|Year : 2016 | Volume
| Issue : 4 | Page : 95-100
The reference values for hepatic oxygen consumption and net lactate production, blood gasses, hemogram, major electrolytes, and kidney and liver profiles in anesthetized large white swine model
Mohamed Bekheit1, Petru Bucur1, Eric Vibert1, Christian Andres2
1 Department of Liver Surgery and Transplantation, Inserm, Unité 1193; AP-HP - Hôpital Paul Brousse, Centre Hépato-Biliaire, Villejuif, France
2 Service de Biochimie, CHRU Tours, Tours, France
|Date of Submission||06-Sep-2016|
|Date of Acceptance||09-Dec-2016|
|Date of Web Publication||3-Jan-2017|
AP-HP - Hôpital Paul Brousse, 12 Avenue Paul Vaillant-Couturier, 94804 Villejuif Cedex
Source of Support: None, Conflict of Interest: None
Aim: Pigs are extensively used as experimental models to study the human physiology and pathophysiological conditions. Knowledge of the normal values of the commonly used parameters is indispensable to the correct interpretation of the test results. This study reports on the normal hemogram, blood gas, major electrolytes, kidney and liver profiles, hepatic oxygen consumption, and net lactate production in a large white pig model. Methods: Twenty-five female large white pigs were included in this study. Blood gas samples were collected from the portal and hepatic veins as well as the carotid artery. Results: The mean hemoglobin level was 97.7 ± 15.8 g/L. white blood cells were 13.5 ± 3.3 10  /mm  , and platelet count was 279 ± 104.6 10  /mm  . The mean aspartate aminotransferase, alanine aminotransferase, gamma-glutamyltransferase, alkaline phosphatase, total bilirubin, and direct bilirubin were 83.8 ± 73.9 IU/L, 43.7 ± 5.9 IU/L, 33.6 ± 8.6 IU/L, 296.5 ± 39.7 IU/L, 5.6 ± 3.2 mmol/L, and 1.6 ± 0.73 mmol/L. The mean albumin level was 29 ± 3.9 g/L. The mean ammonia and arterial lactate levels were 49.1 ± 45.67 mmol/L and 1.5 ± 0.46 mmol/L. Kidney profile parameters were comparable to human values. Hepatic oxygen consumption was 17.3 ± 9.7 mL/100 g liver tissue/min and net hepatic lactate production was 0.017 ± 0.03 mmol/L. Conclusion: Knowledge of the normal parameters is mandatory for accurate interpretation of the experimental results that involves large white animals.
Keywords: Blood gases, hepatic, lactate, liver, normal, oxygen, reference, swine
|How to cite this article:|
Bekheit M, Bucur P, Vibert E, Andres C. The reference values for hepatic oxygen consumption and net lactate production, blood gasses, hemogram, major electrolytes, and kidney and liver profiles in anesthetized large white swine model. Transl Surg 2016;1:95-100
|How to cite this URL:|
Bekheit M, Bucur P, Vibert E, Andres C. The reference values for hepatic oxygen consumption and net lactate production, blood gasses, hemogram, major electrolytes, and kidney and liver profiles in anesthetized large white swine model. Transl Surg [serial online] 2016 [cited 2019 Aug 17];1:95-100. Available from: http://www.translsurg.com/text.asp?2016/1/4/95/197495
| Introduction|| |
Animals are extensively used in research to simulate various clinical situations, and large white pigs are among those widely used as a large surgical model. , In many situations, blood samples are required at different stages of the various experiments conducted on these animals. ,
Pigs, as well as other animals, are frequently influenced by the change in the environment in a manner that might alter the results of the laboratory tests.  Particularly, the blood gas samples are sensitive to stress,  similar to humans.  In addition, restraining large animals for blood sample withdrawal presents challenges. For these reasons, blood samples are usually collected under anesthesia. However, anesthesia has no significant effect on several measurements.  Knowledge of normal biochemistry and hematology values under practical experimental conditions is, therefore, fundamental.
The aim of this study was to describe the normal values of the blood gas, major electrolytes within the portal and systemic blood, and the hepatic and renal function parameters.
| Methods|| |
Approval of the committee of ethics of animal research, Ministry of Higher Education and Scientific Research, and Ministry of Agriculture and Fishing was obtained, complying with the European Union Directive N° 2010/63/EU.
Surgeries were performed at the CIRE platform, INRA Centre Val de Loire, Nouzilly, France. Samples were taken to the central laboratory at the University Hospital of Tours for analysis.
Twenty-five large white female pigs were included in the study. The average age was 3 months ± 15 days. The mean weight was 35.9 ± 7.5 kg.
Animals fasted the night before the surgery. A preanesthetic preparation was given to the animals in their individual cages on the day of surgery as 30 mg/kg ketamine (KETAMINE PANPHARMA 250 mg/5 mL) and 0.03 mg/kg acepromazine (Calmivet, Vetoquinol, France).
Inside their cages, each pig received 2 mL xylazine 2%, with 15 mL ketamine (KETAMINE PANPHARMA 250 mg/5 mL) for anesthesia induction. A tracheal tube, size 6-7 mm (Portex, France), was then placed and secured. Subsequently, inhalational anesthesia was started using 60% FiO 2 inhalational oxygen mixed with 2% isoflurane (Isoflurane Belamont, Centre des Spécialités Pharmaceutiques, France) at a rate of 2-3 mL mixed with 1.5-2 L/min oxygen in 1.5 L of air.
Blood sample withdrawal
The right internal jugular vein was cannulated with an 8 Fr vascular Desivalve (Vygon, Ecouen, France) cannula. The vascular cannulation is performed through a midline neck incision that is used for contemporaneous carotid artery cannulation for the hemodynamic monitoring.
Thirty milliliters of blood was withdrawn from the jugular vein and sent to the central laboratory unit in universal tubes for analysis.
After the overnight fast, blood samples were collected by venipuncture 20 min after the induction of anesthesia. Samples for hematological analysis were collected in ethylenediaminetetraacetic acid tube. For chemistry analysis; samples were collected in fluoride tubes and buffered sodium citrate. Serum was mixed with 0.8 mg aprotinin, centrifuged at 2000 ×g at 4°C for 15 min within 30 min after puncture, and incubated in an ice container until delivery. Delivery time to the laboratory occurred within 45 min following centrifugation.
Blood samples for gas analysis after midline abdominal incision:
- One milliliter of arterial blood was withdrawn from the right carotid artery
- One milliliter of venous blood was withdrawn from the right suprahepatic vein by direct puncture using a 30-gauge needle
- One milliliter of portal venous blood was withdrawn from the portal vein by direct puncture of the portal vein using a 30-gauge needle.
Hepatic oxygen consumption is calculated as described elsewhere.  The hepatic oxygen consumption is calculated using the equation:
([hemoglobin (Hb) g/dL × 1.34 × SaO 2 + 0.003 × PaO 2 ] × hepatic arterial flow [HAF]) + ([Hb × 1.34 × SpO 2 + 0.003 × PpO 2 ] × portal vein flow [PVF]) − ([Hb × 1.34 × SvO 2 + 0.003 × PvO 2 ] × [HAF + PVF]). [Equation 1]
The flow used in the equation is adjusted to the liver volume by a simple transformation (flow × 100/liver volume).
The net hepatic lactate production is calculated using the same principle:
(Arterial lactate × HAF) + (Portal lactate × PVF) − (Hepatic venous lactate × [HAF + PVF]). [Equation 2]
Data presentation and analysis
The data are presented in the summative form. Mean or median was used as central tendency measures, and multiple dispersion measures were given for precision and to facilitate exploitation. The data summary was created using SPSS, version 21 (IBM ® SPSS ® , Chicago, IL, USA).
| Results|| |
In the gas analysis, the mean arterial pH was 7.393 ± 0.09117, the venous pH was 7.378 ± 0.168, and the portal pH was 7.335 ± 0.08816. The mean arterial pCO 2 was 45.89 ± 12.54 mmHg, the venous pCO 2 was 55.37 ± 13.36 mmHg, and the portal pCO 2 was 56.82 ± 13.73 mmHg. The mean arterial pO 2 was 273.6 ± 63.8 mmHg, the venous pO 2 was 37.32 ± 9.108 mmHg, and the portal pO 2 was 45.65 ± 10.12 mmHg. The mean arterial SO 2 was 99.81 ± 0.1311%, the venous SO 2 was 64.27 ± 14.89%, and the portal SO 2 was 75.35 ± 8.802%. The mean arterial lactate was 1.462 ± 0.4654 mmol/L, the venous lactate was 1.272 ± 0.3431 mmol/L, and the portal lactate was 1.451 ± 0.4228 mmol/L [Table 1], [Table 2] and [Table 3].
The mean blood urea nitrogen (BUN) level was 3.208 ± 1.348 mmol/L and the mean creatinine level was 95.5 ± 20.51 mmol/L. The mean plasma sodium level was 138.3 ± 2.188 mEq/L and potassium 4.875 ± 0.9196 mEq/L [Table 4].
|Table 4: BUN, creatinine, and major electrolytes levels in anesthetized animals |
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The mean total bilirubin level was 5.583 ± 3.175 mmol/L and the mean total protein level was 50.67 ± 6.88 g/L. The mean ammonia level was 49.1 ± 45.67 mmol/L and the mean lactate level was 2.013 ± 0.9827 mmol/L. [Table 5] summarizes the main hepatic functions and enzyme levels. The mean venous Hb level was 97.67 ± 15.84 g/L and the mean hematocrit level was 29.41 ± 5.037%. The mean venous white blood cell was 13.51 ± 3.355 103/mm  and the mean platelets count was 279 ± 104.6 103/mm  [Table 6].
|Table 5: Hepatic profile from samples collected from the internal jugular vein |
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|Table 6: Major hemogram parameters in samples collected from the internal jugular vein |
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The mean hepatic oxygen consumption was 17.32 ± 9.671 mL/100 g liver tissue/min and the mean net hepatic lactate production was 0.01682 ± 0.02719 mmol/L [Table 7].
|Table 7: Calculated hepatic net oxygen consumption and lactate production |
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The mean arterial Hg was 8.508 ± 1.738 g/dL and the mean arterial hematocrit is 25.00 ± 5.081%. The mean portal Hb level was 8.625 ± 1.805 g/dL and the hematocrit was 25.18 ± 5.564% [Table 8].
|Table 8: Hemoglobin and hematocrit levels measured in each sample type of gas analysis |
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The mean arterial calcium level was 0.8961 ± 0.2321 mmol/L, the venous calcium level was 0.7861 ± 0.2276 mmol/L, and the mean portal calcium was 0.77 ± 0.2326 mmol/L [Table 9].
|Table 9: Calcium levels as measured by gas analyzer in the arterial, venous, and portal venous samples |
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| Discussion|| |
Reported here is what is expected to be the first of a series of comprehensive routine baseline values in large white pigs. Samples were collected under anesthesia, and xylazine-ketamine  was used for induction. This protocol was reported not to influence the blood gas analysis. 
The lowest calcium concentration was found in samples collected from the portal vein. Kallner  found that postprandial calcium is lower than before meals. In our animals, the pH of the portal venous blood was lower than in other sample types. This makes the alkaline tide effect, in which an increase in the pH would result in a reduction of the ionized calcium level,  unlikely to be the explanation for this difference given that the lactate levels in the portal blood were the highest.
The difference between the arterial and venous concentration of calcium is known in the literature.  Perhaps, this difference is related to the increased protein contents  in the portal blood which reduces the ionized calcium levels, which we did not test in our experimental setting. Calcium levels in our experiments were generally higher than values in humans. 
Perhaps, the elevated serum calcium is a contributing factor to the higher coagulability of blood of animals as compared to that of humans.  In this study, we found that the normal coagulation profile of large white pigs exceeds the human profile. Since kits dedicated for humans were used, the ability to accurately identify the activity except that it exceeded 100%. It was previously reported that prothrombin activity is higher in pigs than in humans.  Analysis of the coagulation profile was not precise in our animals since their values were beyond the reference values in our laboratory. Platelet count, on the other hand, was comparable to that of the human level. 
The difference in Hb concentration was small between the different samples; however, both Hb and hematocrit levels were higher in venous blood than in arterial and portal blood samples. These values are lower than in humans. , In addition, leukocyte count was slightly higher than in healthy humans. 
BUN and serum creatinine levels are within ranges that correspond to the normal values of healthy humans.  Similarly, serum sodium  and chloride levels are equivalent to those in healthy humans. Potassium levels, however, were slightly higher than in humans. 
The pCO 2 levels were significantly lower in arterial samples compared to venous and portal venous samples with a smaller difference than what was found in other studies.  The arterial values of pCO 2 in our animals were slightly higher than the corresponding values in humans.  However, this increase in the arterial pCO 2 values might be attributed to the effect of anesthesia  or as a result of ketamine-induced respiratory depression.  The gap between the arterial and venous pCO 2 might reflect some degree of tissue hypoxia in anesthetized animals  with a resultant increase in pCO 2 production from anaerobic metabolism.  This was not, however, associated with a significant reduction in pH, which might suggest that different physio-metabolic pathways play a major role in the difference in the observed values.
Lactate levels were lower in the venous samples, taken from the suprahepatic vein, than in the arterial or the portal vein. This implies that the liver actively metabolizes lactate.  However, a net lactate production was seen in these animals, which is contrary to the findings observed in transplanted individuals.  Nevertheless, it should be noted that the amount of splanchnic lactate is influenced by the fraction of inspired oxygen,  which in the current study's protocol is relatively high.
Lactate values in the portal blood were higher than in venous samples. This might be attributed to the activity of the different intestinal flora in the production of lactate.  In addition, this might contribute to the relatively higher unconjugated bilirubin fraction compared to the human individual. 
Oxygen tension and saturation were both higher in portal samples than in venous samples. The difference in oxygen saturation between the arterial and venous samples was reported to be an indicator of tissue oxygen delivery.  However, upon observation, this interpretation is not feasible due to the artificial increase in oxygenation of animals under anesthesia. Posthepatectomy, hepatic oxygen consumption was identified as a mediator for liver regeneration.  Similarly, serum lactate has been described as a prognostic marker after live resection. 
Hepatic transaminase levels were higher in these animals than reported for healthy humans.  Both direct and total bilirubin levels were within a similar range to that described for healthy humans.
| Conclusion|| |
To ensure accurate interpretation of the experimental results, it is important to be aware of the reported porcine normal hematological and biological parameters. Some differences between these parameters and the corresponding human parameters do exist, and it should be considered before extrapolation of the human parameter values onto the porcine values. This study confirms agreement between some human and porcine parameters and reports some differences as well.
The authors would like to acknowledge of Hans Adriansen, Francois Le Compte at the INRA, Tours, France, for their role in data acquisition.
Financial support and sponsorship
This study was funded mainly by the "Agence de la Biomedecine" through its program of Research (AOR 2009). Eric Vibert, Petru O. Bucur, and Mohamed Bekheit acknowledge funding by project ANR-13-TECS-0006 (IFlow).
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9]