Ronald W. Dunbar

Nitroglycerin Infusion during Coronary-artery Surgery

The effects of an intravenous infusion of nitroglycerin were studied in 20 acutely hypertensive patients during coronary-artery surgery. Eight patients had histories of essential hypertension and six had been treated for it. They were anesthetized with morphine, diazepam. N2-O. O2- pancuronium. and enflurane. Control measurements were obtained after sternotomy. Nitroglycerin was then administered until the blood pressure returned to normal, and the measurements then repeated. The mean dose of nitroglycerin was 80.0 ± 4.7 μg/min. or 0.96 SmUg/kg/min. This produced significant decreases (P > .03) in systolic diastolic. and mean arterial blood pressures, central venous pressure, pulmonary- capillary wedge pressure, systemic vascular resistance, and left ventricular stroke work index. Cardiac index, stroke index. and heart rate were unchanged. Two indices of myocardial oxygen demand (rate-pressure product and tension-time index) were significantly decreased by nitroglycerin (P > .005). Fifty per cent of the patients had improvement in ST-segment depression on the electrocardiogram. These findings demonstrate that nitroglycerin can he safely administered intravenously during operation, and suggest that nitroglycerin decreases myocardial oxygen demand and relieves myocardial ischemia.

Plasma Lidocaine Concentrations After Caudal, Lumbar Epidural, Axillary Block, and Intravenous Regional Anesthesia

Chromatographic analysis of lidocaine in plasma was carried out in 15 patients having intravenous regional anesthesia and in 15 patients having axillary block, lumbar epidural, or caudal anesthesia. Plasma lidocaine concentration was lower with intravenous regional anesthesia (1.5 ± 0.2 μg./ml.), than with axillary block (2.5 ± 0.5 μg./ml.), or lumbar epidural anesthesia (3.1 ± 0.7 μg./ml.). Pulse rate, blood pressure and ECG changes were absent in those patients having intravenous regional anesthesia. Intravenous lidocaine, 3 mg./kg. of a 0.5 per cent solution, provides safe, effective anesthesia when injected into an exsanguinated extremity.

Successful use of a reduced dose of protamine after cardiopulmonary bypass.

The dose of protamine necessary to reverse heparin was examined in 60 patients. Half the patients (controls) received a reversal dose of protamine equal to the entire amount of heparin given them, while half received a reversal dose based on a heparin half-life of 2 hours. Postoperative chest drainage for the first 12 hours and for 48 hours was markedly reduced in patients given the reduced dose of protamine. Platelet counts were higher and postoperative clotting studies varied less from control in patients receiving the smaller dose of protamine. The authors suggest reevaluation of the dose of protamine necessary to reverse the anticoagulant effects of heparin in patients for cardiopulmonary bypass, since larger doses of protamine may contribute to the conditions which increase postoperative bleeding.

Propranolol and Cardiac Surgery: A Problem for the Anesthesiologist?

Propranolol therapy has been implicated as a cause of myocardial depression and increased morbidity and mortality in patients undergoing coronary artery surgery. The authors reviewed 169 consecutive patients undergoing cardiac surgery, of whom 143 had been taking propranolol, with regard to preoperative administration of propranolol and intraoperative or postoperative complications. Patients taking propranolol until 24 hours before surgery showed no increased incidence of hypotension or bradycardia before cardiopulmonary bypass. Hypotension after bypass was no more common in patients off propranolol 12 to 48 hours than in patients who either discontinued the drug over 48 hours before operation or had never taken the drug. Myocardial contractility as measured by systolic time intervals was normal 24 to 48 hours after stopping propranolol therapy. Five patients had preoperative myocardial infarctions within 48 hours of discontinuing the drug. The operative mortality rate was 4 percent in patients taking propranolol within 48 hours of surgery and 6 percent in all other patients. Seven risk factors, other than propranolol, were identified in those patients requiring inotropic support. The authors conclude that propranolol can be given safely within 24 to 48 hours of coronary artery surgery provided the patient is a satisfactory candidate for myocardial revascularization.

Intravenous regional anesthesia: experience with 779 cases.

N IDEAL regional anesthetic should be A easy to administer, highly effective, and most important, free of toxic side reactions. For surgery of the upper extremity, supraclavicular brachial plexus block and axillary arm block are often used, while subarachnoid and epidural blocks are used for lower extremity procedures. These methods require frequent application to maintain a high success rate. In addition, the complications from these blocks, such as pneumothorax and spinal headache, are often more incapacitating than the original surgical lesion.

Intralingual succinylcholine administration in children: an alternative to intravenous and intramuscular routes?

METHODS Sixty children, under 10 years of age, scheduled for tonsillectomy or eye-muscle surgery, were studied. All patients were in good health with no evidence of cardiac disease. Pentobarbital (1.5 mg./lb. of body weight) and atropine (0.1 mg.115 lb.) were administered as premedication except as noted below. The patients were divided into 5 groups, according to the route of succinylcholine administration, as follows : group I, 10 patients, no succinylcholine; group 11, 15 patients, % mg./lb. of intravenous succinylcholine; group 111, 10 patients, l mg./lb. of intramuscular succinylcholine; group IV, 15 patients, 1/2 mg./lb. of intralingual succinylcholine; and group V, 10 patients, 1/2 mg./lb. of intralingual succinylcholine (no atropine premedication).

PROPRANOLOL AND SURGICAL ANESTHESIA

The potential danger of anesthetizing a patient on beta-adrenergic blockade therapy has long been recognized. The cases of 73 patients taking propranolol and anesthetized for non- cardiac operations were reviewed with regard to preoperative administration of propranolol and intraoperative and postoperative complications. Of these patients, 72 percent took propranolol to within 24 hours of operation and 85 percent took it to within 48 hours. The mean dose of propranolol was 77 mg/day (range, 10 to 320 mg/day). Anesthetic technics and agents included enflurane, halothane, N2O-narcotic-relaxant, and spinal anesthesia. There were only three episodes of hypotension, all of which responded to a decreased depth of general anesthesia, IV fluid administration, and, in one patient, a small dose of a vasopressor. There were no intraoperative or postoperative deaths. It is concluded that if propranolol is indicated for medical control of the patients symptoms, it need not be discontinued before surgical anesthesia.

Microaggregate blood filters: effect on filtration time, plasma hemoglobin, and fresh blood platelet counts.

Several brands of microaggregate blood filters were evaluated in vitro and in vivo for their effect on plasma free hemoglobin and platelet count, both while new and after prior usage. Time required for passage of diluted packed red cells was also determined. The authors conclude that, although the use of microaggregate filters for multiple transfusions is commonly accepted, their use with fresh blood may decrease platelet count. Filtration characteristics and administration time should be considered in selection of filters.

INTRAVENOUS REGIONAL ANESTHESIA — REPORT OF 497 GASES WITH A TOXICITY STUDY

I would like to add our experiencewith intravenousregional anesthesia at the at the US. Army General Hospital, Landstuhl, Germany and the Valley Forge General Hospital, Phoenixville, Pa., to that of Dr. FLEMING’S. During the period of September 1964 to August 1966, 497 intravenous regional anesthetics were administered. The distribution of cases is shown in Table 1. All adult inpatients received pentobarbital and meperidine as premedication. A technique similar to that described by Bier was used to produce anesthesia.l-a A pneumatic tourniquet was placed high on the arm. When surgery was on the foot or ankle the tourniquet was placed on the mid-calf at least three inches below the head of the fibula. This was done to avoid compression of the peroneal nerve as it crosses the fibula. A 21 gauge scalp vein needle was inserted in a superficial vein as close as possible to the operative site. The extremity was elevated and then exsanguinated by tightly wrapping it in a rubber (Esmarch) bandage. If the needle was in the hand or foot, application of the rubber bandage was started at the wrist or ankle to avoid dislodging the needle. The tourniquet was then inflated to 250-30

The effect of mepivacaine, bupivacaine, and lidocaine on digitalis-induced ventricular arrhythmias.

HERAPEUTIC management of ventricular T arrhythmias is a constant challenge. As the anesthesiologist becomes increasingly involved in patient care outside the operating room and becomes more familiar with moment-to-moment electronic patient-monitoring systems, he becomes increasingly aware of the need for a better understanding of the pharmacology of antiarrhythmic drugs. Although there is no single ideal arrhythmia suppressant, drugs which fall into this category can be assessed in terms of therapeutic efficacy as compared with systemic toxicity.