Arginine vasopressin release following surgical operations

Effect of controlled hypotensive hemorrhage on plasma sodium levels in anesthetized pigs: An exploratory study

Perioperative hyponatremia, due to non-osmotic release of the antidiuretic hormone arginine vasopressin, is a serious electrolyte disorder observed in connection with many types of surgery. Since blood loss during surgery contributes to the pathogenesis of hyponatremia, we explored the effect of bleeding on plasma sodium using a controlled hypotensive hemorrhage pig model. After 30-min baseline period, hemorrhage was induced by aspiration of blood during 30 min at mean arterial pressure <50 mmHg. Thereafter, the animals were resuscitated with retransfused blood and a near-isotonic balanced crystalloid solution and monitored for 180 min. Electrolyte and water balances, cardiovascular response, renal hemodynamics, and markers of volume regulation and osmoregulation were investigated. All pigs (n = 10) developed hyponatremia. All animals retained hypotonic fluid, and none could excrete net-free water. Urinary excretion of aquaporin 2, a surrogate marker of collecting duct responsiveness to antidiuretic hormone, was significantly reduced at the end of the study, whereas lysine vasopressin, i.e., the pig antidiuretic hormone remained high. In this animal model, hyponatremia developed due to net positive fluid balance and generation of electrolyte-free water by the kidneys. A decreased urinary aquaporin 2 excretion may indicate an escape from antidiuresis.

American Society for Enhanced Recovery (ASER) and Perioperative Quality Initiative (POQI) joint consensus statement on perioperative fluid management within an enhanced recovery pathway for colorectal surgery

BACKGROUND

Enhanced recovery may be viewed as a comprehensive approach to improving meaningful outcomes in patients undergoing major surgery. Evidence to support enhanced recovery pathways (ERPs) is strong in patients undergoing colorectal surgery. There is some controversy about the adoption of specific elements in enhanced recovery "bundles" because the relative importance of different components of ERPs is hard to discern (a consequence of multiple simultaneous changes in clinical practice when ERPs are initiated). There is evidence that specific approaches to fluid management are better than alternatives in patients undergoing colorectal surgery; however, several specific questions remain.

METHODS

In the "Perioperative Quality Initiative (POQI) Fluids" workgroup, we developed a framework broadly applicable to the perioperative management of intravenous fluid therapy in patients undergoing elective colorectal surgery within an ERP.

DISCUSSION

We discussed aspects of ERPs that impact fluid management and made recommendations or suggestions on topics such as bowel preparation; preoperative oral hydration; intraoperative fluid therapy with and without devices for goal-directed fluid therapy; and type of fluid.

Postoperative vasopressin and copeptin levels in noncardiac surgery patients: a prospective controlled trial

Further information on the endogenous arginine vasopressin (AVP) response in patients with postoperative systemic inflammatory response syndrome (SIRS) and vasodilatory shock would provide more insight into the pathophysiology of SIRS-associated cardiovascular failure and help indicate AVP therapy. Patients after uncomplicated abdominal surgery without SIRS (n = 10), critically ill patients after noncardiac surgery with SIRS (n = 9), and patients with SIRS plus vasodilatory shock (n = 22) were included in this prospective trial. Plasma AVP (radioimmunoassay) and copeptin (immunoluminometric assay) concentrations together with clinical parameters were documented daily during the first 7 days postoperative. The AVP response significantly differed between the three groups. Patients without SIRS had lower AVP concentrations than SIRS patients with (P = 0.001) or without shock (P = 0.003). Patients with SIRS and shock had higher AVP levels than patients with SIRS alone (P < 0.001). Arginine vasopressin decreased over time (P = 0.007) in all groups. At day 28, nonsurvivors had higher AVP levels than did survivors (P < 0.001). In SIRS patients without shock, serum osmolarity was indirectly associated with AVP levels, whereas mean arterial blood pressure and serum osmolarity were associated with AVP in SIRS patients with shock. Arginine vasopressin and copeptin correlated significantly with each other (P < 0.001; r = 0.76). In patients without hemofiltration, copeptin levels predicted 28-day mortality with high sensitivity and specificity. The postoperative AVP response in noncardiac surgery patients seems well maintained. The possibility that AVP plays a contributory role in the failure to restore vascular tone in patients with vasodilatory shock cannot be excluded but seems less important than in septic or postcardiotomy shock.

Plasma vasopressin, cortisol, and growth hormone concentrations in relation to surgery in the suprasellar region

Posterior and anterior pituitary functions were assessed in 8 patients before, during, and after surgery for tumors in the suprasellar region. Preoperatively, all patients but one responded adequately to an osmotic stimulus with a rise in plasma vasopressin (AVP) and all but one showed adequate cortisol response to adrenocorticotropic hormone (ACTH) and hypoglycemia. During surgery a transient rise was seen in plasma levels of AVP (5 out of 8 patients), cortisol (7 out of 8 patients) and growth hormone (4 out of 8 patients). This response could be predicted from the preoperative stimulation tests. Postoperatively the AVP response to osmotic stimuli was impaired in 4 out of 5 patients, although urine volume had returned to normal after a transient polyuric phase. The response of plasma cortisol to ACTH was still adequate but lower than preoperatively.

Experimental gastric dysrhythmias and its correlation with in vivo gastric muscle contractions

AIM: To study the direct correlation between gastric dysrhythmias and in vivo gastric muscle tone.

METHODS: Five healthy dogs were implanted with 4 pairs of electrodes along the greater curvature, with a strain gauge (SG) being sutured parallel to the distal electrodes (2 cm above the pylorus). Intravenous vasopressin was given to induce gastric dysrhythmia. The percentage of regular slow waves and SG energy were calculated.

RESULTS: (1) the regularity of gastric myoelectric activity (GMA) was reduced during and after infusion of vasopressin; (2) SG energy was significantly decreased during the infusion of vasopressin; (3) the decrease in SG energy was well correlated with the reduction in GMA regularity; (4) SG energy was negatively correlated with bradygastria and tachygastria.

CONCLUSION: Vasopressin inhibits gastric contractions and impairs gastric slow waves; gastric dysrhythmias are associated with the reduced antral muscle contractions, and are indicative of antral hypomotility.

Therapeutic potentials of a novel method of dual-pulse gastric electrical stimulation for gastric dysrhythmia and symptoms of nausea and vomiting

BACKGROUND

The aims of this study were to investigate the effects and mechanisms of a novel method of gastric electrical stimulation on the prevention of vasopressin-induced emetic response and gastric dysrhythmias.

METHODS

Fifteen dogs (10 normal, 5 vagotomized) chronically implanted with gastric serosal electrodes were used in a 3-session study (vasopressin, vasopressin plus 2-channel stimulation [DCS], and vasopressin plus dual-pulse stimulation [DPS]).

RESULTS

Vasopressin induced gastric dysrhythmias and motion sickness-like symptoms (P < .05) and these effects were blocked partially with vagotomy. Both methods of DCS and DPS were capable of preventing vasopressin-induced gastric dysrhythmias (P < .05) and motion sickness-like symptoms (P < .05). The antiemetic effects of the proposed methods of DCS and DPS were abolished by vagotomy but their antidysrhythmic effects were not blocked by vagotomy.

CONCLUSIONS

DCS and DPS are able to reduce vasopressin-induced gastric dysrhythmia and symptoms of nausea and vomiting. The vagal pathway is involved in the antiemetic effect but not the antidysrhythmic effect of the proposed methods of stimulation.

Vasopressor hormone response following mesenteric traction during major abdominal surgery

BACKGROUND

We investigated the vasopressor hormone response following mesenteric traction (MT) with hypotension due to prostacyclin (PGI2) release in patients undergoing abdominal surgery with a combined general and epidural anesthesia.

METHODS

In a prospective, randomized, placebo-controlled study we administered 400 mg ibuprofen (i.v.) in 42 patients scheduled for abdominal surgery. General anesthesia was combined with epidural anesthesia (T4-L1). Before as well as 5, 15, 30, 45, and 90 min after MT we recorded plasma osmolality, hemodynamics and measured 6-keto-PGF1 alpha (stabile metabolite of PGI2), TXB2 (stabile metabolite of thromboxane A2) active renin, and arginine vasopressin (AVP) plasma concentrations by radioimmunoassay. Catecholamine levels were assessed by high-pressure liquid chromatography (HPLC) with electrochemical detection.

RESULTS

Following MT, arterial hypotension occurred along with a substantial PGI2 release. This was completely abolished by ibuprofen administration. Although plasma levels of 6-keto-PGF1 alpha (1133 (708) vs. 60 (3) ng/L, median (median absolute deviation), P = 0.0001, placebo vs. ibuprofen) remained significantly elevated, blood pressure was restored within 30 min after MT in the placebo group. At the same point in time plasma concentrations of TXB2 (164 (87) vs. 58 (1) ng/L, P = 0.0001), epinephrine (46 (33) vs. 14 (6) ng/L, P = 0.001), AVP (41 +/- (18) vs. 12 (7) ng/L, P = 0.0004), and active renin (27 (12) vs. 12 (4) ng/L, P = 0.001) were significantly higher in placebo-treated patients.

CONCLUSION

Under combined general and epidural anesthesia arterial hypotension following MT due to endogenous PGI2 release is associated with enhanced release of AVP, active renin, epinephrine and thromboxane A2, presumably contributing to hemodynamic stability within 30 min after MT.

The role of the phrenic nerves in stress response in upper abdominal surgery

Previous studies have failed to demonstrate a block of the endocrine response to upper abdominal surgery by thoracic epidural analgesia. To clarify the bases for this failure, we compared the effects of epidural analgesia of different dermatome levels up to C8-T2 or C3-4. The patients who received general anesthesia alone showed significant increases of adrenocorticotropic hormone (ACTH) and arginine vasopressin (AVP) immediately after skin incision. The patients with C8-T2 blocked developed significant increases in these hormones, not after the skin incision, but after the intraabdominal procedure. Of the eight patients with C3-4 block, six developed no such responses throughout the study period. The responses of oxytocin (OXT) and prolactin (PRL) were more susceptible to epidural analgesia and were blocked at the C8-T2 level. Growth hormone (GH) showed no correlation with surgical procedures and epidural block. These findings indicate that the nociceptive neural information during upper abdominal surgery is conveyed by the sensory fibers included in both the thoracic and lumbar spinal nerves that innervate the abdominal wall and the intraabdominal viscera, and by the phrenic nerves that innervate the diaphragm. The rationale for postulating the involvement of the phrenic nerves can be referred to the embryonal descent of the diaphragm from the C3-5 myotomes that serves as the upper wall of the abdominal cavity.

Neuroendocrine and haemodynamic responses to abdominal aortic cross clamp and release during high-dose opiate-oxygen-isoflurane anaesthesia

The haemodynamic and neuroendocrine responses and beta adrenoceptor distribution associated with aortic cross clamping and release were quantified in 14 patients undergoing elective abdominal aortic aneurysm surgery using a high-dose opiate-oxygen-isoflurane anaesthetic technique. These changes were correlated with neutrophil beta adrenoceptor distribution. Aortic cross clamp application was associated with increased systemic vascular resistance (SVR), and decreased cardiac index (CI). Left ventricular stroke work index remained constant during the period of cross clamp application and following release. Cross clamp release was associated with increased CI and decreased SVR. Plasma cortisol concentrations did not change during the study period. Plasma catecholamine concentrations, although elevated prior to surgery, remained unchanged during aortic cross clamping and following release. The percentage of internalised beta adrenoceptors was elevated before surgery and was unaffected by surgical intervention. This study suggests that a high-dose fentanyl-oxygen-isoflurane anaesthetic technique in a patient population with high circulating catecholamine levels and downregulation of beta adrenoceptors is associated with cardiovascular stability and attenuated neuroendocrine responses.

A study on the vasopressin induced delay in the gastrointestinal transit in mice: possible mechanism of action

The effect of arginine vasopressin (AVP) on the gastrointestinal (GI) transit and its possible mechanism were studied using charcoal meal test in mice. A dose related inhibitory effect was recorded. The effect appears to be independent of the time allowed between AVP administration and testing. The studies on the mechanism reveal that AVP acts without involving V1 and V2 vasopressin receptors. An almost complete reversal of the effect by physostigmine and potentiation by atropine indicate that AVP might act through an inhibition of the release of acetylcholine. However, the neural nicotinic receptors mechanisms do not seem to contribute since hexamethonium failed to modify the AVP action. Further, a partial antagonism by naloxone or prazosin pretreatment indicates that opioid and alpha 1 adrenergic systems also contribute to this action of AVP. However, the effect appears to be independent of alpha 2 and beta adrenergic systems since yohimbine and propranolol failed to modify the same.

Arginine vasopressin inhibits phasic contractions and stimulates giant contractions in monkey colon

Abdominal cramps and urgent defecation are common side effects of clinical doses of arginine vasopressin, indicating that the drug may have stimulating effects on colonic motor activity. Four strain-gauge transducers were implanted on the colon in six monkeys. A blood flow probe was fixed on the inferior mesenteric artery. After a 1-hour control recording, vasopressin, 0.13, 1.3, or 13.0 ng.kg-1.min-1, was infused intravenously for 90 minutes. The frequency of basal colonic contractions was reduced with increasing doses of vasopressin, but their mean amplitude and duration were not altered. Giant migrating contractions associated with defecation were initiated by the highest dose of vasopressin. Atropine had no effect on these giant migrating contractions but completely inhibited normal phasic contractions. Hexamethonium completely inhibited both giant migrating contractions and phasic contractions. Parasympathetic denervation of the colon did not inhibit giant migrating contractions initiated by vasopressin. Our findings suggest that the physiological concentrations of serum vasopressin present perioperatively may transiently inhibit spontaneous colon contractions but are unlikely to be the major cause of postoperative ileus. The giant migrating contractions initiated by vasopressin may account for the defecation associated with pharmacological doses of vasopressin. The initiation of giant migrating contractions by vasopressin may be mediated through a neural pathway.

Changes in cardiovascular homeostasis after injury are mediated by tissue damage and not haemorrhage

During treatment of the injured patient it is assumed that the cardiovascular responses follow recognized physiological principles. Studies in humans have shown that injury causes a profound suppression of arterial baroreflex function which alters the normal relationship between heart rate and blood pressure and casts doubt on this assumption. To investigate the mechanism of baroreflex suppression, we have studied the effects of the two major components of injury, blood loss and tissue damage, on baroreflex function in healthy volunteers. Baroreflex function was assessed using suction stimulation of the carotid sinus. The loss of 500 ml blood had no effect on baroreflex sensitivity. A human laboratory model of tissue injury reduced the ability of the baroreflex to compensate for a rise in blood pressure (P less than 0.05, Wilcoxon signed rank test). We conclude that tissue damage, rather than hypovolaemia, appears to mediate the effect of injury on baroreflex function in the injured. Blockade of neural signals from damaged tissue may have a role in the treatment of injury.

Antidiuretic hormone following surgery in children

We studied 13 children subjected to elective tonsillectomy, 6 of whom (study patients) received supplemental intravenous isotonic saline during and after operation, and 7 of whom (controls) did not. Clinical and biochemical evidence of hypovolaemia was present in the control but not in the study patients. Plasma antidiuretic hormone (ADH) and urine osmolality were higher in controls (p less than 0.005 and p less than 0.05 respectively). Plasma sodium concentration and osmolality were similar in the two groups. We conclude that hypovolaemia is the principal stimulus to ADH release following surgery and that, in addition to replacement of observed losses of blood and other fluids by fluids of appropriate composition, hypovolaemia should be prevented by the administration of maintenance quantities of isotonic fluid, rather than exacerbated by fluid restriction, in patients in whom oral fluid intake is interrupted for more than a brief period. Hypotonic and sodium free fluids should be avoided because of the risk of hyponatraemia.

Postoperative ileus

Postoperative ileus follows any operation. Although worsened if the peritoneum is entered, the length and duration of surgery does not influence the severity of postoperative ileus. Inhibitory alpha 2-adrenergic reflexes with peptidergic afferents contribute to postoperative ileus. Clinically, treatment of ileus centers around symptomatic relief with nasogastric suction. Trials of adrenergic blockade combined with cholinergic stimulation have met with limited success. Prokinetic drugs have not been proved effective in the treatment of this disorder. Two types of ileus exist: postoperative and paralytic. Postoperative ileus resolves spontaneously after two to three days, and probably reflects inhibition of colonic motility. Paralytic ileus is more severe, last more than three days, and seems to represent inhibition of small bowel activity. No discrete structural changes cause postoperative ileus and the role of peptidergic neuronal systems of the enteric nervous system has not been elucidated. Possible central or humoral mechanisms have not been studied extensively. The possible direct inhibition of enteric or spinal nerves by anesthetic agents not cleared from these tissues remains to be studied. Also in need of study is the potential alteration of neurotransmitter receptor activity within the enteric nervous plexus after manipulation of the bowel.

Plasma arginine vasopressin levels and arterial pressure during open heart surgery

A study of plasma arginine vasopressin (AVP) levels and their relation to changes in arterial pressure was undertaken in 13 patients undergoing open heart surgery. Seven of the patients received high doses of intravenous morphine (1 or 2 mg/kg) as part of their anaesthetic, whereas the other six did not. Increases in the AVP levels during cardiopulmonary bypass (CPB) were significant in both groups, but were significantly greater in the patients not receiving morphine (median 86.1 fmol/ml) than in those who did (47.5 fmol/ml). In both groups there was a linear correlation between the natural logarithm of the plasma AVP level and the percentage fall in the mean arterial pressure, although the slope of the relationship was significantly less in the group receiving morphine than in the group not receiving morphine. These results indicate that in patients undergoing cardiac surgery the neuroendocrine reflex control of plasma AVP levels in relation to changes in arterial pressure is intact, but that the sensitivity of the reflex (i.e. the increase in plasma AVP level for a given fall in arterial pressure) is reduced by the administration of high doses of intravenous morphine.

Relative density of urine: methods and clinical significance

The physical properties and chemical composition of urine are highly variable and are determined in large measure by the quantity and the type of food consumed. The specific gravity is the ratio of the density to that of water, and it is dependent on the number and weight of solute particles and on the temperature of the sample. The weight of solute particles is constituted mainly of urea (73%), chloride (5.4%), sodium (5.1%), potassium (2.4%), phosphate (2.0%), uric acid (1.7%), and sulfate (1.3%). Nevertheless, urine osmolality depends only on the number of solute particles. The renal production of maximally concentrated urine and formation of dilute urine may be reduced to two basic elements: (1) generation and maintenance of a renal medullary solute concentration hypertonic to plasma and (2) a mechanism for osmotic equilibration between the inner medulla and the collecting duct fluid. The interaction of the renal medullary countercurrent system, circulating levels of antidiuretic hormone, and thirst regulates water metabolism. Renin, aldosterone, prostaglandins, and kinins also play a role. Clinical estimation of the concentrating and diluting capacity can be performed by relatively simple provocative tests. However, urinary specific gravity after taking no fluids for 12 h overnight should be 1.025 or more, so that the second urine in the morning is a useful sample for screening purposes. Many preservation procedures affect specific gravity measurements. The concentration of solids (or water) in urine can be measured by weighing, hydrometer, refractometry, surface tension, osmolality, a reagent strip, or oscillations of a capillary tube. These measurements are interrelated, not identical. Urinary density measurement is useful to assess the disorders of water balance and to discriminate between prerenal azotemia and acute tubular necrosis. The water balance regulates the serum sodium concentration, therefore disorders are revealed by hypo- and hypernatremia. The disturbances are due to renal and nonrenal diseases, mainly liver, cardiovascular, intestinal, endocrine, and iatrogenic. Fluid management is an important topic of intensive care medicine. Moreover, the usefulness of specific gravity measurement of urine lies in interpreting other findings of urinalysis, both chemical and microscopical.

The neuroendocrinology of physical injury

Physical injury of any sort--accidental injury, burns or elective surgery--provokes an immediate neuroendocrine response. Neural input arising from the cerebral cortex, damaged tissues and receptors detecting fluid loss leads to increased secretion of ACTH, growth hormone, prolactin and vasopressin from the pituitary, and to a general activation of the sympathetic nervous system, with rises in adrenaline and noradrenaline concentrations. Secondary changes include stimulation of cortisol and aldosterone and inhibition of insulin and somatomedin secretion. The glucagon concentration and plasma renin activity may also be increased, either immediately or after a delay. The duration of these responses generally depends upon the severity of the injury and differs considerably between hormones, for reasons that are not understood. The only endocrine changes consistently seen at later times after trauma are an increase in insulin secretion, which supersedes the initial suppression, and decreases in the concentrations of T3 and gonadal steroids. Some of the changes in steroid, thyroid and pancreatic hormones differ temporally or even qualitatively from those of their usual stimuli and are unexplained. The initial neuroendocrine response to injury can be construed as playing a defensive role, but the function of the later changes is not understood; it seems likely that they are adaptive in nature, but the scope for therapeutic intervention remains unclear.

Stimulus for vasopressin release during elective intra-abdominal operations

In 12 patients undergoing an upper abdominal operation, blood pressure and peripheral venous blood samples were taken at intervals throughout the procedure. There was no significant increase in plasma vasopressin concentration after induction of anaesthesia or skin incision; within 3 min of opening the peritoneum and commencing intraperitoneal manipulation there was a highly significant rise (P less than 0.01), maintained with fluctuations until closure of the abdomen. There was no correlation between the changes of blood pressure and those in plasma vasopressin level. In 16 patients undergoing elective cholecystectomy similar observations were made to coincide with events believed, on the basis of the first study, to be related to changes in the concentration of vasopressin. There was a significant rise in vasopressin concentration (P less than 0.01) after incision of the peritoneum, 1 min after the start of intraperitoneal manipulation (P less than 0.01) and after deliberate traction on the stomach (P less than 0.01). During operative cholangiography, when there was no intraperitoneal manipulation, there was a significant fall in the vasopressin level. There was no correlation between changes in vasopressin concentration and blood pressure. These findings indicate that during an abdominal operation nervous stimuli, arising from within the peritoneal cavity and probably mediated via the autonomic system, are an important factor responsible for the increased secretion of vasopressin, and, at least in the absence of major changes in blood pressure and osmolality, the determinant factor.

Vasopressin effects on the small intestine: a possible factor in paralytic ileus?

Experiments were performed on luminally perfused, isolated, canine, jejunal segments in vivo to determine the effects of vasopressin on intestinal motility, myoelectrical activity and absorption. Intravenous vasopressin abolished spike activity and sometimes disrupted slow wave activity. The jejunum became atonic with intraluminal pooling of perfusate. Transit time was prolonged and intestinal absorption of water was decreased. Radionuclide imaging of the intestinal contents showed a doubling of intraluminal volume with vasopressin and confirmed the loss of intestinal motility. It is suggested that the high plasma levels of vasopressin which are known to follow laparotomy may be a factor in the development of postoperative ileus.

Excessive antidiuretic hormone secretion after radical cystectomy

Perioperative plasma antidiuretic hormone (vasopressin) levels were determined in 8 patients undergoing radical cystectomy. Marked elevations of antidiuretic hormone were noted immediately postoperatively in all patients and these levels persisted for 48 hours. Plasma antidiuretic hormone was elevated beyond the physiological levels needed for maintenance of intravascular volume and osmolarity. Excessive antidiuretic hormone secretion is common after radical cystectomy and should be considered in the differential diagnosis of postoperative oliguria in these patients.

Plasma vasopressin and blood pressure. Studies in normal subjects and in benign essential hypertension at rest and after postural challenge

Plasma vasopressin levels were compared in three groups comprising normotensive, mildly hypertensive, and more severely hypertensive patients, both under basal conditions and following an 85 degrees head-up tilt, a stimulus known to provoke vasopressin release in man. Vasopressin levels increased two- to fivefold in all subjects after tilt; however, neither the basal levels nor the maximal levels attained at 45 to 60 minutes after tilt differed in the three groups. These data do not support the postulated role for vasopressin in the causation or perpetuation of non-accelerated essential hypertension in man.

Is "cerebral hyponatraemia" iatrogenic?

Hyponatraemia and hypoosmolality in patients with central nervous system (CNS) disease or trauma are often ascribed to inappropriate secretion of antidiuretic hormone. A "cerebral" aetiology has been postulated. A review of published reports and data from the present study indicate that the increase in antidiuretic activity in these conditions is generally to be expected and is therefore appropriate. It is suggested that the hyponatraemia observed is the result of excessive administration of fluids. In patients with CNS disease or injured brains intravenous fluid intake should be limited to about 1 litre (of 2.5% glucose in 0.45% saline for a 70 kg adult) per day during the acute stress.