Do we need preemptive analgesia for the treatment of postoperative pain?

Preemptive analgesia means that an analgesic intervention is started before the noxious stimulus arises in order to block peripheral and central nociception. This afferent blockade of nociceptive impulses is maintained throughout the intra-operative and post-operative period. The goals of preemptive analgesia are, first, to decrease acute pain after tissue injury, second, to prevent pain-related pathologic modulation of the central nervous system, and third, to inhibit the persistence of postoperative pain and the development of chronic pain. So far, the promising results from animal models have not been translated into clinical practice. Therefore, clinicians should rely on conventional anaesthetic and analgesic methods with proven efficacy, i.e. a multimodal approach including the combination of strong opioids, non-opioid analgesics, and peripheral or neuraxial local anaesthetics that act at different sites of the pain pathways.     

Why do preemptive kidney transplant recipients have an allograft survival advantage?

BACKGROUND: Preemptive kidney transplantation is associated with an allograft survival advantage and is promoted in part because of this association. The basis for the allograft survival advantage in preemptive recipients is unclear. Possibilities include a lead time bias due to the earlier transplantation of patients with preserved native kidney function, less rapid loss of kidney function after transplantation, or the longer patient survival of preemptive recipients. METHODS: We compared the glomerular filtration rate (GFR) six months after transplantation and the subsequent rate of loss of kidney function as defined by the annualized change in GFR (mL/min/1.73 m2/year) in 5,966 preemptive and 34,997 non-preemptive recipients. Linear regression methods were applied to serial GFR estimates after transplantation to determine the annualized change in GFR. Multiple regression was used to determine the independent effect of preemptive transplantation upon the annualized change in GFR. RESULTS: The mean GFR six months after transplantation was similar among preemptive (49.5+/-15.7 mL/min/1.73 m2) and non-preemptive (49.2+/-14.7 mL/min/1.73 m2) recipients (P=0.37). In multivariate analysis, preemptive recipients had a slower decline in GFR (0.28 mL/min/year/1.73 m2; 95% confidence interval 0.11, 0.46; P=0.002). However, this difference was of modest clinical significance and would not explain the allograft survival advantage of preemptive transplantation. CONCLUSIONS: Neither the preservation of native kidney function nor differences in the rate of loss of kidney function explain the superior allograft survival of preemptive recipients. By exclusion, the allograft survival advantage associated with preemptive transplantation may be due to the longer survival of preemptive recipients.     

Does ketamine have preemptive effects in women undergoing abdominal hysterectomy procedures?

Ketamine may produce "preemptive" analgesia when administered before surgically induced trauma. Therefore, we hypothesized that pre- versus postincisional administration of ketamine would improve pain control after abdominal hysterectomy procedures. Eighty-nine patients were randomly assigned to one of three treatment groups according to a placebo-controlled, double-blinded protocol: Group 1 (placebo) received saline 0.04 mL/kg IV immediately before and after surgery; Group 2 (preincision), received ketamine 0.4 mg/kg IV before skin incision and saline at the end of the operation; and Group 3 (postincision), received saline before skin incision, and ketamine 0.4 mg/kg IV was given after skin closure. The general anesthetic technique was standardized in all three treatment groups. During the first postoperative hour, Group 3 experienced significantly less pain than Groups 1 and 2, as assessed by using both visual analog and verbal rating scales. There were no significant differences between Groups 1 and 2 with respect to pain scores, postoperative opioid analgesic requirements, and incidence of postoperative nausea and vomiting. We conclude that a single dose of ketamine 0.4 mg/kg IV fails to produce preemptive analgesic effects. Implications: Even though ketamine 0.4 mg/kg IV has short-lasting acute analgesic effects, it failed to produce a preemptive effect when given before abdominal hysterectomy procedures.     

Does preemptive stellate ganglion blockage increase the patency of radiocephalic arteriovenous fistula?

OBJECTIVE: Radio-cephalic arteriovenous fistulas (AVFs) have high early failure ratio. Increased sympathetic activity and spasm of radial artery during the surgery may responsible for early occlusion rate. DESIGN: Fifty patients were randomized to two groups (each containing 25 patients). Stellate Ganglion Blockade (SGB) was performed in Group 1. Another group was considered as control group (Group 2) to make statistical comparisons. All AVFs were performed under local anesthesia in both groups. RESULTS: Average fistula flow was 201.4+/-40.4 ml/min in Group 1 and 155.6+/-27.4 ml/min in Group 2 (p < 0.001). While average peak velocity of radial artery was 167.1+/-31.3 cm/sec in Group 1, it was 107.8+/-15.8 cm/sec in Group 2 (p < 0.001). Thrill was found in all Group 1 patients, but there was thrill only 13 of the Group 2 patients (p < 0.001). Mean maturation time was 41.4+/-6.8 days after surgery in Group 1 and 77.1+/-10.5 days in Group 2 (p < 0.001). Adequate vascular access was obtained 19 patients in Group 1 and 12 patients in Group 2 (p = 0.041). CONCLUSION: AVF occlusion rate is much more common in early postoperative period. Diminished sympathetic tonus by preemptive SGB not only increases early patency rate but also increases fistula maturation rate.     

A cost too high to bear? Prophylaxis versus preemptive therapy to prevent post-transplantation cytomegalovirus

Both prophylaxis and preemptive therapy are used to prevent the development of cytomegalovirus (CMV) disease after transplantation. Preemptive therapy exposes the least number of patients to costly and potentially toxic drugs. Prophylaxis is less labor intensive and requires less expensive monitoring. While the overall cost of the two modalities is similar, current literature suggests that prophylaxis has an advantage in avoiding secondary effects of CMV. Randomized comparative trials are imperative.     

Does a preemptive block of the great auricular nerve improve postoperative analgesia in children undergoing tympanomastoid surgery?

We performed a double-blinded randomized controlled trial to evaluate the efficacy of preemptive analgesia in children undergoing tympanomastoid surgery. Children were divided into two groups: group block-block (BB) received a preemptive great auricular nerve block (GAN-block) with 0.25% bupivacaine with 1:200,000 epinephrine before incision followed by a second GAN-block with 0.25% bupivacaine with 1:200,000 epinephrine 1 h before the end of the procedure. Group sham block-block (SB-B) received a preemptive GAN-block with normal saline before surgical incision followed by a GAN-block with 0.25% bupivacaine with 1:200000 epinephrine 1 h before the completion of the procedure. All patients were evaluated for pain with the objective pain score (OPS) by a blinded observer. There was no difference in pain rescue requirements in the postanesthesia care unit (BB versus SB-B, 1 of 20 versus 3 of 20, P= 0.60) or in the short-stay unit (BB versus SB-B, 5 of 20 versus 11 of 20, P = 0.107) or for the entire hospital stay (P = 0.20). There was no significant difference between groups in the time to first rescue pain medication (BB versus SB-B, 226 +/- 71 min versus 201 +/- 94 min). There was no significant difference between groups regarding vomiting in the postoperative period (P = 0.52). We conclude that a preoperative GAN-block does not offer significant advantages for postoperative pain relief in children undergoing tympanomastoid surgery. IMPLICATIONS: This double-blinded randomized controlled trial compared the efficacy of preemptive analgesia with a peripheral nerve block of the great auricular nerve for decreasing postoperative pain in children undergoing tympanomastoid surgery. Preemptive analgesia did not improve the quality or duration of postoperative analgesia in our cohort.     

Preoperative sciatic nerve block decreases mechanical allodynia more in young rats: is preemptive analgesia developmentally modulated?

Postoperative sensitivity to tactile stimuli differs as a function of age. In this study, we hypothesized that preoperative sciatic nerve block (SNB), by providing preemptive analgesia, would result in better analgesia than postoperative SNB in the young rat. With the paw incision model of postoperative pain, male Sprague-Dawley rats, aged 2 or 4 wk, underwent general anesthesia and then received a left SNB with 5 microL/g of 0.5% bupivacaine or normal saline. SNB was performed either before or after surgery. Mechanical allodynia was assessed by using von Frey filaments before and at various times after SNB and surgery. In the 2-wk-old rats, preoperative SNB produced a significant reduction in mechanical allodynia, as reflected by a higher threshold at 2, 5, and 24 h when compared with saline control (P < 0.03). At 24 h, the threshold was 4.0 +/- 0.7 g in the preoperative SNB group compared with 1.6 +/- 0.3 g in the postoperative SNB group (P = 0.004). There was no difference at any time point between the preoperative and the postoperative SNB in the 4-wk-old animals. These results suggest that preoperative SNB in young animals provides a preemptive analgesic effect on mechanical allodynia that is age or developmentally dependent.