The present invention relates to a Lactuca sativa seed designated 45-193 RZ, which exhibits a combination of traits including resistance to downy mildew (Bremia lactucae Regel) races B1:1 to B1:31 and CA-I to CA-VIII, currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and root aphids (Pemphigus bursarius), and which has a medium head size, medium sized outer leaves, and moderately incised leaves. The present invention also relates to a Lactuca sativa plant produced by growing the 45-193 RZ seed. The invention further relates to methods for producing the lettuce cultivar, represented by lettuce variety 45-193 RZ.