High entropy values in an organ donor
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Bispectral index (BIS) and entropy are both monitors of electroencephalography (EEG) activity but are seldom applied to organ donors. Authors describe high entropy values associated with incision in an organ donor. A 49-year-old man was diagnosed with brain death due to cerebral ischemia and was scheduled for organ donation. In addition to standard monitors, they also applied continuous entropy and arterial pressure monitoring. Anesthesia was maintained with desflurane (0.5 MAC).

Initially, the entropy values were 0, 0 and 100, respectively for state entropy (SE), response entropy (RE), and burst suppression ratio (BSR). When the first skin incision was made, a sudden increase of SE and RE (more than 60), and a decrease of BSR (0) occurred concomitant with tachycardia and hypertension.

The EEG remained isoelectric. Remifentanil, atenolol, and nicardipine were administered to treat these neurological and cardiovascular changes. Dramatic hemodynamic responses to surgical stimulation have been previously observed during organ donation that occur because of changes in arterial vascular tone. Surgical stimuli can evoke an excessive rise of plasma epinephrine and norepinephrine levels (up to 2000%), which can impair allograft function. These circulating catecholamines may also have an arousal effect, which could cause an increase in BIS due to changes in neurotransmitter levels in the brain despite documented brain death.

The elevated entropy values observed here most likely occurred because of transient increases in serum catecholamine concentrations precipitated by surgical stimulation. Sufficient analgesics and antihypertensive medications are required to reduce sympathetic stimulation, inhibit the release of catecholamines, and maintain hemodynamic stability throughout the procedure.

Source: https://www.jcvaonline.com/article/S1053-0770(21)00368-2/fulltext?rss=yes