Fig. 2. Latencies of somatosensory evoked potential (SSEP) components in healthy unmedicated humans before and after isovolemic hemodilution from hemoglobin concentrations of 12.7 g/dl (Hb13) to 5.1 g/dl (Hb5). Stimulation was applied at the wrist. EP = Erb point (brachial plexus); N13 = cervical spine; N20 = cerebral cortex; H = hemodilution day; C = control day; RA = breathing air; O2 = breathing oxygen. Data are mean ± SD. (A ) Conduction velocity from the wrist to the Erb point was decreased by acute isovolemic hemodilution compared with the subjects’ normal hemoglobin concentrations. Breathing oxygen did not alter the latency during severe isovolemic anemia compared with breathing room air. Latency was not altered at any time during the control day. *Statistically significant difference (P < 0.05) compared with data from baseline at that recording site. (B ) Conduction velocity from the Erb point to the cervical spinal cord was unaffected by reduction of the hemoglobin concentration to 5.1 g/dl (P > 0.8). Breathing oxygen did not alter the latency during severe isovolemic anemia (P > 0.7). Latency was not altered at any time during the control day. (C ) Conduction velocity from the cervical spinal cord to the cerebral cortex was unaffected by reduction of the hemoglobin concentration to 5.1 g/dl (P > 0.8). Breathing oxygen did not alter the latency during severe isovolemic anemia (P > 0.9). Latency was not altered at any time during the control day.