Biomedical subjects

S E McNulty

Publications and source records attributed to S E McNulty.

7 recordsLinked to original sources

PubMed1992

Should the gas outlet port on membrane oxygenators be routinely scavenged during cardiopulmonary bypass?

Elimination of a volatile anesthetic agent administered prior to the start of bypass through the oxygenator has not been previously described. The purpose of this study was to determine the contamination risk from enflurane used before but not during cardiopulmonary bypass. Enflurane concentration was measured from the gas outlet port of a membrane oxygenator using infrared gas analysis in 11 cardiac surgical patients. The mean peak concentration at the gas outlet port in patients who had a final end-tidal concentration of < or = 0.3% was 0.08 +/- 0.04%, compared to 0.18 +/- 0.05% in patients with a final end-tidal concentration of more than 0.3%, P < 0.001. The elapsed time to reach peak concentration was 8.3 +/- 8.4 minutes, whereas the elapsed time from the peak concentration to 50% of the peak level was 63.1 +/- 25.1 minutes. At the time of peak enflurane release, a concentration of less than 2 ppm was measured at distances of 10 cm or less from the oxygenator gas outlet port in patients with an end-tidal enflurane of < or = 0.3%. In one patient with a final end-tidal enflurane of 1.1%, a contaminant level of 2 ppm could be measured at 95 cm from the oxygenator gas outlet port. This demonstrates that there is a potential risk of contamination from volatile anesthetics used immediately prior to extracorporeal circulation. Minimizing this risk may necessitate routine scavenging of the oxygenator, or simply avoiding increased concentrations of inhalation anesthesia before initiating cardiopulmonary bypass.

Air Pollutants, Occupational↗

PubMed1992

Outcasts in a white-lie society: the enigmatic worlds of people with negative self-conceptions.

Although people with negative self-views want to be liked at some level, they repeatedly enact behaviors that alienate their relationship partners. Why? One possibility is that such persons reside in social environments that offer them little insight into what they are doing wrong. Although persons who had negative self-views elicited unfavorable reactions, they did not appreciate this fact because their interaction partners concealed their aversion behind a facade of kind words. To be sure, the interaction partners of people with negative self-views tended to leak their disdain nonverbally. These negative nonverbal messages proved to be uninformative, however, because people with negative self-views overlooked them. These data imply that people with negative self-views may live in social worlds in which they are deprived of corrective feedback that could allow them to improve themselves.

Adult↗

PubMed1991

An improved nasal prong apparatus for end-tidal carbon dioxide monitoring in awake, sedated patients.

We describe and evaluate a new apparatus that monitors end-tidal carbon dioxide (PETCO2) and augments the inspired oxygen concentration in awake, sedated patients. The unit was evaluated for its effectiveness as an oxygenation device and its accuracy as a predictor of PaCO2 through the correlation of PaCO2 with PETCO2. Twenty cardiac surgical patients, physical status ASA 2-4, participated in this study. The PETCO2 monitoring device consisted of a dual-prong nasal oxygen cannula and a 14-gauge intravenous catheter that was inserted into one limb of the oxygen supply tubing and connected to a Datex gas analyzer (Datex Instrumentation Corp, Helsinki, Finland) to measure PETCO2. The cross-over passage between the prongs was intentionally blocked with the end of a wooden-core cotton swab. The oxygen flow rates were randomly varied (2, 4, and 6 L/min) every 5 minutes, and values for PETCO2 as well as arterial blood samples for analysis of PaCO2 and PaO2 were obtained at the end of each 5-minute period. The accuracy of the system was assessed by comparing the PaCO2-PETCO2 differences (bias) at each oxygen flow rate. The ratios of PETCO2 compared with PaCO2 were 0.98, 0.94, and 0.85, with correlation coefficients of r = 0.81, 0.85, and 0.63, respectively. The PaO2 values were 114, 154, and 183 mm Hg for the corresponding nasal oxygen flow rates of 2, 4, and 6 L/min, respectively. This study indicates that this modified nasal cannula provides supplemental oxygen adequately and yields a satisfactory reflection of the PaCO2 depending on the oxygen flow rate delivered.

Carbon Dioxide↗

PubMed1990

Relationship between arterial carbon dioxide and end-tidal carbon dioxide when a nasal sampling port is used.

End-tidal carbon dioxide (ETCO2) values obtained from awake nonintubated patients may prove to be useful in estimating a patient's ventilatory status. This study examined the relationship between arterial carbon dioxide tension (PaCO2) and ETCO2 during the preoperative period in 20 premedicated patients undergoing various surgical procedures. ETCO2 was sampled from a 16-gauge intravenous catheter pierced through one of the two nasal oxygen prongs and measured at various oxygen flow rates (2, 4, and 6 L/min) by an on-line ETCO2 monitor with analog display. Both peak and time-averaged values for ETCO2 were recorded. The results showed that the peak ETCO2 values (mean = 38.8 mm Hg) correlated more closely with the PaCO2 values (mean = 38.8 mm Hg; correlation coefficient r = 0.76) than did the average ETCO2 values irrespective of the oxygen flow rates. The time-averaged PaCO2-ETCO2 difference was significantly greater than the PaCO2-peak ETCO2 difference (P less than 0.001). Values for subgroups within the patient population were also analyzed, and it was shown that patients with minute respiratory rates greater than 20 but less than 30 and patients age 65 years or older did not differ from the overall studied patient population with regard to PaCO2-ETCO2 difference. A small subset of patients with respiratory rates of 30/min or greater (n = 30) did show a significant increase in the PaCO2-ETCO2 difference (P less than 0.001). It was concluded that under the conditions of this study, peak ETCO2 values did correlate with PaCO2 values and were not significantly affected by oxygen flow rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteries↗

PubMed1990

A comparison of labetalol and nitroprusside for inducing hypotension during major surgery.

The hemodynamic and intrapulmonary shunt effects of intravenous labetalol and nitroprusside were compared during induced hypotension for major spinal surgery. A randomized, double-blind protocol was used in which 20 patients, ASA physical status I or II, received either nitroprusside infusion (n = 10) or labetalol bolus injections of 10 mg every 10 min (n = 10) until mean arterial blood pressure was reduced to 55-60 mm Hg. Pulmonary artery pressures were measured and mixed venous samples obtained via a pulmonary artery catheter. Nitroprusside increased heart rate significantly more than labetalol during the period of hypotension. When compared with prehypotension baseline values, nitroprusside increased heart rate significantly with a concomitant significant decrease in systemic vascular resistance. Cardiac output increased significantly 60 min after hypotension was achieved in patients treated with nitroprusside. Systemic vascular resistance decreased significantly below baseline levels in patients treated with labetalol but without changes in cardiac output, heart rate, or mean pulmonary artery pressure. There was a 122% increase in intrapulmonary shunt with nitroprusside administration, compared with an 11% increase with labetalol. Labetalol was effective for inducing hypotension and was not associated with an increase in heart rate, intrapulmonary shunt, or cardiac output as seen with nitroprusside.

Adult↗

PubMed1988

Temporary A-V sequential pacing using transluminal pacing electrodes.

A case is presented which describes the initiation of atrial-ventricular (A-V) sequential pacing using atrial epicardial wires and an in-situ transluminal ventricular pacing probe. A 68-year-old female with a permanent A-V sequential pacemaker was scheduled for elective aortocoronary bypass. Following sternotomy, pacing function was converted to ventricular pacing (VVI) with the use of electrocautery. A Chandler V-pacing probe was introduced through a Paceport (American Edwards) pulmonary artery catheter and with a paced increase in ventricular rate, the cardiac output increased from 2.8 to 3.2 L.min-1. At the conclusion of cardiopulmonary bypass the patient was in sinus rhythm at a rate of 67.min-1 and was paced to a faster rate using bipolar atrial epicardial wires. The patient subsequently developed intermittent heart block so temporary A-V sequential pacing was established using atrial epicardial wires and the in situ ventricular pacing probe. Pacing was achieved at routine generator output settings of seven milliamps (mA) for both atrium and ventricle and at an A-V interval of 0.120 sec. This resulted in an immediate increase in cardiac output from 3.3 to 4.1 L.min-1. The compatibility of these two pacing systems offers an increased margin of safety in cardiac surgery patients requiring atrial pacing, who are at risk for developing postoperative heart block.

Aged↗

PubMedDate not supplied

The effect of the prone position on venous pressure and blood loss during lumbar laminectomy.

STUDY OBJECTIVE: To determine the effects of three different prone support systems (Andrews spinal surgery frame, Cloward surgical saddle, and longitudinal bolsters) on inferior vena cava (IVC) and superior vena cava (SVC) pressures; the validity of measuring central venous pressure (CVP) for the determination of ideal positioning of the patient; and the relationship among frame type, blood loss, and hemodynamic measurements. DESIGN: Prospective, randomized study of the hemodynamic effects of the prone position. SETTING: Inpatient surgery at a university hospital (regional spinal cord injury treatment center). PATIENTS: Eighteen patients free of significant coexisting disease (ASA physical status I and II) undergoing elective lumbar laminectomy. INTERVENTIONS: Patients were assigned to one of three support frames and measurement of SVC pressure, IVC pressure, and mean arterial pressures (MAP) were obtained supine, prone, and after repositioning. These pressures and measured blood loss were obtained every 15 minutes during the surgical laminectomy portion of the procedure. MEASUREMENTS AND MAIN RESULTS: Patients positioned on the Andrews frame had decreased mean SVC and IVC pressures from 8.7 mmHg and 8.4 mmHg in the supine position to 3.3 mmHg and 1.8 mmHg in the prone position, respectively (p less than 0.001). Prone position CVP also was significantly lower in the Andrews group compared with that in the other two groups (p less than 0.001). Repositioning efforts did not significantly decrease CVP. Blood loss was higher in the Cloward group (1,150 +/- 989 ml) than in the Andrews (245 +/- 283 ml) and bolsters (262 +/- 188 ml) groups (p less than 0.02). CONCLUSIONS: Increased blood loss was not associated with increased SVC or IVC pressure, nor was there any significant correlation between any demographic or hemodynamic variable and blood loss. There was no evidence that CVP is useful in determining the ideal prone position in patients undergoing lumbar laminectomy.

Blood Loss, Surgical↗