Posture Notes.TXT

Created : 2013-02-23
Revised : 2013-02-23
Author : Tom Coleman

Upon standing, blood drops to the lower torso where it is
less effective in promoting venous return. Cardiac output
falls. Arterial pressure falls if the autonomic response is
inadequate. If the autonomic response is normal, arterial
pressure is maintained by a substantial vasoconstriction.

Starting with Rowell's data - posted in the HumMod Repository
under Data | Posture and Hemodynamics

               Recumbent Standing % Change
               --------- -------- --------
Mean BP           97        98       ~0
Cardiac Output   6.0       4.6      -23
TPR             16.2      21.3      +31
HR                62        90
SV               100        55
RAP                6         1
Forearm          3.0       0.4      -87
Forearm Muscle   1.5       0.3      -80
Liver            1.5       0.7      -53
Kidney           1.2       0.5      -58

Kaihara used severe hemorrhage in dogs.

                 Control  Bled
                 -------  ------
Mean BP (mmHg)     95      40
CO ((ml/Min)/kG)  130      49
TPR              0.73    0.82
Change in TPR            +12%

Here are the % values for organ resistance after the bleed.

Extremities      822
Spleen           313
Lungs            233
Pancreas         208
Stomach/Duodenum 141
Colon            111
Total Splanchnic 109
Ileum/Jejunum     92
Hepatosplanchnic  84
Kidneys           81
Hepatic Artery    58
Heart             52
Brain             42

Hoffbrand and Forsyth infused norepi, tyramine and
methoxamine and used microspheres. The animals were conscious
so there was probably autoregulatory pushback.

           Resistance (% of Control)
           -------------------------
Whole Body            119
Heart                 120
Brain                 120
Kidney                139
Skin                  203
Skeletal Muscle       112
GI Organs             158
Hepatic Artery        172
Lung (Bracheal)       170
Bone                  135
Fat                    81

References ==================================================

Hoffbrand, B.I. and R.P. Forsyth. Regional blood flow changes
during norepinephrine, tyramine and methoxamine infusions in
the unanesthetized rhesus monkey. J. Pharmacol. Exp. Ther.
184:656-661, 1973.

Jepsen, H. and P. Gaehtgens. Postural vascular response vs.
sympathetic vasoconstriction in human skin during orthostasis.
Am. J. Physiol. 269:H53-H61, 1995.

Kaihara, S. et.al. Distribution of cardiac otput in
experimental hemorrhagic shock in dogs. J. Appl. Physiol.
27(2):218-222, 1969.

End