Jane E. Quandt

Comparison of three different inhalant anesthetic agents (isoflurane, sevoflurane, desflurane) in red‐tailed hawks (Buteo jamaicensis)

OBJECTIVE To compare isoflurane, sevoflurane and desflurane for inhalant anesthesia in red-tailed hawks (Buteo jamaicensis) in terms of the speed and characteristics of induction; cardiovascular and respiratory parameters while anesthetized; and speed and quality of recovery. STUDY DESIGN Prospective, cross over, randomized experimental study. ANIMALS 12 healthy adult red-tailed hawks. METHODS Anesthesia was induced with isoflurane, sevoflurane or desflurane in oxygen via face mask in a crossover, randomized design with a 1 week washout period between each treatment. Hawks were tracheally intubated, allowed to breathe spontaneously, and instrumented for cardiopulmonary monitoring. Data collected included heart rate, respiratory rate, end-tidal CO(2) , inspired and expired agent, SpO(2,) temperature, systolic blood pressure, time to intubation and time to recovery (tracking). Recovery was subjectively scored on a 4 point scale as well as a summary evaluation, by a single blinded observer. RESULTS No significant difference in time to induction and time to extubation was noted with the administration of isoflurane, sevoflurane or desflurane. Time to the ability of the bird to follow a moving object with its eyes (tracking) was significantly faster with the administration of sevoflurane and desflurane. All recoveries were scored 1 or 2 and were assessed as good to excellent. No significant difference was noted in heart rate, blood pressure and temperature among the three inhalants. Administration of isoflurane resulted in lower respiratory rates. CONCLUSIONS AND CLINICAL RELEVANCE Overall, although isoflurane remains the most common inhaled anesthetic in avian practice, sevoflurane and desflurane both offer faster time to tracking, while similar changes in cardiopulmonary function were observed with each agent during anesthesia of healthy red-tailed hawks.

Anesthetic considerations for laser, laparoscopy, and thoracoscopy procedures

Laser surgery and laparoscopy are two relatively new surgical techniques gaining popularity in veterinary medicine, which require special consideration when being performed on the anesthetized patient. For laser surgery, consideration must be given to the possibility of atmospheric contamination, inappropriate energy transfer, eye injury, perforation of a vessel or anatomic structure, perforation of the endotracheal tube, and fire. The primary concern with laparoscopy and thoracoscopy is the creation of a pneumoperitoneum or pneumothorax, which can result in (1) hypercarbia and inadequate ventilation, (2) poor cardiac output and systemic blood pressure, and (3) gas embolism. To minimize complications, patients should be placed on positive pressure ventilation, be well hydrated before and during the procedure, and be thoroughly monitored (ECG, capnography, pulse oximetry.

The use of vasopressin for treating vasodilatory shock and cardiopulmonary arrest.

OBJECTIVE To discuss 3 potential mechanisms for loss of peripheral vasomotor tone during vasodilatory shock; review vasopressin physiology; review the available animal experimental and human clinical studies of vasopressin in vasodilatory shock and cardiopulmonary arrest; and make recommendations based on review of the data for the use of vasopressin in vasodilatory shock and cardiopulmonary arrest. DATA SOURCES Human clinical studies, veterinary experimental studies, forum proceedings, book chapters, and American Heart Association guidelines. HUMAN AND VETERINARY DATA SYNTHESIS: Septic shock is the most common form of vasodilatory shock. The exogenous administration of vasopressin in animal models of fluid-resuscitated septic and hemorrhagic shock significantly increases mean arterial pressure and improves survival. The effect of vasopressin on return to spontaneous circulation, initial cardiac rhythm, and survival compared with epinephrine is mixed. Improved survival in human patients with ventricular fibrillation, pulseless ventricular tachycardia, and nonspecific cardiopulmonary arrest has been observed in 4 small studies of vasopressin versus epinephrine. Three large studies, though, did not find a significant difference between vasopressin and epinephrine in patients with cardiopulmonary arrest regardless of initial cardiac rhythm. No veterinary clinical trials have been performed using vasopressin in cardiopulmonary arrest. CONCLUSION Vasopressin (0.01-0.04 U/min, IV) should be considered in small animal veterinary patients with vasodilatory shock that is unresponsive to fluid resuscitation and catecholamine (dobutamine, dopamine, and norepinephrine) administration. Vasopressin (0.2-0.8 U/kg, IV once) administration during cardiopulmonary resuscitation in small animal veterinary patients with pulseless electrical activity or ventricular asystole may be beneficial for myocardial and cerebral blood flow.

Use of a wireless system to measure invasive arterial blood pressure in ponies – preliminary study

OBJECTIVE To evaluate the feasibility and functionality of intra-carotid wireless device implantation in ponies, and to investigate its short-term complications. STUDY DESIGN Prospective preliminary study. ANIMALS Five mixed breed, adult, intact male ponies weighing 104 +/- 28.8 kg (mean +/- SD) underwent surgery. Arterial blood pressure data were continuously collected from four animals. METHODS General anesthesia was induced on two consecutive days. On the first day, an intra-arterial wireless device was implanted in the right carotid artery. On the next day, a transcutaneous intra-arterial catheter was placed in the left facial artery. Data from both sources were collected. Post-mortem examination was performed. RESULTS Surgical time was 27.1 +/- 11.85 minutes. All catheters remained in place with some extra vascular migration. Complications included mild seroma and hematoma. CONCLUSION The wireless system allowed continuous monitoring in ponies throughout anesthesia and at rest and may allow for the recording of arterial blood pressure and heart rate when it would be difficult to achieve with a conventional system (e.g. during recovery from anesthesia). CLINICAL RELEVANCE The wireless invasive blood pressure monitor may allow continuous measurements when only intermittent measurements would be feasible with a wired system.

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 of Tensile Strength and Early Healing of Acute Repeat Celiotomy Through a Ventral Median or a Right Ventral Paramedian Approach

OBJECTIVE To compare tensile strength, failure location, and histologic features after acute repeat celiotomy through a ventral median (RVM) or a right ventral paramedian (RVP) celiotomy in horses. STUDY DESIGN Ex vivo experimental study. ANIMALS Adult horses (N = 18). METHODS Twelve adult horses had original ventral median (OVM) celiotomy. Repeat celiotomy was performed 72 hours postoperatively through the original ventral median (RVM, N = 6) or a RVP (N = 6) celiotomy. Celiotomies were scored daily for edema, drainage, and dehiscence. Fourteen days after repeat celiotomy, horses were euthanatized and abdominal wall containing celiotomy(ies) were collected for biomechanical and histological evaluation. The abdominal wall of control horses (N = 6; no celiotomy) was collected for biomechanical testing. Vital sign variables, incisional edema, and histologic scores were compared using a Wilcoxon signed-rank test. Incisional fibrotic depth and tensile strength per unit length (N/cm) was compared using repeated measures ANOVA. RESULTS RVM and RVP horses had significantly less tensile strength compared to control horses, but no differences were observed between RVM and RVP horses. No differences in healing, inflammation, infection, or necrosis of repeat celiotomies was observed, but RVP horses accumulated more fibrin and hemorrhage within the incision. RVP horses had significantly greater incisional edema scores, but incisional drainage was more frequent in RVM horses. CONCLUSIONS Acute repeat celiotomy through a RVM incision results in similar incisional healing and tensile strength compared with repeat celiotomy through a RVP incision.

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.

A survey of the use of arterial catheters in anesthetized dogs and cats: 267 cases

OBJECTIVES To describe the clinical practice of insertion of arterial catheters in anesthetized dogs and cats, to document complications of arterial catheterization, and to determine risk factors associated with the complications. DESIGN Prospective clinical study and retrospective evaluation of medical records. SETTING University teaching hospital. ANIMALS Dogs (n = 251) and 13 cats anesthetized for clinical procedures with arterial catheters inserted for blood pressure monitoring. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS Details of the animal and catheter were collected at the time of anesthesia. On the following day, the catheter site was palpated and observed for abnormalities and the medical records of all animals were reviewed retrospectively for complications. Details of catheter placement were available for 216 catheters: 158 catheters in a dorsal pedal artery, 50 catheters in the median caudal (coccygeal) artery, 6 in the median artery, and 1 each in a cranial tibial and lingual artery. Blood pressure was obtained from 200 catheters, and 12 catheters failed before the end of anesthesia. Postoperative observational data obtained from 112 catheters described a palpable arterial pulse at 73 sites and no pulse at 21 sites. No risk factor for arterial occlusion was identified. No complications resulting from arterial catheterization were noted in the medical records. CONCLUSIONS Arterial catheterization resulted in loss of a peripheral pulse postoperatively in 21/94 (22.3%) of animals examined, although no evidence of tissue ischemia was noted in the medical records of any of the patients in this study. These results suggest that insertion of a catheter in the dorsal pedal or coccygeal arteries was not associated with a high risk for complications. However, the course of arterial occlusion postoperatively warrants further investigation.Objectives To describe the clinical practice of insertion of arterial catheters in anesthetized dogs and cats, to document complications of arterial catheterization, and to determine risk factors associated with the complications. Design Prospective clinical study and retrospective evaluation of medical records. Setting University teaching hospital. Animals Dogs (n = 251) and 13 cats anesthetized for clinical procedures with arterial catheters inserted for blood pressure monitoring. Interventions None. Measurements and Main Results Details of the animal and catheter were collected at the time of anesthesia. On the following day, the catheter site was palpated and observed for abnormalities and the medical records of all animals were reviewed retrospectively for complications. Details of catheter placement were available for 216 catheters: 158 catheters in a dorsal pedal artery, 50 catheters in the median caudal (coccygeal) artery, 6 in the median artery, and 1 each in a cranial tibial and lingual artery. Blood pressure was obtained from 200 catheters, and 12 catheters failed before the end of anesthesia. Postoperative observational data obtained from 112 catheters described a palpable arterial pulse at 73 sites and no pulse at 21 sites. No risk factor for arterial occlusion was identified. No complications resulting from arterial catheterization were noted in the medical records. Conclusions Arterial catheterization resulted in loss of a peripheral pulse postoperatively in 21/94 (22.3%) of animals examined, although no evidence of tissue ischemia was noted in the medical records of any of the patients in this study. These results suggest that insertion of a catheter in the dorsal pedal or coccygeal arteries was not associated with a high risk for complications. However, the course of arterial occlusion postoperatively warrants further investigation.

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.

The effect of midazolam on the recovery quality, recovery time and the minimum alveolar concentration for extubation in the isoflurane-anesthetized pig

There are no reported studies evaluating the effect of midazolam on recovery quality, recovery time or minimum alveolar concentration (MAC) at which extubation occurs (MACextubation). Our hypotheses were that midazolam administered prior to recovery would decrease MACextubation, prolong recovery time but provide a smoother recovery. Sixteen Yorkshire pigs were anesthetized with isoflurane for approximately 5 h. The end-tidal isoflurane concentration was then stabilized at 1.4% for 20 min. Pigs were randomly assigned to receive midazolam or saline. The vaporizer was decreased by 10% every 10 min until extubation. Pigs were declared awake by a blinded observer and were assigned a recovery score by the same observer. Mean MACextubation was not significantly different for pigs receiving saline prior to recovery compared with those pigs receiving midazolam. The overall mean MACextubation for both groups was 0.6 ± 0.4 vol%. Time to extubation was not significantly longer with midazolam (124 ± 36 min) compared with the saline group (96 ± 61 min; P = 0.09). Recovery score was not significantly different between groups (midazolam, 0.86 ± 1.1; saline 0.5 ± 0.5; P = 0.26). In conclusion, midazolam did not affect MACextubation. There was no advantage of administering midazolam in the recovery period when performing step-down titration of isoflurane anesthesia.