Dead space and paediatric anaesthetic equipment: a physical lung model study

Untested assumptions have been made with regard to functional dead space in facemasks, filters and breathing systems used in children for the administration of inhalation anaesthesia. Total functional dead space was measured in various combinations of this equipment applied to a spontaneous ventilation lung model with parameter settings appropriate for infants of 7-8 kg. We found that functional dead space was too large to allow for spontaneous ventilation of the lungs when a breathing filter was fitted. There was minimal relationship between size of the facemask and functional dead space; however, the provision of 22-mm female inlets to facemasks achieved proportionately less functional dead space than with 15-mm male inlets. Regardless of the apparatus used and the magnitude of the dead space, the leak induced when a poorly fitting facemask was used dramatically reduced the dead space of the breathing system - to near optimal conditions - by moving the alveolar gas elimination point to within the facemask itself.     

Impact of bispectral index monitoring on stress response and propofol consumption in patients undergoing coronary artery bypass surgery

BACKGROUND: Bispectral Index (BIS)-titrated administration allows a reduction of propofol infusion rates in patients undergoing surgery. Resulting differences in anesthetic depth might affect the stress response to surgery involving neural circuitry not reflected in the electroencephalogram. METHODS: Forty patients scheduled to undergo elective coronary artery bypass grafting receiving a background infusion of remifentanil (0.3 microg . kg . min) were anesthetized with intravenous propofol delivered by target-controlled infusion according to the Marsh pharmacokinetic model under BIS monitoring. In a randomized, prospective design, 20 patients received propofol at a target concentration of 3 microg/ml, whereas in 20 patients propofol was titrated to maintain a BIS value of 40-50. Plasma concentrations of propofol (by means of gas chromatography-mass spectrometry), epinephrine, norepinephrine (by means of high-pressure liquid chromatography), cortisol (by means of radioimmunoassay), and interleukins 6 and 10 (by means of enzyme-linked immunosorbent assay) were measured repeatedly throughout surgery. RESULTS: BIS monitoring allowed a 30% reduction of propofol infusion rates and a similar decrease in plasma propofol concentrations in the BIS group without affecting the stress response to surgery for the group mean. None of the patients reported awareness during a standardized interview. Interestingly, propofol-remifentanil anesthesia blunted the release of epinephrine and cortisol to bypass surgery completely even when the propofol infusion rate was reduced according to BIS values. CONCLUSIONS: Total intravenous anesthesia using propofol-remifentanil effectively attenuates the neurohumoral stress response to coronary bypass surgery involving cardiopulmonary bypass. Titration of propofol using BIS allows for significant reduction of propofol consumption, with only minor effects on stress response under these conditions.     

Left heart bypass during descending thoracic aortic aneurysm repair does not reduce the incidence of paraplegia

BACKGROUND: The preferred technique for spinal cord protection during surgical repair of descending thoracic aortic aneurysms (DTAAs) remains controversial. The purpose of this retrospective analysis was to determine if the use of left heart bypass (LHB) reduced the incidence of paraplegia in patients who underwent DTAA repair. METHODS: Over a 15-year period 387 consecutive patients underwent surgical repair of DTAAs using either the "clamp-and-sew" technique (341 patients, 88.1%) or distal aortic perfusion via a LHB circuit (46 patients, 11.9%). Data regarding patient characteristics, operative variables, and outcomes were retrieved from a prospectively maintained database. The impact of LHB on the frequency of paraplegia was determined using univariate and propensity score analyses. RESULTS: There were 17 operative deaths (4.4%) including 11 patients (2.8%) who died within 30 days. Paraplegia occurred in 10 patients (2.6%). On univariate analysis increasing age (p = 0.03), increasing aortic clamp time (p < 0.001), increasing red blood cell transfusion requirements (p = 0.01), and acute dissection (p = 0.03) were associated with increased incidence of paraplegia. Patients who received LHB had a similar incidence of paraplegia (2/46, 4%) compared with those treated without LHB (8/341, 2.3%; p = 0.3). Both matching and stratification propensity score analyses confirmed that LHB was not associated with reduced risk of paraplegia. CONCLUSIONS: On retrospective analysis the use of LHB during DTAA repair did not reduce the incidence of spinal cord injury. The "clamp-and-sew" technique remains an appropriate approach to DTAA repair.     

Repair of a left main coronary artery aneurysm using the circumflex femoral artery as a Y-interposition graft

Left main coronary artery aneurysms are rare, and treatment options are poorly defined. Here we report the surgical management of a female patient who presented with an acute coronary syndrome resulting from dissection of an aneurysmal left main. She was successfully managed with an interposition graft fashioned from the lateral femoral circumflex artery.     

Soft tissue and intra-articular injection of bupivacaine, epinephrine, and morphine has a beneficial effect after total knee arthroplasty

The purpose of this study was to determine if an intraoperative intraarticular and soft-tissue injection of local anaesthetic, epinephrine, and morphine has a beneficial effect for total knee arthroplasty. A control group of 138 patients (181 knees) received no intraoperative injection. The study group of 171 patients (197 knees) received intraoperative injection of 0.25% bupivacaine with epinephrine and morphine with 2/3 injected into the soft tissues and 1/3 injected into the joint. Patients having bilateral simultaneous procedures received a divided dose. The pain treatment protocol otherwise was identical. Pain, sedation, rescue narcotic usage, narcotic reversal and blood loss were examined. Pain levels during the immediate postoperative period, blood loss, and bleeding indices were reduced with injection. Considerably more control patients required rescue doses of narcotics. Preemptive analgesia with soft tissue and intra-articular injection of long-acting local anesthetic with epinephrine and morphine provides better pain control in the immediate postoperative period, decreases blood loss, and decreases the need for rescue narcotics and reversal agents. This simple, inexpensive method provides an effective adjunct to a multimodal approach in improving the postoperative course of primary total knee arthroplasty.     

Depot local anesthetic in polymethylmethacrylate bone cement: a preliminary study

Acrylic bone cement has been used successfully as a slow-release depot for antibiotics after orthopaedic surgery. The feasibility of administering local anesthetics in this way was examined in this preliminary in vitro study. Discs weighing approximately 4 g were prepared from five brands of acrylic cement (40 g) containing as much as 2 g of anesthetic base. Elution of the anesthetics into saline was measured during 72 hours. Prilocaine eluted the fastest and bupivacaine the slowest, with lidocaine between them. The elution rates were greatest in the first hour, declining thereafter. Rates also depended on the brand of cement with the quickest elution from CMW3 and the slowest from Surgical Simplex P. Using cement as a depot, therapeutic levels of a drug should be achievable in vivo at a negligible risk of toxicity. Before in vivo trials it is necessary to optimize elution of drugs in relation to the cement (brand, microstructure, method of preparation) and the concentration of a drug in the cement above which the cements' mechanical and adhesive properties are compromised.     

Total wrist arthroplasty

With the advent of newer prosthetic designs, total wrist arthroplasty provides a functional range of motion, better wrist balance, reduced risk of loosening, and better implant stability.     

Post-acute brain injury rehabilitation for patients with stroke

Primary objective: Conduct an investigation of post-acute brain injury rehabilitation (PABIR) for persons with stroke.

Research design: Pre-post-treatment observation study.

Methods and procedures: Demographic and medical data for 127 persons with stroke admitted for PABIR at a median interval of 87 days post-stroke were abstracted from medical records. Participants' levels of independence and productivity were assessed at admission and discharge. Follow-up data were available for 90 participants at a median interval of 346 days post-discharge.

Experimental interventions: Not applicable.

Main outcomes and results: Participants showed improvements in productivity and independence level from admission to discharge and these gains were maintained at follow-up. Predictors of productivity at discharge were gender and level of independence at admission (Model R² = 0.28). Predictors of independence at discharge were similar (Model R² = 0.37).

Conclusion: While this investigation has limitations, findings suggest that PABIR is beneficial for some persons with strokes.