PubMed · 8777496
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R W Walker, J A Goodhall. Problems caused by osteogenesis imperfecta.. https://pubmed.ncbi.nlm.nih.gov/8777496/
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UNLABELLED: In order to evaluate whether caudal bupivacaine 3.1 mg/kg is associated with early central nervous system toxicity in awake infants, a clinical trial was performed. METHODS: After obtaining Local Ethical Committee approval and informed parental consent, seven awake infants (postconceptual age: 36-52 wks; weight: 2.2-4.7 kg) received a caudal block with bupivacaine 3.1 mg/kg with epinephrine 5 ug/ml in the left lateral position. Before performance of the caudal block a five minute EEG registration was performed, immediately followed by an assessment of the patient's clinical status based on a scoring system of following parameters: level of consciousness; muscular tone in upper extremities, tested by flexion and extension of the elbows; and the quality of the patient's cry in response to a skin pinch. Twenty minutes after the caudal block another EEG was performed and another assessment of the clinical status of the patient. After completion of the clinical assessment blood samples were collected for determination of plasma bupivacaine, albumin and alpha-1 acid glycoprotein concentrations. RESULTS: In six of seven infants the EEG pattern from the first to the second recording showed a shift of the general frequency spectrum towards a lower range. In two of these patients (No. 3 and 4) signs of pharmacologically induced antiepileptic effects (disappearance of sharp waves) were observed. Patients No. 2 and 6 showed signs of increased muscular activity and of suspect epileptic activity. Bupivacaine plasma concentrations ranged from 0.56-1.62 ug/ml, alpha-1 acid glycoprotein levels from 0.33-0.76 g/l and albumin levels from 25-38 g/l. DISCUSSION: In a few patients this systemic effect was clinically also associated with what is usually classified as early central nervous system toxicity. As a result of these findings the study was stopped prematurely, due to safety reasons. The low plasma levels of bupivacaine associated with side effects in this study may have two possible explanations. First, our patients did not receive any sedative drugs or anaesthetics that could have masked symptoms or have increased the threshold for systemic effects. Second, as can be expected in this age group plasma levels of alpha-1 acidglycoprotein were low. Thus, the lower plasma concentrations of total bupivacaine observed in the present study might have been associated with a similar unbound, free concentration of bupivacaine as it is seen in older children and adults at total plasma levels of 2-4 ug/ml and at alpha-1 acidglycoprotein levels within the normal adult range. We conclude that Bupivacaine at 3 mg/kg is associated with systemic side effects in infants receiving awake caudal anaesthesia. Therefore we recommend to aim at a dose of not larger than 2 mg/kg in caudal blocks if no premedication or other sedative drugs are given simultaneously.
UNLABELLED: An increased microvascular water permeability has been reported after ischemia/reperfusion both in animal models and in human studies. We studied the changes in fluid filtration capacity (FFK) after ischemia/reperfusion due to tourniquet in patients undergoing arthroscopy of the knee. METHOD: Healthy male volunteers (n = 24, mean age 46.9 +/- 3.5) were studied prior to, 1 and 6 hours after arthroscopy of the knee, during which a tourniquet was applied to the thigh. FFK, isovolumetric venous pressure (Pvi) and arterial blood flow in the limb was measured in both legs (tourniquet leg and control leg) using computer assisted venous congestion plethysmography. Venous blood samples were obtained from a cubital vein prior to and from the femoral vein 2 mins after deflation of the tourniquet cuff. 12 patients received preoperatively an infusion of 6% Dextran (D) and 12 patients 500 ml of electrolyte solution (VE) an. RESULTS: The mean duration of the tourniquet was (D) 56.0 +/- 6.9 min and (VE) 53.9 +/- 4.2 min which resulted in a significant increase in venous lactate concentration from (D) 1.4 +/- 0.1 mmol.l-1 to 2.7 +/- 0.3 mmol.l-1 and (VE) 1.3 +/- 0.1 mmol.l-1 to 2.7 +/- 0.3 mmol.l-1 (p < 0.001). A significant decrease in pH from (D) 7.39 +/- 0.01 to 7.32 +/- 0.01 (p < 0.001) and from (VE) 7.39 +/- 0.01 to 7.32 +/- 0.01 (p < 0.001) was also seen. Preoperatively no significant differences in the FFK values of the tourniquet leg (D = 5.3 (4.8-10.7) ml. x 10(-3) min-1.100 ml tissue-1 mmHg-1 = FFKU) and the control leg (5.2 (4.7-8.6 FFKU)) were observed. The maximum FFK value in D was seen 1 hour after ischemia/reperfusion in both, the tourniquet leg (7.5 (4.6-14.2 FFKU) and the control leg (7.8 (5.5-9.4 FFKU). In VE however the maximal FFK value were measured 6 hours after ischemia/reperfusion with an increase in the tourniquet leg from 5.2 (4.2-6.2 FFKU) to 8.1 (3.7-10.4 FFKU) and the control leg from 6.1 (3.6-7.0 FFKU) to 7.3 (6.1-8.3 FFKU) (Median (Range). One-way ANOVA). There were no significant differences in the FFK values between D and VE except for a lower Pvi in VE at the third measurement. No significant changes in the arterial blood flow were seen perioperatively as well as between the operated and non-operated leg. CONCLUSION: A tourniquet of < 1 hour does impair tissue oxygenation as indicated by the increase in lactate and the decrease in pH. The duration of the tourniquet was however to short to have caused sufficient microvascular damage result in a more pronounced increase in fluid filtration capacity.
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