Medycyna Wet. 2006, 62 (12) 1383
Praca oryginalna Original paper
The ease of maintenance and the economical ad-vantages render rabbits preferable for experimental studies (26). Recently rabbits have been taken in as pets, also commonly used in cardiovascular and neu-rological studies. Constant cardiovascular monitoriza-tion, selection of anesthetics least depressive on the cardiovascular system and an attentive dosage will ensure a safe and effective anesthesia in rabbits (5).
Propofol is an intravenous anesthetic agent belon-ging to the alkyl phenol group. It has an isotonic struc-ture and a neutral pH. It can be applied with or without premedication (6). Propofol has a short acting period. Anesthesia is established fast and without an excita-tion period within 20 to 40 seconds following its I.V. injection. This allows an adequate anesthesia depth for endotracheal intubation. The recovery period for the anesthetic is also short and complication free (10, 20). Respiratory depression and hypotension are the most common complications of propofol applications (1, 14). Following its application and prior to surgical anesthetic period being established, a respiratory depression may occur (10). The decrease which propofol induces in the peripheral vascular resistance creates a decrease in the mean arterial blood pressure.
The decrease in the mean arterial blood pressure and cardiac output causes in turn a decrease in myocardial contractility (21, 27). Propofol may cause bradycardia and asystoly. However, important changes in the heart rate values will not occur if not administered at high doses (19, 27). Slow IV induction of propofol may prevent its depressive effects on the heart and respira-tory systems (23). Propofol also possesses cardiopro-tective properties (22), its structural resemblance to vitamin E inhibits the formation of free radicals (18). It has been shown that propofol, decreases postis-chemic myocardial mechanical dysfunction, infarct size and histological degeneration (18).
Propofol also reduces body temperature by causing peripheral vasodilatation (15, 17).
For long-term anesthetic procedures, propofol alone is insufficient in rabbits. The anaesthesia should be maintained with an inhalation anaesthetic. In addition, it is crucial to provide adequate oxygen support to increase the quality of anaesthesia (1).
The pediatric circuit anaesthesia device with non-rebreathing system is the common choice for rabbits (8). Halothane, isoflurane or sevoflurane can be used for the inhalation anaesthesia (9, 11). Sevoflurane is
Effects of propofol and sevoflurane anesthesia on some
physiological and biochemical parameters in rabbits
OZLEM GUZEL, GULDAL INAL*, ZEYNEP T. CIRAKLI**, EVREN ERASLAN*, MUSTAFA AKTAS
Department of Surgery, Faculty of Veterinary Medicine, Istanbul University, 34320, Avcilar, Istanbul/Turkey *Department of Physiology, Faculty of Veterinary Medicine, Istanbul University, 34320, Avcilar, Istanbul/Turkey
**Dr. Sadi Konuk Research and Training Hospital, 34149, Bakirkoy, Istanbul/Turkey
Guzel O., Inal G., Cirakli Z. T., Eraslan E., Aktas M. Effects of propofol and sevoflurane anesthesia
on some physiological and biochemical parameters in rabbits Summary
The effects of propofol and sevoflurane anesthesia on heart rate and respiratory rate, body temperature, plasma Ca, P, Na, K, Mg, creatinine, urea, ALT, APT, ALP, GGT, LDH in rabbits have been assessed. This study was carried out on 12 New Zealand White rabbits. Anesthesia induction was performed using propofol, which was slowly administered via IV injection at a dose of 10 mg/kg. Sevoflurane inhalation was administered at an initial concentration of 5%, followed by 2% for anesthesia maintenance. While causing a decrease in heart rate and respiratory frequency, propofol application but did not affect body temperature and hematocrite value. Sevoflurane did not alter heart rate, although it caused respiratory depression and a decrease in body temperature. Propofol-sevoflurane anesthetic combination caused some alterations in ALT and GGT liver enzymes and plasma phosphorus levels. In the light of the findings, the animals had a reliable and controlled anesthesia with the propofol-sevoflurane combination. However, it should be taken into consideration that this combination may impair the electrolyte balance and cause respiratory depression. Thus it has been concluded that a diligent monitorization and an electrolyte support is essential during the period of anesthesia.
Medycyna Wet. 2006, 62 (12) 1384
one of the newest volatile anesthetic drugs. It ensures a fast induction and recovery. Its depressive effects on the cardiovascular and respiratory systems are very few compared to isoflurane and halothane. Halothane sen-sitizes the heart against catecholamines, which leads to arrhythmias. However, these negative effects are not present with sevoflurane. Sevoflurane induces the least depression on the myocardial contractility (9, 11, 23). Volatile drugs possess cardioprotective properties (18, 22). Halothane and isoflurane decrease the infarc-tion surface. Whereas sevoflurane, diminishes infarct size, increases postischemic ventricular function and coronary vasculature, the latest by reducing the neu-trophil sequestration (18). Sevoflurane, similar to pro-pofol can induce hypothermia during anesthesia (15, 17).
It is important to reduce deaths due to anesthesia especially during experimental studies. The present study has been conducted with propofol and sevoflu-rane; and aimed to investigate their effects on heart and respiratory rate, hematocrite, body temperature and some physiological and biochemical plasma para-meters.
Material and methods
Seven male and 5 female New Zealand White rabbits with a mean body weight of 2.67 ± 0.22 kg were used in this study (n = 12). Animals were fed on standard rabbit chow and water ad libitum and housed in individual cages. The Ethics Committee of the University of Istanbul, Veterinary Faculty, approved this study.
All the animals used in this study are assessed in three groups as fallows, control (C), propofol (P) and sevoflura-ne (S). Measurement taken 15 minutes before asevoflura-nesthesia were used as data of control group, measurements taken 5 minutes after propofol and 15 minutes after sevoflurane applications were used as data of propofol and sevoflurane groups respectively.
A 22 G catheter was placed in the lateral auricular vein of the right auricula for IV anesthetics injections. Blood samples were obtained from the other auricular vein. 10 ml of heparinized blood was collected from each animal prior to and following anesthesia applications. Following the determination of hematocrite levels of each specimen, plasma was separated for biochemical analyzes.
Calcium (Ca), phosphate (P), sodium (Na), potassium (K), magnesium (Mg), aspartate aminotranspherase (AST), alanine aminotranspherase (ALT), alkaline phosphatase (ALP), gamma-glutamiltranspherase (GGT), lactate dehydrogenase (LDH), urea, and creatinine levels were determined by Beckman Coulter auto-analyzer LX20 with its original kits.
To determine the heart rates, electrocardiographic (ECG) values were recorded from all the rabbits during 5 minutes periods just before and after anesthesia inductions; this was carried out using the IInd standard extremity lead
(Petas--Kardiopet® 300, Petas-Turkey). Heart rates were
determi-ned as averages of the measurements obtaidetermi-ned from these records. Also at the same time, the respiratory rate was
determined by visual examination of the chest. Body temperature was measured via the rectum using a digital thermometer.
Anesthesia was induced via slow IV injection of propo-fol at a dose of 10 mg/kg of Diprivan® (Astra Zeneca/
Sweden). Following the next 2 minutes after propofol induction, the epiglottis was depressed using a number 0 laryngoscope tip and the animals were intubated with 3 mm cuffed intubation tubes (Kendall-Curity®/Thailand) and
blood was collected for physiological and biochemical parameters. At the end of 5 minutes, the rabbits were con-nected to the anesthesia machine (BOC-Boyle Internatio-nal) with a non-rebreathing system. Initially, the cases were only given 100% oxygen ventilation for a few minutes, and then sevoflurane was administered at a concentration of 5% of Sevorane® (Liquid-Abbott/ England) by inhalation.
All the cases reached a surgical anesthesia with 3 to 4 mi-nutes of 5% sevoflurane application. During this stage it was observed that a satisfactory level of amesia, analgesia and muscle relaxation had been achieved and that the pedal reflex had disappeared, while the respiration being regular, deep and slow. Thereafter the anesthesia was continued at a dose of 2% of sevoflurane for 30 minutes. Blood specimen was collected from each rabbit 15 minutes after sevoflurane inhalation. At the end of this time anesthesia was stopped, the catheter and electrodes re-moved away, and the rabbits were kept under observation until all the reflexes returned.
In 2 cases apnea developed following propofol, these ones received positive pressure ventilation with 100% O2 until spontaneous respiration was gained.
The results are expressed with their mean values and standard error. The differences between the control and propofol groups, and propofol and sevoflurane groups were calculated using the Paired-Sample t-test. Differences were considered significant when p < 0.05. The statistical analy-ses were conducted with the SPSS10 software program.
Results and discussion
Plasma electrolyte values of the control and experi-mental groups are detailed in table 1. It was demon-strated that the anesthetics used in this study did not change the plasma Ca and Na concentrations. On the other hand K levels decreased after sevoflurane inhalation compared to propofol application (p < 0.05). Plasma P and Mg levels increased significantly both following propofol and sevoflurane applications (p < 0.05).
Tab. 1. Some plasma electrolyte values (n = 10; x ± SE)
s e t y l o rt c e l E (C1o5nmrtoinl) P(0rompoifno)l Se(v1o5lfmuriann)e ) l d / g m ( a C 14.02 0.191 13.99 0.265 13.76 0.257 ) l d / g m ( P 4.52 0.322 5.08* 0.375 5.35* 0.4 ) L /l o m m ( a N 142.0 1.0 143.89 0.75 143.0 0.96 ) L /l o m m ( K 4.5089 0.1415 4.0411 0.2029 3.834* 0.206 ) l d / g m ( g M 2.502 0.1231 2.984* 0.1622 2.397* 0.2245 Explanation: * p < 0.05
Medycyna Wet. 2006, 62 (12) 1385
Liver enzymes, plasma urea and creatinine values are detailed in table 2. Although the anesthetic couple did not cause significant changes on plasma AST, ALP, LDH and urea levels, ALT levels decreased after se-voflurane application compared to propofol (p < 0.05), and GGT levels increased following propofol applica-tion compared to the control group (p < 0.05). Plasma creatinine levels showed significant increase following propofol application (p < 0.05).
Control and experimental data concerning heart and respiratory rates, body temperature and hematocrite levels are detailed in table 3. It was observed that 10 mg of propofol per body weight decreased heart rate com-pared to the control values (p < 0.05). In comparison to propofol, heart rate values following sevoflurane application did not show significant changes. The results regarding the respiratory rate shows that pro-pofol application decrease respiration compared to the control values (p < 0.05). It was also stated that sevo-flurane inhalation decreased respiration rate compa-red to propofol (p < 0.05). While body temperature values obtained after propofol application did not change compared to the control, sevoflurane has de-creased body temperature when compared to propofol (p < 0.05). It is observed that the anesthetic couple did not change the hematocrite value (tab. 3).
Due to 2 induction apneas encountered during propofol administration, respiratory rates could be as-sessed over 10 animals, and due to problems during blood collections of these animals the plasma
electro-lyte and biochemical parameters could also be asses-sed over 10 animals. In regard of the patients safety, the chosen anesthesia should possess the least effects on the cardiavasvular and respiratory systems of the animals. In this study, slow intravenous injection of propofol allowed a fast anesthesia induction without excitation, during this period all the cases were intu-bated free of complication. Following intubation, the animals were connected to the anesthesia machine and had a successful awakening period. It is believed that the decrease of heart rate following propofol applica-tion caused a physiological decrease in renal blood flow, in turn causing a decrease in plasma P+ level.
Considering the short interval between propofol and sevoflurane applications, it is estimated that the stati-stical increase of plasma P+ level following
sevoflura-ne (p < 0.05) is related to the decreased renal blood flow caused predoninatly by propofol (tab. 1).
Increased LDH activity in rabbits is a feature of liver disorder, connected with the damage at the hepa-tocytes, and the increase in AST levels is indicative for liver, heart and skeleton muscle injuries (7). These parameters did not show any significant changes in our study, therefore the anesthetics used in the study did not cause anesthetic related hepatic toxicity.
ALT shows little specificity for liver in the rabbit, for it is also an enzyme present in the heart muscle (7). We observed a decrease activating of ALT in plasma (p < 0.05) following sevoflurane anesthesia. Although in the literature a decrease in ALT was not considered as an important finding (3), it is believed that this ob-servation should be taken into account for sevoflurane anesthetized rabbits (tab. 2).
One of the reasons for plasma GGT increase is due to liver disorders in rabbits (7). Compared to the con-trol values plasma GGT levels showed a significant elevation (p < 0.05) following propofol application, and study maybe related to the action of propofol on the liver.
Isles et al. (16), stated that creatinine concentrations are more trustworthy compared to urea in rabbits. The increase of plasma creatinine levels (p < 0.05) fol-lowing propofol administration has been attributed to the hypotension also occurring at the same time. These results are in accordance with results of other studies (12, 13). Subsequent to propofol application, a drop in the heart rate was observed in all cases, what is consistent with results of other studies indi-cating that propofol may inhibit normal sinus rhythm (19, 21). Compared to propofol effect, heart rate did not show any significant chan-ges during sevoflurane inhalation. This could be attributed to the cardiac stability of this agent, which is in accordance with other stu-dies (11, 23). The most common complication encountered with propofol is related to its application dose and rate. It was observed that propofol caused a respiratory depression Tab. 2. Plasma liver enzymes and urea and creatinine values
(n = 10; x ± SE) s e m y z n e r e v i L (C1o5nmrtoinl) P(0rompoinfo)l Se(v1o5lfmuriann)e e n i n it a e r C ) l d / g m ( 0.920 0.057 1.040* 0.071 1.060 0.074 ) l d / g m ( a e r U 51.44 3.14 51.78 2.99 46.78 5.45 ) L / U I( T S A 32.40 3.46 33.30 3.84 32.20 3.49 ) L / U I( T L A 28.10 2.92 26.60 2.47 23.60* 2.20 ) L / U I( P L A 59.20 16.67 58.70 16.08 56.50 15.701 ) L / U I( T G G 12.00 3.08 18.0* 13.71 20.00 3.03 ) L / U I( H D L 87.10 13.46 127.40 15.97 103.70 16.181 Explanation: as in tab. 1.
Tab. 3. Heart and respiratory rates, hematocrite and body temperature values (x ± SE) l a c i g o l o i s y h P s r e t e m a r a p n (C1o5nmrtoinl) P(r0ompoifno)l Se(1vo5lfmurina)ne e t a r tr a e H 12 273.00 6.53 218.33* 13.06 226.67 7.23 ) % ( T C H 12 40.955 1.226 40.955 1.229 40.045 1.317 e t a r y r o t a ri p s e R 10 112.10 13.94 57.20* 6.82 46.20* 4.01 ( e r u t a r e p m e t y d o B ° )C 12 138.78 10.16 38.70* 0.15 38.36* 0.09 Explanation: as in tab. 1.
Medycyna Wet. 2006, 62 (12) 1386
(p <0.001). The two cases of induction apnea encoun-tered in this study are related to the fast IV injection of the drug as was suggested in other publications (1, 14, 24).
It was stated in other study that propofol infusion for 8 hours caused a decrease in body temperature (15, 17). In our study body temperature values in control and propofol administered rabbits did not show any difference. This could be explained by the relatively short period of the drugs administration. On the other hand, body temperature values following sevoflurane inhalation showed a decrease (p < 0.05) when compa-red to values obtained following propofol application. This observation is in accord with results of other studies stating that sevoflurane may lead to a decrease in body temperature (15, 17). It was also suggested that hypothermia may lead to a decrease in blood plasma K+ ion levels (4). In this study the decrease
observed in plasma K+ levels succeeding to
sevolfura-ne inhalation is related to the simultasevolfura-neous hypother-mia (p < 0.05). Moreover, the decrease of plasma Mg++
level (p < 0.05) was accompanied K+ ion decrease
during anesthesia (2).
Propofol and sevoflurane combination has not been used in previous studies in rabbits. This study demon-strates the effects of propofol and sevoflurane com-bination on heart and respiratory rate, body temperature, plasma electrolyte levels, liver enzymes, some renal and blood parameters. Further experiment should be conducted in order to understand better their effects on liver and renal functions.
The animals had a reliable and controlled anesthe-sia with the propofol-sevoflurane combination. How-ever, it should be taken into consideration that this com-bination may impair the electrolyte balance and cause respiratory depression. Thus it has been concluded that a diligent monitorization and an electrolyte support is essential during the time of anesthesia.
References
1.Aeschbacher G., Webb A. I.: Propofol in rabbits. 2. Long-term anesthesia. Lab. Anim. Sci. 1993, 43, 328-335.
2.Basar K.: Endokrin, Metabolik ve Lipid Bozukluklarý ve Testleri. Veteriner Klinik Laboratuvar Teshis (in Turkish) 2000, 11, 416-487.
3.Baºar K.: Klinik Enzimoloji. Veteriner Klinik Laboratuvar Teshis (in Tur-kish) 2000, 6, 179-201.
4.Bernard S. A., Jones B. M., Buist M.: Experience with prolonged induced hypothermia in severe head injury. Crit Care. 1999, 3, 167-172.
5.Borkowski R., Karas A. Z.: Sedation and anesthesia of pet rabbits. Clin. Tech. Small Anim. Pract. 1999, 14, 44-49.
6.Bufalari A., Miller S. M., Giannoni C., Short C. E.: The use of propofol as an induction agent for halothane and isoflurane in dogs. J. Am. Anim. Hosp. Assoc. 1998, 34, 84-91.
7.Bush B. M.: Plasma biochemistry (5. Nutrients and metabolites/6. Enzymes), [in:] Interpretation of Laboratory Results for Small Animal Clinicians. Blacwell Scientific Publications, Oxford 1991, p. 221-347.
8.Clutton E.: Anaesthetic Equipment, [in:] Seymour C., Gleed R. (eds.): Manual of Small Animal Anaesthesia and Analgesia. BSAVA, Cheltenhan 1999, 19-41.
9.Flecknell P. A., Cruz I. J., Liles J. H., Whelan G.: Induction of anaesthesia with halothane and isoflurane in the rabbit: A comparison of the use of a face-mask or an anaesthetic chamber. Lab. Anim. 1996, 30, 67-74. 10.Flecknell P.: Rabbits, Rodents and Ferrets, [in:] Seymour C., Gleed R. (eds.):
Manual of Small Animal Anaesthesia and Analgesia. BSAVA, Cheltenhan 1999, 295-304.
11.Flecknell P. A., Roughan J. V., Hedenqvist P.: Induction of anaesthesia with sevoflurane and isoflurane in the rabbit. Lab. Anim. 1999, 33, 41-46. 12.Gil A. G., Illera J. C., Silvan G., Illera M.: Effects of the anaesthetic/
tranquillizer treatments on selected plasma biochemical parameters in NZW rabbits. Lab. Anim. 2003, 37, 155-161.
13.Gil A. G., Silvan G., Illera M., Illera J. C.: The effects of anesthesia on the clinical chemistry of New Zealand white rabbits. Comtemp. Top. Lab. Anim. Sci. 2004, 43, 24-28.
14.Henke J., Koch M., Brill T., Bolkart B., Janczewski M., Erhardt W.: Isoflura-ne aIsoflura-nesthesia in rabbits in a closed aIsoflura-nesthetic system. Tierarzt Prax. 1996, 24, 604-609.
15.Ikeda T., Sessler D. I., Kikura M., Kazama T., Ikeda K., Sato S.: Less core hypothermia when anesthesia is induced with inhaled sevoflurane than with intravenous propofol. Anesth. Analg. 1999, 88, 921-924.
16.Isles C. G., Paterson J. R.: Serum creatinine and urea: Make the most of these simple test. Br. J. Hosp. Med. 1996, 55, 513-516.
17.Iwata T., Inoue S., Kawaguchi M., Takahashi M., Sakamoto T., Kitaguchi K., Furuya H., Sakaki T.: Comparison of the effects of sevoflurane and propofol on cooling and rewarming during deliberate mild hipothermia for neuro-surgery. Br. J. Anaesth. 2003, 90, 32-38.
18.Kato R., Foëx P.: Myocardial protection by anesthetic agents against ische-mia-reperfusion injury: an update for anesthesiologists. Can. J. Anesth. 2002, 49, 777-791.
19.Ma D., Chakrabarti M. K., Whitwam J. G.: Propofol, bradycardia and Bezold-Jarisch reflex in rabbits. Br. J. Anaesth. 1999, 82, 412-417. 20.Mustola S. T., Rorarius M. G., Baer G. A., Rosenberg P., Seppala T.,
Har-moinen A.: Potency of propofol, thiopentone and ketamine at various end-points in New Zealand White Rabbits. Lab. Anim. 2000, 34, 36-45. 21.Oztekin S., Kalkan S., Ozzeybek D., Tuncok Y., Guven H., Elar Z.: The
effects of propofol on normal and hypercholesterolemic isolated rabbit heart. Gen. Pharmacol. 2000, 35, 65-70.
22.Piriou V., Chiari P., Lhuillier F., Bastien O., Loufoua J., Raisky O., David J. S., Ovize M., Lehot J. J.: Pharmacological preconditioning: compa-rison of desflurane, sevoflurane, isoflurane and halothane in rabbit myo-cardium. Br. J. Anaesth. 2002, 89, 486-491.
23.Preckel B., Schlack W., Comfere T., Obal D., Barthel H., Thamer V.: Effects of enflurane, isoflurane, sevoflurane and desflurane on reperfusion in jury after regional myocardial ischaemia in the rabbit heart in vivo. Br. J. Anaesth. 1998, 81, 905-912.
24.Short C. E., Bufalari A.: Propofol anesthesia. Vet. Clin. North Am. Small Anim. Pract. 1999, 29, 747-778.
25.Story D. A., Poustie S., Liu G., McNicol P. L.: Changes in plasma creatinine concentration after cardiac anesthesia with isoflurane, propofol, or sevoflu-rane. Anesthesiology 2001, 95, 842-848.
26.Thurmon C. J., Tranquilli J. W., Benson J. G.: Anesthesia of wild, exotic and laboratory animals, [in:] Lump&Jones Veterinary Anesthesia. Williams& Wilkins, Baltimore 1996, p. 686-735.
27.Xu H., Aibiki M., Yokono S., Ogli K.: Dose-dependent effects of propofol on renal sympathetic nevre activity, blood pressure and heart rate in urethane--anesthetized rabbits. Eur. J. Pharmacol. 2000, 387, 79-85.
Authors address: Dr. Ozlem Guzel DVM, PhD, Surgery Department, Faculty of Veterinary Medicine, Istanbul University, 34320, Avcilar-Istan-bul/Turkey; e-mail: drozlemguzel@gmail.com, droguzel@istanbul.edu.tr
