Michele Barletta

Assessment of v-gel supraglottic airway device placement in cats performed by inexperienced veterinary students

Endotracheal intubation has been associated with several complications in cats. The v-gel supraglottic airway device (SGAD) has been developed to adapt to the unique oropharynx of the cat and to overcome these complications. Thirty-three cats were randomly assigned to receive an endotracheal tube (ETT group) or a v-gel SGAD (v-gel group) after induction of general anaesthesia. Third year veterinary students without previous clinical experience placed these devices under direct supervision of an anaesthesiologist. Amount of propofol, number of attempts, time required to secure the airway, leakage around the device, signs of upper airway discomfort and food consumption were compared between the two groups. The v-gel group required less propofol (P=0.03), less time (P<0.01) and fewer attempts (P<0.01) to secure the cats’ airway. The incidence of leakage was lower for the v-gel group immediately after placement of the device (P<0.01) and 60 minutes after induction of general anaesthesia (P=0.04). Cats that received the v-gel SGAD presented a lower incidence of upper airway discomfort immediately after the device was removed (P=0.03) and recorded a higher food consumption score (P=0.03). The v-gel SGAD is a feasible way to secure the airway of healthy cats when performed by inexperienced personnel.

Comparison between invasive blood pressure and a non-invasive blood pressure monitor in anesthetized sheep

Monitoring blood pressure under general anesthesia in animals is important to prevent hypotension and poor tissue perfusion. Thirteen sheep were enrolled to evaluate the accuracy of the petMAP, a portable non-invasive blood pressure (NIBP) monitor. Animals were anesthetized with midazolam, fentanyl, ketamine, propofol and maintained with isoflurane in oxygen for ovariectomy. Invasive and non-invasive (petMAP) blood pressure measurements were recorded simultaneously every 5 minutes. Agreement between IBP and NIBP was assessed by evaluation of bias and 95% limits of agreement (LOA) using the Bland-Altman method and correlation coefficient. None of the measurements met the criteria for good agreement between invasive and non-invasive readings established by the Association for the Advancement of Medical Instrumentation. Systolic blood pressure readings obtained at the left thoracic limb site and mean blood pressure at the right pelvic limb site met the bias and LOA criteria established by the American College of Veterinary Internal Medicine.

Determination of minimum alveolar concentration of isoflurane in dogs and cats using the up-and-down method. A preliminary study

Minimum alveolar concentration (MAC) is a reliable measurement of the potency of inhaled anesthetic agents. The determination of MAC in different species has followed a fairly consistent methodology. In people, MAC is determined with the up-and-down method, whereas in animal the bracketing technique is commonly used. The objectives of this study were to determine the MAC value of isoflurane in dogs and cats using the up-and-down method and to determine the MAC value of isoflurane at extubation (MACex). General anesthesia was induced in 13 dogs and 5 cats with 5% isoflurane in oxygen. An initial end-tidal isoflurane concentration of 1.3% was used for the first dog and of 1.6% for the first cat and maintained constant for ≥20min. A noxious stimulus in the form of Carmalt forceps was applied to the base of the tail for no more than one minute or until movement was noticed. After stimulation, the response was recorded as positive (movement) or negative (no movement) and the animal was recovered. The end-tidal isoflurane concentration of the following animal was increased or decreased by 0.1% if the response of the previous animal to the stimulus was negative or positive, respectively. Isoflurane MAC values in dogs were 1.27% and 1.23%. Isoflurane MAC value in cats was 1.58%. MACex value was 0.45% in dogs and in cats. The up-and-down method for MAC determination achieved similar results when compared to MAC values of isoflurane in dogs and cats reported in the literature using the bracketing technique.

Retrospective study of intra-anesthetic predictors of prolonged hospitalization, increased cost of care and mortality for canine patients at a veterinary teaching hospital

OBJECTIVE To determine the impact of intraoperative anesthetic variables on the length of hospitalization, cost of care and mortality in dogs. STUDY DESIGN Retrospective, observational study. ANIMALS A total of 235 dogs undergoing general anesthesia. METHODS Medical records of dogs undergoing general anesthesia between 2007 and 2014 at the University of Georgia Veterinary Teaching Hospital were reviewed. Data collected included demographic data, American Society of Anesthesiologists (ASA) physical status, type and duration of anesthesia, hemodynamic variables, temperature, ventilation, fluid therapy and adjunctive drugs administered. Outcome variables were length of hospitalization in the intensive care unit (ICU), hospital charges and survival to discharge. RESULTS The only factor significantly associated with duration of ICU care was higher ASA status (p<0.0001). Factors associated with increased cost of hospitalization were ICU duration (p<0.0001), anesthesia duration (p<0.0001), hemorrhage amount (p<0.0001), colloid use (p=0.0081), increased age (p=0.0253), increased weight (p = 0.0293) and presence of hypertension (p=0.0179). Overall mortality rate was 5.1%. The only factors negatively associated with survival were the administration of colloids (p<0.0008) and ASA status (p=0.0314). CONCLUSIONS AND CLINICAL RELEVANCE Several intrinsic patient factors and intraoperative hemodynamic variables were significantly associated with postoperative morbidity and mortality in dogs. These factors might have prognostic value in conjunction with preoperative risk assessment, and patient outcome may be improved by stricter intraoperative control of these variables.

Effects of acepromazine and trazodone on anesthetic induction dose of propofol and cardiovascular variables in dogs undergoing general anesthesia for orthopedic surgery

OBJECTIVE To compare the doses of propofol required to induce general anesthesia in dogs premedicated with acepromazine maleate or trazodone hydrochloride and compare the effects of these premedicants on cardiovascular variables in dogs anesthetized for orthopedic surgery. DESIGN Prospective, randomized study. ANIMALS 30 systemically healthy client-owned dogs. PROCEDURES 15 dogs received acepromazine (0.01 to 0.03 mg/kg [0.005 to 0.014 mg/lb], IM) 30 minutes before anesthetic induction and 15 received trazodone (5 mg/kg [2.27 mg/lb] for patients > 10 kg or 7 mg/kg [3.18 mg/lb] for patients ≤ 10 kg, PO) 2 hours before induction. Both groups received morphine sulfate (1 mg/kg [0.45 mg/lb], IM) 30 minutes before induction. Anesthesia was induced with propofol (4 to 6 mg/kg [1.82 to 2.73 mg/lb], IV, to effect) and maintained with isoflurane or sevoflurane in oxygen. Bupivacaine (0.5 mg/kg [0.227 mg/lb]) and morphine (0.1 mg/kg [0.045 mg/lb]) were administered epidurally. Dogs underwent tibial plateau leveling osteotomy (n = 22) or tibial tuberosity advancement (8) and were monitored throughout anesthesia. Propofol induction doses and cardiovascular variables (heart rate and systemic, mean, and diastolic arterial blood pressures) were compared between groups. RESULTS The mean dose of propofol required for anesthetic induction and all cardiovascular variables evaluated did not differ between groups. Intraoperative hypotension developed in 6 and 5 dogs of the acepromazine and trazodone groups, respectively; bradycardia requiring intervention developed in 3 dogs/group. One dog that received trazodone had priapism 24 hours later and was treated successfully. No other adverse effects were reported. CONCLUSIONS AND CLINICAL RELEVANCE At the described dosages, cardiovascular effects of trazodone were similar to those of acepromazine in healthy dogs undergoing anesthesia for orthopedic surgery.

Critical incident technique analysis applied to peri-anesthetic cardiac arrests at a university teaching hospital

OBJECTIVE To apply the critical incident technique (CIT) methodology to a series of perianesthetic cardiac arrest events at a university teaching hospital to describe the factors that contributed to cardiac arrest. STUDY DESIGN CIT qualitative analysis of a case series. ANIMALS A group of 16 dogs and cats that suffered a perioperative cardiac arrest between November 2013 and November 2016. METHODS If an arrest occurred, the event was discussed among the anesthesiologists. The discussion included a description of the case, a description of the sequence of events leading up to the arrest and a discussion of what could have been done to affect the outcome. A written description of the case and the event including animal signalment and a timeline of events was provided by the supervising anesthesiologist following discussion among the anesthesiologists. Only dogs or cats were included. After the data collection period, information from the medical record was collected. A qualitative document analysis was performed on the summaries provided about each case by the supervising anesthesiologist, the medical record and any supporting documents. Each case was then classified into one or more of the following: animal, human, equipment, drug and procedural factors for cardiac arrest. RESULTS The most common factor was animal (n=14), followed by human (n=12), procedural (n=4), drugs (n=1) and equipment (n=1). The majority (n=11) of animals had multiple factors identified. CONCLUSIONS AND CLINICAL RELEVANCE Cardiac arrests during anesthesia at a referral teaching hospital were primarily a result of animal and human factors. Arrests because of procedural, drug and equipment factors were uncommon. Most animals experienced more than one factor and two animals arrested after a change in recumbency. Future work should focus on root cause analysis and interventions designed to minimize all factors, particularly human ones.

Influence of sedation on onset and quality of euthanasia in sheep

The purpose of this study was to determine if dexmedetomidine administered IV prior to euthanasia in sheep affected the speed or quality of euthanasia. Twenty clinically healthy Dorset-cross adult ewes between 1 and 3years of age were enrolled in a randomized blinded experimental trial. The subjects were randomly assigned to receive dexmedetomidine 5μg/kg IV or an equivalent volume of saline. Five minutes later, euthanasia was accomplished with a pentobarbital/phenytoin overdose given IV. The time to apnea, asystole, cessation of audible heartbeat, and absence of corneal reflex were recorded by two blinded investigators. If any muscle spasms, contractions, vocalization, and/or dysrhythmias were noted, the time was recorded and type of ECG abnormality was described. An overall score of the euthanasia event was assigned using a numeric rating scale (NRS) after the animal was declared dead. The time to loss of corneal reflex was significantly longer in sheep given dexmedetomidine compared with those who received saline (P=0.03). Although vocalization was observed only in some animals premedicated with dexmedetomidine, no significance was found for this event and no other significant differences between groups were noted. Dexmedetomidine at 5μg/kg IV 5min prior to injection of pentobarbital/phenytoin for euthanasia did not substantially affect the progress of euthanasia. Dexmedetomidine may be given to sedate sheep prior to euthanasia without concern for it adversely affecting the progress of euthanasia, however vocalization may occur.

Accuracy of an oscillometric blood pressure monitor in anesthetized pigs

The purpose of this study is to evaluate the accuracy of an oscillometric blood pressure monitor in anesthetized pigs. Invasive blood pressure (IBP) and noninvasive blood pressure (NIBP) measurements were taken using a DRE Waveline Pro multiparameter monitor at four different time points in 17 pigs undergoing injectable anesthesia. NIBP measurements were taken on both the thoracic and pelvic limbs. Bland Altman analysis was used to assess agreement between methods and a linear mixed-effects model was used to evaluate the effect of cuff position and blood pressure on bias. Invasive systolic arterial pressure (SAP) ranged between 112 and 161 mmHg (mean ± SD: 138.8 ± 13.3; median: 139.5). Invasive diastolic arterial pressure (DAP) ranged between 60 and 104 mmHg (mean ± SD: 86.0 ± 9.1; median: 87.0). Invasive mean arterial pressure (MAP) ranged between 79 and 121 mmHg (mean ± SD: 103.2 ± 9.3; median 103.0). Only the diastolic and mean measurements obtained from the pelvic limb met criteria outlined by the American College of Internal Medicine for required accuracy of NIBP monitors. Bias was significantly higher in the thoracic limb in comparison to the pelvic limb and was significantly higher at blood pressures above median. In general, NIBP measurements underestimated IBP measurements. In conclusion, the use of the DRE Waveline Pro to assess NIBP in anesthetized pigs may be useful in monitoring trends in mean and diastolic blood pressure and is most accurate when used on the pelvic limb.

Determination of the minimum alveolar concentration of isoflurane that blunts adrenergic responses in sheep and evaluation of the effects of fentanyl

OBJECTIVE To determine the minimum alveolar concentration that blunts adrenergic responses (MACBAR) for isoflurane and evaluate effects of fentanyl on isoflurane MACBAR in sheep. ANIMALS 13 healthy adult Dorset-cross adult ewes. PROCEDURES In a crossover design, each ewe was anesthetized 2 times for determination of isoflurane MACBAR. Anesthesia was induced with propofol administered IV. Sheep initially received fentanyl (5 μg/kg, IV, followed by a constant rate infusion of 5 μg/kg/h) or an equivalent volume of saline (0.9% NaCl) solution (control treatment). After a washout period of at least 8 days, the other treatment was administered. For MACBAR determination, a mechanical nociceptive stimulus (ie, sponge forceps) was applied at the coronary band for 1 minute. The MACBAR values of the 2 treatments were compared by means of a paired t test. During MACBAR determination, blood samples were collected for measurement of plasma fentanyl concentration. RESULTS Mean ± SD isoflurane MACBAR of the fentanyl and control treatments was 1.70 ± 0.28% and 1.79 ± 0.35%, respectively; no significant difference was found between the 2 treatments. Plasma concentration of fentanyl reached a median steady-state concentration of 1.69 ng/mL (interquartile range [25th to 75th percentile], 1.47 to 1.79 ng/mL), which was maintained throughout the study. CONCLUSIONS AND CLINICAL RELEVANCE Administration of fentanyl at 5 μg/kg, IV, followed by a constant rate infusion of the drug at 5 μg/kg/h did not decrease isoflurane MACBAR. Further studies to determine the effect of higher doses of fentanyl on inhalation anesthetic agents and their potential adverse effects are warranted.