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Biomedical subjects

R Pizov

Publications and source records attributed to R Pizov.

51 records · Page 3Linked to original sources
PubMed1992

Halothane inhibition of ion transport of the tracheal epithelium. A possible mechanism for anesthetic-induced impairment of mucociliary clearance.

Significant depression of mucociliary function occurs during general anesthesia. One possible mechanism to account for this effect is a change in ion and water transport across airway epithelium. To determine if anesthetics alter epithelial cell function, we used electrophysiologic techniques to measure the effects of halothane on ion transport of in vitro canine tracheal epithelial. Epithelial tissues were mounted in an Ussing chamber and the short-circuit current (Isc) (a measure of active ion transport) and transepithelial resistance were determined in the absence and presence of halothane. Halothane induced a rapid and reversible decrease in Isc that was dose-dependent. Four percent halothane reversibly decreased Isc from 90 +/- 11 to 39 +/- 6 microA/cm2 (n = 12; P = 0.001) and increased transepithelial resistance. Isoproterenol is a well-known activator of chloride secretion that acts via beta-adrenergic receptors and cyclic adenosine monophosphate (cAMP). Pretreatment with isoproterenol or dibutyryl cAMP (a cell permeable analogue of cAMP) increased the percent inhibition of Isc by 4% halothane. These effects are consistent with preferential inhibition of chloride secretion by halothane but rule out a primary action of halothane on the beta-adrenergic system. In the presence of indomethacin, which eliminates the contribution of chloride secretion to Isc, 4% halothane induced a much smaller but still significant inhibition. This suggests that sodium absorption is also affected. We conclude that halothane significantly decreases ion and water transport in canine epithelia and that impaired fluid secretion may contribute to decreased mucous clearance in the perioperative period.

Animals↗
PubMed1989

The effect of tidal volume and intravascular volume state on systolic pressure variation in ventilated dogs.

Both tidal volume and effective blood volume may affect the variation in the arterial pressure waveform during mechanical ventilation. The systolic pressure variation (SPV), which is the difference between the maximal and minimal systolic pressure values following one positive pressure breath was analyzed in 10 anesthetized and ventilated dogs, during ventilation with tidal volumes of 15 and 25 ml/kg. The dogs were studied during normovolemia, hypovolemia (after bleeding of 30% of estimated blood volume) and hypervolemia (after retransfusion of shed blood with additional 50 ml/kg of plasma expander). The SPV reflected hemodynamic changes and was maximal during hypovolemia and minimal during hypervolemia. Unlike all other hemodynamic parameters it was also affected by the tidal volume and significantly increased at higher tidal volumes during each volume state. We conclude that the SPV and its components are useful parameters in evaluating the intravascular volume state. They also reflect the magnitude of the tidal volume employed.

Animals↗
PubMed1989

QRS-activated ventilation during general anesthesia for extracorporeal shock wave lithotripsy.

High frequency ventilation has been claimed to improve the efficiency of extracorporeal shock wave lithotripsy (ESWL) by minimizing the movement of urinary stones during the procedure. A ventilatory mode, QRS-activated ventilation, was developed in which the stones remain motionless during the delivery of shock waves. As the shock wave is triggered to occur approximately 20 milliseconds after the R wave of the QRS complex, the mechanical breath was synchronized to occur approximately 150 ms later. QRS-activated ventilation is used in 16 patients undergoing ESWL under general anesthesia. Tidal volume was set at 3 ml/kg (234 +/- 36 ml; mean +/- SD) at a rate that equaled the heart rate (71 +/- 9 beats/min). The time between the R wave and the initiation of mechanical breath (T1) was 124 +/- 25 ms, time of mechanical breath itself (T2) was 431 +/- 67 ms, and time between end of T2 and next R wave (T3) was 264 +/- 84 ms. End-tidal CO2 measured by the large breath technique was 28.1 +/- 4.8 mmHg. During the clinical use of QRS-activated ventilation and during earlier studies using an EKG simulator and a test lung, the shock wave occurred invariably at end-expiration even at high heart rates.

Adult↗
PubMed1989

The arterial pressure waveform during acute ventricular failure and synchronized external chest compression.

Methods for mechanical cardiac support by intermittent increases in the intrathoracic pressure have recently been described. In the present study the responses of the arterial pressure waveform to mechanical ventilation with and without synchronized external chest compression (SEC) in the presence of acute ventricular failure (AVF) were evaluated by measuring the systolic pressure variation (SPV). SPV, the difference between the maximal and minimal values of systolic blood during a single positive pressure breath, consists of delta up and delta down components when systolic blood pressure during a short apnea is used as reference value. During intermittent positive pressure ventilation (IPPV) alone, AVF caused SPV to decrease significantly from 8.8 +/- 4.0 to 5.7 +/- 1.9 mm Hg, and further to 3.1 +/- 1.1 mm Hg after volume loading (P less than 0.02). The decrease in SPV was due to a significant decrease in the delta down component, whereas the delta up became the major component of the reduced SPV. The application of SEC caused significant increases in the delta down, delta up, and overall SPV during AVF without volume loading. However, during AVF with volume loading, SEC increased only the delta up component of the SPV, signifying a transient increase in the left ventricular stroke output. It is concluded that the disappearance of the delta down component of the SPV is characteristic of congestive heart failure. Analysis of the arterial waveform offers a readily available monitoring tool for the differentiation of the possible effects on increased intrathoracic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1988

Systolic pressure variation is greater during hemorrhage than during sodium nitroprusside-induced hypotension in ventilated dogs.

The systolic pressure variation (SPV), which is the difference between the maximal and minimal values of the systolic blood pressure (SBP) after one positive-pressure breath, was studied in ventilated dogs subjected to hypotension. Mean arterial pressure was decreased to 50 mm Hg for 30 minutes either by hemorrhage (HEM, n = 7) or by continuous infusion of sodium nitroprusside (SNP, n = 7). During HEM-induced hypotension the cardiac output was significantly lower and systemic vascular resistance higher compared with that in the SNP group. The systemic, central venous, pulmonary capillary wedge pressures, and heart rates, were similar in the two groups. Analysis of the respiratory changes in the arterial pressure waveform enabled differentiation between the two groups. The SPV during hypotension was 15.7 +/- 6.7 mm Hg in the HEM group, compared with 9.1 +/- 2.0 mm Hg in the SNP group (P less than 0.02). The delta down, which is the measure of decrease of SBP after a mechanical breath, was 20.3 +/- 8.4 and 10.1 +/- 3.8 mm Hg in the HEM and SNP groups, respectively, during hypotension (P less than 0.02). It is concluded that increases in the SPV and the delta down are characteristic of a hypotensive state due to a predominant decrease in preload. They are thus more important during absolute hypovolemia than during deliberate hypotension.

Animals↗
PubMed1987

Systolic blood pressure variation is a sensitive indicator of hypovolemia in ventilated dogs subjected to graded hemorrhage.

Systolic pressure variation (SPV) is defined as the difference between the maximum and minimum values of systolic blood pressure following a single positive pressure breath. An increase in the SPV is known to occur clinically during hypovolemia. This study aims to quantify SPV during graded hemorrhage in ventilated dogs, and to compare its reliability relative to other hemodynamic indicators of hypovolemia. Ten anesthetized dogs were mechanically ventilated with a fixed tidal volume. A continuously inflated vest was applied around the chest to maintain the ratio of lung to chest wall compliance similar to that of humans (0.83 +/- 0.12). SPV was further divided into delta up and delta down components relative to apneic (5 s) systolic blood pressure. Dogs were bled 5, 10, 20, and 30% of their estimated blood volume. The measured parameters best correlated to the amount of bleeding were SPV (rs = 0.993), delta down (rs = 0.981), and cardiac output (rs = 0.976). The SPV and its delta down component correlated to the degree of hemorrhage as well as the CO and the pulmonary capillary wedge pressure, and significantly better than the central venous pressure and the mean systemic blood pressure. Thus, SPV and its delta down component are accurate indicators of hypovolemia in ventilated dogs subjected to hemorrhage.

Animals↗
PubMed1987

One-lung high-frequency ventilation in the management of traumatic tear of bronchus in a child.

An 8-yr-old child suffered traumatic bilateral pneumothoraces and a ruptured right main bronchus. Surgical repair of the bronchus was postponed for 18 h after a definite diagnosis was established due to severe hypoxemia and hypercarbia. Only left endobronchial high-frequency ventilation with muscle relaxation corrected this pulmonary dysfunction sufficiently to enable surgical intervention.

Accidental Falls↗
PubMed1985

Forward displacement of the larynx for nasogastric tube insertion in intubated patients.

Simple insertion of a nasogastric (NG) tube was successful in only 52 of 100 anesthetized intubated patients. After the larynx was manually pulled forward, the NG tube was successfully inserted in 33 patients. In the remaining 15 patients, the NG tube was inserted only with the aid of a finger or a laryngoscope used with Magill forceps. The difficulty of NG tube insertion was not correlated with sex, age, weight, or type of endotracheal intubation. Forward displacement of the larynx by manually gripping and lifting the thyroid cartilage is a useful and safe maneuver that facilitates NG tube insertion in anesthetized intubated patients.

Adolescent↗
PubMedDate not supplied

The use of systolic pressure variation in hemodynamic monitoring during deliberate hypotension in spine surgery.

The systolic pressure variation (SPV), which is the difference between the maximal and minimal systolic blood pressure (SP) during one ventilatory cycle, was studied in ten patients during posterior spine fusion. To minimize the blood loss, deliberate hypotension to a mean blood pressure of 50 mmHg was introduced by a continuous infusion of sodium nitroprusside. SPV was further divided into two components, delta up and delta down, using SP during a short apnea as a reference point. All hemodynamic parameters were measured at the beginning of anesthesia, 15 minutes after induction of hypotension, before cessation of nitroprusside infusion, and 15 minutes after the end of the hypotensive period. During the hypotensive period (166 +/- 53 minutes), cardiac output (CO) decreased significantly from 4.83 +/- 1.36 L/min to 3.86 +/- 1.07 L/min (p less than 0.05). Heart rate (HR), central venous pressure (CVP), and pulmonary capillary wedge pressure (PCWP) did not change during this period and bore no correlation to the changes in CO. The only variables that changed during the hypotensive period, in addition to CO, were SPV (from 13.1 +/- 4.9 mmHg to 16.9 +/- 5.1 mmHg, p less than 0.02), and delta down (from 6.0 +/- 3.8 mmHg to 9.9 +/- 6.3 mmHg, p less than 0.05). The delta down segment was the only hemodynamic variable whose changes during the hypotensive period showed a significant (p less than 0.018) correlation with the changes in CO. delta down reflects the degree of decrease in left ventricular stroke output in response to a positive pressure breath, and thus is a sensitive indicator of preload.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Urgent abdominal aortic aneurysm repair in patients over the age 80.

We present three patients with successful surgical repair of abdominal aortic aneurysms with signs of imminent rupture in octogenarians. The patients presented with evidence of severe left ventricular dysfunction and reduced compliance either before or during surgery. Extremely cautious delivery of fluids and of after-load reducing agents was employed under the guidance of measurements of cardiac output and filling pressures from a pulmonary arterial catheter inserted prior to surgery.

Age Factors↗