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Biomedical subjects

T W Latson

Publications and source records attributed to T W Latson.

At least 19 recordsLinked to original sources
PubMed1996

Evaluation of laboratory coagulation and lytic parameters resulting from autologous whole blood transfusion during primary aortocoronary artery bypass grafting.

STUDY OBJECTIVE: To determine if autologous blood reinfusion influences overall hemostatic function following aortocoronary artery bypass graft (CABG) surgery, and if so, where the predominant area of this influence lies. DESIGN: Prospective, with control values on each patient. SETTING: Cardiac operating room of a major university-affiliated county hospital. PATIENTS: 20 patients undergoing elective CABG surgery. INTERVENTIONS: Following heparinization, and prior to cardiopulmonary bypass (CPB), venous blood (average 4.9 ml/kg) was removed via an indwelling internal jugular catheter into a preservative-free plastic transfer pack unit and stored without agitation at room temperature. This autologous whole blood was reinfused after systemic protamine reversal of heparin. Blood samples for analysis were drawn immediately before and 5 minutes after completion of the reinfusion. MEASUREMENTS AND MAIN RESULTS: Autologous blood reinfusion appears to be significantly related to increased hemoglobin, hematocrit, platelet count, fibrinogen, plasminogen, and antiplasmin levels. The prothrombin time and activated partial thromboplastin times decreased significantly, whereas activated clotting times and D-dimer levels were unchanged. Significant increases occurred in the following thromboelastography parameters: maximum amplitude, amplitude 60 minutes after the maximum amplitude, and whole blood clot lysis index. Reaction time and coagulation time were not statistically different from control values. CONCLUSIONS: Significant improvements in coagulation and lytic parameters occur following CPB after the infusion of autologous blood. These improvements in coagulation indices may be the result of the infused blood or hemoconcentration, which is also known to occur during this period. Additional control studies are needed to differentiate these effects.

Anticoagulants↗
PubMed1994

Autonomic reflex dysfunction in patients presenting for elective surgery is associated with hypotension after anesthesia induction.

BACKGROUND: Autonomic reflex dysfunction in patients with diabetes is associated with an increased incidence of hypotension after induction of anesthesia. Whether this finding can be extrapolated to patients with autonomic dysfunction from other causes (e.g., advanced age, hypertension, altered ventricular function) has not been established. METHODS: The authors investigated whether autonomic reflex dysfunction in a more generalized patient group (26 consecutively consenting day-surgery patients older than 39 yr) was similarly associated with the occurrence of hypotension after induction. Preoperative tests of autonomic function included: Valsalva maneuver, change in heart rate with forced breathing, change in heart rate and blood pressure with standing, and spectral analysis of heart rate variability. Anesthesia was induced with 3-5 mg/kg thiopental, 2 micrograms/kg fentanyl, and 60% N2O; 0.1 mg/kg vecuronium was used for paralysis; 0-1.5% isoflurane was added for maintenance of anesthesia after intubation. Noninvasive measurements of mean blood pressure were obtained every minute for 10 min after induction and then every 3 min until skin incision. RESULTS: Twelve patients developed hypotension (mean blood pressure < 70 mmHg), and 14 patients did not. Measurements of autonomic reflex function were significantly more abnormal in the patients who developed hypotension (P < 0.006 for Valsalva measurements, heart rate variability parameters, and change in heart rate with forced breathing). Using critical test values for autonomic tests, the incidence of hypotension was 67-83% in patients with autonomic nervous system dysfunction versus 9-17% in other patients. CONCLUSIONS: The results document that: (1) some degree of autonomic reflex dysfunction is not uncommon in patients older than 39 yr presenting for elective surgery, and (2) such dysfunction is associated with an increased incidence of hypotension when using the described induction technique.

Adult↗
PubMed1993

Perioperative measurements of interleukin-6 and alpha-melanocyte-stimulating hormone in cardiac transplant patients.

Interleukin-6 (IL-6) and alpha-melanocyte-stimulating hormone (alpha MSH) are important modulators of the immunologic response to tissue injury and antigenic challenge. Serial changes in the plasma concentrations of these two peptides were measured in 12 patients undergoing heart transplantation. Tissue concentrations of IL-6 in atrial samples from both donor and recipient hearts were also compared. Plasma IL-6 concentration remained stable prior to cardiopulmonary bypass (CPB), initially decreased with the onset of CPB, and then increased significantly over control values at the end of CPB (180 +/- 40 v 53 +/- 60 pg/mL). Plasma IL-6 remained elevated for at least 60 minutes after CPB, and then it returned to control values by 24 hours postoperatively (67 +/- 9 pg/mL). Examination of IL-6 changes after CPB in 10 additional patients undergoing nontransplant cardiac surgery with CPB revealed a similar elevation in IL-6 at 60 minutes after CPB (290 +/- 76 pg/mL). However, IL-6 in the nontransplant group remained significantly elevated at 24 hours (138 +/- 42 pg/mL). These combined results suggest that CPB causes a marked increase in IL-6, and that implantation of a new heart in transplant patients does not augment this increase. The return of IL-6 to control values by 24 hours in the patients who have had transplants suggests that immunosuppression has an appreciable effect on IL-6 at this time. In contrast to IL-6, plasma alpha MSH never increased above control values.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Effects of surgical stimulation on autonomic reflex function: assessment by changes in heart rate variability.

Analysis of small oscillations in heart rate (known as heart rate variability or HRV) associated with the activity of homeostatic reflexes can provide a noninvasive measure of autonomic reflex function. We have investigated the effects of surgical stimulation on autonomic reflex function by assessment of changes in HRV. Healthy female patients undergoing laparoscopic tubal ligation were anaesthetized with either thiopentone-nitrous oxide-isoflurane (group I; n = 13) or continuous propofol infusion (group P; n = 13). Power spectral measurements of HRV (HRVtot = total HRV power; %HRVlo = percent of HRV power in the low frequency range) were obtained at the following times; control; before incision; after incision (3 min, 10 min and before skin closure). Compared with control values, measurements of HRVtot before incision were reduced significantly in both groups (group P: 16 (SEM 3)% of control; group I: 2.5 (0.7)% of control). With surgical stimulation, mean HRVtot in group P was restored to 55 (13)% of control (P < 0.01 compared with measurement before incision), whereas mean HRVtot in group I remained at less than 4% of control (ns). %HRVlo increased also in group P, from 49 (7)% to 75(3)% (P < 0.05), consistent with a shift in sympathetic-parasympathetic balance towards sympathetic dominance. These results suggest that surgical stimulation may have significant effects on the autonomic reflexes mediating HRV, and that such effects vary with anesthetic technique.

Adolescent↗
PubMed1993

Ventilation, thermal noise, and errors in cardiac output measurements after cardiopulmonary bypass.

BACKGROUND: The authors observed transient increases in the amplitude of respiratory variations in pulmonary artery blood temperature in many patients after cardiopulmonary bypass (CPB). This increased "thermal noise" may significantly influence measurements of thermodilution cardiac outputs (TDCO) performed during this time. METHODS: The authors recorded the peak-to-peak amplitude of respiratory variations in pulmonary artery blood temperature in 15 patients during the first 35 min after CPB. Possible relationships between the amplitude of these variations and the magnitude of temperature differences between commonly monitored body temperature sites (nasopharyngeal, rectal, bladder, and pulmonary artery) were also examined. In ten additional patients, the authors investigated the influence of these increased respiratory variations on TDCO measurements by correlating the maximum variation in three successive TDCO measurements with the peak-to-peak amplitude of the respiratory variations in pulmonary artery blood temperature. Potential error in TDCO measurements caused by these increased respiratory variations in pulmonary artery blood temperature were also examined using model calculations of the effects of respiratory variations in pulmonary artery blood temperature on measured TDCO thermal areas. RESULTS: In the first 15 patients, the mean amplitude of respiratory variations in pulmonary artery blood temperature after CPB (mean +/- SEM) were: (1) within 5 min after CPB, 0.037 +/- 0.004 degrees C; (2) 10 min after #1, 0.025 +/- 0.003 degrees C; (3) 20 min after #1, 0.019 +/- 0.003 degrees C; and (4) 30 min after #1, 0.012 +/- 0.002 degrees C. There were no significant correlations between the magnitude of the respiratory variation in pulmonary artery blood temperature and the observed temperature differences between body sites. Four patients had pulmonary artery blood temperature variations in excess of the maximum amplitude previously reported in man (0.05 degrees C). In the next ten patients, the maximum variation between three successive TDCO measurements taken at specified times in the respiratory cycle (end inspiration, end exhalation, and 3 s after end exhalation) was significantly correlated with the amplitude of respiratory variations in pulmonary artery blood temperature (r = 0.83, P < 0.001). Four patients with increased respiratory variations in pulmonary artery blood temperature had variations in TDCO measurements exceeding 2 l/min. Subsequent model calculations demonstrated that the magnitude of potential error in TDCO measurements is dependent on both the amplitude of the respiratory variations in pulmonary artery blood temperature and the baseline cardiac output. On the basis of these thermal area calculations, potential errors of 15-50% could be caused by respiratory variations in pulmonary artery blood temperature > 0.05 degrees C. CONCLUSIONS: The authors concluded that respiratory variations in pulmonary artery blood temperature are transiently increased in many patients after CPB, and that this increased "thermal noise" may cause significant errors in TDCO measurements.

Body Temperature↗
PubMed1992

Changes in plasma atrial natriuretic peptide concentration during heart transplantation.

Examination of changes in plasma atrial natriuretic peptide (ANP) concentrations during heart transplantation may provide important information about factors influencing plasma ANP in patients with severe heart failure. Serial changes in plasma ANP during heart transplantation, and atrial content of ANP in native and donor atria, were measured in 12 patients. Preoperative plasma ANP was elevated in all patients (387 +/- 77 pg/mL), whereas atrial content of ANP in native atria was reduced (0.36 +/- 0.082 micrograms/mg protein). Preoperative plasma ANP did not correlate with hemodynamics, but was negatively correlated with creatinine clearance (r = -0.76, P < .01). Intraoperative plasma ANP prior to transplantation was strongly correlated with intraoperative plasma ANP after transplantation (r = 0.84, P < .001). Although postoperative plasma ANP was reduced from preoperative plasma ANP by 75%, these two measurements were also significantly correlated (r = 0.70, P < .02). Postoperative plasma ANP was not correlated with hemodynamics, but was negatively correlated with both creatinine clearance (r = -0.65, P < .05) and content of ANP in the native atria (r = -0.75, P < .01). Multiple linear regression analysis suggested that up to 85% of the variability of early postoperative plasma ANP could be accounted for by the variability in these latter two parameters. The decrease in native atrial ANP content, in the context of elevated plasma ANP concentration, is consistent with prior animal studies suggesting that severe heart failure induces cellular adaptations favoring accelerated ANP synthesis and secretion (with resultant reduction in tissue content).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Pheochromocytoma with extension into the inferior vena cava: a case report.

Eleven cases of pheochromocytoma with extension into the inferior vena cava have been reported previously. This report describes a case of a right adrenal pheochromocytoma with extension into the inferior vena cava that was removed with the aid of cardiopulmonary bypass and circulatory arrest.

Adrenal Gland Neoplasms↗
PubMed1988

Effect of nitroglycerin on aortic impedance, diameter, and pulse-wave velocity.

The effects of an intravenous infusion of 1 microgram/kg/min nitroglycerin were studied on systemic arterial properties in nine acutely instrumented dogs. Aortic impedance and pulse-wave velocity were calculated from measured pressure and flow signals collected during random ventricular pacing. Central aortic diameter was simultaneously determined with ultrasonic dimension crystals. Mean blood pressure was maintained constant to avoid the confounding effects of passive, pressure-induced changes in vascular properties. Nitroglycerin both reduced the amplitude of peripheral vascular reflections and delayed the return of these reflections to the aortic root. This reflection delay was manifested as a consistent leftward shift in both impedance modulus and phase. The magnitude of this reflection delay could not be entirely accounted for on the basis of the measured changes in average pulse-wave velocity along the aorta.

Animals↗
PubMed1986

Time sequential prediction of ventricular-vascular interactions.

A new analytical method (sequential convolution) for describing ventricular-vascular interactions was used to predict instantaneous pressure and flow in four isolated canine left ventricles ejecting into a computer-simulated arterial system. Ventricular pumping ability was described by a load-independent elastance, [E*(t)] combined with a ventricular internal resistance. "Arterial" properties were characterized using a time-based impulse response function that is derived from impedance measurements. Sequential convolution was then used to couple these independent descriptions of ventricular and vascular properties. Predicted pressure-volume trajectories, as well as instantaneous pressures and flows, closely matched the experimental data. Stroke volume, peak pressure, and peak flow were typically within 5% of measured values. This method provides a powerful analytical technique for examining ventricular-vascular interactions and has potential application in evaluating the ventricular-loading effects of more complex in vivo vascular properties.

Animals↗