The objective of this study was to investigate if changes in arterial blood pressure and heart rate differ depending on degree of surgical trauma. Laparoscopic ovariectomy (LOE) was compared with open ovariohysterectomy (OHE) in a non-randomized, prospective clinical trial. Eight dogs were spayed by LOE technique and eight by OHE technique. A non-invasive oscillometric method registered the heart rate and blood pressure once a minute. For comparisons the operations were divided into the four phases: zero=steady state after induction of anaesthesia but before surgical interventions, one=access to abdomen, two=removal of ovaries and, if OHE also the uterus, and three=removal of troacars and closing abdomen. In LOE-patients the systolic blood pressure increased 7 mm Hg (P = 0.05) in phase one, increased an additional 8 mm Hg (P = 0.16) during phase two, and decreased 6 mm Hg (P = 0.08) in phase three. In OHE-patients the systolic pressure increased 3 mm Hg (P = 0.35) in phase one and 26 mm Hg further (P = 0.0003) in phase two, and decreased 15 mm Hg (P = 0.0007) in phase three. Comparison between groups revealed that the blood pressure increase differed from phase one to phase two between the OHE and the LOE groups (P = 0.03). The heart rate did not differ between the two surgical techniques or the phases.

Conclusion: 

The systolic blood pressure increased more during OHE compared with LOE. This is consistent with previous studies showing that OHE induces more severe surgical trauma than LOE. Repeated measurements of blood pressure appear useful for evaluating surgical trauma, but the heart rate is not.