Saturday, March 19, 2011
abnormal peripheral vascular responses to temperature after sympathectomy
Post-sympathectomy the peripheral vascular failure or the reduced cardiac chronotropic response can impair the body’s capacity to compensate for shock
First, the abolition of sweating from the upper body as well as the axillae and both upper limbs may have significantly reduced the capacity of the patient to lose heat through sweating during exercise. Anhidrosis in the head and neck after sympathectomy affects a proportion of patients, but is often neglected in most reports of post-sympathectomy complications [3]. The loss of head and neck sweating in this patient may have further impaired overall heat loss. However we would also note that the degree of heat loss impairment after sympathectomy has never been quantified, and its effect on body temperature during exercise remains to be established.
Second, thoracic sympathectomy has been demonstrated to abolish or alter sympathetic vasoconstrictive responses in the skin, and this may contribute to abnormal peripheral vascular responses to temperature [4]
Paradoxically it has been suggested that in some cases there may be abnormal vasoconstriction rather than the expected vasodilatation after sympathectomy [5]. It is not impossible that such atypical peripheral vascular responses to rising body temperature may have contributed to impaired heat loss during exercise or to an inappropriate response to shock on the development of the heat stroke.
Alan D.L. Sihoe, FRCSEd(CTh)a,* , Raymond W.T. Liu, MRCPb , Alex K.L. Lee, MRCPb , Chak-Wah Lam, FHKAMb , Lik-Cheung Cheng, FRCSa
http://ats.ctsnetjournals.org/cgi/content/full/84/3/1025
Second, thoracic sympathectomy has been demonstrated to abolish or alter sympathetic vasoconstrictive responses in the skin, and this may contribute to abnormal peripheral vascular responses to temperature [4]
Paradoxically it has been suggested that in some cases there may be abnormal vasoconstriction rather than the expected vasodilatation after sympathectomy [5]. It is not impossible that such atypical peripheral vascular responses to rising body temperature may have contributed to impaired heat loss during exercise or to an inappropriate response to shock on the development of the heat stroke.
In the post-sympathectomy patient, the abnormal sympathetic skin response may lead to peripheral vascular failure or the reduced cardiac chronotropic response may impair the body’s capacity to compensate for shock. These may have contributed to the rapid development of shock and severe multiple organ dysfunction syndrome in this patient.
Third, it has been shown that thoracic sympathectomy can impair the autonomic nervous system’s increase of the heart rate in response to exercise [6]. Although absolute tachycardia is not eliminated, given the endocrine and paracrine stimuli during exercise, the maximum heart rate reached during exercise has been shown to be significantly reduced after sympathectomy. Thus for a given workload during exercise, there will be a relative bradycardia. This may possibly affect the circulatory system’s ability to convey heat from the body core to the extremities for heat loss.
Is Previous Thoracic Sympathectomy a Risk Factor for Exertional Heat Stroke?
Wednesday, March 16, 2011
"Sympathectomy is a technique about which we have limited knowledge, applied to disorders about which we have little understanding."
http://www.pfizer.no/templates/Page____886.aspx
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