A novel combination of peripheral nerve blocks for arthroscopic shoulder surgery.

BACKGROUND: Interscalene brachial plexus block is currently the gold standard for intra- and post-operative pain management for patients undergoing arthroscopic shoulder surgery. However, it is associated with block related complications, of which effect on the phrenic nerve have been of most interest. Side effects caused by general anesthesia, when this is required, are also a concern. We hypothesized that the combination of superficial cervical plexus block, suprascapular nerve block, and infraclavicular brachial plexus block would provide a good alternative to interscalene block and general anesthesia. METHODS: Twenty adult patients scheduled for arthroscopic shoulder surgery received a combination of superficial cervical plexus block (5 ml ropivacaine 0.5%), suprascapular nerve block (4 ml ropivacaine 0.5%), and lateral sagittal infraclavicular block (31 ml ropivacaine 0.75%). The primary aim was to find the proportion of patients who could be operated under light propofol sedation, without the need for opioids or artificial airway. Secondary aims were patients' satisfaction and surgeons' judgment of the operating conditions. RESULTS: Nineteen of twenty patients (95% CI: 85-100) underwent arthroscopic shoulder surgery with light propofol sedation, but without opioids or artificial airway. The excluded patient was not comfortable in the beach chair position and therefore received general anesthesia. All patients were satisfied with the treatment on follow-up interviews. The surgeons rated the operating conditions as good for all patients. CONCLUSION: The novel combination of a superficial cervical plexus block, a suprascapular nerve block, and an infraclavicular nerve block provides an alternative anesthetic modality for arthroscopic shoulder surgery.

A randomised placebo-controlled trial examining the effect on hand supination after the addition of a suprascapular nerve block to infraclavicular brachial plexus blockade.

Some surgeons believe that infraclavicular brachial plexus blocks tends to result in supination of the hand/forearm, which may make surgical access to the dorsum of the hand more difficult. We hypothesised that this supination may be reduced by the addition of a suprascapular nerve block. In a double-blind, randomised, placebo-controlled study, our primary outcome measure was the amount of supination (as assessed by wrist angulation) 30 min after infraclavicular brachial plexus block, with (suprascapular group) or without (control group) a supplementary suprascapular block. All blocks were ultrasound-guided. The secondary outcome measure was an assessment by the surgeon of the intra-operative position of the hand. Considering only patients with successful nerve blocks, mean (SD) wrist angulation was lower (33 (27) vs. 61 (44) degrees; p = 0.018) and assessment of the hand position was better (11/11 vs. 6/11 rated as 'good'; p = 0.04) in the suprascapular group. The addition of a suprascapular nerve block to an infraclavicular brachial plexus block can provide a better hand/forearm position for dorsal hand surgery.

Enhanced Recovery After Surgery (ERAS) for gastrointestinal surgery, part 2: consensus statement for anaesthesia practice.

BACKGROUND: The present interdisciplinary consensus review proposes clinical considerations and recommendations for anaesthetic practice in patients undergoing gastrointestinal surgery with an Enhanced Recovery after Surgery (ERAS) programme. METHODS: Studies were selected with particular attention being paid to meta-analyses, randomized controlled trials and large prospective cohort studies. For each item of the perioperative treatment pathway, available English-language literature was examined and reviewed. The group reached a consensus recommendation after critical appraisal of the literature. RESULTS: This consensus statement demonstrates that anaesthesiologists control several preoperative, intraoperative and postoperative ERAS elements. Further research is needed to verify the strength of these recommendations. CONCLUSIONS: Based on the evidence available for each element of perioperative care pathways, the Enhanced Recovery After Surgery (ERAS®) Society presents a comprehensive consensus review, clinical considerations and recommendations for anaesthesia care in patients undergoing gastrointestinal surgery within an ERAS programme. This unified protocol facilitates involvement of anaesthesiologists in the implementation of the ERAS programmes and allows for comparison between centres and it eventually might facilitate the design of multi-institutional prospective and adequately powered randomized trials.

Minimum effective volume of ropivacaine 7.5 mg/ml for an ultrasound-guided infraclavicular brachial plexus block.

BACKGROUND: Ultrasound guidance has been shown to reduce the minimum effective volume (MEV) of local anaesthetics for several peripheral nerve blocks. Although the lateral sagittal infraclavicular block (LSIB) is a well-established anaesthesia method, MEV for this technique has not been established. Our aim with this study was to determine the MEV using ropivacaine 7.5 mg/ml for the LSIB method. METHODS: Twenty-five adult American Society of Anesthesiologists physical status I-II patients scheduled for hand surgery received an ultrasound-guided LSIB with ropivacaine 7.5 mg/ml. A successful block was defined as anaesthesia or analgesia for all five sensory nerves distal to the elbow, 30 min after local anaesthetic injection. The MEV for a successful block in 50% of the patients was determined by using the staircase up-and-down method introduced by Dixon and Massey. Logistic regression and probit transformation were applied to estimate the MEV for a successful block in 95% of the patients. RESULTS: The patients received ropivacaine 7.5 mg/ml volumes in the range of 12.5-30 ml. The MEVs in 50% and 95% of the patients were 19 ml [95% confidence interval (CI), 14-27] and 31 ml (95% CI, 18-45), respectively. CONCLUSIONS: For surgery distal to the elbow, the MEV in 95% of patients for an ultrasound-guided LSIB with ropivacaine 7.5 mg/ml was estimated to be 31 ml (95% CI, 18-45 ml). Further studies should determine the factors that influence the volume of local anaesthetic required for a successful infraclavicular block.

Contractile response of femoral arteries in pigs with acute liver failure.

BACKGROUND: Acute liver failure (ALF) is characterized haemodynamically by a progressive hyperdynamic circulation. The pathophysiological mechanism is unknown, but impaired contractility of vascular smooth muscle may play an important role. The aim of this study was to evaluate the vascular response to stimulation with norepinephrine and angiotensin II in endothelium-denuded femoral artery rings. METHODS: Norwegian Landrace pigs weighing 27.1 +/- 0.5 kg (mean +/- sx (standard error of the mean)) were used. ALF was induced by performing a portacaval shunt followed by ligation of the hepatic arteries (n = 6). Sham-operated animals served as controls (n = 5). Cumulative isometric concentration contraction curves were obtained after in vitro stimulation of the femoral artery rings with either angiotensin II (10(-13) - 10(-5) mol/L) or norepinephrine (10(-13) - 10(-3) mol/L). RESULTS: Pigs suffering from ALF developed a hyperdynamic circulation with an increased cardiac index (P = 0.017) and decreased systemic vascular resistance index (P = 0.015). Studies of the hind leg revealed a decreased vascular resistance index and increased blood flow compared to sham-operated controls (P = 0.003 and P = 0.01, respectively). Angiotensin II caused a concentration-dependent contraction of the arterial segments, with no significant differences in vascular responses between the two groups. Maximum force generated did not differ (55 +/- 7 versus 56 +/- 7 mN, P = 0.95). Furthermore, there were no differences for norepinephrine in the cumulative concentration-response curves and the maximum contractile force was not significantly different (87 +/- 8 versus 93 +/- 16 mN, P = 0.55). CONCLUSIONS: This study documents for the first time that there are no signs of endothelium-independent peripheral vascular hyporesponsiveness to angiotensin II and norepinephrine in pigs with ALF.

An experimental large animal model for the assessment of bioartificial liver support systems in fulminant hepatic failure.

BACKGROUND: Pre-clinical assessment of bioartificial liver support systems requires a highly reproducible large animal model. The main objective of the present study was to develop a valid large animal model for assessing novel bioartificial liver support systems in fulminant hepatic failure. METHODS: A complete liver devascularization procedure was performed in 10 female pigs weighing 25-38 kg. Five matched pigs were sham-operated and served as controls. RESULTS: Pigs with fulminant hepatic failure developed a hyperdynamic circulation, with increased cardiac index (P(GT) < .0001), decreased systemic vascular resistance index (P(GT) < .0001) and mean arterial pressure (P(GT) = .001). Furthermore, intracranial hypertension developed (P(GT) < .0001). with increased common carotid artery flow (P(GT) < .0001) and decreased common carotid resistance (P(G) = .003). Femoral artery flow increased (P = .036). while hindleg resistance (P < .001) and renal artery resistance decreased (P = .019). Oxygen consumption (P(GT) = .050) and oxygen extraction ratio (P(GT) = .001) increased compared to controls. Arterial ammonia, venous aspartate aminotransferase and bilirubin levels increased (P(GT) < .0001, respectively). Abnormal haemostasis developed with significant loss of platelets (P(GT) = .010), decreasing fibrinogen levels (P(G) = .001) and increasing international normalized ratio (P(GT) = .012) and activated clotting time (PGT < .001). Urine became hypo-osmotic (P < .001. P(G) = .011), with decreased sodium levels (P = .08) and increased potassium levels (P(G) = .025). CONCLUSIONS: This study characterizes a reproducible large animal model for fulminant hepatic failure that seems suitable for the assessment of bioartificial liver support systems.

N-acetylcysteine increases cerebral perfusion pressure in pigs with fulminant hepatic failure.

OBJECTIVE: Intravenous administration of N-acetylcysteine beyond 15 hrs reduces mortality rates in patients suffering from paracetamol-induced fulminant hepatic failure, although the mechanism of the therapeutic benefit remains unclear. We hypothesized increased survival to be caused by improved hemodynamic performance. The main objective for the study was to explore the effect of N-acetylcysteine on hemodynamics, oxygen transport, and regional blood flow in pigs with fulminant hepatic failure. DESIGN: Prospective, randomized, controlled trial. SETTING: Surgical research laboratory in a university hospital. SUBJECTS: Female Norwegian Landrace pigs. INTERVENTIONS: Fulminant hepatic failure was induced by a total liver devascularization procedure. Five hours later, the pigs were allocated to N-acetylcysteine treatment (150 mg.kg-1 in 100 mL of 0.9% saline over 15 mins, followed by 50 mg.kg-1 in 500 mL of 0.9% saline over a period of 4 hrs) or placebo. MEASUREMENTS AND MAIN RESULTS: Mean arterial pressure stabilized in the N-acetylcysteine group and increased slightly during the last 2 hrs (pGT =.009). Thus, mean arterial pressure was significantly higher compared with placebo after 3 hrs (p =.01). Cerebral perfusion pressure was significantly higher during the last 2 hrs in the N-acetylcysteine group (pGT =.033). Common carotid artery flow also increased and was maintained at a higher level compared with placebo (pG =.027). Systemic vascular resistance index initially decreased but then gradually increased (pGT <.001). Cardiac index increased after 15 mins of N-acetylcysteine infusion, causing a significant interaction (pGT =.038), but did not differ after 3 hrs. No significant differences in hindleg and mesentery hemodynamics were found. A short-lived increase in oxygen delivery caused by a temporary increase in cardiac index was observed but without any corresponding increase in oxygen consumption. CONCLUSIONS: Intravenous N-acetylcysteine infusion increases cerebral perfusion pressure in pigs with fulminant hepatic failure. Earlier reported effects on oxygen transport and uptake could not be confirmed.

Renal elimination of protein S-100beta in pigs with acute encephalopathy.

BACKGROUND: Protein S-100beta is an established biochemical marker for cerebral injury in serum. For the further interpretation and possible use of S-100beta serum measurements in acute hepatic encephalopathy, renal elimination of S-100beta was measured in pigs with elevated S-100beta levels due to hepatic encephalopathy. METHODS: Eighteen female Norwegian Landrace pigs were randomly allocated to either hepatic devascularization (n=13) or sham operation (n=5). Repeated samples from the common carotid artery, right renal vein, and urine were simultaneously drawn for S-100beta analysis, using the Sangtec100 Liamat immunoassay. RESULTS: In hepatic devascularized pigs, arterial serum levels of S-100beta increased from 0.96+/-0.04 microg/L (mean +/- SEM) at t = 0h to 1.74+/-0.11 microg/L (mean +/- SEM) at t = 5 h. Urinary excretion increased simultaneously from 8.48+/-3.66 ng/h (mean +/- SEM) to 20.4+/-9.54 ng/h (mean +/- SEM), while renal arterial-venous fluxes for both kidneys increased from 1022+/-404 ng/h (mean +/- SEM) to 2444+/-590 ng/h (mean +/- SEM). CONCLUSIONS: Increased arterial S-100beta levels in pigs with acute hepatic encephalopathy are not a result of decreased renal elimination. The large difference between the renal arterial venous S-100beta concentrations and the urinary excretion of S-100beta indicate that renal metabolism is the major route of elimination.

Myocardial metabolism and efficiency after warm continuous blood cardioplegia.

BACKGROUND: Warm continuous blood cardioplegia (WCBCP) has been recommended during prolonged cardiac arrest to minimize functional deterioration. Myocardial metabolism and efficiency after this cardioplegic modality are not well described. METHODS: Substrate oxidation, blood flow, and myocardial function were measured before, during, and after 3 hours of WCBCP in 7 pigs. RESULTS: Free fatty acid and glucose oxidation decreased by 60% +/- 3.8% and 94% +/- 1.2%, respectively, during cardioplegia (both p < 0.05) and increased to 62% +/- 28% and 122% +/- 62% of baseline during the early recovery phase (p < 0.05 for glucose). One hour after WCBCP oxidation rates were similar to baseline. The transient postcardioplegic increase in substrate oxidation was associated with a 43% +/- 23% elevation of oxygen consumption (MVO2) compared with baseline and a 62% +/- 18% increase in myocardial blood flow. Cardiac output and mean arterial pressure did not change significantly after WCBCP, although myocardial function (stroke work, left ventricular end-systolic pressure, end-diastolic pressure, contractility, and efficiency) was depressed (p < 0.05). End-diastolic pressure and contractility improved from early to late phase of recovery, whereas the other indicators of ventricular function remained depressed. CONCLUSIONS: Myocardial substrate oxidation was preserved after 3 hours of WCBCP, although ventricular function was moderately impaired. Thus, WCBCP with a seemingly normal substrate and oxygen supply was associated with a reduced cardiac efficiency.

Protein S-100beta: a biochemical marker for increased intracranial pressure in pigs with acute hepatic failure.

BACKGROUND: Acute hepatic failure (AHF) may cause encephalopathy. Intracranial pressure (ICP) is frequently monitored to guide therapy, but such monitoring may cause intracerebral haemorrhagic complications. We hypothesize that determination of serum levels of S-100beta, a protein synthesized in astroglial cells, will provide useful clinical information on the presence and extent of intracranial hypertension in AHF. METHODS: Continuous intraparenchymatous ICP monitoring and serial S-100beta measurements in serum were performed in 11 Norwegian Landrace pigs with surgically induced AHF and in 4 sham-operated controls. RESULTS: ICP increased hour by hour in the devascularized pigs in parallel with increased serum levels of protein S-100beta. In the sham-operated controls S-100beta was not detectable at any time point. CONCLUSIONS: Serum levels of S-100beta are increased early in experimental AHF. Determination of protein S-100beta may provide useful information on the presence and extent of intracranial hypertension in AHF.

Oxygen-wasting effect of inotropy in the "virtual work model".

In the "virtual work model," left ventricular total mechanical energy (TME) is linearly related to myocardial oxygen consumption (MVO2). This relationship (MVO2-TME) is supposedly independent of inotropic stimulation, vascular loading, and heart rate variations. We reexamined the effect of inotropic stimulation (dopamine) on the metabolic to mechanical energy transfer in nine open-chest anesthetized pigs. Left ventricular mechanical energy was calculated using TME (mean ejection pressure x end-diastolic volume + stroke work), TMEW (end-diastolic volume reduced by unstressed ventricular volume), and the pressure-volume area (PVA). A highly linear relationship between MVO2 and mechanical energy was found for all three indexes during control and dopamine runs (r = 0.87-0.99). The slopes were unaltered by dopamine. y-Axis intercepts were (control vs. dopamine) as follows (in J. beat-1. 100 mg-1; means +/- SD): TME, 0.36 +/- 0.12 vs. 0.61 +/- 0.30 (P < 0.02); TMEW, 0.43 +/- 0.16 vs. 0.72 +/- 0.32 (P < 0.02); and PVA, 0.34 +/- 0.13 vs. 0.60 +/- 0.30 (P < 0.02). We conclude that the virtual work model is dependent on inotropic stimulation and that new insight into myocardial chemomechanical coupling is not added by this concept.

The influence of growth hormone on tumour necrosis factor and neutrophil leukocyte function in sepsis.

The aim of this study was to assess the influence of growth hormone (GH) in sepsis on the immune system represented by the circulating TNF-levels and the neutrophil leukocytes phagocytic capacity and respiratory burst, 22 piglets were randomized to 3 groups; pretreatment with GH (16 i.u.) before sepsis (n = 8), non-treated septic controls (n = 8), and non-septic controls (n = 6). Sepsis was induced by a standardized infusion of live E. coli. TNF was measured by a cytotoxic bioassay, while neutrophil function tests were carried out by flowcytometric assays. In brief, phagocytosis was evaluated by the neutrophils' ability to ingest FITC-labelled (fluorescein isothiocyanate) E. coli and intracellular release of oxygen metabolites was detected by the oxidation of 2',7'-dichlorofluorescin (DCFH) to the fluorescent 2',7'-dichlorofluorescein (DCF). Our data show a suppression of phagocytosis in the GH-treated group before sepsis; however, when challenged with Gram-negative bacteria, the phagocytic capacity was similar to that of the non-treated animals. The serum levels of TNF in the non-treated septic control group were twice the levels of those in the GH-treated group, 65.7 pg/ml (septic controls) vs 32.8 pg/ml (GH). Pretreatment with a single dose of GH few hours prior to sepsis does not seem to entail any further imbalance of the neutrophil function in sepsis. Lowering of the circulating TNF-levels is a presumptive favourable effect of GH in sepsis.

Lactate and pyruvate concentrations in capillary blood from newborns.

Using high pressure liquid chromatography on strong cation exchange column, we analyzed capillary blood from 141 healthy full-term newborns for lactate and pyruvate concentrations. Total range of lactate was 367-3245 mumol/l and reference interval (mean +/- 2 SD) was 260-2212 mumol/l. Total range of pyruvate was 10-141 mumol/l and reference interval (10th/90th percentile) was 12-71 mumol/l.