Download The Comparison of Hypertonic Saline (7.5%) and Normal Saline

The Comparison of Hypertonic Saline (7.5%) and Normal
Saline (0.9%) for Initial Fluid Administration Before
Spinal Anesthesia
Kati Järvelä, MD*, Seppo E. Honkonen,
Seppo Kaukinen, MD, PhD*
MD, PhD†,
Timo Järvelä,
MD†,
Tiit Kööbi,
MD, PhD‡,
and
Departments of *Anaesthesia and Intensive Care, †Orthopaedics, and ‡Clinical Physiology, Tampere University Hospital,
Tampere, Finland
Hypertonic saline can be used for initial fluid administration before spinal anesthesia. It is effective in smallvolume fluid resuscitation. This randomized doubleblinded study compared the effects of 7.5% hypertonic
saline (HS) and 0.9% normal saline (NS) in doses containing 2 mmol/kg of sodium in 40 ASA physical status
I–II patients undergoing arthroscopy or other lower
limb surgery under spinal anesthesia. We infused
1.6 mL/kg of HS or 13 mL/kg of NS for initial fluid
administration before spinal anesthesia induced with a
10-mg dose of 0.5% hyperbaric bupivacaine. Etilefrine
was administered to maintain mean arterial pressure at
ⱖ80% of its control value. Systolic and diastolic blood
S
pinal anesthesia produces sympathetic blockade; systemic vascular resistance decreases, and
the blood pressure may decrease (1). Initial fluid
administration with isotonic fluids is often used for
the prevention of hypotension, and it is usually well
tolerated by healthy young patients. However, excess
free water administration is not desirable in patients
with cardiovascular restrictions.
Infusion of hypertonic saline (HS) increases plasma
osmolality and causes fluid shift from the intracellular
to the extracellular space (2). This leads to intravascular and interstitial volume expansion, and thereby improves hemodynamics (3). HS is inexpensive and involves no risks of allergic reactions compared with
other artificial plasma expanders (4). In addition, there
is no risk of transmission of infectious substances, as
with human plasma (4). HS solutions of varying concentrations (1.8%–7.5%) have been investigated earlier
Supported, in part, by the Medical Research Fund of Tampere
University Hospital, Tampere, Finland.
Accepted for publication August 1, 2000.
Address correspondence and reprint requests to Kati Järvelä, MD,
Department of Anaesthesia and Intensive Care, Tampere University
Hospital, P.O. Box 2000, FIN-33521 Tampere, Finland.
©2000 by the International Anesthesia Research Society
0003-2999/00
pressure, heart rate, and cardiac index did not differ
between the groups, and the amount of etilefrine administered was similar in the treatment groups. In all
our patients, the plasma sodium concentrations were
within the normal range after surgery and serum osmolality was within the normal range after spinal anesthesia. The time and the volume of the first micturition
were similar in both groups, despite the much smaller
amount of infused free water in the HS group. We conclude that 7.5% HS was as good as NS for the initial fluid
administration before spinal anesthesia when the
amount of sodium was kept unchanged.
(Anesth Analg 2000;91:1461–5)
in hemorrhagic (5), cardiogenic (6), and refractory hypovolemic shock (7) and in postoperative use (8).
Initial fluid administration with 5% saline solution
before extradural anesthesia maintained adequate arterial pressure as effectively as isotonic saline or lactated Ringer’s solution when an equal amount of sodium (2 mmol/kg) was given (9). Spinal anesthesia
causes more rapid changes in hemodynamics than
does extradural anesthesia. The effect of hypertonic
saline is rapid and short-lasting (10). Therefore, it
could be even more suitable for the initial fluid administration before spinal anesthesia than before extradural anesthesia. Only a few studies have been
performed on the use of HS solution in this situation
(11,12). However, in these studies the investigators
have used 7 mL/kg of 3% saline and compared it with
the same volume of either normal saline or lactated
Ringer’s solution. Thus, the sodium load was markedly greater in the HS group. Initial fluid administration with 3% saline maintained cardiovascular stability as effectively as 0.9% saline containing the same
amount of sodium (2 mmol/kg) (13). Free water administration could be reduced even more by using
7.5% saline.
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Table 1. Demographic Data and Effects of
Spinal Anesthesia
Sex (F/M)
Age (yr)
Height (cm)
Weight (kg)
Sensory level of anesthesia
Duration of anesthesia (min)
HS
(n ⫽ 20)
NS
(n ⫽ 20)
7/13
44 (18–63)
174 (8)
81 (16)
T6 (T4–10)
154 (36)
3/17
42 (23–64)
177 (11)
79 (12)
T7 (T5–10)
156 (43)
Values are mean (sd or range).
HS ⫽ hypertonic saline group; NS ⫽ normal saline group.
In this randomized, double-blinded study, our purpose was to evaluate the effects of the initial fluid
administration before spinal anesthesia when using
either 7.5% hypertonic saline or normal saline containing the same amount of sodium (2 mmol/kg).
Methods
Forty ASA physical status I–II patients scheduled for
knee arthroscopy or other lower limb orthopedic surgery under spinal anesthesia gave their informed consent to participate in this randomized, double-blinded
study. The study was approved by the ethics committee of the hospital. The exclusion criteria included any
contraindications to spinal anesthesia.
If premedication was needed, 1 mL of fentanyl was
administered IV after the insertion of venous cannula.
A radial arterial catheter was inserted for blood samples and monitoring of real-time arterial pressure during the surgical procedure. Monitoring of circulation
was started in a separate room for baseline measurements before spinal anesthesia. CircMon B202 (JR
Medical Ltd, Tallinn, Estonia) was used for the measurement of whole-body impedance cardiographyderived cardiac output (CO) and heart rate (HR). Disposable electrocardiogram electrodes (Blue sensor
type R-00S; Medicotest A/S, Ølstykke, Denmark)
were used. A pair of electrically connected current
electrodes was placed on the distal parts of the extremities just proximal to the wrists and ankles. Voltage electrodes were placed 5 cm proximally from the
current electrodes (14). The patient’s limbs were isolated from the trunk to prevent an electrical connection during the bioimpedance measurements. Systolic
blood pressure (SBP) and diastolic blood pressure
(DBP) were measured noninvasively by using Accutorr 4 (Datascope Corp., Montvale, NJ).
Then, the patients were transferred to the operating
room; a 16-gauge cannula was inserted in a peripheral
vein in the cubital fossa. Through this cannula, the
patients received either 1.6 mL/kg of HS (NaCl 7.5%)
or 13 mL/kg of NS (NaCl 0.9%) according to randomization, for initial fluid administration over 10 –15 min.
Figure 1. Heart rate before (1) and after (2) preload, after spinal
puncture (3), after completion of the surgery (4), and after recovery
from spinal anesthesia (5) in the hypertonic saline (HS) and normal
saline (NS) groups. Values are expressed as mean ⫾ sem. The
groups did not differ at any time point.
All patients received the same amount of sodium
(2 mmol/kg) in this initial fluid administration, which
was given by the anesthesia nurse caring for the patient in the operating room. The investigators were
blinded to the infusion. After the initial fluid administration, 0.45% saline infusion was started as maintenance fluid at the rate of 2 mL 䡠 kg⫺1 䡠 h⫺1.
Spinal anesthesia was induced immediately after
the end of the study fluid infusion. It was performed
by using a 27-gauge Quinke-type spinal needle (Spinocan; B. Braun, Melsungen, Germany) at the L2-3 or
L3-4 intravertebral space with the patient in lateral
decubitus position with the operative side dependent.
All patients received 2.0 mL of 0.5% bupivacaine (hyperbaric). The patients were kept in lateral decubitus
position for 5 min and then repositioned in the supine
position. The surgical procedure was started when the
level of sensory block was satisfactory for the operation. During the surgical procedure, invasive arterial
pressure was monitored continuously by using a
Hewlett Packard monitor (Hewlett-Packard GmbH;
Böblingen, Germany). A 2-mg bolus of etilefrine was
administered IV during the course of spinal anesthesia
whenever the mean arterial pressure (MAP) stabilized
⬍80% of its baseline value. The baseline value of MAP
was measured before the initial fluid administration in
the operating room. The highest cutaneous level of the
sensory block was determined by cold sensation, and
the patients were asked about possible side effects.
Blood pressure, HR, and CO were measured, and
blood samples were taken from the radial arterial
cannula before the initial fluid administration, after
repositioning the patient in the supine position after
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Figure 3. Cardiac index (CI before (1) and after (2) preload, after
spinal puncture (3), after completion of the surgery (4), and after
recovery from spinal anesthesia (5) in the hypertonic saline (HS) and
normal saline (NS) groups. Values are expressed as mean ⫾ sem.
Figure 2. Systolic blood pressure (SBP) and diastolic blood pressure (DBP before (1) and after (2) preload, after spinal puncture (3),
after completion of the surgery (4), and after recovery from spinal
anesthesia (5) in the hypertonic saline (HS) and normal saline (NS)
groups. Values are expressed as mean ⫾ sem.
the spinal puncture, after the surgical procedure, and
after recovery from the spinal anesthesia (plantar and
dorsiflexion of both ankles recovered). Plasma concentrations of sodium, potassium, and chloride and serum osmolality were measured. The time of voiding
after spinal anesthesia (min after the induction of spinal anesthesia) and the volume of urine were
recorded.
Before the trial, a power calculation for a 15 mm Hg
difference in SBP with a probability level of 0.05 and
power of 0.80 (1-␤) yielded a sample size of 15–16
patients. Accordingly, 20 patients were enrolled in
both groups.
Statistical analysis was performed by using the SPSS
for Windows (version 9.0) (SPSS Inc., Chicago, IL). The
results were analyzed by using an analysis of variance
for repeated measures with group as the factor, and
time as the repeating factor (before the initial fluid
administration, after repositioning the patient in the
supine position after the spinal puncture, after the
surgical procedure, and after recovery from the spinal
anesthesia). Student’s t-test for independent samples
was performed at different time points. Dichotomous
variables were tested by using the ␹2 test. Results are
expressed as mean ⫾ sd; P ⬍ 0.05 was considered
statistically significant.
between the treatment groups (Table 1). The volume
of initial fluid administration was 129 ⫾ 25 mL in the
HS group and 1031 ⫾ 161 mL in the NS group. No
notable intraoperative blood loss occurred in either of
the study groups.
The groups were similar for the total amount of
etilefrine administered (HS: 1.0 ⫾ 2.4 vs NS: 1.0 ⫾
2.1 mg; not significant). Five patients (25%) in both
groups needed etilefrine administration. Baseline values of HR, SBP, DBP, and cardiac index (CI) did not
differ between the two groups. No significant differences were observed between the groups in the HR
(Fig. 1), SBP and DBP (Fig. 2), or CI (Fig. 3) values
during the study.
The plasma sodium and chloride levels as well as
the serum osmolality increased after the initial fluid
administration. The highest plasma sodium value after the initial fluid administration was 150 mmol/L.
All values were within normal range after the surgery.
The plasma sodium, chloride, and potassium values,
and the serum osmolality are presented in Table 2.
There were no significant differences in the time of
voiding after spinal anesthesia (HS 319 ⫾ 68 min; NS
290 ⫾ 71 min) or in the volume of urine (HS 449 ⫾
282 mL; NS 433 ⫾ 270 mL). Adverse effects, including
sensation of heat and compression around the arm
during the study fluid infusion and sensation of thirst,
were more common in the HS group (75% of patients)
than in the NS group (no adverse effects; P ⬍ 0.001).
Discussion
Results
The two groups were comparable for patient characteristics and the number of blocked segments (Table 1). The duration of spinal anesthesia did not differ
We found that 1.6 mL/kg of 7.5% HS was as effective as
13 mL/kg of 0.9% NS in the prophylaxis of hemodynamic changes in ASA physical status I–II patients undergoing knee arthroscopy or other lower limb orthopedic surgery. When the same amount of sodium was
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Table 2. Plasma Sodium (Na), Potassium (K) and Chloride (Cl), and Serum Osmolality
Plasma Na (mmol/L)
Plasma K (mmol/L)
Plasma Cl (mmol/L)
Serum osmolality (mosm/kg)
Group
Baseline
After preload
After surgery
After recovery
from spinal
anesthesia
HS
NS
HS
NS
HS
NS
HS
NS
140 ⫾ 1
140 ⫾ 1
3.9 ⫾ 0.2
3.9 ⫾ 0.2
107 ⫾ 2
107 ⫾ 2
291 ⫾ 4
292 ⫾ 3
145 ⫾ 2*
140 ⫾ 1
3.8 ⫾ 0.2
3.9 ⫾ 0.3
114 ⫾ 3*
110 ⫾ 2
302 ⫾ 5*
292 ⫾ 3
142 ⫾ 2*
140 ⫾ 2
4.0 ⫾ 0.3
3.9 ⫾ 0.2
111 ⫾ 3†
109 ⫾ 3
297 ⫾ 4*
290 ⫾ 3
141 ⫾ 1*
139 ⫾ 1
4.0 ⫾ 0.2
3.9 ⫾ 0.2
111 ⫾ 2
109 ⫾ 3
295 ⫾ 3*
290 ⫾ 3
HS ⫽ hypertonic saline, NS ⫽ normal saline.
* P ⬍ 0.001; † P ⫽ 0.012 as compared to the NS group, t-test for independent samples.
infused during the initial fluid administration, the patients required similar amounts of etilefrine to maintain
adequate arterial pressure during spinal anesthesia. Both
study fluids were able to keep MAP greater than the
acceptable limit in 75% of patients. This is in line with the
results of Veroli and Benhamou’s group (9). They used
5% saline for the initial fluid administration before extradural anesthesia.
The ideal treatment for hypotension related to spinal anesthesia is controversial, as the etiology is still
uncertain. Some investigations suggest that hypotension is primarily the result of a reduction in cardiac
filling or the initial fluid administration and systemic
vascular resistance (15). Initial fluid administration
might provide a protection against undesired cardiovascular side effects (16), but not all studies have
shown this (17). The augmentation of blood volume
with initial fluid administration, regardless of the fluid
used, must be large enough to result in a significant
increase in CO for effective prevention of hypotension
(18). However, excess free water administration is to
be avoided in patients with cardiovascular restrictions. Fluid administration reduces the incidence of
early events, but a vasopressor is needed for prevention of the late events (19). We used etilefrine, which is
as effective as ephedrine in restoring SBP (20).
The level of sensory nervous block did not differ
between the treatment groups. Hyperbaric bupivacaine 0.5% in a dose of 10 mg was chosen for spinal
anesthesia because it provides tolerance to pneumatic
tourniquet for 70 min (21), which is usually enough for
arthroscopic anterior cruciate ligament-reconstruction
and other orthopedic lower limb surgery. This dose
may, however, delay the ability to void in some patients (22). In our study, the time of the first micturition in both groups was comparable to previous results (22), despite the much smaller amount of infused
free water in the HS group. In addition to the ability to
maintain adequate MAP, HS solution improves kidney function by reducing renal vascular resistance
(23). This may even counteract the adverse effects of
etilefrine on renal vasculature, when vasoconstriction
is required.
HS administration causes a rapid increase in serum
sodium concentration and osmolality related to the
sodium dose. This has been associated with central
pontine myelinolysis in chronically debilitated patients with a prolonged period of hyperosmolality or
hypernatremia (24). However, 7.5% HS is safe in
small-volume resuscitation, and the usual dose is
4 mL/kg (25). In our study, the highest plasma sodium value after the initial fluid administration was
150 mmol/L. The plasma sodium concentration of all
patients was within the normal range after surgery,
and the serum osmolality level was within the normal
range after spinal anesthesia. Hypokalemia may develop after rapid expansion of the plasma volume
with HS containing no potassium. This may cause
arrhythmia. Hypokalemia was not seen in our patients, however. In the HS group, the patients experienced the sensation of heat and compression around
the arm during the HS infusion. These symptoms
were well tolerated and disappeared immediately after the completion of the HS infusion. Heat and pain
are probably caused mainly by the high osmolality of
the HS solution and cannot be eliminated totally (26).
The patients of the HS group also felt thirsty until they
were allowed to drink.
Whole-body impedance cardiography (ICGWB) is a
reliable method compared with other methods of measuring CO. Comparison with thermodilution (TD) and
direct Fick methods showed that ICGWB measures CO
accurately in different conditions (in the supine position, during head-up tilt, after the induction of anesthesia and after coronary artery bypass surgery)
(14,27,28). The differences in CO values between
ICGWB and TD were comparable with those attained
between direct Fick and TD, and the repeatability of
ICGWB was nearly twice as good as in TD (27,28).
Therefore, ICGWB is an adequate method to estimate
CO and its changes. In our patients, CI remained at the
same level in the HS group as in the NS group. HR did
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HYPERTONIC SALINE BEFORE SPINAL ANESTHESIA
not differ between the groups. HS solution increases
myocardial contractility (29). This effect of HS probably explains the improved CO after HS infusion. Because osmolality is the driving force for volume distribution, HS causes fluid shift from the intracellular
space into the intravascular and interstitial spaces (30).
Therefore, it increases the plasma volume more than
by its own volume. The increase of myocardial contractility and plasma volume together lead to increased CO and thus help stabilize the hemodynamics
during spinal anesthesia.
We conclude that 7.5% HS was as good as NS for the
initial fluid administration before spinal anesthesia
when the amount of sodium was kept unchanged. It
was effective in small doses of 1.6 mL/kg. Also, the
potential disadvantages of HS solution, including hypernatremia, hyperosmolality, and hypokalemia,
could be avoided. HS can be recommended for the
initial fluid administration in situations in which excess free water administration is not desired. We have
studied ASA physical status I–II patients, but initial
fluid administration with HS may also be beneficial in
other patient groups, such as elderly patients with
cardiovascular restrictions.
We thank Pirjo Järventausta, RN, and Satu Ruusuvuori, RN, for
their valuable technical assistance.
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