Vitality evaluation methods for newborn puppies after cesarean section performed under general inhalation anestesia / Métodos de avaliação da vitalidade neonatal de cães após cesariana sob anestesia geral inalatória

This study aimed to demonstrate and to correlate possible methods for neonatal assessment in dogs born by elective cesarean surgery using inhalation anesthesia, enhancing its advantages and disadvantages as well as proposing lactate measurement as an adjunctive method of evaluation. After elective cesarean surgery of four bitches subjected to morphine premedication followed by propofol induction and sevoflurane anesthesia, 30 neonates were evaluated through blood sampling from the umbilical cord for lactate measurement and blood gas analyses, as well as neurological and cardiorespiratory assessment at birth and at 10 minutes of age. The neonates presented respiratory acidosis and acidemia at birth related to blood lactate values (4.98±1.39mmol/L). Neurological and cardiorespiratory depressions were present at birth with recovery at 10 minutes and no complications were observed during the first 30 days of life. The methods for neonatal assessment used in this study are safe when appropriately interpreted and the effects of general anesthesia on neonates were transient. Blood lactate obtained from the umbilical cord can be an option for the evaluation of these patients.(AU)

Objetivou-se demonstrar e correlacionar os possíveis métodos de avaliação neonatal de filhotes de cães nascidos de cesarianas eletivas com a utilização de anestesia inalatória, apontando suas vantagens e desvantagens e propor a dosagem de lactato sanguíneo como prática auxiliar. Após a cesariana eletiva em quatro cadelas submetidas ao protocolo anestésico composto de morfina, propofol e sevofluorano, foram avaliados 30 neonatos com exames de sangue do cordão umbilical para dosagem de lactato e gases sanguíneos, avaliação neurológica e cardiorrespiratória realizadas no nascimento e aos 10 minutos de vida. Os animais apresentaram acidose respiratória com acidemia ao nascimento, associados a altos valores de lactato sanguíneo (4,89±1,39mmol/L). Ocorreu depressão neurológica e cardiorrespiratória no nascimento, com recuperação após 10 minutos, sem complicações nos primeiros 30 dias. Pode-se concluir que os métodos de avaliação neonatal utilizados são seguros quando interpretados adequadamente e os efeitos da anestesia nos neonatos foram transitórios. O lactato do sangue umbilical pode ser opção na avaliação desses pacientes.(AU)

Pulmonary hemodynamics and alveolar oxygenation in healthy dogs anesthetized with propofol or isoflurane during one-lung ventilation in a closed-thoracic experimental model.

OBJECTIVE To assess pulmonary hemodynamics and alveolar oxygenation in dogs anesthetized with propofol or isoflurane during one-lung ventilation (OLV) in a closed-thoracic experimental model. ANIMALS 6 healthy Beagles. PROCEDURES Dogs were anesthetized with each of 3 protocols (constant rate IV infusion of propofol [0.4 to 1.0 mg/kg/min], isoflurane at the minimum alveolar concentration [MAC], and isoflurane 1.5 MAC), with a 7-day washout period between anesthetic sessions. During each session, dogs were intubated with a double-lumen endotracheal tube, positioned in right lateral recumbency, and administered atracurium (0.1 to 0.2 mg/kg, IV, q 30 min) to allow mechanical ventilation throughout a 2-hour observation period. Dogs underwent two-lung ventilation for 30 minutes, OLV of the right lung for 1 hour, and two-lung ventilation for another 30 minutes. Pulmonary hemodynamic and blood gas variables were evaluated at predetermined times and compared among protocols and over time within each protocol. RESULTS Alveolar oxygenation was not impaired, and mean heart rate and pulmonary artery pressure and occlusion pressure were similar among the 3 protocols. One-lung ventilation caused a significant increase in the arteriovenous shunt fraction only when dogs were anesthetized with isoflurane at 1.5 MAC. Dogs developed respiratory acidosis, which was exacerbated by OLV, during all anesthetic sessions. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated pulmonary hemodynamics and alveolar oxygenation during OLV in a closed-thoracic model were similar regardless of whether dogs were anesthetized with propofol or isoflurane. One-lung ventilation can be successfully performed in dogs by use of a double-lumen endotracheal tube and either propofol or isoflurane.

Eficácia e efeitos hemodinâmicos da anestesia raquidiana com ropivacaína isobárica, hipobárica ou hiperbárica em cães anestesiados com isofluorano / Efficacy and hemodynamic effects of spinal anesthesia with isobaric, hypobaric or hyperbaric ropivacaine in dogs anesthetized with isoflurane

O presente estudo objetivou avaliar a anestesia raquidiana com ropivacaína em cães alterando a baricidade do anestésico local, investigando as alterações hemodinâmicas e complicações. Foram utilizados seis cães, Beagle, 4 anos, submetidos a anestesia inalatória com isofluorano e aos tratamentos: Ghipo = anestesia raquidiana hipobárica (0,5 mL NaCl 0,9% + 0,5 mL ropivacaína 0,75%); Giso = anestesia raquidiana isobárica (0,5 mL NaCl 1,53% + 0,5 mL ropivacaína 0,75%); Ghiper = anestesia raquidiana hiperbárica (0,5 mL glicose 10% + 0,5 mL ropivacaína 0,75%). Após indução anestésica e manutenção com isofluorano, os animais foram posicionados em decúbito lateral direito para a passagem de um cateter de artéria pulmonar pela veia jugular esquerda. Após esse procedimento, a punção subaracnóide foi realizada entre L5-L6 com uma agulha espinhal 22G, seguida da administração de 1 mL de anestésico local em 1 min. Os animais foram mantidos por 60 minutos anestesiados em decúbito ventral. A FC, f, PAM, DC, PAPm e TºC apresentaram aumento progressivo em todos os grupos enquanto que a PCPm, apenas no GHIPO, aumentou ao longo de todos os momentos. O IRPT no GISO apresentou valores significativamente superiores no M1, M5 e M10 comparado aos demais grupos, exceto no M5, em que o GISO diferiu somente do GHIPER. O IRVP no GISO aumentou no M5 em comparação ao MB. Foram observados efeitos adversos como déficit motor unilateral, atonia vesical, excitação, dor aguda e quemose. De acordo com os dados obtidos no presente estudo pode-se concluir que os animais que receberam anestesia raquidiana com as soluções hiperbárica e isobárica apresentaram maior bloqueio motor comprovando que a baricidade influencia diretamente o tipo de fibra a ser bloqueada. A utilização de solução isobárica resulta em um bloqueio misto (motor e sensitivo). As alterações hemodinâmicas descritas na literatura como, bradicardia e hipotensão, não puderam ser evidenciadas neste estudo embora o volume de anestésico tenha sido baixo associado a influência dos efeitos do isofluorano. Em relação às complicações evidenciadas, sugere-se acompanhamento pós-anestésico dos animais submetidos à anestesia raquidiana a fim de que quaisquer alterações possam ser identificadas precocemente e tratadas.(AU)

The aim of the study was to assess hemodynamic changes and complications of spinal anesthesia with ropivacaine at different baricities. Six beagle dogs aged four years. The dogs were anesthetized with isoflurane and subjected to the following treatments: Ghypo = spinal anesthesia with hypobaric ropivacaine (0.5mL of 0.9% NaCl+0.5mL ropivacaine at 0.75%); Giso = isobaric spinal anesthesia (0.5mL of 0,906% NaCl+0.5mL ropivacaine at 0.75%); Ghyper = hyperbaric spinal anesthesia (0.5mL of 10% glucose+0.5mL ropivacaine at 0.75%). After induction to anesthesia and maintenance with isoflurane, animals were positioned in right lateral recumbency for pulmonary artery catheterization through the left jugular vein. Spinal anesthesia was carried out with injection of 1mL of local anesthetic using a 22G Quincke tip needle in the L5-L6 space along 1 minute. Dogs were maintained under inhalation anesthesia for 60 minutes in ventral recumbency. HR, FR, MAP, CO, mPAP and body temperature progressively increased in all groups, whereas PCWP increased only in GHYPO at all time points. The TPRI showed significantly higher values in GISO at M1, M5 and M10 compared to the other groups, except for M5, during which GISO differed only from GHYPER. The PVRI increased at M5 compared to MB in GISO. Side effects such as unilateral motor deficit, bladder atony, excitation, acute pain and chemosis were observed. The hemodynamic changes were not relevant, although inhalation anesthesia with isoflurane might have influenced the results. The changes observed in the study demonstrate that motor blockade is likely to be obtained with isobaric and hyperbaric ropivacaine, thereby confirming the influence of baricity on the type of nerve fibers on the spinal cord. The isobaric solution results in a mixed blockade (motor and sensory blockade). Hemodynamic changes such as hypotension and bradycardia were not evidenced in this study, although local anesthetics were administered in low volumes and together with isoflurane anesthesia. Regarding complications, post-anesthetic observation is warranted in order to identify and treat possible changes. Spinal anesthesia in the conditions studied did not cause hemodynamic changes in isoflurane-anesthetized dogs and is thus considered safe for routine practice, although a few complications are prone to occur.(AU)

Effects on indicators of tissue perfusion in dogs anesthetized with isoflurane at two multiples of the minimum alveolar concentration.

OBJECTIVE: To investigate the effects of isoflurane anesthesia administered at 2 multiples of the minimum alveolar concentration (MAC) on tissue perfusion in dogs. ANIMALS: 8 healthy young adult Beagles. PROCEDURES: A randomized crossover design was used. Dogs were anesthetized with isoflurane at 1.5 or 2.0 times the MAC for 2 hours, a 7-day washout period was provided, and dogs were reanesthetized with the alternate treatment. Various physiologic variables were monitored before anesthesia (baseline), at 20-minute intervals during anesthesia, and after anesthetic recovery. Variable values were compared between MAC multiples by means of repeated-measures ANOVA, with the Tukey test used for multiple comparisons. RESULTS: During anesthesia, mean arterial blood pressure, cardiac output, and mixed venous oxygen saturation were significantly greater when isoflurane was administered at 1.5 versus 2.0 times the MAC. Cardiac output gradually increased during anesthesia at 1.5 times but not at 2.0 times the MAC. Arterial blood lactate concentration did not differ between MAC multiples at any point; however, this concentration decreased with increasing anesthetic duration at both MAC multiples. Oxygen delivery differed between MAC multiples, and oxygen consumption differed from baseline during anesthesia at 2.0 times the MAC. Oxygen extraction was higher at 2.0 versus 1.5 times the MAC. Heart rate differed between MAC multiples only after anesthetic recovery. CONCLUSIONS AND CLINICAL RELEVANCE: Isoflurane anesthesia impaired tissue perfusion in dogs, but these changes would not be clinically relevant with oxygen delivery at 100%. Peripheral tissue perfusion was maintained or improved with time.

Ultrasound-assisted periconal ocular blockade in rabbits.

OBJECTIVE: This study aimed to evaluate the benefit and specifically the feasibility of using ultrasound in ophthalmologic periconal block, and the occurrence of complications. STUDY DESIGN: Prospective experimental study. ANIMALS: Ten healthy New Zealand White rabbits (6-8 months of age), weighing 2.0-3.5 kg. METHODS: Rabbits were anesthetized by intramuscular injection of acepromazine (1 mg kg(-1)), ketamine (30 mg kg(-1)) and xylazine (3 mg kg(-1)). Ultrasound-assisted periconal block with lidocaine was performed on 18 eyes. Intraocular pressure was measured by applanation tonometry whereas corneal sensitivity was assessed using an esthesiometer, before and after each periconal anesthesia. RESULTS: In all 18 eyes, it was possible to adequately visualize the needle shaft within the periconal space, as well as muscular cone, optic nerve and local anesthetic solution spread. Lidocaine 2% without epinephrine (0.79 ± 0.19 mL) was injected into the periconal space. There was no statistical difference between the intraocular pressure (mean ± SD) measured before (10.9 ± 2.9 mmHg) and after (11.9 ± 3.8 mmHg) the periconal anesthesia (p = 0.38). The effectiveness of the ultrasound-assisted technique was shown according to the values for corneal sensitivity, assessed before and after periconal anesthesia (p < 0.0001). Complications were not observed in this study. CONCLUSIONS: Eye ultrasonography allowed visualization of all anatomic structures necessary to perform a periconal block, as well as the needle insertion and anesthetic spread in real time. Further studies are required to prove the real potential of ultrasound for reducing the incidence of complications associated with ophthalmic blocks, especially when anatomic disorders of the eye could potentially increase the risk. CLINICAL RELEVANCE: Ultrasonography is a painless, noninvasive tool that may improve safety of ophthalmic regional blocks, potentially by reducing the prevalence of globe perforation or penetration of the optic nerve associated with the needle-based techniques.

Comparison of anesthetic efficacy and adverse effects associated with peribulbar injection of ropivacaine performed with and without ultrasound guidance in dogs.

OBJECTIVE: To compare the anesthetic efficacy and adverse effects associated with peribulbar injection of ropivacaine (1% solution) performed with and without ultrasound guidance (UG) in dogs. ANIMALS: 15 dogs without ophthalmologic abnormalities. PROCEDURES: Each dog was sedated and anesthetized. A peribulbar injection of ropivacaine (1% solution; 0.3 mL/kg) was performed with UG in 1 eye and without UG in the contralateral eye (control). For each eye, the intraocular pressure (IOP) immediately after eye centralization and number of punctures were recorded; ophthalmic complications, postinjection corneal sensitivity (determined by Cochet-Bonnet esthesiometry), durations of the sensory and motor blockades (the latter determined as the interval to restoration of the vestibuloocular reflex, pupillary light reflex, and conjugate eye movement), and blockade quality were assessed in both eyes following anesthetic recovery. RESULTS: Needle placement was fully visualized in 8 of the 15 eyes injected with UG. For eyes injected with or without UG, there was no difference with regard to the number of punctures, postinjection corneal sensitivity, and sensory or motor blockade duration and quality; however, restoration of conjugate eye movement occurred later in control eyes. For eyes injected with UG, mean IOP was 18.6 mm Hg, compared with 23.3 mm Hg for control eyes. Incidence of subconjunctival hemorrhage was higher for control eyes; severity of chemosis and hyperemia varied over time within both groups of eyes. CONCLUSION AND CLINICAL RELEVANCE: In dogs, peribulbar injection of ropivacaine with UG is feasible in dogs and provides effective sensory and motor blockades similar to those achieved with conventional techniques.

Tumescent local anesthesia with ropivacaine in different concentrations in bitches undergoing mastectomy: plasma concentration and post-operative analgesia.

OBJECTIVE: To compare two concentrations of ropivacaine administered for tumescent local anesthesia (TLA) in dogs undergoing mastectomy. STUDY DESIGN: Prospective randomized clinical study. ANIMALS: Seventeen bitches of various breeds, aged 12 ± 2 years and weighing 10 ± 6.5 kg requiring total unilateral or bilateral mastectomy. METHODS: Dogs were premedicated with acepromazine (0.04 mg kg(-1) ) and morphine (0.4 mg kg(-1) ) intramuscularly. Anesthesia was induced with propofol (2.5 mg kg(-1) ) and midazolam (0.2 mg kg(-1) ) intravenously, followed by intubation and maintenance with isoflurane and TLA. Dogs were randomly allocated to receive TLA either with 0.1% ropivacaine (group G1) or with 0.05% ropivacaine (group G05). TLA was performed by insertion of a multihole needle under the skin and infusion of ropivacaine and lactated Ringer's solution at a fixed volume of 15 mL kg(-1) . Ropivacaine concentrations in arterial blood were measured by high-performance liquid chromatography. Post-operative pain was assessed using two scales (University of Melbourne pain scale and a modified composite measure pain scale) and von Frey filaments, 4 hours after TLA and at 1 hour intervals until sensitivity was regained. A score above 30% of the maximum possible score was considered a positive indicator of pain. RESULTS: Peak plasma concentrations of ropivacaine were measured 240 minutes after TLA in G1. Low concentrations were measured in G05 for 60 minutes, with subsequent increase. Analgesic rescue and return of sensitivity occurred at 7 ± 2.3 and 7 ± 1.9 hours (mean ± SD) after TLA for G1 and G05, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Tumescent local anesthesia with ropivacaine provided satisfactory post-operative analgesia that lasted for several hours, with no difference in duration between the concentrations. No serious side effects were attributed to TLA. Results indicated that 0.05% ropivacaine provided adequate analgesia for mastectomy, however, more studies are required to support this conclusion.

Cardiopulmonary and analgesic effects of caudal epidurally administered ropivacaine in cattle.

OBJECTIVE: To assess cardiopulmonary and analgesic effects after administration of ropivacaine into the caudal epidural space of cattle. STUDY DESIGN: Prospective, single-dose trial. ANIMALS: Eight healthy mixed breed cows aged 8 ± 5 years and weighing 507 ± 112 kg. METHODS: Caudal epidural anesthesia was produced in cows with 0.75% ropivacaine (0.11 mg kg(-1)). Onset time, duration and cranial spread of analgesia were recorded. Heart rate (HR), respiratory rate (f(R)), rectal temperature (RT), and mean arterial blood pressure (MAP) were measured prior to epidural administration (T(0) ) and at 15, 30, 60, 120, 180 and 240 minutes after epidural administration (T(15), T(30), T(60) , T(120) , T(180) and T(240) ). Arterial blood acid-base balance (pH, standard bicarbonate and base excess), gas tension (PaO(2), PaCO(2), SaO(2)) and electrolytes (Na(+), K(+), iCa(2+),Cl(-)) were recorded at T(0), T(30), T(60), T(120), T(180) and T(240). Ataxia was evaluated at T(0), T(30), T(60), T(120), T(180) and T(240) and at 1 hour intervals thereafter until analgesia was no longer present in each animal. RESULTS: Epidurally administered ropivacaine induced variable analgesia extending bilaterally from the coccyx to S3. Time to onset of analgesia and mean duration in the perineal area were 15 ± 4 and 359 ± 90 minutes, respectively. Respiratory rate and RT increased from T(120) to T(240) when compared to the value at T(0) . Ionized calcium and chloride concentrations increased at T(180) and T(240) when compared to T(0). The other variables were not significantly different from baseline values (p > 0.05). Four animals were mildly ataxic. CONCLUSION AND CLINICAL RELEVANCE: Ropivacaine (0.75%, 0.11 mg kg(-1)) can be administered by caudal epidural injection to produce prolonged bilateral perineal analgesia with minimal ataxia and cardiopulmonary changes in standing cattle.

Effect of lidocaine on the minimum alveolar concentration of sevoflurane in dogs.

OBJECTIVE: To investigate the effects of a low-dose constant rate infusion (LCRI; 50 microg kg(-1) minute(-1)) and high-dose CRI (HCRI; 200 microg kg(-1) minute(-1)) lidocaine on arterial blood pressure and on the minimum alveolar concentration (MAC) of sevoflurane (Sevo), in dogs. STUDY DESIGN: Prospective, randomized experimental design. ANIMALS: Eight healthy adult spayed female dogs, weighing 16.0 +/- 2.1 kg. METHODS: Each dog was anesthetized with sevoflurane in oxygen and mechanically ventilated, on three separate occasions 7 days apart. Following a 40-minute equilibration period, a 0.1-mL kg(-1) saline loading dose or lidocaine (2 mg kg(-1) intravenously) was administered over 3 minutes, followed by saline CRI or lidocaine LCRI or HCRI. The sevoflurane MAC was determined using a tail clamp. Heart rate (HR), blood pressure and plasma concentration of lidocaine were measured. All values are expressed as mean +/- SD. RESULTS: The MAC of Sevo was 2.30 +/- 0.19%. The LCRI reduced MAC by 15% to 1.95 +/- 0.23% and HCRI by 37% to 1.45 +/- 0.21%. Diastolic and mean pressure increased with HCRI. Lidocaine plasma concentration was 0.84 +/- 0.18 for LCRI and 1.89 +/- 0.37 microg mL(-1) for HCRI. Seventy-five percent of HCRI dogs vomited during recovery. CONCLUSION AND CLINICAL RELEVANCE: Lidocaine infusions dose dependently decreased the MAC of Sevo, did not induce clinically significant changes in HR or arterial blood pressure, but vomiting was common during recovery in HCRI.