“…Six studies reported HF of New York Heart Association (NYHA) functional class grade II or III [40], III or IV [15,16,43], and IV [17], and only two studies reported opioid use in palliative care [17,43]. Regarding the type of opioids used among patients with AHF, nine studies [17,27,29e35] reported as the use of morphine, while the remaining studies reported opioid [36,37,39] or opiate use [38,42]. In the CHF group, the opioids used included dihydrocodeine [40], morphine [15,43], diamorphine [41], beta-endorphin [28], and oxycodone [15,16].…”