Basic orientation of the article, by the leader of a group of medical researchers associated with hospitals in Lyon, France, is toward definition and classification. A table divides OH (orthostatic hypotension) according to physiopathological classification into sympathicotonic and asympathicotonic types and then each of these into primary and secondary with subdivisions. The figure sketches organization and functioning of the baroreflex arc. Applications to clinical study of circulatory reflexes, listing measurement tests and the biological study of hormonal regulation listing the appropriate kinds of studies. Data are not given

Ninet, J.

English

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ORTHOSTATIC HYPOTENSION
J. Ninet
(NASA-T11-75889) ORTHOSTATIC HYPOTENSION
	 N81-20728
(National Aeronautics and Space
Administration) 11 p HC A02/MF A01 CSCL 065
Onclas
G3/52 41882
Translation of "W hypotension orthostatique", Lyon Medical,
1980, Vol. 244, No. 13, pp 7-9
c
CD w
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGT0N, D. C. 20546 	 FEBRUARY 1981
STANDARD TITLE PAGE
1.	 Report No.
NASA TM-75839
2. Governmont Accession No. 3.	 Recipient's Coteleg No.
4.	 Title end Subtitle.
ORTHOSTATIC HYPOTENSION
S.	 Re er 1 0 ate
FEPBRU
	 1981
6.	 Performing Otgonisolien Cede
7.	 Auther(s)
J. Ninet
8.	 Performing Otgenisolien Report No.
10.	 work unit No.
11.	 CtlQtrwFR— 7
1r77
 No.
1VtE^ J►1NN _71 J9.	 Puformin	 Orgonisetion Noma and Address
Leo Kanner Associates 13.	 Type of Report and Period Covered
Redwood City, California 94063 Translation
12.	 Sponsoring Agency Noma and Address
National Aeronautics and Space Admin.
Washington, D. C.
	
20546 14.	 Sponsoring Agency Cede
15.	 Supplementary Notes
Translation of "L'hypotension orthostatique", Lyon Medical,
11980,	 Vol.	 244,	 No.	 13,	 pp 7-9	 .
16.	 Abstr ict
Basic orientation of the article, by the leader of a group
of medical researchers associated with hospitals in Lyon,.
France, i3 toward definition and classification.	 A Table
divides OH (orthostatic hypotension) according to physio-
pathological classification into sympathicotonic and asym1-
pathicotonic types and then each of these into primary and
secondary with subdivisions.	 The Figure sketches organiza-
tion and functioning of * the baroreflex arc. 	 Applications to
clinical study comprise the physiological study of circula-
tory reflexes, listing measurement tests and the biological
study of hormonal regulation listing the appropriate kinds
of studies.	 Data are not given.
17.	 Kay words (Selected by Author(%)) 11.	 Distribution Statement
Unclassified-Unlimited
19.	 Security Clessif. (of this report) 20.	 Security Clessif. (of this peg*) 21. No. of Pages 22.	 Price
Unclassified Unclassified
NASA-HO
ORTHOSTATIC HYPOTENSION
J. Ninet
Hopit: Edouard-Herriot, Clinique Medicale A (Pres. J. Pasquier)
Determination of a significant pressure drop > or = 40 mm Hg /7*
systolic and > or = 20 mm Hg diastolic and persistent (5 min) in
the passage from decubitus to orthostasis defines orthostatic hypo-
tension.
It means the deregulation of one or several of the mechanisms
which normally maintain tensional homeostasis in orthostasis.
Mechanisms of Physiological Adaptation to Orthostatism
In passage to orthostasis 400-600 ml of blood (0.10 total vol-
emia) proceeding to an extent of 808 from the intrathoracic compart-
ment will accumulate, due to weight, in the low pressure capaci-
tive venous system of the lower half of the body, i. e. the lower
members and the splanchnic region. The result is a reduction in
venous cardiac reflux, of left ventricular repletion ..nd thus, by
Starling's law, of systolic ejection volume, cardiac flow and arte-
rial pressure. If this drop in pressure is not corrected, there
will be cerebral ischemic manifestations, since conditions have
gone beyond the point where autoregulation of the CNS is possible.
In the healthy subject these phenomena are combatted at once
by a series of neuroendocrine mechanisms, basically reflex, which
act upon the three determining factors in arterial pressure: car-
diac flow (rate times undulated systolic volume), resistance of the
peripheral arterioles and circulating blood mass. Thus the pres-
sure drop is discrete, ca 5-10 mm Hg, and very transitory. Correc-
tion occurs at second 10 diastolic and seconds 20-60 systolic.
Thus average BP remains the same.
* Numerals in the margin indicate pagination in the foreign text.
1
TABLE I. ETIOLOGICAL PRINCIPLES OF ORTHOSTATIC HYPOTENSION (OH)
PHYSIOPATHOLOGICAL CLASSIFICATION
SYMPATHICOTONIC OH
	
ASYMPATHICOTONIC OH
Primary	 Primary
- Bradbury-Eggleston
- Shy-Dracer
Secondary	 Secondary
- iatrogenic (neuroleptic,
nitrated)
- hypovolemia
global (dehydration)
circulatory (varices,
thermodilatation,
deadaptation, preg-
nancy)
- hyperbradykininism
- iatrogenic (D.L. sympath-
ectomy; ganglioplegic)
- organic
- peripheral neuropathic
(diabetes, porphyria,
amylosis)
- syringomyelia, Biermer
- Gayet Wernicke
This hemodynamic equilibrium in orthostatism is guaranteed ba-
sically by cardiac acceleration of approximately 208 and by a 308
elevation in peripheral resistances. Cardiac flow remains reduced
by about 158, as does also blood volume, due to temporary exagger-
ation of capillary filtration under hypertension.
a) The autonomic nervous system comprising the baroreflex neu-
rochemical arc
This (see Fig. 1) plays the chief role in such adaptation.
The initial drop in pressure brings with it a reduction in the affe-
rent influxes reaching the bulbar vasomotor centers starting from
the sinocarotid and aortal baroreceptors. There immediately ensues
a removal of the vagal inhibitor and reinforcement of orthosympath-
etic, and in an accessory way medullosuperrenal, activity giving
rise to arteriolar and venous vasoconstriction, tachycardia and im-
provement in cardiac inotropism.
b) Hormonal Regulation
This has a slower corrective affect.
Stimulation of the renin-angiotensin-aldosterone system (RAAS)
2
VI
Fig. 1. Organization and Functionin%4 of Baroreflex Arc.
Pressure drop perceived by baroreceptors (1). Reduced
influx into inhibitor nerves (2) reduces activity of
nucleus of tractus solitarius (NTS). This induces:
- through interneuron facilitator (+) and vagus (x)
a condition of tachycardia
- through interneuron (-) inhibiting vasomotor cent-
er (lateral reticular nucleus NRL) increased activity
of bulbospinal pathway leading to tractus intermedio-
lateralis (TIML). Stimulation of sympathetic nervous
system (SNS) and medullosuprarenal (MSR) brings on ac-
tive vasoconstriction through release of norepineph-
rine (NA) and adrenalin (A).
Key: a. splanchnic nerve
through activation of the intrarenal iegvlatoiv mechanisms (baro-
and chemoreceptors) as well as the entrarenal ones (sympathetic
nervous system, SNS) imt,ediately increases arteriolar resistances
by angiotensin and secondarily sodium retention by aldosterone.
Stimulation of secretion of the antidiuretic hormone, in re-
sponse to information from the central osmoreceptors and atrial
voloreceptors, also controls volemia by reducing renal elimination
of free water.
3
c) Importance of Myogenic Regulation
This is objectified by the major drop in pressure induced
by passive orthostatism (tilt on a seesaw table) rather than by ac-
tive. Muscular contraction at the level of the lower limbs and ab-
domen actually favors venous reflex, as does acceleration of respi-
ratory rhythm.
Etiopathogenic Mechanisms in OH
a) The complexity of the regulatory system and its relative
fragility explain the great variety of causes that may involve OH
(Table I). Vasoconstrictive insufficiency, by itself or linked
with vagal breakdown, plays the chief role in the determination of
this involvement. Hypovolemia, whether absolute or relative, is L
less often responsible. Pathological vasodilatation mediated hu-
morally is exceptional.
b) Two major physiopathic types of OH may be recognized:
The first is sympathicotonic. The orthostatic pressure
drop is moderate and accompanied by considerable tachycardia. The
baroreflex arc is anatomically intact but cedes its compensatory
role to the intensity of the disturbance (functional neuroSsnic,
volemic or myogenic) generating the OH.
The second type is asympathicotonic and is characterized
by a deep depression of systolodiastolic pressure but without acce-
leration adapted to cardiac rate (less than 15/min). Much less fre-
quently it even signalizes serious impairment of the reflex arc it-
self.
Applications to Clinical Study
Numerous case histories, employed basically for research purpo-
ses and particularly in the pr:-„ary forms, attempt to define exac-
tly the mechanism of OH deregulation and to localize the anatomical
or functional problem causing it.
4
a Physiological Study of Circulatory Reflexes
A battery of tests is used to study the various compon-
ents of this reflex by measuring cardiac rate (EKG) and BP (Hg man-
ometer, bleeding method or cardiac catheter). However, the results
must be interpreted prudently: some tests are actually negative in
a normal subject and most of them are not entirely specific in re-
gard to the pathways they explore.
- The integrity of the total baroreflex arc can be tested in
two ways: orthostatism of the type we have shown in the definition
or its equivalents which permit us to neglect myogenic regulation
(verticalization on the tilting table or lower pressure applied to
the inferior half of the body) and the Valsalva (deep inspiration
followed by expiratory effort with closed glottis).
- Integrity of bulbar vasomotor centers and efferent sympa- L
thetic fibers is studied by seeking a hypertensive stress response
(-..) sudden noise, mental arithmetic), response to cold (hand
plunged in ice water) and to hypercapnia (inhalation of a CO 2 en-
riched gas mixture).
- Reactivity of arteriolar receptors is tested by the intensi-
ty to he hypertensive response during pharmacological tests with,
basically, direct sympathomimetics (norepinephrine), indirect ones
(tyramine) or angiotensin. Some authors also study the appearance
of hypotension with arteriolar beta stimulants (isoproterenol) or
venodilators (trinitrin).
- Integrity• of the afferent arc, of the center and of vagal ef-
ference is tested by modification of cardiac rhythm with ocular and
sinocarotid compression, atropine IV and norepinephrine perfusion.
b) Biological Studies of Hormonal Regulation
This comprises three parts:
5
- Study of catecholamines and of dopamine bota hydroxylae
(DBH) activity
- daily urinary elimination of catecholamines and their
metabolites;
- changes in urinary yield or in amounts of plasma nor-
epinephrine (and in an accessory way of adrenalin and DBH) with
postural stimulation;
- changes in urinary yield of adrenalin (and in an ac-
cessory way of norepinephrine and DBH) with insulin hypoglycemia.
- Study of the renin-angiotensin-system (RAS)
- dosage of plasma renin activity and of plasma concen-
tration of aldosterone following 10 hr decubitus with normal sod-
ium diet and different types of stimulation (postural, hypoglyce-
mia, sodium depletion);
- determination of volemia.
- Study of antidiuretic hormone with dosage of plasma neuro-
physines before and after postural stimulation
c) Study of Extravascular Functions of Autonomic Nervous System
Such studies make it possible to assay the integrity of
innervation:
- pupillar innervation by collyria tests (direct and in-
direct sympathico- and parasympathicomimetic);
- sudorimotor and thermoregulatory innervation by eleva-
ting central temperature, injection of parasympathomimetics (ace-
tylcholine, pilocarpine) and cutaneous thermography;
- sphincter, urigenital and rectal innervation by electro-
myography;
- gastric secretion by chemical processes.
Types of Primary off
These cannot be properly pictured until secondary causes have
been eliminated. Two affections, of very different prognostic im-
portance, must be opposed.
6
a) Primary Sympathicotonic OH
Observed especially among young women, it is a benign
functional disturbance, probably associated with deficient veno-
constriction. For a number of authors it would be no more than the
initial phase of vasovagal reactions; the hypersympathicotonic
condition would disappear abruptly, giving way to a cholinergic
discharge and acute orthostatic syncope with bradycardia and hypo-
tension due to vasodepression.
b) Primary Asympathicotonic OH
This affection, very rare, sporadic and familial only by
exception (a single case in the literature) ordinarily involves
both sexes in their 6th decade. It is linked with extensive dege-
neration of the autonomic nervous system responsible, on the one
hand, for major postural hypotension without adapted tachycardia
and, on the other hand, for a concomitant profuse autonomic sympto-
matology (anhydrosis, thermal intolerance, impotence, vesical in-
continence or retention, myosis...).
- The Shy-Drager syndrome associates dysautonomic signs with a
central neurological symptomatology, basically extrapyramidal but
at times more complex (extrapyramidal + cerebellar + pyramidal +
anterior horn...). Setting up of neurological signs habitually
follows rapidly upon occurrence of dysautonomic disorders and de-
velopment involves death within 8 yr on the average. The basic a-
natomical lesions involve the TIML, the dorsal vagal nucleus, the
locus niger and the locus coeruleus. Impairment is more discrete
and variable in frequency at the level of the putamen, the cerebel-
lar cortex, the pons nuclei, the bulbar olivae, the anterior horns
of the medulla and the sympathetic ganglia.
- In idiopathic OH (Bradbury-Eggleston) the dysautonomic signs
are isolated. Survival is much longer and incapacity less due to
the absence of neurological involvement. Crossover to Shy-Drager
is possible but rare. Localization on the baroreflex arc is still
open to discussion for want of sufficient anatomical verification:
central and efferent preganglionic lesions as in Shy-Drager or pre-
dominant lesions on the second postganglionic neuron is a decision
that remains to be made.
8
v_
REFERENCES
1. Dyar6gulaticn tensionnelles et affections neuroloaiques (Pres-
aural Dyaregulation and Neurological Affections), in Reani-
mation et Medecine d'Ur ence, 1979, M. Goulon and M. Rap n,
., Expansion Scientifique Frangaise, pp 169-282.
2. Ninet, J., G. Annat, D. Boisson and L. Holzhapfel, L'hypotension
orthostatique (Orthostatic Hypotension), Cah. med. 1980 (in
the press).
9


Orthostatic hypotension

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