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Biomedical subjects

K Waxman

Publications and source records attributed to K Waxman.

118 records · Page 7Linked to original sources
PubMed1981

Use of transcutaneous oxygen sensors to titrate PEEP.

The relationship of transcutaneous oxygen tension (PtcO2) to arterial oxygen tension (PaO2), pulmonary shunt (Qsp/Qt), mixed venous oxygen tension (PVO2), and O2 delivery was determined in patients with respiratory failure in order to explore the possible usefulness of PtcO2 to titrate the level of positive end expiratory pressure (PEEP). Transcutaneous oxygen sensors were applied to the chest of surgical ICU adult patients who were in acute postoperative respiratory failure. The patients had mechanical ventilation with volume ventilators and an intermittent mandatory ventilation (IMV) rate, which allowed normal pH and arterial CO2 tension ventilation (PacO2). Swan-Ganz and arterial catheters were inserted. The blood volume was measured by iodinated I-125-serum albumin and brought into the normal range, before the study began, with appropriate volume therapy. Serial cardiorespiratory data were taken before and after PEEP was increased from zero to 20 cm H2O, in 5 cm increments. PtcO2 correlated well with PaO2 and PV-O2; it was inversely correlated with Qsp/Qt. PtcO2 correlated with O2 delivery in only seven severely ill patients mean alveolar-arterial oxygen tension difference [A-aDO2] was 380 mmHg and the pulmonary shunt was 37%). For the eight other patients, variations in the greatly elevated cardiac output associated with hypoxemia led to poor correlations between PtcO2 and O2 delivery. There was no significant depression of cardiac output in any of the studies. We conclude that the continuous noninvasive nature of PtcO2 monitoring greatly increased the safety and simplicity of PEEP optimization and respiratory management of adult patients with respiratory failure.

Blood Pressure↗
PubMed1981

Physiologic responses to operation in high risk surgical patients.

Fifty-three high risk surgical patients were studied using invasive cardiorespiratory monitoring to gain physiologic perspective of the perioperative period. Multiple hemodynamic and oxygen transport variables were tracked through the preoperative, intraoperative and postoperative periods using frequent sequential measurements. Impairment of cardiac and pulmonary function was measured intraoperatively, but this was compensated by therapy, so that oxygen delivery was maintained. Nonetheless, there was a decrease in oxygen consumption intraoperatively due to decreased oxygen extraction. Postoperatively, there was an increase in cardiac output, oxygen delivery and oxygen consumption. It is postulated that the fall in oxygen consumption intraoperatively may result in a metabolic debt and that a hyperdynamic postoperative state represents the physiologic response necessary to repair the damage caused intraoperatively by relative cellular hypoxia.

Cardiac Output↗
PubMed1980

Hemodynamic, blood volume, and oxygen transport responses to albumin and hydroxyethyl starch infusions in critically ill postoperative patients.

Hemodynamic, plasma volume, and oxygen transport effects were measured after administration of 500 ml of 5% albumin or 6% hydroxyethyl starch (HES) in hypovolemic postoperative patients using a prospectively randomized crossover design. Both agents produced marked and significant improvement in plasma volume and flow as well as small transient increases in arterial and venous pressures, urine output, colloidal osmotic pressure (COP), and oxygen transport. The authors conclude that HES is a safe, inexpensive, effective plasma expander that has hemodynamic effects similar to those of other colloids. It was apparent from these and other studies that clinically stable postoperative patients may have appreciable blood volume deficits. Routine vital signs correlated poorly with the preinfusion control hemodynamic values or the changes in blood volume status after volume loading. Normal cardiac output, central venous pressure (CVP), and pulmonary arterial wedge pressure (WP) values are commonly seen in critically ill postoperative patients who, nevertheless, may be hypovolemic. Measurement of changes in these variables after a fluid challenge is a useful way to assess plasma volume status.

Adult↗
PubMed1980

Continuous transcutaneous oxygen monitoring during respiratory failure, cardiac decompensation, cardiac arrest, and CPR. Transcutaneous oxygen monitoring during arrest and CPR.

The transcutaneous oxygen sensor (PtcO2), which has been used to predict PaO2 in neonates, recently has been shown to follow changes in oxygen delivery, rather than PaO2 during shock and hypoxia in dogs. Six preterminal patients were continuously monitored with PtcO2 and monitored hemodynamically at frequent intervals during cardiac decompensation, arrest, and cardiopulmonary resuscitation (CPR). The weighted mean correlation coefficients between PtcO2 and O2 delivery as well as between PtcO2 and cardiac output were 0.94 and 0.96, respectively. Five patients died of severe ARDS and 1 patient died intraoperatively of hemorrhagic shock. Four patients were monitored 1-7 days before shock occurred. The correlation between PtcO2 and PaO2 was 0.91 during periods of normal cardiac output in the preterminal period. During cardiac decompensation, the cardiac output, PtcO2, and mixed venous oxygen tension (PcO2) of 25 torr was reached, the PtcO2 fell below the PvO2. This also corresponded to a decrease in VO2. The mean VO2 was 142 +/- 24 ml/min x M2 for PtcO2 values > torr, and 75 +/- 15 ml/min x M2 for PtcO2 < 25 torr (p < 0.01). A PtcO2 of > 40 torr corresponded to normal cardiac index, O2 delivery, VO2, PvO2, and arterial pH (pHa) while a PtcO2, of < 25 torr corresponded to large reductions of these variables. A PtcO2 of < 25 torr preceded cardiac arrest by 43 +/- 28 min.

Cardiac Output↗
PubMed1980

Cardiovascular effects of anesthetic induction with ketamine.

Anesthetic induction with ketamine has been reported to maintain or improve cardiovascular performance in severely ill patients. Using invasive cardiovascular monitoring, we studied physiologic responses to a single dose of ketamine in 12 critically ill patients. Six patient demonstrated decreases in ventricular contractility, and four had decreases in cardiac output. Mean arterial blood pressure decreased in four patients. Pulmonary venous admixture increased in four of six patients, while oxygen consumption decreased in eight of 11 patients. Thus, a single dose of ketamine produced decreases in cardiac and pulmonary performance and in peripheral oxygen transport in this group of patients. It is proposed that in severely ill patients, preoperative stress may alter the usual physiologic responses to ketamine administration, and adverse effects may predominate. Ketamine, therefore, should be used with caution for induction of anesthesia in critically ill and in acutely traumatized patients until additional studies and further information on cardiovascular responses to ketamine are available.

Anesthesia↗
PubMedDate not supplied

Regional flow during experimental hemorrhage and crystalloid resuscitation: persistence of low flow to the splanchnic organs.

UNLABELLED: BACKGROUND AND METHODS. Rapid changes in cardiac output (CO) and organ perfusion occur with hemorrhagic shock and fluid resuscitation. To assess regional alterations of flow, 40 Sprague-Dawley male rats were subjected to hemorrhagic shock and crystalloid resuscitation under halothane anesthesia. Polyethylene microspheres were injected before and after hemorrhage and after resuscitation. At sacrifice, brain, lungs, heart, liver, intestine, spleen and kidneys were harvested, weighed and radioactivity counted. Changes in mean arterial pressure, oxygen consumption, organ flow and CO were also measured. RESULTS: Cardiac output decreased during hemorrhage (P less than 0.01), it increased with resuscitation but did not return to baseline even with infusion of fluid volumes of three times the blood loss. Flow decreased during hemorrhage in all organs, but the difference was not statistically significant in the liver (P greater than 0.05), since a larger percentage of CO was maintained as hepatic perfusion. During resuscitation, flow to brain and kidneys increased over the percentage values expected by increased CO (P less than 0.01), but flow to the liver did not increase significantly. Flow to small bowel remained depressed (P less than 0.005). CONCLUSIONS: Following hemorrhage there is hypoperfusion of all splanchnic organs; however, flow to the liver decreases least. Crystalloid resuscitation in our model failed to return CO to baseline. Blood supply to intestine remained depressed in disproportion to CO both after hemorrhage and resuscitation and hepatic blood flow remained decreased after resuscitation.

Animals↗
PubMedDate not supplied

Safety and efficacy of glycerol and amino acids in combination with lipid emulsion for peripheral parenteral nutrition support.

The safety and efficacy of administering lipid emulsion with ProcalAmine, a glycerol-based parenteral nutrition solution, for peripheral nutrition has not been previously studied. Thirty-four patients recovering from major trauma or surgery were studied while receiving a peripheral parenteral nutrition regimen of either ProcalAmine with 10% lipid emulsion (group 1) or ProcalAmine with 20% lipid emulsion (group 2) for up to 5 days postinjury. Daily dose was 45 mL/kg ProcalAmine, providing 1.35 g of amino acids/kg and 1.35 g of glycero/kg, and 500 mL/day lipid emulsion. The mean daily nitrogen balance was -0.3 g/day in group 1 and -4.1 g/day in group 2. There was no progressive accumulation of circulating glycerol, and urinary glycerol excretion was minimal (less than 0.2 g/day), indicating effective utilization of glycerol as an energy substrate. Our finding that nitrogen balance was better with 10% fat emulsion suggests a limitation in fat utilization in this setting. Both regimens were well tolerated; there were no adverse clinical reactions and no occurrences of phlebitis in either group.

Adolescent↗