J. Vet. Med. A 39, 204-214 (1992) 0 1992 Paul Parey Scientific Publishers, Berlin and Hamburg ISSN 0931-184X

From the Large Animal Surgical Clinic, State University of Gent, Belgium Director: Prof Dr. A . De Moor

Influence of Hypertonic Saline Solution 7.2 % on Different Hematological Parameters in Awake and Anaesthetized Ponies F. GASTHUYS,C. MESSEMAN a n d A. DE MOOR Address of authors: F. GASTHUYS, Large Animal Surgical Clinic, Faculty of Veterinary Medicine, State University of Gent, Casinoplein 24, B-9000 Gent, Belgium

With 4 figures and 2 tables (Received for publication September 23, 1991)

Summary The influence of hypertonic NaCl 7.2% infusion (4ml/kg of body weight [ B W ) on plasma (PV) and blood (BV) volumes, sodium (Na), chloride (Cl), potassium (K) plasma concentrations, osmolality (Osm), total protein content (TP), packed cell volume (PCV) and red blood cell count (RBC) was studied in five standing and anaesthetized ponies (standard halothane anaesthesia). Arterial blood gases were followed in the anaesthetized ponies. Isotonic NaCl 0.9 % (4 ml/kg of BWT) was used as a placebo in the standing ponies. Isotonic solution in the standing ponies induced few changes: only small decreases in K, TP, PCV and RBC were observed. Na, CI and Osm increased significantly after the NaCl 7.2 % infusions in the standing and anaesthetized ponies. Significant decreases in PCV, RBC and T P after the administration of hypertonic solutions were determined and were in both groups clear indications of an occurring hemodilution although no significant increase in PV and BV could be demonstrated. An increase in diuresis characterized by numerous micturations was observed in the standing ponies and during the recovery period after anaesthesia. Apparently, the occurring fluid shift towards the intravascular compartment was partly compensated by an increase in diuresis. The decreases in PCV, RBC and TP were less severe in the anaesthetized ponies compared to the changes observed in the standing ponies. Stress responses during anaesthesia might explain this finding. K increased abnormally at the end of anaesthesia, probably due to minimal muscle damage induced by the dorsal recumbent position. Arterial blood gases did not change after the administration of NaCl 7.2 % solution during anaesthesia. N o specific clinical side-effects related to the use of hypertonic solution could be observed in the standing and anaesthetized ponies. Further studies are necessary to investigate the effects of hypertonic NaCl solution in horses with a disturbed fluid balance (hypovolemia).

Introduction Hypertonic saline solutions were used for the first time during World W a r I as reanimation of hemorrhagic shock in m a n (PENFIELD et al., 1919). In the late sixties the beneficial effects of small-volume resuscitation were further proven (BAUEet al., 1967). T h e interest in hypertonic and hyperoncotic solutions (such as 10 % dextran 60 or 70 in 7.2 % saline solution) for t h e reanimation of hemorrhagic shock was renewed by a n u m b e r of investigations in m a n (DE FELIPPEet al., 1980; HOLCROFT et al., 1987) and animals US. Copyright Clearance Center Code Statement:

0931 - 184X/92/3903 - 0204$02.50/0

Influence of Hypertonic Saline Solution 7.2 % on Different Hematological Parameters

205

(DAUTERMAN et al., 1990; KRAMER et al., 1986; KREIMEYER et al., 1990; MANINCAS et d., 1986; MATHRUet al., 1990; MERMEL et al., 1986; MUIRet d.,1989; NAKAYAMA et al., 1984, 1985; PROUGHet al., 1986; RAMAMOORTHY, 1990; ROCHAE SILVAet al., 1987; SCHMALL et al., 1990a, b; SMITHet al., 1985; TRAVERSO et al., 1987; VELASCO et al., 1980; WASH et al., 1991). Other important applications of small volume hypertonic solutions such as burn shock (MONAFOet al., 1973; MOYLANet al., 1973), endotoxemic shock (BERTONEet al., 1990; LUYPAERT et al., 1986; PROUGHet al., 1985), experimental induced gastric dilatationvolvulus shock (ALLENet al., 1991) or anaesthetic induced hypotension (DYSON et al., 1990) were also demonstrated. Until now the effects of hypertonic solutions were investigated in horses with experimental anaesthetic induced hypotension, hemorrhagic or endotoxemic shock. No information is available about the practical use of these solutions in normal and sick horses. An important cardiovascular depression due to hypovolemic shock is present in a number of horses before surgery. The practical correction of this situation is the administration of large quantities of an isotonic solution before or during anaesthesia which is not always possible due to emergency reasons. Small quantities of hypertonic solutions before surgery might therefore be indicated to achieve a fast normalization of this imbalance. This study was done to obtain more information about the hematological and side-effects of hypertonic saline in awake and anaesthetized ponies. Material and Methods Five healthy ponies (castrated males, mean BWT 320.2 f 21.6 kg, mean age 3.5 f 0.5 years) with a transposed carotid artery were used. The ponies were fasted overnight but had free access to water before each experiment. The different experiments in each animal were performed with at least 1 week interval.

Analytical methods After centrifugation of the venous blood samples, the sodium (Na), potassium (K) and chloride (Cl) concentrations (mmoV1) in the serum were determined using the flame photometry technique’. Osmolality of the plasma (Osm in mosmol) was determined by a semi-micro osmometerz. Total protein content of the plasma (TP in g/l) was measured with a densimeter’. Red blood cell count ~ ~ ) determined by a specific countelA. (in x 1 0 6 / n - ~ was The plasma volume (PV in mVkg) was determined using “Evans Blue” dye dilution technique as described by PERSSON (1%7). The blood volume (BV in mVkg) was calculated using the PV and packed cell volume (PCV in V1)5 by the following formula: BV

=

PV x 100 PCV

100

-

Blood gases (partial arterial oxygen and carbon dioxide tensions or P.02 and C 0 2 in mm Hg) and standard bicarbonate concentration (SBC in mEq/l) were analyzed immediatelp.

Standing non-sedated ponies The ponies were placed in stocks during the first experiment. 12G trocard catheters were placed into the left and right jugular veins; venous blood samples (heparin, silicone coated and EDTA vacuum containers) were taken from the left jugular vein while the different solutions (or injections) were injected into the right vein. After the collection of the control blood samples and the determination of the control PV and BV, NaCl 0.9% (4mVkg of BWT) was infused. The different hematological parameters were 1

2 3 4 5

6

Flame Photometer 430, Corning, UK. Halbmikro-osmometer, Knauber tiCo, Germany. Serum protein meter, Bausch and Lumb Optical Co., USA. Coulter counter ZF, Coulter Electronics LTD, UK. Micro-haematocrit centrifuge, Hawksley, UK. Gas check 939, AVL, Schaffhausen, Switzerland.

206

GASTHUYS, MESSEMAN and DE MOOR

determined 5,15,30,45, and 60 after the administration of the NaC10.9 %n infusion. PV was measured 15 minutes after the infusion of NaCl 0.9 % in the standing ponies. NaCl 7 . 2 % (4 ml/kg of BWT) was given afterwards. The different hematological parameters were determined 5, 15, 30, 45, 60, and 120 minutes after the infusion; PV was measured 15 and 120 minutes after the administration of NaCl 7.2 % in the standing ponies. Anaesthetized ponies Control blood samples were taken in the non-sedated standing ponies. Xylazine’ (1.1 mg/kg of BWT iv) was given as premedication; anaesthesia was induced by ketaminex (2.2 mg/kg of BWT iv). After orotracheal intubation, the ponies were connected to a large animal anaesthetic device9 and were placed in dorsal recumbency. Intermittent positive pressure ventilationlo was used as soon as possible (tidal volume f 11/100 kg of BWT, end-inspiratory pressure between 20 and 25 cm HZO). The respiratory rate and the tidal volume were adjusted to maintain normocapnea which was controlled by arterial P,COz determination. Oxygen (average total oxygen flow of f 2 I/min in a semiclosed system) was the carrier gas for halothane”. Anaesthesia was kept constant by observing the different monitoring device^'*^^^ (end-expiratory P&OZ between 4 and 5 vol. YO)and the eye lid reflexes (slightly positive). Arterial blood samples were collected in heparinized disposable 2 ml syringes by an 18G trocard catheter positioned into the subcutane carotid artery. The jugular veins were prepared as described above. After a stabilization period of 60 minutes, the anaesthetic control samples (hematology and PV) were collected. NaCl 7.2 % 4 (ml/kg of BWT) was infused afterwards. The different parameters (Na, K, C1, Osm, TP, RBC) including the blood gases (P,Oz, P,CO2 and SBC) were determined at 5, 15, 30,45, 60, and 90 minutes after the administration of the hypertonic solution and at 30 minutes after the disconnection of the anaesthetic circuit machine (recovery). Anesthesia, which lasted for 160 minutes, and recovery were uneventful. Statistical analysis A multiple F - and range test (Ducan-Reed) was used to determine the significant difference between the different data. A p-value of 5 0.05 was considered significant.

Results Standing ponies (Table I , Figures 1 to 4 ) The infusion time of different solutions was always less than 10 minutes (average 8.5 minutes) Nu and Cl concentrations remained constant after the isotonic fluid administration. Hypertonic N a C l induced a significant increase in N a and C1 concentrations which gradually decreased afterwards. The potassium concentration decreased significantly 45 and 60 minutes after the isotonic fluid administration. A further non-significant decrease occurred after the hypertonic fluid administration. Osm did not change after N a C l 0.9 % administration but increased significantly for 120 minutes after the hypertonic fluid administration. Non-significant decreases in PCV and T P were observed after the N a C l 0.9 % infusion. P C V and TP decreased significantly respectively 15 and 45 minutes after N a C l 7.2 % administration. RBC decreased significantly after the isotonic fluid administration; a further decrease in RBC occurred after the hypertonic solution administration. PV and BV did not change significantly at 15 and 120 minutes after infusion. Only 1 pony urinated after the isotonic fluid administration; all animals had at least one micturation after the hypertonic fluid administration (minimally after 28 minutes). No specific sideeffects were noticed during and after the infusion of the isotonic and hypertonic solutions. 7

8 9 10 11

12

13

Rompun 2 %, Bayer, Belgium. ImalgPne 1000, Institut MPrieux, Belgium. North American Drager Co, USA. Smith large animal respirator, Denmark. Fluothane, ICI, Belgium. Capnograph Mark 111, Gould Godart, Nederland. Multicap, Datex, Belgium.

Influence of Hypertonic Saline Solution 7.2 YO on Different Hematological Parameters

207

Table 1. Influence of isotonic (0.9 YO) and hypertonic NaCl (7.2 YO) infusions (4 ml/kg of BWT) on different hematological parameters in 5 standing ponies ~~

mmol/l

C1 mmol/l

mmoVl

Osm mosmol

137.3 t 1.7

101.0 t 0.9

4.30 f0.08

275.5 k 3.1

137.3 f 1.3 139.3 f 3.6 137.8 f 1.5 137.8 f 1.7 138.5 f 1.7

101.0 k 1.4 100.0 f 1.8 101.5 f 1.0 101.5 f 1.0 101.0 f 0.8

4.01 f 0.22 4.08 f 0.33 4.08 f 0.24 3.93 f 0.22" 3.90 f 0.29"

276.0 f 6.2 274.5 f 6.2 275.0 f 2.6 277.5 f 2.1 279.8 f 1.8

5' 15' 30' 45' 60' 120'

146.5 f 1.3"""" 146.0 f 0.8"""" 145.0 f 1.4"""" 145.8 f 1.7"""" 145.5 f 1.7"""' 145.0 k 1.8""''

113.3 f 0.5"'"" 112.8 f 1.5*"0° 111.Of 1.8""00 110.8 f 1.7"*0° 108.5 f 1.3*""" 107.0 f 1.4"""'

3.70 f 0.25"" 3.78f 0.15"" 3.78k0.21"" 3.75 k 0.25"" 3.70 f 0.29"" 3.65 f 0.25""

290.0 f 2.2""" 293.0 k 2.9'*"" 293.3 f 3.8'""" 292.8 f 2.8'"'" 289.3 f 4.9""' 285.8 k 4.7"

PCV V1

TP

RBC x E6/mm3

PV

g/l

mVkg

BV ml/kg

36.1 f 7.3

65.5 f 4.0

5.80 f 0.36

53.6 f 2.9

84.3 2 7.3

29.5 f4.5 30.0 t 5.4 30.4 f 5.2 30.4 f 3.9 30.9 f 4.1 25.6 f 3.3" 24.3 f 3.8""" 25.1 f4.1" 24.8 k 2.2* 27.3 k 2.5 26.3 f 1.5"

60.0 k 3.2 61.0 f2.6 61.5 f3.1 61.5 f 3.1 61.0 f 2.9 52.8 f2.9"" 53.3 f 3.44 54.5 k 4.1" 55.8 f 4.9 56.8 f 5.4 58.8 f 5.4

4.99 k 0.20"" 4.n ko m * 4.67 k 0.37"" 4.78 f 0.43"" 4.87 f 0.36"" 4.40 k 0.41*+ 4.18 f0.51**" 4.27 f 0.68"" 4.08 f 0.82"" 4.56 f 0.79"" 4.28 ? 0.77""

51.6 t 3.3

76.2

54.5 f 2.4

74.1 2 4.9

54.0 f 4.1

74.3

TIME CONTROL NaCl 0.9 YO 5' 15' 30' 45' 60'

Na

K

NaCl 7.2 YO

* 6.6

* 6.3

Mean f standard deviation. *, *": significant difference p < 0.01 and 0.05 compared to Control; significant difference p < 0.01 and 0.05 compared to NaCl 0.9 % 60'. Abbreviations see text.

O,

O":

Anaesthetized ponies (Table 2, Figures 1 to 4 ) N o specific changes were observed during the control period in the anaesthetized ponies. The infusion time of different solutions was always less than 10 minutes (average 9.2 minutes). Hypertonic NaCl induced a significant increase in Na and Cl concentrations which gradually decreased afterwards. K concentration decreased only for 15 minutes after the hypertonic fluid administration; a gradud increase occurred afterwards which became significantly different in the recovery period. Osm increased significantly after the NaCl 7.2 OO/ administration; a gradual decrease occurred afterwards. PCV decreased significantly just after the hypertonic fluid administration while RBC showed a slight non-significant decrease. TP decreased also for 90 minutes. PV and BV did not change at 15 and 90 minutes after NaCl 7.2 YO infusion. Except for a small but significant decrease in standard bicarbonate concentration

208

GASTHUYS, MESSEMAN and DE MOOR

Table2. Influence of isotonic (0.9%) and hypertonic NaCl (7.2 %) infusions (4ml/kg of BWT) on different hematological parameters in 5 ponies during a standard halothane anaesthesia (dorsal recumbency, I. P. P. V.). TIME

Na mmol/l

CONTROL NaCl 7.5 %

134.5 f 1.3

0' 5' 15' 30' 60' 90'

158.0 f 6.1':" 151.5 f 1.3"" 146.7 k 1.7" 145.8f 1.7"'" 144.3 f 1.5"" 143.8 k 0.9"" 142.3 f 0.5""

Recovery

K

c1 mmol/l

mmol/l 3.9

95.8 f 2.9 126.3 f 5.1"" 118.8f3.2"" 113.5 S 3.1"" 110.3 f2.9"" 108.5 f4.4"" 106.8 f 4.0"" 104.5 f 5.8''"

* 0.2

3.6 f 0.2'' 3.6 k 0.3': 3.5 f0.3': 3.6 f 0.4 3.9 f 0.4 4.0 f 0.5 4.3 k 0.1':-

Osm mosmol

PCV 1/1

267.3 f 7.6

30.1 k 3.2

310.8 f 7.3"" 297.3 k 6.2*%289.3 k 6.7":' 285.3 f 7.1" 283.5 k 6.5" 282.8 f 6.3" 281.0 zk 8.0"

25.9 f 1.6" 26.8 k 2.4 27.6 _t 2.1 27.5 f 1.9 29.3 f 0.5 30.1 f 2.0 30.8 f 2.3

TP g/l

RBC x E6/mm3

PV ml/kg

BV ml/kg

PaOz mmHg

61.0 f 2.6"

5.03 f 1.32

53.7 f 8.2

77.2 k 10.9

167 k 86.7 46.4 k 3.3

25.0 f 2.2

49.0 k 2.9"" 48.5 k 2.4"" 50.3 f2.6"" 51.3 f2.6"" 52.0 iz 2.3"" 52.8 k 1.5"" 54.8 f 3.3"

4.35 f 1.37 4.68 f 1.89 4.49 f 1.54 4.51 f 1.40 4.67 k 1.18 4.74 f 1.02 4.88 f 1.72

58.3 f 8.9

80.3 f 11.0

166.0 f91.5 177.8 f 77.2 203.9 k 93.3 131.6 f 73.2 142.0 f 98.5

55.0 f 12.8

76.9 f 17.4

22.5 f2.9 21.8 f2.3 22.5 f 2.6 21.4 f 0.8" 21.2 f 1.3" -

PaC02 mmHg

-

46.2 k 5.2 44.8 f 3.7 48.3 f 6.0 48.6 f 6.6 49.7 f 8.5 -

SBC mEq/l

-

Mean f standard deviation. +,+*: significant difference p < 0.01 and 0.05 compared to Control. Abbreviations see text.

mmol/l I 432

-1

NaCl 7.2 %

470

398

h ,. :.:.... ...... ............ ..-...:..... :.:,= .?.., 30...... ......

396

:....... :..:..:..:..> .:

374 before

5

15

60

120/rec

Time Fig. 1. Influence of 4 ml/kgof BWTNaC17.2 YOon theplasmapotassiumconcentration (mean plus standard error) in five standing (K standing) and anaesthetized (K anaesthesia) ponies (data from tables 1 & 2). Before: Control value just before the infusion of NaCl 7.2 % solution. >, Ili, 30, 60, 12O/rec: Values respectively 5, 15, 30, 60 and 120 minutes or during recovery (in anaesthetized ponies) after termination of the infusion of NaCl 7.2 % solution

Influence of Hypertonic Saline Solution 7.2 % on Different Hematological Parameters

209

3 NAC17.2 %

300

310

r T

control

15

5

60

30

120/rec

Time Fig. 2. Influence of 4 ml/kg f BWT NaC17.2 Yoon the plasma osmolality (mean k standard deviation) in five standing (Osm stanc ig) and anaesthetized (Osm anaesthesia) ponies (data from tables 1 &2). Before: Control value just before the infusion of NaCl 7.2 Yo solution. 5, 15, 30, 60, 12ohec: Values respectively 5, 15, 30, 60 and 120 minutes or during recovery

(in anaesthetized ponies) after termination of the infusion of NaCl 7.2 YO solution

60 minutes after the hypertonic fluid administration, no significant changes in the arterial blood gases were noticed after infusion. All ponies urinated in the recovery period. No specific side-effects were observed during and after anaesthesia.

dl 70

65 60

0 TPstanding El TP anaesthesia

55 50 45

before

5

15

30

60

12Olrec

Time Fig. 3. Influence of 4rnllkg of BWT NaC17.2 % on the plasma total protein content (mean -t standard deviation) in five standing (TI' standing) and anaesthetized (TI' anaesthesia) ponies (data from tables 1 &2). Before: Control value just before the infusion of NaCl 7.2 % solution. 5, 15, 30, 60, 120/rec: Values respectively 5, 15, 30, 60 and 120 minutes or during recovery (in anaesthetized ponies) after termination of the infusion of NaCl 7.2 YO solution

210

GASTHUYS, MESSEMAN and DE MOOR

I

34

1T

NaC17.2 %

T

32

T

30

0 PCV standing 0 PCV anaesthesia

28

!Li

...... ......... :.:.: .. ....... i.:.:.:.:. ......... ........ ..:...:...:...:...:... ........... ...... ..... :.:.:.x.: .:.:.:._ .:.:.

26

.% ..>.

24 before

5

15

30

60

120/rec

Time Fig.4. Influence of 4ml/kg of BWT NaCl 7.2% on the packed cell volume (meankstandard deviation) in five standing (PCV standing) and anaesthetized (PCV anaesthesia) ponies (data from tables 1 &2). Before: Control value just before the infusion of NaCl 7.2 Yo solution. li, 15, 30, 60, f20/rec: Values respectively 5, 15, 30, 60 and 120 minutes or during recovery (in anaesthetized ponies) after termination of the infusion of NaCl 7.2 % solution

Discussion Compared to the classic administration of isotonic saline solutions, small volumes of hypertonic saline solutions (4 ml/kg of BWT of a 2,400 mosmol/l solution) have been successfully used in experimentally induced hemorrhagic shock in awake and anaesthetized animals (MANINGAS et al., 1986; SCHMALL et al., 1990a; VELASCO et al., 1980; MERMEL et et al., 1985). It was also proven that the sodium ion is superior in this al., 1986; NAKAYAMA resuscitation compared to other solutions with a similar osmolality. Especially the sodium ion is of importance to maintain the positive effects while the chloride ion has only a secondary role (SMITHet al., 1985; ROCHAE SILVAet al., 1987). Small volume resuscitation with hyperoncotic-hypertonic solutions such as 10 YO Dextran 60 or 70 in 7.2 % NaCl induced in the hemorrhagic shock model better results and was associated with longer duration of positive effects. These hyperoncotic-hypertonic solutions were therefore estimated as the “ideal” solution (KREIMEIER et al., 1990; SMITHet al., 1985). These commercial solutions are rather expensive for repetitive use in large animals. In this study the 7.2 % NaCl (2,40OOmosm/l) was chosen because of the low costs, the possibility of self-production even under clinical circumstances, and the non-viscosity of the solution (rapid administration). Our interest in hypertonic solutions is focused mainly on horses with acute hypovolemic shock due to gastrointestinal disturbances or with acute life-threatening anaesthetic problems. BERTONEet al. (1990) used non-anaesthetized ponies in which a sublethal endotoxemia (E. cofi) was induced. The endotoxemia was successfully counteracted by the use of hypertonic saline solution; the ionic changes were minimal and no specific side-effects were observed. DYSONet al. (1990) demonstrated the beneficial cardiovascular effects of hypertonic saline infusions administered before anaesthesia in healthy anaesthetized horses. Several side-effects were associated with the use of hyper1989; KLEEMAN, 1979; tonic saline solutions, such as neurological disturbances (HARDY, SMITHet al., 1985), release of histamine (RENCKet al., 1983; STIFFet al., 1979), hypophosphatemia (KRAMER et al., 1986), and hemolysis (ROCHAE SILVAet al., 1990). Although

Influence of Hypertonic Saline Solution 7.2 % on Different Hematological Parameters

21 1

numerous investigations have been made in the study of the ionic changes induced by hypertonic infusions in different animals, little information is available on the effects of hypertonic NaC17.2 % on the different hematological parameters and the potential clinical side-effects in horses. In this study, the changes of ions and osmolality were determined in awake and anaesthetized ponies treated with hypertonic saline infusions. Small quantities of isotonic saline infusions induced few changes (decrease in RBC and K) in the standing ponies. Since the ponies became quieter after handling, before the infusion of the different solutions, the observed small decrease in PCV after the isotonic saline solution administration was probably induced by splenic uptake of red blood cells (due to a decrease in activity of the sympathetic nerve system) and/or intravascular uptake of fluid (fluid shift). The potassium concentration decreased significantly 45 minutes after the end of the infusion but remained within the physiological limits; the reasons for this finding were not clear. Hypertonic saline infusions induced clear increases in sodium and chloride plasma concentrations and osmolality in the standing ponies. The gradual decrease of both ions afterwards might be due to the osmotic induced dilution effect and/or increased urinary excretion of both ions. A clear dilution of the intravascular fluid compartment occurred after the administration of hypertonic solution in this study. This osmotically induced et al., 1985; redistribution of fluid has been reported (SMITH et al., 1985; NAKAYAMA RAMAMOORTHY et al., 1990). The fluid shift was also demonstrated to be a fast-acting mechanism (MAZZONIet al., 1983). The dilution on our study was indicated by a decrease in packed cell volume, total protein content, plasma potassium concentration and red blood cell count. Surprisingly, no increase in plasma or blood volume was found in this study. Insufficient experience with this dilution technique might explain this finding. Due to the used time schedule it might also be possible that we missed the peak increase in plasma volume which is followed by a quick compensation mechanism. Frequent urinations were observed after the administration of the hypertonic solution in the standing ponies. The increase in diuresis was also observed in sheep in the hemmorrhagic shock model after administration of hypertonic solution (HANDSet al., 1987). Apparently a compensation for the occurring osmotic changes in the plasma induced this increase in diuresis. The increase in diuresis might be explained by a complex neurohormonal mechanism. Increase in plasma sodium concentration and distention of the atria (which occurs in cases of hypervolemia) induce a release of the atrial natriuretic factor (ANF) leading to a natriuresis and secondary water diuresis (BRENNER et al., 1990; BURNETT,1990). This mechanism has been proven to occur relatively fast (HANDSet al., 1987). Secondly, the increase in osmolality after administration of hypertonic solutions triggers the release of the antidiuretic hormone (ADH) (via the osmoreceptors), leading to a decrease in diuresis. O n the other hand, an increase in circulating volume after the infusion of hypertonic solution infusion stimulates the stretch and baroreceptors leading to a decreased secretion of ADH. Apparently the mechanism induced by the increase in circulating volume had a more important role leading to a global decrease in ADH. Finally, an increase in renal blood flow after hypertonic fluid administration was reported in dogs (MERMEL et al., 1986). This mechanism might also explain the observed increased diuresis, observed in the ponies of this study. No specific side-effects such as nervous disturbances or signs of phlebitis were observed in the standing ponies during and after the hypertonic fluid administration. N o specific changes in the different parameters were observed during the control period in the anaesthetized ponies. The increases in the plasma sodium and chloride concentrations were attributable to the administration of the hypertonic solution; the increases which were followed by a gradual decrease were comparable to the ones observed in the standing ponies. The peak increase in the osmolality observed in the anaesthetized ponies after the hypertonic saline administration was greater than the one observed in the standing ponies. The increase in osmolality was followed by a gradual decrease. A shift of fluids from the intracellular and interstitial spaces towards the vascular compartment was

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demonstrated by RAMAMOORTHY et al. (1990). A fluid shift was also present in the anaesthetized ponies of this study although no change in plasma or blood volume could be calculated 15 minutes after fluid administration. Nevertheless, the significant decreases in packed cell volume, total protein content, red blood cell count, and plasma potassium concentration after the infusions was a clear indication for a dilution. Decreases in these variables in the anaesthetized ponies was less accentuated compared to the changes observed in the standing ponies; the subsequent gradual normalization was also quicker in the anaesthetized ponies. The reasons for these differences were not clear. Since anaesthesia in horses was associated with the occurrence of several stress symptoms (such as increase in catecholamines) (ROBERTSON et al., 1990) it might be possible that a splenic contraction during anaesthesia contributed to the quicker normalization of the packed cell volume and the red blood cell count. The observed increase in the potassium plasma concentration at the end of anaesthesia was probably due to minimal muscle damage induced by dorsal recumbent position (JOHNSON et al., 1978) and was not related to the use of the hypertonic fluid administrations. Arterial blood gas tensions (P,02, P,C02) were not altered by the infusion of hypertonic saline solution; the changes in standard bicarbonate concentration remained within the physiological limits. A single infusion of hypertonic saline solution in standing ponies significantly affected the fluid balance (hemodilution) which was partly corrected by an increase in diuresis. The normalization of the observed changes was rather slow. The effect of hypertonic solutions in horses with an existing fluid imbalance remains uncertain. Nevertheless, we speculate beneficial effects, such as a decrease in packed cell volume and total protein content after the use of hypertonic solutions in colic horses with a hypotonic or moderate hypertonic dehydratation. In severe hypertonic hypovolemic horses, the infusions of these hypertonic saline solutions might induce a potentially dangerous peripheral dehydratation in muscles, intestines, and central nervous system. Recently, the hypertonic solutions have been demonstrated to be effective in counteracting endotoxemic shock in ponies (BERTONEet al., 1990) and experimentally induced gastric dilatationvolvulus shock in dogs (ALLENet al., 1991). Apparently, the infusions of hypertonic saline solutions in anaesthetized ponies were well tolerated. Further cardiovascular studies are needed to justify the use of these hypertonic solutions in horses before and during anaesthesia. References ALLEN,A,, E. SCHERTEL, W. MUIR, and A. VALENTINE, 1991: Hypertonic saline/dextrane resuscitation of dogs with experimentally induced gastric dilatation-volvulus shock. Am. J. Vet. Res. 52, 92-96. BAUE,A. E., E. T. TRAGUS, and W. H. PARKINS,1967: A comparison of isotonic and hypertonic solutions and blood on blood flow and oxygen consumption in the initial treatment of hemorrhagic shock. The Journal of Trauma 7, 743 -755. J. J., K. A. GOSSETT,K. E. SHOEMAKER, A. L. BERTONE, and H. L. SCHNEITER, 1990: Effect BERTONE, of hypertonic vs. isotonic saline solution on responses to sublethal E . coli endotoxemia in horses. Am. J. Vet. Res. 51, 999-1007, BRENNER, B. M., E. BALLERMANN, D. GUNNING,and F. ZEIDEL,1990: Diverse biological actions of Atrial natriuretic peptide. Physiol. Rev. 70, 665-699. BURNETT,J. C., 1990: Atrial natriuretic factor. Is it physiologically important? Circulation 82, 1523-1524. and A. BEATHMANN, DAUTERMAN, C., L. SCHORER,R. HARTL, S. BERGER,R. MURR, K. HEBNER, 1990: Treatment of hypovolemic shock with hypertonic-hyperoncotic solutions: Effects on regional CBF. Anesthesiology 73, 276-283. I. T. VELASCO, 0.V. LOPES,and M. ROCHAE SILVA,1980: Treatment of DE FELIPPE, J., J. TIMONER, refractory hypovolemic shock by 7.5 % Sodium chloride injections. The Lancet 2, 1002- 1004. DYSON,D. H., and P. J. PASCOE,1990: Influence of preinduction methoxamine lacatated Ringer solution, or hypertonic saline solution infusion or postinduction dobutamine infusion on anesthetic-induced hypotension in horses. Am. J. Vet. Res. 51, 17-21.

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HANDS. R., J. W. HOLCROFT, P. R. PERRON,and G. C. KRAMER, 1987: Comparison of peripheral and central infusions of 7.5 % NaC1/6 % dextran 70. Surgery 103, 684-689. HARDY, R. M., 1989: Hypernatremia. In Vet. Clinics of North Am., Small Animal Practice 19, No. 2, 231 -236. HOLCROFT, J. W., M. J. VASSAR, J. E. TURNER, R. W. DERLET,and G. C. KRAMER,1987: 3 % NaCl and 7.5 Yo NaCVDextran 70 in the resuscitation of severely injured patients. Ann. Surgery 206, 279-287. JOHNSON,B.D., R.B. HEATH,B.BOWMAN, R.W. PHILLIPS,L.D. RICH, and J.L. VOSS, 1978: Chemistry changes in horses during anaesthesia: a pilot study investigating the possible causes of postanaesthetic myositis in horses. J. Eq. Med. Surg. 2, 109-123. KLEEMAN, N. S., 1979: CNS manifestations of disordered salts and water balance. Hospital Practice, 60-73. KRAMER, G. C., P. R. PERRON,D. C. LINDSEY, SYHo HUNG, R. A. GUNTHER, W. A. BOYLE,and J. W. H O L C R O1986: ~ , Small-volume resuscitation with hypertonic saline dextran solution. Surgery 100,239-245. KREIMEIER,U., U. BRUECKNER, Y. SCHMIDT,and K. MESSMER,1990: Instantaneous restoration of regional organ blood flow after severe hemorrhage/effects of small volume resuscitation with hypertonic-hyperoncotic solutions. J. Surg. Res. 49,493 -503. LUYPAERT, P., J. L. VINCENT,M. DOMB,P.VAN DER LINDEN,S. BLECIC,G.AZIMI, and A.BERNARD, 1986: Fluid resuscitation with hypertonic saline in endotoxic shock. Circ. Shock 20, 311-320. MANINGAS, P. A., L. R. DE GUZMAN, M. S. TILMAN, C. S. HINSON, K. J. PRIEGNITZ, K. A. VOLK,and R. F. BELLAMY, 1986: Small volume infusion of 7.5 % NaCl in 6 YODextran 70 for the treatment of severe hemorrhagic shock in swine. Annals of Emergency Medicine 15, 1131-1137. MATHRU,M., M.ROONEY,M.VENGORLEKAR, L.J. HIRSCH, and T. K. RAo, 1990: Effect of hypertonic saline resuscitation on myocardial performance in a hemorrhagic shock model: assessment by pressure-volume loops. Anesthesiology 73, 635. MAZZONI,M. C., P. BORGSTROM, K. E. ARFORS,and M. INTAGLIETTA, 1983: Dynamic fluid redistribution in hyperosmotic resuscitation of hypovolemic hemorrhage. Am. J. Physiol. 255, 629-635. MERMEL,G. W., and W. A. BOYLE,1986: Hypertonic saline resuscitation following prolonged hemorrhage in the awake dog. Anesthesiology 65, 3A, 91. MONAFO,W. W., C. CHUNTRASAKUL, and V. AWAZIAN,1973: Hypertonic sodium solutions in the treatment of burn shock. Am. J. of Surgery 126, 778-783. MOYLAN, J. A., J. M. RECKLER, and A. D. MASON,1973: Resuscitation with hypertonic lactate saline in thermal injury. Am. J. of Surgery 125, 580-584. MUIR, W. W., and J. SALLY,1989: Small-volume resuscitation with hypertonic saline solution in hypovolemic cats. Am. J. Vet. Res. 50, 1883-1889. NAKAYAMA, S.I., G.C. KRAMER,R.C. CARLSEN, and J.W. HOLCROFT, 1985: Infusion of very hypertonic saline to bled rats: membrane potentials and fluid shifts. J. Surg. Res. 38, 180-186. NAKAYAMA, S. I. L. SIBLEY,R. A. GUNTHER,J. W. HOLCROFT, and G. KRAMER, 1984: Small-volume resuscitation with hypertonic saline (2,400 mosm/l) during hemorrhagic shock. Circ. Shock 13, 149-159. PENFIELD,W. G., 1919: The treatment of severe and progressive hemorrhage by intravenous injections. Am. J. Physiol. 48, 121 - 128. PERSON,S., 1967: O n blood volume and working capacity in horses. Acta Vet. Scand., supplement 19. PROUGH,D. S., J. C. JOHNSON,and E. H. STULKEN,1985: Effects on cerebral hemodynamics of resuscitation from endotoxic shock with hypertonic saline versus lactated Ringer’s solution. Crit. Care Med. 13, 1040-1044. PROUGH,D.S., J. C. JOHNSON,D.A. STUMP,E. H. STULKEN, G.V. POOLE,and G. HOWARD, 1986: Effects of hypertonic saline versus lactated Ringer’s solution on cerebral oxygen transport during resuscitation from hemorrhagic shock. J. Neurosurgery 64,627-632. RAMAMOORTHY, C., M.ROONEY,S. WAT, J. KALATHEEVITIL,M.MATHRU,and T. L. K. RAo, 1990: Small volume hypertonic NaCl resuscitation in a pedriatic hemorrhage model. Anesthesiology 73, 1110. RENCK,H., K. G. LJUNGSTROM, and H. HEDIN,1983: Prevention of dextran-induced anaphylactic reactions by hapten inhibition. Acta Chir. Scand. 149, 355-360. ROBERTSON, S. A., C. J. STEELE,and CHEN CHAO-LING,1990: Metabolic and hormonal changes associated with arthroscopic surgery in the horse. Equine Vet. J. 22, 313-316.

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ROCHAE SILVA,M., I. IRINEU,and M. PORFIRIO,1990: Hypertonic saline resuscitation: saturated salt-dextran solutions are equally effective, but induce hemolysis in dogs. Critical Care Medicine 18,203-211. R. I. NOGUEIRA DA SILVA,N. A. OLIVEIRA, G. A. NEGRAES, and ROCHAE SILVA,M., I.T. VELASCO, N. A. OLIVEIRA,1987: Hypersomatic sodium salts reverse severe hemmorrhagic shock: other solutes do not. Am. J. Physiol. 253, 751-762. SCHMALL, L. M., W. W. MUIR,and J. T. ROBERTSON, 1990 a: Haemodynamic effects of small volume hypertonic saline in experimentally induced hemorrhagic shock. Equine Vet. J. 22, 273-277. SCHMALL, L. M., W. W. MUIR,and J. T. ROBERTSON, 1990 b: Haematological, serum electrolyte and blood gas effects of small volume hypertonic saline in experimentally induced hemorrhagic shock. Equine Vet. J. 22,278-283. SMITH,G. G., G. C. KRAMER, P.PERRON,S.NAKAYAMA, R.A. GUNTHER,and J. W. HOLCROFT, 1985: A comparison of several hypertonic solutions for resuscitation of bled sheep. J. Surg. Res. 39, 517-528. STIFF,J. L., F. MUNCH,and B. BROMBERGER-BARNEA, 1979: Hypotension and respiratory distress caused by rapid infusion of mannitol or hypertonic saline. Anesth. Analg. 58, 42-48. TRAVERSO, L., R. F. BELLAMY, R. F. HOLLENBACH, and L. D. WITCHER,1987: Hypertonic sodium chloride solutions: effect on hemodynamics and survival after hemorrhage in swine. J. of Trauma 27, 32-39. VELASCO, I. T., V. PONTIERI, J. R. ROCHAE SILVA,and 0.V. LOPES,1980: Hyperosmotic NaCl and severe hemorrhagic shock. Am. J. Physiol. 239, 664-673. WALSH,J. C., J. ZHUANG, and S. R. SHACKFORD, 1991: A comparison of hypertonic to isotonic fluid in the resuscitation of brain injury and hemorrhagic shock. J. Surg. Res. 50, 284-292.

Influence of hypertonic saline solution 7.2% on different hematological parameters in awake and anaesthetized ponies.

The influence of hypertonic NaCl 7.2% infusion (4 ml/kg of body weight [BWT]) on plasma (PV) and blood (BV) volumes, sodium (Na), chloride (Cl), potas...
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