Source: Mojica et al, Anesth Analg 2002: 94: 432-7

Reviewer:  R. Prasad, MD

Summary:

• 404 pts randomly allocated, 3 groups. All got SAB with hyperbaric 0.5% bupiv, 0.25 mg/kg up to 15mg
• I - LR 1-2 ml/min
• II - LR 20 ml/kg 20min before SAB (in 6-10min, then LR 1-2 ml/min)
• III - LR 20 ml/kg at time of SAB (in 6-10min, then LR 1-2 ml/min)
• Similar:
• pts: age, sex, weight (clinically insignif diff), bupiv dose (~14.2 mg), ASA-PS
• block height >= T5 (63-74%)
• dec in SBP by >=30% of baseline (SIH, or spinal-induced hypotension)
• NS trend for II higher than I [19.2% vs. 12.7%]
• relative risk 1.52; p=0.143
• Fewer cardiovascular side effects (CVSE - N, V, faintness) in III vs. I (9.9% vs. 2.3%, with RR = 0.23; NNT = 13)
• Incidence of SIH and CVSE
• decreased with age up to 40y, then increased
• SIH: 14.3% 11-19y --> 7.3% 30-39y --> 25.0% 70-84y
• CVSE: 7.1% 11-19y --> 2.4% 30-39y --> 19.4% 70-84y
• increased with ASA-PS
• SIH: ASA-PS I 9.8%, III 26.7%
• CVSE: ASA-PS I 2.7%, III 13.3%
• males had more complications
• block >T5 increased risk
• Multivariate analysis: treatment group, age, and block height were only independent variables associated with risk for SIH
• III less likely than I to have CVSE relative risk 0.23)
• >=50yr had relative risk >3x 30-39y
• From T2-T12
• risk SIH increased 25% per segment increase in block height
• risk CVSE inc 47% per segment

• 53.5% men, mean age 42y
• Interesting that CVSE doesn't seem to necessarily correlate with SIH
• Difference in administration time of only a few (20) minutes seems to be important b/c of the incredibly short half-life of crystalloid solutions. Presumably, the first 20min after block is time of greatest risk for sx, and after that reflexes have more or less compensated for block effects.