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Biomedical subjects

J C Johnson

Publications and source records attributed to J C Johnson.

At least 127 records · Page 7Linked to original sources
PubMed1986

Cerebral hemodynamics after hemorrhagic shock: effects of the type of resuscitation fluid.

Cerebral blood flow (CBF), cerebral oxygen delivery, and intracranial pressure were measured in 12 dogs subjected to hemorrhagic shock and then resuscitated with lactated Ringer's solution or 6% hetastarch. Hemorrhagic shock was produced by the rapid removal of blood to achieve a mean arterial pressure (MAP) of 40 mm Hg with BP maintained at that level for 30 min. Six animals were resuscitated with lactated Ringer's solution, 60 ml/kg iv, and six with 6% hetastarch, 20 ml/kg iv. Both solutions effectively restored systemic hemodynamic stability, increasing cardiac output and MAP. Intracranial pressure was significantly (p less than .05) lower after resuscitation in the hetastarch group, but CBF, which had decreased during shock, was not normalized by either fluid, and cerebral oxygen transport fell further with resuscitation secondary to a hemodilutional reduction of hemoglobin. Although 6% hetastarch may improve systemic hemodynamics and maintain a low intracranial pressure during resuscitation, it fails, as does lactated Ringer's solution, to restore cerebral oxygen transport to prehemorrhagic shock levels.

Animals↗
PubMed1986

Effects of hypertonic saline versus lactated Ringer's solution on cerebral oxygen transport during resuscitation from hemorrhagic shock.

Hypertonic saline successfully restores systemic hemodynamics in dogs and humans with severe hemorrhagic shock and, in contrast to lactated Ringer's solution, does not increase intracranial pressure (ICP). This study compares cerebral oxygen delivery in 12 dogs subjected to hemorrhagic shock by the rapid removal of blood (mean arterial pressure of 40 mm Hg maintained for 30 minutes), and then resuscitated with lactated Ringer's solution (six dogs) or 7.5% saline solution (six dogs) to restore systolic arterial pressure. Both solutions effectively restored systemic hemodynamic stability, increasing cardiac output and systolic blood pressure while decreasing mean and diastolic arterial pressure and systemic vascular resistance. The ICP was significantly lower after resuscitation in the hypertonic saline group (p less than 0.05), but cerebral blood flow, which had decreased during shock, was not restored by either fluid, and cerebral oxygen transport fell further secondary to a hemodilutional reduction of hemoglobin. Although hypertonic saline may improve systemic hemodynamics and maintain a low ICP during resuscitation, it fails, as does Ringer's solution, to restore cerebral oxygen transport to prehemorrhagic shock levels.

Animals↗
PubMed1985

Effects on intracranial pressure of resuscitation from hemorrhagic shock with hypertonic saline versus lactated Ringer's solution.

Hypertonic saline (2400 mOsm/L) has been used successfully for fluid resuscitation of dogs subjected to severe hemorrhagic shock. This study compared the effects of resuscitation with hypertonic saline vs. lactated Ringer's solution on intracranial pressure (ICP) in dogs subjected to 30 min of sustained hypovolemic shock. Hypotension was produced by rapid withdrawal of blood until mean arterial pressure was 50 mm Hg, maintained at that level by withdrawal or infusion of blood over the next 30 min as necessary. Eight animals were resuscitated with hypertonic saline solution and nine with lactated Ringer's solution. Both solutions restored systolic blood pressure and cardiac output to control values. However, diastolic blood pressure and mean arterial pressure did not return to control values. The most prominent difference between the two groups was in ICP measured after resuscitation. ICP was lower in dogs resuscitated with hypertonic saline than in dogs resuscitated with lactated Ringer's solution (p = .029). Hypertonic saline fluid resuscitation may represent a potential alternative when aggravation of intracranial hypertension during resuscitation would place a patient at greater risk.

Analysis of Variance↗
PubMed1985

Pulmonary artery wedge pressure may fail to reflect left ventricular end-diastolic pressure in dogs with oleic acid-induced pulmonary edema.

We investigated the accuracy with which pulmonary artery wedge pressure (WP) reflected left ventricular end-diastolic pressure (LVEDP) in dogs with oleic acid-induced pulmonary edema. We compared hemodynamic variables before and during edema, as measured from a pulmonary artery catheter placed before oleic acid (PA-1) and from a second catheter (PA-2) placed 2 h after oleic acid infusion. Oleic acid decreased arterial oxygen saturation and cardiac output and increased pulmonary vascular resistance and phasic pulmonary artery pressure. LVEDP did not change after oleic acid, although WP measured by both catheters was increased. In addition, WP measured by PA-2 (7.1 +/- 0.7 mm Hg) was greater than that measured by PA-1 (5.6 +/- 0.5 mm Hg) (p less than or equal to 0.037). Using PA-1, we found that WP increased in a linear manner with LVEDP both before and after pulmonary injury (r2 = 0.91, 0.68, respectively). There was no relationship between LVEDP and WP using PA-2 (r2 = 0.07). We conclude that oleic acid-induced pulmonary edema lessens the accuracy with which WP reflects LVEDP, and that WP from a catheter placed after edema less accurately reflects LVEDP than does WP from a catheter placed before edema.

Animals↗
PubMed1985

Effects on cerebral hemodynamics of resuscitation from endotoxic shock with hypertonic saline versus lactated Ringer's solution.

This study was carried out to determine whether 7.5% hypertonic saline (HSS) and lactated Ringer's solution restore cerebral hemodynamics comparably when used for resuscitation from endotoxic shock. Endotoxic shock was produced in 13 dogs by the iv administration of 1.5 mg/kg Escherichia coli endotoxin. After 90 min of shock, seven animals were resuscitated with lactated Ringer's solution, 60 ml/kg iv, and six with 7.5% HSS, 6 ml/kg iv. Both solutions increased cardiac output and mean arterial pressure. With HSS, intracranial pressure was lower immediately after resuscitation (p less than .001) and one hour later (p less than .01). However, cerebral blood flow was not increased by either fluid and, due to hemodilution, cerebral oxygen transport decreased during resuscitation in both groups of animals. Thus, HSS restored systemic hemodynamics and maintained a lower intracranial pressure during resuscitation from endotoxic shock, but failed, as did lactated Ringer's solution, to restore cerebral blood flow and oxygen transport.

Animals↗
PubMed1985

Vasomotor abnormalities as post-polio sequelae: functional and clinical implications.

Persons who had poliomyelitis report cold and discolored extremities and decreased muscle strength when exposed to mildly cool ambient temperatures. Bilateral digital cutaneous blood flow, skin temperature and median nerve latencies and amplitudes were measured at 30 degrees C, 25 degrees C and 20 degrees C in five post-polio subjects and age-matched controls. Cutaneous blood flow was lowest on the more affected side in the post-polio subjects but vasoconstriction with decreasing Ta was equal bilaterally in both groups. With decreasing Ta, median motor nerve latencies became clinically abnormal and "giant" sensory nerve potential amplitudes were seen in a majority of the post-polio subjects. It is concluded that an impairment of sympathetic vasoconstrictor outflow in post-polios allows passive dilatation and engorgement of the cutaneous venous capacitance beds. This promotes uncontrolled heat loss and causes cooling of nerve and muscle that is responsible for the impairment of muscle functioning and the abnormal electrophysiological findings.

Adult↗
PubMed1984

High-frequency jet ventilation produces auto-PEEP.

Positive-pressure ventilation can increase dead space by trapping gas, especially at high frequencies. Under conditions of high airway resistance and high pulmonary compliance, gas trapping can increase alveolar pressure without affecting proximal airway pressure, due to impedance to expiratory gas flow. The difference between alveolar pressure and proximal airway pressure at end-expiration has been called auto-PEEP. Using a mechanical test lung, we altered compliance and resistance under a variety of high-frequency jet ventilator settings to evaluate the generation of auto-PEEP. High driving pressures and prolonged inspiratory times significantly increased gas trapping. This effect was most pronounced when both airway resistance and pulmonary compliance were elevated. These findings support the concept that high-frequency jet ventilation (HFJV) may have deleterious side-effects in patients with chronic obstructive pulmonary disease.

Airway Resistance↗
PubMed1983

The medical evaluation and management of the elderly surgical patient.

Contrary to earlier findings, elderly patients are not at significantly greater risk of perioperative morbidity or mortality than younger patients simply because of advanced age. Increased risk, when present, is attributable to pathologic changes that are not uniformly seen in all geriatric patients. Most perioperative morbidity is caused by cardiovascular and pulmonary complications. The author discusses an appropriate preoperative evaluation and recommends selective ancillary tests to screen for high-risk patients.

Aged↗
PubMed1983

A multiple extraction--centrifugation method for the recovery of viruses from waste water treatment plant effluents and sludges.

Absorption of 14C-labelled poliovirus-2 to sedimentable solids of primary sludge samples collected from a secondary treatment facility during a 6-month period averaged 94%; for anaerobically digested sludge, 99%. The extent of virus adsorption was influenced by the amount of solids. Maximal adsorption occurred at or above 0.5% solids with sludge diluted with deionized water and above 1.5% solids when diluted with the respective particle-free sludge supernatants. A Tris-HCl buffer containing NaCl, glycerol, and serum was found to efficiently elute poliovirus-2 from primary sludge solids. By means of re-extraction and concentration by centrifugation (the TEC procedure), the average recoveries of poliovirus-2 were 92-94% based upon either infectivity or radioactivity analyses. Similarly, recoveries were 90-92% for poliovirus-2 in digested sludge. Maximum elution was dependent upon all four TEC buffer components and the restriction of solids to less than or equal to 1.0%. The procedure was found to be more efficient than glycine-NaOH and Freon procedures or elution with beef embryo extract. As adapted for effluents the procedure increased the yield and improved the consistency of virus recovery. The arithmetic mean titers and obtained during a monitoring study for primary and digested sludge were 4.2 X 10(5) and 5.1 X 10(3) plaque-forming units (pfu)/L; for primary, secondary, and final effluents 2.3 X 10(5), 4.7 X 10(3), and 4.7 X 10(2) pfu/L, respectively.

Centrifugation↗
PubMed1983

Comparison of total body surface map depolarization patterns of left bundle branch block and normal axis with left bundle branch block and left-axis deviation.

Total body surface maps from 15 subjects with left bundle branch block and normal axis (LBBB-NA) and 10 subjects with left bundle branch block and left axis (LBBB-LA) were analyzed and compared with maps from normal subjects. In 19 of the 25 subjects with LBBB, the timing of early upper sternal positivity was similar to that of normal subjects, indicative of timely but oppositely directed septal activation. The right ventricular breakthrough was normally located in all, but was earlier after the onset of QRS than expected in some. The initial portion of the positivity produced by left ventricular activation was located in the upper anterior chest in both LBBB-NA and LBBB-LA, but its onset was generally delayed compared with that in normal subjects, presumably because of the time taken by the right-to-left septal activation. Also, the total duration of this positivity was longer than in normal subjects and extended considerably beyond 90 msec, indicating prolonged activation of the anterior free wall of the left ventricle. In LBBB-NA, this upper anterior positivity remained anterior throughout depolarization, but in LBBB-LA it moved toward the left shoulder and the left upper back, presumably due to the posterior orientation of the terminal portion of depolarization. This terminal orientation in patients with LBBB-LA was thought to be due to the additional delay in the activation of the anterobasal portion of the left ventricle caused by selective involvement of the left anterior fascicle.

Aged↗
PubMed1983

Crossbred and purebred dairy cattle in warm and cool seasons.

This study was to determine if breed groups ranked differently in warm (May to August) and cool (November to February) seasons of calving and to determine if heterosis was more important in the warm season. A total of 719 records of cows in first lactation in four herds in the southeastern United States were used. Breeds were Holsteins, Brown Swiss, and Jerseys and the crosses among them. Milk and milk fat yields were greater in the cool season than in the warm season. Holsteins exceeded other breeds for milk and milk fat yield in both seasons, but their superiority was less among cows calving from May through August. Days open were longer for Holsteins, particularly in the warm season. In the cool season only the 3/4 Holstein X 1/4 Swiss group exceeded Holsteins for milk, but two groups--1/2 Holsteins X 1/2 Swiss and 5/8 Holstein X 1/4 Swiss-1/8 Jersey--were higher in the warm season. In the cool season three crossbred groups--1) 1/2 Holstein X 1/2 Swiss (Holstein sires), 2) 3/4 Holstein X 1/4 Swiss, and 3) 1/2 Holstein X 1/4 Swiss-1/4 Jersey--had greater milk fat yields than Holsteins, and a fourth--1/2 Holstein X 1/2 Jersey--yielded an equal amount. In the warm season six of the eight crossbred groups had greater milk fat yields than Holsteins. More crossbreds exceeded Holsteins in the warm than in the cool season, suggesting interactions for yields. There was slightly more heterosis in warm than in cool seasons for all traits.

Animals↗
PubMed1982

Ouabain binding and potassium relaxation in aortas from renal hypertensive rabbits.

This study was designed to characterize the electrogenic sodium pump in vascular smooth muscle from one-kidney one-clip (1K-1C), renal hypertensive rabbits. Two measures of the electrogenic pump were used: 1) [3H]ouabain binding and 2) potassium-induced relaxation. The binding study indicated a significant increase in the affinity of pump sites for ouabain in aortic strips from hypertensive rabbits compared with those from normotensive rabbits (Scatchard analysis). The maximal binding capacity of the binding sites was similar in the two groups of animals, whereas the concentration of ouabain at which half-maximal binding occurred was lower in the aortic strips from hypertensive rabbits. Aortic strips from hypertensive rabbits showed greater sensitivity to the relaxant effect of potassium after incubation in potassium-free solution. The potassium-induced relaxation in aortic strips from hypertensive rabbits was more sensitive to the inhibitory effect of ouabain than that in strips from normotensive rabbits. These results suggest that the increased sensitivity to potassium and ouabain in vascular smooth muscle from hypertensive rabbits is due to an increased affinity of the pump sites for these substances.

Animals↗
PubMed1981

The determination of the human ventricular gradient from body surface potential map data.

We have analyzed the Wilson ventricular gradient in terms of body surface potential maps and of the reduction of such surface patterns to equivalent dipoles or vectors. While the ventricular gradient traditionally was treated as first a scalar, then a vector concept, we found that the three entities (QRS area, T area, QRST area) did not reduce to vectors with a common location. However, conventional vector addition (QRST area = QRS area + T area) did precisely apply. Further we found considerable more-than-vector or extra-dipolar information remaining for all three entities after removal of the dipole effect. This suggests that maps of these entities should be considered the boundaries of complex electrical fields rather than simple surface effects of vectors.

Adult↗