Acute change in extracellular fluids associated with major surgical procedures

Determinanten des insensiblen Flüssigkeitsverlustes

Accurate perioperative fluid balance is the basis of a targeted infusion regimen. However, neither the initial status nor perioperative changes of the fluid compartments can be reliably measured in daily routine. In particular, insensible losses are not consistently assessed, so that substitution therapy is generally empirical. The object of this paper is to communicate the scientific data on this topic. Preoperative fasting (10 h) does not per se cause intravascular hypovolemia. In adults, total basal evaporation by way of the skin and airways and of any wounds during major abdominal interventions is usually less than 1 ml/kg/h. An inconstant fluid and protein shift towards the interstitial space perioperatively seems to be associated with hypervolemia, which suggests it should be preventable. The decisive factor in this context seems to be deterioration of the endothelial glycocalyx, whose further patho-physiological impact is currently only partially known. Clinical studies have revealed a link between fluid restriction and improved outcome after major abdominal surgery.

Perioperative fluid management: current consensus and controversies

The scientific knowledge base that supports clinical decisions about perioperative fluid management continues to evolve. However, despite these advancements in the understanding of the physiology of fluid replacement, the definition of ''optimal'' perioperative fluid management remains a matter of clinical judgment. With an appreciation of the many factors, both sensible and insensible, that contribute to changes in blood and extracellular fluid volume during surgery, clinicians have tried to create reproducible and generally applicable formulas for replacement of fluid during surgery. These formulas have been challenged recently by the introduction of new tools for monitoring cardiopulmonary function, by the implementation of monitor-guided protocols for fluid management, and, more recently, by clinical data suggesting that fluid restriction may improve surgical outcomes in some clinical settings. The relative ease of pre-identified fluid replacement protocols is being slowly replaced by data-guided interventions that take into account a variety of factors. Clinicians are therefore required to tailor their fluid replacement strategies based on preoperative patient characteristics, the type of surgery and even the type of anesthetic that is utilized. Some of the benefits of this new approach range from relatively ''minor'' outcomes such as diminished nausea after surgery to preventing postoperative complications such as wound breakdown and cardiopulmonary failure.

Fluid, electrolytes and nutrition: physiological and clinical aspects

Fluid and electrolyte balance is often poorly understood and inappropriate prescribing can cause increased post-operative morbidity and mortality. The efficiency of the physiological response to a salt or water deficit, developed through evolution, contrasts with the relatively inefficient mechanism for dealing with salt excess. Saline has a Na+:Cl-of 1:1 and can produce hyperchloraemic acidosis, renal vasoconstriction and reduced glomerular filtration rate. In contrast, the more physiological Hartmann's solution with a Na+:Cl-of 1·18:1 does not cause hyperchloraemia and Na excretion following infusion is more rapid. Salt and water overload causes not only peripheral and pulmonary oedema, but may also produce splanchnic oedema, resulting in ileus or acute intestinal failure. This overload may sometimes be an inevitable consequence of resuscitation, yet it may take 3 weeks to excrete this excess. It is important to avoid unnecessary additional overload by not prescribing excessive maintenance fluids after the need for resuscitation has passed. Most patients require 2–2·5 litres water and 60–100?mmol?Na\d for maintenance in order to prevent a positive fluid balance. This requirement must not be confused with those for resuscitation of the hypovolaemic patient in whom the main aim of fluid therapy is repletion of the intravascular volume. Fluid and electrolyte balance is a vital component of the metabolic care of surgical and critically-ill patients, with important consequences for gastrointestinal function and hence nutrition. It is also of importance when prescribing artificial nutrition and should be given the same careful consideration as other nutritional and pharmacological needs.

Fluid therapy for the surgical patient

Perioperative fluid therapy is the subject of much controversy, and the results of the clinical trials investigating the effect of fluid therapy on outcome of surgery seem contradictory. The aim of this chapter is to review the evidence behind current standard fluid therapy, and to critically analyse the trials examining the effect of fluid therapy on outcome of surgery. The following conclusions are reached: current standard fluid therapy is not at all evidence-based; the evaporative loss from the abdominal cavity is highly overestimated; the non-anatomical third space loss is based on flawed methodology and most probably does not exist; the fluid volume accumulated in traumatized tissue is very small; and volume preloading of neuroaxial blockade is not effective and may cause postoperative fluid overload. The trials of 'goal-directed fluid therapy' aiming at maximal stroke volume and the trials of 'restricted intravenous fluid therapy' are also critically evaluated. The difference in results may be caused by a lax attitude towards 'standard fluid therapy' in the trials of goal-directed fluid therapy, resulting in the testing of various 'standard fluid regimens' versus 'even more fluid'. Without evidence of the existence of a non-anatomical third space loss and ineffectiveness of preloading of neuroaxial blockade, 'restricted intravenous fluid therapy' is not 'restricted', but rather avoids fluid overload by replacing only the fluid actually lost during surgery. The trials of different fluid volumes administered during outpatient surgery confirm that replacement of fluid lost improves outcome. Based on current evidence, the principles of 'restricted intravenous fluid therapy' are recommended: fluid lost should be replaced and fluid overload should be avoided.

The cellular, metabolic, and systemic consequences of aggressive fluid resuscitation strategies

Increasing evidence has demonstrated that aggressive crystalloid-based resuscitation strategies are associated with cardiac and pulmonary complications, gastrointestinal dysmotility, coagulation disturbances, and immunological and inflammatory mediator dysfunction. As large volumes of fluids are administered, imbalances in intracellular and extracellular osmolarity occur. Disturbances in cell volume disrupt numerous regulatory mechanisms responsible for keeping the inflammatory cascade under control. Several authors have demonstrated the detrimental effects of large, crystalloid-based resuscitation strategies on pulmonary complications in specific surgical populations. Additionally, fluid-restrictive strategies have been associated with a decreased frequency of and shorter time to recovery from acute respiratory distress syndrome and trends toward shorter lengths of stay and lower mortality. Early resuscitation of hemorrhagic shock with predominately saline-based regimens has been associated with cardiac dysfunction and lower cardiac output, as well as higher mortality. Numerous investigators have evaluated potential risk factors for developing abdominal compartment syndrome and have universally noted the excessive use of crystalloids as the primary determinant. Resuscitation regimens that cause early increases in blood flow and pressure may result in greater hemorrhage and mortality than those regimens that yield comparable flow and pressure increases late in resuscitation. Future resuscitation research is likely to focus on improvements in fluid composition and adjuncts to administration of large volume of fluid.

Randomized clinical trial assessing the effect of Doppler-optimized fluid management on outcome after elective colorectal resection

BACKGROUND

Protocolized fluid administration using oesophageal Doppler monitoring may improve the postoperative outcome in patients undergoing surgery.

METHODS

A total of 108 patients undergoing elective colorectal resection were recruited into a double-blind prospective randomized controlled trial. An oesophageal Doppler probe was placed in all patients. The control group received perioperative fluid at the discretion of the anaesthetist, whereas the intervention group received additional colloid boluses based on Doppler assessment. Primary outcome was length of postoperative hospital stay. Secondary outcomes were morbidity, return of gastrointestinal function and cytokine markers of the systemic inflammatory response. Standard preoperative and postoperative management was used in all patients.

RESULTS

Demographic and surgical details were similar in the two groups. Aortic flow time, stroke volume, cardiac output and cardiac index during the intraoperative period were higher in the intervention group (P<0.050). The intervention group had a reduced postoperative hospital stay (7 versus 9 days in the control group; P=0.005), fewer intermediate or major postoperative complications (2 versus 15 percent; P=0.043) and tolerated diet earlier (2 versus 4 days; P=0.029). There was a reduced rise in perioperative level of the cytokine interleukin 6 in the intervention group (P=0.039).

CONCLUSION

A protocol-based fluid optimization programme using intraoperative oesophageal Doppler monitoring leads to a shorter hospital stay and decreased morbidity in patients undergoing elective colorectal resection.

Fluid management of patients undergoing abdominal surgery – more questions than answers *

The 'wet vs. dry' philosophy in patients undergoing abdominal surgery is a subject of substantial debate. It has been suggested that restricting fluid input would significantly reduce complications and improve outcome following abdominal surgery. Keeping the patients dry may be a two-edged sword because the resulting hypovolaemia may result in compromised organ perfusion and poor tissue oxygenation. A review of the literature from 1990 to 2004 revealed that only very few studies on this subject have been published. Unfortunately, most of the 'dry'-supporting studies used fixed amounts of volume instead of a fluid concept adapted to the patients' need ('goal-directed') and there is no generally accepted definition of 'restricted', 'dry' or 'overload'. Not only the amount but also the kind of administered fluid appears to be important. Current evidence indicates that using crystalloids exclusively may cause overloading of the interstitial compartment with considerable negative sequelae, whereas using colloids may improve microperfusion and tissue oxygenation. This review shows that the meagre literature on a restricted volume replacement strategy in abdominal surgery patients cannot clearly support the 'dry' approach. Further well-performed studies are necessary to elucidate the ideal amount and type of fluid replacement and determine how to guide fluid therapy.

Hemorrhage and operation cause a contraction of the extracellular space needing replacement—evidence and implications? A systematic review

BACKGROUND

Hemorrhagic hypotension or operative trauma is believed to cause a contraction of the extracellular fluid volume (ECV) beyond the measured fluid losses. The aim of this review was to explore the evidence and implications of ECV loss.

METHODS

We performed a systematic review of original trials measuring ECV changes during hemorrhage or operation. PubMed, relevant periodicals, and reference lists were searched until no further original articles appeared. The quality of both the scientific and the technical methods of the trials were evaluated.

RESULTS

A total of 61 original articles were found. The pattern appeared that all investigators reporting shock or operation to cause a disparate reduction of the ECV had measured the ECV with the same method. The ECV was calculated from very few blood samples that were withdrawn after 20 to 30 minutes of equilibration of a tracer (the (35)SO(4)-tracer). Trials calculating ECV from multiple blood samples, after longer equilibration times, or using other tracers did not find a contraction of the ECV. On the contrary, trials using a bromide tracer found the ECV to be expanded after operation.

CONCLUSIONS

The evidence supporting the idea that hemorrhage or operation cause a contraction of the ECV is weak, and probably a result of flawed methodology.

Intraoperative fluid restriction improves outcome after major elective gastrointestinal surgery

Fluid therapy is one of the most controversial topics in perioperative management. There is continuing debate with regard to the quantity and the type of fluid resuscitation during elective major surgery. However, there are increasing reports of perioperative excessive intravascular volume leading to increased postoperative morbidity and mortality. Recent evidence suggests that judicious perioperative fluid therapy improves outcome after major elective gastrointestinal surgery. The observed benefits may not be solely attributable to crystalloid restriction but also to the use of colloids instead. Some clinically useful guidelines based on the studies discussed in this review include avoidance of deep general anesthesia and elimination of preload for patients who receive epidural analgesia. A balanced approach to fluid management is recommended, with colloids administered to provide hemodynamic stability and maintain urine output of 0.5 mL x kg(-1) x h(-1) and crystalloids administered only for maintenance. In addition, blood loss may be replaced with colloid on a volume-to-volume basis. Furthermore, predetermined algorithms that suggest replacement of third space losses and losses through diuresis are unnecessary. Significant reduction in crystalloid volume can be achieved without encountering intraoperative hemodynamic instability or reduced (i.e., < 0.5 mL x kg(-1) x h(-1)) urinary output just by avoiding replacement of third space losses and preloading. Finally, there is a need for well-controlled studies in a well-defined patient population using clear criteria or end-points for perioperative fluid therapy.

Perioperative fluid management and clinical outcomes in adults

The administration of IV fluid to avoid dehydration, maintain an effective circulating volume, and prevent inadequate tissue perfusion should be considered, along with the maintenance of sleep, pain relief, and muscular relaxation, a core element of the perioperative practice of anesthesia. Knowledge of the effects of different fluids has increased in recent years, and the choice of fluid type in a variety of clinical situations can now be rationally guided by an understanding of the physicochemical and biological properties of the various crystalloid and colloid solutions available. However, there are few useful clinical outcome data to guide this decision. Deciding how much fluid to give has historically been more controversial than choosing which fluid to use. A number of clinical studies support the notion that an approach based on administering fluids to achieve maximal left ventricular stroke volume (while avoiding excess fluid administration and consequent impairment of left ventricular performance) may improve outcomes. In this article, we review the available fluid types and strategies of fluid administration and discuss their relationship to clinical outcomes in adults.

Effects of 7.5% hypertonic saline on fluid balance after radical surgery for gastrointestinal carcinoma

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.

Patterns and clinical outcomes associated with routine intravenous sodium and fluid administration after colorectal resection

Excess intravenous water and sodium may be associated with postoperative complications and an adverse outcome. However, the effect of the magnitude of the surgery on such a relation has not been studied. This study assesses current practice in intravenous fluid and sodium administration after colonic and rectal resection and its relation to the postoperative outcome. A series of 100 consecutive patients undergoing elective colonic (n = 44) or rectal resection (n = 56) were included in a retrospective case-cohort study. The volumes of water and sodium from intravenous fluid and antibiotic administration on the day of surgery and the next 5 days were recorded together with the clinical outcome. The mean +/- SEM fluid and sodium administration on the day of operation was greater after rectal than colonic resection (4.6 +/- 0.2 vs. 3.6 +/- 0.2 liters and 507 +/- 34 vs. 389 +/- 22 mmol, respectively (p < 0.05). The mean +/- SEM rate of daily fluid and sodium administration for the 5 subsequent days was greater following rectal than colonic resection (2.1 +/- 0.1 vs. 1.8 +/- 0.1 L/day and 155 +/- 8.7 vs. 128 +/- 8.0 mmol/day; p < 0.05). For all resections, there were no differences in fluid and sodium administration on the day of surgery in patients with or without postoperative complications. During the subsequent 5 days, patients with complications after colonic resection had a higher postoperative mean rate of intravenous sodium administration than those who did not (149 +/- 12 vs. 115 +/- 10 mmol; p < 0.05). A similar pattern was not observed following rectal resection. Current postoperative intravenous fluid prescription delivers approximately 2 liters of fluid and 140 mmol of sodium per day. Complications after colonic, but not rectal, resection are associated with more early postoperative daily intravenous sodium administration. Because colonic resection poses less of a physiologic insult than rectal resection, the overall outcome in the former group may be more sensitive to the interplay between fluid and sodium overload and patient co-morbidity.

[Hyperchloremic acidosis druing plasma volume replacement]

OBJECTIVES

Review of the physiological and clinical consequences of hyperchloraemic acidosis observed during plasma volume replacement using crystalloids and colloids.

DATA SOURCES

Data were searched in the Medline database after 1990 using the following key words: metabolic acidosis, crystalloids, colloids, albumin, gelatin, hydroxyethyl starch.

DATA EXTRACTION

Publications before 1990 were selected for their historical value. Most of articles published after 1990 and all types including case report were accepted.

DATA SYNTHESIS

Large volume infusion of isotonic solution can cause hyperchloraemic acidosis. Colloid plasma substitutes using saline solvent may be responsible for the same kind of acidosis with acidaemia. The anion gap is not modified in this case because of chloride increase. Physiological mechanism may be described using the Henderson-Hasselbach equation or the strong ion difference decrease (Stewart concept). Excessive chloride infusion is a major factor in this acid-base disorder and the term hyperchloraemic acidosis should be preferred to dilutional acidosis. When perioperative acidosis occurs, careful and complete analysis of acid-base disturbance should be made. The association of a normal anion gap, normal lactatemia, hyperchloraemia and acidaemia does not need specific treatment. Acidosis corrects spontaneously and slowly following chloride normalization. But any factor that may increase acidosis should be avoided.

CONCLUSION

The use of balanced solution like lactated-Ringer solution instead of isotonic saline solution for fluid resuscitation, except for specific contra-indication as intracranial hypertension, may avoid hyperchloraemic acidosis. Potential risk of this acidosis led to the conception of a new colloid using balanced crystalloids solution as the solvent (Hextend).

Choice of fluid for resuscitation of septic shock

OBJECTIVES

To determine current practice in choice of fluid resuscitation in children following publication of a systematic review that demonstrated a higher mortality in patients treated with human albumin solution.

METHODS

A descriptive telephone and postal questionnaire survey directed at the on call paediatric registrar, lead clinician for paediatrics and the paediatric pharmacist at each of 33 hospitals within the Greater London area. The study was coordinated by the Paediatric Intensive Care Unit at St Mary's Hospital, London. The questionnaire was designed to assess whether a protocol/guidelines existed for resuscitation fluid in children with septic shock; whether the participants were aware of the systematic review and if so, had it changed clinical practice. The word "protocol" was used in its broadest sense to include guideline and policy.

RESULTS

11 hospitals had guidelines for fluid resuscitation of septic shock in children. These varied greatly: only three gave clear instructions of which fluid to use and how to use it. Choice of fluid varied widely and there was wide discrepancy between consultant's and registrar's choice of fluid. The systematic review had lead to a change in policy in two thirds of respondents.

CONCLUSION

It is apparent that few paediatric departments have a written protocol or guidelines for the management of septic shock that is accessible to all those concerned in the acute treatment of seriously ill children. The systematic review into choice of fluid has had an impact on clinical practice with no data regarding whether this is in the patient's best interests.

Intraoperative fluid management--what and how much?

An approach to intraoperative fluid management based on a monitored physiologic application of the Starling principles of cardiac function is recommended to individualize therapy to optimize hemodynamic function and tissue perfusion. The complexity of intraoperative fluid administration, beginning with preoperative cardiovascular function followed by innumerable intraoperative considerations, including anesthetic pharmacology, positive pressure ventilation, operative site, and surgical technique may lead to serious intraoperative and postoperative complications. Emphasis must be given to intraoperative fluid shifts resulting in hidden fluid loss and intravascular hypovolemia that must be replaced. Explanations for this fluid redistribution have included tissue trauma, endotoxemia, and proinflammatory cytokines with resultant increased capillary permeability.

A prospective randomized double-blinded study of the effect of intravenous fluid therapy on adverse outcomes on outpatient surgery

This study investigated the impact of perioperative fluid status on adverse clinical outcomes in ambulatory surgery. Two hundred ASA grade I-III ambulatory surgical patients were prospectively randomized into two groups to receive high (20 mL/kg) or low (2 mL/kg) infusions of isotonic electrolyte solution over 30 min preoperatively. A standardized balanced anesthetic was used. A minimal amount of fluid was given during the intraoperative and postoperative periods. Adverse outcomes were assessed by an investigator blinded to the fluid treatment group at 30 and 60 min after surgery, at discharge, and the first postoperative day. The incidence of thirst, drowsiness, and dizziness was significantly lower in the high-infusion group at all intervals. We recommend perioperative hydration of 20 mL/kg for patients undergoing general anesthesia for short ambulatory surgery.

[Oncotic pressure and hemodilution]

The appropriate fluid therapy in neurosurgical patients remains an area of disagreement between neurosurgeons and anaesthesiologists. Fluid restriction has long been practiced in patients with brain pathology, in order to reduce or prevent the formation of cerebral oedema. This grows from a fear that rapid administration of fluids, particularly noncolloidal fluids, can enhance cerebral oedema, although there is a lack of experimental evidence to substantiate this belief. On the other hand, fluid restriction can lead to relative hypovolaemia, causing haemodynamic instability during anaesthesia and influence defavourably cerebral perfusion. The appropriate fluid management of patients with brain pathology requires a careful review of the Starling's law and a clear understanding of osmolality, oncotic pressure (OP) and the nature of the blood-brain barrier (BBB). The Starling equation of ultrafiltration states that the net movement of fluid between the intra- and extravascular compartments is the result of the summated influences of the pressure gradients (hydrostatic pressure, OP, and osmotic pressure) between those compartments and the properties of the barriers (capillary endothelium) that separate them. In most peripheral tissues this barrier is freely permeable to small molecules and ions and net fluid movement depends on intravascular hydrostatic pressure and OP. Under normal circumstances, intraluminal hydrostatic pressure is higher than interstitial pressure, favouring water egress. By contrast, intraluminal OP is higher than interstitial OP, favouring water retention. These forces do not balance exactly, and fluid accumulation is prevented by the lymphatics. If this net movement exceeds the capacity of the lymphatic clearance mechanisms, fluid accumulates, which is the definition of oedema.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous fluid administration and urine output during radical neck surgery

This study examines perioperative urine output (UO) and hemodynamics in 24 patients who underwent radical head and neck surgery. The hypothesis tested was that "UO was not important in patients with normal renal function as long as hemodynamics were maintained." Intraoperatively, a "wet" group (13 patients) had generous amounts of intravenous (IV) fluid administered during surgery receiving 1,018 +/- 58 mL.h-1. The other "dry" group (11 patients) had fluids restricted to 426 +/- 23 mL.h-1. The intraoperative UOs for the wet and dry groups were 1.33 +/- 0.27 and 0.39 +/- 0.10 mL.kg-1 x h-1, respectively (p < 0.05). Postoperatively, the UOs for the wet and dry groups were 1.9 +/- 0.3 and 1.1 +/- 0.1 mL.kg-1 x h-1, respectively (p < 0.05). Perioperatively, there were no statistically significant differences between groups in systemic or pulmonary hemodynamics. Postoperatively, ordinary indices of renal function remained normal in both groups. We conclude that intraoperative oliguria due to moderate fluid restriction is not detrimental to renal outcome as long as systemic hemodynamics are maintained. Furthermore, not only does this relatively "dry" status not compromise hemodynamics, it affords the patient other benefits.

Fluid and electrolyte management in the pediatric surgical patient

The following is a quick guide to the perioperative fluid program discussed 1. Always assess the state of fluid repletion in any patient presenting for surgical management (Note: This does not necessarily mean operative management). 2. If the patient is hypovolemic or if there is the possibility of hypovolemia and you are uncertain, restore volumes equal to 25% of the patient's blood volume with a fluid push made up of an osmotically active electrolyte solution modified for the additional requirements of red cell carrying capacity or clotting factors. If this results in a urine output and correction of hypoperfusion or hypotension, maintain an increased fluid administration program until a stable urine output and good perfusion are achieved. If the patient is normovolemic at the time of presentation, particularly if the patient is having an elective operative procedure and does not have an intravenous line in place, calculate the insensible losses that will occur during the time of fluid restriction before surgery and correct at least 50% of these during the operative procedure. 3. Develop the postoperative fluid program as a combination of 24-hour insensible loss replacement (maintenance fluid), restoration of measured losses, and an estimate (guess) as to the volume requirements for third-space fluid shifts. Restore blood losses if appropriate or administer additional volumes of balanced electrolyte solution at a 3-to-1 ratio to replace measured blood loss. 4. Total the insensible loss measurement, the measured losses, and the estimate of third-space requirement and divide this volume by 24 to get an initial hourly fluid administration rate. 5. Select the most osmotically active fluid that you intend to use and administer it first at the calculated rate. Carefully monitor the patient's urine output. 6. Increase or decrease the fluid administration rate to bring the hourly urine output within the guidelines for the appropriate hourly urine output (milliliters) for the particular patient based on size (kilograms). 7. When the urine output falls within the appropriate range, maintain that rate of fluid administration, and recalculate the volumes required because of insensible loss, measured loss, and third-space shifts by subtracting the amount of fluid already administered from the volume that will be required in the remainder of the 24 hours; this will yield the volumes of additional maintenance, measured loss, and third-space fluids that will make up the remainder of the fluids needed for the 24 hours.(ABSTRACT TRUNCATED AT 400 WORDS)

Postoperative seizures

Two young patients with extensive ulcerative colitis were treated with oral steroids and developed seizures between 36 and 72 h after emergency colectomy. These cases highlight the problem of postoperative seizures, related to previous steroid administration, fluid overload, postoperative hypertension and biochemical abnormalities.

Assessment of changes in body water by bioimpedance in acutely ill surgical patients

OBJECTIVE

To evaluate the relationship between changes in body bioelectrical impedance (BI) at 0.5, 50 and kHz and the changes in body weight, as an index of total body water changes, in acutely ill surgical patients during the rapid infusion of isotonic saline solution.

DESIGN

Prospective clinical study.

SETTING

Multidisciplinary surgical ICU in a university hospital.

PATIENTS

Twelve male patients treated for acute surgical illness (multiple trauma n = 5, major surgery n = 7).

SELECTION CRITERIA

stable cardiovascular parameters, normal cardiac function, signs of hypovolemia (CVP < or = 5 mmHg, urine output < 1 ml/kg x h).

INTERVENTIONS

After baseline measurements, a 60 min fluid challenge test was performed with normal saline solution, 0.25 ml/kg/min [corrected].

MEASUREMENTS AND RESULTS

Body weight (platform digital scale), total body impedance (four-surface electrode technique; measurements at 0.5, 50 and 100 kHz) and urine output. Fluid retention induced a progressive decrease in BI at 0.5, 50 and 100 kHz, but the changes were significant for BI 0.5 and BI 100 only, from 40 min after the beginning of the fluid therapy onwards. There was a significant negative correlation between changes in water retention and BI 0.5, with individual correlation coefficients ranging from -0.72 to 0.95 (p < 0.01-0.0001). The slopes of the regression lines indicated that for each kg of water change, there was a mean decrease in BI of 18 ohm, but a substantial inter-individual variability was noted.

CONCLUSION

BI measured at low frequency can represent a valuable index of acute changes in body water in a group of surgical patients but not in a given individual.

Early inappropriate secretion of antidiuretic hormone after trans-sphenoidal pituitary adenomectomy

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a rare but life-threatening complication of trans-sphenoidal pituitary adenomectomy. It has previously only been described as a late phenomenon. We report an early presentation within the first week. The pathophysiology, clinical features and treatment are discussed.

Intravenous fluid load and recovery. A double-blind comparison in gynaecological patients who had day-case laparoscopy

The effect of intra-operative fluid and dextrose administration upon recovery was tested in a randomised, double-blind trial. Three groups of 25 patients, each undergoing laparoscopic examination as day cases, were studied. The two groups who received fluid (20 ml/kg compound sodium lactate solution) showed significant improvement (p less than 0.05) in the variables that reflected hydration. The fluid group who also received dextrose (1 g/kg) exhibited further significant improvement. Intra-operative fluid and dextrose administration appears to confer some benefit upon recovery in patients who have minor surgery.

Preoperative characteristics predicting intraoperative hypotension and hypertension among hypertensives and diabetics undergoing noncardiac surgery

We prospectively studied patients with hypertension and diabetes undergoing elective noncardiac surgery with general anesthesia to test the hypothesis that patients at high risk for prognostically significant intraoperative hemodynamic instability could be identified by their preoperative characteristics. Specifically we hypothesized that patients with a low functional capacity, decreased plasma volume, or significant cardiac comorbidity would be at high risk for intraoperative hypotension and those with a history of severe hypertension would be at risk for intraoperative hypertension. Patients who had a preoperative mean arterial pressure (MAP) greater than or equal to 110, a walking distance of less than 400 m, or a plasma volume less than 3000 cc were at increased risk of intraoperative hypotension (i.e., more than 1 hour of greater than or equal to 20 mmHg decreases in the MAP). Hypotension was also more common among patients having intra-abdominal or vascular surgery, and among those who had operations longer than 2 hours. Patients older than 70 years or with a decreased plasma volume were at increased risk of having more than 15 minutes of intraoperative elevations of greater than or equal to 20 mmHg over the preoperative MAP in combination with intraoperative hypotension; this was also more common when surgery lasted more than 2 hours. Patients who had intraoperative hypotension tended to have an immediate decrease in MAP at the onset of anesthesia and were often purposefully maintained at MAPs less than their usual level during surgery with fentanyl and neuromuscular blocking agents. Patients who had intraoperative hyper/hypotension tended to have repeated elevations in MAP above their preoperative levels during the course of surgery, and such elevations precipitated interventions with neuromuscular blocking agents and/or fentanyl. Neither pattern was more common among patients who developed net intraoperative negative fluid balances. Both hypotension and hyper/hypotension were associated with increased renal and cardiac complications after operation. Patients with cardiac disease, especially diabetics, and those with negative fluid balances also had increased complications. Preoperative characteristics influence the susceptibility to intraoperative hypotension and hypertension, which are related to postoperative complications.

Post-traumatic changes in, and effect of colloid osmotic pressure on the distribution of body water

The aim of this study was to define the post-traumatic changes in body fluid compartments and to evaluate the effect of plasma colloid osmotic pressure (COP) on the partitioning of body fluid between these compartments. Forty-two measurements of plasma volume (green dye), extracellular volume (bromine), and total body water (deuterium) were done in ten traumatized patients (mean Injury Severity Score, ISS, = 34) and 23 similar control studies were done in eight healthy volunteers who were in stable fluid balance. Interstitial volume, intracellular volume, and blood volume were calculated from measured fluid spaces and hematocrit; COP was directly measured. Studies in volunteers on consecutive days indicated good reproducibility, with coefficients of variation equal to 3.5% for COP, 6.3% for plasma volume, 4.5% for extracellular volume, and 4.9% for total body water. COP values extended over the entire range seen clinically, from 10 to 30 mmHg. Interstitial volume was increased by 55% in patients, but intracellular volume was decreased by 10%. We conclude (1) that posttraumatic peripheral edema resulting from hemodilution is located in the interstitial compartment, with no intracellular space expansion; and (2) that interstitial volume, but not intracellular volume, is closely related to plasma COP.

Intraoperative management of abdominal aortic aneurysms. The anesthesiologist's viewpoint

Factors that influence the choice of anesthetic, monitoring methods, and fluid management for aneurysm repair are reviewed, with particular attention to epidural anesthesia and analgesia and the pulmonary artery catheter. Management of bleeding, renal preservation, temperature control, and myocardial ischemia are discussed, and special anesthetic issues associated with ruptured aneurysms and juxtarenal and suprarenal surgery are summarized.

Decrease in plasma volume from intraabdominal trauma in rats

Intraabdominal surgery tends to lower circulating blood volume by mechanisms unrelated to bleeding. This phenomenon was investigated in chloralose anesthetized rats. Plasma volume was determined with radiolabelled albumin. Animals were subjected to a standardized abdominal trauma, eliciting minimal bleeding and evaporation, and others served as controls. The trauma decreased plasma volume and increased hematocrit significantly, whereas the plasma concentration of labelled albumin followed a similar time course in traumatized animals and in controls. It is concluded that experimental abdominal trauma may decrease blood volume by a loss of fluid with virtually the same albumin concentration as that of plasma.

Intravenous fluids in minor gynaecological surgery. Their effect on postoperative morbidity

Postoperative morbidity was assessed in 100 patients who underwent minor gynaecological procedures. Fifty patients received intra-operative crystalloid (1000 ml compound sodium lactate solution) and the remaining fifty none. Identical short-acting intravenous anaesthetic techniques were used in both groups. There was no statistically significant difference between the groups in symptoms of nausea, vomiting, headache and drowsiness within the first 6 hours after operation. Patients who received intra-operative fluids exhibited a decreased incidence of dizziness within the first 6 hours and a decreased incidence of nausea when questioned at 3 days compared with those who did not receive any fluid; the difference was statistically significant.