Cardiac contractile function during coronary stenosis in dogs: association of adenosine in glycolytic dependence.

We tested the hypothesis that during critical coronary stenosis, endogenous adenosine alters myocardial glucose utilization to support myocardial contractile function (MCF). Anesthetized mongrel dogs were instrumented to measure hemodynamic variables, regional MCF (sonomicrometry), and substrate uptakes. Critical coronary artery stenosis was established with a screw clamp on the left circumflex coronary artery (LCX). Either 8-phenyltheophylline (3 x 10(-7) mol/min; adenosine-receptor blockade), iodoacetate (1 x 10(-5) mol/min; glycolysis blockade), or vehicle was infused into the LCX and the left anterior descending coronary artery (LAD). Critical coronary stenosis caused small decreases in arterial blood pressure and LCX blood flow, but no significant changes in MCF or other hemodynamics. There was a significant decrease in the O2 supply-to-consumption ratio in the stenotic region and an increased glucose uptake. Infusion of either 8-phenyltheophylline or iodoacetate caused a decrease in MCF in the stenotic LCX region concomitant with a decreased glucose uptake and without further changes in blood flow. This was not seen in the nonstenotic (LAD) region. These data support the hypothesis, indicating that glycolysis is vital for maintaining regional MCF during a decrease in the myocardial O2 supply-to-consumption ratio and that adenosine is important in this regard, independent of its vasoactive properties.

In vitro calculation of flow by use of contrast ultrasonography.

Contrast echocardiography has been used for qualitative assessment of cardiac function, and its potential for quantitative assessment of blood flow is being explored. With the development of an ultrasound contrast agent capable of passage through the microcirculation, a mathematical model based on classic dye dilution theory, and a digital ultrasound acquisition system, absolute quantitation of myocardial perfusion may be feasible. This study validates the mathematical model in a simple in vitro tube system. Flow was delivered at variable rates through an in vitro tube system while a longitudinal section was imaged with a modified commercial ultrasound scanner. Albunex contrast agent was injected, and videointensity data were captured and analyzed off line. Time-intensity curves were generated, and flow was calculated by use of a mathematical model derived from classic dye dilution mathematics. For 39 different flow rates, ranging for 9.2 to 110 ml/seconds, a correlation coefficient of r = 0.928 (p < 0.001) with a slope of 0.97 was calculated. We conclude that (1) contrast ultrasonography is capable of quantitative determination of flow in an in vitro system, and (2) a mathematical model based on dye dilution theory can be used to calculate flow with accuracy and precision.

Examination of the hypopharynx predicts ease of laryngoscopic visualization and subsequent intubation: a prospective study of 665 patients.

STUDY OBJECTIVE: To determine (a) whether the ability to visualize a patient's airway preoperatively correlates with the ability to visualize his or her larynx during laryngoscopy and (b) whether the presence of certain anatomic characteristics allows anesthetists to predict difficult laryngoscopic visualization and intubation. DESIGN: Observational. Patients were categorized into two groups: those who had one or more physical characteristics to alert an anesthetist to the possibility of difficult intubation (obesity, overbite, short neck, or decreased neck/jaw mobility) and those with none of these characteristics. SETTING: University-affiliated hospital. PATIENTS: Six hundred sixty-five patients scheduled for general anesthesia and requiring endotracheal intubation. Patients were between the ages of 18 and 88 years, with body weight ranging from 21 kg to 141 kg. INTERVENTIONS: Preoperatively, the anesthetist obtained the best view of the hypopharynx by having the patient extend the tongue and phonate. The airway was then categorized into one of three classes by the ability to see the tonsillar pillars and uvula (Class A, best view--all four tonsillar pillars and uvula seen; Class B, part of the pillars and uvula seen; Class C, worst view--pillars not seen and uvula partially or not seen). After induction, the same anesthetist graded laryngeal visibility into one of four groups depending on his ability to see the patient's epiglottis and vocal cords. MEASUREMENTS AND MAIN RESULTS: Patients with one or more clinical clues were more likely to have poor visualization of the hypopharynx and, in turn, poor laryngoscopic visualization of the glottis. Patients who had a Class A airway tended to have easy laryngoscopic visualization and were relatively easy to intubate. Conversely, patients with no clinical clues and a Class C airway had poor glottic exposure. CONCLUSIONS: Our study confirms work showing that the ability to visualize structures of the hypopharynx is a good predictor of subsequent glottic visualization during laryngoscopy and of ease of intubation.

Continuous infusion of interpleural bupivacaine maintains effective analgesia after cholecystectomy.

Twenty-five patients who had undergone elective cholecystectomy were prospectively randomized to receive via an interpleural catheter either a continuous infusion of 0.25% bupivacaine at 0.125 mL.kg-1.h-1 (n = 13) or repeated bolus injections (n = 12) of 0.5% bupivacaine with epinephrine 1:200,000 at 0.4 mL/kg every sixth hour. Adequacy of pain relief was measured by the amount of patient-controlled analgesia morphine required postoperatively and by patient scores on a visual analog scale obtained every sixth hour. Two venous blood samples for measurements of serum bupivacaine levels were obtained from patients in the continuous group at hours 6 and 24; four blood samples were obtained from patients in the bolus group, both immediately before and 30 min after injections at hours 6 and 24. Among the patients receiving the bolus injections, morphine was required 62 +/- 15 (SEM) times over the 24-h study period with total morphine dosage averaging 30 +/- 15 mg. Corresponding values for patients in the continuous groups were 35 +/- 10 times and 23 +/- 5 mg of morphine. The difference was not, however, statistically significant, but when activity during the 2-h time periods immediately before reinjection were examined, patients in the bolus group required and received significantly more morphine than did those in the continuous group (P less than 0.05). Patients in the continuous group had visual analog scale scores that averaged 2.9 +/- 0.6 over the 24-h study period. Patients within the bolus group had visual analog scale scores before and again 30 min after injection that averaged 5.8 +/- 0.8 and 1.8 +/- 0.5, respectively (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Brain glucose utilization and transport and cortical function in chronic vs. acute hypoglycemia.

We compared regional brain capillary permeability-surface area products for glucose transfer (PSin), cerebral glucose utilization (rCMRGlc) rates, and brain tissue glucose levels (GlCbr) in N2O-sedated, paralyzed, and artificially ventilated rats during normoglycemia (NG), insulin-induced acute hypoglycemia (AH), or chronic hypoglycemia (CH) [hypoglycemic plasma glucose (Glcp) = 2.2-2.3 mumol/ml]. In addition, a comparative assessment of brain function in AH vs. CH was performed employing somatosensory-evoked response (SSER) technology. A double-label (3H and 14C) 2-deoxy-D-glucose method was used for the simultaneous assessment of PSin and rCMRGlc. Compared with normoglycemic controls, AH resulted in significant 40-50% reductions in rCMRGlc in 10 of 11 regions analyzed (cerebellum unchanged). In CH vs. AH, significantly higher values for rCMRGlc, Glcbr/Glcp ratios, and PSin were seen in 8, 8, and 5 regions, respectively. No differences in rCMRGlc were observed when comparing CH vs. NG groups. Furthermore, CH rats were able to sustain normal SSER at levels of hypoglycemia (1.5 mumol/ml) that, when imposed acutely, resulted in attenuated SSER. Thus CH is associated with an enhanced blood-brain glucose transport capacity in many (but not all) brain regions. This in turn increases rCMRGlc and improves the general cerebral function compared with that seen during AH.