Postoperative pain facilitates nonthermoregulatory tremor.
BACKGROUND
Spontaneous tremor is relatively common in normothermic patients after operation and has been attributed to many causes. The hypothesis that nonthermoregulatory shivering-like tremor is facilitated by postoperative pain was tested. In addition, the effects of intravenous lidocaine on nonthermoregulatory tremor were evaluated.


METHODS
Patients undergoing knee surgery were anesthetized with 2 microg/kg intravenous fentanyl and 0.2 mg/kg etomidate. Anesthesia was maintained with 1.7 +/- 0.8% (mean +/- SD) isoflurane. Intraoperative forced-air heating maintained normothermia The initial 44 patients were randomly allocated to receive an intra-articular injection of 20 ml saline (n = 23) or lidocaine, 1.5% (n = 21). The subsequent 30 patients were randomly allocated to receive an intravenous bolus of 250 microg/kg lidocaine followed by an infusion of 13 microg x kg(-1) x h(-1) lidocaine or an equivalent volume of saline when shivering was observed. Patient-controlled analgesia was provided for all patients: 3.5 mg piritramide, with a lockout interval of 5 min, for an unlimited total dose. Shivering was graded by a blinded investigator using a four-point scale. Pain was assessed by a 100-mm visual analog scale (0 = no pain and 100 = worst pain). The arteriovenous shunt status was evaluated with forearm-minus-fingertip skin-temperature gradients.


RESULTS
Morphometric characteristics and hemodynamic responses were similar in the four groups. Core and mean skin temperature remained constant or increased slightly compared with preoperative values, and postoperative skin-temperature gradients were negative (indicating vasodilation) in nearly all patients. After intra-articular injection of saline, pain scores for the first postoperative hour averaged 46 +/- 32 mm (mean +/- SD), and 10 of the 23 (43%) patients shivered. In contrast, the pain scores of patients who received intra-articular lidocaine were significantly reduced to 5 +/- 9 mm and shivering was absent in this group (P < 0.05). In the second portion of the study, neither intravenous lidocaine nor saline reduced the magnitude or duration of nonthermoregulatory tremor or the patients' pain scores.


CONCLUSIONS
Intra-articular, but not intravenous, lidocaine reduced surgical pain and prevented nonthermoregulatory shivering. Therefore, these data indicate that postoperative pain facilitates nonthermoregulatory shivering.
Horn
E P
EP
Outcomes Research Group, Department of Anesthesiology, University Hospital Eppendorf, Hamburg, Germany. EPHORN@compuserve.com
Schroeder
F
F
Wilhelm
S
S
Sessler
D I
DI
Standl
T
T
von dem Busche
K
K
Schulte am Esch
J
J
D000328:Adult; D000368:Aged; D000768:Anesthesia, General / Q000009:adverse effects / Q000379:methods; D000779:Anesthetics, Local / Q000008:administration & dosage; D001833:Body Temperature Regulation / Q000187:drug effects; D005260:Female; D006801:Humans; D007270:Injections, Intra-Articular; D007275:Injections, Intravenous; D008012:Lidocaine / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D010149:Postoperative Pain / Q000150:complications* / Q000188:drug therapy; D014202:Tremor / Q000503:physiopathology* / Q000517:prevention & control
D000779:Anesthetics, Local; D008012:Lidocaine