Silbert BS et al, 2014: Incidence of postoperative cognitive dysfunction after general or spinal anaesthesia for extracorporeal shock wave lithotripsy.
Silbert BS, Evered LA, Scott DA
Centre for Anaesthesia and Cognitive Function, Department of Anaesthesia, St Vincent's Hospital, Melbourne, PO Box 2900, Fitzroy, VIC 3065, Australia Anaesthesia, Perioperative and Pain Medicine Unit, Melbourne Medical School, University of Melbourne, Australia
BACKGROUND: Since general anaesthesia invariably accompanies surgery, the contribution of each to the development of
postoperative cognitive dysfunction (POCD) has been difficult to identify. METHODS: A prospective randomized controlled trial was undertaken in elderly patients undergoing extracorporeal shock wave lithotripsy (ESWL). Between 2005 and 2011, 2706 individuals were screened to recruit 100 eligible patients. Patients were randomly assigned to receive general or spinal anaesthesia alone. A battery of eight neuropsychological tests was administered before operation and at 7 days and 3 months after operation. The reliable change index was used to calculate the incidence of POCD. Intention-to-treat analysis was used to compare rates of POCD.RESULTS: Futility analysis led to
stopping of the trial after recruitment of 100 patients. Fifty patients were randomly assigned to general anaesthesia, and 48 patients to spinal anaesthesia without sedation or postoperative opioids. At 3 months, POCD was detected in 6.8% [95% confidence interval (CI): 1.4-18.7%] of patients in the general anaesthesia group and 19.6% (95% CI: 9.4-33.9%) in the spinal group (P=0.07). At 7 days after operation, the incidence of POCD was 4.1% (95% CI: 0.5-14%) in the general anaesthesia group and 11.9% (95% CI: 4.0-26.6%) in the spinal group (P=0.16).CONCLUSIONS: We found no significant difference in the rates of POCD when comparing general anaesthesia with spinal anaesthesia, suggesting that the surgical or procedural process itself may contribute to the development of POCD.
Br J Anaesth. 2014 Jun 27. pii: aeu163. [Epub ahead of print]
A lot of work has been published that tried to show important side effects and complications of ESWL. Here is a well done study with an unusual conclusion: ESWL may cause postoperative cognitive dysfunction. But the frequently met problem to differentiate between statistical or causal relations also applies to this publication:
A non-treatment control group was taken from another study. “Patients with hip osteoarthritis typically requiring analgesics, and thus provided a suitable control group for study patients with renal stones who also often needed analgesics.” (Why not stone patients?)
“The control individuals had a higher IQ than the 98 study patients (adjusted P incidence of POCD at 3 months of 13.6% is consistent with other studies of major non-cardiac surgery. The results are consistent with recent data which indicate that POCD at 3 months occurs after other non-invasive interventions such as cardiac angiography at rates indistinguishable from total hip joint replacements or cardiac surgery.”
This is a good publication for those readers interested in postoperative cognitive dysfunction.