Haemostatic changes caused by i.v. regional anaesthesia with lignocaine

The various components of i.v. regional anaesthesia (IVRA), that is ischaemia, tourniquet compression and the presence of high concentrations of local anaesthetics in the blood vessels of the extremity, may affect haemostatic mechanisms. We performed a cross-over study in 10 healthy male volunteers to examine the role of lignocaine in IVRA on several haemostatic variables, and those indicating fibrinolysis and platelet function in particular. Venous blood samples were obtained from the test arm and the opposite arm before IVRA, at the time of tourniquet cuff deflation and 30 min thereafter. Metal needle punctures were used, and for the sample from the test arm at the time of cuff deflation, cuff pressure was reduced from 300 mm Hg to individual mean arterial pressure. The IVRA technique included exsanguination by arm elevation and axillary artery compression, inflation of the tourniquet cuff for 20 min and deflation of the cuff in one step (after obtaining the venous sample). Each subject received, in random order, either 0.5% lignocaine 3 mg kg-1 or the corresponding volume of saline i.v. All fibrinolysis markers, that is, D-dimer, tissue plasminogen activator antigen (t-PA antigen), tissue plasminogen activator activity (t-PA activity), plasminogen activator inhibitor activity (PAI) and protein C indicated enhanced fibrinolysis by IVRA, but only t-PA antigen and PAI showed greater changes in the lignocaine compared with the saline group in the exposed arm at the time of cuff deflation. Platelet function tests (ADP-induced platelet aggregation, beta-thromboglobulin and thrombelastogram (TEG)) indicated no differences between the lignocaine and saline groups. Although IVRA appeared to induce some platelet dysfunction, there was a small increase in TEG amplitude indicative of improved fibrin-platelet interaction in the lignocaine-exposed arm at the time of cuff deflation. We conclude that the presence of high i.v. lignocaine concentrations (median 144.4 micrograms ml-1 in cubital veins at the end of the tourniquet time) potentiated ischaemia-induced fibrinolysis activation during IVRA. Concomitant platelet dysfunction was not aggravated by lignocaine.     

Audit pinpoints i.v. drug administration pitfalls

This paper describes an approach to auditing the time spent by nurses giving intravenous drugs. The results of the audit, carried out at Wycombe General Hospital, are reported and discussed together with the measures taken to address practical and medico-legal issues. The authors conclude that much nursing time could be saved with closer adherence to guidelines for practice.     

Benefits of high-dose i.v. immunoglobulin in patients with severe steroid-dependent asthma

STUDY OBJECTIVE: To determine the efficacy of IV immunoglobulin (IVIg) in severe asthma to reduce steroid requirements. DESIGN: Pre- and posttreatment measurements were analyzed using Dunnett's multiple comparison procedure. SETTING: Hospital clinical research center. PATIENTS: Eleven adolescents and adults with severe, steroid-dependent asthma enrolled over a 14-month period. INTERVENTIONS: IVIg was administered at a dose of 2 g/kg every 4 weeks for a total of seven infusions. MEASUREMENTS AND RESULTS: Steroid requirements, pulmonary function including lung volumes, symptom scores, bone densitometry, and airway reactivity monitored by methacholine challenge were followed over the course of 7 months. A significant decrease in steroid usage was achieved. Despite substantial steroid reduction, the patients demonstrated improvement in their pulmonary function and symptom scores. The responses to methacholine challenge were unaffected by IVIg treatment. CONCLUSIONS: IVIg provides a potentially important adjunctive therapy in severe asthma, reducing oral steroid requirements and steroid side effects without deterioration of lung function.     

Evaluation of saline for i.v. locks in children

A practice change to saline for peripheral IV maintenance was evaluated in a large teaching hospital in the Midwest. Subjects (N = 126) were children over 28 days of age, with peripherally placed IVs. Group I (n = 68) were children randomly selected to receive saline flush in an experimental study. Group II (n = 58) consisted of children receiving the saline flush after the change in practice was made. There was no significant difference between groups for either of two measures of IV duration. The mean duration of the IV from first flush was 35.38 hours for Group I and 44.09 hours for Group II; the time from insertion to discontinuation was 60.86 and 60.03 hours respectively. Patient age, site location, number of flushes, number of irritating medications, and site complications did not differ significantly between groups. The results of this clinical evaluation support previous findings that saline is efficacious for maintaining the patency of peripheral IVs in children over 28 days of age.     

Pulmonary atresia with intact i.v. septum (author''s transl)

Eight cases of pulmonary atresia with intact ventricular septum, are reviewed. Three corresponded to the group with small or hypoplastic right ventricle and five to the one with normal or enlarged right ventricular cavity. The electrocardiogram was of less value than plain chest radiography for the differential diagnosis of both groups. Cardiac catheterization revealed a right to left atrial shunt and the suprasystemic level of the right ventricular pressure. Selective angiocardiography demonstrates the stop of contrast at the level of pulmonary valve. Five patients were operated. An ascending aorta to right pulmonary artery anastomosis, Waterston type, was performed in three patients. Pulmonary valvotomy was carried out in the others.     

Interaction of i.v. anaesthetic agents with 5-HT3 receptors

Using N1E-115 neuroblastoma cells as an experimental model, we have examined if four commonly used i.v. anaesthetic induction agents interact with 5-HT3 receptors. Specifically, we tested the hypothesis that the antiemetic effects of propofol may result from 5-HT3 receptor antagonism. Binding of tropisetron (a 5-HT3 selective reference compound), etomidate, ketamine, thiopentone and propofol to 5-HT3 receptors was assessed by measuring the displacement of [3H]BRL 43694 from whole N1E-115 cells. The rank order potency (Ki) was tropisetron (1.7 (SEM 0.2) nmol litre-1) > etomidate (83.(4) mumol litre-1) > or = ketamine (97 (4) mumol litre-1) > thiopentone (177 (9) mumol litre-1) > propofol (819 (171) mumol litre-1). With the exception of thiopentone these effects were outside the clinical range and suggest that anaesthetic agents are unlikely to interact directly with 5-HT3 receptors, and that other mechanism(s) must underlie the antiemetic effects of propofol.     

Centralized i.v. team provides inpatient and home-care treatment

AIM: The study of the effects of the inhibitor of angiotensin converting enzyme ramipril (tritace) on the 24-h profile of blood pressure (BP) in patients with mild and moderate arterial hypertension. MATERIALS AND METHODS: Ramipril was given to 21 males aged 45-68 years with essential hypertension stage II (WHO criteria) with stable elevated diastolic blood pressure (95-114 mm Hg) in a single dose 2.5-10 mg/day. Captopril controls received 100 mg twice a day. BP was monitored using "SpaceLabs Medical" unit (model 90207, USA). RESULTS: Compared to placebo, ramipril lowered systolic and diastolic blood pressure both for the 24-h period and in the day time; captopril lowered only diastolic BP in the day time. Side effects of long-term application of ramipril occurred 2 times less frequently than in application of captopril. CONCLUSION: Long-term treatment with ramipril in the above regimen provides more effective control of BP than captopril in the above doses in patients with mild and moderate hypertension.     

Health center-supplier team approach to solving i.v. equipment problems

A team approach to problem solving in which a health care center and a supplier worked together to improve product quality is described and a detailed example is provided. When the health care center began using a new supplier for i.v. solutions and equipment, the supplier's incomplete product line and recurrent functional problems with products led to dissatisfaction of staff members. The supplier suggested that the health care center and supplier form a quality action team. The team addressed eight product concerns by using a total quality management process. For each concern, the team defined the problem and formulated a problem statement, collected data and determined the contributing factors to the problem, developed an action plan for solving the problem, and executed the plan and monitored its impact. After the first meeting, the team met monthly to monitor progress and discuss new ways they could work together to improve product quality and reduce costs. The implementation of the action plans allowed the health care center to realize cost savings and increased staff members' satisfaction with the supplier's products. A quality action team, composed of representatives from a health care center and one of its suppliers, used a total quality management process to solve problems to the satisfaction of both sets of participants.     

Inhibition of naloxone-precipitated withdrawal jumping by i.c.v. and i.t. administration of saline in morphine-dependent mice

In morphine-dependent mice, s.c. and i.t. administered naloxone produced withdrawal jumping (ED50 values were i.t. = s.c.) but i.c.v. administered naloxone failed to produce dose-dependent jumping. Peak times of jumping were earliest after i.t. administration of naloxone among the three administration routes. These results suggested that the spinal site was more sensitive to naloxone than the supraspinal site. Concomitant administration of naloxone i.c.v. and i.t. did not precipitate jumping. It was found that i.c.v. and i.t. injections of saline inhibited withdrawal jumping precipitated by s.c. administered naloxone and that the i.c.v. effect was more profound than the i.t. effect. I.c.v. injection of saline also delayed the peak time of withdrawal jumping precipitated by s.c. administered naloxone. These inhibitory effects of the injection procedures may explain the difficulty of i.c.v. administered naloxone and concomitant i.c.v. + i.t. administered naloxone to precipitate jumping, and may explain the difference in the ED50 values of naloxone and the time courses of jumping.     

The use of continuous i.v. sedation is associated with prolongation of mechanical ventilation

STUDY OBJECTIVE: To determine whether the use of continuous i.v. sedation is associated with prolongation of the duration of mechanical ventilation. DESIGN: Prospective observational cohort study. SETTING: The medical ICU of Barnes-Jewish Hospital, a university-affiliated urban teaching hospital. PATIENTS: Two hundred forty-two consecutive ICU patients requiring mechanical ventilation. INTERVENTIONS: Patient surveillance and data collection. MEASUREMENTS AND RESULTS: The primary outcome measure was the duration of mechanical ventilation. Secondary outcome measures included ICU and hospital lengths of stay, hospital mortality, and acquired organ system derangements. A total of 93 (38.4%) mechanically ventilated patients received continuous i.v. sedation while 149 (61.6%) patients received either bolus administration of i.v. sedation (n=64) or no i.v. sedation (n=85) following intubation. The duration of mechanical ventilation was significantly longer for patients receiving continuous i.v. sedation compared with patients not receiving continuous i.v. sedation (185+/-190 h vs 55.6+/-75.6 h; p<0.001). Similarly, the lengths of intensive care (13.5+/-33.7 days vs 4.8+/-4.1 days; p<0.001) and hospitalization (21.0+/-25.1 days vs 12.8+/-14.1 days; p<0.001) were statistically longer among patients receiving continuous i.v. sedation. Multiple linear regression analysis, adjusting for age, gender, severity of illness, mortality, indication for mechanical ventilation, use of chemical paralysis, presence of a tracheostomy, and the number of acquired organ system derangements, found the adjusted duration of mechanical ventilation to be significantly longer for patients receiving continuous i.v. sedation compared with patients who did not receive continuous i.v. sedation (148 h [95% confidence interval: 121, 175 h] vs 78.7 h [95% confidence interval: 68.9, 88.6 h]; p<0.001). CONCLUSION: We conclude from these preliminary observational data that the use of continuous i.v. sedation may be associated with the prolongation of mechanical ventilation. This study suggests that strategies targeted at reducing the use of continuous i.v. sedation could shorten the duration of mechanical ventilation for some patients. Prospective randomized clinical trials, using well-designed sedation guidelines and protocols, are required to determine whether patient-specific outcomes (eg, duration of mechanical ventilation, patient comfort) can be improved compared with conventional sedation practices.     

Hemodynamic effects caused by i.v. administration of verapamil in healthy subjects

The hemodynamic data obtained after rapid i.v. administration of verapamil (Isoptin) (7.5-12.5 mg) to 7 healthy subjects are presented and discussed. The drug caused an early and statistically significant increase in heart rate and output with concomitant decrease of blood pressure (mainly diatolic) and peripheral resistance. Negative inotropic effects were not observed by the decreased peripheral resistance probably masks any possible negative inotropic effects of the drug.     

A phase II study of i.v. methylprednisolone in secondary-progressive multiple sclerosis

We have used rats with streptozotocin-induced diabetes to investigate the effects of hyperglycaemia-mediated impaired nucleoside uptake on the actions of endogenous adenosine in hippocampal slices. In control tissue under conditions of anoxia and aglycaemia the rise in the extracellular adenosine concentration resulted in complete inhibition of synaptic activity in about 2 min. In slices from previously hyperglycaemic rats the inhibition of synaptically mediated responses occurred significantly faster, although this change could be prevented by insulin treatment. Application of the selective adenosine A1 receptor antagonist [8-cyclopentyl-1,3-dipropylxanthine (DPCPX)] prevented the anoxia/aglycaemia-mediated inhibition and, furthermore, abolished the differences in the electrophysiological responses between control and diabetic tissue. The effects of impaired nucleoside uptake could be mimicked in control slices by applying the nucleoside uptake blocker hydroxynitrobenzylthioinosine (HNBTI). This had the effect of speeding up the rate of anoxia/aglycaemia-induced synaptic inhibition in control tissue to that seen in diabetic tissue. However, such treatment had no effect on the responses in diabetic tissue as expected if the HNBTI-sensitive uptake process was already inhibited by the chronic hyperglycaemia. The impairment of nucleoside uptake by chronic hyperglycaemia results in the potentiation of the modulatory actions of endogenous adenosine in the central nervous system. Such an alteration in adenosine function may be important in explaining behavioural and pathological changes associated with diabetes mellitus.