Anesthesia for Patients with Cardiovascular, Respiratory and Gastrointestinal Diseases | VMED 7412, Study notes of Anesthesiology

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Anesthesia: 1 of 8 Veterinary Surgery I, VMED 7412 Patients with Cardiovascular, Respiratory & Gastrointestinal Disease ANESTHESIA FOR PATIENTS WITH CARDIOVASCULAR, RESPIRATORY & GASTROINTESTINAL DISEASES Lyon Lee DVM PhD DACVA Patients with Cardiovascular Diseases General considerations • Most anesthetics produce some degree of cardiovascular depression • The patient with preexisting cardiovascular disease often has reduced cardiac reserve - less ability to compensate for anesthetic-induced depression • Usually patients with compensated cardiovascular disease (that is, not exhibiting any clinical symptoms of their disease) tolerate anesthesia fairly well • The cardiopulmonary system functions to ensure that the rate of delivery of oxygen (DO2) meets or exceeds the consumption of oxygen (VO2) in the whole body (review Cardiopulmonary Physiology lecture) • Effects of anesthetics on the cardiovascular system are o impairment of calcium utilization (inhalants, barbiturates) o alteration of systemic vascular resistance, heart rate, blood pressure o development of intracellular acidosis (secondary to respiratory depression) • Many different types of cardiovascular disease may be encountered o congenital heart disease o acquired valvular disease o significant preexisting arrhythmias o hypotension/hypovolemia o dilated cardiomyopathy o anemia • Primary goals of anesthetic management in these patient groups are to o avoid wide swings in heart rate o minimize changes in preload and afterload o prevent hypovolemia or overhydration o minimize changes in inotropy (myocardial contractility) Anesthesia: 2 of 8 Veterinary Surgery I, VMED 7412 Patients with Cardiovascular, Respiratory & Gastrointestinal Disease Ways to support the cardiovascularly challenged patients • Stabilize heart rate & rhythm prior to anesthesia if possible • Optimize cardiac function prior to anesthesia if possible • Physical examination: observe jugular distension, pulsation, palpate peripheral arterial pulse quality, auscultate heart for assessing characters of pulsation • Thorough cardiac evaluation prior to anesthesia - ECG, Doppler echocardiograph, thoracic radiographs, blood pressure measurement, ultrasonography, cardiac catheterization • Laboratory evaluation - PCV, TP, hemoglobin content, arterial blood gases, electrolytes • Choose anesthetic agents that produce minimal cardiovascular changes and preferably have drugs of short duration of action or that are reversible • Preanesthetics: rely mostly on opioids +/- benzodiazepines: neuroleptanalgesic combination • Anticholinergics are used judiciously • Employ local anesthetic technique under sedation or even general anesthesia • Induction: propofol, etomidate, ketamine, mask with inhalant • Maintenance: usually isoflurane or sevoflurane (rapid recovery and less cardiovascular depression than halothane) • Monitor cardiovascular performance o ECG: rate and rhythm o arterial blood pressure (BP = CO x SVR) o central venous pressure (preload) • Treat arrhythmias if they develop o significant VPC – lidocaine, beta-blockers o significant bradycardia or bradyarrhythmias – glycopyrrolate, atropine, isoproterenol or temporary pace maker implant if medically nonresponsive • Support inotropy with o adrenergic agonists dobutamine dopamine doepxamine ephedrine norepinephrine epinephrine o phophodiesterase inhibitor milrinone amrinone enoximone theophylline pentoxyfylline o calcium channel sensitizer levosimendan pimobendan o digoxin o calcium o glucagon Anesthesia: 5 of 8 Veterinary Surgery I, VMED 7412 Patients with Cardiovascular, Respiratory & Gastrointestinal Disease • minimize oxygen deficit period by allowing rapid intubation and ventilation • Control airway as quickly as possible, begin positive pressure ventilation (esp. with lower airway disease) • Nitrous oxide may be better avoided. o It diffuses into gaseous pocket and worsens symptoms such as pneumothorax o It reduces the inspiratory fraction of oxygen • Monitoring: o ECG o Pulse oximetry o BP o Capnography o Serial blood gas analysis o Tidal volume and peak airway pressure (thoracic compliance) o Temperature • Recovery o Maintain ET tube in situ as long as possible o Post-operative pulse oximetry o Support ventilation as long as possible o Consider post anesthetic oxygen supplementation mask nasal catheter oxygen cage o Minimize stress, judicious use of tranquilizers/sedatives if needed o If acute respiratory obstruction occurs post extubation, be prepared to reinduce anesthesia & reintubate rapidly o Treat chest pain so as to facilitate better use of respiratory muscle Case example 1 • “Jake” • Signalment: 1 year old intact male Labrador retriever • History: presented for evaluation anorexia, listlessness of one week's duration • Significant physical exam findings: tachypnea, fever • Laboratory finding: elevated white blood cell count • Thoracic radiographs: pleural fluid, lung lobe collapse (suspect lung lobe torsion) • Presented for anesthesia 3/27 for thoracic exploratory Preanesthetic management? Anesthetic induction? Maintenance of anesthesia? Monitoring? Postoperative care? Anesthesia: 6 of 8 Veterinary Surgery I, VMED 7412 Patients with Cardiovascular, Respiratory & Gastrointestinal Disease Case example 2 • "Miss Genuines" • Signalment: 1 week old Quarter Horse filly • History: presented for choanal atresia • Significant physical exam findings: normal neonatal foal except for nasal obstruction • Laboratory finding: normal • Referring DVM had performed a tracheostomy shortly after birth • Presented for anesthesia 4/6 for laser surgical correction of choanal atresia Preanesthetic management? Anesthetic induction? Maintenance of anesthesia? Monitoring? Postoperative care? Anesthesia: 7 of 8 Veterinary Surgery I, VMED 7412 Patients with Cardiovascular, Respiratory & Gastrointestinal Disease Patients with Gastrointestinal Diseases General considerations • Variety of disease processes... • Malabsorption • Derangement of electrolytes, acid-base status • hypovolemia • Preoperative stabilization of fluid balance, electrolyte balance important, if possible... Gastric dilitation/volvulus (GDV) • Surgical emergency • Present with: o Respiratory compromise o Cardiovascular compromise o Cardiac dysrhythmias (VPCs, V tach, tachycardia) o Hypotension o Hypoxemia o Acid/base disturbances • If possible, decompress stomach prior to anesthesia • Large volumes of IV fluids rapidly (multiple large bore catheters) at 40-90 ml/kg • Acid/base evaluation helpful • Monitor & treat cardiac dysrhythmias as they present - lidocaine usually first line of defense • Anesthetic management o Preanesthetic: opioids +/- benzodiazepines o Induction: rapid induction to gain control of airway quickly is preferable, initiate positive pressure ventilation may be able to intubate w/ neuroleptanalgesic combination (eg oxymorphone + diazepam) propofol preferred low dose thiopental may be used - but cautiously - potential for aggravating arrhythmias mask induction w/ isoflurane/sevoflurane may be used - but it is still slower o Maintenance isoflurane/sevoflurane supplemental opioids (eg oxymorphone, hydromorphone, fentanyl) IV to reduce inhalant concentration o IPPV usually needed o Monitor cardiovascular system closely ECG Blood pressure