André Escobar

Comparison of analgesia provided by lidocaine, lidocaine-morphine or lidocaine-tramadol delivered epidurally in dogs following orchiectomy

OBJECTIVE To evaluate and compare the postoperative analgesia provided by epidural lidocaine, lidocaine/morphine or lidocaine/tramadol in dogs following elective orchiectomy. STUDY DESIGN Prospective experimental trial. ANIMALS Thirty-six mongrel dogs aged 2-8 years old, weighing 6.6-22 kg. METHODS The dogs received 6.0 mg kg(-1) of lidocaine combined with 1.0 mg kg(-1) of tramadol, 0.1 mg kg(-1) of morphine or 0.01 mL kg(-1) of 0.9% NaCl epidurally. Analgesia was assessed at 4, 8, 12, 18 and 24 hours (T4, T8, T12 and T24) after the offset of lidocaine using a scale composed of physiologic and behavioral parameters. Rescue analgesia with morphine (0.2 mg kg(-1) , IM) was performed if the evaluation score exceeded 10 during the postoperative period. The scores over time were analyzed using the Friedmans two-way analysis of variance and the comparison between groups was made by the Kruskal-Wallis test with statistical significances accepted if p ≤ 0.05. RESULTS There were no differences in the pain scores between the morphine and tramadol groups over time and no rescue analgesia was administered. In the NaCl group, rescue analgesia was needed at T4, T8 and T12. Within this group, the final evaluation times (T18 and T24) had lower pain scores than at T4, T8 and T12. CONCLUSIONS AND CLINICAL RELEVANCE Epidural lidocaine/tramadol provided an analgesic effect comparable to that of epidural lidocaine/morphine during the first 12 hours after surgical castration without substantial side effects, suggesting that tramadol may be an effective postoperative analgesic in dogs submitted to this surgical procedure.

Effects of butorphanol on the minimum anesthetic concentration for sevoflurane in guineafowl (Numida meleagris)

OBJECTIVE To determine the minimum anesthetic concentration (MAC) for sevoflurane and measure the dose and temporal effects of butorphanol on the MAC for sevoflurane in guineafowl. ANIMALS 10 healthy adult guineafowl (Numida meleagris). PROCEDURES Each bird was anesthetized with sevoflurane, and a standard bracketing method was used to measure the MAC in response to a noxious electrical stimulus. Subsequently, conditions were adjusted so that each bird was anesthetized with sevoflurane at a fraction of its respective MAC (eg, 0.7 times the MAC for that bird). Butorphanol tartrate (2 mg/kg, IV) was administered, and a noxious stimulus was applied every 15 minutes until the bird moved in response. The reduction in MAC was estimated with logistic regression by use of a standard quantal method. After an interval of ≥ 1 week, the MAC reduction experiment was repeated with an increased butorphanol dosage (4 mg/kg). RESULTS Individual mean ± SE MAC for sevoflurane was 2.9 ± 0.1%. At 15 minutes after administration of 2 mg of butorphanol/kg, estimated reduction in the MAC for sevoflurane was 9 ± 3%. At 15 and 30 minutes after administration of 4 mg of butorphanol/kg, estimated reduction in the MAC for sevoflurane was 21 ± 4% and 11 ± 8%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE In guineafowl, the MAC for sevoflurane was similar to values reported for other species. Increasing the butorphanol dosage decreased the MAC for sevoflurane, but the effect was small and of short duration for dosages up to 4 mg/kg.

Anesthetic induction with guaifenesin and propofol in adult horses

OBJECTIVE To evaluate whether guaifenesin can prevent adverse anesthetic induction events caused by propofol and whether a guaifenesin-propofol induction combination has brief cardiovascular effects commensurate with rapid drug washout. ANIMALS 8 healthy adult horses. PROCEDURES Guaifenesin was administered IV for 3 minutes followed by IV injection of a bolus of propofol (2 mg/kg). Additional propofol was administered if purposeful movement was detected. Anesthesia was maintained for 2 hours with isoflurane or sevoflurane at 1.2 times the minimum alveolar concentration with controlled normocapnic ventilation. Normotension was maintained via a dobutamine infusion. Plasma concentrations of propofol and guaifenesin were measured every 30 minutes. RESULTS Mean ± SD guaifenesin and propofol doses inducing anesthesia in half of the horses were 73 ± 18 mg/kg and 2.2 ± 0.3 mg/kg, respectively. No adverse anesthetic induction events were observed. By 70 minutes, there was no significant temporal change in the dobutamine infusion rate required to maintain normotension for horses anesthetized with isoflurane or sevoflurane. Mean plasma guaifenesin concentrations were 122 ± 30 μM, 101 ± 33 μM, 93 ± 28 μM, and 80 ± 24 μM at 30, 60, 90, and 120 minutes after anesthetic induction, respectively. All plasma propofol concentrations were below the limit of quantitation. CONCLUSIONS AND CLINICAL RELEVANCE Guaifenesin prevented adverse anesthetic induction events caused by propofol. Guaifenesin (90 mg/kg) followed by propofol (3 mg/kg) should be sufficient to immobilize > 99% of calm healthy adult horses. Anesthetic drug washout was rapid, and there was no change in inotrope requirements after anesthesia for 70 minutes.

Effects of meloxicam administered by different routes to control experimental uveitis in dogs.

Efficacy of meloxicam, administered by different routes was studied in experimental uveitis in dogs. Anterior chamber paracenteses was accomplished at two different moments (M0 and M1), with a five hour interval among them. At M0 and M1, 0.2mL of aqueous humor was collected and total protein and prostaglandin E2 (PGE2) quantitation was determined. Four groups were formed (n=5), which received meloxicam at the end of M0. by the following routes: subcutaneous (GIm), subconjunctival (GII), and topical (GIII). A fourth group that received no treatment was instituted (Control). Conjunctival histopathology of the GII was performed. Results were evaluated statistically (P≤0.05). In all groups, protein and PGE2 values enhanced significantly in M1. Protein and PGE2 values did not change significantly between groups at M1. Inflammatory exudate of acute character and mild hemorrhage were seen at histopathology, after meloxicam administration. Meloxicam were unable to inhibit PGE2 synthesis and the protein influx to the anterior chamber by any of the tested routes.

CARDIORESPIRATORY EFFECTS OF ISOFLURANE ANESTHESIA IN CRESTED CARACARAS (CARACARA PLANCUS)

Abstract To evaluate the cardiorespiratory changes induced by isoflurane (ISO) anesthesia in the crested caracara (Caracara plancus), eight crested caracaras that weighed 1.0 kg (range 0.9–1.1 kg) were the subjects for the study. The birds were anesthetized by face mask with ISO for brachial artery catheterization. After recovery, anesthesia was re-induced and maintained with ISO with spontaneous ventilation. Electrocardiography, direct systolic arterial blood pressure (SAP), diastolic arterial blood pressure (DAP), mean arterial blood pressure (MAP), respiratory rate (RR), end-tidal carbon dioxide (PETCO2), and cloacal temperature (T°C) were measured before induction (baseline, under physical restraint) and after 5, 10, 15, 20, 25, 30, 35, and 40 min of ISO anesthesia. Arterial blood samples were collected for blood gas analysis at baseline, 10, 25, and 40 min. No cardiac arrhythmias were observed in the present study. RR, SAP, DAP, MAP, T°C and pH decreased from baseline values, whereas arterial partial pressures of oxygen and carbon dioxide, bicarbonate concentration, and PETCO2 were significantly higher than baseline. Apnea was not observed in any bird. ISO anesthesia is suitable for use in healthy members of this species despite the moderate cardiovascular and respiratory depression produced.

Effect of passive pneumoperitoneum on oesophageal pressure, cardiovascular parameters and blood gas analysis in horses

REASONS FOR PERFORMING STUDY Standing surgical procedures are being employed to an ever-greater extent in horses. Pneumoperitoneum during abdominal surgery might adversely affect the work of breathing. OBJECTIVES To determine whether development of pneumoperitoneum during abdominal surgery adversely influences the work of breathing. METHODS Eight healthy mature horses were equipped with carotid artery and thoracic vena cava catheters and an intraluminal manometry system. The following measurements were obtained before and at +5, +10, +15 and +30 min following establishment of pneumoperitoneum by paralumbar puncture using an 8 gauge needle: vital signs, oesophageal pressure, gastric pressure, arterial and central venous blood pressures, and arterial and mixed venous blood gas analyses. RESULTS Significant changes in oesophageal pressure, central venous pressure and results of arterial and mixed venous blood gas analysis were not detected. Arterial diastolic and mean pressures and rectal temperature increased slightly (P ≤ 0.05). CONCLUSIONS Passive pneumoperitoneum did not adversely affect breathing mechanics or haemodynamic variables under experimental conditions. Changes in arterial pressure could have occurred as a response to the passive pneumoperitoneum or be related to handling stress. Subtle variations in rectal temperature were not clinically relevant and likely resulted from stress associated with restraint. POTENTIAL RELEVANCE It is unlikely that mature horses will develop signs of respiratory difficulty as a result of the development of passive pneumoperitoneum during standing laparoscopy.

Effects of Methadone on the Minimum Anesthetic Concentration of Isoflurane, and Its Effects on Heart Rate, Blood Pressure and Ventilation during Isoflurane Anesthesia in Hens (Gallus gallus domesticus).

The aim of this study was to measure the temporal effects of intramuscular methadone administration on the minimum anesthetic concentration (MAC) of isoflurane in hens, and to evaluate the effects of the isoflurane-methadone combination on heart rate and rhythm, blood pressure and ventilation. Thirteen healthy adult hens weighing 1.7 ± 0.2 kg were used. The MAC of isoflurane was determined in each individual using the bracketing method. Subsequently, the reduction in isoflurane MAC produced by methadone (3 or 6 mg kg-1, IM) was determined by the up-and-down method. Stimulation was applied at 15 and 30 minutes, and at 45 minutes if the bird had not moved at 30 minutes. Isoflurane MAC reduction was calculated at each time point using logistic regression. After a washout period, birds were anesthetized with isoflurane and methadone, 6 mg kg-1 IM was administered. Heart rate and rhythm, respiratory rate, blood gas values and invasive blood pressure were measured at 1.0 and 0.7 isoflurane MAC, and during 45 minutes after administration of methadone once birds were anesthetized with 0.7 isoflurane MAC. Fifteen minutes after administration of 3 mg kg-1 of methadone, isoflurane MAC was reduced by 2 (-9 to 13)% [logistic regression estimate (95% Wald confidence interval)]. Administration of 6 mg kg-1 of methadone decreased isoflurane MAC by 29 (11 to 46)%, 27 (-3 to 56)% and 10 (-8 to 28)% after 15, 30 and 45 minutes, respectively. Methadone (6 mg kg-1) induced atrioventricular block in three animals and ventricular premature contractions in two. Methadone caused an increase in arterial blood pressure and arterial partial pressure of carbon dioxide, while heart rate and pH decreased. Methadone, 6 mg kg-1 IM significantly reduced isoflurane MAC by 30% in hens 15 minutes after administration. At this dose, methadone caused mild respiratory acidosis and increase in systemic blood pressure.

Use of gastric balloon manometry for estimation of intra-abdominal pressure in horses

REASONS FOR PERFORMING STUDY Standing laparoscopic procedures, facilitated by abdominal insufflation with carbon dioxide, are being employed to an increasingly greater extent in horses. However, a sustained increase in abdominal pressure may be life-threatening. A practical method for intra-abdominal pressure (IAP) assessment is imperative. Although indirect methods for estimating IAP have been extensively studied in man, little work has been performed in veterinary medicine. OBJECTIVES To investigate the utility of gastric manometry for purposes of evaluating IAP in horses. METHODS Gastric pressure (P(ga) ) was estimated by balloon manometry in 8 healthy, mature horses, before and during a 30 min passive pneumoperitoneum induced by right paralumbar puncture. The balloon manometer was positioned within the gastric lumen and inflated using 2 separate volumes of air: 10 and 50 ml. P(ga) Gastric pressure was determined at baseline (0) and 5, 15 and 30 min after induction of passive pneumoperitoneum. Intra-abdominal pressure was measured directly by right paralumbar puncture using an 8 gauge needle at baseline and immediately following establishment of passive pneumoperitoneum. RESULTS Baseline IAP values were negative and increased (P≤0.05) during development of passive pneumoperitoneum. However, recorded P(ga) measurements for both inflation volumes were positive before (baseline) and during the course of the passive pneumoperitoneum. Measured P(ga) values did not correlate with IAP at any time. CONCLUSIONS AND POTENTIAL RELEVANCE Our results suggest that the indirect method used in human patients for estimating IAP by P(ga) is not applicable for horses.

Fluorescence evaluations for porphyrin formation during topical PDT using ALA and methyl-ALA mixtures in pig skin models

BACKGROUND Photodynamic Therapy (PDT) using Aminolevulinic acid (ALA) and derivative molecules as topical medication and as a precursor of protoporphyrin (PPIX), is limited due to low permeation through skin or efficiency in porphyrin production. This behavior affects the production and homogeneity of PPIX distribution on superficial skin and in the deeper skin layers. Many authors propose alternatives to solve this such as, modification in the ALA and derivativemolecules, modifying the chemical properties of emulsion external phase or incorporating a delivery system to the emulsion. The goal of this study is to discuss what proportion of ALA and Methyl aminolevulinate (MAL) on mixtures increase the amount and uniformity of PPIX formation at superficial skin by fluorescence evaluations. METHODS The study was conducted in vivo using a pig skin model. PPIX production was monitored using fluorescence spectroscopy and widefield fluorescence imaging on skin surface. 20% of ALA and MAL cream were done mixing the following proportions: ALA, M2 (80% ALA-20% MAL), M3 (60% ALA-40% MAL), M4 (50% ALA-MAL), M5 (40% ALA-60% MAL), M6 (20% ALA-80% MAL) and MAL. RESULTS Mixtures M3, M4, and M5 showed the most PPIX production on skin by widefield fluorescence imaging and fluorescence spectroscopy in 3h of incubation. These results suggest that 50% of ALA and MAL in the same mixture increase the PPIX production in amount, homogeneity and time production when compared to ALA and MAL. This has a positive impact on photodynamic damage optimizing the PDT treatment.

Alterações morfométricas no plexo mioentérico do cólon menor equino distendido experimentalmente

The equine small colon is frequently affected by obstruction, and intestinal motility dysfunction is a common complication after its surgical treatment. This fact may be related to myoenteric plexus lesion caused by distention; however, little is known about the pathophysiology of this condition. The objective of this study was to evaluate the morphological alterations in the myoenteric inervation of segments of small colon of horses subjected to intraluminal distension with reduction of the microvascular perfusion (partial ischemia) of the intestinal wall. Nine horses were used to promote distension of on segment of small colon for 4 hours. Samples of intestinal wall were collected before and at the end of the distension, after 1.5 and 12 hours of reperfusion in the experimental segment and at the end of the procedure in a different distant segment. Samples were processed and histological sections were stained with cresyl violet for the morphometric studies. An image analyzer software was used to measure perimeter, diameter, and area of the neuronal body, nucleus and nucleolus of the neurons and the areas of the cytoplasm and nucleoplasm. Significant reductions (P<0.05) in the areas of the neuronal body and cytoplasm were detected at the end of intestinal distension, returning to the basal values during the reperfusion. In conclusion, intraluminal distension promoted changes in the morphology of the neurons of myoenteric plexus. These morphological modifications may be associated to the motility dysfunction frequently observed in clinical cases.