A 9-year-old 31-kg castrated male mixed-breed dog was referred to the Veterinary Teaching Hospital of the University of Bologna for treatment of a 4 X 4-cm splenic mass incidentally identified by the referral veterinarian. The dog was otherwise healthy; its past medical history was unremarkable. On presentation, cardiac auscultation revealed an irregular heart rhythm with a heart rate of 80 to 120 beats/ min. The femoral pulses were strong and synchronous with the heartbeat. The remaining physical findings were normal. Preanesthetic screening included routine blood tests (CBC, serum biochemical panel, and restricted coagulation panel) and thoracic radiography, which yielded unremarkable results. A 6-lead ECG was obtained (Figure 1). ECG InterpretationAn irregular rhythm with a mean heart rate of 120 beats/min was present. Narrow QRS complexes (duration, 0.07 seconds) with normal morphology and mean electric axis (89°) were evident. Two distinct P-wave configurations coexisted. The first configuration was characterized by P waves of normal amplitude (0.15 mV), duration (0.04 seconds), and axis (72°). They were constantly associated with a QRS complex and normal PQ interval (0.11 seconds). On the basis of these features, they were considered sinus in origin. The second configuration included smaller P' waves (amplitude, 0.05 mV; duration, 0.025 seconds) with a fast and irregular coupling interval (0.18 to 0.22 seconds). They occurred independently from the QRS complexes and were occasionally superimposed on the QRS complexes, T waves, and sinus P waves. The P' waves were almost isoelectric in lead I, positive in the inferior leads, and negative in the remaining leads, suggesting an atrial vector with a superior-to-inferior direction. 1 Given these findings, atrial dissociation (AD) was diagnosed. [1][2][3][4][5] The dissociated rhythm was suspected to be atrial tachycardia arising from an atrial roof ectopic focus. 1 In light of the ECG abnormality, transthoracic echocardiography was performed to further explore the dog's cardiac status. Cardiac dimensions and functional parameters were normal, and no valvular insufficiency was found. Intriguingly, 2-D and M-mode analysis through the mitral valve revealed simultaneous leaflet opening with the P' waves. Additionally, pulsed-wave Doppler ultrasonographic interrogation of the mitral inflow documented abnormal diastolic waves induced by P' waves (Figure 2). These findings were judged to be caused by abnormal active atrial contractions mediated by dissociated P' waves. 2,5,6 On the basis of previous veterinary reports describing AD in dogs as a benign entity, 2-5 the dog underwent splenectomy on the same day.For the anesthetic procedure, a multiparameter monitor (Datex Ohmeda S5; GE Healthcare) was used to monitor the dog's cardiac rhythm. The dog was sedated with acepromazine (10 µg/kg, IM), dexmedetomidine (1 µg/kg, IM), and methadone (0.2 mg/ kg, IM). Ten minutes after premedication, AD with a slow ventricular response rate (minimum heart rate, 45 beats/min) was stil...

Surgery-induced stress and anesthesia-related immunosuppression are believed to play a critical role in human oncology patients. Studies have hypothesized that anesthesia influences patients' outcome, promoting tumor recurrence and metastasis. Aim of the study was to investigate whether anesthesia promoted relapse in dogs with diffuse large B-cell lymphoma (DLBCL). Medical records were searched for dogs with DLBCL, that were in complete remission (CR) after the same chemo-immunotherapy protocol. Dogs receiving anesthesia were included if the procedure was performed while in CR. Time to relapse (TTR) was obtained via Kaplan–Meier method. Association between anesthesia and relapse was assessed using a nested case-control design and estimated using conditional logistic regression. Sixty-one dogs with DLBCL were included. Overall median TTR was 329 days (95% CI, 281–377). Forty-eight (79%) dogs relapsed during the study period, while 13 (21%) were still in CR at data analysis closure. Eighteen (30%) dogs received anesthesia with opioids, propofol, and isoflurane or sevoflurane. The relative risk of lymphoma relapse for dogs undergoing anesthesia was significantly higher compared with dogs not undergoing anesthesia, with an odds ratio of 3.09 (P = 0.019) on multivariable analysis. Anesthesia may promote relapse in dogs with DLBCL treated with chemo-immunotherapy, although a role of perioperative stress cannot be ultimately excluded. Considering the high frequency of anesthetic procedures required for diagnostic and therapeutic protocols among oncology patients, it is of utmost interest to characterize the effects of single anesthetic agents on the immune system. Further prospective studies are needed to better define the impact of anesthesia on patients' outcome.