The addition of lidocaine to bupivacaine does not shorten the duration of spinal anesthesia: a randomized, double-blinded study of patients undergoing knee arthroscopy.

BACKGROUND: The duration of spinal anesthesia with bupivacaine is often too long for day surgery. A recent study of patients presenting for transurethral surgery suggested that the addition of a small amount of lidocaine to intrathecal hyperbaric bupivacaine could shorten the duration of the sensory and motor blocks. In this prospective, randomized double-blind study we investigated these findings in patients undergoing unilateral knee arthroscopy. METHODS: Fifty patients were randomized to receive 2 mL hyperbaric 0.5% bupivacaine plus either 0.6 mL 1% lidocaine (lidocaine group) or 0.6 mL saline (control group). The sensory and motor blocks were monitored until complete regression and the patient was ready for discharge. The patients were interviewed 2 and 7 days after the operation about any side effects and any signs of transient neurologic syndrome. RESULTS: Data on 45 patients were available for analysis (24 in the lidocaine group). There was no statistically significant difference between the groups regarding time to readiness for surgery, maximum level of sensory block, total duration of sensory, and motor blocks or time to discharge from the postoperative care unit. Two patients in the control group and 1 patient in the study group had symptoms of transient neurologic syndrome for <24 hours after the operation. One patient had voiding difficulties for 3 days. All symptoms resolved spontaneously. No patient had spinal headache or backache. CONCLUSION: We did not confirm, in patients undergoing knee arthroscopy, that the addition of a small dose of lidocaine to intrathecal hyperbaric bupivacaine could shorten the duration of sensory or motor blocks or time to readiness for discharge from the postanesthesia care unit.

Treatment with epinephrine (adrenaline) in suspected anaphylaxis during anesthesia in Denmark.

BACKGROUND: Literature on the use of epinephrine in the treatment of anaphylaxis during anesthesia is very limited. The objective of this study was to investigate how often epinephrine is used in the treatment of suspected anaphylaxis during anesthesia in Denmark and whether timing of treatment is important. METHODS: A retrospective study of 270 patients investigated at the Danish Anaesthesia Allergy Centre after referral due to suspected anaphylaxis during anesthesia was performed. Reactions had been graded by severity: C1, mild reactions; C2, moderate reactions; C3, anaphylactic shock with circulatory instability; C4, cardiac arrest. Use of epinephrine, dosage, route of administration, and time between onset of circulatory instability and epinephrine administration were noted. RESULTS: A total of 122 (45.2%) of referred patients had C3 or C4 reactions; of those, 101 (82.8%) received epinephrine. Route of administration was intravenous in 95 (94%) patients. Median time from onset of reported hypotension to treatment with epinephrine was 10 min (range, 1-70 min). Defining epinephrine treatment less than or equal to 10 min after onset of hypotension as early, and more than 10 min as late, infusion was needed in 12 of 60 patients (20%) treated early versus 12 of 35 patients (34%) treated late (odds ratio, 2.09) (95% confidence interval, 0.81-5.35). CONCLUSION: Anaphylaxis may be difficult to diagnose during anesthesia, and treatment with epinephrine can be delayed as a consequence. Anaphylaxis should be considered and treated in patients with circulatory instability during anesthesia of no apparent cause who do not respond to the usual treatments.

Effect of general anesthesia and orthopedic surgery on serum tryptase.

BACKGROUND: Mast cell tryptase is used clinically in the evaluation of anaphylaxis during anesthesia, because symptoms and signs of anaphylaxis are often masked by the effect of anesthesia. No larger studies have examined whether surgery and anesthesia affect serum tryptase. The aim of this study was to investigate the effect of anesthesia and surgery on serum tryptase in the absence of anaphylaxis. METHODS: The study included 120 patients (median age, 54 yr; range, 19-94 yr) undergoing elective orthopedic surgery in general anesthesia. Exclusion criteria were allergic reactions during this or previous anesthesia, hematologic disease, or high-dose corticosteroid treatment. Blood samples for tryptase analysis (ImmunoCAP; Phadia, Uppsala, Sweden) were drawn shortly before anesthesia and after anesthesia and surgery. RESULTS: Median duration of anesthesia was 105 min (range, 44-263 min). Median interval between blood samples was 139 min (range, 39-370 min). Mean tryptase before surgery was 5.01 microg/l, with a mean decrease of 0.55 microg/l (P < 0.0001; 95% CI, 0.3-0.8) postoperatively. All patients received intravenous fluid (median value 750 ml; range, 200-2000 ml) perioperatively. There was no significant effect of gender, age, American Society of Anesthesiologist's physical status classification, or self-reported allergy on serum tryptase. CONCLUSIONS: Serum tryptase shows small intraindividual variation in the absence of anaphylaxis. A small decrease was observed postoperatively, likely due to dilution by intravenous fluid. On suspected anaphylaxis during anesthesia, tryptase values, even within the normal reference interval, should, when possible, be compared with the patient's own basal level taken more than 24 h after the reaction.

IgE-mediated allergy to chlorhexidine.

BACKGROUND: Investigations at the Danish Anesthesia Allergy Centre have included testing for allergy to chlorhexidine since 1999. OBJECTIVE: To investigate whether measurement of IgE and histamine release confirm an IgE-mediated mechanism for chlorhexidine allergy. METHODS: Twenty-two patients with clinical history suggestive of chlorhexidine allergy were included. Skin tests with chlorhexidine and tryptase measurements were performed during initial investigations. Sera were analyzed retrospectively for IgE and histamine release (passive sensitization) to chlorhexidine. RESULTS: Twelve patients were skin test positive and 10 were skin test negative. Of the skin test-positive patients, 11 of 12 had IgE to chlorhexidine and 7 of 11 had a positive histamine release test. None of the skin test-negative patients had specific IgE or positive histamine release to chlorhexidine. Skin test-positive patients had higher median age (64 vs 49 y) and were mainly male (11/12 vs 6/10). In both groups, 8 patients had hypotension, but bronchospasm mainly appeared in skin test-negative patients (1/12 vs 6/10). Reactions occurred more often during urologic surgery in skin test-positive patients (5/12 vs 0/10). Baseline tryptase was higher in skin test-positive patients (median, 11.5 vs 3.7 microg/L), and 6 of 7 patients had elevated IgE to chlorhexidine in serum at the time of reaction. CONCLUSION: This study confirms that chlorhexidine allergy is IgE-mediated and that measurement of specific IgE and histamine release are good adjuncts to skin testing in patients with clinical history suggesting chlorhexidine allergy. CLINICAL IMPLICATIONS: IgE and histamine release can be used to support the diagnosis of allergy to chlorhexidine.