fluid management

1. Nutrition & Fluid therapy in
peri-operative period
K.Kashyap
1st year P.G.

2.  In healthy individuals water constitues
approximately 60% of TBW.
 This is divided between intra and
extracellular compartments.
 The extracellular compartment is
further divided into interstitial,
intravascular & transcellular
compartments.

3.  Movement between compartments is
limited by membranes.
 The vascular endothelium forms the
barrier between the intravascular and
interstitial spaces, with the endothelial
glycocalyx present on the vascular
side and the cleft between endothelial
cells closed by tight junctions.

4.  The movement of larger molecules such
as protein is limited by the glycocalyx,
and they require an active transport
system.
 Disruption to the glycocalyx is reported in
a variety of disease states, leading to
extravascular movement of larger
molecules including proteins and an
alteration in intra and extravascular
oncotic pressure, with a subsequent
movement of water extravascularly.

5.  With an evolving and changing
evidence base, there have been
significant developments in clinical
practice.
 Changes have been seen in all
domains, from fluid choice, to volume
of administration, to which end points
to target.

6.  Historically, there was a trend for high
volume or liberal fluid therapy, this
shifted towards a focus on restrictive
fluid therapy or goal directed fluid
therapy.
 increasing evidence base
demonstrates that perioperative fluid
management alters patient outcomes

7.  The consequences of hypovolaemia,
with haemodynamic compromise,
impaired oxygen delivery and
subsequent organ dysfunction are well
recognised.
 Conversely, fluid overload has
resultant multisystemic effects,
including interstitial oedema with
implications on gas exchange, renal
function and the gastrointestinal
system.

8. Fluid choice
 Historically, colloids were frequently used; it
was believed that as colloids were more likely
to remain intravascularly than crystalloids,
and greater haemodynamic stability could be
achieved with lower volumes.
 Consistent evidence of increased acute
kidney injury, need for renal replacement
therapy and 90 day mortality in patients
receiving colloids, particularly starches,
compared to patients receiving crystalloids,
crystalloids now form the mainstay of
treatment.

9.  Generally either 0.9% saline or a
balanced solution such as Hartmann’s is
used. 0.9% saline has a chloride
concentration of 154 mmol.
 Its use can lead to a hyperchloremic
acidosis.
 Post-operative hyperchloremia has been
linked with increased post-operative
complications, such as acute kidney
injury and increased 30-day mortality,
although causation has not been proved.

10.  Balanced solutions, which include
Hartmann’s solution or Plasmalyte are
considered more physiological and
generally preferred for perioperative
fluid management.

11. Liberal v/s restrictive
stratergies
 The period of fasting preoperatively,
intraoperative surgical time, surgical
losses and insensible losses all need
to be considered.
 In healthy volunteers, a period of
pre-operative fasting was shown to
have no effect on markers of preload.

12.  Evidence for insensible losses, or third
space losses, requiring liberal
replacement, is inconsistent.
 The use of basic haemodynamic
variables, for example changes from
baseline heart rate and blood
pressure, leads to reactive rather than
proactive management.

13.  It is well acknowledged that 20% of the
circulating volume must be lost before
any change in these parameters is seen.
 Both general anaesthesia and neuroaxial
anaesthesia can cause perioperative
hypotension, which is not necessarily
indicative of intravascular fluid depletion,
but decreased vascular tone.
 Conversely, fluid overload may not
manifest until adverse end organ effects
are seen.

14.  The definition of what constitutes a liberal
versus a restrictive fluid strategy varies but
can be in the region of >5 L for a liberal
strategy, and <3 L for a conservative strategy.
 the trend is towards increased morbidity and
mortality in the liberal fluid groups particularly
those undergoing high risk or major surgery.
 A positive fluid balance has been shown to be
associated with increased mortality.

15. GOAL DIRECTED THERAPY
 aims to meet the patient’s increased
oxygen demand incurred in the
perioperative period, by targeted
intervention, guided by haemodynamic
monitoring.
 Perioperative GDT describes fluid
administration, with the aim of optimising
a patient’s cardiac function and
ultimately oxygen delivery. It is used for a
time limited period, both during and after
a surgical intervention.

16.  The fluid is given with the aim of
increasing preload and therefore
stroke volume and cardiac output to
potentially supranormal targets.
 GDT evolved mainly focusing on
stroke volume optimisation with less
invasive cardiac output monitors.

17.  GDT carried on being studied in
different settings, with multiple studies
showing significant decreases in
morbidity and mortality, particularly in
higher risk patient groups.
 hypothesised that increased fluid and
inotrope use, may predispose to
increased complications but in fact,
early GDT therapy was shown to be
associated with decreased
cardiovascular events.

18. ASSESSMENT OF FLUID
STATUS
 In addition to a thorough clinical
examination, echocardiography is an
increasingly useful bedside tool for the
assessment of a patient’s fluid status.
 Echocardiography can be used to
assess preload, contractility and
afterload and changes in these
parameters in response to a fluid
challenge observed.

19. FLUID EXPANSION, FLUID
RESPONSIVENESS AND
ITS PREDICTION
 Venous return is equal to cardiac
output.
 Assessing fluid responsiveness is
important every time fluids are given.
 If possible the response to fluids
should be predicted before their
administration.

20.  The prediction of a patient’s fluid
responsiveness aims to identify those
who may benefit from an increase in
intravenous volume with an increase in
stroke volume and cardiac output.
 Predictors of fluid responsiveness
include high pulse pressure variation,
stroke volume variation, vena cava
collapsibility index and end occlusion
expiratory test.

21.  When the decision to administer fluids has
been made, the best way to do it is with a
fluid challenge.
 A fluid challenge can be used to assess for
fluid responsiveness without the limitations
associated with pulse pressure variation or
stroke volume variation and it can be both
diagnostic and therapeutic.
 A patient is deemed fluid responsive if stroke
volume or cardiac output increase by at least
10% following a fluid challenge.

22. FLUID CHALLENGE
 The assessment of fluid responsiveness
relies on the administration of a fluid
challenge, however the method of
administration of a fluid challenge shows
significant inter-user variability.
 Crystalloids accounted for 74.3% of
fluids used for the challenge, of these
45.9% were 0.9% saline and 53.5%
balanced solutions including Hartmann’s
solution, a range of colloids accounted
for the remaining 25.6%.

23.  If the fluid challenge is to be effective
in testing fluid responsiveness then it
needs to increase Pmsf.(mean
systemic filling pressure).
 A fluid challenge of 4 ml/kg is the
option which most reliably stresses the
cardiac system, to differentiate
responders from non-responders.

24.  It is important that the assessment of
fluid responsiveness is used as part of
a complete assessment of a patient’s
clinical condition and fluid status to
determine whether they need or it is
appropriate for them to receive further
intravenous fluids.

25. MACRO AND
MICROCIRCULATION
COHERENCE
 The focus in fluid management has
historically been on the
macrocirculation, with an assumption
there will be haemodynamic
coherence or that correction of the
haemodynamics at the
macrocirculatory level will translate to
normalisation of perfusion and oxygen
delivery in the microcirculation.

26.  there were no significant differences in
the systemic haemodynamic variables
between patients who did and did not
develop post-operative complications.
 However, at the microcirculation level,
both the proportion and density of
perfused small vessels and the
microvascular flow index were reduced
both pre and post-operatively in those
patients who developed post-operative
complications.

27.  Surrogate markers of microcirculation
such as lactate or skin temperature
correlate poorly with direct
visualisation of flow.
 Patients with macrocirculatory
markers of hypoperfusion may have
either low or normal microcirculatory
flow.

28.  The choice of fluid has been shown to
alter coherence.
 0.9% saline has been shown to be the
least effective of the commonly used
fluids in improving microcirculatory
flow and promoting haemodynamic
coherence.

29. Perioperative Nutrition
Support
 Which patients need perioperative
nutritional support?
◦ albumin levels are used stratify nutritional
risk.
◦ Albumin levels are an accurate and
inexpensive indicator of potential
morbidity.

30.  It is recommended that in esophageal,
gastric and pancreatic surgery, when
albumin is below 3.25 g/dl, the
operation should be postponed
whenever possible for additional
nutritional and metabolic support.
 serum albumin is the best single
indicator of postoperative
complications.

31.  visceral proteins (albumin, transferrin,
prealbumin, and retinol-binding protein)
and various combinations of the two, no
single assessment tool or laboratory
value consistently yields information that
would change nutritional practice in the
acute setting.
 However ratio of prealbumin (t ½ - 48 h)
and C-reactive protein(t ½ - 8h) may be
of some value.

32.  C-reactive protein may indicate when
the patient starts to produce visceral
proteins as the inflammatory response
wanes.

33.  What is the optimal route of nutrient
delivery?
◦ The optimal route of preoperative nutrition
is clearly the enteral route whenever
feasible.
◦ The use of total parenteral nutrition in the
preoperative period has limited utility
except in the severely malnourished.

34.  Caution is the key in this labile
population, as there have been reports
of jejunal feeding inducing small-bowel
necrosis in critically ill and immediately
postoperative patients.

35.  What is the optimal time for nutrient
delivery?
 Preoperative preparation of the patient
gained support following several
landmark studies
◦ Major morbidity could be reduced by
approximately 50% in patients undergoing
resection for malignancy of the esophagus,
stomach or pancreas.
◦ This benefit was noted in both the well
nourished and malnourished patient

36.  The immune-modulating formula in
addition to their regular diet.
 The formula contained additional
arginine,w-3 fatty acids and nucleic
acids, and resulted in significant
decreases in infectious morbidity,
length of hospital stay.

37.  Another area of recent interest in the
preoperative setting, is carbohydrate
loading.
 This strategy utilizes an isotonic
carbohydrate solution given at
midnight on the night before surgery,
then 3 h preoperatively, to maximally
load the tissues with glycogen prior to
the surgical stress.

38.  Recent studies reported that a group
receiving multimodality treatment,
including avoidance of drains,
controlled perioperative sodium and
fluid administration, epidural
anesthesia, early mobilization and
carbohydrate loading, displayed less
hepatic insulin resistance, decreased
postoperative nitrogen loss, and better
retention of muscle function.

39.  The optimal time to start postoperative
nutritional intervention is significantly
influenced by a host of factors such as
age, premorbid conditions, route of
delivery, metabolic state, organ
involvement.
 benefits of early enteral feeding
are,prevention of adverse structural and
functional alterations in the mucosal
barrier, augmentation of visceral blood
flow,and enhancement of local and
systemic immune response.

40.  Numerous recent reports continue to
support the concept that bowel sounds
and evidence of bowel function –
passing flatus or stool – is not required
for resumption of oral intake.
 These studies concluded that early
postoperative feeding was safe and
did not increase morbidity.

41.  Although the benefits of early enteral
feeding have been uniformly reported,
feeding in the immediate postoperative
period in critically ill patients yields an
entirely different set of problems.
 Gastrointestinal dysfunction in the setting
of the intensive care unit (ICU) ranges
from depending on the diagnosis,
premorbid condition,mode of ventilation,
medications, and metabolic state.

42.  Postoperative gastrointestinal
dysfunction can be separated into
three general categories:
◦ mucosal barrier disruption,
◦ altered motility and atrophy of the
mucosa, and
◦ Gut associated lymphoid tissue.

43.  Barrier disruption appears most
commonly to be associated with
splanchnic hypoperfusion, which is
precipitated by numerous factors in the
critical care setting and immediate
postoperative period, including
◦ hypovolemia,
◦ increased catecholamines,
◦ Increased proinflammatory cytokines and
◦ decreased cardiac output.

44.  All ultimately lead to reduced mucosal
blood flow, barrier disruption, altered
gastrointestinal motility, and changes in
the bacterial flora and virulence of the
organisms.
 Following visceral manipulation,
activation of transcription factors is
noted, with upregulation of intracellular
adhesion molecule-1 on the endothelium
of the muscularis vessels.

45.  Leukocyte extravasation into the
muscularis occurs, with resultant
upregulation of inducible nitric oxide
synthase, cyclooxygenase-2, interleukin-
6, and signal transducer and activator of
transcription-3 protein phosphorylation.
 This inflammatory focus then decreases
the contractile response and alters
electrical activity, resulting in ileus.

46.  Recent approaches to maximize gut
function in the postoperative and critical
care settings include
◦ maintenance of visceral perfusion,
◦ strict glycemic control,
◦ electrolyte correction,
◦ early enteral feeding, and
◦ minimization of medications that alter
gastrointestinal function, such as
anticholinergic agents, narcotics, and high-
dose pressors.

47. What is the optimal nutrient to
deliver?
 Regarding specific macronutrients, the
requirement for
◦ carbohydrates is estimated at 3 to 6
mg/kg per min(roughly 200–300 g/day),
◦ protein is 1.25–2.0 g/kg per day, and
◦ lipids is 10–25% of total
calories,depending on the route and lipid
composition.

48.  Ideally, one would like to provide
sufficient nutrients to minimize the
catabolic loss associated with stress,
injury, and surgery while avoiding the
problems associated with overfeeding,
such as hyperglycemia, azotemia,
excess CO2 production.
 The most recent trials suggest additional
benefit with immune-modulating
compared to the standard formulas.

49. Immune modulating formulas
 arginine to be beneficial, especially in
the surgical and trauma population.
 Glutamine is the other conditionally
essential amino acid that has recently
gained even greater support in the
critical care setting.

50.  Glutamine has been reported to offer a
myriad of benefits, including
maintenance of acid/base balance,
provision of primary fuel for rapidly
proliferating cells (i.e. enterocytes and
lymphocytes), synthesis of glutathione
and arginine, lowering of insulin
resistance, and function as a key
substrate for gluconeogeneis.
 Recent evidence that glutamine can
induce heat-shock protein is yet another
beneficial molecular effect of this amino
acid.

51. Elective
surgery
general septic trauma burns
Acute
lung
injury
arginine beneficial Possible
benefit
glutamine Possible
benefit
beneficial Possibly
beneficial
Possibly
beneficial
Omega 3
FFA
beneficial
Anti-
oxidants
Possibly
beneficial
Critically ill

52.  Understanding lipid modulation of the
metabolic response in the surgical and
critical care setting is hampered
because lipids are traditionally given
as one of many active components of
an immune-enhancing formula.
 recent data demonstrates that
eicosapentaenoic acid modulates
arginine metabolism.

53.  The w-3 fats in fish oil have multiple
beneficial effects in the perioperative
period, including
◦ modulation of leukcocyte function and
◦ regulation of cytokine release through
nuclear signaling and
◦ gene expression

54.  w-3 fats downregulate the
proinflammatory response to stressful
stimuli.
 It has been recently reported that w-3
fatty acids given intravenously at a
dose of 0.11 g/kg per day for a mean
of 8.7 days demonstrated a decrease
in mortality.

55.  The route of delivery of v-3 fats may
be of importance.
 Utilizing the enteral route, it takes
approximately 3 days to achieve
adequate v-3 fat levels in the cellular
membrane. However, when given
parenterally, a clinically relevant
response can be achieved in 3 hr.

56. How much to feed?
 The caloric requirement for the perioperative
and ICU patient is evolving as the concept of
hypocaloric feeding, or so-called permissive
underfeeding, in the early ICU and
postoperative period gains support.
 The argument states that a relative ‘anorexia
of illness’ develops with significant injury and
that supply of nutrients during this period
induces a proinflammatory state which then
exacerbates the condition.
 This concept has led to advocate hypocaloric
feeding in the early phases of critical illness.

57.  the caloric delivery currently
considered safe for the perioperative
period is in the range of 20–30 kcal/kg
per day.