examination and is not easily applied to the clinical setting. 3 P Ph hy ys si io ol lo og gy y Cardiovascular The most common serious side effects from spinal anesthesia are hypotension and bradycardia, and closed claims surveys of 40,000-550,000 spinal anesthetics indicate an incidence of cardiac arrest from 0.04-10/10,000. 4,5 Large surveillance studies typically observed incidences of hypotension around 33% and bradycardia around 13% in non-obstetrical populations. 4 Risk factors for hypotension in non-obstetrical populations include block height $ T5, age $ 40 yr, baseline systolic blood pressure (SBP) < 120 mmHg, and spinal punctur...

Spinalanästhesie in der Tageschirurgie

“…Aufgrund seines kurzen Wirkprofils ist Lidocain im ambulanten Sektor weit verbreitet; es wird jedoch wegen der hohen Inzidenz transienter neurologischer Symptome (TNS) von bis zu 30% inzwischen nicht mehr uneingeschränkt für die intrathekale Anwendung empfohlen [7,9,25]. Bupivacain birgt ein sehr niedriges Risiko für TNS (0-1%); in äquipotenter Dosierung beschränkt die langsame Erholung von der sensomotorischen Blockade allerdings die Anwendung in der Tageschirurgie [15].…”

“…Mit dem kurz wirksamen Prilocain steht eine Alternative zu Lidocain ohne erhöhte TNS-Inzidenz zur Verfügung [9,15]. Ziel der vorliegenden prospektiven Studie war herauszuarbeiten, inwieweit sich die Abläufe in der Tageschirurgie durch die Verwendung von 2%igem hyperbarem Prilocain anstelle von 0,5%igem hyperbarem Bupivacain optimieren lassen.…”

Perioperative Strategien zur Regulierung des Sympathikotonus

“…Ein starker Blutdruckabfall kann bei bis zu 30% und eine Bradykardie bei 5% der Patienten auftreten. Prä-Hydrierung, langsame Injektion des Lokalanästhetikums und unilaterale Anlage der Blockade kön-nen einen Beitrag zur Verminderung von hämodynamischen Nebenwirkungen leisten [46]. Wenn die Ausbreitung der Spinalanästhesie vorsichtig und schrittweise mit einer Kathetertechnik erfolgt ("kontinuierliche Spinalanästhesie") kann das Risiko hypotensiver Episoden und kardialer Ischämieereignisse im Vergleich mit der üblichen Bolusinjektion deutlich gesenkt werden [23].…”

Effects of spinal anesthesia on the peripheral and deep core temperature in elderly diabetic patients undergoing urological surgery

“…is known to signifi cantly impair thermoregulation by inhibiting vasomotor and shivering responses and by redistributing heat from the core of the body to peripheral tissues [1][2][3].…”

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is known to signifi cantly impair thermoregulation by inhibiting vasomotor and shivering responses and by redistributing heat from the core of the body to peripheral tissues [1][2][3].Patients with long-term diabetes mellitus (DM) develop various complications of neuropathy, particularly disorders of microvascular function [4] and autonomic nervous activity [5]. Patients with DM may thus be expected to display different vascular responses and changes in body temperature of the lower limb during spinal anesthesia.

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