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denitive decision about that will be taken. In any case, at the state of the art, the dilemma
about the ideal solution still remain unsolved and new scenarios should be opened.
Suggested References
Hydroxyethyl Starch or Saline for Fluid Resuscitation in Intensive Care John A et Al. (NEJM
2012)
Colloids versus crystalloids for uid resuscitation in critically ill patients (Review) Perel P, Roberts
I, Ker K Cochrane Database Syst Rev. 2013 Feb
JAMA. 2013 Feb 20;309(7):678-88. doi: 10.1001/jama.2013.430. Association of hydroxyethyl
starch administration with mortality and acute kidney injury in critically ill patients requiring
volume resuscitation: a systematic review and meta-analysis
13.14 Comparison Between Balanced
and Unbalanced Solutions
When evaluating the effects of different volume-replacement strategies, the electro-
lytic composition has to be taken into account. Hyperchloremia caused by neither
non-balanced nor non-plasma-adapted solutions can alter kidney sensitivity to vaso-
constrictors, leading to increased vascular tone and a reduction in glomerular ltra-
tion. Balanced and plasma-adapted solutions avoid hyperchloremia, with a lower
risk of kidney injury, even in cardiac surgery patients, as well as a reduced bleeding
risk and inammatory response (Agrò et al. 2013a).
Furthermore, there is growing evidence that the use of balanced solutions reduces
the need for blood products because of the improved coagulation status (Agrò et al.
2013a; Roche et al. 2002; Martin et al. 2002). Finally, balanced plasma-adapted
solutions better maintain acid–base balance, alterations of which may worsen the
hemodynamic status of cardiac patients (Agrò et al. 2013a; Base et al. 2011) (see
Chap. 15).
13.15 How Much Fluid?
The second main concern of the debate on uid management is “how much to ll”
the patient. In fact, although there are many evidences about the benets of uid
administration in restoring and maintaining an adequate IVS volume, the risk to
develop congestive heart failure with interstitial edema, respiration complication,
and wound healing delay remains in the case of excessive uid administration
(Agrò et al. 2013a; Agrò and Vennari 2013b). Moreover, in daily practice, practitio-
ners have to face with the lack of consensus guidelines and the limited equipment
for hemodynamic monitoring. As a consequence, it is not surprising that the need
for rescue therapy in shock patient, congestive heart failure, and prolonged mechan-
ical ventilation is yet too frequent both in operating room than in ICU (Habicher
et al. 2011).
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In a 50-year ongoing debate, literature proposed many strategies for periopera-
tive uid management in cardiac surgery patient (Agrò et al. 2013a; Agrò and
Vennari 2013b).
13.15.1 Liberal vs. Restricted Approach
Historically, there have been two main approaches to uid management: liberal and
restrictive. Studies used different references to establish the nature (liberal or
restrictive) of uid administration. As a consequence, literature may appear
contradictory.
Considering a normal water assumption of 25–35
mL/Kg, a patient with no par-
ticular uid loss should be treated with 1,75–2,75 L/die (Powell-Tuck et al. 2008).
According to this basal requirement, a uid strategy may be considered (Varadhan
and Lobo 2010):
• Liberal, when more of 2,75 L/die of uid is administered
• Restrictive when less of 1,75 L7Die is administered
In the liberal approach, uid replacement has been funded on the estimation of
preoperative loss due to fasting, intraoperative loss due to perspiration insensibilis,
urine output and bleeding, and anticipated postoperative loss due to uid shifting in
the third space (Fanzca 2012; Shires et al. 1961). According to this approach, the
surgical patient is hypovolemic before the start of the procedure because of fasting
and intestinal cleaning preparation (when necessary); the perspiratio has a great
increase when the continuity of skin is interrupted by the surgical procedure; the third-
space shifting is the natural response to surgical stress, an effective ECS (Jenkins et al.
1975; Campbell et al. 1990; Holte and Kehlet 2002). Finally, the kidney is able to
eliminate any uid overload (Watenpaugh et al. 1992). As a consequence, a preopera-
tive uid load is needed and should consist of about 20 ml/kg/h IV uids (Chappell
et al. 2008; Campbell et al. 1990; Maharaj et al. 2005) as the administration of about
20
mL/Kg/h of IV uids (Bamboat and Bordeianou 2009).
Although the use of a liberal approach was supported by some studies demon-
strating an improvement of tissue perfusion and oxygenation and the reduction of
inammatory response and of organ failure risk (Maharaj et al. 2005; Arkilic et al.
2003; Mythen and Webb 1995; Holte et al. 2004; Lobo et al. 2010; Hiltebrand et al.
2007), it has been related with a uid overload potentially impacting on patient
outcomes (Nisanevich et al. 2005; Lobo et al. 2002). A mathematical model demon-
strated that using a liberal approach causes a massive retention of uid in the
stressed tissues, especially when infusion overcomes 10 mL/kg/h, with reduced or
no impact on IVS volume (Tatara and Tashiro 2007). Moreover, in a normal organ-
ism the surgical stress increases the capacity of uid overload elimination, but not
in a proportional way to the administration. As a consequence, if administration is
excessive, uids will accumulate (Holte et al. 2007a).
Lowell et al. found that at ICU admission, 40 % of surgery patients presented an
increase of total body water of 10 % or more (Lowell et al. 1990). This uid over-
load may need days to be eliminated, determining a body weight gain. The gain is
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mainly due to interstitial edema responsible for heart failure; pulmonary edema and
ARDS; increased abdominal pressure, with possible development of compartmen-
tal syndrome; tissue hypoperfusion and hypoxia, slowing down wound healing and
increasing risk of dehiscence; ileus; and MOF (Reid et al. 2003; Bamboat and
Bordeianou 2009; Lobo et al. 2001; Balogh et al. 2003; Shandall et al. 1985;
Sheridan et al. 1987; Lobo 2004). Finally, uid and sodium overload causes cellular
membrane hyperpolarization, neurotransmitter metabolism alteration, and mito-
chondrial dysfunction (Wilkes et al. 2001; Petty and Ashbaugh 1971).
At the state of the art, it is not clear if a liberal uid administration is the cause
of the consequence of uid shift in the third space. In animal models, the surgical
damage (mechanical and inammatory) has been shown as the rst cause of uid
shift that is increased by abundant uid administration (Chan et al. 1983). However,
literature on major abdominal surgery demonstrated the liberal approach may aug-
ment the risk of complication development, increase hospital stay, and worsen out-
comes (Varadhan and Lobo 2010; Nisanevich et al. 2005; Brandstrup 2006;
Brandstrup et al. 2003).
Moreover, evidence demonstrated that Shire theory premises were not very cor-
rect. In fact, it has been shown that preoperative fasting does not produce a signica-
tive reduction in IVS volume (Jacob et al. 2008); basal perspiratio is 0,5 mL/Kg/h,
and during surgery, it is no more than 1 mL/kg/h (Lamke et al. 1977); the stress
response to surgery is responsible of an inappropriate increase of ADH and aldoste-
rone levels, determining an overload of water and sodium; nally, a “primitive”
third space does not exists (Chappell et al. 2008). These evidences suggest the use
of a restrictive approach to uid management, rst proposed by Moore et al. (1955).
Many studies demonstrated that a restrictive management (dened as a contained
infusion respected liberal approach) reduces the risk of complications and hospital
stay, favoring wound healing and postoperative recovery of organ function (espe-
cially abdominal) and lowering the incidence of cardiopulmonary events, with no
cases of prerenal AKI (Chappell et al. 2008; Nisanevich et al. 2005; Lobo et al.
2002; Moyer 1950). On the other hand, when a real restrictive administration is
realized (infusion <1,75 L/die), perioperative morbidity increased (Vermeulen et al.
2009; Holte et al. 2007b; MacKay et al. 2006). In fact, a restrictive management
may cause hypovolemia with hypoperfusion and DO
2
reduction, increasing the risk
of organ damage. Moreover, there is an increase viscosity of body uids potentially
leading to microcirculation alteration and microthrombosis, pulmonary mucus con-
centration with bronchial obstruction, and atelectasis development (Lobo and
Allison 2005) (Fig. 13.17).
Despite scientic evidences, the discussion remains opened about the ideal
uid management in the cardiac surgery patient, because works are widely
different, and no studies have been conducted on cardiac surgical population. For
these reasons, the literature of the last two decades has emphasized a guided
uid management as an alternative to both restrictive and liberal approach
(Habicher et al. 2011). It consists on the administration of uids according to the
evaluation of physiological parameters and hemodynamic variables. This
approach is called goal- directed therapy (Agrò and Vennari 2013b).
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13.15.2 Goal-Directed Fluid Therapy
In cardiac surgery patient, a rational uid administration is one of the main tools
useful to optimize tissue perfusion (Habicher et al. 2011).
Goal-directed therapy (GDT) is a complex strategy for uid infusions aimed at
optimizing tissue perfusion and oxygenation. Through hemodynamic monitoring,
GDT allows physicians to administer uids and/or use others therapies, such as
inotropic or vasoactive drugs, only to those patients who need them, in order to
assure sufcient DO
2
to fulll the metabolic requirement of the particular patient.
With GDT, hemodynamic management is therefore personalized (Agrò and Vennari
2013b).
13.15.2.1 Physiological Basis
Management of both critically ill and major surgery patients is mainly aimed at
assuring adequate tissue perfusion and oxygenation. A continuous supply of oxygen
is needed because it is indispensable for aerobic metabolism (Agrò and Vennari
2013b).
Physiologically adequate DO
2
is assured by cardiovascular and respiratory sys-
tems, and it corresponds to the quantity (in mL) of oxygen per minute carried to the
tissues (Agrò and Vennari 2013b; Lees et al. 2009).
DO
2
is dened by the following equation (Agrò and Vennari 2013b):
DO mL /min = cardiac output CO arterialoxygencontentCaO
2 2
() ()
×
()
(13.1)
Hypovolaemia Hypervolaemia
Increasing morbidity
Hypotension;
SIRS;
Sepsis;
Multi organ failure;
Increased post op nausea;
Organ hypoperfusion;
Impaired tissue oxigenation
Interstitial edema;
Ileus;
PONV;
Pulm complications;
↑
Cardiac demands;
Poor wound healing;
Delayed gastric emptying
Fig. 13.17 Liberal and restrictive approaches: consequences on morbidity
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DO
2
physiologically corresponds to 900–1,100 mL/min or to 500–600 mL/min/
m
2
if reported as body surface area (DO
2
I) (Agrò and Vennari 2013b).
Considering the factors determining CO and CaO
2
, Eq. 13.1 can be rewritten as
(Agrò and Vennari 2013b):
DO mL /min =HRSV1,34HbSaO + 0.003 paO
22
2
()
×
()
××
()
×
()
(13.2)
where:
•
HR is the heart rate.
• SV is the stroke volume.
• 1.34 is the number of mL of oxygen carried by hemoglobin at 100 % saturation.
• Hb is the amount of hemoglobin in g/dL.
• SaO
2
is the arterial O
2
saturation in arterial blood.
• 0.003 is the solubility coefcient of oxygen.
• PaO
2
is the partial O
2
pressure of arterial blood.
Thus, oxygen delivery can be improved by modifying:
• SV, by using inotropic or vasoactive drugs (post-load) and uid administration
(preload)
• Hb, by the transfusion of red cells
• SaO
2
and paO
2
, by O
2
therapy and in some cases by mechanical ventilation (Agrò
and Vennari 2013b)
Oxygen demand consumption (VO
2
) is the quantity (in mL) of oxygen consumed
by the tissue per minute. It depends on the metabolic state and it is increased by
surgical stress and critical conditions. VO
2
may be described by the following rela-
tionship (Agrò and Vennari 2013b):
VO mL /min = caridac output CO [arterialO content(Ca
O)
ven
22
2
() ()
×
− oous Ocontent(CvO)
22
(13.3)
Equation 13.3 can be rewritten as (Agrò and Vennari 2013b):
VO mL /min =(FC SV) [(1,34HbSaO )
+(0.003 paO) (1.34 Hb
22
2
()
×× ××
×××− SSvO)+ 0.003 pv
O]
22
×
()
(13.4)
where:
• CO and CaO
2
are described by the same factor as in Eq. 13.2.
• SvO
2
is the saturation of mixed venous blood.
• PvO
2
is the partial O
2
pressure in mixed venous blood (Agrò and Vennari 2013b).
VO
2
is about 200–300 mL/min (110–160 mL/min/m
2
if reported as body surface
area) at basal metabolism (Roberts and Bratton 1998). Under stress conditions it
may increase four- to sixfold.
O
2
extraction (O
2
ER) is the fraction of DO
2
released to the tissues per minute
(Agrò and Vennari 2013b). It is a tissue oxygenation index, expressed as:
OER=
VO
DO
2
2
2
(13.5)
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Under basal conditions, the ratio is 0.25, but it can increase in order to assure
VO
2
. In fact, normally, VO
2
is maintained despite wide-ranging DO
2
values, through
an increase of O
2
ER. Below a critical value of DO
2
(critical DO
2
), O
2
ER can no
longer increase, and VO
2
becomes ow dependent (Agrò and Vennari 2013b).
Tissue hypoxia appears and anaerobic metabolism starts. The tissue hypoxia causes
unbalance between ATP production and ATP demand. A reduction in cAMP and
cGMP levels activates the endothelium, reducing its barrier function and causing
the release of pro-inammatory cytokines, leading to capillary leak syndrome.
Disruption of the endothelial barrier exposes the blood to procoagulant factors and
leukocyte adhesion molecules. Leukocytes and complement are activated, leading
to a systemic inammation with organ hypoperfusion and failure (multiorgan fail-
ure). The detection and prevention of tissue hypoxia is therefore crucial, especially
in cardiac surgery patient (Agrò and Vennari 2013b; Lamke et al. 1977).
A rational approach to uid therapy (GDT) is the most readily available and
simplest tool to assure adequate DO
2
. Some patients have reduced compensatory
mechanisms when VO
2
increases, because of comorbidities (cardiovascular or pul-
monary diseases), and thus have a higher probability of reaching the critical DO
2
under stress conditions, such as surgery. Cardiac surgery patients are high-risk
patients who are likely to benet from a GDT approach (Agrò and Vennari 2013b).
13.15.2.2 Hemodynamic Variables in GDT
The rational approach to uid administration in GDT is based on the prediction of
uid responsiveness. Fluid-responder patients are those who, according to Starling’s
law, will benet from uid loading in terms of hemodynamic stability and DO
2
(Agrò and Vennari 2013b). It has been shown that if uid responsiveness is not
assessed, only 40–72 % of critically ill patients respond to uid therapy with a sig-
nicant increase in stroke volume (Michard and Teboul 2002). It is immediately
evident that uid responsiveness is not evaluable on the bases of the sole clinic
(Grebe et al. 2006). In fact, clinical parameters change later than the effect volume.
This should bring to a tardive treatment of hypovolemia, potentially fatal for cardiac
surgery patients (Grebe et al. 2006; Grocott et al. 2005).
Dened hemodynamic variables are necessary to evaluate volume status and to
test uid responsiveness. These can be divided into static and dynamic. Static vari-
ables indicate hemodynamic status at a specic time, for the preload value at that
time. An example of static variable is the value of CI obtained in a single thermodi-
lution. Dynamic variables indicate hemodynamic changes in response to a periodic
variation in preload. Static indexes are comparable to a picture, while dynamic ones
to a movie. Dynamic variables are better indicators of uid responsiveness than
static ones (Agrò and Vennari 2013b; Lees et al. 2009).
Historically, lling pressures (CVP, MAP, and PCWP) were used to guide intra-
vascular volume therapy. In cardio-surgical ICU, CVP is the most used (87 % of
intensivists), followed by MAP (84 %) and PCWP (30 %) (Kastrup et al. 2007).
Many studies have shown that CVP does not adequately reect preload and fails to
predict uid responsiveness (Agrò and Vennari 2013b; Kastrup et al. 2007; Cavallaro
et al. 2008; Marik et al. 2008). In one study, PCWP was found to adequately predict
uid responsiveness in 19 patients who underwent CABG (Bennett-Guerrero et al.
2002). Other studies found a signicant CVP and PCWP increase after a uid
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challenge, but they did not correlate to an increase in SV (Wiesenack et al. 2001;
Brock et al. 2002). Moreover, pressure parameters are altered by intra-abdominal
pressure variation, modication of cardiac compliance, pulmonary resistance, and
cardiac pathologies (Marik et al. 2008). As a result, they are not very reliable and
useful in cardiac surgery patients who present at least one of these conditions
(Habicher et al. 2011; Wittkowski et al. 2009; Michard et al. 2003; Hofer et al. 2005a;
Reuter et al. 2002a, b; Sakka et al. 2009; Breukers et al. 2009a, b; Goedje et al. 2000).
Pulse wave analysis allows the assessment of other functional hemodynamic
parameters, such as stroke volume variation (SVV), pulse pressure variation (PPV),
and continuous CI (Agrò and Vennari 2013b). Intermittent transpulmonary thermo-
dilution can be used to calibrate pulse wave analysis, enhancing the reliability of CI
measurements, according to the monitoring system applied (Agrò and Vennari
2013b).
Pulse pressure is dened as the difference between systolic and diastolic pressure
for each heartbeat (Roberts and Bratton
1998). PPV corresponds to the variation in
pulse pressure at different heartbeats induced by variations of the intrathoracic pres-
sure due to mechanical ventilation (Agrò and Vennari 2013b) (Fig. 13.18). A PPV
cutoff value of 12 % has been shown to be useful to identify responder patient (PPV
>12 %) and nonresponder patients (PPV <12 %) (Auler et al. 2008). In a study on
CABG patients comparing PEEP and uid infusion effects on hemodynamics, PPV
was found to be the best predictor of uid responsiveness with respect to PCWP and
other variables (Bendjelid et al. 2004). PPV use in guiding volume therapy has been
demonstrated, suggesting a possible improvement in outcome after high-risk sur-
gery (Lopes et al. 2007).
SVV is based on cyclic changes in the SV due to intrathoracic pressure during
mechanical ventilation (Agrò and Vennari 2013b) (Fig. 13.19).
SVV= SVmaxSVmin /SVmean−
()
It is conceptually similar to PPV, but more precise and reliable (Agrò and Vennari
2013b). SVV has been found to consistently predict uid responsiveness, with
Airway pressure
Arterial pressure
50
10
120
80
1 s
cmH
2
0 mmHg
Fig. 13.18 PPV and
intrathoracic pressure. In the
inspiratory phase of
mechanical ventilation, the
intrathoracic pressure
increases, reducing preload
and consequently increasing
PPV. In expiration,
intrathoracic pressure
decreases, increasing preload
and consequently reducing
reduction in PPV (Agrò and
Vennari
2013b, pp. 71–92)
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threshold values of 11–13 % (Agrò and Vennari 2013b; Marik et al. 2009; Benes
et al. 2010). SVV may indicate the actual position on the Frank–Starling curve.
When the heart operates on the ascending limb of the Frank–Starling curve, the
intrathoracic pressure induces large changes in preload and SV (SVV >13 %), indi-
cating a preserved preload reserve and an improvement after uid administration
(uid responders). By contrast, at the plateau of the Frank–Starling curve, small
changes in SV are observed (SVV <13 %), representing a lower preload reserve and
a minimal or no improvement after uid administration (uid nonresponders)
(Fig. 13.20). In this case, inotropes may be required (Agrò and Vennari 2013b). In
a study on 20 patients who underwent cardiac surgery, SVV modication correlated
to CI changes (Reuter et al. 2002b).
However, there are some limitations that may exclude a valid use of SVV (Agrò
and Vennari 2013b):
• Right ventricular failure
• Arrhythmias
• Spontaneous breathing
• Ratio heart rate/respiratory rate <3.6
• Low tidal volume (<8 mL/kg)
1.2
0.9
0.6
0.3
0
01 2
Time (s)
34
Voltage (V)
Fig. 13.19 Pulse wave
analysis and SVV: the area
under the curve corresponds
to the SV. Knowing the HR,
CI may be calculated
continuously (Agrò and
Vennari
2013b, pp. 71–92)
C.O.L
/min
Right atrial pressure mmHg
Fluid non responders
Fluid responders
–1 01 2
Fig. 13.20 Fluid
responsiveness and Frank–
Starling law (From Agrò and
Vennari
2013b, pp. 71–92)
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In fact, Reuter et al. (2003) demonstrated that tidal volume may affect reliability
of SVV value in cardiac surgery patients. In a similar population, SVV was found
to be reduced by high blood pressure value and increased by high airway pressure,
without effective change in volemic status (Habicher et al. 2011).
Both high PPV and SVV are indicators of hypovolemia, indicate uid respon-
siveness, and correlate to the CI increase after uid challenge administration
(Habicher et al. 2011; Wiesenack et al. 2003; Hofer et al. 2005b). This evidence was
conrmed in a study on off-pump CABG patients, in which both SVV and PPV
strongly correlated to CI improvement after a uid challenge, with respect to lling
pressure (Habicher et al. 2011; Belloni et al. 2008). As a consequence, dynamic
parameters such as PPV and SVV are able to adequately distinguish uid-responder
and uid-nonresponder patients and are suitable to guide uid management in the
perioperative period of cardiac surgery, with respect to lling pressure (Habicher
et al. 2011; Brock et al. 2002).
GEDV (global end-diastolic volume) is a volumetric parameter easily obtainable
through transpulmonary thermodilution. It may index to body surface (GDVI)
(Wittkowski et al. 2009). It has been showed as a better marker of cardiac preload
than CVP (Agrò and Vennari 2013b). This evidence was conrmed by a study
where GEDVI was compared to PAC pressure through echocardiography: it corre-
lated with ventricular preload (Hofer et al. 2005a). However, it is a static parameter
that does not allow the evaluation of cardiac responsiveness to uid loading (Agrò
and Vennari 2013b).
ITBV (intrathoracic blood volume) is another volumetric index of preload
(ITBVI). In cardiac surgery patients with hypovolemia, ITBV has been shown to
signicantly correlate to SV increase after a uid challenge, with respect to CVP
and PCWP (Habicher et al. 2011; Brock et al. 2002). These results are conrmed by
many studies on cardiac surgery patients (Habicher et al. 2011; Wiesenack et al.
2001; Reuter et al. 2002a, b). Moreover, in another study on cardiac surgery patients,
a lling pressure-guided management was compared to a management based on
ITBVI, CI, MAP, HR, and ScvO
2
use. The rst group showed a longer ICU and
hospital stay, with respect to the second group (Smetkin et al. 2009).
In the case of left ventricular failure or acute lung injury, the EVLW (extravascu-
lar lung water, index of lung edema) can be used. EVLW is an independent predictor
of survival (Agrò and Vennari 2013b). In GDT, the use of EVLW accelerates the
resolution of lung edema, whether due to increased vascular permeability or to an
increase in hydrostatic pressure (Agrò and Vennari 2013b).
In cardiac surgery patients, the use of a goal-directed protocol (GEDV > 800 mL/
m
2
, EVLW = 10–12 mL/kg) resulted in an enhanced postoperative outcome (Agrò
and Vennari 2013b; Goepfer et al. 2007).
Left ventricular end-diastolic area (LVEDA) is the most popular echocardio-
graphic parameter (measured with transesophageal probe) used to assess preload,
very easy to measure, and reliable with respect to other sophisticated parameters.
Literature evidenced LVEDA is a valid parameter to guide uid management in
cardiac surgery patients and to evaluate uid responsiveness (LVDA increase in
uid responder after the challenge) (Habicher et al. 2011; Cheung et al. 1994;
Tousignant et al. 2000). LVEDA correlates with SVV and ITBV (Buhre et al. 2001).
In patients who underwent cardiac surgery, LVEDA showed a better predictive
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capacity to uid responsiveness than lling pressure (Wiesenack et al. 2005). As a
consequence, its use is suitable in this kind of patients (Habicher et al. 2011).
Literature has showed that volumetric parameters are superior to conventional
lling pressures to assess cardiac preload and might prove helpful in guiding uid
therapy in cardiac surgical patients (Habicher et al. 2011).
13.15.2.3 Monitoring Systems in GDT
The use of GDT requires hemodynamic assessment and monitoring. The ideal system
should be simple, non- or hardly invasive, safe, and precise, allowing immediate ther-
apeutic intervention. Unfortunately, this system has not yet been invented. Many sys-
tems have been proposed for hemodynamic assessment, especially recently (Agrò and
Vennari
2013b). All these systems have to be compared to the Swan–Ganz or pulmo-
nary artery catheter (PAC), which remains the gold standard, despite its limits. In fact,
many clinical trials showed that PAC is not suitable for GDT in the routine periopera-
tive setting (Agrò and Vennari 2013b). Its use is further discouraged by the invasive-
ness of the procedure, which exposes patients to complications. In addition, PAC
cannot be used without adequate training and experience. Finally, its performance
mainly refers to lling pressure values (PVC, PCWP), which have been found to be
not so effective in clinical practice. Consequently, its fame in the literature and in clin-
ics has decreased over the years (Agrò and Vennari 2013b). Moreover, less invasive
systems with similar precision have been introduced. Modern technologies provide
lling volume values that are more reliable as preload and uid responsiveness indexes
(Agrò and Vennari 2013b; Lees et al. 2009). Current and less invasive ow monitoring
techniques include Doppler technologies or arterial pressure waveform analysis.
The esophageal Doppler (ED) allows measurement such as LVEDA and the
blood velocity at the level of the descending aorta. The ow time in the descending
aorta corrected for HR (FTc normally 330–360 ms) corresponds to the SV. According
to the chosen probe, the correspondence is obtained through a monogram calculated
from comparative studies performed with a PAC or through the measurement of the
vessel cross section. At lower velocities, hypovolemia should be suspected. FTc
correlates with LVEDA (Agrò and Vennari
2013b; DiCorte et al. 2000). ED requires
shorter operator training than other systems and does not require calibration, but it
is difcult to use in awake patients and in prolonged monitoring; nally, its results
may be operator dependent. GDT using ED was shown to improve patient outcomes
(Agrò and Vennari 2013b). Chytra et al. (2007) have shown that the optimization of
uid management using ED in trauma patients reduces blood lactate levels, the
incidence of infections, and the duration of ICU and hospital stay. A meta-analysis
showed that patients undergoing major abdominal surgery, who received
ED-oriented GDT, had a reduction in complications, requirement of inotropes, ICU
admissions, and hospital stay, with a rapid organ function recovery (Agrò and
Vennari 2013b; Abbas and Hill 2008).
New monitoring devices, assessing dynamic and volumetric parameters, are
PICCO system and PiCCO2 Pulsion Medical Systems, Munich, Germany; FloTrac,
Edwards Life Systems; and LiDCOrapid, LiDCO, London, UK.
These devices use transpulmonary thermodilution and/or pulse wave analysis.
When the methodologies are used in combination, the validity of pulse pressure
F.E. Agrò et al.
https://t.me/med1917
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