Age-dependent Responses to Thermal Hyperalgesia and Mechanical Allodynia in a Rat Model of Acute Postoperative Pain

Background: Developmental differences in short- and long-term responses to pain, especially surgical pain, have received minimal attention. The purpose of the present study was to examine postoperative responses in rats of developmental ages paralleling the infant to young adult human.

Methods: The withdrawal threshold to von Frey filament testing and withdrawal latency to hind-paw radiant heating were determined before and for various times after hind-paw incision in rats 2, 4, and 16 weeks of age. Control rats of these ages were observed serially without surgery.

Results: In control animals, younger rats were more sensitive to mechanical stimulation and less sensitive to thermal stimulation. Paw incision resulted in similar changes to both types of stimulation in all age groups, peaking 4 h after surgery. However, the return to normal sensitivity to mechanical stimulation, as measured by return of threshold to 80% of normal, occurred more quickly in 2-week-old than in 4- and 16-week-old animals. In contrast, there was no age difference for time to return to normal sensitivity to thermal stimulation after surgery.     

Age-dependent Responses to Nerve Injury- induced Mechanical Allodynia

Background: Developmental differences in responses to acute and chronic nerve injury have received minimal attention. This study examines developmental differences in behavioral responses to a proximal (closer to the spinal cord) (L5 and L6 spinal nerve root ligation) or to a more distal (closer to peripheral innervation) (partial sciatic nerve ligation) nerve injury in rats paralleling the infant to young adult human.

Methods: Withdrawal thresholds to von Frey filament testing in the hind paw were determined before and various times after either spinal nerve root ligation or partial sciatic nerve ligation in rats aged 2, 4, and 16 weeks. Control rats of these ages were observed serially without surgery. Times for withdrawal thresholds to mechanical stimuli to return to 80% of that of the hind paw in the control animals were compared among the different ages in the two models.

Results: Baseline withdrawal thresholds in younger rats were lower (P < 0.05). In the 2-week-old animals, distal injury partial sciatic nerve ligation did not cause a reduction in withdrawal threshold from baseline. This was different from the spinal nerve root ligation group and the older animals in the partial sciatic nerve ligation group. However, when compared with age-matched control animals, both nerve injuries resulted in reduced withdrawal thresholds (P < 0.05). The resolution of hypersensitivity to mechanical stimulation, as measured by return of threshold to 80% of controls, occurred more quickly in 2-week-old than in 4- and 16-week-old animals in both injury models (P < 0.05).     

Differential onset of median nerve block: randomized, double-blind comparison of mepivacaine and bupivacaine in healthy volunteers

We have compared the delay in onset of 1% mepivacaine and 0.33% bupivacaine in different nerve fibre types in 10 volunteers undergoing median nerve blocks, in a randomized, double-blind, crossover study. Hot, cold, pinprick and light touch sensations, compound motor action potentials (CMAP), sensory nerve action potentials (SNAP) and skin temperature were recorded at 2-min intervals. Hot, cold, pinprick, light touch sensations, SNAP and CMAP were significantly inhibited, and skin temperature was significantly increased after administration of both agents. The first noticeable reduction in cold sensation was detected later after bupivacaine compared with mepivacaine, but after a delay similar to that of other nerve functions. Bupivacaine and mepivacaine inhibited SNAP and CMAP with a similar time delay to steady- state. Bupivacaine produced steady-state inhibition of hot and cold sensations significantly later than mepivacaine; nevertheless, the sequence that sensory modalities failed, with few exceptions, and the extent of anaesthesia at 40 min were similar for both agents. Our technique provides a novel, multi-modal method of comparing local anaesthetics and related agents over time.      

The Response of Patients with Duchenne's Muscular Dystrophy to Neuromuscular Blockade with Vecuronium

Background: The authors hypothesized that patients with Duchenne's muscular dystrophy (DMD) are more sensitive to nondepolarizing muscle relaxants.

Methods: Eight children with DMD and eight healthy children having orthopedic procedures were studied. Anesthesia consisted of thiopental, 60% nitrous oxide in 40% oxygen, and intravenous fentanyl and midazolam. Using electromyography, the ulnar nerve was stimulated and the electromyographic train-of-four ratio (TOFr) of the first dorsal interosseous muscle was recorded every 60 s. After baseline TOFr recording, all patients received 50 micro gram/kg vecuronium and the TOFr at 3 min was compared. Vecuronium (10 micro gram/kg) was then administered every minute until TOFr was or= to 0.01. Then 10 micro gram/kg of vecuronium were administered to maintain TOFr Results: The initial dose of vecuronium resulted in greater TOFr depression in patients with DMD than in controls (0.14 vs. 0.86). Less vecuronium was needed to produce TOFr or= to 0.1 after the initial dose was longer in the patients with DMD than in the controls (28 vs. 20 min; P = 0.03), and the maintenance dose of vecuronium was less in patients with DMD (0.6 vs. 1.3 micro gram [center dot] kg sup -1 [center dot] min sup -1; P < 0.01). The time for TOFr recovery from 0.1 to 0.25 was 36 min in the patients with DMD and 6 min in the controls (P <0.01). After neostigmine, the TOFr was 1.0 in the controls and 0.91 (P = 0.03) in the patients with DMD.     

Transfusion-related acute lung injury in an infant during craniofacial surgery

Transfusion-related acute lung injury (TRALI) is a potentially life-threatening, systemic, immune-mediated reaction to transfused blood product. The symptoms may be masked under general anesthesia. In this case report, we describe an infant who developed TRALI under general anesthesia for craniofacial surgery. The difficulty with diagnosis, the pathophysiology, and the need for understanding and recognition to reduce morbidity and mortality are discussed. IMPLICATIONS: Transfusion-related acute lung injury (TRALI) is a life-threatening problem that can occur during blood product transfusion in patients of any age. Understanding the pathophysiology may help make an earlier diagnosis to reduce more serious adverse outcomes.     

Allogeneic hematopoietic stem cell transplantation in the active duty military population: 1987-2001

Wilford Hall Medical Center at Lackland Air Force Base is the only military medical center in the United States at which allogeneic hematopoietic stem cell transplants (HSCT) are performed. Through May 2001, 367 patients, including 163 active duty service members, have received allogeneic HSCT from related donors. We performed a retrospective review of the outcomes of allogeneic HSCT in active duty members to determine what proportion was returned to full-time military service after HSCT and to delineate the factors associated with successful return to military service. Twenty-one percent of service members who received allogeneic HSCT were returned to active duty at some point after treatment. Age, sex, branch of service, and rank had no significant influence on return to duty status. When adjusted for age and rank, the only significant predictor of successful return to active duty was a diagnosis of chronic myelogenous leukemia. Although individuals with good risk diseases such as aplastic anemia, myelodysplastic syndrome, paroxymal nocturnal hemoglobinuria, and acute myelogenous leukemia in first complete remission have also been returned active duty after HSCT, these diagnoses were not statistically predictive of a return to active duty. We conclude that it may be possible to predict which service members will return to active duty after allogeneic HSCT based on the disease for which HSCT is being performed. Most importantly, active duty service members need not be a priori medically retired after HSCT, and each return to duty decision must be individualized.     

Correlation of CD34+ cell counts with volume of bone marrow collected for allogeneic bone marrow harvests

The quantity of bone marrow collected for allogeneic bone marrow transplantation is based on collecting 10 to 15 cc of bone marrow/kg of recipient weight. We hypothesized that the percentage of CD34+ cells collected during a bone marrow harvest decreased at the end of the harvest because of increasing amounts of peripheral blood contamination. We performed a prospective, blinded study in which we measured CD34+ percentages and cell counts at 200-cc intervals during bone marrow harvests from 11 consecutive human leukocyte antigen (HLA)-matched sibling bone marrow donors. We observed that the percentage of CD34+ cells in aspirated bone marrow did not vary significantly from the start to the end of the bone marrow harvest, and the total number of CD34+ cells/kg increased in a linear fashion, thus disproving our original hypothesis. In conclusion, the percentage of CD34+ cells in aspirated bone marrow will remain constant throughout a bone marrow harvest.