Farhan Sheikh

Low systemic vascular resistance during cardiac surgery: Case reports, brief review, and management with angiotensin II

C LINICIANS HAVE observed patients who, despite having an adequate cardiac output (CO), develop profound hypotension subsequent to separation from hypothermic cardiopulmonary bypass (CPB). The hypotension is associated with a low systemic vascular resistance (SVR), which may be refractory to traditional a-adrenergic agonist therapy. Two cases are described in which such a low SVR state was successfully treated using a non-a-agonist vasopressor, angiotensin.

Effect of hemorrhagic shock and reperfusion on the respiratory quotient in swine.

OBJECTIVES Respiratory quotient, the ratio of CO2 production to oxygen consumption (VO2), is principally affected by the fuel source used for aerobic metabolism. Since the respiratory quotient, VO2, and CO2 production cannot be directly measured easily, indirect calorimetry is commonly used to determine the value of these variables at the airway level (i.e., airway respiratory quotient, airway VO2, and airway CO2 production). However, under nonsteady-state conditions, a variety of phenomena can alter the relationship between true metabolic activity and measurements determined by indirect calorimetry. During exercise, for example, airway respiratory quotient increases as anaerobic threshold is reached because of the disproportionate increase in airway CO2 production that results from the CO2 liberated through the buffering of excess hydrogen ions by bicarbonate. We hypothesized that hemorrhage and reinfusion might change airway respiratory quotient in a consistent manner as shock is produced and reversed. DESIGN Prospective laboratory study. SETTING University animal laboratory. SUBJECTS Eight pigs (25 +/- 2 [SD] kg), anesthetized with fentanyl and relaxed with pancuronium bromide, and mechanically ventilated on room air. INTERVENTIONS The animals were sequentially hemorrhaged and then autotransfused while metabolic and hemodynamic measurements were obtained, using continuous indirect calorimetry and continuous applications of the Fick principle. Hemoglobin, arterial lactate concentration, and blood gases for calibration were measured serially. Analysis of variance was used to compare various periods in time. MEASUREMENTS AND MAIN RESULTS Between baseline and peak hemorrhage, and between peak hemorrhage and postreinfusion, all of the following variables changed significantly (p < .05): airway VO2 (baseline 6.4 +/- 0.9 mL/min/kg, peak hemorrhage 3.9 +/- 0.6 mL/min/kg, postreinfusion 7.0 +/- 1.4 mL/min/kg); airway CO2 production (baseline 5.5 +/- 0.9 mL/min/kg, peak hemorrhage 4.5 +/- 0.9 mL/min/kg, postreinfusion 6.0 +/- 1.4 mL/min/kg); airway respiratory quotient (baseline 0.87 +/- 0.07, peak hemorrhage 1.16 +/- 0.07, postreinfusion 0.87 +/- 0.05); lactate concentration (baseline 2.4 +/- 1.2 mmol/L, peak hemorrhage 6.7 +/- 1.9 mmol/L, postreinfusion 5.1 +/- 2.0 mmol/L); and delta PCO2 (venous PCO2-PaCO2) (baseline 4.5 +/- 3.6 torr [0.6 +/- 0.5 kPa], peak hemorrhage 12.1 +/- 5.3 torr [1.6 +/- 0.7 kPa], postreinfusion 2.7 +/- 2.7 torr [0.4 +/- 0.4 kPa]). CONCLUSIONS Airway respiratory quotient increases in hemorrhagic shock and decreases again as shock is reversed during reinfusion. This phenomenon appears related to the buffering of excess of hydrogen ion during hemorrhagic shock.

Recognition and management of patients with antiphospholipid antibody syndrome undergoing cardiac surgery

A NTIPHOSPHOLIPID antibody (APA), a condition that occurs in 2% 1 of the population, may result in a hypercoagulable state. If not recognized, it may increase perioperative morbidity and mortality in patients undergoing cardiac surgery. Antiphospholipid antibodies have been detected in 46% of patients with stroke or transient ischemic attack under age 50 years, 2 and have been reported in 21% of young survivors (younger than 45 years) of myocardial infarction. 3 Their detection and management, therefore, are of considerable clinical significance because a high risk of recurrent thrombosis exists. Two patients who had antiphospholipid antibodies and required cardiac surgery are presented. In case 1, the diagnosis of APA was not made preoperatively. In case 2, the patient was admitted with an established diagnosis of APA.

Management of the parturient with severe aortic incompetence

S YMPTOMATIC aortic insufficiency is infrequent during childbearing years. Because symptoms of aortic insufficiency usually develop during the fourth and fifth decades of life, most pregnant patients with dominant aortic insufficiency have uneventful pregnanoes. Although infrequent, together with aortic stenosis and mitral regurgitation, they account for up to 10% to 35% of all obstetric cardiac cases. The physiologic changes of pregnancy should actually improve forward flow. With pregnancy there is a decrease m systemic vascular resistance and an increase in heart rate; both of which may reduce both the regurgitant flow across the aortic valve as well as the intensity of the murmur of insufficiency. 1,2 Although these changes should improve forward flow, the increase in intravascular volume observed throughout pregnancy associated with the increase m systemic vascular resistance associated with the stress of labor and delivery can lead to left ventricular dysfunction. The anesthetic management of the critically ill patient with aortic insufficiency in labor and in the postpartum period is reported here.

Right Heart Reconstruction Following Repair of Tetralogy of Fallot

Ten patients in whom tetralogy of Fallot had been repaired underwent late reconstruction of the outflow tract of the right ventricle because of poor hemodynamic results. The major hemodynamic problems that necessitated right ventricular (RV) outflow tract reconstruction were severe pulmonary insufficiency in 9 patients and pulmonary stenosis in 1. Impaired RV contractility and RV aneurysm were the most important factors prompting valve replacement for severe pulmonary insufficiency. Seven patients received a Hancock prosthesis and 3, an aortic homograft. Among the 7 patients who underwent postoperative cardiac catheterization, the surgical results were hemodynamically excellent in 2, good in 3, and unsatisfactory in 2. The management of pulmonary insufficiency in such patients is discussed.

The use of angiotensin II to treat profound hypotension in a patient taking amiodarone

A MIODARONE, a class III antiarrhythmic agent, has been implicated as a cause of cardiovascular instability during anesthesia.is3 Two major side effects of amiodarone include bradyarrhythmias and low systemic vascular resistance (SVR). Profound hypotension can sometimes result from either of these side effects. Electrical pacing is the treatment of choice for the dysrhythmia, and angiotensin may be the drug of choice for treating the low SVR.’ A patient taking amiodarone before cardiac surgery is reported. An angiotensin infusion was used to reverse marked hypotension that developed during cardiopulmonary bypass (CPB), and was continued to wean the patient from CPB and to maintain an adequate SVR in the postCPB period.

Cardiovascular collapse and refractory bronchospasm following administration of vancomycin, esmolol, and heparin

A case is presented in which cardiovascular collapse and refractory bronchospasm requiring rapid institution of cardiopulmonary by pass occurred following the infusion of vancomycin

Double internal jugular vein cannulation in adult patients utilizing a single venipuncture.

In his review, “The Clinical Use of Premedicants” (Anesth Analg 1986;65:963-74), Dr. Paul F. White’s incorrect terminology of hydroxyzine not having received ”official approval” from the Food and Drug Administration for intravenous use could be misleading to anesthesiologists. In this age of overzealous attorneys and pharmacy directors, it is notable that the publishers of the Physicians’ Desk Reference and the AMA have attempted to resolve this concern and confusion among practitioners (1,2). In addition, the FDA Drug Bulletin states “The FD&C Act does not, however, limit the manner in which a physician may use an approved drug. Once a product has been approved for marketing, a physician may prescribe it for uses or in treatment regimens or patient populations that are not included in approved labeling. Such ’unapproved’ or, more precisely, ’unlabeled’ uses may be appropriate and rational in certain circumstances, and may, in fact, reflect approaches to drug therapy that have been extensively reported in medical literature (3).” This clarification is important to anesthesiologists, who commonly use drugs for unlabeled uses (curare for defasciculation, lidocaine for modification of the stress response to tracheal intubation, nitroglycerine ointment as a topical venodilator) and in unlabeled routes (rectal methohexital, intravenous methadone, epidural fentanyl). As there is little financial motivation to apply to the FDA to broaden the indications for a generically available preparation, we should not expect product literature to keep pace with our ever improving therapeutic ability.

Anesthetic management for myocardial revascularization following bleomycin chemotherapy.

B LEOMYCIN (BLM) is a glycoprotein antibiotic synthesized from Streptomyces verticillus that is highly effective against malignancies such as lymphomas, dysgenetic testicular tumors, and squamous cell carcinomas. It is often used in conjunction with other agents because of its low potential for bone marrow suppression or immunosuppression, thereby enhancing the antineoplastic effect at the cost of fewer side effects.’ Pulmonary toxicity that presents as an interstitial pneumonitis that may progress to fibrosis is its major side effect.* Patients more than 65 years of age and those with persisting pulmonary pathology are especially at risk. Pulmonary fibrosis occurs in 3% of patients receiving BLM. A hypersensitivity pneumonitis and fulminant respiratory failure can also occur.3 Asymptomatic changes in pulmonary function that may be construed as milder forms of toxicity are probably more common.4,5 Radiation to the chest and oxygen therapy are believed to potentiate BLM pulmonary toxicity. A high or even modestly elevated F,02 (0.33) has been thought to be responsible for postoperative respiratory failure and subsequent deaths.‘.6 In addition, exacerbations of recognized or occult pulmonary fibrosis may occur with other antineoplastic agents (eg, busulfan, methotrexate, cyclophosphamide) following 0, therapy.‘.’ The anesthesiologist may be required to manage a case for the removal of retroperitoneal lymph nodes or pulmonary metastasis following BLM chemotherapy. Even if the lymph nodes show no metastatic disease, they are large, fibrotic, sclerotic, and often attached to neighboring structures. This makes surgery technically difficult, prolonged, accompanied by considerable blood loss, and may involve the resection of the large bowel, aorta, inferior vena cava, or a kidney.6 Resection of pulmonary metastases has the potential problem of the need for one-lung anesthesia during thoracotomy, and the consequent risk of the use of an increased F,O, to avoid hypoxia. A patient who may have been at risk for reactivation of BLM lung toxicity when he underwent myocardial revascularization during hypothermic cardiopulmonary bypass (CPB) is reported. The use of an Oximetric pulmonary artery catheter (PAC) in combination with peripheral pulse oximetry ensured adequate oxygenation while the patient received restricted 0, therapy during and after surgery.

New treatments for symptomatic severe aortic stenosis

Aortic stenosis (AS) is the most frequent valvular heart disease in western industrialized countries. AS is caused by age related degenerative calcific disease. The mechanism is believed to be similar to that of atherosclerosis. The treatment of symptomatic AS is surgical replacement of the aortic valve. Medical treatment is often utilized in optimizing patients before surgery but has limited utility in treating symptoms. Transcatheter aortic valve replacement (TAVR) has become an established treatment for symptomatic severe AS. Careful patient selection, valve sizing, and meticulous technique result in good outcomes. Palliative management of symptomatic AS was appropriate for patients who were not candidates for aortic valve surgery. This new approach is discussed in this chapter.