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Department of Anesthesiology and Pain Management, University of Texas Southwestern Medical Center
Address correspondence and reprint requests to Girish P. Joshi, MB, BS, MD, FFARCSI, Department of Anesthesiology and Pain Management, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 753909068. Address e-mail to girish.joshi{at}utsouthwestern.edu.
| Abstract |
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| Introduction |
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However, the doctrine of Shires still dictates current perioperative fluid therapy (6,7). Current intraoperative fluid therapy is guided by algorithms based on the assumption that preoperative deficits, maintenance requirements, third space losses, and blood loss are to be replaced by crystalloids using an mL · kg1 · h1 formula (8). However, the bases of such formulae are being questioned (1). For example, the studies suggesting the replacement of third space losses (1) and amount of crystalloid required to replace blood loss (i.e., replacement of blood loss by thrice the amount of crystalloid) may be flawed (9). Furthermore, several reports of significant deleterious effects of overhydration with crystalloids (1013) question this practice. This article will briefly review several studies reporting improved outcome with judicious intraoperative fluid administration during major elective gastrointestinal surgery (1418).
| Excessive Perioperative Fluid Therapy |
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The consequences of excessive intravascular volume are well recognized (6). It increases demands on cardiac function and may result in myocardial dysfunction and associated morbidity (6). In a provocative article, Arieff (10) analyzed 13 generally healthy patients (average age, 38 yr; no comorbidities) with fatal postoperative pulmonary edema. He concluded that routinely used end-points (e.g., heart rate, mean arterial blood pressure, central venous pressure, and urine output) neither detect nor predict impending pulmonary edema. In addition, he also suggested that pulmonary edema can occur when the net fluid retention exceeds 67 mL · kg1 · day1. Arieff (10) then reviewed the records of patients undergoing major surgery at two university medical centers over a period of 1 yr. He found that the overall incidence of postoperative pulmonary edema was 7.6% (n = 612) with mortality of 11.9%. Of these, 2.6% (n = 204) had no comorbidities, suggesting that the most likely cause of postoperative pulmonary edema in these patients was perioperative excessive intravascular volume (the net fluid retention in these patients was 90 ± 36 mL · kg1 · day1).
Increased extravascular lung water from excessive intravascular volume may predispose patients to pneumonia and respiratory failure (6). Holte et al. (11) found that administration of 40 mL/kg lactated Ringers solution (which is an average amount of fluids used in moderate surgical procedures) significantly reduced pulmonary function in healthy volunteers (with average age 63 yr). Moller et al. (12) reported that a positive fluid balance exceeding 4000 mL was associated with an increased risk of postoperative pulmonary complications and in-hospital mortality after pneumonectomy. In addition, excessive intravascular volume increases the excretory work of the kidneys (6). It can lead to edema of the gut, which may inhibit gastrointestinal motility and prolong postoperative ileus and intolerance for enteric alimentation (6). The potential for bacterial translocation and development of sepsis and multiorgan failure is also increased. An even more severe complication is the occurrence of abdominal compartment syndrome (i.e., increase of intraabdominal pressure) leading to physiological effects such as respiratory and renal dysfunction (13). Excessive crystalloids can also cause coagulation abnormalities (6). Increased cutaneous edema may decrease tissue oxygenation, which can lead to delayed wound healing (6). Of note, most complications of excessive intravascular volume occur during the period from the third to the fifth postoperative day, when fluid is mobilized into the vascular space and the kidneys cannot diurese this extra fluid (6).
| Liberal Versus Restricted Perioperative Fluid Administration |
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An observational case series of 56 consecutive patients undergoing near-total esophagectomy evaluated the benefits of a standardized multimodal anesthetic management, which included intraoperative fluid restriction, smaller (<1 MAC) concentrations of inhaled anesthetics, minimal opioids (fentanyl
250 µg), and intraoperative epidural lidocaine 1.5%2% (15). The mean surgical duration was 6.5 h and the mean blood loss was 175 mL (maximum, 400 mL). No predetermined algorithm for fluid administration was used. All patients received 500 mL of 5% albumin. Intraoperative fluids were administered to maintain adequate hemodynamics (systolic blood pressure within 20% of baseline) and urinary output of 0.3 to 0.5 mL · kg1 · h1. Although no preload was used before epidural analgesia, 20%25% of total intraoperative crystalloid volume was administered in the first 3045 min. The median crystalloid (lactated Ringers solution) administration was 650 mL/h (mean, 661 ± 194 mL/h). Interestingly, hemodynamic stability was not difficult to maintain despite intraoperative fluid restriction. In addition, the authors were able to maintain a mean intraoperative urinary output of 0.57 mL · kg1 · h1. There was no case of renal failure. All patients were tracheally extubated in the operating room. Postoperatively patients received 11.5 mL · kg1 · h1 of lactated Ringers solution. The median length of ICU stay was 1 day and patients ambulated early (median, 1.6 days; range, 03 days). The authors concluded that the improved outcome may have been associated with use of the multimodal approach, which included use of smaller concentrations of inhaled anesthetics, judicious use of crystalloids, use of colloids, and acceptance of a lower urinary output (<0.5 mL · kg1 · h1), and use of patient-controlled epidural analgesia (14). The authors report similar outcomes in 250 near-total esophagectomies. The limitations of this study include its observational, non-randomized case series design and small sample size. A randomized, double-blind, controlled trial of intraoperative fluid restriction is warranted to further validate the findings of this study.
Lobo et al. (16) performed a prospective trial in which otherwise normal patients (n = 20) undergoing colon surgery were randomized to receive either standard fluid therapy (
3 L crystalloids, 1L 0.9% saline, and 2 L 5% dextrose) or restricted fluid therapy (
2 L crystalloid, 0.5 L 0.9% saline, and 1.5 L 5% dextrose or 2 L 0.9% saline/0.18% dextrose) in the postoperative period. Although intraoperative fluid administration was not controlled, both groups received similar amount of crystalloids (mean, 2800 mL). The duration of surgery was short (<2 h) and the mean blood loss was 275 mL (no intraoperative blood transfusion was required). Urine output did not differ between the groups. Patients in the restricted group had statistically significantly shorter gastric emptying times for both liquids and solids and drank significantly more fluids. Compared with the restricted group, the median passage of flatus was 1 day later, median passage of stools was 2.5 days later, and median postoperative hospital stay 3 days longer in the standard group; these were statistically significantly differences (15). The patients in the standard practice group had a more frequent incidence of complications (e.g., peripheral edema, hyponatremia, vomiting, confusion, and readmission within 30 days).
A recent randomized, observer-blinded, controlled trial evaluated the effects of standard and restricted fluid therapy on complications after colorectal surgery (17). Anesthetic technique included epidural analgesia combined with general anesthesia. Patients (n = 72) in the standard fluid therapy group received 500 mL saline 0.9% for the fasting period and 500 mL hydroxyethyl starch 6% in normal saline as preload before epidural analgesia and saline 0.9% (7 mL · kg1 · h1 for first hour, 5 mL · kg1 · h1 second and third hours, and 3 mL · kg1 · h1 thereafter) to replace third space losses. Blood loss was replaced with 10001500 crystalloid mL for the first 500 mL and hydroxyethyl starch 6% for any additional loss (17).
Patients (n = 69) in the restricted fluid therapy group received 500 mL glucose 5% in water for the fasting period, no preload before epidural analgesia, and no replacement for third space loss (17). Blood loss was replaced with hydroxyethyl starch 6% on a volume-to-volume basis after 500 mL blood lost. Diuresis was not replaced. In both groups a hematocrit was maintained between 25% and 35% (higher limits in patients with cardiovascular disease). If the maximum dose of hydroxyethyl starch 6% (i.e., 33 mL · kg1 · day1) was achieved, albumin 5% was administered. Patients in both the groups received vasoactive drugs (ephedrine and/or dopamine) to achieve a mean arterial blood pressure of more than 60 mm Hg (17).
The postoperative fluid regimen in the standard group was 10002000 mL crystalloid. On the other hand, the restricted group received 1000 mL of glucose 5% (with potassium if needed) and hydroxyethyl starch 6% for volume-to-volume loss through drains. A weight increase exceeding 1 kg was treated with furosemide. Postoperative hypotension or small urinary output (<0.5 mL · kg1 · h1) was treated according to standard practice (e.g., change epidural analgesic dose, vasoactive therapy when appropriate, and fluid therapy). Feeding (through nasogastric tube) commenced 4 h postoperatively and all patients were encouraged to eat and drink from 4 h after surgery (17).
IV fluid administration was significantly less in the fluid restricted group on the day of surgery (mean, 2740 mL versus 5388 mL) and on day 1 postoperatively (mean, 500 mL versus 1500 mL). Both groups received similar volumes of hydroxyethyl starch 6%; thus the differences were attributable to differences in crystalloid administration (17). A 34 kg increase in body weight occurred over the first 2 days. The number of patients with postoperative complications was significantly reduced in the fluid restricted group (33% versus 51% in the standard therapy group, P = 0.013). Patients with complications had an average of 1.2 complications in the restricted group and 2.1 complications in the standard group. A dose-response relation was observed between complications and increasing IV fluid volumes as well as increasing body weight. There were no deaths in the fluid restricted group whereas 4 patients (4.7%) died in the standard group (causes of death included pulmonary edema in 2 patients, pneumonia with septicemia, and pulmonary embolism). The urinary output was larger and the serum creatinine was lower in the standard group on the day of surgery, but there was no difference thereafter. Only one patient (in the standard group) had renal failure after sepsis. The authors concluded that restricted fluid administration by eliminating preloading and replacement for "third spacing" and maintenance of body weight reduced postoperative complications after colorectal surgery (17). Although this was a well-designed study, the limitations include more proximal anastomoses and more smokers in the restricted group, which may have favored this group with respect to anastomotic leaks. There may have been some "learning bias," as there was a tendency towards fluid restriction even in the standard group, which was likely an effect of the lack of blinding of the anesthesiologists and surgeons. Additional studies evaluating different surgical procedures and fluid therapies are necessary to validate these findings (18).
| Conclusion |
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Although no convincing guidelines regarding perioperative fluid therapy, including the amount and the choice of fluid, can be derived from these studies because the definitions of standard fluid therapy and restricted fluid therapy varied, certain observations can be implemented in our current practice while we wait for further evidence for optimal fluid regimens. Some clinically useful guidelines based on the studies discussed in this review include avoidance of deep general anesthesia, which requires larger fluid administration to maintain adequate hemodynamics, and elimination of preload for patients who receive epidural analgesia. In addition, it is unnecessary to use algorithms that suggest replacement of third space losses and losses through diuresis. Blood loss may be replaced with colloid on a volume-to-volume basis. Although neither crystalloid nor colloid solutions can be expected to be ideal for every individual or in all circumstances, most authors recommend a balanced approach to fluid management with colloids administered to provide hemodynamic stability and maintain urine output of 0.5 mL · kg1 · h1 and crystalloids administered as maintenance fluids. Significant reduction in crystalloid load can be achieved without encountering intraoperative hemodynamic instability or reduced (i.e., < 0.5 mL · kg1 · h1) urinary output, just by avoiding replacement of third space losses and preloading. Postoperatively, patients who gain more than 1 kg may receive furosemide. Finally, a multidisciplinary approach to the development of clinical pathways that would include appropriate intraoperative and postoperative fluid therapy to improve postoperative outcome is needed.
| Footnotes |
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| References |
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