Jacek Wojtczak

Combined electrophysiological technique for assessment of the cellular basis of early ventricular arrhythmias.

A new technique has been used in dogs to make combined measurements in vivo of conduction delay, action potentials, and epicardial ST-segment during myocardial ischaemia. These measurements should provide new information about ionic and metabolic cellular changes relating to the onset of ventricular arrhythmias.

Contractures and increase in internal longitudianl resistance of cow ventricular muscle induced by hypoxia.

This study was performed to determine whether hypoxia in glucose-free solutions can increase the electrical resistance of intercellular junctions in ventricular muscle. Internal longitudinal resistance (Rj), mechanical tension, and transmembrane action potentials were measured simultaneously in cow ventricular trabeculae. The mean control value of Rj was 265 ± 38 Ωcm (mean ± SE) at 34°C. After 1 hour of hypoxia in glucose-free Tyrodes solution, it had increased by 300 ± 41% (n « 11, P < 0.001). The rise in Rj was closely related to the increase in resting tension (contracture). These effects were more pronounced during a second exposure to hypoxia and were potentiated by application of epinephrine, by increasing extracellular calcium concentration, and by increasing frequency of stimulation. Addition of glucose (50 mM) provided some protection against hypoxia. It is inferred that the increase in Ri is entirely due to the increase in the resistance of intercellular junctions (electrical uncoupling). Intracellular calcium may be responsible for both the contracture and the uncoupling. Circ Res 44: 88-95, 1979

Submandibular sonography: assessment of hyomental distances and ratio, tongue size, and floor of the mouth musculature using portable sonography.

The aim of this study was to evaluate the feasibility of sonography as a tool to measure the hyomental distance ratio and tongue size in obese patients with a large neck circumference. The hyomental distance ratio is a predictor of difficult laryngoscopy that may result in difficult intubation.

Lack of Lung Hemorrhage in Humans After Intraoperative Transesophageal Echocardiography with Ultrasound Exposure Conditions Similar to Those Causing Lung Hemorrhage in Laboratory Animals

This study investigated the phenomenon of ultrasonically induced lung hemorrhage in humans. Multiple experimental laboratories have shown that diagnostic ultrasound exposure can cause hemorrhage in the lungs of laboratory animals. The left lung of 50 patients (6 women, 44 men, mean age 61 years) was observed directly by the surgeon after routine intraoperative transesophageal echocardiography was performed. From manufacturer specifications the maximum derated intensity in the sound field of the system used was 186 W/cm2, the maximum derated rarefactional acoustic pressure was 2.4 MPa, and the maximum mechanical index was 1.3. The lowest frequency used was 3.5 MHz. This exposure exceeds the threshold found for surface lung hemorrhage seen on gross observation of laboratory animals. No hemorrhage was noted on any lung surface by the surgeon on gross observation. We conclude that clinical transesophageal echocardiography, even at field levels a little greater than the reported thresholds for lung hemorrhage in laboratory animals, did not cause surface lung hemorrhage apparent on gross observation. These negative results support the conclusion that the human lung is not markedly more sensitive to ultrasound exposure than that of other mammals.

Pocket mobile smartphone system for the point-of-care submandibular ultrasonography

BACKGROUND Focused ultrasonography of the airway may be useful in the prediction of difficult intubation. The wider use of sonography in quantitative airway assessment may depend on the availability of highly portable, inexpensive, and accurate ultrasound systems. Pocket-sized ultrasound devices are emerging as a useful tool for point-of-care ultrasonography. The aim of this study was to evaluate the suprahyoid airway of healthy volunteers using a smartphone-based ultrasound imaging system in comparison with a platform-based machine. METHODS Mobisante MobiUS SP1 system with 2 mechanical sector (3.5 and 7.5 MHz) probes was used to acquire images of the tongue and measure the diameter of the hyomental muscle in the mouth floor. In the same group of subjects, imaging and measurements were repeated using BK Medical Flex Focus 400 ultrasound system with linear (18 MHz ) and curved 5 (MHz) transducers. The MobiUS system was also used to image plastic cylinders and procedure needles embedded in tofu bars. Outside diameters of cylinders were measured using digital calipers and sonography. RESULTS The mean diameter of the hyomental muscle in 10 healthy volunteers was 7.22 ± 1.6 mm using BK 18 MHz probe, 7.11 ± 1.7 mm using MobiUS 7.5 MHz probe, and 7.84 ± 2 mm using MobiUS 3.5 MHz probe. These means were not statistically different (BK vs Mo 7.5, P = .74, and BK vs Mo 3.5, P = .13). The mean outside diameter of plastic cylinders measured with digital calipers was 10.1 ± 0.2 mm (n = 5) vs 9.8 ± 0.3 mm and 10.2 ± 0.2 mm using 3.5 and 7.5 MHz probes, respectively. These means were not statistically different (calipers vs Mo 3.5, P = .16 and calipers vs Mo 7.5, P = .39). CONCLUSION Mobisante MobiUS system was able to acquire clinically useful images of the suprahyoid airway and muscular architecture in the mouth floor and allowed accurate measurements of linear distances.

Influence of cyclic nucleotides on the internal longitudinal resistance and contractures in the normal and hypoxic mammalian cardiac muscle

Influence of the derivatives of cyclic adenosine monophosphate (cyclic AMP) and cyclic guanosine monophosphate (cyclic GMP) on the internal longitudinal resistivity (Ri) and mechanical tension was studied in normal and hypoxic cat ventricular muscle. Dibutyryl cyclic AMP in concentration of 10−3 m and 8-bromo cyclic GMP in concentration of 3 × 10−4 m had no effect on Ri in the normal muscle. Dibutyryl cyclic AMP in the same concentration potentiated the hypoxia-induced increase in Ri and contracture. Bromo cyclic GMP exerted no effect. Isoprenaline (10−7 m), known to increase intracellular cyclic AMP had qualitatively similar action in the hypoxic muscle as dibytyryl cyclic AMP. Drugs increasing intracellular cyclic GMP such as acetylcholine (10−6 m) and sodium nitroprusside (5 × 10−4 m) exerted no effect. The action of cyclic AMP seems to be related to an increase in calcium concentration inside the hypoxic cells which accelerates the rise of Ri (intercellular uncoupling).

The hemodynamic effects of halothane and isoflurane in chick embryo.

The cardiovascular effects of volatile anesthetics in prenatal hearts are not well investigated. The purpose of this study was to determine whether the embryonic cardiovascular system is sensitive to an exposure to clinically relevant, equipotent concentrations of halothane and isoflurane. Stage 24 (4-day-old) chick embryos were exposed to 0.09 and 0.16 mM of halothane and 0.17 and 0.29 mM of isoflurane. Dorsal aortic blood velocity was measured with a pulsed-Doppler velocity meter. Halothane, but not isoflurane, caused a significant decrease in cardiac stroke volume and maximum acceleration of blood (dV/dtmax), an index of cardiac performance. This effect was reversible, and during washout, stroke volume and dV/dtmax increased above control levels. Embryonic heart rate was not affected by either drug. Chick and human embryos are similar during early stages of development; therefore, chick embryo may be a useful model to study the cardiovascular effects of anesthetics. Implications In equipotent, clinically relevant concentrations, halothane, but not isoflurane, markedly decreased aortic blood flow and cardiac performance measured with ultrasound techniques in chick embryos. Chick and human embryos are similar during early stages of development; therefore, chick embryo may be a useful model to study the cardiovascular effects of anesthetics.

Ultrasound evaluation of the impact of cricoid pressure versus novel 'paralaryngeal pressure' on anteroposterior oesophageal diameter.

To assess the degree to which cricoid pressure (Sellick manoeuvre) actually compresses the oesophagus, we measured the effect of cricoid pressure and paralaryngeal pressure on the outer anteroposterior diameter of the upper oesophagus with ultrasound in 39 healthy volunteers. The mean (SD) outer anteroposterior oesophageal diameter was 0.77 (0.11) cm with no pressure, 0.79 (0.13) cm with the application of cricoid pressure of 30 N and 0.68 (0.12) cm with the application of paralaryngeal pressure of 30 N (p < 0.0001). If cricoid pressure does not reduce the anteroposterior diameter of the oesophagus, it is difficult or impossible to explain the efficacy of the Sellick manoeuvre. However, paralaryngeal pressure decreases this diameter and has the potential to occlude the upper oesophagus.

COMBINED ELECTROPHYSIOLOGICAL TECHNIQUE FOR ASSESSMENT OF THE CELLULAR BASIS OF EARLY VENTRICULAR ARRHYTHMIAS: Experiments in Dogs

A new technique has been used in dogs to make combined measurements in vivo of conduction delay, action potentials, and epicardial ST-segment during myocardial ischaemia. These measurements should provide new information about ionic and metabolic cellular changes relating to the onset of ventricular arrhythmias.

Electrophysiological effects of the neuroleptanalgesic drugs on the canine cardiac tissue

SummaryParameters of action and resting potentials of dog Purkinje and ventricular muscle fibers were studied after the administration of droperidol and fentanyl given separately and in combination (in a weight proportion 50:1 as in neuroleptanalgesia). Droperidol in all concentrations studied (10−6 M, 5×10−6 M, 10−5 M) moderately shortened action potential duration in electrically driven Purkinje fibers. Effective refractory period was also shortened but to a lesser degree than action potential duration. The drug was also able to diminish the automaticity in Purkinje fibers. It exerted nearly no effect on resting membrane potential, action potential amplitude and on maximum rate of depolarization. The latter was only slightly decreased by the highest concentration of the drug. Also conduction velocity in Purkinje fibers was not changed by the drug. Ventricular action potentials were not significantly influenced by droperidol. Fentanyl administered in concentrations 2.2×10−7 M and 1.1×10−6 M was devoid of any action on cardiac transmembrane potentials. The effects exerted by both drugs administered simultaneously were similar to the effects exerted by droperidol administered as a sole agent. The electrophysiological effects of droperidol on the isolated cardiac tissue are very similar to the action of lidocaine and diphenylhydantoin.