- Risk Factors
- Interventions that may reduce the likelihood of POVL caused by ION
- Informed Consent
POVL is assumed to be due to
- ischemic optic neuropathy (ION) or
- central retinal artery occlusion (CRAO)
- POVL from CRAO caused by globe compression should be preventable with the use of appropriate positioning aids and monitoring of the external globes (eye checks) during the intraoperative period.
High-risk patients for ION are defined as
- those undergoing spine procedures while positioned prone and
- who had prolonged procedures (exceeding an average of 6.5 hours) and who
- experienced substantial blood loss (an average of 44.7% of the estimated blood volume), or
- A similar definition with regard to operative duration is arbitrarily applied by the APSF to head-down (degree of head-down not definable) robotic/laparoscopic surgeries.
- prolonged spine surgery in the prone position, or
- prolonged robotic surgery in the head down position
- increased blood loss
- male gender
- use of Wilson surgical frame
- Use of controlled hypotension in patients at risk for POVL caused by ION, although not documented to be an independent risk factor, is not recommended on a routine basis.
- Risk is LOW (<1%), but because outcome is devastating, informed consent is IMPORTANT
- minimize duration of surgery
- consider staged spine procedures
- keep head at or above the level of the heart
- minimize use of surgical frames that place the head lower than the heart
- include colloid in nonblood replacement
- limit the amount of crystalloid fluid administration
During the informed consent process, anesthesia professionals and surgeons should include discussion of the remote risk (<1%) of visual impairment, ranging from partial vision loss to complete blindness in both eyes for patients considered to be at risk for POVL from ION.
The informed consent process may include a discussion of risk factors (see above)
and the current understanding of interventions that may reduce the likelihood of POVL caused by ION (see above)
Discussion may include the concept that this complication is difficult to study because of its low incidence. Preventive measures are based on the our best educated guess from what we know of the risk factors but have not been tested.
The APSF suggests that it is the Surgeon's Primary Responsibility to inform the patient of this remote but catastrophic complication. On the day of surgery, the Anesthesiologist should confirm that this discussion between the Surgeon and the Patient has occured. If the Surgeon has not done this, then the Anesthesiologist must include a full discussion in the Informed Consent.
POVL Video (2014) from Anesthesia Patient Safety Foundation (10 minutes): Focuses on Informed Consent
ASA Practice Advisory on POVL: Anesthesiology 2012;116:274-282