Articles: general-anesthesia.
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J. Auton. Nerv. Syst. · Mar 1982
Effects of ketamine and Althesin Anesthesia on baroreceptor--heart rate reflex and hemodynamics of intact and pontine rabbits.
The changes in baroreceptor-heart rate reflex properties and in hemodynamics produced by light ketamine anesthesia were studied in one group of rabbits before and after infracollicular decerebration and those produced by althesin anesthesia in another group. Ketamine produced marked depression of baroreceptor reflex-mediated vagal effects on heart rate which was of similar magnitude in intact and pontine decerebrate rabbits; this indicates that its action was largely at or below the pons. ⋯ In the intact rabbit ketamine produced a greater rise in blood pressure than Althesin anesthesia for 1 h; the greater pressor response was due to a transient rise in total peripheral resistance (TPR) and a sustained rise in cardiac output. The difference in the blood pressure responses was mainly due to differences in action of the two anesthetics at or below the pons and only the transient rise in TPR during ketamine anesthesia was mediated through a suprapontine pathway.
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To determine the effects of tidal volume (VT) and positive end-expiratory pressure (PEEP) on pulmonary oxygen exchange during endobronchial (one-lung) anesthesia, the authors studied the effects of VT at 8 and 16 per cent total lung capacity (TLC), at zero end-expiratory pressure (ZEEP), and at 10 cmH2O PEEP in 16 patients in the lateral position. Anesthesia was maintained with halothane and oxygen. During two-lung ventilation (FIO2 0.99), mean PaO2 and physiologic shunt (Qs/Qt) were 421 +/- 12 mmHg and 0.22 +/- 0.02, respectively. ⋯ At both levels of VT, PEEP reduced mean Qt by approximatley 10 per cent (P less than 0.01) and increased compliance (P less than 0.01). However, PEEP did not significantly affect mean Qs/Qt or mean arterial or pulmonary arterial pressures at either level of VT. There was considerable variation in PaO2 and Qs/Qt among patients.
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Acta Anaesthesiol Scand · Feb 1982
Cardiocirculatory effects of prolonged administration of isoflurane in normocarbic human volunteers.
Effects of the prolonged administration of isoflurane on haemodynamics were studied in 17 healthy volunteers under normocarbic conditions. The anaesthetic was administered for 90 min at a constant alveolar concentration. Cardiac index was unchanged in the presence of decrease stroke volume index and increased heart rate. ⋯ Left ventricular work decreased. The left ventricular ejection time index increased marginally but significantly. Isoflurane caused no change in the pump performance of the heart but depressed the muscle performance.