- Email: [email protected]
CHANGES IN PACKED CELL VOLUME DURING ANAESTHESIA
Praredinps of the 4th International Connress of Veterinarv Anaesthesia
CHANGES IN PACKED CELL VOLUME DURING ANAESTHESIA
I.G. Handel, G.E. Staddon', B.M.Q. Weaver, M.R.B. Pearson** and J.I. Cruz Madorran***. *Department of Medical Physics, Bristol General Hospital, Bristol, England. 'bepartment of Veterinary Clinical Studies, University of Sydney, Australia. ***Facultadde Veterinaria, Universidad de Zaragoza, Zaragoza, Spain. Introduction During anaesthesia, especially with barbiturates, the spleen is expected to dilate (Hahn, et aL, 1942) and, as a consequence, the packed cell volume (PCV) can be expected to fall. O n the other hand, factors leading to a stress response e.g. fear and apprehension as in handling conscious individuals can activate splenic contraction with a resultant increase in PCV (Gartner et al., 1969). It would seem likely therefore, that response to stimuli during anaesthesia could have a similar effect.
packed cell volume measurements were made on a bull anaesthetized with methohexitone followed by inhalation of halothane in oxygen. Two ewes were used to study packed cell volumes before and after induction of anaesthesia with thio&ntone followed by inhalation of oxygen only after endotracheal intubation. Seven ewes were used to study packed cell volumes in association with propofol anaesthesia. They were used on twenty three occasions, a period of at least two weeks elapsing before each ewe received another anaesthetic. In addition, on six occasions, PCV measurements were made on mnscious sheep for a minimum of thirty minutes. All the animals were judged to be clinically healthy each time they were studied.
During a study of the pharmacokinetics of propofol in sheep, transient rises in blood concentration occurred as reported elsewhere in this Congress. These, it was considered, might have been due to splenic contraction. Thus, PCV measurements were carried out to see if there were transient rises associated with the transient rises in propofol concentration and a comparison was made with PCV measurements made during anaesthesia in animals other than sheep and where a barbiturate was used to induce anaesthesia.
The ewes were not premedicated and for each set of measurements, the ewe was restrained gently in the standing position. Local analgesia was injected over each jugular vein at the site of venepuncture and a 1% catheter inserted. Each catheter was fitted with a Sway tap and sutured in position. Blood samples were taken at one minute intervals in the sheep that remained conscious and, in the sheep anaesthehd with propofol, samples were taken before and then at one minute intervals after the intravenous injection of the propofol (6 mg kg-') for approximately twenty minutes.
Materials and Methods Packed cell volume measurements were made on anaesthetized ponies on five occasions. The ponies were prernedicated with acepromazine and anaesthetkd with a barbiturate followed by halothane in oxygen. O n six occasions, similar measurements were made on sheep anaesthetized with a barbiturate followed by inhalation of enflurane in oxygen and on one occasion,
On two occasions, laI human serum albumin (0.4 MBq) was injected intravenously and subsequent serial blood samples were taken for esti-
347
pnxwedings of the 4th International Congress of Veterinary Anaesthesia
mation of plasma volume. Packed cell volumes from sheep anaesthetized with propofol were compared with the propofol blood concentration curves to see if changes were related to transient rises in propofol concentration.
Discussion
Changes in packed cell volume could be due to changes in plasma volume or in circulating red cell volume. In the two sheep anaesthetized with propofol where the plasma volume was measured, little change was seen in this volume, hence it was assumed that changes in PCV were due to changes in the number of circulating red blood cells. A similar conclusion was reached by one of us (M.R.B.P.) from a study of the effect of acepromazine and propofol on PCV and total plasma proteins in greyhounds. Since the spleen is known to be a reservoir for red blood cells it is assumed&t the changes in PCV were due to variable pooling of these cells in the spleen. It has been known for many years that barbiturates cause splenic dilatation (Hahn et al., 1942) and certainly, animals killed with an overdose of barbiturate do have large spleens (Webb and Weaver, 1981). One sheep killed this way was found to have a spleen at post mortem examination which weighed 670 g, and it may have been larger than this before death occurred (Pearson, 1988). Another sheep killed while deeply anaesthetized by an intravenous injection of potassium chloride to arrest the heart, was found at post mortem examination to have a spleen which was much smaller, weighing only 44 g, Sheep that were slaughtered were found to have spleens that were much smaller than sheep that were anaesthetized with pentobarbitone sodium (Turner and Hodgetts, 1959). The PCV was found to fall while the sheep were conscious and as they were becoming accustomed to b e i i restrained. It also fell during the first ten to fifteen minutes of anaesthesia in the sheep anaesthetized with propofol and also in the two animals which were anaesthetized with thiopentone (Fig. 3).
Results The PCV measurements made on the anaesthetized ponies and the bull showed fluctuations but the changes were minor and no consistent pattern was seen. Likewise, the six occasions when PCV measurements were made on sheep anaesthetized with a barbiturate followed by enflurane inhalation, little change was seen. However, there were few measurements in the first fifteen minutes after induction of anaesthesia. For the ewes where blood samples covered the early period with rapid sampling, in every case, the PCV fell over the first ten minutes of anaesthesia and generally continued to fall for approximately twenty minutes, none of the values were lower than nineteen (Fig. 1).
Pre-anaesthesia 40.5%
During anaesthesia
Table 1 Packed Cell Volume (PCV) in a sheep before and after induction of anaesthesia with thiopentone sodium Frequently, superimposed on the general trend, however, in the sheep anaesthetized with propofol, there were transient increases which often appeared to be associated with the transient rises in propofol concentration (Fig. 2). The PCV of conscious ewes was more erratic but also showed a fall over the period studied. Plasma volume estimations showed only slight variation and no transient changes.
Conclusion It would seem, from this study, that the PCV is 348
Proceedings of the 4th International Congmsi of Veterinary Anaesthesia
likely to fall during at least the frrst ten minutes of anaesthesia. Furthermore this study indicates that there is an association between splenic contraction and transient rises in plasma propofol concentration.
The work was carried out in the Wellcome Comparative Anaesthetic Laboratory which was provided by the Wellcome Trust. Financial support for the research was provided by the Perry Foundation.
References Gartner RJ.W., Callow L.L., Granzien C.K. and Pepper P.M. (1%9) Variations in the concentration of blood constituents in relation to the handling of cattle. Res. vet. Sci. 10,7-12. Hahn P.F., Bale W.F. and Bonner Jr, J.F. (1942) Removal of red cells from the active
circulation by sodium pentobarbital. Amer. J. Physiol. l.38,415420. Pearson, M.R.B. (1988) The Pharmacokinetics of inhaled anaesthetics in the sheep and ox. PbD. Thesis, p. 124,University of Bristol. Turner A.W. and Hodgetts V.E. (1959) The dynamic red cell storage function of the spleen in sheep. Aust. J. exp. Biol. 37,399-420. Webb A.I. and Weaver B.M.Q. (1981) Solubility of halothane in equine tissues at 37' C. Br. J. Anaesth. 53,479 - 486.
Acknowledgements
The authors are grateful to Mr. A. Jones and Ms. M. Graham for Catrying out the packed cell volume measurements and they are grateful to Mr. Jones and to Mrs. C. Phippen for general technical support. The authors are also grateful to Mr. G. Bird and Mr. S. Leader for assistance with the animals. Grateful thanks are due to Messrs. M. Parsons and J. Conibear for the preparation of the illustrations.
349
20
25
33
3
40
45
PC
0
I
I
I
I
5
I I
I 1
I
1
I
I
I
I
I
10 15 minutes after injection
I
I
I
I
x)
I
I
a
I
* *
I
25
1
Bolus + Halothane Bolus only Bolus + Isoflurane t Bolus only Infusion Bolus only
Packed Cell Volume(PCV) measurements following induction of anaesthesia with Propofol in individual sheep
Procccdinpr of the 4th International Con-
of Veterinary Anaesthesia
G>
N 00
G)
N
0
0 P
0
CD
0
n
01
TI
7
3 -.
0 U 0
3
c
0
0
3 0
m
3
rc
aa
a2 U 0
N
0
0
z-.
rc
0
3 I
0
v)
0
m m
3
r
U 0
ul
0
35 1
Proceedings of the 4th International Congress of Vcterinaw Anaesthesia
0 3 -
tii
352
Kl
CHANGES IN PACKED CELL VOLUME DURING ANAESTHESIA
I.G. Handel, G.E. Staddon', B.M.Q. Weaver, M.R.B. Pearson** and J.I. Cruz Madorran***. *Department of Medical Physics, Bristol General Hospital, Bristol, England. 'bepartment of Veterinary Clinical Studies, University of Sydney, Australia. ***Facultadde Veterinaria, Universidad de Zaragoza, Zaragoza, Spain. Introduction During anaesthesia, especially with barbiturates, the spleen is expected to dilate (Hahn, et aL, 1942) and, as a consequence, the packed cell volume (PCV) can be expected to fall. O n the other hand, factors leading to a stress response e.g. fear and apprehension as in handling conscious individuals can activate splenic contraction with a resultant increase in PCV (Gartner et al., 1969). It would seem likely therefore, that response to stimuli during anaesthesia could have a similar effect.
packed cell volume measurements were made on a bull anaesthetized with methohexitone followed by inhalation of halothane in oxygen. Two ewes were used to study packed cell volumes before and after induction of anaesthesia with thio&ntone followed by inhalation of oxygen only after endotracheal intubation. Seven ewes were used to study packed cell volumes in association with propofol anaesthesia. They were used on twenty three occasions, a period of at least two weeks elapsing before each ewe received another anaesthetic. In addition, on six occasions, PCV measurements were made on mnscious sheep for a minimum of thirty minutes. All the animals were judged to be clinically healthy each time they were studied.
During a study of the pharmacokinetics of propofol in sheep, transient rises in blood concentration occurred as reported elsewhere in this Congress. These, it was considered, might have been due to splenic contraction. Thus, PCV measurements were carried out to see if there were transient rises associated with the transient rises in propofol concentration and a comparison was made with PCV measurements made during anaesthesia in animals other than sheep and where a barbiturate was used to induce anaesthesia.
The ewes were not premedicated and for each set of measurements, the ewe was restrained gently in the standing position. Local analgesia was injected over each jugular vein at the site of venepuncture and a 1% catheter inserted. Each catheter was fitted with a Sway tap and sutured in position. Blood samples were taken at one minute intervals in the sheep that remained conscious and, in the sheep anaesthehd with propofol, samples were taken before and then at one minute intervals after the intravenous injection of the propofol (6 mg kg-') for approximately twenty minutes.
Materials and Methods Packed cell volume measurements were made on anaesthetized ponies on five occasions. The ponies were prernedicated with acepromazine and anaesthetkd with a barbiturate followed by halothane in oxygen. O n six occasions, similar measurements were made on sheep anaesthetized with a barbiturate followed by inhalation of enflurane in oxygen and on one occasion,
On two occasions, laI human serum albumin (0.4 MBq) was injected intravenously and subsequent serial blood samples were taken for esti-
347
pnxwedings of the 4th International Congress of Veterinary Anaesthesia
mation of plasma volume. Packed cell volumes from sheep anaesthetized with propofol were compared with the propofol blood concentration curves to see if changes were related to transient rises in propofol concentration.
Discussion
Changes in packed cell volume could be due to changes in plasma volume or in circulating red cell volume. In the two sheep anaesthetized with propofol where the plasma volume was measured, little change was seen in this volume, hence it was assumed that changes in PCV were due to changes in the number of circulating red blood cells. A similar conclusion was reached by one of us (M.R.B.P.) from a study of the effect of acepromazine and propofol on PCV and total plasma proteins in greyhounds. Since the spleen is known to be a reservoir for red blood cells it is assumed&t the changes in PCV were due to variable pooling of these cells in the spleen. It has been known for many years that barbiturates cause splenic dilatation (Hahn et al., 1942) and certainly, animals killed with an overdose of barbiturate do have large spleens (Webb and Weaver, 1981). One sheep killed this way was found to have a spleen at post mortem examination which weighed 670 g, and it may have been larger than this before death occurred (Pearson, 1988). Another sheep killed while deeply anaesthetized by an intravenous injection of potassium chloride to arrest the heart, was found at post mortem examination to have a spleen which was much smaller, weighing only 44 g, Sheep that were slaughtered were found to have spleens that were much smaller than sheep that were anaesthetized with pentobarbitone sodium (Turner and Hodgetts, 1959). The PCV was found to fall while the sheep were conscious and as they were becoming accustomed to b e i i restrained. It also fell during the first ten to fifteen minutes of anaesthesia in the sheep anaesthetized with propofol and also in the two animals which were anaesthetized with thiopentone (Fig. 3).
Results The PCV measurements made on the anaesthetized ponies and the bull showed fluctuations but the changes were minor and no consistent pattern was seen. Likewise, the six occasions when PCV measurements were made on sheep anaesthetized with a barbiturate followed by enflurane inhalation, little change was seen. However, there were few measurements in the first fifteen minutes after induction of anaesthesia. For the ewes where blood samples covered the early period with rapid sampling, in every case, the PCV fell over the first ten minutes of anaesthesia and generally continued to fall for approximately twenty minutes, none of the values were lower than nineteen (Fig. 1).
Pre-anaesthesia 40.5%
During anaesthesia
Table 1 Packed Cell Volume (PCV) in a sheep before and after induction of anaesthesia with thiopentone sodium Frequently, superimposed on the general trend, however, in the sheep anaesthetized with propofol, there were transient increases which often appeared to be associated with the transient rises in propofol concentration (Fig. 2). The PCV of conscious ewes was more erratic but also showed a fall over the period studied. Plasma volume estimations showed only slight variation and no transient changes.
Conclusion It would seem, from this study, that the PCV is 348
Proceedings of the 4th International Congmsi of Veterinary Anaesthesia
likely to fall during at least the frrst ten minutes of anaesthesia. Furthermore this study indicates that there is an association between splenic contraction and transient rises in plasma propofol concentration.
The work was carried out in the Wellcome Comparative Anaesthetic Laboratory which was provided by the Wellcome Trust. Financial support for the research was provided by the Perry Foundation.
References Gartner RJ.W., Callow L.L., Granzien C.K. and Pepper P.M. (1%9) Variations in the concentration of blood constituents in relation to the handling of cattle. Res. vet. Sci. 10,7-12. Hahn P.F., Bale W.F. and Bonner Jr, J.F. (1942) Removal of red cells from the active
circulation by sodium pentobarbital. Amer. J. Physiol. l.38,415420. Pearson, M.R.B. (1988) The Pharmacokinetics of inhaled anaesthetics in the sheep and ox. PbD. Thesis, p. 124,University of Bristol. Turner A.W. and Hodgetts V.E. (1959) The dynamic red cell storage function of the spleen in sheep. Aust. J. exp. Biol. 37,399-420. Webb A.I. and Weaver B.M.Q. (1981) Solubility of halothane in equine tissues at 37' C. Br. J. Anaesth. 53,479 - 486.
Acknowledgements
The authors are grateful to Mr. A. Jones and Ms. M. Graham for Catrying out the packed cell volume measurements and they are grateful to Mr. Jones and to Mrs. C. Phippen for general technical support. The authors are also grateful to Mr. G. Bird and Mr. S. Leader for assistance with the animals. Grateful thanks are due to Messrs. M. Parsons and J. Conibear for the preparation of the illustrations.
349
20
25
33
3
40
45
PC
0
I
I
I
I
5
I I
I 1
I
1
I
I
I
I
I
10 15 minutes after injection
I
I
I
I
x)
I
I
a
I
* *
I
25
1
Bolus + Halothane Bolus only Bolus + Isoflurane t Bolus only Infusion Bolus only
Packed Cell Volume(PCV) measurements following induction of anaesthesia with Propofol in individual sheep
Procccdinpr of the 4th International Con-
of Veterinary Anaesthesia
G>
N 00
G)
N
0
0 P
0
CD
0
n
01
TI
7
3 -.
0 U 0
3
c
0
0
3 0
m
3
rc
aa
a2 U 0
N
0
0
z-.
rc
0
3 I
0
v)
0
m m
3
r
U 0
ul
0
35 1
Proceedings of the 4th International Congress of Vcterinaw Anaesthesia
0 3 -
tii
352
Kl