Information available on the internet regarding anesthesia in dogs is generally not complete and may be misleading with respect to risks to specific breeds. Consequently, veterinarians should appropriately educate clients regarding anesthetic risk to their particular dog.
The significant reduction in MAC of isoflurane supported the practice of the addition of regional anesthesia for painful dental procedures to reduce the dose-dependent cardiorespiratory effects of general anesthesia.
Objective
To investigate changes in colloid osmotic pressure (COP), total protein (TP) and osmolality (OSM) during anesthesia in horses given intravenous lactated Ringer’s solution (LRS) or LRS and hetastarch (HES).
Study design
Prospective, clinical trial.
Animals
Fourteen horses presented for surgery. Mean age 8.3 ± 1.9 years; mean weight 452 ± 25 kg.
Methods
Horses were premedicated with xylazine intravenously (IV); anesthesia was induced with ketamine and diazepam IV, and maintained with sevoflurane. Butorphanol was administered IV with pre-medications or immediately after induction. Xylazine was administered IV for recovery if necessary. LRS was administered IV to all horses with a target rate of 5–10 mL kg−1 hour−1. Half of the horses also received 6% HES, 2.5 mL kg−1 over 1 hour in addition to LRS. Horses that received LRS only were considered the LRS group. Horses that received both LRS and HES were considered the LRS/HES group. Blood was drawn pre- and post-anesthesia, immediately following induction, and every 30 minutes throughout anesthesia. COP, TP and OSM were measured.
Results
COP and TP significantly decreased at similar rates for both treatment groups from pre-anesthetic values. Pre-anesthetic COP was significantly greater in the LRS group when compared to the LRS/HES group pre-, post- and throughout anesthesia. In the LRS group post-anesthetic OSM was significantly different than the pre-anesthesia value and that for the LRS/HES group.
Conclusions and clinical relevance
Administration of IV HES (2.5 mL kg−1, over 1 hour) in combination with LRS does not attenuate the decrease in COP typically seen during anesthesia with crystalloid administration alone. Based on these results, administration of HES at this rate and total volume would not be expected to prevent fluid shifts into the interstitium through its effects on COP.
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