Concentrated urine, low urine flow, and postoperative elevation of plasma creatinine: A retrospective analysis of pooled data.

Elevations of plasma creatinine are common after major surgery, but their pathophysiology is poorly understood. To identify possible contributing mechanisms, we pooled data from eight prospective studies performed in four different countries to study circumstances during which elevation of plasma creatinine occurs. We included 642 patients undergoing mixed major surgeries, mostly open gastrointestinal. Plasma and urinary creatinine and a composite index for renal fluid conservation (Fluid Retention Index, FRI) were measured just before surgery and on the first postoperative morning. Urine flow was measured during the surgery. The results show that patients with a postoperative increase in plasma creatinine by >25% had a high urinary creatinine concentration (11.0±5.9 vs. 8.3±5.6 mmol/L; P< 0001) and higher FRI value (3.2±1.0 vs. 2.9±1.1; P< 0.04) already before surgery was initiated. Progressive increase of plasma creatinine was associated with a gradually lower urine flow and larger blood loss during the surgery (Kruskal-Wallis test, P< 0.001). The patients with an elevation > 25% also showed higher creatinine and a higher FRI value on the first postoperative morning (P< 0.001). Elevations to > 50% of baseline were associated with slightly lower mean arterial pressure (73 ± 10 vs. 80 ± 12 mmHg; P< 0.005). We conclude that elevation of plasma creatinine in the perioperative period was associated with low urine flow and greater blood loss during surgery and with concentrated urine both before and after the surgery. Renal water conservation-related mechanisms seem to contribute to the development of increased plasma creatinine after surgery.

Predicting fluid responsiveness using esophagus Doppler monitoring and pulse oximetry derived pleth variability index; retrospective analysis of a hemodynamic study.

BACKGROUND: Fluid therapy during major surgery can be managed by providing repeated bolus infusions until stroke volume no longer increases by ≥ 10%. However, the final bolus in an optimization round increases stroke volume by < 10% and is not necessary. We studied how different cut-off values for the hemodynamic indications given by esophagus Doppler monitoring, as well as augmentation by pulse oximetry, are associated with a higher or smaller chance that stroke volume increases by ≥ 10% (fluid responsiveness) before fluid is infused. METHODS: An esophagus Doppler and a pulse oximeter that displayed the pleth variability index were used to monitor the effects of a bolus infusion in 108 patients undergoing goal-directed fluid therapy during major open abdominal surgery. RESULTS: The analyzed data set comprised 266 bolus infusions. The overall incidence of fluid responsiveness was 44%, but this varied greatly depending on pre-infusion hemodynamics. The likelihood of being fluid-responsive was 30%-38% in the presence of stroke volume > 80 mL, corrected flow time > 360 ms, or pleth variability index < 10%. The likelihood was 21% if stroke volume had decreased by <8% since the previous optimization, which decreased to 0% if combined with stroke volume > 100 mL. By contrast, the likelihood of fluid responsiveness increased to 50%-55% when stroke volume ≤ 50 mL, corrected flow time ≤ 360 ms, or pleth variability index ≥ 10. A decrease in stroke volume by > 8% since the previous optimization was followed by a 58% likelihood of fluid responsiveness that, in combination with any of the other hemodynamic variables, increased to 66%-76%. CONCLUSIONS: Single or combined hemodynamic variables provided by esophagus Doppler monitoring and pulse oximetry derived pleth variability index could help clinicians avoid unnecessary fluid bolus infusions.

Plasma volume expansion reveals hidden metabolic acidosis in patients with diabetic ketoacidosis.

BACKGROUND: Hyperchloremic metabolic acidosis that develops during the treatment of diabetic ketoacidosis is usually attributed to the chloride content of resuscitation fluids. We explored an alternative explanation, namely that fluid-induced plasma volume expansion alters the absolute differences in the concentrations of sodium and chloride (the Na-Cl gap) enough to affect the acid-base balance. We analyzed data from a prospective single-center cohort study of 14 patients treated for diabetic ketoacidosis. All patients received 1 L of 0.9% saline over 30 min on two consecutive days. Blood gases were sampled before and after the infusions. RESULTS: The initial plasma volume was estimated to be 25 ± 13% (mean ± SD) below normal on admission to the intensive care unit. At that time, most patients had an increased actual Na-Cl gap, which counteracts acidosis. However, the correction of the plasma volume deficit revealed that these patients would have had a decreased Na-Cl gap upon admission if they had been normovolemic at that time; the estimated "virtual Na-Cl gap" of 29 ± 5 mmol/L was significantly lower than the uncorrected value, which was 39 ± 5 mmol/L (P < 0.001). On Day 2, most patients had a decreased actual Na-Cl gap (33 ± 5 mmol/L), approaching the corrected value on Day 1. CONCLUSIONS: The hyperchloremic acidosis commonly seen in diabetic ketoacidosis may not be primarily caused by the chloride content of resuscitation fluids but, rather, by the restoration of plasma volume, which reveals the hidden metabolic acidosis caused by a decreased Na-Cl gap. Trial registration Clinical Trials Identifier NCT02172092, registered June 24, 2014, https://www. CLINICALTRIALS: gov/NCT02172092.

Goal-directed therapy during transthoracic oesophageal resection does not improve outcome: Randomised controlled trial.

BACKGROUND: Goal-directed therapy (GDT) is expected to be of highest benefit in high-risk surgery. Therefore, GDT is recommended during oesophageal resection, which carries a high risk of postoperative complications. OBJECTIVES: The aim of this study was to confirm the hypothesis that GDT during oesophageal resection improves outcome compared with standard care. DESIGN: A randomised controlled study. SETTING: Two Swedish university hospitals, between October 2011 and October 2015. PATIENTS: Sixty-four patients scheduled for elective transthoracic oesophageal resection were randomised. Exclusion criteria included colonic interposition and significant aortic or mitral valve insufficiency. INTERVENTION: A three-step GDT protocol included stroke volume optimisation using colloid boluses as assessed by pulse-contour analysis, dobutamine infusion if cardiac index was below 2.5 l min m and norepinephrine infusion if mean arterial blood pressure was below 65 mmHg. MAIN OUTCOME MEASURE: The incidence of complications per patient at 5 and 30 days postoperatively as assessed using a predefined list. RESULTS: Fifty-nine patients were available for analysis. Patients in the intervention group received more colloid fluid (2190 ±â€Š875 vs. 1596 ±â€Š759 ml, P < 0.01) and dobutamine more frequently (27/30 vs. 9/29, P < 0.01). The median [interquartile range, IQR] incidence of complications per patient 5 days after surgery was 2 [0 to 3] in the intervention group and 1 [0 to 2] in the control group (P = 0.10), and after 30 days 4 [2 to 6] in the intervention group and 2 [1 to 4] in the control group (P = 0.10). CONCLUSION: Goal-directed therapy during oesophageal resection did not result in a reduction of the incidence of postoperative complications. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT01416077.

Pleth variability index or stroke volume optimization during open abdominal surgery: a randomized controlled trial.

BACKGROUND: The impact of Goal Directed Fluid Therapy (GDFT) based on the non-invasive Pleth Variability Index (PVI) on clinical outcome after abdominal surgery has only sparingly been explored. The purpose of this study was to compare the effect of intraoperative GDFT guided by PVI to a control group using esophageal Doppler on the incidence of complications and length of hospital stay after major abdominal surgery. We hypothesized that there would be no difference between the groups. METHODS: This was a randomized controlled trial in a Swedish university hospital between November 2011 and January 2015; 150 patients scheduled for open abdominal surgery lasting 2 h or more were included. Exclusion criteria included hepatic resection or severe cardiac arrhythmia. The patients were randomized 1:1 to either the intervention group or the control group. The intervention group received intraoperative GDFT by administering fluid boluses of 3 ml/kg tetrastarch aiming at a PVI value below 10%, while GDFT in the control group aimed for optimization of stroke volume as assessed with esophageal Doppler. Blinded observers assessed complications until postoperative day 30 using pre-defined definitions, as well as length of hospital stay. RESULTS: One hundred and-fifty patients were randomized and 146 patients were available for the final data analysis. Median duration of surgery was 3 h. A total of 64 complications occurred in the PVI group (N = 74) and 70 in the Doppler group (N = 72) (p = 0.93). Median (IQR) length of stay was 8.0 (8.0) days in the PVI group and 8.0 (9.5) in the Doppler group (P = 0.57). CONCLUSIONS: No difference in clinical outcome, as defined by number of postoperative complications, and length of hospital stay, was found when goal directed fluid therapy was applied using PVI as an alternative to esophageal Doppler. PVI appears to be an acceptable alternative to esophageal Doppler for goal directed fluid therapy during major open abdominal surgery. TRIAL REGISTRATION: Clinicaltrials.gov NCT01458678 . Date of first registration October 20, 2011.

Preoperative fluid retention increases blood loss during major open abdominal surgery.

BACKGROUND: Quantification of renal fluid conservation is possible by urine analysis, and the results can indicate dehydration. The present report sought to determine whether this fluid retention correlates with fluid requirements during major abdominal surgeries that have estimated operating times ≥ 2 h. METHODS: Urine colour, specific weight, osmolality and creatinine concentration were used to calculate a composite "fluid retention index" (FRI) in 97 patients prior to major abdominal surgery. Goal-directed fluid volume optimization, with hydroxyethyl starch supplemented with a background administration of crystalloid fluid, was used. RESULTS: The median preoperative FRI was 3.0. Fluid retention, considered as present when FRI ≥ 3.5, was found in 37% of the patients. Fluid retention was followed by a significantly larger blood loss (+ 125%; 450 vs. 200 ml), higher haemorrhage rate (+ 41%; 123 vs. 87 ml/h) and greater need for both colloid (+ 43%; 1.43 vs. 1.00 l) and crystalloid (+ 18%; 1.28 vs. 1.08 l) fluids. Despite the larger blood loss, the total fluid balance was more positive after surgery in the dehydrated patients (+ 26%; 1.91 vs. 1.51 l; P < 0.02). CONCLUSIONS: Preoperative fluid retention, as detected in a urine sample, was associated with a greater blood loss and a more positive fluid balance during major abdominal surgery. TRIAL REGISTRATION: ClinicalTrials.gov, NCT01458678.