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

Lack of impact of nil-per-os (NPO) time on goal-directed fluid delivery in first case versus afternoon case starts: a retrospective cohort study

BACKGROUND

Goal Directed Fluid Therapy (GDFT) represents an objective fluid replacement algorithm. The effect of provider variability remains a confounder. Overhydration worsens perioperative morbidity and mortality; therefore, the impact of the calculated NPO deficit prior to the operating room may reach harm.

METHODS

A retrospective single-institution study analyzed patients at UC Irvine Medical Center main operating rooms from September 1, 2013 through September 1, 2015 receiving GDFT. The primary study question asked if GDFT suggested different fluid delivery after different NPO periods, while reducing inter-provider variability. We created two patient groups distinguished by 0715 surgical start time or start time after 1200. We analyzed fluid administration totals with either a 1:1 crystalloid to colloid ratio or a 3:1 ratio. We performed direct group-wise testing on total administered volume expressed as total ml, total ml/hr., and total ml/kg/hr. between the first case start (AM) and afternoon case (PM) groups. A linear regression model included all baseline covariates that differed between groups as well as plausible confounding factors for differing fluid needs. Finally, we combined all patients from both groups, and created NPO time to total administered fluid scatterplots to assess the effect of patient-reported NPO time on fluid administration.

RESULTS

Whether reported by total administered volume or net fluid volume, and whether we expressed the sum as ml, ml/hr., or ml/kg/hr., the AM group received more fluid on average than the PM group in all cases. In the general linear models, for all significant independent variables evaluated, AM vs PM case start did not reach significance in both cases at p = 0.64 and p = 0.19, respectively. In scatterplots of NPO time to fluid volumes, absolute adjusted and unadjusted R2 values are < 0.01 for each plot, indicating virtually non-existent correlations between uncorrected NPO time and fluid volumes measured.

CONCLUSIONS

This study showed NPO periods do not influence a patient's volume status just prior to presentation to the operating room for surgical intervention. We hope this data will influence the practice of providers routinely replacing calculated NPO period volume deficit; particularly with those presenting with later surgical case start times.

Unexpectedly prolonged fasting and its consequences on elderly patients undergoing spinal anesthetics. A prospective observational study1

Purpose

To measure the preoperative fasting durations with respect to time of the day and its effect on vital parameters and electrocardiogram in elderly patients undergoing surgery under spinal anesthesia.

Methods

This study investigated 211 patients older than 60 years undergoing elective surgery under spinal anesthesia. Patients scheduled for surgery in morning hours (AM) and afternoon hours (PM) were compared. Patients fasting hours and repeated measurements of mean arterial pressure (MAP), heart rate (HR), peripheral oxygen saturation (Sp02) and the type and number of ischemic electrocardiogram (ECG) signs were recorded and compared [preoperative, zeroth, 2nd,5th,15th,30th minutes following spinal anesthesia(SA)].

Results

Mean fasting durations were 12±2.8 and 9.5±2.1 hours in AM group and 15.5±3.4 12.7±4.4 hours in PM group for foods and liquids respectively. ECG changes were significantly more frequent in PM group and body temperatures were significantly higher in AM group patients.

Conclusion

Our study has shown that fasting times in our population is far longer than recommended and fasting prolonged>15 hours is related to a transiently increased cardiac stress and mild hypothermia.

Fasting Urinary Osmolality, CKD Progression, and Mortality: A Prospective Observational Study

RATIONALE & OBJECTIVE

Chronic kidney disease (CKD) characterized by decreased glomerular filtration rate (GFR) is often accompanied by various degrees of impaired tubular function in the cortex and medulla. Assessment of tubular function may therefore be useful in establishing the severity of kidney disease and identifying those at greater risk for CKD progression. We explored reductions in urinary concentrating ability, a well-known feature of CKD, as a risk factor for GFR decline and end-stage renal disease (ESRD).

STUDY DESIGN

Prospective longitudinal cohort study.

SETTING & PARTICIPANTS

2,084 adult patients with CKD stages 1 to 4 from the French NephroTest Cohort Study.

PREDICTOR

Fasting urinary osmolality measured using delta cryoscopy.

OUTCOMES

ESRD, mortality before ESRD, and measured GFR (mGFR) assessed using ⁵¹Cr-EDTA renal clearance.

ANALYTICAL APPROACH

Cause-specific hazards models were fit to estimate crude and adjusted associations of urinary osmolality with ESRD and death before ESRD. Linear mixed models with random intercepts were fit to evaluate the association of urinary osmolality with slope of decline in mGFR.

RESULTS

At baseline, mean age was 58.7±15.2 (SD) years with a median mGFR of 40.2 (IQR, 29.1-54.5) mL/min/1.73m² and a median fasting urinary osmolality of 502.7±151.7mOsm/kg H₂O. Baseline fasting urinary osmolality was strongly associated with mGFR (R=0.54; P < 0.001). 380 ESRD events and 225 deaths before ESRD occurred during a median follow-up of 5.9 (IQR, 3.8-8.2) years. Patients with lower baseline fasting urinary osmolality had higher adjusted risk for ESRD but not for mortality (HRs of 1.97 [95% CI, 1.26-3.08] and 0.99 [95% CI, 0.68-1.44], respectively, for the lowest vs highest tertile). Based on a mixed linear model adjusted for baseline mGFR and clinical characteristics, patients in the lowest tertile of baseline urinary osmolality had a steeper decline in kidney function (-4.9% ± 0.9% per year; P < 0.001) compared with patients in the highest tertile.

LIMITATIONS

Fasting was self-reported.

CONCLUSIONS

Fasting urinary osmolality may be a useful tool, in addition to GFR and albuminuria, for assessing nonglomerular damage in patients with CKD who are at higher risk for CKD progression.

Fluid deficits during prolonged overnight fasting in young healthy adults

BACKGROUND

Overnight fasting is often prolonged before scheduled surgery, and the extent of perioperative fluid replacement may influence outcome. In clinical practice, basic requirements are estimated at 1.2-2.0 mL·kg^-1 ·h^-1 , but there is little contemporary clinical data on what deficits result from complete fasting. This prospective preclinical study was designed to determine total fluid loss during overnight fasting, prolonged during daytime.

METHODS

Twenty (10 female) healthy adult volunteers, aged 24 (range 21-46) years, fasted from 22:00 until 16:00, and had their body weight and urine output measured at predefined time intervals.

RESULTS

The median (interquartile range) fluid deficits were 0.82 (0.73-1.00) kg, corresponding to 1.26 (1.11-1.41) g·kg^-1 ·h^-1 for the initial overnight fasting period, 0.59 (0.40-0.70) kg and 0.99 (0.83-1.31) g·kg^-1 ·h^-1 for the consecutive daytime period, and 1.47 (1.27-1.64) kg and 1.19 (1.05-1.28) g·kg^-1 ·h^-1 for the total period of fasting. Urine output accounted for 52% of total weight loss and was 36% of the baseline hourly level during the last four-hour period of fasting.

CONCLUSIONS

Ten hours of overnight fasting in young adults induces fluid deficits at the lower limit of estimated intervals referred to in clinical practice, and hourly weight loss gradually decreases further during prolonged daytime fasting. These findings indicate that current routine procedures do slightly overestimate fluid deficits resulting from prolonged fasting in perioperative clinical practice.

[Does fasting influence preload responsiveness in ASA 1 and 2 volunteers?]

INTRODUCTION

Preoperative fasting was long regarded as an important cause of fluid depletion, leading to hemodynamic instability during surgery should replenishment not be promptly instituted. Lately, this traditional point of view has been progressively challenged, and a growing number of authors now propose a more restrictive approach to fluid management, although doubt remains as to the true hemodynamic influence of preoperative fasting.

METHODS

We designed an observational, analytic, prospective, longitudinal study in which 31 ASA 1 and ASA 2 volunteers underwent an echocardiographic examination both before and after a fasting period of at least 6h. Data from both static and dynamic preload indices were obtained on both periods, and subsequently compared.

RESULTS

Static preload indices exhibited a markedly variable behaviour with fasting. Dynamic indices, however, were far more consistent with one another, all pointing in the same direction, i.e., evidencing no statistically significant change with the fasting period. We also analysed the reliability of dynamic indices to respond to known, intentional preload changes. Aortic velocity time integral (VTI) variation with the passive leg raise manoeuvre was the only variable that proved to be sensitive enough to consistently signal the presence of preload variation.

CONCLUSION

Fasting does not appear to cause a change in preload of conscious volunteers nor does it significantly alter their position in the Frank-Starling curve, even with longer fasting times than usually recommended. Transaortic VTI variation with the passive leg raise manoeuvre is the most robust dynamic index (of those studied) to evaluate preload responsiveness in spontaneously breathing patients.

Does fasting influence preload responsiveness in ASA 1 and 2 volunteers?

INTRODUCTION

Preoperative fasting was long regarded as an important cause of fluid depletion, leading to hemodynamic instability during surgery should replenishment is not promptly instituted. Lately, this traditional point of view has been progressively challenged, and a growing number of authors now propose a more restrictive approach to fluid management, although doubt remains as to the true hemodynamic influence of preoperative fasting.

METHODS

We designed an observational, analytic, prospective, longitudinal study in which 31 ASA 1 and ASA 2 volunteers underwent an echocardiographic examination both before and after a fasting period of at least 6hours (h). Data from both static and dynamic preload indices were obtained on both periods, and subsequently compared.

RESULTS

Static preload indices exhibited a markedly variable behaviour with fasting. Dynamic indices, however, were far more consistent with one another, all pointing in the same direction, i.e., evidencing no statistically significant change with the fasting period. We also analysed the reliability of dynamic indices to respond to known, intentional preload changes. Aortic velocity time integral (VTI) variation with the passive leg raise manoeuvre was the only variable that proved to be sensitive enough to consistently signal the presence of preload variation.

CONCLUSION

Fasting does not appear to cause a change in preload of conscious volunteers nor does it significantly alter their position in the Frank-Starling curve, even with longer fasting times than usually recommended. Transaortic VTI variation with the passive leg raise manoeuvre is the most robust dynamic index (of those studied) to evaluate preload responsiveness in spontaneously breathing patients.

[Preoperative fasting guidelines: an update]

Anesthesiology societies have issued various guidelines on preoperative fasting since 1990, not only to decrease the incidence of lung aspiration and anesthetic morbidity, but also to increase patient comfort prior to anesthesia. Some of these societies have been updating their guidelines, as such that, since 2010, we now have 2 evidence-based preoperative fasting guidelines available. In this article, an attempt is made to review these updated guidelines, as well as the current instructions for more controversial patients such as infants, the obese, and a particular type of ophthalmic surgery.

Dose and type of crystalloid fluid therapy in adult hospitalized patients

OBJECTIVE

In this narrative review, an overview is given of the pros and cons of various crystalloid fluids used for infusion during initial resuscitation or maintenance phases in adult hospitalized patients. Special emphasis is given on dose, composition of fluids, presence of buffers (in balanced solutions) and electrolytes, according to recent literature. We also review the use of hypertonic solutions.

METHODS

We extracted relevant clinical literature in English specifically examining patient-oriented outcomes related to fluid volume and type.

RESULTS

A restrictive fluid therapy prevents complications seen with liberal, large-volume therapy, even though restrictive fluid loading with crystalloids may not demonstrate large hemodynamic effects in surgical or septic patients. Hypertonic solutions may serve the purpose of small volume resuscitation but carry the disadvantage of hypernatremia. Hypotonic solutions are contraindicated in (impending) cerebral edema, whereas hypertonic solutions are probably more helpful in ameliorating than in preventing this condition and improving outcome. Balanced solutions offer a better approach for plasma composition than unbalanced ones, and the evidence for benefits in patient morbidity and mortality is increasing, particularly by helping to prevent acute kidney injury.

CONCLUSIONS

Isotonic and hypertonic crystalloid fluids are the fluids of choice for resuscitation from hypovolemia and shock. The evidence that balanced solutions are superior to unbalanced ones is increasing. Hypertonic saline is effective in mannitol-refractory intracranial hypertension, whereas hypotonic solutions are contraindicated in this condition.

Preoperative oral rehydration solution intake volume does not affect relative change of mean arterial blood pressure and crystalloid redistribution during general anesthesia in low-risk patients: an observational cohort study

Despite the implementation of liberal preoperative fasting routines, it is unclear whether preoperative oral rehydration solution intake volume affects blood pressure during general anesthesia. We enrolled 60 patients (American Society of Anesthesiologists status I/II) undergoing tympanoplasty. Patients drank 200-1,000 ml oral rehydration solution until 2-3 h before anesthesia induction. Anesthesia was induced by propofol and maintained with sevoflurane and remifentanil. Coinciding with anesthesia induction, 15 ml/kg Ringer's acetate solution was administered intravenously over 60 min followed by 1 ml/kg Ringer's acetate solution over the next 30 min. Mean arterial blood pressure (MAP) and whole-body bioelectrical resistance for extracellular fluid (R e) during anesthesia were compared between retrospectively classified intake groups of oral rehydration solution. There were no differences in mean MAP during the 30-90 min period relative to baseline [0.67 (0.60-0.74), 0.65 (0.61-0.76), 0.64 (0.60-0.70), P = 0.96] and relative R e at 90 min [0.945 (0.018), 0.944 (0.021), 0.943 (0.021), P = 0.95] between the small (n = 14), intermediate (n = 29), and large (n = 17) intake groups. The intake volume of preoperative oral rehydration solution does not affect the magnitude of hypotension during general anesthesia in low-risk patients undergoing minor surgery.