H. Wissing

BACKGROUND: Continuous venovenous haemofiltration (CVVH) in the intensive care setting requires anticoagulation to prevent clotting of the extracorporeal circuit. Several protocols avoiding heparin and using regional citrate anticoagulation have been developed to diminish bleeding risks. However, data from randomized trials comparing citrate anticoagulation with systemic heparinization are very limited. METHODS: One hundred and seventy-four patients on mechanical ventilation, requiring renal replacement therapy for acute renal failure, were included in this prospective randomized multicentre trial comparing regional citrate with systemic heparin. The study was performed at nine different intensive care units at university or academic teaching hospitals. The participants were randomized to either CVVH using regional citrate anticoagulation or CVVH using systemic anticoagulation with unfractionated heparin. The primary outcome was to compare treatment efficacy represented by the patients' acid base status on Day 3 and on each consecutive day. Several parameters of safety and efficacy were analysed as secondary outcomes. RESULTS: Comparison of standard bicarbonate from Day 3 to Day 11 revealed no difference between both treatment modalities. Use of citrate resulted in less systemic anticoagulation, a lower risk of bleeding and a longer haemofilter patency. Episodes of hypercalcaemia, hypocalcaemia and the need for additional bicarbonate infusions occurred more often under citrate. The patients' high mortality was not influenced by the mode of anticoagulation. CONCLUSIONS: Citrate may be used as a regional anticoagulant and the only buffering agent in CVVH with adequate treatment efficacy and safety. However, neither citrate nor heparin anticoagulation should be regarded as a therapeutic standard, since there is no advantage of one of these substances with regard to patient mortality.

OBJECTIVE: We report the results and complications associated with standardized intraoperative management designed for the prevention of hemodynamically relevant venous air embolism during surgery performed in the semisitting position. METHODS: A protocol for preoperative evaluation and intraoperative monitoring was developed and applied in 187 consecutive patients who underwent surgery in the semisitting position between 1999 and 2004. The protocol included preoperative transesophageal echocardiography examination (TEE), intraoperative TEE monitoring, catheterization of the right atrium and a combination of fluid input, positive end expiratory pressure, and standardized positioning aiming at a positive pressure in the transverse and sigmoid sinuses. Data were collected retrospectively from the charts and intraoperative anesthesiological protocols of the patients for the incidence of clinically relevant air embolism (i.e., TEE-diagnosed air embolism plus a decrease in end tidal CO2 or hemodynamic changes) and other complications related to the semisitting position. RESULTS: Three cases (1.6%) of relevant venous air embolism occurred in 187 patients. Only 1 case (0.5%) was hemodynamically relevant, with temporary arterial blood pressure decrease and heart rate increase. Pneumatocephalus leading to lethargy was a frequent postoperative finding, which resolved spontaneously in all except 1 patient with epileptic seizure and oculomotor nerve palsy attributable to space-occupying subdurally trapped air, which had to be treated surgically. There was no permanent morbidity or mortality related to the semisitting position. CONCLUSION: Fear of massive venous air embolism is one reason for dramatic decline in the use of the semisitting position in neurosurgical practice. We found that strict adherence to a standardized protocol using TEE monitoring before and during surgery; exclusion of patients with patent foramen ovale; and a combination of positive end expiratory pressure, fluid input, and a standardized position aiming a positive pressure in the transverse and sigmoid sinuses helped to greatly minimize this complication to a rate of 0.5% for hemodynamically relevant events.

In a prospective, randomized parallel study, 60 ASA I-III children aged 1-17 years, scheduled for elective strabismus surgery, were anaesthetized with desflurane without prophylactic antiemetic medication. The objective of the study was to determine the incidence of postoperative nausea and vomiting after general anaesthesia with desflurane. To decide whether nitrous oxide further influences these symptoms, the patients were randomly assigned to two groups of 30 patients each. One group received desflurane in oxygen/air and a second group received desflurane in oxygen/nitrous oxide. In all children, after intravenous induction and tracheal intubation, anaesthesia was administered as minimal flow anaesthesia with oxygen and nitrous oxide or air according to the random plan. The patients were observed for 48 postoperative hours until their discharge from the ward. The overall incidence of nausea was found to be 37%, and vomiting was seen in 32% of all patients. No statistical correlation was found between the incidence of postoperative emesis and the administration of nitrous oxide or the duration of general anaesthesia. Instead, the incidence of vomiting was 2.5-fold higher when surgery was performed on both eyes compared with one eye. The relatively low incidence of postoperative nausea and vomiting, as well as the quick recovery from anaesthesia, permitting an early discharge from the postoperative care unit to the ward, show desflurane to be a suitable volatile anaesthetic in strabismus surgery in children.