The Influence of a Bupivacaine Digital Nerve Block Using Rev G.

The Influence of a Bupivacaine Digital Nerve Block With the New Continuous Sensor (Rev G) on the Accuracy of SpHb Monitoring.

The investigators are proposing to continue investigation to improve the accuracy of the SpHb (continuous hemoglobin monitoring device) by administering an intermediate acting digital nerve block in the finger connected to the SpHb, specifically bupivacaine 0.25% in patients undergoing spine surgery. Bupivacaine is FDA approved and in routine use.

Patients undergoing spine surgery will be randomized to receive (or not) the bupivacaine digital block on the finger attached to the new limited release version of the hemoglobin sensor, RevG. The SpHb reading will be compared to a blood hemoglobin level analyzed in the UCSF Clinical Laboratories.

Inclusion Criteria:

• Male or female 18 years of age or older
• American Society of Anesthesiologists classification 1, 2 or 3
• Scheduled to undergo spine or hip surgery

Exclusion Criteria:

• Pregnant or nursing
• Patients who in the study investigators clinical judgement would not be suitable