Delayed embryo implantation following in vitro fertilization and embryo transfer (IVFET).

PURPOSE: Our goal was to compare serum human chorionic gonadotropin (hCG) levels in singleton pregnancies achieved following IVFET with those achieved following spontaneous conception. RESULTS: The mean serum hCG level of patients who became pregnant following IVFET lagged 1.5 days behind that of patients who became pregnant spontaneously. CONCLUSIONS: The use of gonadotropin releasing hormone analogue as part of the stimulation protocol leading to egg retrieval and IVFET results in a delay in embryo implantation.

Nerve stimulator polarity and brachial plexus block.

To determine whether needle polarity significantly affects nerve stimulation during peripheral nerve block, we performed a randomized double-blinded study of 10 patients undergoing axillary block for upper extremity surgery. Using an insulated needle, we determined the minimum current necessary to elicit muscle contraction with positive and negative needle polarity at two needle placements: (A) where stimulation was first observed and (B) where stimulation was maximal. At Position A, stimulation required significantly more current when the needle was positive (2.32 +/- 0.45 mA, mean +/- SEM) than when it was negative (1.05 +/- 0.23 mA, P < 0.001). Similarly, at Position B, stimulation required more current when the needle was positive (1.49 +/- 0.49 mA) than when it was negative (0.47 +/- 0.15 mA, P < 0.001). The mean ratio of positive to negative threshold stimulation current at Position B (3.11 +/- 0.20) was significantly greater than that at Position A (2.37 +/- 0.19, P < 0.05). Our results emphasize the importance of attaching the negative terminal of the nerve stimulator to the stimulating electrode. Use of the positive terminal could lead to abandoning a block if stimulation were not obtained at a low enough current; alternatively, motor contraction might not be observed before neural contact or vascular puncture.