Effects of a single dose of ketamine on duodenal motility activity in pigs

Abstract

In order to investigate the effects of a single dose of ketamine on duodenal motility, the present study focused on the electric impedance technique. Five pigs (32 to 40 kg, CVC group) were instrumented with a central venous catheter 1 d before measurements. The next day, general anesthesia was started and maintained via central venous catheter by propofol and fentanyl. In contrast, the pigs of the KETA group (n = 5) received ketamine intramuscularly prior to the induction of anesthesia by the injection of propofol-fentanyl via an ear vein. An intraluminal impedance catheter was manually introduced into the proximal duodenum. Measurements were recorded for 4 h. The KETA group showed a median duration of phase II that was shortened by 35%, while phase I was prolonged by 73% (P < 0.05). In conclusion, when gastrointestinal motility has to be investigated, the effects of a single dose of ketamine, even for premedication, should be taken into consideration.

Figure 1

Cylinder shaped metallic electrodes are mounted on a thin plastic catheter. Each neighbouring electrode pair is connected to an impedance voltage transducer outside the body (Zn = measured impedance at the moment, which is the ratio between the applied voltage [Un] and the resulting current). The instantaneous output voltage of each transducer represents the average electrical impedance of the volume conductor around the catheter. Estimation of the impedance changes caused by a bolus (Bolus) and an air volume in front of it which move distally with a velocity (V) in the reverse x-direction. (a) Illustration of a bolus shape at the moment (tn). (b) Temporal impedance changes between two neighbouring electrodes which give a characteristic shape of the impedance phases I to V. (c) Spatial impedance distribution of the impedance in the measured segment along the catheter at the time tn.

Figure 3

The duration of the different interdigestive phases of both groups. Data are shown as box blots indicating median, 25% and 75% quartiles, and range. Significance was defined as P < 0.05.

Figure 2

Duodenal impedance tracings of ketamine treated pig demonstrating 16 pairs of electrodes (Ch 1 = proximal channel 1, Ch 16 = distal channel 16). Top: time period of 8 h containing interdigestive phases. Middle: time period expanded. p1 = phase I, p2 = phase II, p3 = phase III. Bottom: phase II further expanded demonstrating bolus transport events (BTE).