Comparison of lidocaine and lidocaine-xylazine for distal paravertebral anesthesia in dairy cattle.

OBJECTIVE: To determine the time of onset and duration of action of distal paravertebral blocks (DPB) in dairy cattle using lidocaine and lidocaine plus xylazine (LX). ANIMALS: 10 healthy adult Holstein cows. METHODS: Unilateral DPB were performed in 6 cows at L1, L2, and L4. They received 2 treatments (lidocaine and LX) in a blinded random crossover design. Due to treatment failure, 4 additional cows were enrolled. The lidocaine treatment received 1,800 mg (90 mL) of lidocaine, and treatment LX received 1,784 mg (89.2 mL) of lidocaine and 16 mg (0.8 mL) of xylazine. Anesthesia was assessed by response (rapid movements of the tail, directed movements of the feet, or turning of the head towards the site of the needle pricks) to 6 approximately 1-cm deep needle pricks to the paralumbar fossa with a 22-gauge hypodermic needle. The time of onset, duration of action, maximum sedation score, and average heart rate (HR) were compared between treatments. RESULTS: Duration of anesthesia was significantly prolonged after DPB in cows treated with LX (251.6 ± 96.94 minutes) compared to lidocaine (105.8 ± 35.9 minutes; P = .01). Treatment with LX was associated with significantly lower average heart rate (56 ± 3 beats/min) compared to cows treated with lidocaine (59 ± 3 beats/min; P = .045). The LX treatment was associated with mild sedation but was not significant (P = .063). CLINICAL RELEVANCE: The addition of xylazine to a lidocaine DPB provides a longer duration of anesthesia, is inexpensive and practical, and can be implemented with ease.

Comparison of rostral spread of lumbosacral epidural volume calculated by body weight or length of the vertebral column in small-sized anesthetized dogs.

The first objective of this prospective, randomized, crossover experimental trial was to compare the rostral spread of lumbosacral epidural volume calculated by body weight (BW) or vertebral column length (LE) in 6 small, isoflurane-anesthetized female beagle dogs (BW: 7.5 to 10.2 kg; LE measured from the occipital crest to the sacrococcygeal space: 46 to 56 cm). The second objective was to assess the response to a noxious stimulus once the dogs recovered from anesthesia and to determine the effects of the injection on cardiopulmonary variables. While in sternal position, dogs were injected through an epidural catheter with a volume mixture of bupivacaine 0.25% and iopamidol 15% based on BW: 0.2 mL/kg or LE: 0.05 mL/cm (< 50 cm) or 0.07 mL/cm (50 to < 70 cm). Rostral spread was determined by counting the number of vertebrae reached by iopamidol using computed tomography. After anesthesia, cardiopulmonary variables, motor function, and responses to nociceptive stimuli were evaluated. Comparisons were completed with mixed linear models and 2-way analysis of variance (ANOVA) (P < 0.05). The volume of injectate (3.29 ± 0.74 versus 1.81 ± 0.21 mL; mean ± SD) and the number of vertebrae (22 ± 2 versus 19 ± 2 vertebrae) reached by iopamidol were significantly greater for LE than for BW. Response to nociception, time to return of pain sensation, motor function, and cardiopulmonary variables were similar between groups. In conclusion, dosing based on LE resulted in larger rostral spread than when based on BW in dogs of small size.

Le premier objectif de cet essai expérimental croisé prospectif randomisé était de comparer la propagation rostrale du volume épidural lombo-sacré calculé en fonction du poids corporel (PC) ou de la longueur de la colonne vertébrale (LE) chez 6 petites chiennes beagle anesthésiées à l'isoflurane (PC : 7,5 à 10,2 kg; LE mesuré de la crête occipitale à l'espace sacro-coccygien : 46 à 56 cm). Le deuxième objectif était d'évaluer la réponse à un stimulus nocif une fois que les chiens se sont remis de l'anesthésie et de déterminer les effets de l'injection sur les variables cardiopulmonaires. En position sternale, les chiens ont reçu une injection via un cathéter péridural d'un mélange volumique de bupivacaïne à 0,25 % et d'iopamidol à 15 % basé sur le poids corporel : 0,2 mL/kg ou LE : 0,05 mL/cm (< 50 cm) ou 0,07 mL/cm (50 à < 70 cm). La propagation rostrale a été déterminée en comptant le nombre de vertèbres atteintes par l'iopamidol en utilisant la tomodensitométrie. Après l'anesthésie, les variables cardiopulmonaires, la fonction motrice et les réponses aux stimuli nociceptifs ont été évaluées. Les comparaisons ont été complétées avec des modèles linéaires mixtes et une analyse de variance à 2 facteurs (ANOVA) (P < 0,05). Le volume d'injectat (3,29 ± 0,74 versus 1,81 ± 0,21 mL; moyenne ± SD) et le nombre de vertèbres (22 ± 2 versus 19 ± 2 vertèbres) atteints par l'iopamidol étaient significativement plus élevés pour LE que pour BW. La réponse à la nociception, le temps de retour de la sensation de douleur, la fonction motrice et les variables cardiopulmonaires étaient similaires entre les groupes. En conclusion, le dosage basé sur LE a entraîné une plus grande propagation rostrale que lorsqu'il était basé sur BW chez les chiens de petite taille.(Traduit par Docteur Serge Messier).

Evaluation of an automatic approach device to the epidural space of Beagle dogs.

OBJECTIVE: To compare the epidural anesthesia device (EPIA), which facilitates an automatic approach to location of the epidural space, with the performance of clinicians using tactile sensation and differences in pressure when inserting an epidural needle into the epidural space of a dog. STUDY DESIGN: Prospective, crossover experiment. ANIMALS: A total of 14 Beagle dogs weighing 7.5 ± 2.4 kg (mean ± standard deviation). METHODS: Each dog was anesthetized three times at 2 week intervals for three anesthesiologists (two experienced, one novice) to perform 14 epidural injections (seven manual and EPIA device each). The sequence of methods was assigned randomly for each anesthesiologist. The dogs were anesthetized with medetomidine (10 µg kg-1), alfaxalone (2 mg kg-1) and isoflurane and positioned in sternal recumbency with the pelvic limbs extended cranially. Epidural puncture in the manual method was determined by pop sensation, hanging drop technique and reduced injection pressure, whereas using the device a sudden decrease in reaction force on the device was detected. A C-arm identified needle placement in the epidural space, and after administration of iohexol (0.3 mL), the needle length in the epidural space was defined as the mean value measured by three radiologists. Normality was tested using the Kolmogorov-Smirnov test, and significant differences between the two methods were analyzed using an independent sample t test. RESULTS: In both methods, the success rates of epidural insertion were the same at 95.2%. The length of the needle in the epidural space using the device and manual methods was 1.59 ± 0.50 and 1.68 ± 0.88 mm, respectively, with no significant difference (p = 0.718). CONCLUSIONS AND CLINICAL RELEVANCE: EPIA device was comparable to human tactile sense for an epidural needle insertion in Beagle dogs. Further research should be conducted for application of the device in clinical environments.

Low-dose epidural anesthesia decreases the use of intraoperative systemic analgesics in goats undergoing lower urinary tract surgery.

OBJECTIVE: To test whether the use of low-dose epidural anesthesia (EA) in goats undergoing lower urinary tract surgery reduces the requirements of perioperative analgesics, contributes to intraoperative hypotension, and improves postoperative comfort during the first 24 hours after surgery. ANIMALS: Retrospective analysis of 38 goats between January 2019 and July 2022. PROCEDURES: Goats were divided into 2 groups (EA or no EA). Demographic characteristics, surgical procedure, time of anesthesia, and anesthetic agents used were compared between treatment groups. Outcome variables potentially related to the use of EA included dose of inhalational anesthetics, incidence of hypotension (mean arterial pressure < 60 mm Hg), intraoperative and postoperative administration of morphine, and time to first meal after surgery. RESULTS: EA (n = 21) consisted of bupivacaine or ropivacaine 0.1% to 0.2% with an opioid. There were no differences between groups except for age (EA group was younger). Less inhalational anesthetic (P = .03) and less intraoperative morphine (P = .008) were used in the EA group. The incidence of hypotension was 52% for EA and 58% for no EA (P = .691). Administration of postoperative morphine was not different between groups (EA, 67%, and no EA, 53%; P = .686). Time to first meal was 7.5 hours (3 to 18 hours) for EA and 11 hours (2 to 24 hours) for no EA (P = .057). CLINICAL RELEVANCE: Low-dose EA reduced the use of intraoperative anesthetics/analgesics in goats undergoing lower urinary tract surgery without an increased incidence of hypotension. Postoperative morphine administration was not reduced.

Dexmedetomidine Alone or Combined With Morphine for Epidural Anesthesia in Bitches Undergoing Elective Ovariohysterectomy.

The purpose of this study was to assess perioperative analgesia provided by the combination of epidural dexmedetomidine and morphine in bitches undergoing elective ovariohysterectomy. Twenty-four bitches were included in the study and allocated into 3 groups: GM, morphine 0.1 mg/kg; GD, dexmedetomidine 2 µg/kg; and GDM, dexmedetomidine and morphine at the same doses. All solutions were diluted in saline to a total of 0.36 mL/kg. Heart rate (HR), respiratory rate (FR) and systolic blood pressure (SAP) were recorded prior to epidural analgesia (TB), immediately following epidural analgesia (TEA), at surgical incision (TSI), at the first ovarian pedicle clamping (TOP1), at the second pedicle clamping (TOP2), at uterine stump clamping (TUC), at the start of abdominal cavity closure (TSC) and at the end of skin closure (TEC). Rescue analgesia with fentanyl was administered at 2 µg/kg IV if nociception corresponding to a 20% increase of any cardiorespiratory variables was noted. Postoperative pain assessment was performed using a modified composite Glasgow pain scale along the first 6 hours following the end of surgery. Numeric data were compared using ANOVA for repeated measures followed by Tukey test and ovarian ligament relaxation was analyzed using chi-square test under 5% significance. No differences were found on FR among times or groups, although HR showed significant differences between GM and GD at TSI, TOP1, TOP2, TSC and TEC and between GM and GDM at TEA and TSI (significantly lower HR values recorded in dexmedetomidine groups). Differences among time points were found on HR between TB and TEA in GD and on PAS between TOP1 and TSC in GM and between TOP1 and TUC in GDM (P < .05). Ovarian ligament relaxation was significantly more present in groups using dexmedetomidine, although the number of rescue analgesia administrations did not differ among groups. Kaplan-Meyer analysis failed to show significant differences on time of rescue analgesia administration among groups (P > .05). In conclusion, the combination of epidural dexmedetomidine and morphine is a more interesting choice for elective ovariohysterectomy in bitches for producing analgesia comparable to that of each drug alone, with noticeable relaxation of ovarian ligaments and lesser cardiovascular consequences.

The Antinociceptive Effect of Magnesium Sulphate Administered in the Epidural Space in Standing Horses.

To study the antinociceptive properties of epidural magnesium sulphate (MgSO4) in standing horses Experimental, placebo-controlled, masked, cross-over A group of six healthy horses Through an epidural catheter, 1 mg kg -1 MgSO4 (treatment Mg) diluted to a volume of 15 mL or the same volume of saline (treatment S) was administered over 15 minutes. Electrical, thermal and mechanical nociceptive thresholds were determined on the pelvic limb before and 20, 40, 60, 80, 100, 120, 140, 160 and 180 minutes after the start of the injection. Heart rate (HR) and respiratory frequency (fR) were recorded every 10 minutes. Blood samples were collected before treatment and every 30 minutes throughout the study period. Data were assessed for normality using a Shapiro-Wilk test. A linear mixed model with horse as random effect and time, treatment and their interaction as fixed effects was used. Treatments were compared at 20, 60, 120 and 180 minutes using the Wilcoxon rank sum test stratified for horse (global α = 0.05, with Bonferroni correction α = 0.0125). Epidural MgSO4 caused a significant increase in the electrical threshold (mA) (P = .0001), but no significant differences in thermal and mechanical nociceptive thresholds. During the injection of MgSO4, two horses collapsed. One stood up within 20 minutes and was able to continue the study, the second one was excluded. A significant difference was found for HR at T180 (Mg 44 ± 23 beats minute-1; S 32 ± 9 beats minute-1) (P = .0090). Epidural administration of MgSO4 caused an increase in the electrical threshold of the pelvic limbs of horses. Caution is warranted however, as with the current dose, 2 horses collapsed.

Is an epidural component during general anaesthesia for caesarean section beneficial for neonatal puppies' health and vitality?

Regional centro-axial block is a recommended technique for uncomplicated caesarean section in human medicine. Since the application of regional anaesthesia as the only technique in veterinary medicine is impractical, the objective of the study was to assess and compare the epidural component of caesarean section (CS) on maternal and fetal outcomes. Bitches (n = 36) undergoing elective CS were enrolled in this study. Females were randomly assigned into two groups: Gr I (Isoflurane, n = 20) and Gr IE (Isoflurane plus Epidural, n = 16). Anaesthesia was induced with propofol, and maintained with isoflurane in oxygen. In the IE group, epidural anaesthesia was also performed using lidocaine. The maternal intraoperative parameters were compared at three time points: T1 - just before the skin incision, T2 - after the last puppy removal, and T3 - at the end of surgery. At least 100 mcl of mixed umbilical cord blood was collected for gas analysis. The modified Apgar scoring system (AS) was used to objectively score newborn health and vitality immediately after birth (0 min), 5 and 20 min after birth. Systolic, diastolic, and mean blood pressure were lower in the IE group at T1, T2, and T3 compared to I group (p < 0.05). In the combined anaesthesia group blood pressure remained stable but low at all time points. Throughout surgery, the IE group required a lower concentration of isoflurane (p < 0.05). The median values of the umbilical blood gas results were found to be similar (p > 0.05) in both investigated groups. The initial results of the Apgar score were comparable in the I and IE groups (p > 0.05). However, subsequent AS measurements revealed significant differences between both groups. Puppies from the IE group received better AS scores at 5 and 20 min compared to the I group (median AS 8 and 9 vs. 5 and 8, respectively). The results obtained demonstrated that epidural anaesthesia administration reduced the requirement for isoflurane in dams undergoing caesarean section and despite episodes of maternal hypotension did not affect the results of neonatal umbilical blood gas. Furthermore, newborns from the epidural anaesthesia group improved more quickly postnatally, developing a satisfactory condition in a shorter time.

Thoracic epidural anaesthesia vs intrathecal morphine in dogs undergoing major thoracic and abdominal surgery: clinical study.

BACKGROUND: There is scant clinical research on neuraxial analgesia in dogs undergoing major surgery. With this study we compared the perioperative analgesic effects of thoracic epidural anaesthesia (TEA) and intrathecal morphine (ITM) in dogs scheduled for thoracic or cranial abdominal surgery. The dogs received methadone and dexmedetomidine, were anaesthetized with propofol maintained with sevoflurane, and randomly assigned to receive either TEA (ropivacaine 0.5% at 0.2 mg/kg and morphine 0.1 mg/kg administered at T12-T13) or ITM (morphine 30 µg/kg administered at L6-L7). Intraoperative rescue analgesia (iRA) was fentanyl 1 µg/kg administered if heart rate or mean arterial pressure increased by 30% above the pre-stimulation level. Glasgow Pain Composite Scale score (GPCS) dictated the use of postoperative rescue analgesia (pRA) with methadone 0.2 mg/kg. RESULTS: There was a statistically significant difference in iRA, median time to first fentanyl bolus, median fentanyl dose after surgical opening, and median GPCS score at 30 minutes (min), 1 ,2, 4, 6, and 8 hours (h) between the two groups (p<0.001; p<0.001; p<0.001; p<0.01; p<0.01; p<0.001; p<0.01; p=0.01; p=0.01, respectively). Fewer TEA than ITM group dogs required iRA during surgical opening and pRA: 5% (1/18) and 2/18 (11%), respectively, in the TEA and 83% (16/18) and 10/18 (55%), respectively, in the ITM group. Side effects were urinary retention in 3/18 (16%) TEA group dogs and 2/18 (11%) ITM group dogs and prolonged sedation in 2/18 (11%) in ITM group dogs. TEA and ITM were effective in managing perioperative pain in dogs undergoing thoracic or cranial abdominal surgery.

Comparison of cervical epidural morphine with intravenous morphine administration on antinociception in adult horses using thermal threshold testing.

OBJECTIVE: To compare the antinociceptive effects of morphine administered via cervical epidural catheter to intravenously administered morphine using a thermal threshold (TT) testing model in healthy adult horses. STUDY DESIGN: Prospective, randomized, blinded experimental study. ANIMALS: A total of six university-owned adult horses. METHODS: Horses were instrumented with a cervical (C1-C2) epidural catheter and TT testing device with probes at withers and thoracic limb coronary bands. All horses underwent three TT testing cycles including cervical epidural morphine administration (treatment EpiM; 0.1 mg kg-1), systemic morphine administration (treatment SystM; 0.1 mg kg-1) and no morphine administration (treatment Control). Baseline TT was established prior to treatments, and TT was tested at 15, 30, 60, 90, 120, 150, 180, 240, 300, 360, 420, 480, 600 and 720 minutes following treatment. Horses underwent a 5 day washout period between treatments and the order of treatment was randomized. Differences between treatments were analyzed with repeated measures anova. RESULTS: Systemic and epidural morphine administration resulted in significantly higher TT values compared with baseline and control treatment. The duration of effect was significantly longer in treatment EpiM (10-12 hours) than in treatment SystM (1.5-2.0 hours). Horses in treatment EpiM had significantly higher TT values at time points 180-600 minutes (withers) and 300-600 minutes (coronary band) than horses in treatment SystM. CONCLUSIONS AND CLINICAL RELEVANCE: Cervical epidural administration of morphine provided antinociceptive effects as measured by increased TT for 10-12 hours compared with 1.5-2.0 hours for intravenously administered morphine. No complications or adverse effects were noticed following epidural placement of a C1-C2 catheter and administration of morphine. The use of a cervical epidural catheter can be considered for analgesia administration in treatment of thoracic limb and cervical pain in the horse.

Epidural anesthesia in dogs undergoing hindlimb orthopedic surgery: effects of two injection sites.

This prospective clinical trial evaluated the effects of epidural anesthesia (EA) placed at the lumbosacral compared to the L5-L6 junction in dogs undergoing hindlimb orthopedic surgery. In all, 98 dogs were randomly assigned to receive injection at either L7-S1 (LS group) or L5-L6 (LL group) at the same local anesthetic regimen (1 mg/kg bupivacaine 0.5% and 0.1 mg/kg morphine 1%). Fentanyl (1 µg/kg) was the intraoperative rescue analgesia (iRA) administered if mean arterial pressure increased by 30% above pre-stimulation value. Procedural failure, iRA, hypotension, motor block resolution, and postoperative side effects were recorded. There were 7/47 (15%) epidural procedural failures in the LS group and 8/51 (16%) (P=1.00) in the LL group; iRA was administered in 21/40 (52%) LS group dogs and in 13/43 (30%) LL group dogs, respectively (P=0.047). The incidence of hypotension was 10/40 (25%) and 16/43 (37%) in the LS group and the LL group, respectively (P=0.25). Proprioceptive residual deficit at 8 hr after EA was recorded in 3/26 (12%) in group LS dogs and in 13/26 (50%) group LL dogs, respectively (P=0.01). The proprioceptive residual deficit at 24 hr in one dog (LL group) resolved within 36 hr. No episodes of postoperative urinary retention, pruritus or neurological damage were recorded. The L5-L6 EA decreased significantly iRA but delays the proprioceptive recovery time. Further studies are needed to determine whether a lower bupivacaine dose reduces the duration of the residual block retaining the same incidence of iRA.

Real-time ultrasound-guided lumbosacral epidural anaesthesia in obese or appropriate body condition score dogs: A randomized clinical trial.

Correctly identifying the puncture site and needle position in obese dogs can be challenging to achieve epidural anaesthesia. The current study aimed to evaluate a real-time ultrasound-guided technique, to perform epidural anaesthesia in obese or appropriate body condition score dogs, based on visualization of local anaesthetic flow during its injection, compared to the traditional method of palpation of anatomical landmarks. Seventy-two client-owned dogs were evaluated in a prospective, comparative, randomized clinical trial, allocated into four groups of 18 dogs. For the Palpation-guided 1 (PG1) and 2 (PG2) groups, epidural anaesthesia was based on palpating anatomical landmarks. Dogs with a body condition score (BCS) 1-5/9 were included in the PG1 (non-obese), and those with a BCS 6-9/9 in PG2 (obese) groups. In the Ultrasound-guided 1 (USG1 - BCS 1-5/9) and 2 (USG2 - BCS 6-9/9) groups, epidural anaesthesia was guided by ultrasound (US). The flow of anaesthetic through the epidural canal was observed in all dogs by US. There were fewer needle-to-bone contacts in the US-guided groups when performing epidural anaesthesia; this only occurred on the vertebral laminae, never in the vertebral canal. Ultrasound guidance enabled local anaesthetic injection into the epidural space without the need for palpation of anatomical landmarks to guide needle placement. Blood reflux occurred in 11.1% (PG1), 22.2% (PG2), 5.5% (USG1), and 0% (USG2) of the dogs. Ultrasound-guided punctures led to fewer vascular punctures. Epidural anaesthesia was effective in all animals, and no complications were observed.

Intraoperative effect of low doses of ketamine or dexmedetomidine continuous rate infusions in healthy dogs receiving propofol total intravenous anaesthesia and epidural anaesthesia: A prospective, randomised clinical study.

The present study aimed to determine the effect of either ketamine or dexmedetomidine constant rate infusion (CRI) on intraoperative propofol anaesthetic requirements during total intravenous anaesthesia (TIVA) in healthy dogs undergoing hindlimbs orthopaedic procedures receiving epidural anaesthesia. In this randomised, blinded clinical study, thirty-nine healthy client-owned dogs were premedicated intramuscularly (dexmedetomidine 4 µg/kg and methadone 0.3 mg/kg). General anaesthesia was induced to effect with propofol administered as intravenous bolus, and maintained with propofol TIVA (18 mg/kg/h), adjusted to meet the suitable clinical anaesthetic depth (indicatively±20%) based on clinical judgement. Lumbosacral epidural anaesthesia was performed using bupivacaine (1 mg/kg) and morphine preservative free (0.1 mg/kg). Dogs randomly received either saline (SP; loading dose 1 mL/kg, CRI 1 mL/kg/h), or ketamine (KP; loading dose 1.5 mg/kg, CRI 1.5 mg/kg/h), or dexmedetomidine (DP; loading dose 1 µg/kg/, CRI 1 µg/kg/h). Physiological variables were recorded intraoperatively at 5-min intervals using standard-of-care monitoring. Recovery quality and duration were recorded. Treatment groups were compared with parametric and non-parametric tests as appropriate, p < 0.05. Propofol rates and recovery scores were similar between groups. Overall mean and diastolic blood pressures were higher in group DP compared to group KP (12-14 mmHg, p = 0.016 and p = 0.015, respectively). More dogs required mechanical ventilation in group KP (12 dogs) than in either group SP or DP (7 dogs per group, p = 0.037). Ketamine or dexmedetomidine CRIs, at the studied rates, did not reduce propofol TIVA requirements in dogs undergoing orthopaedic surgery with epidural anaesthesia.

Success Rate and Perioperative Complications of Lumbosacral Extradural Anaesthesia in Dogs Undergoing Total Hip Replacement: A Double-Centre Retrospective Study.

OBJECTIVE: The aim of this study was to retrospectively evaluate the success rate and perioperative complications of lumbosacral extradural anaesthesia in dogs undergoing total hip replacement. STUDY DESIGN: Records of dogs undergoing total hip replacement in which lumbosacral extradural anaesthesia with 0.5% levo- or bupivacaine combined with either morphine or buprenorphine were retrieved. Success rate was defined as intraoperative fentanyl consumption <1 µg/kg/h with no intravenous infusion of other analgesic drugs and no additional morphine/methadone within the first 3 hours from premedication. Prevalence of intraoperative anaesthetic and postoperative surgical complications was calculated. RESULTS: Overall, 206 dogs were included in the study. Success rate was 88.7%. Hypercapnia (75.2%), hypotension (46.1%), hypothermia (27.7%) and regurgitation (6.3%) were recorded during anaesthesia. Within 24 hours post-surgery, urinary retention (17.8%), vomiting/regurgitation/diarrhea (8.2%) and sciatic neurapraxia of the operated limb (5.8%) were recorded. Luxation of the operated hip occurred at 48 and 72 hours after surgery in two dogs and one dog respectively. One dog had cardiopulmonary arrest at 52 hours after surgery. CONCLUSION: While hypercapnia, hypotension and hypothermia might develop intraoperatively, the high success rate and the relatively low prevalence of postoperative surgical complications directly associated with lumbosacral extradural anaesthesia justify its use in dogs undergoing total hip replacement.

Effects of thoracolumbar epidural anesthesia with lidocaine on the systemic hemodynamics and hepatic blood flow in propofol anesthetized dogs.

General anesthesia reduces hepatic blood flow (HBF) from circulatory depression. Total intravenous anesthesia (TIVA) is associated with decreased circulatory depression compared to inhalation anesthesia, and epidural anesthesia using local anesthetics increases blood flow by blocking the sympathetic nerves and expanding blood vessels. We investigated the effects of thoracolumbar epidural anesthesia with TIVA on HBF in dogs. Six Beagle dogs had epidural catheters placed between T13 and L1 and were anesthetized with propofol and vecuronium. Physiological saline (control) or 2% lidocaine (0.2 ml/kg, followed by 0.2 ml/kg/hr) was administered at 1-2 weeks intervals. Heart rate (HR), cardiac index (CI), mean arterial pressure (MAP), and systemic vascular resistance index (SVRI) were recorded at 10-min intervals from before epidural injections (T0) to 110 min. Indocyanine green test was used to measure HBF during the awake state and until 90 min after epidural injections. HR and CI did not differ between treatments. MAP and SVRI after lidocaine were significantly lower than those of controls, and the lowest MAP value was 65 ± 11 mmHg at T10. Compared to T0, after lidocaine treatment, HBF was significantly higher at T30, T60 and T90 (P<0.05); while, after control treatment, no significant change was evident at any time point. Despite a decrease in MAP by this technique, HBF was either maintained at pre-anesthetic levels or increased in comparison to controls, probably due to vasodilation of the hepatic artery induced by the selective blockade sympathetic ganglia.

Evaluation of perfusion index as a noninvasive tool to determine epidural anesthesia effectiveness in dogs.

OBJECTIVE: To evaluate perfusion index (PI) as a noninvasive tool to determine effectiveness and onset of epidural anesthesia in dogs. STUDY DESIGN: Prospective clinical trial. ANIMALS: A total of 21 adult dogs, aged 6.5 ± 3 years and weighing 34.9 ± 6.4 kg, undergoing a tibial plateau leveling osteotomy. METHODS: Dogs were premedicated intramuscularly with acepromazine (0.03 mg kg-1) and hydromorphone (0.1 mg kg-1) and anesthetized with intravenous propofol (to effect) and isoflurane in oxygen. A surface transflectance probe was secured to the tail base to monitor PI and a dorsal pedal artery catheter was placed for invasive blood pressure monitoring. A lumbosacral epidural was performed with the dog in sternal recumbency. Dogs were randomly assigned for inclusion of epidural morphine (0.1 mg kg-1) or morphine (0.1 mg kg-1) and lidocaine (4 mg kg-1). PI was recorded following instrumentation of each dog just prior to the epidural (baseline), at 10 minute intervals for 30 minutes, before and after the surgical skin incision and before and after completion of the osteotomy. Physiological variables and end-tidal isoflurane were recorded at the same time points. RESULTS: There was no significant difference in PI between the groups at any time point. There was a significant change in end-tidal isoflurane before and after the skin incision in the epidural morphine and epidural morphine-lidocaine groups (p = 0.04, p = 0.05, respectively) and before and after the osteotomy in each group for heart rate (p = 0.001, p = 0.04), diastolic (p = 0.01, p = 0.01) and mean arterial blood pressure (p = 0.03, p = 0.05). CONCLUSIONS AND CLINICAL RELEVANCE: PI did not provide an objective means for determining the onset or effectiveness of epidural anesthesia in anesthetized dogs and alternate methods of noninvasive assessment should be investigated.

Evaluation of electrical nerve stimulation to confirm sacrococcygeal epidural needle placement in dogs.

OBJECTIVES: To evaluate the use of 0.7 mA as a fixed electrical current to indicate epidural needle placement and to confirm that 0.7 mA is greater than the upper limit of the minimal electrical threshold (MET) for sacrococcygeal epidural needle placement in dogs. STUDY DESIGN: Prospective clinical study. ANIMALS: A group of 20 client-owned dogs. METHODS: During general anesthesia and with standard monitoring, the presence of the patellar reflex was confirmed in all dogs. An insulated needle was inserted through the sacrococcygeal intervertebral junction, and absence of tail movement was confirmed when a fixed electrical current of 0.7 mA was applied. Then, the needle was further advanced toward the epidural space until the expected motor response was obtained - the nerve stimulation test (NST). The NST was considered positive when a motor response of the muscles of the tail was elicited but not the perineal muscles, whereas it was considered negative when no movement of the tail was evoked. The electrical current was turned to 0 mA and then increased by 0.01 mA increments until tail movement was evoked; this was recorded as the MET. In the positive NST cases, 0.05 mL cm-1 occipitococcygeal length of 2% lidocaine or 0.25-0.5% bupivacaine was administered. Epidural blockade was confirmed by the loss of patellar reflex. Descriptive statistics were used to present data. RESULTS: Sacrococcygeal epidural needle placement, corroborated by loss of the patellar reflex, was correctly predicted in 89.5% (95% confidence interval, 68.6-97.1%) of the cases. The MET was 0.22 mA (0.11-0.36). CONCLUSIONS AND CLINICAL RELEVANCE: A current of 0.7 mA is approximately twice the upper limit of the MET for epidural placement. Therefore, this study demonstrates, with a success rate of 89.5%, the adequacy of using 0.7 mA as the fixed electrical current to detect sacrococcygeal epidural needle placement in dogs.

Transient skin and fur color change after trichotomy of the sacrococcygeal region for epidural anesthesia in a domestic cat (Felis catus) / Mudança transitória da cor da pele e pelo após tricotomia da região sacrococcígea para anestesia epidural em gata doméstica (Felis catus)

A clinical case in which skin and hair color change occurred after sacrococcygeal epidural anesthesia in a nine-month-old Siamese cross queen undergoing ovariohysterectomy (OHE) is described. Six weeks after surgery, during a re-check, it was noted that in the sacrococcygeal region the color of the skin and new hair growth was dark with a color comparable to the color present on the body extremities (muzzle, pinnae, legs, and tail). The skin and new hair growth of the shaved abdomen presented a standard color. The key enzyme of the melanogenic pathway in mammals is tyrosinase (TYR), and the Siamese temperature-sensitive phenotype is the result of genetic mutations that makes TYR function thermolabile. The activity of TYR in these cats is limited to the extremities where the temperature is lower while pigment production is impaired in the other body areas. The trichotomy of the sacrococcygeal region performed during wintertime in an outdoor cat was probably the trigger for increased activity of TYR in this area promoting pigment production. The absence of the same alterations in the abdominal area may be justified by less exposure of that region to the external environment, as well as to the feline habits of sedentarism, that avoid significant cooling in these regions. This report highlights the importance of taking this type of occurrence into account when performing an epidural in the Siamese cat breed. Also, to avoid skin color change in this breed, the authors recommend a midline abdominal instead of a flank approach to perform OHE.(AU)

Descreve-se um caso clínico no qual ocorreu mudança na cor da pele e do pelo após anestesia epidural sacrococcígea numa gata cruzada de raça Siamês de nove meses submetida à ovariohisterectomia (OVH). Seis semanas após a cirurgia, durante uma avaliação pós-operatória, notou-se que na região sacrococcígea, a cor da pele e o crescimento do pelo apresentavam uma cor escura, comparável à das extremidades do corpo (face, orelhas, membros e cauda). A pele e o crescimento do pelo do abdómen, que também havia sido tosquiado, apresentavam uma cor padrão. A enzima chave da via melanogênica em mamíferos é a tirosinase (TYR) e o fenótipo siamês sensível à temperatura é o resultado de mutações genéticas que tornam a função TYR termolábil. A atividade da TYR nestes gatos é limitada às extremidades onde a temperatura é mais baixa, enquanto a produção de pigmento é prejudicada em outras áreas do corpo. A tricotomia da região sacrococcígea realizada durante o inverno nesta gata com acesso livre ao ambiente externo, provavelmente determinou um aumento da atividade da TYR nesta área, promovendo a produção de pigmento. A ausência das mesmas alterações na região abdominal pode ser justificada pela menor exposição desta área do corpo ao ambiente externo, também devido aos hábitos felinos de sedentarismo, que evitam resfriamento significativo nestas regiões. Este relato destaca a importância de se levar em consideração a possibilidade deste tipo de ocorrência quando da realização de uma anestesia epidural nesta raça de gatos. Além disso, os autores recomendam uma abordagem abdominal na linha média ao invés de uma abordagem de flanco para realizar a OVH nesta raça, a fim de evitar a alteração da cor da pele.(AU)