tokens: An initial dose of 0 . 1 microgram . kg - 1 . min - 1 of PGE1 ( 15 patients ) , or 10 micrograms . kg - 1 . min - 1 of TMP ( 15 patients ) was administered intravenously after the dural opening and the dose was adjusted to maintain the mean arterial blood pressure ( MAP ) at about 60 mmHg .