Accuracy of radial artery blood pressure determination with the Vasotrac.

PURPOSE: To evaluate the accuracy of a new non-invasive method (Vasotrac) to measure blood pressure (BP) with accompanying arterial wave-form and pulse-rate display when compared with BP and waveform measured invasively. METHODS: Healthy volunteers (n=53) served as subjects for the study. Blood pressures and waveforms obtained via a radial artery catheter (IABP) were compared with non-invasive measurements obtained every 12-15 beats by the new system (Vasotrac BP) from the opposite radial artery. In a sub-group of volunteers (n=11), BP was acutely increased and decreased with isoproterenol, phenylephrine and sodium nitroprusside. Data were analyzed by determining correlation and agreement between the two systems of measurement. Waveforms obtained by the two systems were qualitatively examined. RESULTS: Non-invasive BP measured every 12-15 beats by the Vasotrac correlated with IABP (systolic r2 = 0.89; diastolic r2 = 0.88; mean r2 = 0.94). The actual values obtained by the two methods agreed closely with > 90% of readings being within 2SDs when plotted by the Bland Altman method. This was also true during vasoactive drug infusion when BP changed acutely and swiftly. During this dynamic period, Vasotrac BP accurately tracked the changes in IABP with correlations (systolic r2 = 0.82; diastolic r2 = 0.89; mean r2 = 0.95) and close agreement (> 90% of readings were within 2 SDs in the Bland Altman plot). Waveforms displayed by the two systems were qualitatively very similar. Pulse rates measured by the two systems were identical. CONCLUSIONS: The Vasotrac system displayed an arterial waveform which was similar to that obtained directly and measured BP and pulse rate accurately. It should be a convenient device to measure BP continually in a non-invasive fashion.

Children with mucopolysaccharidosis: perioperative care, morbidity, mortality, and new findings.

The perioperative care, morbidity, and mortality in 30 patients with mucopolysaccharidosis (MPS) are presented. They underwent a detailed preoperative assessment and were anesthetized 141 times. An intravenous induction technique was used in most patients. It was easier to see the vocal cords, during laryngoscopy, in children with Hurler syndrome (HS) when they were younger (23 v 41 months, P < or = .01) and smaller (12 v 15 kg, P < or = .05). Preoperative obstructive breathing was associated with a significantly higher incidence of postextubation obstruction (P < or = .05). A total of 28 children underwent bone marrow transplantation (BMT); this reversed upper airway obstruction and also reversed intracranial hypertension. In children with HS, the incidence of odontoid dysplasia was 94%; 38% demonstrated anterior C1-C2 subluxation. Head and neck manipulation was limited in children with cervical spine defects. None of the 30 patients experienced spinal cord morbidity. One child suffered an intraoperative stroke; another, pulmonary edema. Severe and extensive coronary obstruction was responsible for 2 intraoperative deaths. Coronary angiography underestimated coronary artery disease.

Surfactant-mediated hydrophobic interaction chromatography of proteins: gradient elution.

Addition of 3-[(3-cholamidopropyl)dimethylammonio]-l-propanesulphonate (CHAPS) to mobile phases in gradient elution hydrophobic interaction chromatography (HIC) on SynChropak Propyl causes changes in observed elution times for nine globular proteins. The nine proteins showed different percentage reductions in capacity factor, k', demonstrating the ability of CHAPS to change the selectivity of the separations. Three basic types of gradient experiments have been explored for surfactant-mediated gradient elution HIC. Type I gradients are conducted with constant salt and variable surfactant concentration. Type II gradients with variable salt and constant surfactant concentration, and Type III gradients with variable salt and surfactant concentrations. By the criterion of a linear relationship between gradient time and retention time the linear solvent strength condition applies to Type II and Type III gradients. Type III gradients, with the fastest re-equilibration time, are preferable for repetitive analyses. Type I gradients are relatively ineffective in making use of the solvent strength of CHAPS, and Types I and II gradients require long equilibration times due to large changes in surface concentration of CHAPS which occur during elution. The presence of CHAPS had a negligible effect on peak shapes of the proteins examined, except for bovine serum albumin which yielded a narrower, less distorted peak in the presence of CHAPS.

Use of the surfactant 3-(3-cholamidopropyl)-dimethyl-ammoniopropane sulfonate in hydrophobic interaction chromatography of proteins.

Isocratic hydrophobic interaction chromatography of five proteins has been carried out using mobile phases containing the surfactant 3-(3-cholamidopropyl)-dimethylammoniopropane sulfonate (CHAPS). Linear relationships were found between log k' and ammonium sulfate concentrations for all the proteins with CHAPS in the submicellar concentration range. The slope of such a plot decreases monotonically as CHAPS concentration is increased. To a first approximation, the effect of CHAPS on protein retention can be explained in terms of a competitive binding model. However, CHAPS does show differential effects on the elution of proteins, substantially altering selectivity. The use of a normalized capacity factor, k'/k'o, proves useful for comparing retention times of different proteins as a function of CHAPS concentration. The magnitudes of k'/k'o were found to be inversely correlated with the slopes of plots of log k' vs. ammonium sulfate concentration in the absence of CHAPS. Adsorption isotherms for CHAPS were determined over the working range of ammonium sulfate. The binding of CHAPS to the SynChropak Propyl stationary phase and its effects on retention were found to be readily reversible. For each protein, plots of k'/k'o vs. surface concentration of CHAPS were superposable for data obtained at different salt concentrations. These findings support a competitive binding model. A simple geometric argument for stationary phase occupancy provides a qualitative explanation for the observed surfactant selectivity.

A new approach to massive blood transfusion during pediatric liver resection.

Morbidity and death during liver resection in children are due to hemorrhage and the consequences of massive transfusion. To overcome these problems, a new rapid method of blood transfusion was used in four children (8 to 35 months, 8.6 to 13 kg) undergoing extensive hepatic resection for tumor (tumor weight, 440 to 1625 gm). The rapid infusion device consisted of a roller pump and a bubble oxygenator-warmer circuit primed with washed packed red cells resuspended in fresh-frozen plasma and calcium-free balanced salt solution (Plasmalyte). The infusate was warmed, oxygenated, and buffered before it was administered. An average of 5130 ml per patient of this reconstituted blood was infused at an average rate of 122 +/- 45 ml/min, with peak infusion rates sometimes as great as 1 L/min. Cardiac output, pulmonary artery wedge pressure, body temperature, urine output, blood gases, blood chemistries, and coagulation factors remained unchanged during and after these massive transfusions. Blood transfusion at rapid rates required during pediatric liver resection can be accomplished safely if the storage lesion of the bank blood is previously corrected.

Stochastic dominance: an approach to decision making under risk.

This paper introduces stochastic dominance as a technique to reduce the set of possible actions that a decision maker must consider in a decision problem under risk. The procedure usually does not choose an optimal action, but instead eliminates certain actions as unacceptable. Very little need be known about the decision maker's utility function. Two possible applications are presented: upgrading buildings to better withstand an earthquake; and choosing a site for a LNG facility.

Pharmacokinetics of fentanyl in neonates.

The pharmacokinetics of fentanyl were studied in fourteen neonates undergoing major surgical procedures. Five patients were less than 1 day of age, seven were 1-4 days old, and two were 7-14 days old. Fentanyl was given intravenously, 10 micrograms/kg (n = 1), 25 micrograms/kg (n = 4), or 50 micrograms/kg (n = 9), and plasma concentrations measured at intervals of up to 18 hr. Average weight was 2.9 kg. The injection of 25 or 50 micrograms/kg of fentanyl over 1-3 min was hemodynamically well-tolerated by all patients. Four newborns without respiratory impairment secondary to surgery or disease needed ventilatory support for an average of 24 hr (range 11-40 hr). Plasma concentrations of fentanyl were most appropriately described by a two-compartment model. The mean +/- SEM values of selected model parameters were volume of the central compartment, 1.45 +/- 0.34 L/kg; volume of distribution at steady state, 5.1 +/- 1 L/kg; clearance, 17.94 +/- 4.38 ml X kg-1 X min-1; and terminal elimination half-life (t 1/2 beta), 317 +/- 70 min. In seven patients transient rebound in plasma fentanyl concentrations of 0.5 ng/ml or greater occurred. In three patients with markedly increased intraabdominal pressure, the t 1/2 beta was 1.5-3 times the population mean. Thus fentanyl disposition in neonates is highly variable, but the t 1/2 beta is predictably prolonged in the presence of increased abdominal pressure.

Delayed hydrothorax following percutaneous central venous cannulation.

Isolated cases of delayed complications associated with prolonged use of percutaneous central venous lines have been reported. We report four patients who developed hydrothorax more than 24 h after central venous cannulation due to perforation of an intrathoracic vein wall by the catheter tip. The patients were all adults of average body habitus. Left-sided catheters were placed in the operating room after anesthetic induction by experienced personnel using the Seldinger technique and secured in position with a dressing and tape. Chest x-rays taken in the recovery room showed all catheter tips terminated in the central vein and no evidence of hydrothorax. Hydrothorax was manifested in the post-operative period and occurred 1-7 days postcannulation. We are left with the conclusion that the delayed hydrothorax resulted from gradual penetration of the vein wall by the catheter tip. We feel a combination of factors probably contributed to the vein wall erosion. First, the insecure fixation of the catheter combined with head, neck, and cardiopulmonary motion has been shown to result in the back-and-forth movement of the catheter tip. Second, the stiff catheters in the left jugular system take a curved course to the superior vena cava bringing the catheter tip into close proximity to the wall of the superior vena cava. We therefore conclude that late developing hydrothorax can be minimized by using a soft, pliable catheter, sutured firmly in place. Right-sided line placement is preferable to left-sided placement because of the anatomic relationships.

Dissimilarities between droperidol and phentolamine on vascular tone and dopamine and norepinephrine vasoconstriction.

Droperidol has been found to have an alpha-adrenoceptor blocking potency comparable to phentolamine in in vitro studies where norepinephrine was used as the alpha agonist. Because dopamine also stimulates alpha receptors, its vasoconstrictor effects should be similarly inhibited by droperidol and phentolamine. Because the aforementioned comparisons have not been examined in vivo, we continuously infused either droperidol or phentolamine into a denervated canine hindlimb, perfused at a constant rate of blood flow, and measured changes in the basal perfusion pressure and its response to intra-arterial injections of dopamine and norepinephrine. It was found that 1) droperidol was much less potent than phentolamine in blocking the vasoconstrictor response to dopamine and norepinephrine. 2) Phentolamine's inhibition of dopamine was similar to its effect on norepinephrine whereas droperidol had the opposite effect, producing a greater inhibitory effect on norepinephrine than on dopamine. 3) The initial decrease in vascular resistance at the onset of steady state plasma levels of droperidol was quite transient while with phentolamine a corresponding decrease in vascular tone was more prolonged.

Risk of bacteremia after endotracheal intubation for general anesthesia.

Blood cultures were obtained before and after endotracheal intubation to assess the risk of bacteremia associated with this procedure and to evaluate the need for prophylactic antibiotics to prevent bacterial endocarditis in patients with structural heart disease requiring general anesthesia. Blood cultures were obtained immediately before intubation and two and ten minutes after intubation in 50 individuals without evidence of structural heart disease who required general anesthesia for elective surgery. Of 32 who had orotracheal intubation, only one demonstrated postintubation bacteremia; of 18 individuals who had nasotracheal intubation, none had evidence of bacteremia. These data suggest that in healthy individuals undergoing endotracheal intubation under direct vision the risk of bacteremia is quite small (about 2%).

Percutaneous cervical central venous line placement: a comparison of the internal and external jugular vein routes.

To compare the rate of success and incidence of complications associated with two currently popular routes of percutaneous central venous cannulation, we studied 167 patient in whom either internal or external jugular vein catheterization was attempted. Internal jugular vein (IJV) catheterization (125 patients) was successful in 91%; an intrathoracic location was achieved in 100%; complications occurred in 12.8%. Complications included one case of catheter malposition, one case of tension pneumothorax, and 12 instances of inadvertent carotid artery puncture, one resulting in a paratracheal hematoma and phrenic nerve compression. The success rate of IJV cannulation was higher and carotid artery puncture less frequent when an 18-gauge thin-walled needle and a straight guide-wire were used than when IJV cannulation was performed by bind puncture with a larger over-the-needle catheter. Delayed vein perforation occurred twice. External jugular vein cannulation (42 patients), using a "J" wire technique, yielded a 76% success rate: 93.7% of catheter tips reached an intrathoracic location. No complications occurred. We conclude that IJV cannulation is a more reliable means of percutaneous central venous line placement but is associated with a significant incidence of complications which can be reduced if a technique employing a scout needle and guide-wire is used.

The Bezold reflex: a special case of the left ventricular mechanoreceptor reflex.

Our previous finding that increasing myocardial contractility caused reflex systemic hypotension, the left ventricular (LV) mechanoreceptor reflex, suggested that the classical Bezold reflex (systemic hypotension and bradycardia after intracoronary administration of veratrum alkaloids) may be initiated by these same LV mechanoreceptors. In our working LV preparation with the coronary and systemic circulations isolated and perfused separately, intracoronary injection of veratrum alkaloids, like that of catecholamines or ouabain, had a positive inotropic effect which produced the hypotensive response typical of the LV mechanoreceptor reflex. To test directly if veratridine's positive inotropic effect initiates the Bezold reflex, verapamil, which blocks the slow Ca(2+) channels of myocardial cells but leaves intracardiac nerves unaffected, was injected by the intracoronary route to prevent the increased contractility from intracoronary injection of veratridine which also abolished the reflex hypotension, demonstrating conclusively that increasing myocardial contractility and thereby activating LV mechanoreceptors but not chemoreceptors initiates the Bezold reflex. Contrariwise, decreasing contractility or cardiac asystole by administration of tetrodotoxin, verapamil, or EDTA resulted in an increase in the systemic resistance, indicating that changes in the magnitude of the stimulus initiating the LV mechanoreceptor reflex (i.e., changes in myocardial contractility) lead to directionally opposite changes in peripheral resistance, as in the sino-aortic mechanoreflexes. Thus, it is concluded that the Bezold reflex is a special case of the LV mechanoreceptor reflex. The latter, by means of feedback mechanisms, functions normally by continuously matching the peripheral resistance to the LV contractile state so as to maintain the arterial pressure constant, thereby playing an important role in blood pressure regulation.