A few considerations regarding fluid resuscitation in the obese & otherwise:
1) Muscle and solid organs are 75-85% water and densely vascular. Fat is 10% water and much less vascular. Distribution of newly administered isotonic fluid such as normal saline will be limited to the extracellular space. With normal capillary permeability and osmolality this distribution will be roughly 2/3 extravascular and 1/3 intravascular. The fractional distribution will increase to the extravascular space if capillary permeability is increased or osmolality is decreased, as in septic patients. 2) Lean body mass is increased in the obese by as much as 40% in some estimates. Predicted ideal body weight derived from height will underestimate true lean body mass in the obese. 3) Blood volume is increased in the obese in proportion to weight and may be as useful a number as any for estimating a necessary resuscitation volume in sepsis. The Nadler formula has been utilized to calculate blood volume in stable patients. 4) Most studies addressing resuscitation volumes utilize actual body weight. The observed range to reach a target (such as CVP) is very large, as evidenced for example by the large standard deviations in the Rivers EGDT study. 5) The "initial fluid bolus" recommended for resuscitation in sepsis seems to be an empirical estimate of what is prudent rather than evidence based. The only bolus referenced in the Rivers trial was the 20 ml/kg actual body weight in 30 minutes, an amount used only to reject from the study those who were initially hypotensive but responded to fluid. To be sure, an initial bolus may serve a useful purpose by moving patients more quickly towards resuscitation pressure, volume or perfusion goals. Determination of the actual volume required to reach those goals will be facilitated by early monitoring. Any fluid prescription without monitoring is at best a guess at what will be required, and influenced by a myriad of constantly changing interactive variables such as capillary permeability, source control, vasodilation, cardiac depression, coagulopathy, microvascular & mitochondrial dysfunction and reversibility, comorbidities and genetic predisposition. Ron Elkin MD California Pacific Medical Center San Francisco On Thu, May 29, 2014 at 12:59 PM, Terry Clemmer <[email protected]> wrote: > We use predicted body weight calculated from the height rather than > actual body weight. It is only the lean body mass that counts. > > > > Terry P. Clemmer, MD > > Director: Critical Care Medicine > > LDS Hospital > > Professor of Medicine > > University of Utah School of Medicine > > Salt Lake City, Utan 84143 > > > > Work Phone: 801-408-3661 > > Work Fax: 801-408-1668 > > > > *From:* Sepsisgroups [mailto:[email protected]] *On > Behalf Of *Kelsey K. Solano > *Sent:* Wednesday, May 28, 2014 8:05 AM > *To:* [email protected] > > *Subject:* [Sepsis Groups] Fluid Bolus in pts. with weight > 200 kg > > > > I am wondering whether there are any recommendations regarding fluid > resuscitation in patients weighing >200 Kg? Our physicians have expressed > concern about the recommended fluid bolus for patients who are > 200 Kg and > potential for CHF exacerbations. Are there any resources that address this > concern or any modifications for this patient population? Also, is it > always recommended to go with 30 ml/kg based on current weight or should we > be calculating ideal weight when determining bolus volume? Currently we are > using the patient's actual weight on admission for bolus calculations. Any > clarifications regarding the fluid bolus would be greatly appreciated. > > > > Thanks, > > > > Kelsey K. Solano > > Sepsis Coordinator > > Email: [email protected] > > Office: 574-335-2438 > > > > _______________________________________________ > Sepsisgroups mailing list > [email protected] > http://lists.sepsisgroups.org/listinfo.cgi/sepsisgroups-sepsisgroups.org > >
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