Source: Schiffer et al, Anesth 2002;96:1325-1330

Reviewer:  R. Prasad, MD

Summary:

• with higher cerebrospinal fluid densities, a higher spinal block level can be expected
• plain bupiv is slightly hypobaric
• density findings interesting and instructive, but not clinically useful until is possible to measure individual patient's CSF density
• however, they did confirm extreme variability in spread. For LE surgery, they recommend hyperbaric solutions with 30degree torso-elevated position during surgery.

• 64 consecutive pts for peripheral orthopedic surgery. Power analysis needed 60 pts (std dev of CSF density from previous report, 80% power to detect 4-segment difference in #dermatomes blocked with p<0.05)
• SAB in the lateral decubitus position, operative side up
• 2ml CSF sampled first (for analysis), then 3 ml plain bupiv 0.5%
• patient immediately turned supine, remained horizontal till end of study
• Maximal sensory block level (MSBL) and time to sensory regression to L4 were determined for each pt
• CSF bupiv densities, and CSF proteins, glucose, sodium, and chloride concentrations measured.

• MSBL highly variable (T1-L1)
• A highly significant but poorly predictive correlation btwn CSF density and MSBL (R^2 = 0.37).
• No signif relation btwn MSBL and other CSF parameters (proteins, glucose, Na, Cl)
• Men vs women: men had higher CSF:
• density,1.000567 ± 0.000091 vs 1.000501 ± 0.000109 g/ml (P = 0.014)
• protein concentration, 0.46 ± 0.18 vs 0.32 ± 0.13 g/l (P = 0.001)
• glucose concentration, 3.27 ± 0.7 vs 2.93 ± 0.5 mM (P = 0.023)
• A highly significant (P = 0.0004) and predictive (R2 = 0.73) inverse correlation was found between MSBL and sensory regression to L4: higher block --> faster regression to L4.