The effects of hypocapnic ventilation on mental function in elderly patients undergoing cataract surgery

Effects of intra-operative end-tidal carbon dioxide levels on the rates of post-operative complications in adults undergoing general anesthesia for percutaneous nephrolithotomy: A clinical trial

Background:

A retrospective study has shown lesser days of hospital stay in patients with increased levels of intra-operative end-tidal carbon dioxide (ETCO₂). It is probable that hypercapnia may exert its beneficial effects on patients’ outcome through optimization of global hemodynamic and tissue oxygenation, leading to a lower rate of post-operative complications. This study was designed to test the hypothesis that higher values of intra-operative ETCO₂ decrease the rate of post-operative complications.

Materials and Methods:

In this randomized, double-blind clinical trial, 78 adult patients scheduled for percutaneous nephrolithotomy (PCNL) were prospectively enrolled and randomly divided into three groups. ETCO₂ was set and maintained throughout the procedure at 31-33, 37-39 and 43-45 mmHg in the hypocapnia, normocapnia and hypercapnia groups, respectively. The rates of post-operative complications were compared among the three groups.

Results:

Seventy-five patients completed the study (52 male and 23 female). Ten (38.5%), four (16%) and two (8.3%) patients developed post-operative vomiting in the hypocapnia, normocapnia and hypercapnia groups, respectively (P = 0.025). The nausea score was significantly lower in the hypercapnic group compared with the other groups (3.9 ± 1.8, 3.2 ± 2.1 and 1.3 ± 1.8 in the hypocapnia, normocapnia and hypercapnia groups, respectively; P = 0.000). Time to return of spontaneous respiration and awakening were significantly decreased in the hypercapnia group compared with the other groups (P < 0.01).

Conclusion:

Mild intra-operative hypercapnia has a protecting effect against the development of post-operative nausea and vomiting and decreases the duration of emergence and recovery from general anesthesia.

Postoperative cognitive dysfunction in the elderly

Despite improvement in surgical techniques, anesthetic management, and intensive care, a significant number of elderly patients develop postoperative cognitive decline. Postoperative cognitive dysfunction (POCD) is a postoperative memory or thinking impairment that has been corroborated by neuropsychological testing, for which increasing age is the leading risk factor. POCD is multifactorial in origin, but it remains unclear whether its occurrence is a result of surgery or general anesthesia. This article discusses the incidence, assessment, consequences, and prevention of POCD, as well as anesthetic strategies to improve cognitive outcome in elderly patients.

Evidence-based clinical update: general anesthesia and the risk of delirium and postoperative cognitive dysfunction

PURPOSE

The purpose of this structured, evidence-based, clinical update was to identify the best evidence comparing general and regional anesthesia and their influence on delirium or cognitive dysfunction (POCD) in the postoperative period.

SOURCE

In June 2005 a structured search of MEDLINE from 1966 to present using OVID software was undertaken. Medical subject headings and textwords describing both delirium and POCD were employed. OVID's Therapy (sensitivity) algorithm was used to maximize the detection of randomized trials. The bibliographies of eligible publications were hand-searched to identify trials not identified in the electronic search. Publications enrolling children were excluded. Levels of evidence and grades of recommendations were scored using Centre for Evidence Based Medicine criteria.

PRINCIPAL FINDINGS

A total of 18 unique randomized controlled trials were identified: two evaluating delirium; ten evaluating POCD; and six evaluating both. Outcomes for delirium were abstracted from eight trials that enrolled 765 patients (387 regional anesthesia; 378 general anesthesia). Outcomes for POCD were identified from 16 trials that enrolled 2,708 patients (1,313 regional anesthesia; 1,395 general anesthesia). Both delirium (11-43%) and POCD (15-25%) were relatively common in trials actively seeking these outcomes. Consistent Level 2b evidence suggests no significant increase in delirium in patients receiving general anesthesia compared with those receiving regional anesthesia. Similarly, consistent Level 1 evidence indicates that exposure to general anesthesia is not significantly associated with POCD.

CONCLUSION

Available randomized controlled trials suggest that there is no significant difference in the incidence of delirium or POCD when general anesthesia and regional anesthesia are compared.

Postoperative cognitive dysfunction versus complaints: a discrepancy in long-term findings

This review describes the discrepancy in findings between postoperative cognitive performance and postoperative cognitive complaints long time after an operation under general anesthesia. Shortly (from 6 hr to 1 week) after an operation a decline in cognitive performance is reported in most studies. However, long time (from 3 weeks to 1-2 years) after an operation this is rarely found although some patients are still reporting cognitive complaints. In general this kind of research is suffering from severe methodological problems (use of insensitive tests, lack of control groups, lack of parallel tests, different definitions of cognitive decline). However, these problems cannot totally explain the discrepancy in findings in the long term. Thus, there are patients who have persistent cognitive complaints long time after an operation, that cannot be measured with cognitive tests. More psychological factors such as fixation on short-term cognitive dysfunction, mood, coping style, and personality are possible explanations for these cognitive complaints in the long term. As a consequence, these factors should be a topic in future research elucidating the persistence of these cognitive complaints long time after an operation under general anesthesia.