The predictive value of gastric reactance for postoperative morbidity and mortality in cardiac surgery patients.

No useful method to directly monitor the level of end organ tissue injury is currently available clinically. Gastric reactance has been proposed to measure changes in a tissue structure caused by ischemia. The purpose of this study was to assess whether gastric reactance is a reliable, clinically relevant predictor of complications and a potentially useful tool to assess hypoperfusion in cardiovascular surgery patients. The value of gastric reactance measurements, standard hemodynamic and regional perfusion variables, and scores to predict postoperative complications were compared in 55 higher risk cardiovascular surgery patients with cardiopulmonary bypass. Low frequency gastric reactance, X(L), had a significant predictive value of postoperative persistent shock requiring more than 48 h of vasopressors and associated complications, before, during and after surgery (p < 0.05). Results suggest that reactance is an earlier predictor of patients at risk than all other variables tested. Patients with a high reactance (X(L) > 26) before surgery had a significantly higher incidence of complications, higher mortality and more days in the ICU than patients with a low reactance (X(L) < 13). X(L) was found to be a reliable and clinically relevant measurement. These results justify further clinical research to explore how this information may be used to improve patient management.

Gastric impedance spectroscopy in elective cardiovascular surgery patients.

Impedance spectroscopy has been proposed as a method of monitoring mucosal injury due to hypoperfusion and ischemia in critically ill patients. The present study characterizes human gastric impedance spectral changes under gastric hypoperfusion in patients undergoing cardiovascular surgery, and evaluates spectral differences between patients with no evidence of gastric ischemia and complications, and patients who developed ischemia and complications. Cole and Kun parameters were calculated over time to characterize changes as tissue injury progresses. Gastric ischemia was determined by air tonometry. Impedance spectroscopy spectra were obtained from 63 cardiovascular surgery patients. The recorded spectra were classified into three groups: group 1 for patients without ischemia or complications, group 2 for patients with a short period of ischemia (less than 2 h) and group 3 for patients with more than 4 h of gastric ischemia and complications. Two distinct dispersion regions of the spectra centered at about 316 Hz and 215 kHz become clearer as tissue damage develops. The average spectrum in group 3 shows a significant difference in tissue impedance at all frequencies relative to group 1. The parameters obtained for human gastric tissue show significant changes that occur at different times and at different frequencies as ischemia progresses, and could be correlated with patient outcome. This confirms our hypothesis that hypoperfusion and ischemia cause evident changes in the impedance spectra of the gastric wall. Therefore, this technology may be a useful prognostic and diagnostic monitoring tool.

Gastric Impedance Spectroscopy in Cardiovascular Surgery Patients vs. Healthy Volunteers.

Impedance spectroscopy has been proposed as a method of monitoring mucosal injury due to hypoperfusion and ischemia in the critically ill. The present study evaluates spectral differences in elective cardiovascular surgery patients compared with the impedance spectra of the gastric mucosa in healthy adults. An impedance spectroscopy probe and nasogastric tube (ISP/NGT) was placed into the stomach of 77 heart surgery and 21 healthy volunteers. The recorded impedance spectra were classified into 3 groups: group 1 for healthy volunteers; group 2 for patients with neither ischemia nor complications; and group 3 for patients with ischemia and complications during the first 3 days in the recovery unit. There were statistical differences in resistance (p<0.001) and reactance (p<0.001) among the 3 groups. The results show that impedance spectra are distinct and significantly different in patients with probable ischemic mucosal injury compared to healthy subjects, and therefore this technology may be a useful prognostic and diagnostic monitoring tool.

[A system for non-invasive measurement of arterial pulse velocity in different vascular territories]. / Sistema para la medición no invasiva de la velocidad del pulso arterial en diferentes territorios vasculares.

Blood pulse wave velocity (PWV) is a known index of arterial rigidity and its measurement has proved its usefulness in the study of some cardiovascular pathologies. In this study we describe the design and implementation of a system for noninvasive PWV determination in the aorto-braqui-humero-radial (A-->h), aorto-ileo-femoro-pedial (A-->f) and aorto-carotid (A-->c) regions. This system was examined with 36 normotensives (NT) and 34 hypertensives (HT) patients with (LVH, n = 20) and without (WLVH, n = 14) left ventricular hypertrofy. The equipment consist of a personal computer with an analog to digital converter and hardware and software items adapted to take simultaneously the electrocardiogram (ECG), two photopletismographic pulses and one oscilometric pulse. The Q-pP interval (time between a Q ECG wave and distal blood pulse) and the distance to the register sites are taken into account to calculate the beginning of cardiac prexpulsive period (time zero of pulse trip) which allow the determination of the PWV (in meters/second) from the aortic root to the distal point of the via. PWV was significant higher (p < 0.001) in HT vs. NT (A-->h: 9.3 +/- 2.6 vs. 7.2 +/- 0.8, A-->c: 9.5 +/- 2.8 vs. 6.0 +/- 1.9 and A-->f: 9.5 +/- 1.8 vs. 7.2 +/- 0.9) in each evaluated arterial region. Same thing occurred in cases with LVH vs. WLVH (A-->h: 10.5 +/- 1.6 vs. 8.0 +/- 1.9, A-->c: 10.2 +/- 1.9 vs. 8.0 +/- 1.9 and A-->f: 10.5 +/- 2.0 vs. 8.6 +/- 1.2) (p < 0.025). This is consistent with the relationship more pressure [symbol: see text] more rigidity and with other reports. This method may have clinical application.

[Provocation and measurement of retrograde pulsatile wave velocity in normal subjects and patients with systemic hypertension]. / Provocación y medición de la velocidad de la onda pulsátil retrógrada en sujetos normales e hipertensos sistémicos.

UNLABELLED: There are not published incruent methods of provocation and/or measurement of the velocity of the reflexive arterial pulse wave. This phenomenon is implicated in the pathogenesis of arterial hypertension. We describe that during compressive sphygmomanometry (CS) done in the forearm, reflexive waves are provoked that are register in the arm with an equipment developed by us, which measures the velocity of the antegrade (APWV) and the provoked retrograde (RPWV) pulse waves. The procedure consist in: 1) detection, capture and digitalization by pneumatic cuffs of oscillopulses of the arm and the forearm, 2) detection of finger photopulse to control the efficacy of CS, 3) measurement of APWV and RPWV by taking the conduction time travel distance of pulse wave between detectors arm-forearm and forearm-arm respectively. Thirty normal case (group A, GA) and 37 essential systemic hypertensive patients (group B, GB) were studied. Sixteen cases of GB had left ventricular hypertrophy (LVH). RESULTS: A reflexive wave was provoked in 99% of cases. The APWV (m/s) was 6.0 +/- 0.9 vs 7.5 +/- 1.3, p < 0.001 for GA and GB respectively. The RPWV (m/s) of the same groups were 1.8 +/- 0.3 vs 2.5 +/- 0.7, p < 0.001. The hypertensive cases with LVH had more RPWV than the cases without it (2.7 +/- 0.6 vs 2.3 +/- 0.6, p = 0.07). CONCLUSION: Hypertensive cases vs normals had higher antegrade and retrograde pulse wave velocities possible due to the major degree of arterial rigidity of the former. The method may be used in study of chronic arteriopathy.