postoperative cognitive dysfunction

Clinical Topic: Cerebral O2 Saturation and Cognitive Dysfunction

Postoperative cognitive dysfunction (POCD) is a common complication after major surgery with general anaesthesia in the elderly. Due to the increase of average life expectancy, an increasing number of elderly patients undergo surgery. Following surgery, elderly patients may exhibit cognitive changes.

Anesthesia researchers have speculated that single lung ventilation places an elderly patient at increased risk for reduced cerebral oxygenation and also speculate that reduced cerebral oxygenation correlates with postoperative cognitive dysfunction. Two recent studies have addressed the issues described above.

In the first study by Tang L, et al (Br J Anaesth. 2012 Apr;108(4):623-9. doi: 10.1093/bja/aer501. Epub 2012 Feb 5.) titled “Reduced cerebral oxygen saturation during thoracic surgery predicts early postoperative cognitive dysfunction.” studied seventy-six patients undergoing thoracic surgery with single-lung ventilation (SLV) of an expected duration of >45 min were enrolled. Monitoring consisted of standard clinical parameters and absolute oximetry (S(ct)O(2)). The Mini-Mental State Exam (MMSE) test was used to assess cognitive function before operation and at 3 and 24 h after operation. In this study, the authors found that postoperative cognitive dysfunction correlated with reduced cerebral oxygenation during surgery

Click here to read the abstract of the original work.

A similar study by Suehiro K. et al found similar results. The study titled “Duration of cerebral desaturation time during single-lung ventilation correlates with mini mental state examination score.” published in J Anesth. 2011 Jun;25(3):345-9. doi: 10.1007/s00540-011-1136-1. Epub 2011 Apr 12. looked at “Sixty-nine patients , each of whom received combined thoracic epidural and general anesthesia. rSO(2) was measured using INVOS 5100 (Somanetics, Troy, MI, USA) before anesthesia (baseline value) and until SLV was completed. Patient cognitive function was assessed using the mini mental state examination (MMSE) on the day before surgery (baseline) and then repeated 4 days after surgery. The patients were classified into two groups: with (desaturation group, group D) and without (nondesaturation group, group N) cerebral desaturation during SLV. Cerebral desaturation was defined as a reduction of rSO(2) during SLV less than 80% of the baseline value.” They found that the duration of cerebral desaturation correlated with postoperative cognitive dysfunction.

Click here to read the abstract of the original work

Cerebral oxymetry is becoming increasingly available and should be considered for the elderly patient scheduled for one lung ventilaion.

Clinical Topic: Bis and Postoperative Cognitive Dysfunction

As anesthetists, we pride ourselves in our vigilance and our ability to maintain hemodynamic stability during difficult surgical situations. However, for the patient, the surgical experience is just one point in time in the continuum of life. They recover, leave the hospital and continue with life. The ability of an elderly patient to participate in the activities of daily living can be impaired by postoperative cognitive dysfunction.

The risk of postoperative cognitive dysfunction in the elderly was documented by JT Moller MD et al in an article published in The Lancet (Long-term postoperative cognitive dysfunction in the elderly: ISPOCD1 study, The Lancet, Volume 351, Issue 9106, Pages 857 – 861, 21 March 1998) The authors speculated that hypotension and hypoxemia might be correlated to cognitive dysfunction and state the following findings:

Postoperative cognitive dysfunction was present in 266 (25·8% [95% CI 23·1—28·5]) of patients 1 week after surgery and in 94 (9·9% [8·1—12·0]) 3 months after surgery, compared with 3·4% and 2·8%, respectively, of UK controls (p<0·0001 and p=0·0037, respectively). Increasing age and duration of anaesthesia, little education, a second operation, postoperative infections, and respiratory complications were risk factors for early postoperative cognitive dysfunction, but only age was a risk factor for late postoperative cognitive dysfunction. Hypoxaemia and hypotension were not significant risk factors at any time.

Click here for an abstract of the original article

A study by MT Chan et al (BIS-guided Anesthesia Decreases Postoperative Delirium and Cognitive Decline, PMID:23027226 [PubMed – as supplied by publisher]) utilized the BIS monitor to guide the amount of anesthesia administered and to correlate depth of anesthesia to postoperative cognitive dysfunction. In this study the BIS group had anesthesia adjusted to maintain a BIS level between 40-60. The control group had anesthesia administered based on clinical signs.

Based on their findings, the authors concluded:

BIS-guided anesthesia reduced anesthetic exposure and decreased the risk of POCD at 3 months after surgery. For every 1000 elderly patients undergoing major surgery, anesthetic delivery titrated to a range of BIS between 40 and 60 would prevent 23 patients from POCD and 83 patients from delirium.

Click here for an abstract of the original article

The debate remains….”to BIS or not to BIS” Many providers are comfortable that the depth of anesthesia is adequate without BIS guidance, however, the BIS may be useful in preventing excessive depth of anesthesia and, therefore, reducing the incidence of postoperative cognitive dysfunction in the elderly.

What say you? Please share your thoughts with your colleagues.

The Influence of Perioperative Care and Treatment on the 4-Month Outcome in Elderly Patients With Hip Fracture

With the baby boomers coming of age, the demographics of those seeking health care is changing. The percentage of those considered “elderly” in the surgical population has had a steady increase over the past few decades. In a study published in the February 2011 edition of the AANA Journal, Bjorkelund et al discuss risk factors of anesthesia related to the elderly population.

In this study of elderly patients with hip fracture, premedication, prolonged fasting and fracture type were related to postoperative confusion and mortality at 4 month. The authors found that decreased SpO2, prolonged fasting and increased number of units transfused all impaired recovery and were correlated to a higher mortality rate. Patients with the longest fasting times tended to receive a larger volume of fluid which may have stressed physiologic reserve.

The effects of preoperative medication on outcome produced an unexpected finding. In this study, those who received no premedication had a higher rate of confusion and mortality at 4 months. The authors speculate that either the premedication reduced the stress of surgery and improved outcome or that those who were not premedicated were in a higher risk group and possibly not a candidate for sedation.

Click here to view the study published in the AANA Journal.