Assessment of the agreement between photoplethysmographic and arterial waveform respiratory variation in patients undergoing spine surgery

Respiratory variation in the arterial blood pressure and photoplethysmographic (PPG) waveforms have both been shown to predict the haemodynamic response to volume administration. Whether or not the two can be considered interchangeable is controversial. Twenty-three patients undergoing spine surgery received both a 20 gauge intra-arterial catheter and a Masimo adult adhesive SpHb sensor connected to a Radical-7 monitor. Pulse pressure variation (PPV) was calculated off-line at 1-min intervals. Pleth Variability Index (PVI) and Perfusion Index data were recorded. After exclusion of outliers, agreement between PPV and PVI was assessed using a repeated measures Bland-Altman approach. Concordance between changes in PPV and PVI was assessed using a four-quadrant plot with a 20% zone of exclusion. In total, 6549 min of data were collected. Repeated measures Bland-Altman analysis identified a bias of 2.2% and 95% confidence intervals of ±15.3% (limits of agreement -13.1 and +17.6%). The concordance rate between changes in PPV and changes in PVI was 51%. The agreement between respiratory variation in the arterial blood pressure and PPG waveforms is poor and these two should not be considered interchangeable. Changes in PPV are unrelated to changes in PVI. The data, combined with recently published work from other authors, suggests that the low frequency oscillations in the PPG waveform are not related to the low frequency oscillation in the systemic arterial blood pressure tracing and may be related to changes in venous pressure, peripheral tone or other physiologic phenomena yet to be described.

The pharmacokinetics of methadone in adolescents undergoing posterior spinal fusion

BACKGROUND

The optimal methadone dosing regimen for children undergoing spinal surgery is uncertain because of sparse pediatric pharmacokinetic data and a paucity of analgesic effect data. The minimum effective analgesic concentration of methadone in opioid naïve adults is 58 mcg · L(-1).

METHODS

Adolescents aged 12-19 years undergoing idiopathic scoliosis correction were administered 0.25 mg · kg(-1) racemic methadone IV prior to surgical incision. Arterial blood samples for methadone assay were obtained at 0 min, 5 min, 10 min, 15 min, 20 min, 40 min, 1 h, 2 h, 4 h, 5 h, 6 h, 8 h, 10 h, 12 h, 24 h, and 48 h. Compartment analysis was undertaken using nonlinear mixed effects models. Parameter estimates were standardized to a 70-kg person using allometric models.

RESULTS

A three-compartment linear disposition model best described observed time-concentration profiles. Population parameter estimates (between-subjects variability) were central volume (V1) 19.1 (126%) L 70 kg(-1), peripheral volumes of distribution V2 65.5 (60%) L 70 kg(-1), V3 485 (23%) L 70 kg(-1), clearance (CL) 9.3 (11%) L · h(-1) · 70 kg(-1), and inter-compartment clearances Q2 282 (95%) L · h(-1) 70 kg(-1), Q3 139 (42%) L · h(-1) 70 kg(-1). The terminal elimination half-life was 44.4 h. The mean observed methadone concentration was <58 mcg · L(-1) by the first hour after administration.

CONCLUSIONS

Current pharmacokinetic parameter estimates in adolescents are similar to those reported in adults. Methadone undergoes rapid redistribution after bolus administration. This may result in plasma concentrations that provide inadequate analgesia postoperatively. We would suggest following the bolus (0.25 mg.kg(-1)) with an infusion (0.1-0.15 mg · kg(-1) · h(-1) for 4 h) during spinal surgery to ensure adequate plasma concentrations for 24 h.

Non-invasive estimation of jugular venous oxygen saturation: a comparison between near infrared spectroscopy and transcutaneous venous oximetry

The ability of practitioners to assess the adequacy of global oxygen delivery is dependent on an accurate measurement of central venous saturation. Traditional techniques require the placement of invasive central venous access devices. This study aimed to compare two non-invasive technologies for the estimation of regional venous saturation (reflectance plethysmography and near infrared spectroscopy [NIRS]), using venous blood gas analysis as gold standard. Forty patients undergoing cardiac surgery were recruited in two groups. In the first group a reflectance pulse oximeter probe was placed on the skin overlying the internal jugular vein. In the second group, a Somanetics INVOS oximeter patch was placed on the skin overlying the internal jugular vein and overlying the ipsilateral cerebral hemisphere. Central venous catheters were placed in all patients. Oxygen saturation estimates from both groups were compared with measured saturation from venous blood. Twenty patients participated in each group.Data were analyzed by the limits of agreement technique suggested by Bland and Altman and by linear regression analysis. In the reflectance plethysmography group, the mean bias was 4.27% and the limits of agreement were 58.3 to -49.8% (r(2) = 0.00, p = 0.98). In the NIRS group the mean biases were 10.8% and 2.0% for the sensors attached over the cerebral hemisphere and over the internal jugular vein, respectively, and the limits of agreement were 33.1 to -11.4 and 19.5 to -15.5% (r(2) = 0.22, 0.28;p = 0.04, 0.03) for the cerebral hemisphere and internal jugular sites, respectively. While transcutaneous regional oximetry and NIRS have both been used to estimate venous and tissue oxygen saturation non-invasively, the correlation between estimates of ScvO(2) and SxvO(2) were statistically significant for near infrared spectroscopy, but not for transcutaneous regional oximetry. Placement of cerebral oximetry patches directly over the internal jugular vein (as opposed to on the forehead) appeared to approximate internal jugular venous saturation better (lower mean bias and tighter limits of agreement), which suggests this modality may with refinement offer the practitioner additional clinically useful information regarding global cerebral oxygen supply and demand matching.

The ability of anesthesia providers to visually estimate systolic pressure variability using the "eyeball" technique

BACKGROUND

Systemic arterial respiratory variation has been shown to be a reliable predictor of changes in cardiac output after fluid administration. Arterial respiratory variation is often estimated from visual examination of the arterial waveform tracing. Our goal in this study was to assess the ability of anesthesia providers to visually estimate systolic pressure variation (SPV) as a percentage of systolic blood pressure (SPV).

METHODS

Fifty anesthesia providers were recruited and asked to visually examine 10 recorded arterial waveform tracings (played in real time), to estimate SPV, and to state whether or not a fluid bolus was indicated. After completion of the examination, the participants were shown the original tracings, the true value for SPV, and their estimate. The percentage of incorrect physician decisions to administer or not administer additional fluid was analyzed using a binomial proportion confidence interval. Clinical utility was also assessed using clinical significance analysis. Limits of agreement were analyzed using the nonparametric approach recommended by Bland and Altman.

RESULTS

The mean bias was +1.2%. The nonparametric limits of agreement were -5.1 and 7.5%, and contained 82% of values. Actual physician decisions were incorrect 4.4% of the time (95% confidence interval [CI] 2.8% to 6.6%). On the basis of the clinical significance analysis, only 1% of treatments based on the visual estimation would have been incorrect.

CONCLUSION

Visual estimates of respiratory variation are within clinically reasonable limits 82% of the time and lead to erroneous management decisions in 4.4% of measurements.

Ketamine induces apoptosis via the mitochondrial pathway in human lymphocytes and neuronal cells

BACKGROUND

Ketamine has been shown to have neurotoxic properties, when administered neuraxially. The mechanism of this local toxicity is still unknown. Therefore, we investigated the mechanism of cytotoxicity in different human cell lines in vitro.

METHODS

We incubated the following cell types for 24 h with increasing concentrations of S(+)-ketamine and racemic ketamine: (i) human Jurkat T-lymphoma cells overexpressing the antiapoptotic B-cell lymphoma 2 protein, (ii) cells deficient of caspase-9, caspase-8, or Fas-associated protein with death domain and parental cells, and (iii) neuroblastoma cells (SHEP). N-Methyl-d-aspartate (NMDA) receptors and caspase-3 cleavage were identified by immunoblotting. Cell viability and apoptotic cell death were evaluated flowcytometrically by Annexin V and 7-aminoactinomycin D double staining. Mitochondrial metabolic activity and caspase-3 activation were measured.

RESULTS

Ketamine, in a concentration-dependent manner, induced apoptosis in lymphocytes and neuroblastoma cell lines. Cell lines with alterations of the mitochondrial pathway of apoptosis were protected against ketamine-induced apoptosis, whereas alterations of the death receptor pathway did not reduce apoptosis. S(+)-Ketamine and racemic ketamine induced the same percentage of cell death in Jurkat cells, whereas in neuroblastoma cells, S(+)-ketamine was slightly less toxic.

CONCLUSIONS

Ketamine at millimolar concentrations induces apoptosis via the mitochondrial pathway, independent of death receptor signalling. At higher concentrations necrosis is the predominant mechanism. Less toxicity of S(+)-ketamine was observed in neuroblastoma cells, but this difference was minor and therefore unlikely to be mediated via the NMDA receptor.

Review article: the role of the perioperative period in recurrence after cancer surgery

A wealth of basic science data supports the hypothesis that the surgical stress response increases the likelihood of cancer dissemination and metastasis during and after cancer surgery. Anesthetic management of the cancer patient, therefore, could potentially influence long-term outcome. Preclinical data suggest that beneficial approaches might include selection of induction drugs such as propofol, minimizing the use of volatile anesthetics, and coadministration of cyclooxygenase antagonists with systemic opioids. Retrospective clinical trials suggest that the addition of regional anesthesia might decrease recurrence after cancer surgery. Other factors such as blood transfusion, temperature regulation, and statin administration may also affect long-term outcome.

Local anesthetics time-dependently inhibit staphylococcus aureus phagocytosis, oxidative burst and CD11b expression by human neutrophils

BACKGROUND AND OBJECTIVES

Local anesthetics have been shown to modulate neutrophil functions in a time-dependent manner, which might help to prevent inflammatory injury to the organism. However, if host defense mechanisms are affected similarly, the ability to eliminate bacteria might be reduced. We hypothesized that local anesthetics have time-dependent effects on phagocytosis of S. aureus, oxidative burst, and CD11b expression by human neutrophils. To test this hypothesis, we reanalyzed data from a previous study.

METHODS

Blood samples from 11 healthy volunteers were incubated with lidocaine (1,846 mumol/L), bupivacaine (770 mumol/L) or ropivacaine (801 mumol/L) for 30 minutes. Thereafter, bacteria were added, either fluorescently labeled for determination of phagocytosis, or unstained for determination of oxidative burst and CD11b expression. After an additional incubation for 0, 10, 30, or 60 minutes, phagocytosis was stopped and neutrophils were stained with monoclonal antibodies for flow cytometric analysis. Data were analyzed by analysis of variance for repeated measurements.

RESULTS

Lidocaine and bupivacaine inhibited neutrophil functions in a time-dependent manner (P < .05). Prolonged local anesthetic exposure reduced the fraction of ingesting neutrophils by 20% +/- 12% (mean +/- SD) and 7% +/- 7%, bacterial uptake by 19% +/- 16% and 14% +/- 12%, oxidative burst by 29% +/- 23% and 28% +/- 25%, and CD11b expression by 66% +/- 24% and 25% +/- 21% for lidocaine and bupivacaine, respectively. Ropivacaine exerted a time-dependent effect on CD11b expression only (24% +/- 34%; P < .05).

CONCLUSIONS

Our results indicate that in a whole blood model, time-dependent effects of local anesthetics affect key neutrophil functions necessary for bacterial elimination. However, these effects only occur at concentrations that are unlikely to be routinely attained in the clinical setting, and concern about interfering with the host defense is likely unwarranted.

Systemic lidocaine shortens length of hospital stay after colorectal surgery: a double-blinded, randomized, placebo-controlled trial

OBJECTIVE

To characterize the beneficial effects of perioperative systemic lidocaine on length of hospital stay, gastrointestinal motility, and the inflammatory response after colorectal surgery.

SUMMARY BACKGROUND DATA

Surgery-induced stimulation of the inflammatory response plays a major role in the development of several postoperative disorders. Local anesthetics possess anti-inflammatory activity and are thought to positively affect patients' outcome after surgery. This double-blinded, randomized, and placebo-controlled trial aimed to evaluate beneficial effects of systemic lidocaine and to provide insights into underlying mechanisms.

METHODS

Sixty patients undergoing colorectal surgery, not willing or unable to receive an epidural catheter, were randomly assigned to lidocaine or placebo treatment. Before induction of general anesthesia, an intravenous lidocaine bolus (1.5 mg/kg) was administered followed by a continuous lidocaine infusion (2 mg/min) until 4 hours postoperatively. Length of hospital stay, gastrointestinal motility, and pain scores were recorded and plasma levels or expression of pro- and anti-inflammatory mediators determined.

RESULTS

Lidocaine significantly accelerated return of bowel function and shortened length of hospital stay by one day. No difference could be observed in daily pain ratings. Elevated plasma levels of IL-6, IL-8, complement C3a, and IL-1ra as well as expression of CD11b, L- and P-selectin, and platelet-leukocyte aggregates were significantly attenuated by systemic lidocaine.

CONCLUSIONS

Perioperative intravenous lidocaine not only improved gastrointestinal motility but also shortened length of hospital stay significantly. Anti-inflammatory activity modulating the surgery-induced stress response may be one potential mechanism. Systemic lidocaine may thus provide a convenient and inexpensive approach to improve outcome for patients not suitable for epidural anesthesia.

Novel local anaesthetics and novel indications for local anaesthetics

Research into local anaesthetic mechanisms over the past few years has focused on two main issues. First, attention has focused on development of compounds with fewer side effects, better sensory/motor separation and longer duration of action; this has resulted in the introduction of ropivacaine and levobupivacaine into clinical practice. These agents have a lesser cardiotoxic effect than older compounds, and ropivacaine may in addition offer better sensory/motor separation. Several other compounds, including tonicaine and sameridine, are under investigation. In addition, the local anaesthetic properties of amitryptiline are being studied, and liposome encapsulation of local anaesthetics appears able to confer new pharmacokinetic properties on common drugs. Second, the molecular basis for several local anaesthetic actions that are not mediated by sodium channels has become a topic of interest. The mechanisms that underlie anti-inflammatory and antithrombotic actions are at present being unravelled. How local anaesthetics potentiate antitumour agents, protect neuronal tissue and prevent bronchial reactivity is less clear, but the potential clinical benefits of these effects deserve further exploration.

Intravenous lidocaine infusion facilitates acute rehabilitation after laparoscopic colectomy

BACKGROUND

Intravenous infusion of lidocaine decreases postoperative pain and speeds the return of bowel function. The authors therefore tested the hypothesis that perioperative lidocaine infusion facilitates acute rehabilitation protocol in patients undergoing laparoscopic colectomy.

METHODS

Forty patients scheduled to undergo laparoscopic colectomy were randomly allocated to receive intravenous lidocaine (bolus injection of 1.5 mg/kg lidocaine at induction of anesthesia, then a continuous infusion of 2 mg.kg.h intraoperatively and 1.33 mg.kg.h for 24 h postoperatively) or an equal volume of saline. All patients received similar intensive postoperative rehabilitation. Postoperative pain scores, opioid consumption, and fatigue scores were measured. Times to first flatus, defecation, and hospital discharge were recorded. Postoperative endocrine (cortisol and catecholamines) and metabolic (leukocytes, C-reactive protein, and glucose) responses were measured for 48 h. Data (presented as median [25-75% interquartile range], lidocaine vs. saline groups) were analyzed using Mann-Whitney tests. P<0.05 was considered statistically significant.

RESULTS

Patient demographics were similar in the two groups. Times to first flatus (17 [11-24] vs. 28 [25-33] h; P<0.001), defecation (28 [24-37] vs. 51 [41-70] h; P=0.001), and hospital discharge (2 [2-3] vs. 3 [3-4] days; P=0.001) were significantly shorter in patients who received lidocaine. Lidocaine significantly reduced opioid consumption (8 [5-18] vs. 22 [14-36] mg; P=0.005) and postoperative pain and fatigue scores. In contrast, endocrine and metabolic responses were similar in the two groups.

CONCLUSIONS

Intravenous lidocaine improves postoperative analgesia, fatigue, and bowel function after laparoscopic colectomy. These benefits are associated with a significant reduction in hospital stay.

Pharmacologic modulation of operative risk in patients who have cardiac disease

Cardiac complications continue to compose a major proportion of serious postoperative morbidity and mortality, and it is appropriate, therefore, that this area has received a lot of attention in the search for pharmacologic modulation of surgical outcomes. Despite numerous studies, conclusive data does not exist, making it difficult to recommend a course of action. beta-blockade has not only made it into national protocols, but is even considered as a quality assessment measure. However, the data are not quite as conclusive as it may sometimes appear. There have been few studies, with a small number of negative outcomes, and, at times, significant methodological concerns. The positive outcomes of meta-analyses rest essentially on a single trial in a highly selected patient population. Although use of beta-blockers in patients who have documented coronary artery disease and are undergoing major vascular procedures appears supported, it is premature to recommend beta-blockade for all patients with cardiac risk. Because these drugs are not without risks, it might be advisable to be restrained in their use until the results of the large-scale randomized POISE trial are available. For clonidine and statins, the data are even more tenuous, and largely based on retrospective reviews (with the exception of postprocedure use of statins, which is well supported). Here again, the results of large-scale prospective trials must become available before recommendations can be made. Finally, promising data indicate that it might be possible to modulate by pharmacologic means the neurocognitive decline that is frequently associated with cardiac surgery, and which is often considered by patients to be the most troublesome complication of the intervention.

The role of the dorsal root ganglion in cervical radicular pain: diagnosis, pathophysiology, and rationale for treatment

Cervical radicular pain affects 83 per 100,000 adults annually. Diagnosis by means of physical examination, imaging, and electrophysiological studies is characterized by high specificity but low sensitivity. In this review, we focus on the role of the dorsal root ganglion and those treatment modalities that aim at pathophysiological mechanisms occurring after injury to the dorsal root ganglion. Cervical nerve injury initiates multiple events that lead to changes in nerve function and result in spontaneous firing at the dorsal root ganglion. Among these, inflammation and changes in ion-channel function play a pivotal role. Although many treatment modalities are described in the literature, the available evidence for efficacy does not allow us to formulate definitive conclusions on the optimal therapy. A lack of evidence is reported for cervical spine surgery. Interlaminar epidural steroid administration and radiofrequency techniques adjacent to the cervical dorsal root ganglion have the highest, but still weak recommendations.

The Role of Sodium Channels in Chronic Inflammatory and Neuropathic Pain

Clinical and experimental data indicate that changes in the expression of voltage-gated sodium channels play a key role in the pathogenesis of neuropathic pain and that drugs that block these channels are potentially therapeutic. Clinical and experimental data also suggest that changes in voltage-gated sodium channels may play a role in inflammatory pain, and here too sodium-channel blockers may have therapeutic potential. The sodium-channel blockers of interest include local anesthetics, used at doses far below those that block nerve impulse propagation, and tricyclic antidepressants, whose analgesic effects may at least partly be due to blockade of sodium channels. Recent data show that local anesthetics may have pain-relieving actions via targets other than sodium channels, including neuronal G protein-coupled receptors and binding sites on immune cells. Some of these actions occur with nanomolar drug concentrations, and some are detected only with relatively long-term drug exposure. There are 9 isoforms of the voltage-gated sodium channel alpha-subunit, and several of the isoforms that are implicated in neuropathic and inflammatory pain states are expressed by somatosensory primary afferent neurons but not by skeletal or cardiovascular muscle. This restricted expression raises the possibility that isoform-specific drugs might be analgesic and lacking the cardiotoxicity and neurotoxicity that limit the use of current sodium-channel blockers.

PERSPECTIVE

Changes in the expression of neuronal voltage-gated sodium channels may play a key role in the pathogenesis of both chronic neuropathic and chronic inflammatory pain conditions. Drugs that block these channels may have therapeutic efficacy with doses that are far below those that impair nerve impulse propagation or cardiovascular function.

Revision total knee arthroplasty does not increase PACU utilization

The hospital records of 232 consecutive cases of patients undergoing primary and revision total knee arthroplasty were analyzed to determine differences in operating room time, postanesthesia care unit time, operating room narcotic usage, and postanesthesia care unit narcotic usage between the two groups. The average operating room time for a surgeon performing revision total knee arthroplasty on a patient was greater than that for a primary total knee arthroplasty. However, there was no difference in average postanesthesia care unit time nor operating room and postanesthesia care unit narcotic usage. When stratified to anesthetic type and perioperative pain intervention, there was no difference in any of the measured parameters between the primary and revision groups. Thus, even with longer operating times, a patient undergoing revision total knee arthroplasty did not utilize more postanesthesia care unit time, nor more perioperative narcotics, than a patient undergoing primary total knee arthroplasty.

LEVEL OF EVIDENCE

Therapeutic study, Level III (retrospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.

Sublingual Piroxicam for Postoperative Analgesia: Preoperative Versus Postoperative Administration: A Randomized, Double-Blind Study

Nonsteroidal antiinflammatory drugs have been used to obtain preemptive analgesia. We investigated, in this randomized, double-blind study, whether sublingual (s.l.) piroxicam given before was more effective than that given after surgery. Fifty-two patients scheduled for laparoscopic bilateral inguinal hernia repair under general anesthesia were enrolled. Group PRE (25 patients) received 40 mg of piroxicam s.l. 2 h before surgery and a placebo 10 min after surgery. Group POST (27 patients) were treated with a placebo 2 h before surgery and received 40 mg of piroxicam s.l. 10 min after surgery. After an initial dose of 100 mg tramadol IV, patient-controlled analgesia with tramadol was started and recorded. Visual analog scores were assessed in the recovery and at 6, 20, and 30 h postoperatively. Significantly lower visual analog scores were found in group PRE at 6 and 20 h. Significantly smaller cumulative tramadol consumption was observed after 30 h in group PRE. In summary, our findings suggest that preoperative s.l. piroxicam is more effective than the postoperative administration. Because of the low pain scores in both groups, the clinical relevance of these findings is not clear from this study.

Local anaesthetics inhibit signalling of human NMDA receptors recombinantly expressed in Xenopus laevis oocytes: role of protein kinase C

BACKGROUND

N-methyl-D-aspartate (NMDA)-receptor activation contributes to postoperative hyperalgesia. Studies in volunteers have shown that intravenous local anaesthetics (LAs) prevent the development of hyperalgesic pain states. One potential explanation for this beneficial effect is the inhibition of NMDA receptor activation. Therefore, we studied the effects of LA on NMDA receptor function.

METHODS

The human NR1A/NR2A NMDA receptor was expressed recombinantly in Xenopus laevis oocytes. Peak currents were measured by voltage clamp in Mg- and Ca2+-free, Ba2+-containing Tyrode's solution. Holding potential was -70 mV. Oocytes were stimulated with glutamate/glycine (at EC50) with or without 10 min prior incubation in bupivacaine, levobupivacaine, S-(-)-ropivacaine, or lidocaine (all at 10(-9)-10(-4) M), procaine (10(-4) M), R-(+)-ropivacaine (10(-4) M), QX314 (permanently charged, 5 x 10(-4) M) extracellularly or intracellularly or benzocaine (permanently uncharged, 5 x 10(-3) M). We also determined the effect of the protein kinase C (PKC) inhibitors chelerythrine (5 x 10(-5) M), calphostin C (3 x 10(-6) M) and Ro 31-8220 (10(-7) M), and the effect of PKC activation with phorbolester (10(-6) M).

RESULTS

Non-injected oocytes were unresponsive to agonist application, but oocytes expressing NMDA receptors responded with inward currents (1.1+/-0.08 microA). All LA concentration-dependently inhibited agonist responses. The inhibition was reversible and stereoselective. Intracellular QX314 reduced responses to 59% of control, but extracellular QX314 was without effect. Benzocaine reduced responses to 33% of control. PKC inhibitors had no additional inhibitory effect beyond that of bupivacaine. The effect of PKC activation was abolished in the presence of bupivacaine.

CONCLUSION

All LA tested inhibited the activation of human NMDA receptors in a concentration dependent fashion. This effect may contribute to reduced hyperalgesia and opiate tolerance observed after systemic administration of LA. The effect is independent of the charge of LA; site of action is intracellular. The mechanism of action may be mediated by inhibition of PKC.

Effects of cafedrine/theodrenaline, etilefrine and ephedrine on uterine blood flow during epidural-induced hypotension in pregnant sheep

INTRODUCTION

Maternal hypotension is a major concern in obstetric anesthesia, and concerns have been raised about standard vasopressor therapy with ephedrine. Therefore, we evaluated the maternal and fetal hemodynamic effects of two potential alternatives to ephedrine.

METHODS

Hypotension was induced by epidural administration of lidocaine in 6 chronically instrumented pregnant ewes (at 118-122 days of gestation, term 145 days). Three treatments were studied: 25 mg ephedrine, 5 mg etilefrine and 100 mg cafedrine/5 mg theodrenaline (C/T) intravenously. Mean fetal and maternal blood pressure and heart rate, uterine blood flow, as well as fetal and maternal arterial blood gases were recorded for 60 min.

RESULTS

All three vasopressors increased maternal blood pressure, accompanied by a significant increase in uterine blood flow. C/T caused marked maternal tachycardia, whereas ephedrine decreased maternal heart rate. Maternal and fetal blood gases did not change during any of the three treatment regimens.

CONCLUSION

All three vasopressors restored maternal blood pressure and uterine blood flow after epidurally induced maternal hypotension. However, restoration of uterine perfusion was delayed and less pronounced with C/T.

Receptors, G Proteins, and Their Interactions

Membrane receptors coupling to intracellular G proteins (G protein-coupled receptors) form one of the major classes of membrane signaling proteins. They are of great importance to the practice of anesthesiology because they are involved in many systems of relevance to the specialty (cardiovascular and respiratory control, pain transmission, and others) and many drugs target these systems. In recent years, understanding of these signaling systems has grown. The structure of receptors and G proteins has been elucidated in more detail, their regulation is better understood, and the complexity of interactions between the various parts of the system (receptors, G proteins, effectors, and regulatory molecules) has become clear. These findings may help explain both actions and side effects of drugs. In addition, these newly discovered targets are likely to play important roles in disease states of relevance to anesthesiologists.

Revising a Dogma: Ketamine for Patients with Neurological Injury?

We evaluated reports of randomized clinical trials in the perioperative and intensive care setting concerning ketamine's effects on the brain in patients with, or at risk for, neurological injury. We also reviewed other studies in humans on the drug's effects on the brain, and reports that examined ketamine in experimental brain injury. In the clinical setting, level II evidence indicates that ketamine does not increase intracranial pressure when used under conditions of controlled ventilation, coadministration of a gamma-aminobutyric acid (GABA) receptor agonist, and without nitrous oxide. Ketamine may thus safely be used in neurologically impaired patients. Compared with other anesthetics or sedatives, level II and III evidence indicates that hemodynamic stimulation induced by ketamine may improve cerebral perfusion; this could make the drug a preferred choice in sedative regimes after brain injury. In the laboratory, ketamine has neuroprotective, and S(+)-ketamine additional neuroregenerative effects, even when administered after onset of a cerebral insult. However, improved outcomes were only reported in studies with brief recovery observation intervals. In developing animals, and in certain brain areas of adult rats without cerebral injury, neurotoxic effects were noted after large-dose ketamine. These were prevented by coadministration of GABA receptor agonists.

IMPLICATIONS

Ketamine can be used safely in neurologically impaired patients under conditions of controlled ventilation, coadministration of a {gamma}-aminobutyric acid receptor agonist, and avoidance of nitrous oxide. Its beneficial circulatory effects and preclinical data demonstrating neuroprotection merit further animal and patient investigation.

Perioperative Blood Transfusions and Delayed Wound Healing After Hip Replacement Surgery: Effects on Duration of Hospitalization

Patients who receive allogeneic blood transfusions after orthopedic surgery have a longer duration of hospitalization, and this cannot be explained by a more frequent incidence of infections in transfused patients. To determine whether transfusion of allogeneic blood interferes with wound healing and therefore increases the duration of hospitalization, we performed an observational study in 444 consecutive patients scheduled for elective primary hip surgery. Transfusion, wound, and infection variables were collected at five time points during treatment. Of the 444 consecutive patients studied, 92 received blood transfusions during their perioperative course. Thirty-one percent of transfused patients developed wound-healing disturbances versus 18% of the nontransfused group (P < 0.05); allogeneic blood transfusion was the only significant predictor for development of minor wound-healing disturbances. Duration of hospitalization was prolonged in transfused patients (12.3 versus 9.8 days) and could be predicted by 4 significant variables: requirement for blood transfusion (adds 2.7 +/- 0.5 days), presence of wound-healing disturbances (adds 1.3 +/- 0.5 days), duration of surgery (adds 0.2 +/- 0.1 days/10 min), and patient's age (adds 0.9 +/- 0.2 days/10 yr). These data suggest that allogeneic blood transfusion is associated with an increased incidence of wound-healing disturbances and that prevention of allogeneic blood transfusion may be relevant in limiting the duration of admission after elective orthopedic surgery.

Epidural Local Anesthetics: A Novel Treatment for Fetal Growth Retardation?

BACKGROUND

Chronically compromised uterine perfusion may lead to placental insufficiency and subsequent intrauterine growth restriction (IUGR). Various therapeutic approaches (e.g. vasodilators, low-dose aspirin, intravenous glucose infusion, and hemodilution) are often of limited efficacy. Local anesthetics have been shown to improve placental blood flow in pre-eclamptic women. We hypothesized that epidural administration of local anesthetics might improve outcome in IUGR independent of the underlying cause. In preparation for a clinical trial to test this hypothesis, we performed a pilot study in 10 patients.

METHODS

After approval of the study protocol, 10 pregnant women presenting with oligohydramnios and IUGR were included in the study. In addition to our standard protocol (magnesium, glucose, betamethasone), each patient received an epidural catheter (T10/T12) with continuous infusion of bupivacaine 0.175% at a rate of 5 ml/h. Uteroplacental circulation was monitored by Doppler sonography and the amount of amniotic fluid was estimated daily.

RESULTS

Epidural insertion and infusion was performed without complications. Four patients continued to deteriorate rapidly, amniotic fluid volume did not change and uterine artery pulsatility index (PI) tended to increase. In the remaining 6 patients the clinical status stabilized, amniotic fluid volume tended to increase and uterine artery PI tended to decrease during treatment. This improvement was associated with a prolonged interval to cesarean section and increased infant birth weight.

CONCLUSION

Our data suggest that, even if the underlying cause of IUGR is not pre-eclampsia, epidural local anesthetic administration might improve placental blood flow and be beneficial in a subgroup of patients. A clinical trial to test this hypothesis appears warranted.

Clinical Pharmacology of Local Anesthetics

Whereas currently available local anesthetics may be suitable for intraoperative and in-hospital postoperative use, long-acting analgesia after outpatient procedures will require new techniques and drugs. Catheter delivery systems are rapidly gaining clinical acceptance and allow for great flexibility in dosing. Encapsulated local anesthetics can provide the slow release of drugs. Novel, long-acting local anesthetics are being investigated but are not yet ready for clinical use. In addition to the effects on the sodium channel, other actions of these novel compounds need to be explored, because both beneficial and detrimental effects may be induced with these compounds.

Clinical efficacy of postoperative autologous transfusion of filtered shed blood in hip and knee arthroplasty

BACKGROUND

Total knee arthroplasty (TKA) or total hip arthroplasty (THA) regularly results in postoperative requirement of blood transfusion. Because of the disadvantages of allogeneic blood transfusion (ABT) such as the risk of transfusion-associated infections, incompatibility-related transfusion fatalities, or immunomodulatory effects, a continuing effort to reduce allogeneic blood transfusion is important. For this purpose, the effect of reinfusion of drain blood, via a postoperative wound drainage and reinfusion system, on the need for allogeneic blood transfusion was evaluated.

STUDY DESIGN AND METHODS

Using a prospective observational quality assessment design, we compared 135 patients scheduled for TKA or THA with a historic group of 96 patients. In the study group the Bellovac ABT autotransfusion system was used. The shed blood was returned either when 500 mL were collected or at most 6 hours after surgery. Compared were the preoperative, postoperative, and discharge hemoglobin, as well as the number of allogeneic blood transfusions.

RESULTS

There were no statistical differences between preoperative, postoperative, and discharge hemoglobin levels. Autologous transfusion reduced the number of patients receiving ABT overall from 35 percent (control) to 22 percent (study). The decrease of allogeneic transfusion requirement was most significant after TKA: from 18 percent to 6 percent (p < 0.001).

CONCLUSION

We conclude that the Bellovac ABT device reduces allogeneic blood transfusions in TKA and THA.