title: Incidence and risk factors for side effects of spinal anesthesia.
abstract: We prospectively studied 952 patients to identify the incidence of hypotension (systolic blood pressure less than 90 mmHg), bradycardia (heart rate less than 50 beats/min), nausea, vomiting, and dysrhythmia during spinal anesthesia. Historical, clinical, and physiologic data were correlated with the incidence of these side effects by univariate and multivariate analysis. Hypotension developed in 314 patients (33%), bradycardia in 125 (13%), nausea in 175 (18%), vomiting in 65 (7%), and dysrhythmia in 20 (2%). Variables conferring increased odds of developing hypotension include peak block height greater than or equal to T5 (odds ratio 3.8, P less than 0.001), age greater than or equal to 40 yr (2.5, P less than 0.001), baseline systolic blood pressure less than 120 mmHg (2.4, P less than 0.001), combination of spinal and general anesthesia (1.9, P = 0.01), spinal puncture at or above the L2-L3 interspace (1.8, P less than 0.001), and addition of phenylephrine to the local anesthetic (1.6, P = 0.02). Variables conferring increased odds of developing bradycardia include a baseline heart rate less than 60 beats/min (odds ratio 4.9, P less than 0.001), ASA physical status classification of 1 versus 3 or 4 (3.5, P less than 0.001), current therapy with beta-adrenergic blocking drugs (2.9, P less than 0.001), and peak block height greater than or equal to T5 (1.7, P = 0.02). Variables conferring increased odds of developing nausea or vomiting include addition of phenylephrine or epinephrine to the local anesthetic (3.0-6.3, P less than or equal to 0.003), peak block height greater than or equal to T5 (odds ratio 3.9, P less than 0.001), use of procaine (2.6-4.4, P less than or equal to 0.003), baseline heart rate greater than or equal to 60 beats/min (2.3, P = 0.03), history of carsickness (2.0, P = 0.01), and development of hypotension during spinal anesthesia (1.7, P = 0.009). Our results indicate that the incidence of side effects during spinal anesthesia may be reduced by 1) minimizing peak block height; 2) using plain solutions of local anesthetics; 3) performing the spinal puncture at or below the L3-L4 interspace; and 4) avoiding the use of procaine in the subarachnoid space.
authors.affiliation: Department of Anesthesiology, Virginia Mason Medical Center, Seattle, Washington 98111.
authors.forename: R L
authors.initials: RL
authors.lastname: Carpenter
authors.forename: R A
authors.initials: RA
authors.lastname: Caplan
authors.forename: D L
authors.initials: DL
authors.lastname: Brown
authors.forename: C
authors.initials: C
authors.lastname: Stephenson
authors.forename: R
authors.initials: R
authors.lastname: Wu
mesh_terms: D000328:Adult; D000775:Anesthesia, Spinal / Q000009:adverse effects*; D001919:Bradycardia / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D007022:Hypotension / Q000453:epidemiology / Q000209:etiology*; D008297:Male; D015999:Multivariate Analysis; D009325:Nausea / Q000453:epidemiology / Q000209:etiology*; D011446:Prospective Studies; D012044:Regression Analysis; D012307:Risk Factors; D014839:Vomiting / Q000453:epidemiology / Q000209:etiology*