Patients survival on dyalisis

"Average life expectancy on dialysis is 5-10 years, however, many patients have lived well on dialysis for 20 or even 30 years"[1]

The causes of death in dyalisis patients

"infections accounted for more than 36% of all deaths. Withdrawal occurred in 21.2% of the patients and was most common in patients over age 61. Notably, cardiac deaths accounted for only 14.4% of all deaths <...> Cardiac mortality was not as frequent as anticipated and occurred mainly in patients on dialysis less than 4 years, suggesting that it is the result of preexisting disease." https://pubmed.ncbi.nlm.nih.gov/1882824/ 1991y^{(find more recent)}

In more recent work https://pubmed.ncbi.nlm.nih.gov/14767027/ (2004y, France) 13.9% of people on dialysis died during 1 year. 24% died of cachexia (of 196 died patients, 24 died of cachexia and 23 died of withdrawal of dialysis decided due to cachexia). 18% died of cardiac failure and 6% due to cancer. Only 6.6% died due to infections (so probably better controlled now). Some cardiac/cancer mortality was to be expected anyway due to died patients age being 73 +-12 years (table 2). 3x difference between cardiac/cancer mortality probably can be explained by (a) partial cachexia probably decreases cancer chances(?) (b) probably hard to maintain good level of physical activity => more prone to cardia
Good review on cachexia causes in CKD (and dialysis): 10.1186/s41100-016-0015-5 See table 1; most of causes are not really applicable in head transplantation scenario (either when transplanted to a living person or to artificial body, except as for connection to brain-dead person)

Relevant details on dialysis

Dialysis rate is "usually between 300 and 500 mL/min"[2].
Compare to total cerebral blood flow which is roughly 700±100 mL/min[3].