SB 4.28.46

yadā nopalabhetāṅghrāv
 ūṣmāṇaṁ patyur arcatī
āsīt saṁvigna-hṛdayā
 yūtha-bhraṣṭā mṛgī yathā
Word for word: 
yadā — when; na — not; upalabheta — could feel; aṅghrau — in the feet; ūṣmāṇam — heat; patyuḥ — of her husband; arcatī — while serving; āsīt — she became; saṁvigna — anxious; hṛdayā — at heart; yūtha-bhraṣṭā — bereft of her husband; mṛgī — the she-deer; yathā — as.
Translation: 
While she was serving her husband by massaging his legs, she could feel that his feet were no longer warm and could thus understand that he had already passed from the body. She felt great anxiety upon being left alone. Bereft of her husband’s company, she felt exactly as the deer feels upon being separated from its mate.
Purport: 

As soon as the circulation of blood and air within the body stops, it is to be understood that the soul within the body has left. The stoppage of the blood’s circulation is perceived when the hands and feet lose heat. One tests whether a body is alive or not by feeling the heart’s palpitations and the coldness of the feet and hands.