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Biomedical subjects

W R Keatinge

Publications and source records attributed to W R Keatinge.

At least 37 records · Page 2Linked to original sources
PubMed1994

Cold-induced increases in erythrocyte count, plasma cholesterol and plasma fibrinogen of elderly people without a comparable rise in protein C or factor X.

1. Six elderly (66-71 years) and six young (20-23 years) subjects (half of each group women) were cooled for 2 h in moving air at 18 degrees C to investigate possible causes of increased mortality from arterial thrombosis among elderly people in cold weather. Compared with thermoneutral control experiments, skin temperature (trunk) fell from 35.5 to 29.5 degrees C, with little change in core temperature. 2. Erythrocyte count rose in the cold from 4.29 to 4.69 x 10(12)/l, without a change in mean corpuscular volume, indicating a 14% or 438 ml decline in plasma volume; increased excretion of water, Na+ and K+ accounted for loss of only 179 ml of extracellular water. 3. Plasma cholesterol and fibrinogen concentrations rose in the elderly subjects from 4.90 mmol/l and 2.97 g/l (control) to 5.45 mmol/l and 3.39 g/l in the cold, and in the young subjects from 3.33 mmol/l and 1.84 g/l (control) to 3.77 mmol/l and 2.07 g/l in the cold. Increases were significant for the elderly subjects, the young subjects and the group as a whole, except for cholesterol in the young subjects, and all were close to those expected from the fall in plasma volume. 4. Plasma levels of Protein C and factor X did not increase significantly in the cold in the elderly subjects, young subjects, or the group as a whole. 5. The results suggest that loss of plasma fluid in the cold concentrates major risk factors for arterial thrombosis, while small molecules, including protective Protein C, redistribute to interstitial fluid.

Adult↗
PubMed1989

Factors associated with hypothermia in patients admitted to a group of inner city hospitals.

In a case-control study of factors contributing to hypothermia all fourteen patients (mean age 80 years) admitted to hospital with hypothermia after being found ill indoors also had some other serious illness. They were more likely than control patients to have been alone when taken ill (93 vs 39% of controls), to live alone (86 vs 43%), and to have been found on the floor (79 vs 14%). They were less likely to have been wearing more than indoor clothing (0 vs 50%), or to have had heating on when found (50 vs 89%), but 93% of patients in both groups had heating available. Healthy young adult volunteers who lay immobile on the ground in air at 5 degrees C lightly clothed cooled progressively by 0.57 degrees C (SD 0.32) (rectal T degrees) in 90 min despite doubling of metabolic rate. With better insulation in bed, core temperature stabilised within 90 min, and when they were in an armchair it fell slowly, with no increase in metabolic rate in either case. The findings suggest that hypothermia indoors resulted largely from collapse due to illness when the patient was alone lightly clothed and not in bed. Eight hypothermic patients found outside (in December and January) were younger (mean age 60 years) than the fourteen found indoors; six of these were chronic alcoholics or acutely intoxicated, and six lacked, or had wandered from, a fixed home.

Adult↗
PubMed1989

Changes in seasonal mortalities with improvement in home heating in England and Wales from 1964 to 1984.

Changes in summer (July-September) and winter (January-March) mortalities of people aged 70-74 in England and Wales from 1964 to 1984 were compared with possible causal factors. Summer mortalities were little affected by annual temperature or influenza epidemics and fell from 1972-1975 for all causes, coronary and respiratory causes, while cerebrovascular mortality fell more rapidly from that time. Cigarette consumption also fell from 1972-1975; falling consumptions of total fat from 1970 and saturated fat from 1972-1975 probably also contributed to the fall in arterial deaths, and likewise falls in prescription rates for tranquillisers and sedatives from 1976-1978 to the fall in respiratory deaths. From 1964 to 1984 use of central heating increased from 13% to 69% of households, domestic fuel consumption increased, and excess mortality in winter from respiratory disease declined by 69%, even relative to summer mortality and when adjusted for varying coldness of winters. The improvement was partly explained by a decline in influenza epidemics. By contrast, excess mortalities in winter from coronary and cerebrovascular disease, although rising in some early influenza epidemics, did not fall significantly as home heating improved. These thrombotic deaths together accounted for 56% of the total excess winter mortality by 1984. The findings support other indications that most of the excess mortality from arterial thrombosis in winter in England and Wales is due to brief excursions outdoors rather than to low indoor temperatures.

Aged↗
PubMed1987

Effects of carbon dioxide on mental performance.

Although elevated levels of inspired CO2 have been recorded in work situations, little is known about effects of concentrations greater than 6% on mental performance. We have measured the effects of inhaling 0, 4.5, 5.5, 6.5, or 7.5% CO2 for 20 min on normal young adults unhabituated to CO2. Performance of reasoning tasks, such as AB logic problems, was significantly slowed at the higher levels of CO2, with a threshold at end-tidal PCO2 close to 51 Torr. Accuracy of reasoning and short-term memory were not significantly affected. More prolonged studies with inhalation of 6.5% CO2 showed that after the first 10 min ventilation tended to increase, end-tidal PCO2 to fall, and slowing of reasoning to recover, but substantial decrement in performance continued for 80 min, by which time performance virtually stabilized. On return to air breathing, preexposure performance was resumed within 10 min. Also caused by 6.5% CO2 was a significant rise in subjectively assessed irritability and discomfort, with no significant change in alertness or in either registration or recall of long-term memory.

Adult↗
PubMed1986

Increased platelet and red cell counts, blood viscosity, and plasma cholesterol levels during heat stress, and mortality from coronary and cerebral thrombosis.

Recorded deaths from coronary and cerebral thrombosis rise markedly in heat waves. In a British heat wave with little or no distortion due to air-conditioning, outside temperatures of 34.6 degrees C (maximum) and 20.8 degrees C (minimum) were followed by peak mortalities from coronary and cerebral thrombosis one to two days later. Experimental exposure of volunteers to moving air at 41 degrees C for six hours caused core temperature to rise 0.84 degree C, weight to fall 1.83 kg with sweating despite access to water, heart rate to increase 32 beats per minute, and arterial pressure to fall, particularly on standing. The red blood cell count increased 9 percent, and blood viscosity increased 24 percent, mostly after the first hour. The platelet count rose 18 percent, and the platelet volume fell, mostly in the first hour. The plasma cholesterol level increased 14 percent without a change in distribution among lipoprotein fractions. The changes seem able to explain the increased mortality from arterial thrombosis in hot weather.

Adult↗
PubMed1986

Effects of fluctuating skin temperature on thermoregulatory responses in man.

Fluctuations in the skin temperature of volunteers in water, of up to +/- 1.5 degrees C, were induced by circulating water through a tube suit at a fluctuating temperature for 80 min. Fluctuations with a cycle length of 2.5, 5.0 or 10.0 min all slowed the fall in core temperature that otherwise occurred in water at 29 degrees C, and reduced thermal comfort. Metabolic rate increased. Symmetrical fluctuations, or ramp fluctuations with either slow cooling and rapid warming phases or slow warming and rapid cooling phases, were all effective. Similar but less clear effects on core temperature were usually produced by fluctuating skin temperature in water at 25 and 33 degrees C; metabolic rate tended to increase during fluctuation in the 25 degrees C experiments, but not in the 33 degrees C experiments. Stability of the temperature of cutaneous receptors appears to be factor in insidious hypothermia produced by immersion in mildly cool water.

Adult↗
PubMed1985

Heat exchanges in wet suits.

Flow of water under foam neoprene wet suits could halve insulation that the suits provided, even at rest in cold water. On the trunk conductance of this flow was approximately 6.6 at rest and 11.4 W . m-2 . C-1 exercising; on the limbs, it was only 3.4 at rest and 5.8 W . m-2 . degrees C-1 exercising; but during vasoconstriction in the cold, skin temperatures on distal parts of limbs were lower than were those of the trunk, allowing adequate metabolic responses. In warm water, minor postural changes and movement made flow under suits much higher, approximately 60 on trunk and 30 W . m-2 . degrees C-1 on limbs, both at rest and at work. These changes in flow allowed for a wide range of water temperatures at which people could stabilize body temperature in any given suit, neither overheating when exercising nor cooling below 35 degrees C when still. Even thin people with 4- or 7- mm suits covering the whole body could stabilize their body temperatures in water near 10 degrees C in spite of cold vasodilatation. Equations to predict limits of water temperature for stability with various suits and fat thicknesses are given.

Adult↗
PubMed1985

Effects of raised body temperature on reasoning, memory, and mood.

Volunteers' body core temperatures were raised to 38.80-39.05 degrees C within a few minutes by immersion in water at 41 degrees C. Tests were then made with the subjects insulated and cooling slowly. Control immersions were made in water at 37 degrees C when core temperatures remained at 36.60-37.40 degrees C. Neither memory registration nor recall of memories registered an hour earlier, nor immediate ability to recall digit spans forward or backward was affected by the increase in core temperature. The increase in temperature did not have any significant effect on accuracy of performance of verbal logic problems or of two-digit subtractions. However, the increase in core temperature was associated with a significant increase in the speed of performance of the tests, by 11 and 10%, respectively. The warm immersions also induced a significant decrease in alertness and an increase in irritability as assessed subjectively by the volunteers; control immersions had no such effects.

Adult↗
PubMed1984

Increases in platelet and red cell counts, blood viscosity, and arterial pressure during mild surface cooling: factors in mortality from coronary and cerebral thrombosis in winter.

Six hours of mild surface cooling in moving air at 24 degrees C with little fall in core temperature (0.4 degree C) increased the packed cell volume by 7% and increased the platelet count and usually the mean platelet volume to produce a 15% increase in the fraction of plasma volume occupied by platelets. Little of these increases occurred in the first hour. Whole blood viscosity increased by 21%; plasma viscosity usually increased, and arterial pressure rose on average from 126/69 to 138/87 mm Hg. Plasma cholesterol concentration increased, in both high and low density lipoprotein fractions, but values of total lipoprotein and lipoprotein fractions were unchanged. The increases in platelets, red cells, and viscosity associated with normal thermoregulatory adjustments to mild surface cooling provide a probable explanation for rapid increases in coronary and cerebral thrombosis in cold weather. The raised arterial pressure and possibly cholesterol concentration may contribute to slower components of the increased thrombosis.

Adolescent↗
PubMed1983

Action of vasodilator agents on inner and outer muscle of bovine coronary arteries.

Noradrenaline and adrenaline (via beta-receptors), adenosine, and prostacyclin all relaxed inner more than outer muscle in coronary arteries contracted by histamine. In submaximal concentrations, noradrenaline, and usually the other dilator hormones, produced proportionately even greater relaxation of inner than outer muscle. Inner and outer strips contracted by 5-hydroxytryptamine showed similar but smaller differences in response to noradrenaline. Outer strips contracted by methacholine were little affected by noradrenaline, though inorganic nitrite relaxed them.

Adenosine↗
PubMed1983

Impaired memory registration and speed of reasoning caused by low body temperature.

Volunteers' body core temperatures were lowered by immersion in water at 15 degrees C. Aspects of cognitive function were subsequently tested after rewarming had been started in water at 41 degrees C when their skin was warm and they felt comfortable but their body core temperature remained low. Memory registration was found to be impaired progressively when core temperature fell from about 36.7 degrees C; at core temperatures of 34-35 degrees C the impairment caused loss of approximately 70% of data that could normally be retained. However, recall of previously learned data was not impaired at these core temperatures. On a two-digit calculation test, speed of performance was impaired by about 50% at a core temperature of 34-35 degrees C, but provided enough time was available, accuracy of performance was not reduced.

Adult↗
PubMed1982

Constrictor actions of acetylcholine, 5-hydroxytryptamine and histamine on bovine coronary artery inner and outer muscle.

1. In bovine coronary arteries, cholinesterase staining showed an extensive cholinergic innervation at the adventitia-media junction, and some cholinesterase in the outer but not inner smooth muscle.2. Acetylcholine or methacholine caused large, atropine-sensitive contractions of outer muscle but caused little contraction of inner muscle.3. Fluorescence microscopy for monoamines and for histamine, supported by chemical assays, showed no adrenergic innervation but showed numerous fluorescent cells in the adventitia and the outer 50% of the media which stained as mast cells and contained large amounts of histamine and noradrenaline and some dopamine, but little 5-hydroxytryptamine (5-HT).4. 5-hydroxytryptamine (acting by D receptors) and histamine (acting by H(1) receptors) in high concentrations caused large contractions, of similar size, in inner and outer muscle. In given submaximal concentrations they generally caused more contraction of outer than inner muscle, particularly in the case of histamine, provided that imipramine or desipramine was present to inhibit uptake of the agents by mast cells which were present in the outer part of the artery wall.5. Without blockade of uptake, 5-HT applied to the arteries in submaximal concentrations caused less contraction of outer than inner muscle; histamine still caused significantly more contraction of outer than inner muscle.6. The findings indicate that the cholinergic constrictor nerves of these arteries, unlike adrenergic constrictor nerves of other systemic arteries, act almost solely on outer muscle of the vessel wall; and that mast cells give considerable protection against constriction by 5-HT, but little against histamine, reaching the vessel from its adventitial surface.

Acetylcholine↗
PubMed1982

Restoration of thermoregulatory response to body cooling by cooling hands and feet.

Deep body temperature fell progressively by 0.5-1.4 degrees C during 3-h immersions in 29 degrees C water. Both in unacclimatized volunteers and, to a lesser degree, in divers in cold-water training, cooling the hands and feet for 1 h in 12 degrees C water during such immersion caused sensation of cold, shivering, and rise in metabolic rate; it caused body temperature to rise in unacclimatized subjects and halted its fall in divers. Tissue conductances generally fell a little in divers but rose in unacclimatized subjects, probably because of muscle blood flow associated with the greater shivering in the latter. Soaking the skin for 4 h produced no major changes in cutaneous thermal sensation assessed in the forearm, though with seawater it sometimes reduced cold sensation and with distilled water sometimes reduced warm sensation, a little. It is concluded that uniform skin temperature of 29 degrees C often induces insufficient heat-gain reflexes to maintain body temperature and that cooling of the extremities can restore adequate thermoregulatory response.

Adult↗