Paul J. Dauchot

Radial artery cannulation and complications in 1,000 patients: Precautions

A review of 1,000 radial artery cannulations performed over a 2-year period showed that, with careful selection of patients, by means of the Allen test and Doppler studies, and with the apparatus used, only two serious complications were encountered; embolectomy was necessary in one and arterial reconstruction in another. Twenty-four percent of patients had evidence of diminution of flow, but in none did it persist for more than 2 weeks. Critical factors in reducing complications were a short period of cannulation, use of a Teflon catheter, and a continuous arterial line flush system.

The self-tuning controller: comparison with human performance in the control of arterial pressure

A self-tuning controller was implemented for the automated infusion of sodium nitroprusside to lower mean arterial pressure in anesthetized dogs. The system incorporated a recursive least-squares parameter identifier and a modified minimumvariance controller. The onset delay was estimated on-line, the performance criterion included the cost of control, and requested step-changes were automatically translated into five successive smaller steps to reduce overshoot. The performance of the system in lowering mean arterial pressure was quantitatively compared with that of a well-trained anesthesiologist. In 10 runs in four animals, the automated system performed as well as the physician who devoted 100% of his attention to the task. Since the stability of the self-tuning controller cannot be guaranteed, such a system should be operated only in the presence of appropriate supervisory algorithms.

Management of Aortocaval Fistula Due to Abdominal Aortic Aneurysm

Anasarca and intractable congestive heart failure were the presenting signs of an abdominal aortic aneurysm with aortocaval fistula. Management with careful monitoring of cardiovascular function using a Swan-Ganz catheter before, during, and after surgery resulted in an uneventful recovery.

Detection and prevention of cardiac dysfunction during aortic surgery

Abstract Anesthesia and aortic occlusion and release all can adversely affect cardiac function during aortic reconstruction. To minimize these effects we developed on-line computerized monitoring techniques to measure systolic time intervals (STI) and compared these data with results of cardiac output, and in nine patients with pulmonary artery pressures obtained by Swan-Ganz catheters. In 35 patients, left ventricular preejection time (PEP), left ventricular ejection time (LVET), and PEP/LVET were displayed continuously in the operating room. Paired cardiac outputs, determined by dye dilution ( 26 35 ) or thermodilution ( 9 35 ) provided cardiac index and systemic vascular resistance. Pulmonary artery diastolic pressure (PADP) was taken for the assessment of preload. Heart rate and mean arterial pressure were recorded using radial artery cannulas. Characteristic changes were noted and compared during anesthesia and clamping and release of aortic occlusion. Changes in LVET were most notable with highly significant increases during aortic crossclamping. This overall effect occurred frequently in patients with EKG evidence of prior myocardial infarction ( 24 25 ). In 11 patients without previous myocardial infarction, LVET increased only once during aortic crossclamping. STI were clearly most sensitive for titrating both anesthetic and vasoactive drugs to minimize cardiac depression. In contrast, pulmonary artery diastolic pressures appeared more specific for alterations in blood and fluid balance. While changes in PADP were often inconclusive, changes in STI made possible rapid detection of adverse effects of anesthesia, crossclamping, and unclamping upon cardiac function. The immediate detection and treatment of changes in left ventricular function add an important safety factor in minimizing cardiac mortality of aortic surgery.

Continuous real-time computation and display of systolic time intervals from surgical patients.

Abstract The noninvasive measurement of systolic time intervals (STI) during surgery is expected to provide a useful index of the status of the patients heart. A PDP-11 based system has been developed to continuously measure and report these intervals in real time. The software has been designed to allow easy implementation of a variety of monitoring tasks, in addition to STI. To accomplish this, a general purpose control program was developed which maintains a multipatient environment and performs all operations which are task independent. Applications modules, specific to the parameters being measured, are called from the control program. For STI, these modules operate on samples of the ECG, carotid pulse, and heart sounds to obtain the onsets of the QRS, systolic upstroke, dicrotic notch, and second heart sound. Every 15 sec, other modules derive mean and standard deviation of the preejection period (PEP), left-ventricular ejection time (LVET), and heart rate. Trend graphs of these parameters are displayed in the operating room. The accuracy of computer-determined STI was evaluated by comparing manual and machine measurements of 250 randomly selected heartbeats. The mean difference between the measurements was less than 1.5 ± 7 (SD) msec.

Effects of nifedipine on the hemodynamic response to clamping and declamping of the abdominal aorta in dogs.

Clamping and declamping of the infrarenal abdominal aorta may adversely affect cardiovascular function, particularly in the presence of heart disease. This effect may be further altered by drugs used in the treatment of symptomatic coronary artery disease. The effect of nifedipine on the hemodynamic response to aortic clamping and declamping was determined in 12 dogs anesthetized with 50% nitrous oxide and 0.6% end-tidal isoflurane and monitored with aortic, left ventricular (LV), and thermodilution pulmonary artery catheters. Six dogs received a nifedipine bolus of 100 micrograms/kg followed by an infusion of 4 micrograms/kg/min. Six dogs did not receive any nifedipine and served as controls. Before clamping, nifedipine produced immediate decreases in arterial pressure, systemic vascular resistance (SVR), and LV dP/dt, and a modest increase in cardiac output (CO). During aortic clamping, nifedipine-treated dogs demonstrated marked increases in heart rate (HR), dP/dt, and CO while maintaining a low SVR. There were no significant changes upon declamping. The nifedipine-treated animals maintained a high CO and low SVR. Thus, nifedipine greatly altered the hemodynamic responses to aortic clamping and declamping. Awareness of these alterations is important when caring for patients being treated with nifedipine who are undergoing aortic surgery.

Effectiveness of Sodium Nitroprusside as a Function of Total Peripheral Resistance in the Anesthetized Dog

To determine the influence of background vasomotor tone on the effectiveness of sodium nitroprusside in decreasing total peripheral resistance, experiments were performed on 12 open-chest dogs under halothane anesthesia. In the first experiment, the vasomotor condition of six dogs was changed by altering the background infusion rate of phenylephrine (0, 40, and 0 μg/min). Increasing background phenylephrine infusion from 0 to 40 μg/min significantly enhanced the effectiveness of nitroprusside in decreasing total peripheral resistance. In contrast, the effectiveness of nitroprusside in decreasing arterial pressure was not altered significantly. In a second experiment on six other dogs, phenylephrine was infused continuously at 40 μg/min, and the vasomotor condition was changed by the infusion of phentolamine (0, 60–100, 0 μg/min). Phentolamine significantly diminished the effectiveness of nitroprusside in decreasing peripheral resistance. In contrast, the effectiveness of nitroprusside in decreasing arterial pressure was not altered significantly. Stepwise linear regression analysis indicated that the background peripheral resistance was the hemodynamic variable that could account partially for the changes in nitroprusside effectiveness. Increasing background total peripheral resistance significantly enhanced the effectiveness of nitroprusside in decreasing total peripheral resistance.

Cardiac Function During Induction and Early Anesthesia with Methoxyflurane. An Evaluation Using Systolic Time Intervals and Pressure Time Indices

In addition to the standard monitoring of heart rate and blood pressure, the Systolic Time Intervals were used to evaluate cardiac performance, and the Pressure Time Indices (tension time index = TTI; diastolic pressure time index = DPTI) were used to estimate myocardial oxygen balance. Twelve patients with known heart disease were studied during induction with thiopental, intubation, and early anesthesia with methoxyflurane.

Epinephrine-aminophylline-induced arrhythmias after midazolam or thiopentone in halothane-anaesthetized dogs

The purpose of this study was to evaluate epinephrine-aminophylline-induced arrhythmias during halothane anaesthesia after induction with thiopentone or midazolam. Ten mongrel dogs were studied during 1 MAC halothane and 50% N2O:O2 anaesthesia while maintaining constant acid-base status. The minimal arrhythmogenic infusion rate of epinephrine (MAIRE) and the corresponding plasma concentration of epinephrine (MAPC) required to produce ventricular arrhythmias before and after aminophylline were higher following induction of anaesthesia with midazolam than with thiopentone (P < 0.05); the MAIREs decreased stepwise with aminophylline (P < 0.05). The correlation coefficient between individual MAIREs and MAPCs was 0.93 (P < 0.001). Epinephrine alone and in combination with aminophylline was less arrhythmogenic after induction with midazolam than with thiopentone.RésuméCette étude fut entreprise pour comparer l’ effet de l’ induction de l’ anesthésie au midazolam à l’effet de l’induction au thiopentone sur l’arythmogénicité de l’ épinéphrine tant en l’absence qu’en la présence d’aminophylline. Cinq chiens reçurent 10 mg · kg−1 de midazolam intraveineux. Cinq autres reçurent 25 à 30 mg · kg−1 de thiopentone. Après intubation trachéale, tous furent gardés sous anesthésie à l’ aide de 1 MAC d’ halothane dans un mélange de 50% de N2O et d’O2. Les taux minimaux d’infusion d’ épinéphrine (MAIRE) requis pour produire des arythmies ventriculaires et les concentrations plasmatiques d’ épinéphrine correspondantes (MAPC) diminuèrent graduellement après 10 et 20 mg · kg−1 d’ aminophylline mais furent toujours plus élevés après l’induction au midazolam qu’ après l’induction au thiopentone. Donc, sous nos conditions expérimentales et comparée au thiopentone, l’induction au midazolam atténue l’ arythmogénicité de l’ épinéphrine tant en l’absence qu’ en la présence d’aminophylline.

Subjective assessment and cardiovascular response to ischemic pain in young, healthy women users and non-users of oral contraceptives

Due to the fact that oral contraceptives (OCs) can alter the pain threshold and since evidence of possible concomitant changes in the cardiovascular response to pain is still missing, an investigation of the response of heart rate (HR), blood pressure (BP), and systolic time interval (STI) to ischemic pain in OC users and nonusers was conducted. The objective was to explore also the existence of correlations, if any, between subjective and hemodynamic responses. 26 women students volunteered for the study. 12 of the women used a combination of estrogen-progestogen OCs (users) and 14 did not (nonusers). The women were healthy and of similar height, weight, age, and strength. 4 users and 3 nonusers smoked cigarettes. Ischemic pain was induced by blanching the dominant arm with an Esmarck bandage, inflating an upper arm cuff at 250 torr, and having the subject exercise the ischemic hand by pulling the ergometer springload of 5.4 kg 15 times in 75 seconds according to a rigid time schedule. Following the exercise, pain levels were estimated by the subjects on a numbered visual scale in color. The 2 groups differed statistically in cardiovascular variables. At rest the users had higher HR and shorter preejection period (PEP) than the nonusers. The Wilcoxon rank-sum test showed no difference between users and nonusers as to the intensity of perceived pain. In the user group a significant positive correlation between pain and preejection period time index (PEPI) and the PEP/LVET (left ventrical ejection time) ratio was observed. These correlations were not significant in the nonusers. Both hypertension and heart disease occur more often in OC users than in nonusers. In the sample the 2 groups were not distinguished at rest by differences in BP, but they did differ in the cardiac variables of HR and PEP. Users had more rapid HR and shorter PEP than the nonusers, implying a comparatively more active cardiac state.