Assessment of preoperative fluid depletion using bioimpedance analysis

Intravenous Fluid to Prevent Hypotension in Patients Undergoing Elective Colonoscopy

Colonoscopy may be associated with hypotension during sedation leading to postoperative morbidity. However, no treatment is proven to ameliorate intraoperative hypotension for this procedure. We therefore conducted a randomized trial to determine the effect of intravenous fluid infusion on the incidence of hypotension during sedation for colonoscopy. With institutional approval, 160 patients presenting for elective colonoscopy were randomized to 1.5 ml/kg or 15 ml/kg Hartmann's solution before colonoscopy. All observers were blind to group allocation. The incidence of hypotension during sedation (29% vs 25%; P=0.59) and postoperative morbidity (nausea, vomiting, headache, drowsiness and dizziness) (41% vs 39%; P=0.75) did not differ between the two groups. Hypotensive patients were older, had a higher baseline systolic blood pressure, and were thirstier after fluid infusion than normotensive patients. This study does not support the use of 15 ml/kg Hartmann's solution to reduce the incidence of hypotension or postoperative morbidity in patients undergoing elective colonoscopy.

American Society for Enhanced Recovery (ASER) and Perioperative Quality Initiative (POQI) joint consensus statement on prevention of postoperative infection within an enhanced recovery pathway for elective colorectal surgery

BACKGROUND

Colorectal surgery (CRS) patients are an at-risk population who are particularly vulnerable to postoperative infectious complications. Infectious complications range from minor infections including simple cystitis and superficial wound infections to life-threatening situations such as lobar pneumonia or anastomotic leak with fecal peritonitis. Within an enhanced recovery pathway (ERP), there are multiple approaches that can be used to reduce the risk of postoperative infections.

METHODS

With input from a multidisciplinary, international group of experts and through a focused (non-systematic) review of the literature, and use of a modified Delphi method, we achieved consensus surrounding the topic of prevention of postoperative infection in the perioperative period for CRS patients.

DISCUSSION

As a part of the first Perioperative Quality Initiative (POQI-1) workgroup meeting, we sought to develop a consensus statement describing a comprehensive, yet practical, approach for reducing postoperative infections, specifically for CRS within an ERP. Surgical site infection (SSI) is the most common postoperative infection. To reduce SSI, we recommend routine use of a combined isosmotic mechanical bowel preparation with oral antibiotics before elective CRS and that infection prevention strategies (also called bundles) be routinely implemented as part of colorectal ERPs. We recommend against routine use of abdominal drains. We also give consensus guidelines for reducing pneumonia, urinary tract infection, and central line-associated bloodstream infection (CLABSI).

Fluid prescription practices of anesthesiologists managing patients undergoing elective colonoscopy: an observational study

Background

Routine fluid prescription is common practice amongst anesthesiologists caring for patients undergoing colonoscopy. However there is limited information about routine procedural fluid prescription practices of anesthesiologists in this setting. Routine fluid administration may also have important pharmaco-economic implications for the health care budget. Therefore we performed a prospective observational study assessing the fluid prescription practices of anesthesiologists caring for patients undergoing elective colonoscopy.

Methods

With Institutional Review Board approval, adult patients receiving procedural fluid intervention during elective colonoscopy were included. Data collected: size of intravenous cannula inserted, volumes of fluid administered, adverse events, procedure duration, and pharmaco-economic costs associated with fluid prescription. Anesthesiologists and gastroenterologists were blinded to the study.

Results

We collected data on 289 patients who received fluid prescription by their attending anesthesiologist. Median patient age: 48 yrs (range 18–83), gender: 174 (60%) female; median duration of procedure: 24 minutes (range 12–48). Cannula size: 181 (63%) patients received a 22G cannula or smaller. Median volume of fluid administered during the colonoscopy was 325 ml (range 0 to 1000 ml). Median duration of the procedure: 25 minutes (range 12 to 48 minutes). Median volume of fluid administered in the post anaesthesia recovery unit: 450 ml (range 0 to 1000 ml). Fifteen patients (5%) became hypotensive during the procedure and two patients (<1%) developed hypotension in the PACU. There was no difference in the median fluid requirements between patients with hypotension and those without. Fluid volumes were strongly associated with increasing cannula diameter (p = 0.0001), however there was no association between fluid volumes administered and vasopressor use, peri-procedural adverse events, or procedure duration. At our institution fluid therapy currently cost about AUD$4.90 per patient: 1 L crystalloid $1.18 and fluid delivery set $3.77 Our institution performs over 9000 endoscopic procedures annually with fluid therapy costing about $45,000/year.

Conclusions

Routine fluid prescription by anesthesiologists managing patients undergoing colonoscopy was ineffective with low actual fluid volumes delivered during the procedure. There was no association between volumes of fluid delivered and procedural hypotension, adverse events, or procedure duration. Anesthesiologists should question the clinical and pharmaco-economic value of routine fluid administration for patients undergoing elective endoscopy.

Preoperative fasting does not affect haemodynamic status: a prospective, non-inferiority, echocardiography study

BACKGROUND

The link between preoperative fasting and hypovolaemia remains unclear. We tested the hypothesis that preoperative fasting does not significantly increase the proportion of patients with hypovolaemia according to transthoracic echocardiography (TTE) criteria.

METHODS

Patients of ASA status I-III and without bowel preparation were included in a non-inferiority, prospective, single-centre trial. Patients underwent passive leg raising (PLR) test and TTE at admission (Day 0) and after 8 h fasting (Day 1). The primary hypothesis was that an 8 h preoperative fasting does not increase the proportion (margin=5%) of patients with a positive PLR test ('functional approach'). The secondary hypothesis was that echocardiographic filling pressures or stroke volume (margin 10%) are not affected by preoperative fasting ('static approach').

RESULTS

One hundred patients were included and 98 analysed. After an 8 h fasting, the change in the proportion of responders to PLR was -6.1% [95% confidence interval (CI)=-16.0 to 3.8] of responders to PLR test on Day 0 when compared with Day 1. Because 95% CI was strictly inferior to 5%, there was no significant increase in the proportion of PLR responders on Day 1 when compared with Day 0. The 95% CI changes of static variables were always fewer than 10%, meaning that preoperative fasting induced significantly no relevant changes in static variables.

CONCLUSION

Preoperative fasting did not alter TTE dynamic and static preload indices in ASA I-III adult patients. These results suggest that preoperative fasting does not induce significant hypovolaemia. Clinical trial registration NCT 01258361.

Fluid and electrolyte balance after major thoracic surgery by bioimpedance and endocrine evaluation

OBJECTIVE

Weight gain with oedema development is a complication of major surgical procedures with an incidence as high as 40%. Fluid retention is not always clinically evident and it is reported despite fluid-restriction regime. The causes are several and not totally clear. We performed a prospective study to assess the amount of fluid accumulation and redistribution observed after major thoracic surgery.

METHODS

In 49 patients submitted to lobectomy with systematic lymph node dissection for lung cancer, we measured preoperatively and on the postoperative days 1, 2, 4 and 7, body weight, fluid balance, brain natriuretic peptide (BNP) and bioimpedance analysis (BIA)-derived parameters resistance (R) and reactance (X(c)).

RESULTS

The postoperative course was characterised by significant changes. Mean increase in body weight was 2.7 kg ((1.9-3.4); p<0.001) on postoperative day 2. Most of the patients had a negative basal fluid balance (-244 ml (-520 to -50)), whereas, on postoperative day 2, we observed a positive and significant change (+968 ml (646-1456), p<0.001)). Total body R and X(c) fell on the first day (p<0.001), anticipating the changes in weight and fluid balance. BNP increased on day 1, immediately after surgery, and remained significantly above basal values for the entire observation period (p<0.001), in the absence of clinical signs of heart failure.

CONCLUSION

The three methods used consistently showed a significant fluid retention over the course of the study. BIA was an easy, reproducible and non-invasive method for the estimation and early detection of fluid retention. Increase in BNP may be related to the systemic reaction to stress and to the decreased pulmonary vascular bed. We found no correlation between fluid retention and length of anaesthesia, sex, age, blood loss and body mass index. The clinical and prognostic implication of weight gain may be relevant to patient's health.

Hydration status after overnight fasting as measured by urine osmolality does not alter the magnitude of hypotension during general anesthesia in low risk patients

BACKGROUND

The increased distribution of crystalloid solution into the interstitial space may decrease the effectiveness of intravascular volume loading in patients. We investigated whether preoperative hydration status after overnight fasting affects interstitial fluid redistribution and thus the magnitude of hypotension during general anesthesia.

METHODS

Sixty ASA physical status I/II patients undergoing tympanoplasty fasted from midnight. Anesthesia was induced by fentanyl and propofol and maintained with sevoflurane and remifentanil. Coinciding with the induction of anesthesia, 15 mL/kg acetated Ringer solution was infused IV over 60 minutes followed by 1 mL/kg acetated Ringer solution over the next 30 minutes. Urine osmolalities after induction of anesthesia and during the study period (pre-U(osm), post-U(osm)) and percent decreases of whole-body bioelectrical resistance for extracellular fluid relative to baseline at the end of the study period (ΔR(e)) were measured. Patients with a pre-U(osm) < the 25th percentile or with a pre-U(osm) > the 75th percentile of pre-U(osm) were categorized in the hydrated or the dehydrated group, respectively. A range of variables, including mean arterial blood pressure during the 30- to 90-minute period relative to baseline, and ΔR(e), were compared between the groups.

RESULTS

The dehydrated group (pre-U(osm) >759.5 mOsm/kg, n = 15) had a lower age (44 vs 52 years, P = 0.049) and had a higher post-U(osm) (181 vs 55 mOsm/kg, P = 0.001) compared with the hydrated group (pre-U(osm) <378.5 mOsm/kg, n = 15). Mean arterial blood pressure during the 30- to 90-minute period relative to baseline (0.67 vs 0.67, P = 0.85) with 95% confidence interval for the difference of means (-0.070 to 0.084) and ΔR(e) (5.6% vs 6.0%, P = 0.58) with 95% confidence interval for the difference of means (-1.85% to 1.06%) were similar for the hydrated and dehydrated groups.

CONCLUSIONS

Preoperative dehydration after overnight fasting as measured by urine osmolality did not alter the magnitude of hypotension during general anesthesia. This finding suggests that intravascular volume loading with crystalloid solution to prevent hypotension during general anesthesia is an unfounded practice for low risk patients after overnight fasting.

Functional intravascular volume deficit in patients before surgery

BACKGROUND

Stroke volume (SV) maximization with a colloid infusion, referred to as individualized goal-directed therapy, improves outcome in high-risk surgery. The fraction of patients who need intravascular volume to establish a maximal SV has, however, not been evaluated, and there are only limited data on the volume required to establish a maximal SV before the start of surgery. Therefore, we estimated the occurrence and size of the potential functional intravascular volume deficit in surgical patients.

METHODS

Patients scheduled for mastectomy (n=20), open radical prostatectomy (n=20), or open major abdominal surgery (n=20) were anaesthetized, and before the start of surgery, a 200 ml colloid fluid challenge was provided and repeated if a >or=10% increment in SV estimated by oesophageal Doppler was established. The volume needed for SV maximization defined the intravascular volume deficit.

RESULTS

Forty-two (70%) of the patients needed volume to establish a maximal SV. For the patients needing volume, the required amount was median 200 ml (range 200-600 ml), with no significant difference between the three groups of patients. The required volume was >or=400 ml in nine patients (15%).

CONCLUSION

The majority of anaesthetized patients present with a functional intravascular volume deficit before surgery. Although the deficit in general was minor, a fraction of patients presented with a deficit that may be of clinical relevance, emphasizing the importance of the individual approach of goal-directed fluid therapy.

Bioimpedance monitoring of airway inflammation in asthmatic allergic children

BACKGROUND

Asthma in childhood is characterized by chronic inflammation. Measurement of bioimpedance (BI) is a non-invasive way of detecting airway inflammation. The aim was to compare BI with exhaled nitric oxide (eNO) and lung function evaluations in asthmatic allergic children while not exposed to offending allergens.

METHODS

22 asthmatic children allergic to house dust mites have been enrolled while residents at high altitude in an environment free of house dust mites. They were evaluated at T0 after allergen exposure at home, at T1 and at T2 after 1 and 4 months of allergen avoidance, respectively.

RESULTS

eNO decreased from 32.21 +/- 5.70 ppb at T0 to 21.92 +/- 4.36 ppb at T1, after one month at high altitude (p = 0.038), without a further decrease at T2. Data in electrical activity showed a significant decrease in conductivity of lower airways between T0 (48.53 +/- 3.53 microA) and T1 (42.08 +/- 3.47 microA) (p = 0.023). deltaB parameter (difference between conductivity of lower respiratory tract and average yield) showed significant decrease from T0 (20.75 +/- 2.64 microA), and T1 (12.84 +/- 2.52 microA) (p < 0.01), but no further decrease at T2. No difference in lung function parameters was observed.

CONCLUSION

Allergen avoidance regimen modifies inflammatory parameters in allergic asthmatics. Evaluation of extracellular bioelectrical conductivity seems to represent a promising non-invasive method to assess airway inflammation.

Australian Anaesthetists’ Practice of Sedation for Gastrointestinal Endoscopy in Adult Patients

A wide spectrum of practice in sedation for gastrointestinal endoscopy in adult patients is documented overseas, but a current profile of the practice of Australian anaesthetists is unavailable. We therefore surveyed 200 Fellows of the Australian and New Zealand College of Anaesthetists on the choice of drugs and monitoring, use of analgesic throat spray and prophylactic intravenous fluids and the depth of sedation for gastrointestinal endoscopy. Our response rate was 57% and endoscopy formed a significant part of most respondents’ practices. Propofol was used for almost all procedures, in combination with midazolam alone (14%), fentanyl alone (6%), midazolam and fentanyl (61%), another drug (15%) or no adjuvant(4%). The majority of patients received prophylactic intravenous fluids for endoscopic retrograde cholangio-pancreatography (83%) and colonoscopy (64%), but not for gastroscopy (20%). All patients received supplemental oxygen and monitoring with pulse oximetry. However, over 20% of patients having gastroscopy or colonoscopy did not have noninvasive blood pressure monitoring. A maximum depth of sedation during which the patient was unresponsive to painful stimulation (commensurate with general anaesthesia) was targeted by 54% of respondents. Significant variations exist in the practice of sedation and monitoring for endoscopy in adult patients by anaesthetists in Australia.

Dehydration induced by bowel preparation in older adults does not result in cognitive dysfunction

BACKGROUND

Postoperative cognitive dysfunction occurs in a proportion of patients after noncardiac surgery. Older patients are particularly vulnerable. We hypothesized that dehydration, a common perioperative problem in the elderly, may provoke cognitive dysfunction. We used a clinical scenario free of surgical/anesthetic intervention to determine whether dehydration caused by bowel preparation results in cognitive changes.

METHODS

Thirty-eight patients of an age associated with a significant incidence of postoperative cognitive dysfunction were recruited in a prospective observational study. A further control group of 14 patients undergoing sigmoidoscopy, who did not receive any bowel preparation, were matched for age, education, and gender.

RESULTS

Loss of total body weight (1.5 kg [95% CI: 0.9-2.2]; P < 0.001) occurred in patients undergoing bowel preparation (2.0 [95% CI: 1.3-2.6] percent total body weight), whereas sigmoidoscopy patients' weight did not change (0.17 kg [95% CI: -0.2-0.6 kg]; P = 0.26). Total body water, derived from foot bioimpedance, indicated dehydration in the bowel preparation group only (mean impedance change 36 [Omega] [95% CI; 25-46], P < 0.001) with a calculated decrease of 2.6% in total body water (95% CI: 1.1-4.8; P < 0.001). Hematocrit increased after bowel preparation only (prebowel prep 0.41 [0.40-0.43] versus postbowel prep 0.43 [0.42-0.45]; P = 0.003). Despite this degree of dehydration, all cognitive tests were within 1 SD of the population mean of normal values. Repeated measures analysis of variance did not reveal significant changes for within group comparisons over time for motor speed (P = 0.51), executive function (P = 0.57), Trail Making Tests and recall (P = 0.88), other than a 3 s slowing in learning ability (Rey Auditory Verbal Learning Test; P = 0.04). Hydration status did not affect learning (P = 0.42), recall (P = 0.30) motor speed (P = 0.36), or executive function tests (P = 0.26).

CONCLUSION

Dehydration alone does not result in cognitive dysfunction.

Intravascular Fluid Administration and Hemodynamic Performance During Open Abdominal Surgery

We studied whether central hemodynamics measured by a pulmonary artery catheter can serve as a pharmacodynamic expression of fluid therapy in 10 patients undergoing open abdominal surgery. We examined how closely hemodynamic variables follow plasma dilution, which is an index of plasma volume expansion, during and after an IV infusion of 25 mL/kg of lactated Ringer's solution over 45 min. Pulmonary artery wedge pressure and central venous pressure responded to IV fluid with an increase that correlated with accompanying plasma dilution. Six of 10 patients showed a decrease in cardiac output that was probably secondary to an increase in peripheral vascular resistance (nonresponders), whereas the rest increased cardiac output (responders). Volume kinetic analysis suggested that 54% of the infused fluid resided in the central fluid space at the end of the infusion and 25% at the end of the study in the responders compared with 25% and 3%, respectively, in nonresponders. In conclusion, half of the patients undergoing open abdominal surgery responded to crystalloid fluid with a decrease in cardiac output. Pulmonary artery wedge pressure and central venous pressure responded more consistently to different degrees of plasma dilution, which can be simulated for various fluid regimens using volume kinetics.

Effect of "preoperative" oral carbohydrate treatment on insulin action--a randomised cross-over unblinded study in healthy subjects

BACKGROUND AND AIMS

Preoperative intake of a clear carbohydrate-rich drink reduces insulin resistance after surgery. In this study, we evaluated whether this could be related to increased insulin sensitivity at the onset of surgery. Furthermore, we aimed to establish the optimal dose-regimen.

METHODS

Six healthy volunteers underwent hyperinsulinaemic (0.8 mU/kg/min), normoglycaemic (4.5 mmol/l) clamps and indirect calorimetry on four occasions in a crossover-randomised order; after overnight fasting (CC), after a single evening dose (800 ml) of the drink (LC), after a single morning dose (400 ml, CL) and after intake of the drink in the evening and in the morning before the clamp (LL). Data are presented as mean+/-SD. Statistical analysis was performed using the Student's t-test and ANOVA.

RESULTS

Insulin sensitivity was higher in CL and LL (9.2+/-1.5 and 9.3+/-1.9 mg/kg/min, respectively) compared to CC and LC (6.1+/-1.6 and 6.6+/-1.9 mg/kg/min, P<0.01 vs. CL and LL).

CONCLUSIONS

A carbohydrate-rich drink enhances insulin action 3 h later by approximately 50%. Enhanced insulin action to normal postprandial day-time level at the time of onset of anaesthesia or surgery is likely to, at least partly, explain the effects on postoperative insulin resistance.

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.