Agreement among anesthesiologists regarding postoperative pain assessment in dogs.

OBJECTIVE: To establish evidence for the validity and reliability of three commonly used pain scales in dogs when assessed by video by specialists in anesthesia. STUDY DESIGN: Mixed-method test-retest observational study. SUBJECTS: A group of six American College of Veterinary Anesthesia and Analgesia board-certified specialists and 31 postoperative dogs. METHODS: The evaluators scored 31 dogs using a visual analogue scale (VAS), numeric rating scale (NRS), and Glasgow pain scale (GPS). The evaluators individually scored the dogs using all three scales together and subsequently, at 3 month intervals, using each of the scales apart. Then, all evaluators in one room reviewed 23 of the videos. A camera was positioned for video and audio recording of discussion about the videos. Intra- and interobserver reliability was determined using a two-way random model intra-class correlation coefficient (ICC). RESULTS: Linear regression indicated a strong correlation among all scales when assigned together (VAS versus NRS, p < 0.0001, R2 = 0.93; VAS versus GPS, p < 0.0001, R2 = 0.59; and NRS versus GPS, p < 0.0001, R2 = 0.61) and apart (VAS versus NRS, p < 0.0001, R2 = 0.68; VAS versus GPS, p < 0.0001, R2 = 0.40; and NRS versus GPS, p < 0.0001, R2 = 0.47). Posture, appearance, vocalization, stiffness, interaction between the animal and a person and response to palpation were identified as important variables for assessing pain. Intra-observer reliability produced average ICC values of 0.90 for VAS, 0.89 for NRS and 0.85 for GPS. Interobserver reliability produced average ICC values when scores were assigned together (VAS: 0.93, NRS: 0.93 and GPS: 0.93) and when done separately (VAS: 0.91, NRS: 0.93 and GPS: 0.95). CONCLUSIONS AND CLINICAL RELEVANCE: The preferred use of the VAS and NRS over the use of the GPS should be cautiously considered for research applications when experts are observers. Revisions of the GPS to clarify descriptors and remove or modify items that may not be associated with pain in dogs should be considered.

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.

Evaluation of an oscillometric blood pressure monitor for use in anesthetized sheep.

OBJECTIVE: To determine the accuracy of an oscillometric blood pressure monitor in anesthetized sheep. STUDY DESIGN: Prospective study. ANIMALS: Twenty healthy adult sheep, 11 males and nine females, weighing 63.6 ± 8.6 kg. METHODS: After premedication with buprenorphine or transdermal fentanyl, anesthesia was induced with ketamine-midazolam and maintained with isoflurane and ketamine, 1.2 mg kg(-1) hour(-1), ± lidocaine, 3 mg kg(-1) hour(-1). Invasive blood pressure measurements were obtained from an auricular arterial catheter and noninvasive measurements were from a cuff on the metatarsus or antebrachium. Simultaneous invasive and noninvasive measurements were recorded over a range (55-111 mmHg) of mean arterial pressures (MAP). Isoflurane concentration was increased to decrease MAP and decreasing the isoflurane concentration and infusing dobutamine achieved higher pressures. Invasive and noninvasive measurements were compared. RESULTS: Correlation (R(2)) was good between the two methods of measurement (average of three consecutive readings) for systolic (SAP) (0.87), diastolic (DAP) (0.86), and mean (0.90) arterial pressures (p < 0.001). Bias ± SD between noninvasive and invasive measurements for SAP was 3 ± 8 mmHg, for DAP was -10 ± 7 mmHg, and MAP was -7 ± 6 mmHg. There was no significant difference between the average of three measurements and use of the first measurement. Correlations using the first measurement were SAP (0.82), DAP (0.84), and MAP (0.89). Bias ± SD for SAP was 3 ±10 mmHg, for DAP was -11 ± 7 mmHg, and MAP was -7 ± 6 mmHg. The oscillometric monitor slightly overestimated SAP and underestimated DAP and MAP for both average values and the first reading. CONCLUSIONS AND CLINICAL RELEVANCE: This oscillometric model provided MAP measurements that were acceptable by ACVIM standards. MAP measurements with this monitor were lower than those found with the invasive technique so a clinical diagnosis of hypotension may be made in sheep that are not hypotensive.

Anesthetic agents and complications in Vietnamese potbellied pigs: 27 cases (1999-2006).

OBJECTIVE: To document complications associated with preanesthetic and anesthetic agents used in Vietnamese potbellied pigs and identify predictors of complications. DESIGN: Retrospective case series. ANIMALS: 27 potbellied pigs (14 female and 13 male) ranging in age from 0.25 to 15 years old and ranging in body weight from 5.9 to 169 kg (13.0 to 371.8 lb) that were anesthetized on 32 occasions between 1999 and 2006. PROCEDURES: Data, including perianesthetic management, anesthetic agents and dosages, complications, and outcome, were retrieved from medical records. Patient information, anesthetic agents, and duration of anesthesia were evaluated as predictors for development of complications. RESULTS: Anesthesia was maintained with isoflurane or sevoflurane during 30 anesthetic episodes. Commonly used premedicants were butorphanol, atropine, and midazolam administered in combination with xylazine or medetomidine and a combination of tiletamine-zolazepam and butorphanol. Anesthesia was induced with an inhalation agent on 15 occasions, via injection of ketamine on 10 occasions, and via injection of propofol on 3 occasions. Complications included hypoventilation (16/24 [67%]), hypotension (16/25 [64%]), hypothermia (15/31 [48%]), bradycardia (9/32 [28%]), and prolonged recovery time (7/32 [22%]). None of the factors evaluated were associated with development of these complications. All pigs survived anesthesia. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that a variety of anesthetic agent combinations can be used to provide anesthesia in potbellied pigs with satisfactory outcomes. Although there were high incidences of hypoventilation, hypotension, and hypothermia, no specific anesthetic agent was associated with development of these complications.

Effects of changing body position on oxygenation and arterial blood pressures in foals anesthetized with guaifenesin, ketamine, and xylazine.

OBJECTIVE: To investigate the impact of a change in body position on blood gases and arterial blood pressures in foals anesthetized with guaifenesin, ketamine, and xylazine. STUDY DESIGN: Prospective, randomized experimental study. ANIMALS: Twelve Quarter Horse foals, age of 5.4 +/-0.9 months and weighing 222 +/- 48 kg. METHODS: Foals were anesthetized with guaifenesin, ketamine, and xylazine for 40 minutes in lateral recumbency and then assigned to a change in lateral recumbency after hoisting (Group 1, n = 6), or no change (Group 2, n = 6). Oxygen 15 L minute(-1) was insufflated into the endotracheal tube throughout anesthesia. Arterial blood pressure, heart rate, respiratory rate (f(R)), inspired fraction of oxygen (FIO(2)), and end-tidal carbon dioxide (PE'CO(2)) were measured every 5 minutes. Arterial pH and blood gases [arterial partial pressure of oxygen (PaO(2)), arterial partial pressure of carbon dioxide (PaCO(2))] were measured at 10, 30, and 40 minutes after induction, and 5 minutes after hoisting. Alveolar dead space ventilation and PaO(2)/FIO(2) were calculated. Two repeated measures models were used. All hypothesis tests were two-sided and significance level was alpha = 0.05. All values are presented as least square means +/- SE. RESULTS: Values at time-matched points from the two groups were not significantly different so they were combined. Arterial partial pressure of oxygen decreased significantly from 149 +/- 14.4 mmHg before hoisting to 92 +/- 11.6 mmHg after hoisting (p = 0.0013). The PaO(2)/FIO(2) ratio decreased from 275 +/- 30 to 175 +/- 24 (p = 0.0055). End-tidal carbon dioxide decreased significantly from 48.7 +/- 1.6 to 44.5 +/- 1.2 mmHg (p = 0.021). Arterial partial pressure of carbon dioxide, blood pressures and heart rates measured 5 minutes after hoisting were not different from measurements obtained before hoisting. CONCLUSION AND CLINICAL RELEVANCE: Hoisting decreased PaO(2) in anesthetized healthy foals. Administration of supplemental oxygen is recommended to counter the decrease in oxygenation and PaO(2) measurement is necessary to detect early changes.

Effect of butorphanol administration on cardiovascular parameters in isoflurane-anesthetized horses - a retrospective clinical evaluation.

OBJECTIVE: To determine cardiovascular responses to administration of butorphanol in isoflurane-anesthetized horses. STUDY DESIGN: Retrospective evaluation of anesthetic records. ANIMALS: Seventy-six horses anesthetized for a variety of clinical surgical procedures. METHODS: Anesthetic records of clinical equine patients anesthetized between January 1999 and December 2003 were searched. The records were reviewed for horses in which anesthesia was induced with ketamine and a benzodiazepine and maintained with isoflurane, and horses that received butorphanol intraoperatively. Exclusion criteria included horses in which the rate of infusion of an inotrope or end-tidal isoflurane concentration was changed 10 minutes before or after the butorphanol bolus. The horses were separated into two groups: group 1 horses received butorphanol at intervals as part of a balanced protocol, group 2 horses had > or = 10% increase in heart rate (HR) or blood pressure within 10 minutes prior to butorphanol administration. RESULTS: Eighty-nine butorphanol administration events matched the criteria for inclusion, 49 in group 1 and 40 in group 2. There were no significant changes after butorphanol administration in systolic arterial pressure (SAP), mean arterial pressure (MAP), diastolic arterial pressure (DAP), and heart rate (HR) in group 1, or in end-tidal carbon dioxide concentration or hemoglobin oxygen saturation in either group. There were significant decreases in SAP (p < 0.0001), MAP (p < 0.0005), and DAP (p < 0.0008) after butorphanol administration in group 2. CONCLUSIONS AND CLINICAL RELEVANCE: The results presented here confirm that butorphanol can be administered to horses during isoflurane anesthesia without adverse effects on HR and arterial blood pressure. The results imply that butorphanol can deepen the plane of anesthesia and obtund sympathetic stimulation from a surgical procedure.

Acute pulmonary edema after diazepam-ketamine in a dog.

An 8-year-old mixed-breed dog was anesthetized for colonoscopy. Moderate sedation was produced by premedication with glycopyrrolate, acepromazine, and hydromorphone, and anesthesia was induced by IV injection of diazepam and ketamine. Frothy, reddish-colored fluid flowed from the endotracheal tube immediately after endotracheal intubation but ceased after several minutes. Furosemide was injected IV. Anesthesia was maintained by sevoflurane in oxygen. Ventilation and arterial blood pressure were satisfactory, however, after oxygen was administered to maintain normal hemoglobin saturation. Radiography revealed changes consistent with a diagnosis of pulmonary edema. The following day, ventricular premature contractions developed and atrial dissociation, valvular regurgitation, and pulmonary hypertension were diagnosed on echocardiography. The proposed etiology is either profound transient hypotension and/or pulmonary hypertension induced by ketamine. The cardiac abnormalities that were present the following day suggest that myocardial dysfunction after induction of anesthesia was more severe than was apparent as assessed by routine physical examination and monitoring methods.

Traumatic endotracheal intubation in the cat.

BACKGROUND: Orotracheal intubation is a commonly performed procedure in the cat, but it is not without complications. Tracheal rupture has been reported in cats, but trauma to the arytenoids from intubation has not been documented. OBSERVATIONS: An otherwise healthy, 5-year-old male domestic shorthair cat presented for total ear canal ablation to resolve intractable otitis media and externa. The cat was premedicated with glycopyrrolate, hydromorphone, and acepromazine. Anesthesia was induced with diazepam and ketamine, and maintained with isoflurane in oxygen. During orotracheal intubation, the larynx was poorly visualized and excessive force was used to perform intubation. Subsequently, blood was observed in the larynx and laryngoscopy revealed a tear lateral to the patient's right arytenoid which had been created during intubation. The larynx was re-intubated normally and the cat suffered no obvious ill effects from the trauma to the larynx. CONCLUSIONS: Direct observation and proper technique must be employed during orotracheal intubation in cats in an attempt to avoid laryngeal trauma.

Cardiopulmonary effects of controlled versus spontaneous ventilation in pigeons anesthetized for coelioscopy.

OBJECTIVE: To evaluate the cardiorespiratory effects of controlled versus spontaneous ventilation in pigeons anesthetized for coelioscopy. DESIGN: Prospective study. ANIMALS: 30 healthy adult pigeons (Columbia livia). PROCEDURE: During isoflurane anesthesia, 15 pigeons were allowed to breathe spontaneously (SP group) and 15 were mechanically ventilated (MV group) by use of a pressure-limited ventilator. In each group, cardiopulmonary variables (including end-tidal CO2 concentration [ETCO2]) were measured before (baseline), during, and after coelioscopy. An arterial blood sample was collected for blood gas analyses from each pigeon before coelioscopy and after the procedure, when the caudal thoracic air sac was still open. RESULTS: At baseline, hypoventilation was greater in the SP group than the MV group. Compared with the SP group values, ETCO2 overestimated PaCO2 to a greater degree in the MV group. Cardiovascular variables were not different between groups. After coelioscopy (when the air sac was open), PaCO2 had decreased significantly from baseline in the MV group. In the SP group, hypoventilation worsened despite an increase in respiratory rate. After coelioscopy, PaO2 in the SP group had decreased from baseline and was lower than PaO2 in the MV group; arterial blood pressure and heart rate in the MV group had decreased from baseline and were lower than values in the SP group. CONCLUSIONS AND CLINICAL RELEVANCE: In adult pigeons, controlled ventilation delivered by a pressure-limited device was not associated with clinically important adverse cardiopulmonary changes but may be associated with respiratory alkalosis and cardiovascular depression when air sac integrity has been disrupted.

The effects of two endotracheal tube cuff inflation pressures on liquid aspiration and tracheal wall damage in horses.

OBJECTIVE: To investigate the effect of endotracheal tube cuff inflation pressure on the occurrence of liquid aspiration and tracheal wall damage. STUDY DESIGN: Prospective, randomized experimental study. ANIMALS: Ten healthy horses, weighing 535 +/- 55 kg. METHODS: Horses were anesthetized, orotracheally intubated, placed in dorsal recumbency, and maintained on isoflurane in oxygen with controlled ventilation for 175 +/- 15 minutes. The horses were randomly assigned to an endotracheal cuff pressure of 80-100 or 120 cm H2O. The cuff pressure was continuously monitored and maintained at a constant pressure. Methylene blue in saline was instilled proximal to the cuff. After euthanasia, the trachea was opened distal to the endotracheal tube tip to check for evidence of dye leaking past the cuff. The cervical trachea was then resected and opened longitudinally for gross and histologic examinations. RESULTS: No blue staining was found distal to the cuff in any horse. Visual examination of the tracheal mucosa revealed hyperemic and hemorrhagic lesions at the site of the cuff contact. Histologic changes included epithelium attenuation or erosion, submucosal neutrophilic infiltration, and submucosal hemorrhages. Lesions were absent or less extensive in the lower cuff pressure group as compared to the high cuff pressure group. CONCLUSIONS: The endotracheal tube cuff produced a seal sufficient to prevent leakage in both groups. Tracheal wall damage was more severe and occurred more frequently in the higher cuff pressure group. CLINICAL RELEVANCE: Tracheal mucosal damage induced by cuff inflation is pressure-dependent. Cuff pressure monitoring is recommended.