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Biomedical subjects

L E Kirson

Publications and source records attributed to L E Kirson.

11 recordsLinked to original sources
PubMed1996

Impact of respiratory acid-base status in patients with pulmonary hypertension.

BACKGROUND: The perioperative management of patients undergoing mitral valve replacement (MVR) with pulmonary hypertension from mitral stenosis may be complicated by increased pulmonary vascular resistance. The purpose of this study was to examine the influence of respiratory acid-base status on the pulmonary hemodynamic indices of patients with pulmonary hypertension before and after MVR. METHODS: Ten patients with pulmonary hypertension from mitral stenosis (mean preoperative systolic pulmonary artery pressure, 73 +/- 8 mm Hg) undergoing MVR were studied in the operating room before and after MVR. Arterial partial pressure of carbon dioxide was manipulated by the addition of 5% carbon dioxide to the breathing circuit. Hemodynamic data were collected as the partial pressure of carbon dioxide rose from 30 mm Hg to 50 mm Hg and decreased back to 30 mm Hg. RESULTS: There were no differences in mean pulmonary artery pressure or pulmonary vascular resistance before and after MVR. Before MVR, mean pulmonary artery pressure increased from 32 +/- 1 mm Hg to 48 +/- 1 mm Hg as the partial pressure of carbon dioxide rose from 30 mm Hg to 50 mm Hg (p < 0.05), and pulmonary vascular resistance rose from 379 +/- 30 to 735 +/- 40 dynes.second.cm-5 (p < 0.05). These effects on mean pulmonary artery pressure and pulmonary vascular resistance were not different after MVR. CONCLUSION: Respiratory acid-base status has a profound impact upon pulmonary vascular resistance in patients with pulmonary hypertension from mitral stenosis undergoing MVR. This impact persists in the immediate postoperative period. We conclude that respiratory acidemia should be avoided in these patients, whereas respiratory alkalemia may be used to help minimize pulmonary vascular resistance.

Acid-Base Imbalance↗
PubMed1996

Adenosine is a selective pulmonary vasodilator in cardiac surgical patients.

OBJECTIVE: The purpose of this study was to examine and compare the systemic and pulmonary hemodynamic effects of a central venous infusion of adenosine in cardiac surgical patients. DESIGN: Prospective; each subject served as his/her own control. SETTING: University Hospital and Veteran's Affairs Medical Center. PATIENTS: Ten cardiac surgical patients (age 56 +/- 6 years) were studied in the operating room under general anesthesia after weaning from cardiopulmonary bypass. Pulmonary vascular resistance (PVR), systemic vascular resistance (SVR), mean pulmonary arterial pressure (MPAP), and mean systemic arterial pressure (MAP) were determined before, during, and after central venous infusion of adenosine (50 micrograms/kg/min) for 15 min. Statistical analysis was by analysis of variance; significance was accepted at p < 0.05. RESULTS: Adenosine produced selective vasodilation of the pulmonary vascular bed: both PVR and MPAP were significantly reduced during adenosine infusion without changes in either SVR or MAP. PVR and MPAP returned to preinfusion levels after cessation of the infusion. Adenosine effectively reduced PVR and pulmonary arterial pressure without decreasing SVR or systemic arterial pressure. CONCLUSIONS: Adenosine may be used clinically as a selective pulmonary vasodilator to optimize pulmonary hemodynamics without adverse systemic hemodynamic effects in cardiac surgical patients. It may be particularly valuable in patients with right heart dysfunction by selectively lowering right ventricular afterload.

Adenosine↗
PubMed1994

A system for monitoring the delivery of ventilating gas to the oxygenator during cardiopulmonary bypass.

Present methods for monitoring delivery of ventilating gas to the oxygenator during cardiopulmonary bypass have not been critically examined despite the occurrence of catastrophic gas flow disturbances. Currently, a flowmeter regulates the delivery of gas into the proximal portion of the gas circuit, and at these institutions, an oxygen (O2) analyzer positioned downstream of the flowmeter monitors oxygen concentration of the flowing gas. However, these devices are incapable of accurately analyzing the flow of gas into the oxygenator housing. In response to this deficiency, the authors developed and evaluated, in a laboratory model, an alternative system for monitoring ventilating gas flow. The system measured quantity of gas flow by pneumotachography, and oxygen concentration of the ventilating gas with a polarographic oxygen analyzer at the gas inlet port of the oxygenator. Five types of disturbances in gas delivery, which have been documented in the medical literature, were created in a laboratory model: (1) O2 concentration variation, (2 and 3) oxygenator gas line disconnection at each of two locations in the gas circuit, (4) a decrease in gas flow to the oxygenator secondary to a leak in the gas circuit, and (5) excess gas flow to the oxygenator. The capability of currently used monitoring devices (flowmeter and "passive" O2 analyzer) with the proposed monitoring system (pneumotachograph and "aspirating" O2 analyzer) was compared for detecting these abnormalities in gas delivery. The currently used devices were only able to satisfactorily detect a change in oxygen concentration. In contrast, the proposed system was able to rapidly detect all types of gas delivery disturbance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

The influence of respiratory acid-base status on adult pulmonary vascular resistance before and after cardiopulmonary bypass.

Respiratory acid-base status has recently been shown to affect pulmonary vascular resistance (PVR) in adults following cardiac surgery. The purpose of this study was to examine what influence cardiopulmonary bypass has on the pulmonary vascular response to changes in respiratory acid-base status. Fifteen consecutive patients undergoing aortocoronary bypass were studied under general anesthesia both before and after cardiopulmonary bypass. Arterial PCO2 was manipulated by the addition of 5 percent carbon dioxide to the breathing circuit. Both before and after bypass, PVR increased significantly as PCO2 rose from 30 mm Hg to 50 mm Hg (p < 0.05). The PVR returned to baseline as PCO2 was returned to 30 mm Hg. These data suggest that increased PVR induced by hypercarbic acidemia is not simply a result of the effects of cardiopulmonary bypass on the pulmonary circulation. Instead, we conclude that respiratory acid-base status is an important determinant of adult PVR. We believe these data may be helpful in the treatment of mechanically ventilated patients, since patients are at particular risk of having abnormalities develop in respiratory acid-base status.

Acid-Base Equilibrium↗
PubMed1993

Influence of hydrogen ion concentration versus carbon dioxide tension on pulmonary vascular resistance after cardiac operation.

Disturbances of respiratory acid-base status are common in patients supported with mechanical ventilation of the lungs after cardiac operations. This study was conducted with two protocols. The purpose was to determine whether respiratory acid-base status influences pulmonary vascular resistance in adults after cardiac operations and whether the influence is mediated by hydrogen ion concentration or carbon dioxide tension. Patients were studied while under general anesthesia immediately after aorta-coronary bypass. In the first protocol, with seven patients, arterial carbon dioxide tension was manipulated by the addition of 5% carbon dioxide to the breathing circuit. Pulmonary vascular resistance index was determined as arterial carbon dioxide tension rose from 30 mm Hg to 50 mm Hg and back to 30 mm Hg. In the second protocol, with 10 different patients, hydrogen ion concentration was manipulated by the addition of 0.2N hydrochloric acid, sodium bicarbonate, or both as arterial carbon dioxide tension was held constant. We used analysis of variance for statistical data. The results of the first protocol showed that pulmonary vascular resistance index rose by 44% (p < 0.05) as arterial carbon dioxide tension rose from 30 to 50 mm Hg. The results of the second protocol showed that changes in pulmonary vascular resistance index were parallel to changes in hydrogen ion concentration as arterial carbon dioxide tension was held constant (p < 0.05). These data demonstrate that respiratory acid-base status is an important determinant of pulmonary vascular resistance in the adult after cardiac operations. Furthermore, these data suggest the effect is mediated by hydrogen ion concentration, not carbon dioxide tension.

Acid-Base Equilibrium↗
PubMed1989

Low-dose intrathecal morphine for postoperative pain control in patients undergoing transurethral resection of the prostate.

Thirty patients undergoing lidocaine spinal anesthesia for transurethral resection of the prostate (TURP) were studied to evaluate the effectiveness of low-dose intrathecal morphine (ITM) for postoperative analgesia. In a double-blinded fashion, groups of ten patients received either 0.1 mg morphine, 0.2 mg morphine, or placebo (control group) intrathecally with lidocaine 75 mg. Standard postoperative analgesics were available to all patients. Patients receiving 0.1 mg or 0.2 mg morphine reported significantly less postoperative pain as assessed by an inverse numerical visual pain scale and required significantly fewer postoperative analgesic interventions than the control group. There was no difference between the 0.1 mg ITM and 0.2 mg ITM groups with regard to severity of postoperative pain or analgesic requirements. The incidence of nausea and vomiting was significantly higher in the group receiving 0.2 mg ITM than in the control group. Six patients (60%) in the 0.2 mg ITM group, two patients (20%) in the 0.1 mg ITM group, and one patient (10%) in the control group experienced nausea and vomiting. No clinically evident respiratory depression occurred in any of the subjects. The authors conclude that administration of 0.1 mg or 0.2 mg of morphine intrathecally is effective in reducing postoperative pain following TURP and that 0.1 mg ITM is not associated with nausea and vomiting.

Clinical Trials as Topic↗
PubMed1979

Mental nerve paresthesia secondary to sickle-cell crisis.

Two individual cases in which mental nerve paresthesia developed concurrently with sickle-cell crisis are described. A brief review of the hemoglobinopathies follows, with genetic considerations and clinical manifestations discussed.

Adolescent↗