Effects of high-volume, rapid-fluid therapy on cardiovascular function and hematological values during isoflurane-induced hypotension in healthy dogs

The objective of this study was to determine the effects of the administration of a high volume of isotonic crystalloid at a rapid rate on cardiovascular function in normovolemic, isoflurane-anesthetized dogs during induced hypotension.Using a prospective study, 6 adult dogs were induced to general anesthesia and cardiovascular and hematological values were measured while the dogs were maintained at 3 hemodynamic states: first during light anesthesia with 1.3% end-tidal isoflurane (ETI); then during a hypotensive state induced by deep anesthesia with 3% ETI for 45 min while administered 1 mL/kg body weight (BW) per minute of isotonic fluids; and then decreased to 1.6% ETI while receiving 1 mL/kg BW per minute of fluids for 15 min. End-tidal isoflurane (ETI) at 3.0 ± 0.2% decreased arterial blood pressure (ABP), cardiac index (CI), and stroke volume index (SVI), and increased stroke volume variation (SVV) and central venous pressure (CVP). Fluid administration during 3% ETI decreased only SVV and systemic vascular resistance index (SVRI), while CVP increased progressively. Decreasing ETI to 1.6 ± 0.1% returned ABP and SVI to baseline (ETI 1.3 ± 0.1%), while CI and heart rate increased and SVV decreased. There was significant progressive clinical hemodilution of hemoglobin (Hb), packed cell volume (PCV), total protein (TP), colloid osmotic pressure (COP), arterial oxygen content (CaO₂), and central-venous oxygen content (CcvO₂).High-volume, rapid-rate administration of an isotonic crystalloid was ineffective in counteracting isoflurane-induced hypotension in normovolemic dogs at a deep plane of anesthesia. Cardiovascular function improved only when anesthetic depth was reduced. Excessive hemodilution and its adverse consequences should be considered when a high volume of crystalloid is administered at a rapid rate.     

Prior determination of baseline minimum alveolar concentration (MAC) of isoflurane does not influence the effect of ketamine on MAC in rabbits

The objective of this study was to compare the effect on the minimum alveolar concentration (MAC) of isoflurane when ketamine was administered either after or without prior determination of the baseline MAC of isoflurane in rabbits. Using a prospective randomized crossover study, 8 adult, female New Zealand rabbits were allocated to 2 treatment groups. Anesthesia was induced and maintained with isoflurane. Group 1 (same-day determination) had the MAC-sparing effect of ketamine [1 mg/kg bodyweight (BW) bolus followed by a constant rate infusion (CRI) of 40 μg/kg BW per min, given by intravenous (IV)], which was determined after the baseline MAC of isoflurane was determined beforehand. A third MAC determination was started 30 min after stopping the CRI. Group 2 (separate-day determination) had the MAC-sparing effect of ketamine determined without previous determination of the baseline MAC of isoflurane. A second MAC determination was started 30 min after stopping the CRI. In group 1, the MAC of isoflurane (2.15 ± 0.09%) was significantly decreased by ketamine (1.63 ± 0.07%). After stopping the CRI, the MAC was significantly less (2.04 ± 0.11%) than the baseline MAC of isoflurane and significantly greater than the MAC during the CRI. In group 2, ketamine decreased isoflurane MAC (1.53 ± 0.22%) and the MAC increased significantly (1.94 ± 0.25%) after stopping the CRI. Minimum alveolar concentration (MAC) values did not differ significantly between the groups either during ketamine administration or after stopping ketamine. Under the study conditions, prior determination of the baseline isoflurane MAC did not alter the effect of ketamine on MAC. Both methods of determining MAC seemed to be valid for research purposes.     

Determination of cardiac output in neonatal foals by ultrasound velocity dilution and its comparison to the lithium dilution method

Objective – To compare cardiac output (CO) measured by use of lithium dilution (LiDCO) and ultrasound velocity dilution (UDCO) in conditions of high, intermediate, and low CO in anesthetized foals.
Design – Original prospective study.
Setting – University teaching hospital.
Animals – Six foals 1–3 days of age (38–45 kg).
Interventions – Neonatal foals were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases, and CO. The CO was measured by use of LiDCO and UDCO techniques. Measurements were obtained from each foal at baseline and during low, intermediate, and high CO states. Measurements were converted to cardiac index (cardiac index=CO/body weight) values for statistical analysis. Agreement between the 2 methods was determined using Bland and Altman analysis and concordance correlation coefficients.
Measurements and Main Results – LiDCO determinations of CO ranged between 4.0 and 14.0 L/min resulting in cardiac index ranging between 75.5 and 310 mL/kg/min. There was no significant effect of blood pressure variation on bias or relative bias ( P =0.62 and 0.93, respectively). The mean bias and relative bias of UDCO (±SD) compared with LiDCO were −20.1±39.2 mL/kg/min and −7.7±23.4%, respectively. Concordance correlation coefficient between LiDCO and UDCO was 0.833.
Conclusions – When compared with LiDCO, the UDCO technique has acceptable clinical utility for measuring CO in healthy anesthetized newborn foals.     

Effect of anesthesia duration on the quality of recovery in horses undergoing elective and emergency surgeries using the same anesthetic protocol

The objective of this study was to investigate the effect of anesthesia duration on the quality of recovery in horses. The medical records of horses that were anesthetized and underwent surgery for elective and emergency soft tissue and orthopedic conditions from 2013 to 2019 were reviewed. Horses included in the study (N = 305) fulfilled the following requirements: all had the same premedication/induction protocol and the same balanced anesthesia for maintenance and were anesthetized by the same, experienced Board-certified anesthesiologist. A standardized anesthetic recovery score was completed for all horses to evaluate their recovery and the following interactions were assessed: age, body weight, breed, sex, American Society of Anesthesiologists status, type of surgical procedure, occurrence of hypotension, use of dobutamine, number of additional doses of xylazine/ketamine after isoflurane discontinuation, anesthesia duration, post-anesthetic sedation, and end-tidal isoflurane concentration during maintenance and at the time of transfer to the recovery room. These interactions were assessed based on the quality of recovery score using logistic regression. Duration of anesthesia (P = 0.021) and age (P = 0.003) negatively affected the quality of recovery. The odds of a worse recovery score were increased by 1.20-fold (1.03, 1.41; lower and upper limits) for every additional 30 min of anesthesia duration, while the odds of a worse recovery score were increased by 1.09-fold (1.03, 1.16) for every additional 1 y of age. In conclusion, the results of this retrospective study indicate that increasing the anesthesia duration negatively affects the quality of recovery in horses undergoing routine and emergency surgical procedures.     

Age-related mechanisms of propanil tolerance in Jungle-rice,Echinochloa colona

Uptake and metabolism of propanil were measured in both susceptible (S) and resistant (R) biotypes of Jungle-rice, Echinochloa colona (L.) link at different growth stages. Results showed that there was no significant difference in uptake between S and R biotypes of E. colona at any given growth stage, but that uptake was significantly reduced at older plant growth stages in all biotypes studied. Metabolism of propanil was more rapid in R biotypes than in S biotypes at all growth stages studied. Specific and total aryl acylamidase activity, responsible for the first stage of propanil metabolism, was higher in R biotypes than in S at all growth stages, but declined to about 50% of the maximum at older growth stages, confirming the importance of this enzyme in conferring resistance to this herbicide. The area of necrosis that developed around a single drop of propanil deposited on the adaxial leaf surface was used to assess the degree of propanil resistance; it was found that resistance increased at older E. colona growth stages in contrast to the rate of propanil metabolism and amidase activity. Treatment of leaves with the amidase inhibitors, carbaryl or piperophos, simultaneously with propanil, caused a decrease in resistance at growth stages where amidase activity was greatest. This treatment was less effective at older growth stages. These results show that, in E. colona, propanil metabolism is important for conferring resistance in younger plants (four-six-leaf stage). It is suggested that restricted uptake confers resistance in older plants.     

Association between elevated activity of aryl acylamidase and propanil resistance in Jungle-rice,Echinochloa colona

Aryl acylamidase (aryl-acylamine amidohydrolase, EC 3.5.1.13) activity has been measured in crude extracts from leaves of propanil-susceptible (S) and propanil-resistant (R) biotypes of the grass weed. Echinochloa colona (L.) Link from Columbia. Both specific and total amidase activity increased with plant age up to 15 days (four-leaf stage), then decreased beyond 20 days to about 50% of the maximum at 36 days in both R and S E. colona biotypes. Specific activity with propanil in the R biotype was about 80% of that obtained for rice (Oryza sativa L.), compared to 25% in the susceptible biotype. The specific activity of the propanil amidase was three-fold higher in the R biotype than in the S. Partially purified amidase extracts from rice and both S and R biotypes of E. colona were compared biochemically. Both rice and E. colona amidases had a pH optimum of 7.5 and native relative molecular masses, estimated by gel filtration, of 179 000 and 181 000, respectively. Out of six substrates tested, three produced appreciable activity (propanil, 4-chloroacetanilide and acetanilide) in both rice and E. colona. Michaelis constants showed that the rice amidase had a higher affinity for propanil (0.36 mM) than had the E. colona enzyme (1.1 mM). Carbamates and organo-phosphorus pesticides were shown to inhibit amidase activity in partially purified rice and E. colona extracts. Additional preliminary data have implicated peroxidase in the next step of propanil metabolism in vitro. These data demonstrate that increased aryl acylamidase activity contributes to resistance to the herbicide propanil in E. colona weeds. Also, a biochemical comparison of purified aryl acylamidases from S and R biotypes of E. colona is presented for the first time.     

Cardiac output measurement by partial carbon dioxide rebreathing, 2-dimensional echocardiography, and lithium-dilution method in anesthetized neonatal foals

The objective of this study was to assess 2 noninvasive methods of measuring cardiac output (CO) in neonatal foals by comparing results to that of the lithium-dilution method. Ten neonatal foals were anesthetized and CO was manipulated by varying the depth of anesthesia and infusion of dobutamine. Concurrent CO measurements were obtained by lithium dilution (reference method), partial carbon dioxide (CO2) rebreathing, volumetric echocardiography (cubic, Teichholz, Bullet, area-length, and single and biplane modified Simpson formulas), and transthoracic Doppler echocardiography. Thirty pairs of lithium-dilution/noninvasive CO measurements were taken from the 10 foals. For each method, relative bias was calculated as a percentage of the average CO. Lithium determinations of CO ranged between 3.09 and 1 1.1 L/min (mean +/- SD = 6.39 +/- 2.1 L/min), resulting in cardiac indices ranging between 79.0 and 209 mL/kg/min (mean +/- SD = 131 +/- 35.9 mL/kg/min). Relative bias of Doppler echocardiography significantly increased (P < .05), whereas that of partial CO2 rebreathing significantly decreased (P = .03) with increasing CO. Other methods were not influenced by the level of CO. Among methods not influenced by the level of CO, relative bias of the Bullet method (-4.2 +/- 20.9%; limits of agreement -45.2 to 36.7%) was significantly lower (P < .05) than that of each of the other noninvasive methods evaluated. Volumetric echocardiography using the Bullet method provides an accurate and noninvasive estimate of CO in anesthetized neonatal foals and warrants investigation in critically ill conscious foals.     

Comparison of non-invasive cardiac output measurement by partial carbon dioxide rebreathing with the lithium dilution method in anesthetized dogs

Objective: To compare the partial CO₂ rebreathing method (non‐invasive cardiac output [NICO]) and the lithium dilution method (lithium dilution cardiac output [LiDCO]) for cardiac output (CO) measurement in anesthetized dogs. Design: Prospective study. Setting: College of Veterinary Medicine, University of Florida. Animals: Six adult dogs (weight range 22–25.4 kg). Interventions: All animals were instrumented for CO determinations using the LiDCO and NICO methods. Direct blood pressure, heart rate, arterial blood gases, end‐tidal isoflurane (ETI), and CO₂ concentrations were monitored throughout the study. CO was manipulated with dobutamine and isoflurane to allow for intermediate, low, and high CO determinations in that order using LiDCO and NICO. Measurements and main results: A 1.5% ETI produced the intermediate rate of CO, a constant‐rate infusion of dobutamine (1–4 μg/kg/min) and 1.1% ETI, the highest rate, and 2.5–3% ETI, the lowest rate. Measurements were obtained in duplicate or triplicate for the LiDCO and continuously for the NICO method after achieving a stable hemodynamic plane for at least 15 minutes at each level of CO, allowing 5 minutes between measurements. Forty‐seven comparisons were determined. The correlation coefficient (r) between the 2 methods was 0.888 for all determinations. The mean LiDCO and NICO from 47 measurements were 155.9±78.7 mL/kg/min (range, 49.6–303.2) and 146.6±62.9 mL/kg/min (50–290.3), respectively. The bias between LiDCO and NICO estimations was 9.3 (?60.7 to +79.4) mL/kg/min (mean and 95% confidence interval). The mean (mL/kg/min) of the differences of LiDCO–NICO was 1.11 × NICO. The relative error was 2.4±24.7%. As CO increased, the relative difference between the methods also increased. Conclusions: The NICO is a viable non‐invasive method for CO determination in the dog and compares well with the LiDCO.     

The perinatal development of the gastrointestinal tract in piglets can be modified by supplementation of sow diet with bioactive substances

Dietary bioactive substances involving taurine, l-carnitine, polyunsaturated fatty acids, flavonoids and antioxidants were shown to control the perinatal development in mammals. A blend of bioactive substances was used to supplement the diet of sows according to the optimal needs of their offspring. Our study aimed to examine the development of gastrointestinal tract in their offspring as compared to the offspring from control sows fed with standard diet. The supplemented diet was given from the gestation day 80 until the end of lactation period. One piglet from each litter was sacrificed on postnatal days 1 (i.e., unsuckling neonates), 2, 4, 7, 14, and 28 for tissue sampling. At birth, the stomach relative weight was larger in the supplemented group, and the small intestine relative weight was smaller as compared to control. These differences disappeared within 1–4 postnatal days. The stomach weight was larger at postnatal day 28 in the supplemented group as compared to control. Gastric protein content and the proteolytic activity in the offspring of the supplemented sows showed after birth a tendency to increase as compared to control, though the differences disappeared after the fourth postnatal day. In conclusion, the supplementation of sow diet with dietary bioactive substances affected primarily the prenatal development of the stomach and small intestine in their offspring.