Flushing induction chambers used for rodent anesthesia to reduce waste anesthetic gas

Anesthetic Effects of Intramuscular Alfaxalone-Ketamine in Naked Mole Rats (Heterocephalus glaber)

In this study, adult intact male and female (n = 10) naked mole rats (Heterocephalus glaber) were anesthetized by using a combination of ketamine (20 mg/kg IM), and alfaxalone (4.0 mg/kg IM). Induction and recovery times were recorded. Vital parameters, including heart rate, respiratory rate, and reflexes, were monitored every 5 min during the anesthetic period. Anesthetic induction was smooth and rapid. Induction time was significantly longer in male rats (median, 325 s; range, 180 to 385 s) than in females (median, 145 s; range, 118 to 180 s). In addition, overall duration of loss of righting reflex was shorter in male mole rats (median, 50 min; range, 36 to 65 min) than females (median, 70 min; range, 60 to 85 min). Males largely had intact withdrawal reflexes, whereas females showed variable loss of both forelimb and hindlimb withdrawal reflexes. Neither recovery time (mean ± 1 SD, 16 ± 13 min) nor vital parameters differed between sexes. None of animals showed any anesthesia-related adverse responses. According to these findings, intramuscular AK is a safe and effective protocol that provides brief, light anesthesia in male naked mole rats and deeper anesthesia in females. We recommend adding analgesics when this AK protocol is used for pain-inducing or invasive procedures, and further studies evaluating higher doses and different combinations are indicated.

Use of an Integrated Low-Flow Anesthetic Vaporizer, Ventilator, and Physiological Monitoring System for Rodents

Low-flow digital vaporizers commonly utilize a syringe pump to directly administer volatile anesthetics into a stream of carrier gas. Per animal welfare recommendations, animals are warmed and monitored during procedures requiring anesthesia. Common anesthesia and physiological monitoring equipment include gas tanks, anesthetic vaporizers and stands, warming controllers and pads, mechanical ventilators, and pulse oximeters. A computer is also necessary for data collection and to run equipment software. In smaller spaces or when performing field work, it can be challenging to configure all this equipment in limited space. The goal of this protocol is to demonstrate best practices for use of a low-flow digital vaporizer using both compressed oxygen and room air, along with an integrated mechanical ventilator, pulse oximeter, and far infrared warming as an all-inclusive anesthesia and physiological monitoring suite ideal for rodents.

Anesthetic Effects of Alfaxalone-Ketamine, Alfaxalone-Ketamine-Dexmedetomidine, and Alfaxalone-Butorphanol-Midazolam Administered Intramuscularly in Five striped Palm Squirrels ( Funambulus pennantii)

Injectable anesthesia protocols for five striped palm squirrels (Funambulus pennantii) are poorly described in the literature. In this study, male intact squirrels received intramuscular injections of either alfaxalone (6 mg/kg) and ketamine (40 mg/ kg; AK group, n = 8); alfaxalone (6 mg/kg), ketamine (20 mg/kg), and dexmedetomidine (0.1 mg/kg; AKD group, n = 8); or alfaxalone (8 mg/kg), butorphanol (1 mg/kg), and midazolam (1 mg/kg; ABM group, n = 8). Atipamezole (0.15 mg/kg IM) and flumazenil (0.1 mg/kg IM) were administered 40 min after anesthesia induction (defined as loss of the righting reflex) with AKD and ABM, respectively. Heart rate, respiratory rate, rectal temperature, and reflexes were recorded every 5 min during anesthesia. Anesthetic induction was rapid in all groups (AK: median, 49 s; range, 33 to 60 s; AKD, 60 s; 54 to 70 s; and ABM, 15 s; 5 to 58 s). The anesthetic duration (from induction to full recovery) for the AK group was 62 ± 3 min (mean ± 1 SD). There was no statistically significant difference between the ABM and AKD groups regarding recovery time after partial antagonist administration and was 51 ± 5 and 48 ± 5 min, respectively. All AK animals showed twitching and abnormal vocalization during recovery. The righting reflex was absent in all squirrels for 20 min in the AK treatment group and throughout the 40 min anesthetic period in the AKD and ABM groups. The frontlimb withdrawal response was absent in all squirrels for the 40 min anesthetic period in the AKD and ABM groups, with variable responses for the AK treatment. All tested protocols in this study provided safe and effective immobilization in five striped palm squirrels, but oxygen and thermal support were indicated. Anesthetic depth must be determined before surgical procedures are performed in palm squirrels anesthetized by using these regimens.

Anesthetic effects of dexmedetomidine-ketamine-midazolam administered intramuscularly in five-striped palm squirrels (Funambulus pennantii)

OBJECTIVE

To evaluate efficacy and safety of anesthesia with dexmedetomidine-ketamine-midazolam (DKM) in five-striped palm squirrels (Funambulus pennantii).

ANIMALS

8 male squirrels.

PROCEDURES

Squirrels were anesthetized with DKM (dexmedetomidine, 0.1 mg/kg; ketamine hydrochloride, 30 mg/kg; and midazolam, 0.75 mg/kg) administered IM. Atipamezole (0.15 mg/kg) and flumazenil (0.1 mg/kg) were administered IM 40 minutes after induction of anesthesia. Vital signs and responses were recorded every 5 minutes during anesthesia.

RESULTS

Anesthetic induction and recovery from anesthesia were rapid and without complications in all squirrels. Median anesthetic induction time was 67.5 seconds (interquartile [25th to 75th percentile] range, 5.5 seconds), and mean ± SD recovery time after drug reversal was 147 ± 79 seconds. Heart rate, respiratory rate, and rectal temperature significantly decreased during the anesthetic period. All squirrels became hypothermic by 40 minutes after induction. The righting reflex was absent during the 40-minute anesthetic period in all squirrels, with variable responses for the palpebral reflex, jaw tone, forelimb withdrawal reflex, and hind limb withdrawal reflex. Only 2 of 8 squirrels had loss of the limb withdrawal reflex in both the forelimbs and hind limbs from anesthetic induction to 25 minutes after induction.

CONCLUSIONS AND CLINICAL RELEVANCE

DKM appeared to provide safe and effective anesthesia in five-striped palm squirrels, but oxygen and thermal support were indicated. At the doses administered, deep surgical anesthesia was not consistently achieved, and anesthetic depth of individual squirrels must be determined before surgical procedures are performed in palm squirrels anesthetized with this drug combination.

Evaluation of waste anesthetic gas surveillance program and isoflurane exposures during animal and human surgery

Prolonged occupational exposure to waste anesthetic gases may have the potential to cause adverse health effects. Workplace exposure surveillance programs are intended to reduce health risk by evaluating exposures to waste anesthetic gases during surgical procedures. Both the personal breathing-zone and area measurements are used to assess occupational exposure in the operating theater. Direct-reading instruments provide real-time measurements and are useful for identifying leaks and evaluating on-the-spot corrective actions. Passive diffusion monitors quantify occupational exposures over time during surgery. The aim of this study was to evaluate a waste anesthetic gas surveillance program to understand occupational exposures and further improve data collection strategy. For this study, 76 survey reports from 2012 through 2014 were retrospectively reviewed to assess occupational exposures to isoflurane in 58 unique procedural rooms operated by the National Institutes of Health. The surveys included industrial hygiene assessments performed during animal and human surgical procedures. The survey reports were evaluated qualitatively and data from these reports was transcribed for quantitative analysis. Variations in sample strategy were observed between surveys and were attributed to ambiguity in the written surveillance program. The study also evaluated the relationship between isoflurane concentrations and sampling method, sampling location, patient type, or scavenging method. Isoflurane exposures were significantly higher among procedures performed on rodents compared to the patients with a large body mass (humans, non-human primates, and swine) (P < 0.05) and in procedures using the charcoal canister exhaust system compared with the central vacuum exhaust system. In addition, individuals performing the surgical procedure experienced elevated occupational exposures measured by both direct-reading instrument and passive diffusion monitors, that is, exposure was significantly higher as measured at the breathing-zone compared with any area within the room (P < 0.05). The study identified several inconsistencies and shortcomings in the surveillance program. Isoflurane concentrations measured during rodent procedures requires further review of work practices and engineering controls. Overall, the findings provide insights to further improve data collection, monitoring, and control of isoflurane exposures.

Comparison of Dexmedetomidine-Ketamine-Midazolam and Isoflurane for Anesthesia of Black-tailed Prairie Dogs (Cynomys ludovicianus)

Few studies evaluate anesthesia in black-tailed prairie dogs (Cynomys ludovicianus). Isoflurane inhalant anesthesia is used in this species most commonly, but injectable protocols are poorly described. Here we compared the physiologic effects, including anesthetic depth, vital signs, and hematologic changes, of anesthetic protocols using isoflurane or a combination of dexmedetomidine, ketamine, and midazolam in black-tailed prairie dogs. In a randomized, complete crossover study design, intact male black-tailed prairie dogs (n = 9; age, 6 mo) were anesthetized by using a combination of dexmedetomidine (0.25 mg/kg IM), ketamine (40 mg/kg IM), and midazolam (1.5 mg/kg IM). For reversal, atipamezole (0.15 mg/kg) and flumazenil (0.05 mg/kg) were administered 45 min after induction. For comparison, isoflurane was administered at 5% in 100% oxygen at 5 L/min in an anesthetic induction chamber, followed by maintenance isoflurane 2% in 2 L/min oxygen through a tight-fitting facemask for 45 min. Induction and recovery time, respiratory rate, heart rate, body temperature, SpO₂, indirect blood pressure, and reflexes were monitored every 5 min during the anesthetic period. Blood samples for venous blood gases, PCV, and refractometric total protein were obtained from the cranial vena cava at 5 min and 45 min. Both protocols appeared to achieve safe and effective anesthesia. Except for blood pressure, all vital signs differed between the 2 treatments. Isoflurane anesthesia resulted in a slightly longer induction and lower respiratory rate and body temperature but increased likelihood of absent reflexes. DKM anesthesia resulted in a faster induction and less hypothermia but also prolonged recovery and lower heart rate and SpO₂ readings. These findings suggest that isoflurane provides a more stable and consistent anesthetic plane, whereas dexmedetomidine-ketamine-midazolam anesthesia may be an effective alternative for short procedures that require fast induction and limited analgesia.