Suero literally means "serum" or refers to the fluid in a medical IV drip. It's a perfect example of the song's central metaphor: comparing heartbreak to a medical emergency.
In the lyrics, Daddy Yankee pleads, “Un suero de cariño es lo que me toca” (An IV drip of affection is what I need). He uses this dramatic, medical imagery to express how desperately he needs his partner's love, as if it were the only medicine that could save his life.
Daddy Yankee drops his signature party sound here for straight-up emergency room drama. The whole track treats a breakup like a sudden medical crisis. He casts himself as a dying man needing immediate first aid, yelling that standard hospital care is useless: "No existe medicina / Doctores ni aspirina" ("No medicine, doctors, or aspirin exist") to fix his broken heart. Instead of paramedics, he demands his ex show up to revive him.
The extended hospital metaphor gets delightfully over-the-top. He begs for an "electroshock" of her warmth, asks for mouth-to-mouth resuscitation ("respiración boca a boca"), and cheekily turns clinical gear into romance by hoping "la camilla sea nuestra camita" (the stretcher becomes our little bed). Notice the playful rhyme between camilla (stretcher) and camita (diminutive for bed). He also pleads for her to "inyéctale calma" (inject calmness) into his soul, mixing frantic panic with pure sweet-talking.