Abstract

To determine the cardiopulmonary effects and usefulness of intraosseous propofol as an anesthetic in green iguanas (Iguana iguana) following a single bolus and during constant rate infusion for 30 min.

Animals

Fourteen clinically healthy green iguanas of unknown sex and age on loan from a local zoological institution were used.

Methods

In the first trial, four iguanas were induced with propofol administered intraosseous (IO) at 10 mg/kg. Immediately following induction of anesthesia iguanas were intubated and end tidal CO₂ (EtCO₂) concentrations were monitored continuously. Heart rate, respiratory rate, and rectal body temperature were recorded 1 min prior to propofol administration, every minute for the first 5 minutes, then every 5 minutes until recovered from the anesthetic event. Functional hemoglobin oxygen saturation (SpO₂) was recorded every minute following induction for the first 5 minutes and every 5 minutes until recovery.

In a second trial ten green iguanas were administered intraosseous propofol at 5 mg/kg for induction of anesthesia. Anesthesia was maintained for 30 minutes by constant rate intraosseous infusion of propofol at 0.5 mg/kg/minutes. Iguanas were not intubated and EtCO₂ was not monitored. Heart rate, respiratory rate, rectal body temperature, and SpO₂ were recorded as in the first trial. In addition, venous blood gas tensions were determined 1 minute prior to propofol administration and at 1-, 5-, and 30-minutes post induction.

Results

In the first trial, induction time was 1.2±0.6 minutes. Baseline heart rate was 74±8 beats/minutes. A significant but transient decrease in heart rate was seen 1 minute after propofol administration (60±5 beats/minute). All iguanas were apneic following induction and spontaneous ventilation resumed within 5 minutes. A significant decrease in respiratory rate from 26±8 breaths/minute to 2±3 breaths/minute was observed 1 minute following propofol administration. This decrease persisted until 25 minutes where it was no longer different from Time 0 (T0). End-tidal CO₂ concentrations decreased from 46±7 mm Hg at 4 minutes of immobilization to 32±6 mm Hg at 30 minutes of immobilization.

In the second trial, induction time was 3±2 min following administration of 5 mg/kg propofol. No significant changes in heart rate were seen throughout the infusion period; however, at 35 minutes a significant decrease in heart rate was noted. The baseline heart rate was 59±17 beats/minute. Heart rate after 30 minutes of immobilization was 51±12 beats/minute. A significant decrease in heart rate occurred at 35 minutes and persisted until 120 minutes after the initiation of propofol administration. Apnea was observed in six iguanas between 2 and 15 minutes after the onset of propofol administration. Apnea persisted to 120 minutes in two of the six iguanas. A significant decrease in respiratory rate was observed after 2 minutes of immobilization (12±7 breaths/minute) when compared to T0 (27±13 breaths/minute). Decreased respiratory rates persisted to 105 minutes of immobilization. SpO₂ values decreased from 79±10% at 5 minutes of immobilization to 64±16% at 30 minutes. The venous pH decreased from 7.4±0.2 at 1 minute to 7.2±0.2 at 30 minutes. Recovery time was 57±27 minutes. Recoveries were smooth and excitement-free.

Conclusions

Propofol is an effective agent for induction and maintenance of anesthesia in green iguanas. Propofol administration was associated with clinically substantial changes in cardiopulmonary function. It is recommended to intubate, provide oxygen supplementation, and assist ventilation following administration of propofol to prevent hypoxemia and hypercapnia. Further studies are needed to see if a dose less than that used in this study might shorten the recovery time as well as decrease the cardiopulmonary depressant effects.

Literature Cited

1.  Bennett, R.A., J. Shumacher, K. Hedjazi-Haring, S.M. Newell. 1998. Cardiopulmonary and anesthetic effects of propofol administered intraosseously to green iguanas. JAVMA. 212 (1): 93–98.