Cardiovascular Status during Ketamine Anesthesia in the Fetal Lamb

Abstract

To determine the effects of maternal ketamine anesthesia on fetal hemodynamic and cardiac function, a study was carried out on 8 chronically catheterized fetal lambs. Ketamine was administered intravenously to the mother every 15 min during 1 h. The fetal PO₂ and pH remained within physiological limits whereas the PCO₂ decreased from 44.35 ± 1.36 to 37.32 ± 4.75 Torr (p < 0.05). The following changes of the fetal heart systolic time intervals were observed: a progressive lenghtening of the preejection period (PEP) (from 52 ± 10 to 63 ± 11 ms, p < 0.01), a shortening of the ejection time (ET) and a significant increase of the PEP/ET ratio (from 0.32 ± 0.04 to 0.47 ± 0.01, p < 0.01). The two components of PEP, electromechanical delay and the isovolumetric contraction time were both prolonged. A progressive rise of fetal systolic and diastolic pressures was also noted (p < 0.01). Fetal heart rate increased (145 ± 33 to 190 ± 28 beats/min, p < 0.01) and cardiac beat-to-beat variability decreased (from 0.028 to 0.009, p < 0.01) during the ketamine anesthesia. This study demonstrates that maternal anesthesia with ketamine can alter indices of fetal myocardial function and other cardiac parameters used in fetal and neonatal monitoring, without affecting tissular oxygenation.

Characterization of systolic intervals in healthy, conscious sheep

“…In the study reported here, systolic intervals were measured noninvasively in conscious, healthy sheep. When the dependence of PEP, ET, and PEP-to-ET ratio on heart rate was taken into account, the values of these systolic intervals were in consistent agreement with other findings in fetal lambs 14 and newborn and adult sheep. 1,15,19 The proportion of the cardiac cycle that constitutes the ICT in sheep is similar to that in fetal lambs.…”

“…The myocardial tension index decreases when systolic function improves. The PEP-to-ET ratio is a commonly used means of assessing ventricular performance 2,3,[7][8][9][10][11]14,15,17,18 that decreases when systolic function improves. Reduced ventricular contractility is reflected by an increase in the PEP-to-ET ratio.…”

“…6,16 The isovolumetric contraction index and the systolic time index were computed as ICT/PEP 5,6 and ICT/ET, 5,17 respectively. The PEP-to-ET ratio, which is a commonly used index of contractility and performance of the left ventricle, 2,3,[7][8][9][10][11][12][13][14][15]17,18 was determined. The duration of cardiac output ejection was defined as a product of ET and heart rate.…”

Impact of Anesthesia on Echocardiographic Evaluation of Systolic and Diastolic Function in Rats

“…However, sedation is almost always used to perform an echocardiogram in small animals such as mice and rats. Anesthetic agents are known to affect cardiovascular hemodynamics, preload, afterload, as well as myocardial contractility ( [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Therefore the choice of anesthetic agent has the potential to significantly alter echocardiographic parameters.…”

Hyperactivity following postnatal NMDA antagonist treatment: Reversal by D-amphetamine

“…The NMDA receptor antagonist, ketamine, has been applied as an anaesthetic compound during both normal birth and Caesarean section in different species, rays (Danneman and Mandrell, 1997), monkeys (Eng et al, 1975), calves (Blaze et al, 1988) and lambs (Lafond et al, 1987). Several studies have been aimed at assessments of potential neurobehavioural deficits (e.g., Hodgkinson et al, 1977;1978a,c).…”