SYMPOSIUM on fluid and electrolytes balance.
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The renal and endocrine actions of atrial natriuretic peptide (ANP) administered at a rate to induce plasma concentrations within the physiological range have been re-examined in conscious rats in which body fluid volume was maintained by infusion of replacement fluid at a rate to match spontaneous urine losses (servo-controlled replacement) throughout experimentation. The involvement of vasopressin in the actions of ANP was assessed by comparing the responses induced in Brattleboro (DI) and Long-Evans (LE) rats. A rate of ANP administration inducing a less than twofold increment in circulating ANP concentration evoked a small but significant diuresis and natriuresis. In contrast to previous studies during which body fluid balance had not been maintained and the response to ANP was transient, renal responses were rapid in onset and sustained over the period of hormone administration. The change in renal excretion occurred without concomitant changes in mean arterial blood pressure, haematocrit or glomerular filtration rate, and without consistent alterations in the circulating concentrations of angiotensin II, vasopressin, aldosterone or corticosterone. Furthermore, although small differences between the two strains in the character of the response could be demonstrated, the evoked response was of similar magnitude in vasopressin-replete and -deficient animals. In summary, in conscious rats in which body fluid volume was maintained, the profile of the diuretic and natriuretic responses evoked by low-rate ANP administration was different from that previously observed in anaesthetized and/or constantly infused preparations; being rapid in onset and sustained.(ABSTRACT TRUNCATED AT 250 WORDS)
OBJECTIVES: The objective of this study was to investigate body weight change in adult patients undergoing cardiac surgery and to assess the accuracy of conventional recorded fluid balance charting methods to reflect this change in body weight. DESIGN: This was a descriptive study. SETTING: This study was conducted at the cardiac care unit and medical-surgical intensive care unit (ICU) of a private hospital in Melbourne, Australia. SUBJECTS: The subjects were 32 adult patients who underwent cardiac surgical procedures. Twenty-six were male, and the mean age was 67 years (range 36-84 years). Twenty-three patients underwent coronary artery bypass graft surgery, and nine patients underwent heart valve repair or replacement+/-coronary artery bypass graft surgery between December 2003 and May 2004. OUTCOME MEASURES: The measures were recorded fluid balance for the perioperative period together with body weight measurements from the night before surgery and immediately on discharge from the ICU. An additional body weight measurement on the seventh postoperative day provided a trajectory of body weight gain or loss for the period of hospitalization after surgery. A retrospective medical history audit and an HV-CS digital chair scale (A&D Mercury Pty Ltd, Victoria, Australia) were used to collect the data. RESULTS: Analysis revealed that 30 patients increased their body weight from the night before surgery until discharge from the ICU. The mean weight gain was 3.34 kg (standard deviation [SD] 1.17, 95% confidence interval 2.70-3.98, P<.001). The average preoperative body weight was 80.97 kg (SD 16.79), whereas the average ICU postoperative weight was 83.94 kg (SD 16.15). Twenty-six patients (81.25%) had returned to, or were below, their preoperative weight by their seventh postoperative day (M 2.96 kg, SD 2.24 kg, P<.05). The average recorded fluid balance during the perioperative period was +1.56 L (SD 2.59 L, P<.001) with a difference of 1.39 kg between the recorded fluid balance and measured body weight change. Three patients (9.75%) met the criteria for accurate recorded fluid balance, and eight patients (25%) experienced a net difference in the opposite direction between recorded fluid balance and body weight change during the perioperative period. CONCLUSION: Body weight in patients who undergo cardiac surgery was found to fluctuate over the perioperative period. Use of recorded fluid balance to reflect change in body weight for patients undergoing cardiac surgery was deemed unreliable. Further investigation of body weight change and scrutiny of conventional recorded fluid balance charting methods for patients who undergo cardiac surgery is needed.
To clarify whether monoaminergic inputs to the subfornical organ (SFO) area participate in fluid regulatory systems, we examined the effects of body fluid depletion on monoamine turnover in the region of the SFO using microdialysis techniques in rats. An iso-osmotic reduction of fluid volume following subcutaneous treatment with polyethylene glycol (PEG) significantly increased dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), and 5-hydroxyindoleacetic acid (5-HIAA) concentrations in the SFO area. 5-hydroxytryptamine (5-HT) in the SFO area could be detected after the PEG treatment, while 5-HT was undetectable before the treatment. The data imply that both dopaminergic and serotonergic systems in the SFO area may be involved in controlling body fluid balance.
The long-term haemodynamic effects of ketanserin, a new serotonin-antagonist, was examined in 13 patients of both sexes (age range 24-62 years) with mild and moderate essential hypertension (EH). Cardiac output (CO) and intra-arterial blood pressure (BP) were measured at rest and during exercise before and after nine months of therapy. On ketanserin the mean casual BP was lowered by 15/21 mmHg to 152/91 mmHg and five of the 13 patients became 'normotensive' (BP less than 140/90 mmHg). The intra-arterial systolic pressure fell by 5-8% and the diastolic pressure by 5-11% from pretreatment levels at rest supine, sitting and during 50, 100 and 150 W exercise. The fall in BP was associated with a reduction in CO at rest while during exercise both a fall in CO and in total peripheral resistance contributed to the hypotensive effect. The fall in CO was due to a reduction in heart rate (average: -4 to 8 beats/min). The stroke volume remained unchanged in all settings and oxygen consumption was not affected by the drug. Body weight and body fluid volumes did not change significantly. Eight patients complained of drowsiness and lack of concentration. It is concluded that in mild and moderate EH ketanserin induces a moderate BP reduction associated with a fall in CO. There is no large vasodilating effect after long-term ketanserin treatment either at rest or during exercise. Ketanserin does not influence body fluid balance. The incidence of side-effects is high.
Six male volunteers performed three tests, each comprising a passive heating session to obtain dehydration (loss of 2.6% body mass), followed by exercise on a treadmill until exhaustion (50% of maximal oxygen consumption) in a warm environment (dry bulb temperature 35 degrees C, relative humidity 20%-30%). In one test, the subjects exercised without rehydration (Dh). In the two other tests, 50% of the fluid lost in the dehydration session was replaced by drinking mineral water given either in one amount [913 (SEM 23) ml] before the exercise (Rh1) or divided into four equal portions [228 (SEM 5) ml] before the exercise and on three occasions at 15-min intervals during exercise (Rh4). Rehydration increased exercise duration in Rh1 compared to Dh [112 (SEM 7) min and 82 (SEM 3) min, respectively; P < 0.05]. The difference was not significant with Rh4 [103 (SEM 9) min]. A restoration of the time course of changes in plasma volume, plasma osmolality, heart rate and rectal temperature occurred immediately in Rh1 and as delayed in Rh4 until after 60 min of exercise. Our results demonstrated that the swift replacement of the fluid loss in the dehydrated subjects was beneficial to exercise performance by rapidly correcting the disturbances in body fluid balance.
The hypocalciuric response to prolonged polythiazide (PTZ) administration has been investigated in intact and thyroparathyroidectomized (TPTX) rats. After 3 control days, PTZ was given for 6 days (0.1 mg/100 g body weight . 24 h p.o.). In both groups, calcium excretion fell on day 1 of PTZ and remained depressed thereafter. In the intact rats, this decrease was associated with increased sodium excretion and urine output on treatment day 1. In the TPTX rats, hypocalciuria occurred without change in sodium excretion or body weight; urine output increased on the first 2 days. Thus PTZ can reduce calcium excretion in the absence of parathyroid hormone, changes in sodium excretion, and changes in body weight (an estimate of body fluid balance with constant food intake).
AIM: To investigate the effects of 7.5% hypertonic saline on positive fluid balance and negative fluid balance, after radical surgery for gastrointestinal carcinoma. METHODS: Fifty-two patients with gastrointestinal carcinoma undergoing radical surgery were studied. The patients were assigned to receive either Ringer lactate solution following 4 mL/kg of 7.5% hypertonic saline (the experimental group, n = 26) or Ringer lactate solution (the control group, n = 26) during the early postoperative period in SICU. Fluid infusion volumes, urine outputs, fluid balance, body weight change, PaO2/FiO2 ratio, anal exhaust time as well as the incidence of complication and mortality were compared between the two groups. RESULTS: Urine outputs on the operative day and the first postoperative day in experimental group were significantly more than in control group (P<0.000001, P = 0.000114). Fluid infusion volumes on the operative day and the first postoperative day were significantly less in experimental group than in control group (P = 0.000042, P = 0.000415). The volumes of the positive fluid balance on the operative day and during the first 48 h after surgery, in experimental group, were significantly less than in control group (P<0.000001). Body weight gain post-surgery was significantly lower in experimental group than in control group (P<0.000001). The body weight fall in experimental group occurred earlier than in control group (P<0.000001). PaO2/FiO2 ratio after surgery was higher in experimental group than in control group (P = 0.000111). The postoperative anal exhaust time in experimental group was earlier than in control group (P = 0.000006). The overall incidence of complications and the incidence of pulmonary infection were lower in experimental group than in control group (P = 0.0175, P = 0.0374). CONCLUSION: 7.5% hypertonic saline has an intense diuretic effect and causes mobilization of the retained fluid, which could reduce fluid infusion volumes and positive fluid balance after radical surgery for gastrointestinal carcinoma, as well as, accelerate the early appearance of negative fluid balance after the surgery, improve the oxygen diffusing capacity of the patients' alveoli, and lower the overall incidence of complications and pulmonary infection after the surgery.
Salt tablets are habitually ingested by some people while doing physical exercise in hot climate, in order to prevent sodium depletion. The effects of supplementary salt on the intraocular pressure was investigated on 5 healthy acclimatized subjects who rode a bicycle ergometer at temperature of 35 degrees C and relative humidity of 40%. A significant decrease of 1.0 mmHg in their mean intraocular pressure was detected when 10.2 gm NaCl was added daily to the normal diet. The pressure reduction was associated with changes of the body fluid balance.
BACKGROUND: Little data is available concerning the heat stress experienced by members of staff who wear bullet-proof vests in a warm or hot environment. For this reason, knowledge is limited and, consequently, preventative advice on how to avoid heat sickness or hyperthermia is required. STUDY DESIGN: Skin and body temperatures, fluid loss and the heart rate of 30 persons (15 test persons versus 15 control persons) were measured in three situations typical of the test participants' job situations. Environmental data (wind velocity, air humidity, air temperature) were measured during the tests as well. RESULTS: Whereas there was a significant increase in skin temperatures, there was no difference in the core body temperatures of both groups. Maximum core body temperature remained well below 38 degrees C in all subjects. Test persons wearing vests showed a fluid loss of 1.1 l on average (non-vest wearers in the control group 1.0 l). CONCLUSION: There is no increased risk of heat stroke or hyperthermia for employees wearing bullet-proof vests in comparison with employees who do not wear them. Both groups, however, should be advised to ensure an adequate intake of fluid to maintain a healthy body fluid balance when working in hot environments.
The present experiments were designed to study behavioral, neurochemical and physiological effects of repeated exposure to subsymptomatic levels of the anticholinesterase, soman. Sprague-Dawley rats were placed on a soman regimen of 35 micrograms kg-1 (0.3 log10 units below the LD50) which consisted of daily injections SC for the first three days, followed by the same dose three times per week for a total of 11 injections (22 days). There were no significant differences in pretreatment baselines between soman-treated and saline control animals for any of the variables measured. Some basic physiological processes, i.e., caloric intake and body fluid balance, and behavioral functions associated with aversive reinforcement (e.g., conditioned avoidance response) were not affected by the soman regimen. Core body temperature showed an early hypothermia and later developed tolerance. Nociceptive sensory and perceptual thresholds were elevated (hypoalgesia) and remained so throughout the treatment. Temporal perception (as evidenced in fixed interval responding) was significantly impaired initially, but tolerance developed as the duration of the regimen increased. Tolerance was also evident in measures of general activity and cognitive functions. The process of tolerance development proceeded when brain AChE activity was depressed and stable, indicating that some other process(es) must have been involved. The results of the present series of experiments show quite clearly that exposure to the antiChE, soman, at subsymptomatic levels can produce differential effects on enzymatic, physiological and behavioral functions, i.e., some of these functions may be affected while others are not. Moreover, effects when they do appear may also differ in that some may persist during the duration of the exposure, while others may appear initially and then disappear as tolerance develops.
It is now well recognized that systemically released angiotensin II (Ang II) and arginine vasopressin (AVP) act in concert in regulation of blood pressure and water-electrolyte balance. Numerous studies have also demonstrated that centrally applied Ang II and AVP cause significant alterations of the cardiovascular functions and body fluid balance. Moreover, it has been established that Ang II and AVP are released in the central nervous system during cardiovascular and osmotic disorders and that the cardiovascular regions of the brainstem and the osmoregulatory regions of the forebrain are extensively innervated by the angiotensinergic and vasopressinergic neurons. Some evidence indicates that the angiotensinergic and vasopressinergic system may interact in the central blood pressure control, although the significance of this interaction may differ in various species. Recently, attempts have been made to find out whether centrally released Ang II and AVP may play a role in the regulation of the cardiovascular system under physiological and pathophysiological conditions. With regard to this, the available evidence strongly suggests that the both systems may be involved in regulation of blood pressure under baseline conditions. In addition, the vasopressinergic system appears to be involved in the adjustment of cardiovascular functions to hypovolemia, whereas its role in regulation of blood pressure during the osmotic disorders is less clear. Regulation of blood pressure and heart rate by centrally released AVP under baseline conditions, during hypovolemia and in osmotic disorders is significantly altered in the spontaneously hypertensive rats. It is now well established that centrally applied Ang II and Ang III are potent dipsogenic compounds. There also is evidence that AVP may enhance the osmotic thirst. However, the physiological role of brain-derived AVP and Ang II in the control of water intake awaits further examination. The available evidence from rat studies does not give support to a significant cooperation between central angiotensinergic and vasopressinergic system in regulation of water intake.
Patients with burns lose large amounts of water through evaporation from open wounds. Because the wound covering is the first line of defense for maintenance of body fluid balance in these patients, quantification of the evaporative water loss through wound coverings at the bedside would improve the accuracy of estimations of body water loss. The present experiment evaluates the use of a small ventilated capsule system automated with miniature resistance-type dew-point sensors for measurement of evaporative water loss through biologic dressings under simulated wound conditions. Evaporative water loss from wounds was simulated by pilocarpine-induced profuse sweating on the forearm. Evaporative water loss through uncovered skin was compared with that of skin covered with commercially available temporary wound dressings. Compared with an adjacent unstimulated area, forearm dew-point temperature in the capsule (Tcdp) and sweat rate increased immediately after pilocarpine exposure and remained significantly elevated and relatively constant for an additional 60 minutes. Evaporative water loss of the forearm was 29 +/- 4.8 gm/m2/hr (mean +/- SE) at baseline and rose significantly to 275 +/- 18.2 gm/m2/hr after pilocarpine exposure. The pilocarpine-stimulated sweat rate and Tcdp at neutral conditions were similar to those obtained from walking on a treadmill for 60 minutes in a 30 degrees C room. Compared with pilocarpine-induced evaporative water loss of the uncovered skin, temporary wound dressings significantly reduced evaporative water loss by 40% to 60%. No significant differences were observed between varieties of temporary wound dressings differing in thickness and/or porosity.(ABSTRACT TRUNCATED AT 250 WORDS)
Thermoregulation during exercise was studied in seven women who were taking oral contraceptive pills for 3 weeks of each month. The subjects were studied once in the 3rd week of taking the pill (P) and once during the following week when they took no pil (N). Rectal temperature (Tre), heart rate (fc) and evaporative water loss (EWL, ventilated capsule technique) were measured while they walked on a treadmill for 60 min at 4.8 km.h-1 at a 10% gradient. Ambient temperature was 22 degrees C. A venous blood sample was drawn 30 min before each experiment for measurement of hematocrit (packed cell volume, PCV), plasma osmolality (Osmpl), and plasma levels of the endogenous pyrogens interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6). Resting Tre was 0.31 degree C higher in P than in N (P < 0.01) and Tre remained higher in P throughout the entire exercise period (P < 0.01). Threshold Tre for the onset of EWL was 0.32 degree C higher in P than in N (P < 0.01). Exercise fc was 6.5 beats.min-1 higher in P than in N (P < 0.01). There was no significant difference in PCV, Osmpl, IL-1 beta or IL-6 between P and N. It was concluded that the administration of synthetic progestins in oral contraceptives causes an upward shift in the threshold for heat loss responses, resulting in higher body core temperatures both at rest and during exercise. There was no evidence that these alterations in thermoregulation were mediated by changes in body fluid balance or in plasma levels of IL-1 beta or IL-6.
BACKGROUND: The effect of reduced cardiopulmonary bypass (CPB) prime volume by retrograde autologous priming (RAP) was studied. METHODS: Twenty patients undergoing elective coronary artery bypass grafting were randomized to either standard prime (SP) volume (1,602 +/- 202 mL crystalloid prime, n = 10) or RAP (395 +/- 150 mL). RAP was performed by draining crystalloid prime from the arterial and venous lines into a recirculation bag before CPB. Cardiac index, pulmonary vascular resistance index, systemic vascular resistance index, alveolar-arterial oxygen tension difference, pulmonary shunt fraction, extravascular lung water (EVLW), plasma colloid osmotic pressure (COP), crystalloid fluid balance, body weight, and clinical parameters were evaluated perioperatively. RESULTS: Demographic data and operative parameters were equal for patients in both groups. During CPB, COP was reduced by 55% in the SP group (9.8 +/- 2.0 vs 21.4 +/- 2.1 mm Hg) and by 41% in the RAP group (12.4 +/- 1.1 vs 20.9 +/- 1.8 mm Hg) (p = 0.008, SP vs RAP group). Compared with preoperatively, EVLW was unchanged in the RAP group 2 hours post-CPB, but it was elevated by 21% in the SP group (p = 0.002, SP vs RAP group). End-CPB crystalloid fluid balance was significantly reduced in the RAP group (1,857 +/- 521 vs 2,831 +/- 637 mL). Postoperative (day 2) weight gain in the SP group (1.5 +/- 1.2 kg, p = 0.021) was absent in the RAP group (0.1 +/- 0.9, NS). Postoperative time to full mobilization was shorter in the RAP group. Postpump cardio-respiratory function did not differ among groups. CONCLUSIONS: This small-scale pilot study indicates that by reducing crystalloid fluid administration and fall of COP during CPB, RAP reduces postpump EVLW accumulation and weight gain in uncomplicated coronary artery bypass graft patients with no associated effects on cardio-respiratory function.