Abstract
Purpose
Neuraxial blockade is known to have a sedative effect, decreasing the need for inhalational and iv anesthetic agents. The purpose of the present study was to quantify the sedative effect of spinal anesthesia and to determine the time of maximum sedation.
Methods
This is an observational study in which 20 unsedated patients were scheduled to undergo urologic and orthopedic surgeries under spinal anesthesia. Patients with pre-existing neurological conditions or receiving psychotropic medications were excluded from the study. All received 1.5 mL (11.25 mg) of hyperbaric bupivacaine 0.75% intrathecally. No sedative or narcotic was administered intravenously or intrathecally. The Patient State Analyzer, (PSA-4000) was used to monitor sedation along with Observer’s Assessment of Alertness and Sedation (OAA/S) scores every five minutes. Differences in patient state index (PSI) and OAA/S scores are expressed as median and range and were evaluated by Wilcoxon’s signed rank test for non-parametric data; P < 0.05 was considered significant. PSI, OAA/S and time at lowest score are expressed as median(range).
Results
PSI scores decreased from baseline 99 (96–99) to 78 (56–87) at 35(14.5–54) min into the spinal anesthetic (P < 0.05). OAA/S scores decreased from baseline 5 to 4 (range 3–5) at the time of the lowest PSI scores (P < 0.05).
Conclusions
In this elderly patient population, spinal anesthesia induced changes in the processed electroencephalogram with reduction in PSI and OAA/S scores. The reduction in afferent input to the reticular activating system could possibly explain the sedation that has been observed and the reduction in the PSA scores.
Résumé
Objectif
L’effet sédatif du bloc neuraxial est connu pour diminuer les besoins d’anesthésiques iv et par inhalation. Nous avons voulu quantifier l’effet sédatif de la rachianesthésie et déterminer le temps nécessaire pour atteindre la sédation maximale.
Méthode
L’étude observationnelle porte sur 20 patients sans sédation qui doivent subir une intervention sous rachianesthésie en chirurgie urologique ou orthopédique. Sont exclus ceux qui ont des pathologies neurologiques préexistantes ou un traitement psychotrope. Tous reçoivent 1,5 mL (11,25 mg) de bupivacaïne hyperbare à 0,75% par voie intrathécale. Aucun sédatif ou narcotique n’est administré par voie intraveineuse ou intrathécale. Le Patient State Analyzer, (PSA-4000), un analyseur de l’état du patient, est utilisé pour surveiller la sédation au même titre que l’Observer’s Assessment of Alertness and Sedation (OAA/S) scores (évaluation de la vigilance et de la sédation par un observateur) toutes les cinq minutes. Les différences de l’index de l’état du patient (IEP) et les scores de l’OAA/S sont exprimés par la médiane et les valeurs extrêmes et évalués par le test de rang des signes de Wilcoxon pour les données non paramétriques; P < 0,05 est considéré significatif. L’IEP, l’OAA/S et le moment du score le plus bas sont exprimés par la médiane (valeurs extrêmes).
Résultats
Les scores de l’IEP ont baissé, par rapport aux données du début, de 99 (96–99) à 78 (56–87) à 35(14,5–54) min avec la rachianesthésie (P < 0,05). Les scores à l’OAA/S ont été plus bas que les données initiales, passant de 5 à 4 (3–5) au moment des scores IEP les plus bas (P < 0,05).
Conclusion
Chez les patients âgés, la rachianesthésie a induit des changements à l’électroencéphalogramme traité et une réduction des scores de l’IEP et de l’OAA/S. La réduction des afférences au système réticulé activateur peut expliquer la sédation observée et la réduction des scores du PSA.
Article PDF
Similar content being viewed by others
References
Greene NM, Brull SJ. Physiology of Spinal Anesthesia, 4th edition. Baltimore: Williams and Wilkins; 1993: 65–7.
Tverskoy M, Shagal M, Finger J, Kissin I. Subarachnoid bupivacaine blockade decreases midazolam and thiopental hypnotic requirements. J Clin Anesth 1994; 6: 487–90.
Eappen S, Kissin I. Effect of subarachnoid bupivacaine block on anesthetic requirements for thiopental in rats. Anesthesiology 1998; 88: 1036–42.
Hodgson PS, Liu SS, Gras TW. Does epidural anesthesia have general anesthetic effects? Anesthesiology 1999; 91: 1687–92.
Ben-David B, Vaida S, Gaitini L. The influence of high spinal anesthesia on sensitivity to midazolam sedation. Anesth Analg 1995; 81: 525–8.
Gentili M, Huu PC, Enel D, Hollande J, Bonnet F. Sedation depends on the level of sensory block induced by spinal anaesthesia. Br J Anaesth 1998; 81: 970–1.
Pollock JE, Neal JM, Liu SS, Burkhead D, Polissar N. Sedation during spinal anesthesia. Anesthesiology 2000; 93: 728–34.
Drover DR, Lemmens HJ, Pierce ET, et al. Patient state index. Titration of delivery and recovery from propofol, alfentanil, and nitrous oxide anesthesia. Anesthesiology 2002; 97: 82–9.
Chernik DA, Gillings D, Laine H, et al. Validity and reliability of the observer’s assessment of alertness/sedation scale: study with intravenous midazolam. J Clin Psychopharmacol 1990; 10: 244–51.
Oreshchuk FA. The development of sleep on local cooling of the spinal cord. Fiziol Z (Moscow). 1960; 46: 1230–5.
Larrabee MG, Posternak JM. Selective action of anesthetics on synapses and axons in mammalian sympathetic ganglion. J Neurophysiol 1952; 15: 91.
Tverskoy M, Fleyshman G, Bachrak L, Ben-Shlomo I. Effect of bupivacaine-induced spinal block on the hypnotic requirement of propofol. Anaesthesia 1996; 51: 652–3.
Caplan RA, Ward RJ, Posner K, Cheney FW. Unexpected cardiac arrest during spinal anesthesia: a closed claims analysis of predisposing factors. Anesthesiology 1988; 68: 5–11.
Pollard JB. Cardiac arrest during spinal anesthesia: common mechanisms and strategies for prevention. Anesth Analg 2001; 92: 252–6.
Prichep LS, John ER, Gugino LD, Kox W, Chabot RJ. Quantitative EEG assessment of changes in the level of sedation/hypnosis during surgery under general anesthesia. In: Jordon C, Vaughan DJ, Newton DE (Eds). Memory and Awareness in Anaesthesia IV. World Scientific Publishing Co.; 1998: 97–107.
Billard V, Gambus PL, Chamoun N, Stanski DR, Shafer SL. A comparison of spectral edge, delta power, and bispectral index as EEG measures of alfentanil, propofol, and midazolam drug effects. Clin Pharmacol Therap 1997; 61: 45–58.
Author information
Authors and Affiliations
Corresponding author
Additional information
Disclosure: We did not receive any funding from any source and have no commercial affiliation with the product manufacturers.
Rights and permissions
About this article
Cite this article
Kurup, V., Ramani, R. & Atanassoff, P.G. Sedation after spinal anesthesia in elderly patients: a preliminary observational study with the PSA-4000. Can J Anesth 51, 562–565 (2004). https://doi.org/10.1007/BF03018398
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF03018398