To the Editor: One of the limitations of the pulse oximeter (1) is an unreliable or unrecordable Spo2 reading when there is a loss or diminution of the peripheral pulse caused by proximal blood pressure cuff inflation, improper positioning, hypotension (2), hypothermia (3), peripheral vascular disease, or infusion of vasoconstrictor drugs. The most common cause is peripheral vasoconstriction, which produces inadequate plethysmographic pulsations and leads to low-quality signal allowing false saturation readings. Many novel methods have been used to eliminate this problem, i.e., warming cool extremities (4), application of vasodilating creams, and digital nerve blocks (5). A procedure previously described digital nerve blocks as blocking volar sympathetic nerves at the level of interfingerweb by injecting 2–4 mL of local anesthetics. This causes local vasodilatation and improved pulse oximeter signal. As an alternative to digital nerve blocks, we injected 0.5–1 mL of 1% lidocaine without addition of a vasoconstrictor in the pulp space of distal phalanx of the finger. The digital nerves and arteries are not strictly cutaneous, because they also supply structures such as tendons and joints. These nerves and arteries lie in fatty connective tissue on sides of flexor tendons in a tunnel formed by septa stretching from the phalanges to the skin (6). Direct infiltration of local anaesthetics into the fatty tissue of digital pulp space places the local anesthetic drug very close to distal digital nerves, thus blocking the sympathetic nerve supply. This should cause an increase in capillary flow and pulse volume. We studied more than 100 patients undergoing major abdominal surgeries who had significant introperative fluid loss. At least 45 patients had vasoconsticted peripheries and loss of pulse oximeter signal. In all cases there was a significant increase in signal strength after infiltration of local anesthetic. The lag time for signal enhancement after injecting local anesthetic was 2–3 minutes and the signal remained for 1.5 hours thereafter. In conclusion, we found the pulp space infiltration of local anesthetic an easy, safe, quick alternate method to digital nerve block for pulse oximeter signal enhancement. V. Hari Prasad Krovvidi MD V. K. Grover MD, MNAMS P. Chari MD, FAMS