Pengaruh faktor-faktor intra dan pascabedah terhadap disfungsi kognitif pascabedah jantung terbuka: penelitian terhadap nilai nirs, kandungan dan ekstraksi oksigen perioperatif serta penanda serologis = Intra- and postoperative factors affecting POCD after open-heart surgery: analysis of cerebral saturation, oxygen content and extraction, and serologic marker