Eva Rioja

Comparison of three techniques for paravertebral brachial plexus blockade in dogs.

OBJECTIVE To compare success and complication rates, based on staining of nerves and other structures, among three techniques of paravertebral brachial plexus blockade (PBPB) in dogs. STUDY DESIGN Prospective randomized design. ANIMALS A total of 68 thoracic limbs from 34 dogs. METHODS Limbs were randomly assigned to blind (BL) (n = 24), nerve stimulator-guided (NS) (n = 21) or ultrasound-guided (US) (n = 23) technique. Injections were made with 0.3 mL kg(-1) of lidocaine mixed with new methylene blue. Time to perform each block and current used during NS technique were recorded. Dogs were anesthetized during the blocks and euthanized once completed. Dissections were performed to evaluate staining of nerves, spinal cord, mediastinum, pleura and vessels. An anova and Tukey adjustment for time, logistic regression for association between current and nerve staining and a generalized linear mixed model for staining of different structures were used. Significance was considered when p ≤ 0.05. RESULTS The median (range) number of nerves stained was 2 (0-4) with BL, 1 (0-3) with NS and 1 (0-4) with US guided technique. No significant differences in staining of C6, C8 and T1 or other structures were found among techniques. Nerve C7 was more likely to be stained by BL (p = 0.05). Time to perform the blocks was significantly different among techniques, with mean ± SD duration in minutes of 3.6 ± 1.8 with BL, 6.3 ± 2.7 with US and 12.2 ± 5 with NS. The most common complication was staining of the spinal cord (29%, 38% and 39% with BL, NS and US, respectively). CONCLUSIONS Success rates were low and complication rates were relatively high, based on staining, with the three techniques. CLINICAL RELEVANCE The use of more advanced techniques for PBPB in dogs is not justified according to this study. Clinical significance of the complications encountered in this study should be evaluated.

Clinical and pharmacokinetic effects of regional or general anaesthesia on intravenous regional limb perfusion with amikacin in horses

REASONS FOR PERFORMING STUDY Antimicrobial i.v. regional limb perfusion (IV-RLP) is clinically performed on anaesthetised or sedated horses with or without regional anaesthesia. To date, no scientific data are available on the clinical and pharmacokinetic effects of these anaesthetic protocols on antimicrobial IV-RLP, which is believed to result in better tourniquet efficiency due to decreased movement. OBJECTIVE To determine the effects of regional or general anaesthesia on the clinical and synovial pharmacokinetic parameters of amikacin administered by IV-RLP to horses. STUDY DESIGN Experimental crossover study. METHODS Eight healthy horses received 4 treatments of amikacin IV-RLP in a randomised, blinded, crossover design: standing sedation without regional anaesthesia (CNT); standing sedation with i.v. regional anaesthesia; standing sedation with perineural regional anaesthesia (PNA); or general anaesthesia. Synovial fluid amikacin concentrations were measured over 24 h and regional pharmacokinetic parameters calculated. Heart and respiratory rates, visual analogue scale of discomfort, number of times the limb was lifted and number of additional sedations administered were recorded. Analysis of variance crossover analysis was applied with significance level at P < 0.05. RESULTS Amikacin concentrations and regional pharmacokinetic parameters did not differ significantly among treatments. Visual analogue scores (mean ± s.d.) were significantly lower with PNA (19 ± 15) vs. i.v. regional anaesthesia (69 ± 36) or CNT (81 ± 13; P < 0.001). Significantly less lifting of the limb (mean ± s.d.) occurred with PNA (20 ± 20) vs. CNT (54 ± 22; P < 0.04). CONCLUSIONS Perineural regional anaesthesia before IV-RLP was most effective in providing comfort to standing, sedated horses without significantly affecting the regional pharmacokinetic parameters of amikacin. High variability of synovial amikacin concentrations was present. The use of general anaesthesia for IV-RLP is not justified based on this study.

Anaesthetic, analgesic and cardiorespiratory effects of intramuscular medetomidine-ketamine combination alone or with morphine or tramadol for orchiectomy in cats

OBJECTIVES To compare the anaesthetic, analgesic and cardiorespiratory effects of intramuscular (IM) medetomidine and ketamine administered alone or combined with morphine or tramadol, for orchiectomy in cats. STUDY DESIGN Randomised, blinded, prospective clinical study. ANIMALS Thirty client-owned cats. MATERIALS AND METHODS Cats (n = 10 in each group) received a combination of medetomidine (60 μgkg(-1) ) and ketamine (10 mg kg(-1) ) alone (MedK); combined with morphine (0.2 mg kg(-1) ) (MedKM), or combined with tramadol (2 mg kg(-1) ) (MedKT) IM. Time of induction, surgical and recovery events were recorded, and physiological parameters measured and recorded. Analgesia was evaluated with a visual analogue scale, a composite scoring system and the von Frey mechanical threshold device, every hour from three to eight hours post-drug administration injection. Data were analyzed with a linear mixed model, Kruskal-Wallis or Chi-square tests (p < 0.05). RESULTS Median (IQR) induction and recovery times (minutes) were not significantly (p = 0.125) different between groups: 5.6 (2.7-8.0), 7.4 (5.1-9.6) and 8.0 (5.8-14.9) for induction and 128.5 (95.1-142.8), 166.4 (123.1-210.0) and 142.9 (123.4-180.2) for recovery, with MedK, MedKT and MedKM, respectively. Two cats (MedKM) required alfaxalone for endotracheal intubation. In all groups, three or four cats required additional isoflurane for surgery. Arterial oxygen tension overall (mean ± SD: 66 ± 2 mmHg) was low. Surgery resulted in increased systolic arterial blood pressure (p < 0.001), haemoglobin saturation (p < 0.001), respiratory (p = 0.003) and heart rates (p = 0.002). Pain scores did not differ significantly between groups. Von Frey responses decreased over time; changes over time varied by treatment (p < 0.001), MedK returning to baseline values more rapidly than MedKM and MedKT. No cat required rescue analgesics. CONCLUSION AND CLINICAL RELEVANCE All three protocols can provide adequate anaesthesia and analgesia for orchiectomy in cats. However, rescue intervention to maintain surgical anaesthesia may be required in some cats. Oxygen supplementation is advised.

Assessment of behavioural changes in domestic cats during short-term hospitalisation

We evaluated behavioural changes in domestic cats during short-term hospitalisation using a novel cat demeanour scoring system. Thirty-five healthy, client-owned cats admitted for neutering were enrolled. Cats were housed in a standardised cat ward for a short-term hospitalisation period (3–5 days) and demeanour scores were recorded once daily. The scoring system classified cats into one of five behavioural groupings: friendly and confident, friendly and shy, withdrawn and protective, withdrawn and aggressive, and overtly aggressive. Total demeanour score decreased over time (P <0.001) and the demeanour category improved (P <0.001). The intra-class correlation was 0.843 (P <0.001) and kappa was 0.606 (P <0.001), suggesting good repeatability and agreement among investigators. The demeanour scoring system was effective in detecting a change in behaviour in healthy cats undergoing short-term hospitalisation. The findings suggest that healthy cats require 2 days to acclimatise to hospitalisation.

Comparison of cardiac output determined by arterial pulse pressure waveform analysis method (FloTrac/Vigileo) versus lithium dilution method in anesthetized dogs.

OBJECTIVE To compare the determination of cardiac output (CO) via arterial pulse pressure waveform analysis (FloTrac/Vigileo) versus lithium dilution method. DESIGN Prospective study. SETTING University teaching hospital. ANIMALS Six adult dogs. INTERVENTIONS Dogs were instrumented for CO determinations using lithium dilution (LiDCO) and FloTrac/Vigileo methods. Direct blood pressure, heart rate, arterial blood gases, and end-tidal isoflurane (ETIso) and CO(2) concentrations were measured throughout the study while CO was manipulated with different depth of anesthesia and rapid administration of isotonic crystalloids at 60 mL/kg/h. MEASUREMENTS AND MAIN RESULTS Baseline CO measurements were obtained at 1.3% ETIso and were lowered by 3% ETIso. Measurements were obtained in duplicate or triplicate with LiDCO and averaged for comparison with corresponding values measured continuously with the FloTrac/Vigileo method. For 30 comparisons between methods, a mean bias of -100 mL/kg/min and 95% limits of agreement between -311 and +112 mL/kg/min (212 mL/kg/min) was determined. The mean (mL/kg/min) of the differences of LiDCO-Vigileo=62.0402+-0.8383 × Vigileo, and the correlation coefficient (r) between the 2 methods 0.70 for all CO determinations. The repeatability coefficients for the individual LiDCO and FloTrac/Vigileo methods were 187 and 400 mL/kg/min, respectively. Mean LiDCO and FloTrac/Vigileo values from all measurements were 145 ± 68 mL/kg/min (range, 64-354) and 244 ± 144 mL/kg/min (range, 89-624), respectively. The overall mean relative error was 48 ± 14%. CONCLUSION The FloTrac/Vigileo overestimated CO values compared with LiDCO and the relative error was high, which makes this method unreliable for use in dogs.

Effects of a constant rate infusion of magnesium sulphate in healthy dogs anaesthetized with isoflurane and undergoing ovariohysterectomy

OBJECTIVE To determine the effects of intravenous (IV) magnesium sulphate (MgSO(4) ) as a bolus followed by a constant rate infusion (CRI) on anaesthetic requirements, neuroendocrine stress response to surgery, haemostasis and postoperative analgesia in healthy dogs undergoing ovariohysterectomy. STUDY DESIGN Blinded randomized clinical trial. ANIMALS Sixteen female dogs. METHODS After intramuscular premedication with acepromazine (0.05 mg kg(-1) ) and morphine (0.3 mg kg(-1) ), anaesthesia was induced with diazepam (0.2 mg kg(-1) ) and propofol (2 mg kg(-1) ) intravenously and maintained with isoflurane in oxygen in all dogs. Dogs were randomly assigned to two groups, M and C. Group M received MgSO(4) (50 mg kg(-1) over 15 minutes, followed by a 15 mg kg(-1) hour(-1) CRI). Group C received an equivalent bolus and CRI of lactated Ringers solution. In addition, all dogs received lactated Ringers solution (10 mL kg(-1) over 15 minutes followed by 10 mL kg(-1) hour(-1) ). End-tidal isoflurane and carbon dioxide tensions, cardio-respiratory variables, arterial blood gases, electrolytes, ACTH and cortisol concentrations were measured at different time points. Thromboelastography (TEG) was performed pre- and post-anaesthesia. Postoperative pain was evaluated using the short form of the Glasgow Composite Pain Scale. Data were analysed with repeated measures anova and Mann-Whitney U tests (p < 0.05). RESULTS No statistically significant differences between groups were found in any of the measured variables. However, the alpha angle and maximal amplitude recorded by TEG in group M were significantly increased post-anaesthesia, but remained within the reference interval. One dog in Group M and two in Group C received rescue analgesia during recovery. CONCLUSIONS AND CLINICAL RELEVANCE As used in this study, MgSO(4) failed to decrease isoflurane requirements, postoperative pain and stress hormone concentrations; however, it did not produce any cardio-respiratory or major haemostatic side effects. Administration of intravenous MgSO(4) together with an opioid during ovariohysterectomy in dogs does not seem to provide any clinical advantage.

Effects of hypercapnia, hypocapnia, and hyperoxemia on blood oxygenation level-dependent signal intensity determined by use of susceptibility-weighted magnetic resonance imaging in isoflurane-anesthetized dogs.

OBJECTIVE To assess the effects of alterations in PaCO(2) and PaO(2) on blood oxygenation level-dependent (BOLD) signal intensity determined by use of susceptibility-weighted magnetic resonance imaging in brains of isoflurane-anesthetized dogs. ANIMALS 6 healthy dogs. PROCEDURES In each dog, anesthesia was induced with propofol (6 to 8 mg/kg, IV) and maintained with isoflurane (1.7%) and atracurium (0.2 mg/kg, IV, q 30 min). During 1 magnetic resonance imaging session in each dog, targeted values of PaCO(2) (20, 40, or 80 mm Hg) and PaO(2) (100 or 500 mm Hg) were combined to establish 6 experimental conditions, including a control condition (PaCO(2), 40 mm Hg; PaO(2), 100 mm Hg). Dogs were randomly assigned to different sequences of conditions. Each condition was established for a period of >or= 5 minutes before susceptibility-weighted imaging was performed. Signal intensity was measured in 6 regions of interest in the brain, and data were analyzed by use of an ANCOVA and post hoc Tukey-Kramer adjustments. RESULTS Compared with control condition findings, BOLD signal intensity did not differ significantly in any region of interest. However, signal intensities in the thalamus and diencephalic gray matter decreased significantly during both hypocapnic conditions, compared with all other conditions except for the control condition. CONCLUSIONS AND CLINICAL RELEVANCE In isoflurane-anesthetized dogs, certain regions of gray matter appeared to have greater cerebrovascular responses to changes in PaCO(2) and PaO(2) than did others. Both PaO(2) and PaCO(2) should be controlled during magnetic resonance imaging procedures that involve BOLD signaling and taken into account when interpreting findings.

Comparison of the spread of two different volumes of contrast medium when performing ultrasound-guided transversus abdominis plane injection in dog cadavers

OBJECTIVES To compare, via CT imaging, the spread of different volumes of diluted iodinated contrast medium in the transversus abdominis muscle plane of dog cadavers. METHODS Prospective, randomised study. An electro stimulation or a SonoTAP needle was inserted in plane with the ultrasound beam in the fascia between the internal oblique and transversus abdominis muscles. A test dose of 1 ml of diluted contrast (30 mg/mL iohexol) was injected to confirm positioning, followed by 0 · 5 mL/kg (n=14) or 1 mL/kg (n=12) and the distribution of the fluid compared. RESULTS Contrast medium was identified exclusively in the transversus abdominis plane in 19 of 26 dogs. In one dog, the contrast lay between the external and internal oblique muscles and partially in three dogs. Intraperitoneal contrast was detected in 6 of 26 dogs (23%). No significant differences were found in the dorso-ventral or cranio-caudal spread or area of distribution but a significant difference was found in the transverse spread. There was an association between poor ultrasound visualisation of the tip of the needle and intraperitoneal injection. CLINICAL SIGNIFICANCE Injection of 1 mL/kg of diluted contrast did not result in wider cranio-caudal spread in the transversus abdominis muscle plane of dog cadavers when compared with 0 · 5 mL/kg. Intraperitoneal injection is a risk and might be reduced with good needle visualisation.

Anaesthetic management of two Bengal tiger (Panthera tigris tigris) cubs for fracture repair

This case series describes the anaesthetic management of two sibling Bengal tiger (Panthera tigris tigris) cubs that were found to have spontaneous femur fractures due to severe nutritional secondary hyperparathyroidism. Both cubs received a combination of medetomidine (25 µg/kg) and ketamine (4 mg/kg) intramuscularly and were maintained with isoflurane in oxygen. An epidural injection of morphine (0.1 mg/kg) and ropivacaine (1.6 mg/kg) was administered to both tigers, which allowed a low end-tidal isoflurane concentration to be maintained throughout the femur fracture reduction operations. Both cubs experienced profound bradycardia and hypotension during general anaesthesia, and were unresponsive to anticholinergic treatment. Possible causes for these cardiovascular complications included: drug pharmacodynamics (medetomidine, morphine, isoflurane), decreased sympathetic tone due to the epidural (ropivacaine) and hypothermia. These possible causes are discussed in detail.

Transversus abdominis plane block in two calves undergoing umbilical herniorrhaphy

A transversus abdominis plane (TAP) block was performed in two calves undergoing umbilical hernia repair. Both calves were in good health and body condition and were anaesthetised using standard anaesthesia protocols. After placement in dorsal recumbency, the abdomen was scanned with an 11-MHz linear array probe from the last rib to the iliac crest to identify the abdominal musculature comprising the external and internal abdominal oblique muscles and the transversus abdominis (TA). The needle (SonoTAP cannula 22G×50 mm; Pajunk) was advanced using an in-plane technique, and a volume of 0.3 ml/kg was injected after a test dose. No obvious reduction of isoflurane requirements was apparent and one of the calves required rescue analgesia. The calves recovered uneventfully from anaesthesia. This case report discusses the advantages of the TAP block over the paravertebral block, discusses the risks associated with TAP blocks and highlights the importance of training in ultrasound-guided techniques.