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The influence of magnesium and calcium on the proprioceptive regulation of arterial pressure
SEIXCTED Wexler,
J., Whittenberger, termining Circulation of the Oximeter.
ABSTRACTS
J. L., and Himmelfarb, Time From Pulmonary J. Clin. Investigation 2.5:447
675
S.: An Objective Method to Systemic Capillaries by (May), 1946.
for the
DeUse
The oximeter is an instrument which measures continuously the oxygen saturation of arterial blood by means of photoelectric calorimetry of the intact fully flushed ear. The interval between the beginning of a deep breath of 100 per cent nitrogen and the beginning of the downward deflection of the recording device (a galvanometer) was considered to be the time required for the unsaturated blood to pass from .the lungs to the ear. In thirty-five subjects without heart disease the range of values was 4.1 to 7.0 seconds with an average value of 5.2 seconds. Twenty-three subjects (66 per cent) were within the range of 4.6 to 5.5 seconds and the variation on repeated tests in any individual did not exceed 1.8 seconds. Of course the recorded values are probably higher than the true pulmonary to systemic capillary circulation time since the measurement includes the time of inspiration, diffusion time of the nitrogen in the residual air, the galvanometer lag, and the reaction time of the observer. The method promises to be useful and accurate in that it is objective, requires a minimum of cooperation on the part of the patient, and eliminates the variable arm-to-lung segment in the usual method of measuring the circulation time.
Heymans, C., and Capet, prioceptive Regulation therap. 51:164 (Nov.),
L.: of 1945.
The Influence of Arterial Pressure.
Magnesium and Arch. internat.
Calcium on de pharmacodyn.
the
Proet de
It is well known that magnesium has a depressant action on the central nervous system which can be neutralized by calcium. On the other hand, calcium deficiency has been shown to cause a diminution of the aortic and carotid sinus reflexes which control the proprioceptive regulation of An investigation was therefore made of the reciprocal influences of magnesium arterial pressure. and calcium on the vasomotor reflexes originating in the carotid sinus and of the action of calcium on arterial hypertension produced by suppression of the four aortic and carotid sinus nerves. The studies were performed on dogs and led to the following conclusions: 1. Magnesium sulphate can depress and almost paralyze the vasomotor reflexes concerned in the proprioceptive regulation of general arterial pressure. 2. Calcium chloride or thiosulphate can re-establish the vasomotor reflexes of the carotid sinus which have been depressed or paralyzed by magnesium. 3. Suppression of the four depressor nerves produces a substantial hypertension which may be permanent or transient. The fall of arterial pressure after hypertension is produced by suppression of the depressor nerves is due to cardiovascular collapse caused hy the hypertension. 4. Calcium administered intravenously protects the heart against the effects of sudden hypertension produced by suppression of the four depressor nerves. 5. Calcium administered intravenously, on the one hand, stimulates the heart but, on the other hand, increases and maintains the hypertension produced by suppression of the depressor nerves. LAPLACE.
J., Whittenberger, termining Circulation of the Oximeter.
ABSTRACTS
J. L., and Himmelfarb, Time From Pulmonary J. Clin. Investigation 2.5:447
675
S.: An Objective Method to Systemic Capillaries by (May), 1946.
for the
DeUse
The oximeter is an instrument which measures continuously the oxygen saturation of arterial blood by means of photoelectric calorimetry of the intact fully flushed ear. The interval between the beginning of a deep breath of 100 per cent nitrogen and the beginning of the downward deflection of the recording device (a galvanometer) was considered to be the time required for the unsaturated blood to pass from .the lungs to the ear. In thirty-five subjects without heart disease the range of values was 4.1 to 7.0 seconds with an average value of 5.2 seconds. Twenty-three subjects (66 per cent) were within the range of 4.6 to 5.5 seconds and the variation on repeated tests in any individual did not exceed 1.8 seconds. Of course the recorded values are probably higher than the true pulmonary to systemic capillary circulation time since the measurement includes the time of inspiration, diffusion time of the nitrogen in the residual air, the galvanometer lag, and the reaction time of the observer. The method promises to be useful and accurate in that it is objective, requires a minimum of cooperation on the part of the patient, and eliminates the variable arm-to-lung segment in the usual method of measuring the circulation time.
Heymans, C., and Capet, prioceptive Regulation therap. 51:164 (Nov.),
L.: of 1945.
The Influence of Arterial Pressure.
Magnesium and Arch. internat.
Calcium on de pharmacodyn.
the
Proet de
It is well known that magnesium has a depressant action on the central nervous system which can be neutralized by calcium. On the other hand, calcium deficiency has been shown to cause a diminution of the aortic and carotid sinus reflexes which control the proprioceptive regulation of An investigation was therefore made of the reciprocal influences of magnesium arterial pressure. and calcium on the vasomotor reflexes originating in the carotid sinus and of the action of calcium on arterial hypertension produced by suppression of the four aortic and carotid sinus nerves. The studies were performed on dogs and led to the following conclusions: 1. Magnesium sulphate can depress and almost paralyze the vasomotor reflexes concerned in the proprioceptive regulation of general arterial pressure. 2. Calcium chloride or thiosulphate can re-establish the vasomotor reflexes of the carotid sinus which have been depressed or paralyzed by magnesium. 3. Suppression of the four depressor nerves produces a substantial hypertension which may be permanent or transient. The fall of arterial pressure after hypertension is produced by suppression of the depressor nerves is due to cardiovascular collapse caused hy the hypertension. 4. Calcium administered intravenously protects the heart against the effects of sudden hypertension produced by suppression of the four depressor nerves. 5. Calcium administered intravenously, on the one hand, stimulates the heart but, on the other hand, increases and maintains the hypertension produced by suppression of the depressor nerves. LAPLACE.