The focus of temperature monitoring with zero-heat-flux technology (3M Bair-Hugger): a clinical study with patients undergoing craniotomy.

In the noninvasive zero-heat-flux (ZHF) method, deep body temperature is brought to the skin surface when an insulated temperature probe with servo-controlled heating on the skin creates a region of ZHF from the core to the skin. The sensor of the commercial Bair-Hugger ZHF device is placed on the forehead. According to the manufacturer, the sensor reaches a depth of 1-2 cm below the skin. In this observational study, the anatomical focus of the Bair-Hugger ZHF sensor was assessed in pre- and postoperative CT or MRI images of 29 patients undergoing elective craniotomy. Assuming the 2-cm depth from the forehead skin surface, the temperature measurement point preoperatively reached the brain cortex in all except one patient. Assuming the 1-cm depth, the preoperative temperature measurement point did not reach the brain parenchyma in any of the patients and was at the cortical surface in two patients. Corresponding results were obtained postoperatively, although either sub-arachnoid fluid or air was observed in all CT/MRI images. Craniotomy did not have a detectable effect on the course of the ZHF temperatures. In Bland-Altman analysis, the agreement of ZHF temperature with the nasopharyngeal temperature was 0.11 (95% confidence interval - 0.54 to 0.75) °C and with the bladder temperature - 0.14 (- 0.81 to 0.52) °C. As conclusions, within the reported range of the Bair-Hugger ZHF measurement depth, the anatomical focus of the sensor cannot be determined. Craniotomy did not have a detectable effect on the course of the ZHF temperatures that showed good agreement with the nasopharyngeal and bladder temperatures.

Effect of Albumin in Combination With Mannitol on Whole-blood Coagulation In Vitro Assessed by Thromboelastometry.

BACKGROUND: Albumin and mannitol may interfere with hemostasis, but their coinfluence is unclear. We aimed to determine the effects of albumin alone and in combination with mannitol or Ringer acetate (RAC) on hemostasis in crossover in vitro study. MATERIALS AND METHODS: From citrated fresh whole blood withdrawn from 10 volunteers, we prepared 2.5, 5, 10, 15, and 20 vol% dilutions of 4% albumin (Alb group). Each sample was thereafter diluted by 15% mannitol (Alb/Man group) or RAC (Alb/RAC group) at a ratio of 9:1. Using thromboelastometry, FibTEM (fibrinogen ROTEM) and ExTEM (extrinsic ROTEM) tests were performed. RESULTS: A 20 vol%, but not 2.5 to 15 vol% dilution of albumin caused a prolonged clot formation time, α-angle decrease, and maximum clot firmness (MCF) weakening compared with undiluted sample (P<0.05). Clot formation time prolonged more in Alb5/Man than in Alb5 and Alb5/RAC dilution (P<0.05). In Alb2.5/Man, Alb10/Man, and Alb15/Man, dilution α-angle was lower than in corresponding Alb/RAC and Alb-group dilutions (P<0.05). In ExTEM, MCF decreased similarly in every dilution of Alb/Man and Alb/RAC compared with Alb group (P<0.05). In FibTEM, MCF decreased more in Alb10/Man than in Alb10/RAC dilution (P<0.05). CONCLUSIONS: In up to 15 vol% dilutions, albumin alone did not impair hemostasis in vitro, but in combination with mannitol or RAC coagulation was disturbed similarly at most concentrations. There was some significant additional effect with mannitol at certain concentrations. Our results indicate that coadministration of mannitol and albumin needs further study in vivo.

Stroke volume-directed administration of hydroxyethyl starch (HES 130/0.4) and Ringer's acetate in prone position during neurosurgery: a randomized controlled trial.

PURPOSE: General anesthesia in the prone position is associated with hypotension. We studied stroke volume (SV)-directed administration of hydroxyethyl starch (HES 130 kDa/0.4) and Ringer's acetate (RAC) in neurosurgical patients operated on in a prone position to determine the volumes required for stable hemodynamics and possible coagulatory effects. METHODS: Thirty elective neurosurgical patients received either HES (n = 15) or RAC (n = 15). Before positioning, SV measured by arterial pressure waveform analysis was maximized by fluid boluses until SV did not increase more than 10 %. SV was maintained by repeated administration of fluid. RAC 3 ml/kg/h was infused in both groups. Thromboelastometry assessed coagulation. Mann­Whitney U test, Wilcoxon signed-rank test, ANOVA on ranks, and a linear mixed model were applied. RESULTS: Comparable hemodynamics were achieved with the mean cumulative (SD) boluses of HES or RAC 240 (51) or 267 (62) ml (P = 0.207) before positioning, 340 (124) or 453 (160) ml (P = 0.039) 30 min after positioning, and 440 (229) or 653 (368) ml at the end of surgery (P = 0.067). The mean dose of basal RAC infusion was 813 (235) and 868 (354) ml (P = 0.620) in the HES and RAC group, respectively. Formation and maximum strength of the fibrin clot were decreased in the HES group. Intraoperative blood loss was comparable between groups (P = 0.861). CONCLUSION: The amount of RAC needed in the prone position was 25 % greater. The cumulative dose of 440 ml HES induced a slight disturbance in fibrin formation and clot strength. We suggest cautious administration of HES during neurosurgery.

Colloid solutions: a clinical update.

Albumin, dextran, gelatin, and hydroxyethyl starch (HES) solutions are colloids that efficiently expand the circulating blood volume. The administration of colloids restores the intravascular volume with minimal risk of tissue edema in comparison with crystalloid solutions alone. However, colloids are always given for surgical and critically ill patients. The type of the colloid, volumes applied, aggressiveness of fluid resuscitation, and the volume status at the initial phase of administration determine their clinical responses. The outcome after fluid resuscitation with various colloids in critically ill patients seems to be comparable according to systematic reviews. A randomized, adequately powered clinical trial comparing modern nonprotein colloid to albumin is still lacking. Rapidly degradable HES solutions have good hemodynamic effects, and the risk of adverse renal and coagulation effects, as well as allergic reactions, is minimal. The current investigation has also shown the beneficial effect of HES solution (especially HES 130/0.4) on inflammatory response, postoperative nausea and vomiting, and postoperative outcome. The indication of colloids with an assessment of the degree of hypovolemia and safety profiles should thus be taken into consideration before colloid administration.

Adenosine-induced cardiac arrest during intraoperative cerebral aneurysm rupture.

BACKGROUND: Rupture of an intracranial aneurysm during surgical clipping may have devastating consequences. Should this happen all methods ought to be considered to stop the bleeding. A short-term cardiac arrest induced by adenosine could be a feasible method to help the surgeon. We present our experiences in the administration of adenosine during an intraoperative aneurysm rupture. METHODS: Medical records of patients who underwent surgical clipping of a cerebral arterial aneurysm were reviewed from 2 university hospitals' operative database in the years 2003 to 2008. Patients were included in this study if adenosine had been administered during intraoperative rupture of an aneurysm. RESULTS: Altogether, 16 of 1014 patients were identified with the use of adenosine during an intraoperative rupture of an aneurysm. All of the patients had sinus rhythm and normotension before the rupture of the aneurysm. Twelve patients were administered a single dose of adenosine and 4 multiple boluses for induction of cardiac arrest; the median (range) total dose was 12 (6-18) mg and 27 (18-87) mg, respectively. The clipping of the aneurysm and the recovery of circulation were uneventful in all cases. In a subgroup analysis according to patient outcome as alive/dead, the pre- and postoperative neurologic condition correlated with the outcome, whereas adenosine did not have any effect on the patient outcome. CONCLUSION: In a case of a sudden aneurysm rupture, adenosine-induced circulatory arrest could be a safe option to facilitate clipping of an aneurysm. However, if adenosine is used, a very close collaboration between the surgeon and the anesthesiologist is required.

Comparison of the effect of 6% hydroxyethyl starch and gelatine on cardiac and stroke volume index: a randomized, controlled trial after cardiac surgery.

BACKGROUND AND AIMS: The objective of this study was to find out the effect of various doses of hydroxyethyl starch (HES), gelatine or Ringer's acetate on cardiac and stroke volume index after cardiac surgery. MATERIAL AND METHODS: Three consecutive boluses (each 7 mL·kg(-1)) of either 6% HES 130/0.4, 4% gelatine, or Ringer's acetate solutions were administered to 45 patients postoperatively. The rate of infusions was adjusted according to haemodynamic measurements. Thereafter, infusion of the study solution (7 mL·kg(-1)) was continued for the following 12 hours. The total dose of study solution was 28 mL·kg(-1). RESULTS AND CONCLUSION: Mean (SD) cardiac and stroke volume indices were greater in the HES group [2.8 L·min(-1)·m(-2) (0.7), 34.1 (6.7) ml·m( -2)] than in the gelatine group [2.2 L·min(-1)·m( -2) (0.6), 25.8 (7.2) ml·m(-2)] after completion of 7 mL·kg(-1) of study solution. At this stage, the effect of gelatine did not differ from Ringer's acetate. After completion of 14 mL·kg(-1) and 21 mL·kg(-1) of colloids, similar cardiac and stroke volume indices were observed and the haemodynamic response was better in both colloid groups than in the Ringer's acetate group. No differences between groups were detected on the first postoperative morning. In the early postoperative phase after cardiac surgery, the effect of a single dose of HES solution on the haemodynamics was superior to the effect of gelatine or Ringer's acetate. However, after repeated administration of the study solutions, the haemodynamics in the two colloid groups appeared to be similar, but superior to the Ringer's acetate group.

Thromboelastometry in patients with severe sepsis and disseminated intravascular coagulation.

Severe sepsis induces coagulopathy, which may lead to disseminated intravascular coagulation (DIC). Thromboelastometry is a point-of-care whole blood coagulation monitor, which has been validated in human endotoxemia model. We assessed thromboelastometry in severe sepsis and overt DIC and investigated its applicability in differentiating sepsis-related coagulation disturbances. Thromboelastometry (EXTEM and FIBTEM tests) and traditional coagulation assays were analyzed in 28 patients with severe sepsis, 12 of who fulfilled the criteria of overt DIC on admission. Ten healthy persons served as controls. Coagulation parameters, clotting time, clot formation time (CFT), alpha angle, maximal clot firmness (MCF) and lysis index at 60 min, were registered. In patients with overt DIC, EXTEM MCF, CFT and alpha angle differed from that in both healthy controls and patients without DIC, indicating hypocoagulation (MCF 52, 63 and 68 mm; CFT 184, 88 and 73 s; and alpha angle 58, 72 and 76 degrees , respectively, P < 0.01 for all). In patients without DIC, the trend was toward hypercoagulation in EXTEM and FIBTEM MCF (68 vs. 63 mm, P = 0.042 and 23 vs. 15 mm, P = 0.034, respectively). Receiver operating characteristic curves showed that MCF, CFT and alpha angle discriminated patients with overt DIC moderately (area under curve 0.891, 0.815 and 0.828, respectively, P < 0.001 for all). Traditional coagulation assays showed progressively worsening coagulopathy from controls to septic patients without DIC and further to those with overt DIC. We conclude that thromboelastometry may be a valuable tool in assessing whole blood coagulation capacity in patients with severe sepsis with and without overt DIC.

Rapidly degradable hydroxyethyl starch solutions impair blood coagulation after cardiac surgery: a prospective randomized trial.

BACKGROUND: There is continuing concern about the effect of hydroxyethyl starch (HES) solutions on blood coagulation. Rapidly degradable HES solutions with more favorable effects on clot strength have therefore been developed. Because the risk of bleeding is increased after cardiopulmonary bypass, we examined whether these types of HES solutions could be administered after cardiac surgery without an alteration of coagulation. METHODS: Two new rapidly degradable HES solutions were compared with human albumin in 45 patients scheduled for elective primary cardiac surgery. After admission to the cardiac surgical intensive care unit, the patients were allocated in random order to receive either 15 mL/kg of HES solution with low molecular weight and low molar substitution (either 6% HES200/0.5 or 6% HES130/0.4) or 4% human albumin solution as a short-time (70-240 min) infusion. RESULTS: Clot formation time was prolonged and maximum clot firmness was decreased in thromboelastometry tracings after infusion of both HES solutions. This impairment in thromboelastometry tracings partly recovered (using InTEM and ExTEM coagulation activators) at 2 h after the completion of the study infusion. Platelet contribution to maximum clot firmness remained unaffected in all of the study groups. HES did not induce fibrinolysis. No changes in thromboelastometry tracings were observed after human albumin infusion. Chest tube drainage was comparable in the study groups. CONCLUSIONS: We conclude that a short-time infusion of rapidly degradable HES solutions after cardiac surgery produces impairment in fibrin formation and clot strength in thromboelastometry tracings. In this clinical setting, human albumin does not impair hemostasis.

An evaluation of the epidural catheter position by epidural nerve stimulation in conjunction with continuous epidural analgesia in adult surgical patients.

BACKGROUND: The epidural stimulation test to confirm epidural catheter position has been described as being simple, fast, and reliable. We evaluated the feasibility of the epidural stimulation test and its potential in contributing to effective postoperative continuous epidural analgesia. METHODS: Thirty adult patients (ASA I-III) undergoing major abdominal surgery or thoracotomy were to receive continuous epidural analgesia at a thoracic level postoperatively. The epidural stimulation test was performed after catheter placement, after local anesthetic boluses, and during epidural analgesia, up to six times in each patient. Catheter positions were verified by epidurography (before start of epidural analgesia and again on the second postoperative day). RESULTS: Several technical issues (e.g., need to flush catheter with saline in order to maintain adequate stimulation during >25% of all measurements) and interpretation problems (e.g., interference of respiratory activity [n = 6]) made the implementation of the epidural stimulation test rather time consuming, both at the time of catheter placement and during epidural analgesia. Immediately after catheter placement (before test dose) the epidural stimulation test did not identify four of four catheters positioned outside the spinal canal. In addition, the initial epidural stimulation test indicated a possible intrathecal or paravertebral placement in 3 of 25 catheters correctly positioned in the epidural space. During 107 of 122 (88%) measurements with the catheter tip situated epidurally and with preceding or simultaneous administration of epidural local anesthetic, the epidural stimulation test elicited a motor response. Continuous epidural analgesia provided adequate pain relief in all 25 patients having positive epidurography. CONCLUSIONS: The epidural stimulation test was often associated with technical difficulties and interpretation problems. The role of the repeated use of the epidural stimulation test for quality assurance in patients undergoing postoperative continuous epidural analgesia remains undetermined.

Patient satisfaction with postoperative pain management--effect of preoperative factors.

Patients often suffer from inadequate treatment of postoperative pain. The purpose of this study was to survey the factors affecting patient satisfaction with postoperative pain management. A questionnaire with 41 items was given on the third postoperative day to 102 patients undergoing major orthopedic or vascular surgery. Intensity of pain was assessed using a 10-cm visual analogue scale (VAS) and given analgesics were recorded. Nurses (n = 74) working on the wards received a questionnaire concerning attitudes toward management of pain. The questionnaires were returned by 75.5% of the patients and 86.3 % of the nurses. Mean VAS on all wards was 2 (scale 0-10). Twenty-eight percent of the patients agreed having hard pain during the day of the operation and 39.3% during the first postoperative night. Eighty percent of the patients were satisfied with pain management, and their satisfaction correlated significantly with received preoperative information (p < .01) and preoperative well-being (p < .01). There is discrepancy between the amount of experienced pain and values of the frequent VAS recordings, which does not seem to be due to the nurses' attitudes toward pain. Preoperative interview is important tool to receive and give information concerning postoperative pain management.

Single-injection brachial plexus anesthesia for arteriovenous fistula surgery of the forearm: a comparison of infraclavicular coracoid and axillary approach.

BACKGROUND AND OBJECTIVES: The surgical site for the creation of an arteriovenous fistula at the lateral aspect of the distal forearm may be faster and more effectively blocked with the infraclavicular coracoid approach than with the axillary approach for brachial plexus block. METHODS: Sixty uremic patients scheduled for the creation of an arteriovenous fistula at the forearm were randomized to receive a single-injection brachial plexus block with 35 to 50 mL mepivacaine 0.95% with epinephrine using the infraclavicular coracoid approach (IC group) or the perivascular axillary approach (AX group). A distal muscular contraction elicited by a nerve stimulator at current <0.5 mA was used in all patients. RESULTS: At 30 and 45 minutes, complete loss of sensation was observed more often in group IC than AX in the cutaneous distribution of musculocutaneous nerve (62% v 30% [P < .05] and 69% v 40%, respectively [P < .05]), but at 60 minutes the difference was not statistically significant. In other areas, analgesia and motor block were achieved at a similar rate. In 3 patients surgery could not be performed under the block due to changes in schedule or the use of a brachial tourniquet. Patient satisfaction was equally high in both groups. CONCLUSIONS: Blockade of the musculocutaneous nerve developed faster with the infraclavicular coracoid approach than with the axillary approach. The infraclavicular coracoid approach may be preferable in patients scheduled for the creation of an arteriovenous fistula at the forearm.

Tranexamic acid does not correct the haemostatic impairment caused by hydroxyethyl starch (200 kDa/0.5) after cardiac surgery.

We investigated the effect of intravenous tranexamic acid on hydroxyethyl starch (HES)-induced clot strength impairment after cardiac surgery. Patients were randomized to receive either 1 g tranexamic acid or the same volume of 0.9% saline after administration of 15 ml/kg of 6% HES (molecular weight, 200 kDa; degree of substitution, 0.5) in the immediate postoperative period. Modified thromboelastometry (ROTEM) using different activators [intrinsic ROTEM (InTEM), extrinsic ROTEM (ExTEM), fibrinogen ROTEM (FibTEM)] was carried out to evaluate clot formation and lysis. The clot formation time was prolonged, and the maximum clot firmness (MCF) and shear elastic modulus [G = 5000 x MCF / (100-MCF), dynes/cm(2)] decreased (all activators of ROTEM) after completion of HES (P < 0.001, two-factor analysis of variance). These abnormalities in blood coagulation persisted despite tranexamic acid. Maximal lysis (FibTEM), indicative of fibrinolytic activity, was increased after HES but no effect of tranexamic acid was observed. The cumulative chest tube drainage until the first postoperative morning was not different between the groups (1008 +/- 251 and 1081 +/- 654 ml, P = 0.698, respectively). We conclude that after cardiopulmonary bypass, HES-induced impairment in clot formation and strength, or increased fibrinolytic capacity, is not reversed by the administration of tranexamic acid.

N-acetylcysteine for the prevention of kidney injury in abdominal aortic surgery: a randomized, double-blind, placebo-controlled trial.

In this prospective, randomized, placebo-controlled, double-blind trial we studied the effects of IV N-acetylcysteine for prevention of renal injury in patients undergoing abdominal aortic surgery. Seventy patients without previously documented renal dysfunction were randomly allocated to receive either N-acetylcysteine (150 mg/kg mixed in 250 mL of 5% dextrose infused in 20 min, followed by an infusion of 150 mg/kg in 250 mL of 5% dextrose over 24 h) or placebo. The infusion was started after the induction of anesthesia. The primary outcome measure was renal injury as measured by the increases in urinary N-acetyl-beta-d-glucosaminidase (NAG)/creatinine ratio (indicator of renal tubular injury) and urinary albumin/creatinine ratio (indicator of glomerular injury). Renal function was assessed by measuring plasma creatinine and serum cystatin C concentrations. The urinary NAG/creatinine ratio increased significantly from baseline to before crossclamp and remained increased on day 5 in both groups. The urinary albumin/creatinine ratio increased significantly from baseline to 6 h after declamping in the N-acetylcysteine group. However, the changes in the NAG/creatinine ratio and the albumin/creatinine ratio were not significantly different between the two groups. Plasma creatinine and serum cystatin C values remained unchanged during the study period in both groups. In conclusion, N-acetylcysteine did not offer any significant protection from renal injury during elective aortic operation in patients with normal preoperative renal function, and some degree of tubular injury seems to occur before aortic crossclamp.

The effect of N-acetylcysteine on blood coagulation and platelet function in patients undergoing open repair of abdominal aortic aneurysm.

N-acetylcysteine (NAC) may offer renal and hepatic protection during surgery, but in experimental studies it has been shown to impair coagulation. Since very little is known about the effects of NAC on blood coagulation in surgical patients, we studied its effects during abdominal aortic reconstruction. NAC (a bolus of 150 mg/kg followed by a continuous 24-h infusion of 150 mg/kg) or the same volume of placebo was given intravenously, in a randomized double-blinded fashion, to 20 patients undergoing abdominal aortic aneurysm repair. The haematocrit, platelet count, prothrombin time, thromboelastometry, and platelet aggregation were studied during and after surgery. Total blood loss was also measured. The median (25th-75th percentiles) decrease of the prothrombin time value was 33.0% (30-37%) after NAC treatment and 6.5% (4-8%) after placebo (P<0.001). Postoperative prothrombin time values remained lower in the patients receiving NAC. In thromboelastometry tracings the coagulation time was more prolonged after the bolus of NAC (P=0.02). Platelet aggregation induced with adenosine diphosphate decreased after NAC but not after placebo. Low prothrombin time values before and after bolus infusions were associated with increased blood loss (P=0.008 and P=0.015, respectively). NAC has anticoagulant and platelet-inhibiting properties in patients undergoing major vascular surgery. This abnormal haemostatic activity should be considered when NAC is administered to patients with increased bleeding risk.

Gelatin and hydroxyethyl starch, but not albumin, impair hemostasis after cardiac surgery.

We investigated the effect of postoperative administration of colloids on hemostasis in 45 patients after cardiac surgery. Patients were randomized to receive 15 mL kg(-1) of either 4% albumin, 4% succinylated gelatin, or 6% hydroxyethyl starch (molecular weight of 200 kDa/degree of substitution 0.5) as a short-term infusion. There was a comparable decrease in maximum clot firmness of thromboelastometry tracings in gelatin and hydroxyethyl starch groups immediately after completion of the infusion, whereas these values remained unchanged in the albumin group. The impairment in clot strength persisted up to 2 h, although the values partly recovered. Postoperative bleeding correlated inversely with the clot strength in pooled data of the artificial colloids. Fibrin formation (clot formation time, alpha-angle) and fibrinogen-dependent clot strength (maximum clot firmness and shear elastic modulus) were more disturbed in the hydroxyethyl starch group than in the gelatin group. We conclude that after cardiopulmonary bypass surgery, both gelatin and hydroxyethyl starch impair clot strength and fibrin buildup, which may predispose patients to increased blood loss. The greatest impairment in hemostasis was seen after hydroxyethyl starch administration, whereas albumin appeared to have the least effect on hemostatic variables.

Dose-dependent inhibition of platelet function by acetaminophen in healthy volunteers.

BACKGROUND: Acetaminophen (paracetamol) is widely used for postoperative analgesia. Its mechanism of action is inhibition of prostaglandin synthesis in the central nervous system, and acetaminophen is traditionally not considered to influence platelet function. The authors studied the dose-dependent inhibition of platelet function by acetaminophen in healthy volunteers. METHODS: Thirteen healthy male volunteers (aged 19-26 yr) were given placebo or 15, 22.5, or 30 mg/kg acetaminophen intravenously in a double-blind, crossover study. Ten and 90 min after infusion, platelet function was assessed by photometric aggregometry and by measuring release of thromboxane B2, analgesia by cold pressor test, and plasma acetaminophen concentrations by high-performance liquid chromatography. RESULTS: When triggered with 500 microm arachidonic acid, median platelet aggregation (area under the curve) was 25.7, 22.8, 4.1, or 3.6 x 10 area units (P < 0.001) 10 min after placebo or 15, 22.5, or 30 mg/kg acetaminophen, respectively. An increasing concentration of arachidonic acid attenuated the antiaggregatory effect. After 90 min, platelet function was recovering. Release of thromboxane B2 was also dose-dependently inhibited by acetaminophen. Although plasma concentration of acetaminophen increased linearly with the dose, no analgesic effect was detected in the cold pressor test. CONCLUSIONS: Acetaminophen, which is a weak inhibitor of platelet cyclooxygenase 1, has a dose-dependent antiaggregatory effect. This property may become clinically significant in patients with intrinsic or drug-induced impairment of hemostasis.