Mallamaci F, Tripepi G, Zoccali C
Vasodepressor syncope in haemodialysis patients
16th Scientific Meeting of the International Society of Hypertension
ISH Abstract Book
(Jun) 16: 1996
Hypotension is the main complication of haemodialysis treatment. It
has recently been shown (JCI, 90, 1657, 1992) that it may be caused by
the activation of a cardiovascular reflex causing abrupt sympathetic
withdrawal, vasodilatation and bradycardia. This study is aimed at
assessing the prevalence of vasodepressor syncope (defined as
hypotension associated with bradycardia) in a large dialysis
population (n = 106) and test the hypothesis that dialysis patients
are predisposed to vasodepressor syncope.
Twenty patients with well
defined dialysis hypotension (i.e. MAP fall > 20% in > 80% of dialysis
treatments) were prospectively identified during a 3-months survey.
These cases underwent non invasive haemodynamic monitoring and TBW
measurement during a standard haemodialysis session. In addition 18
dialysis patients, including 7 patients with dialysis hypotension
underwent a tilt test in a volume-depleted state (after dialysis).
Sixty hypotensive episodes were recorded.
Heart rate rose in 35 episodes, did not change in 19
episodes and fell in 6 episodes. The HR response pattern to
hypotension was highly reproducible in 10 patients (always
tachycardia: 6, always unchanged heart rate: 4). Patients developing
bradycardic hypotension (n = 5) all had an erratic HR response to
hypotension (i.e. bradycardia preceded or followed by tachycardia or
by no HR change) and were characterized either by the typical
haemodynamic pattern of hypovolemia (predialysis hypotension,
tachycardia and low TBW) or by being treated with a very high UF rate
(greater than 0.36 ml/Kg/min). On tilt testing 4 patients developed
bradycardic
hypotension (two hypotension-prone and two hypotension-resistant
dialysis patients).
The overall proportion (20%) of tilt induced
vasodepressor syncope in uraemic patients did not differ from that
reported in healthy subjects and in non-uraemic patients (Kapoor, Am J
Med 1994, 97, 75). Tachycardia is the more frequent HR response
pattern to hypotension in dialysis patients. Vasodepressor syncope in
dialysis patients is consistently associated with marked hypovolemia.
Comment:
This study adds weight to the hypothesis that bradycardic hypotension
in dialysis patients is a physiological response to severe hypovolemia
rather than the expression of a peculiar predisposition to
vasodepressor syncope (Carmine Zoccali, M.D, Reggio Calabria,
Italy).
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16th Scientific Meeting of the International Society of Hypertension
Basic hemodialysis :
Complications (acute)