Fluid Management:
Questions and Answers 20
Maria Benedetto, Chiara Candela and Felice Eugenio Agrò
20.1 How Is Water Distributed in Body Compartments?
Body water accounts for approximately 60% of body weight; it is mainly distrib-
uted in the extracellular and intracellular spaces (ECS and ICS, respectively).
The ICS contains nearly 55% of the water, and the ECS 45% (about 15 L in a
normal adult). The ECS is further divided into the intravascular space (IVS), the
interstitial space (ISS), and the transcellular space (TCS), containing about 15%,
45%, and 40% of ECS water, respectively. The TCS is a functional compartment
represented by the amount of fluid and electrolytes continually exchanged (in
and out) by cells with the ISS and by the IVS with the ISS.
20.2 What Is the Physiological Role of Electrolytes
Contained in the Plasma?
Sodium is the main cation in the ECS and the main determinant of ECS vol-
ume. It has an important hemodynamic role as it is involved in the renin-
angiotensin system. It is necessary for the regulation of blood and body flu-
ids, for the transmission of nerve impulses, and for cardiac activity.
Potassium is the major cation in the ICS. It is important in allowing car-
diac muscle contraction and conduction and participates in sending nerve
impulses. It also plays a key role in kidney function.
Calcium is involved in exocrine, endocrine, and neuro-endocrine secretions,
the coagulation system, muscle contraction, cell growth, and enzymatic regulation.
C. Candela ()
Postgraduate School of Anesthesia and Intensive Care, Anesthesia, Intensive Care and Pain
Management Department, University School of Medicine Campus Bio-Medico of Rome,
Rome, Italy
e-mail:
F. E. Agrò (ed.), Body Fluid Management, 255
DOI: 10.1007/978-88-470-2661-2_20 © Springer-Verlag Italia 2013
Questions and Answers 20
Maria Benedetto, Chiara Candela and Felice Eugenio Agrò
20.1 How Is Water Distributed in Body Compartments?
Body water accounts for approximately 60% of body weight; it is mainly distrib-
uted in the extracellular and intracellular spaces (ECS and ICS, respectively).
The ICS contains nearly 55% of the water, and the ECS 45% (about 15 L in a
normal adult). The ECS is further divided into the intravascular space (IVS), the
interstitial space (ISS), and the transcellular space (TCS), containing about 15%,
45%, and 40% of ECS water, respectively. The TCS is a functional compartment
represented by the amount of fluid and electrolytes continually exchanged (in
and out) by cells with the ISS and by the IVS with the ISS.
20.2 What Is the Physiological Role of Electrolytes
Contained in the Plasma?
Sodium is the main cation in the ECS and the main determinant of ECS vol-
ume. It has an important hemodynamic role as it is involved in the renin-
angiotensin system. It is necessary for the regulation of blood and body flu-
ids, for the transmission of nerve impulses, and for cardiac activity.
Potassium is the major cation in the ICS. It is important in allowing car-
diac muscle contraction and conduction and participates in sending nerve
impulses. It also plays a key role in kidney function.
Calcium is involved in exocrine, endocrine, and neuro-endocrine secretions,
the coagulation system, muscle contraction, cell growth, and enzymatic regulation.
C. Candela ()
Postgraduate School of Anesthesia and Intensive Care, Anesthesia, Intensive Care and Pain
Management Department, University School of Medicine Campus Bio-Medico of Rome,
Rome, Italy
e-mail:
F. E. Agrò (ed.), Body Fluid Management, 255
DOI: 10.1007/978-88-470-2661-2_20 © Springer-Verlag Italia 2013
