What is the optimal morphine dose to be administered intrathecally in postoperative analgesia of cardiac surgery?

Tamayo E, Alvarez J, Ruiz de Temiño FJ, Martinez A, Florez S (2002). What is the optimal morphine dose to be administered intrathecally in postoperative analgesia of cardiac surgery? Journal of Cardiothoracic and Vascular Anesthesia 16(1), 132-134; author reply 134-135. Enlace