Sensation and Distress of Pain Scales: reliability, validity, and sensitivity

Psychometric properties of the Sensation and Distress of Pain Visual Analogue Scales (VAS) are compared to dual numerical rating scales (NRS) with data from a randomized controlled trial of postoperative patients. On postoperative days 1 and 2, 15-minute test-retest reliability was .73 to .82 for the VAS and slightly lower for the NRS, r = .72 to .78, while convergent validity of the scales ranged from r = .90 to .92; construct validity of sensation and distress ranged from r = .72 to .85; and discriminant validity was lower, r = .65 to .78. Both instruments were significantly associated with pain reduction following treatment, p < .05 to .01. The VAS scores were significantly lower, p < .01 to .001, and more evenly distributed than NRS scores. It is recommended that the VAS be used in research to produce continuous scores that are more suited to parametric analysis.

Nerve blocks in chronic pain therapy--are there any indications left?

Although diagnostic imaging is now highly developed, neural blockade provides another opportunity to test for a source of pain that may frequently leave no signature. Likewise, many neuropathic pains can not be tested by neurodiagnostic methods. This paper makes a case for the continued use of regional anesthesia to assist in the diagnosis and therapy of chronic pain. In particular, the example of autonomic blocks and blocks of the axial spine are emphasized. Nerve blocks require an understanding of the anatomy, physiology, pharmacology, and the ability to interpret critically their results.

Reflex sympathetic dystrophy: a sympathetically mediated pain syndrome or not?

Because of the controversy concerning the manner in which the sympathetic nervous system is involved in reflex sympathetic dystrophy (RSD), its name was changed to one having no mechanistic connotations. This article reviews the relevant literature in support of not only the taxonomical changes to complex regional pain syndrome (CRPS) but also provides evidence of sympathetic dysfunction demonstrated in animal models of neuropathic pain.

Relaxation and music to reduce postsurgical pain

AIMS

We investigated the effects of relaxation, music, and the combination of relaxation and music on postoperative pain, across and between two days and two activities (ambulation and rest) and across ambulation each day. This secondary analysis of a randomized controlled trial was conducted from 1995 to 1997.

BACKGROUND

After surgery, patients do not always receive sufficient relief from opioids and may have undesired side-effects. More complete relief (10-30%) was found recently with adjuvant interventions of relaxation, music, and their combination. Comparison of effects between days and treatments have not been examined longitudinally.

METHODS

With a repeated measures design, abdominal surgery patients (n = 468) in five US hospitals were assigned randomly to one of four groups; relaxation, music, their combination, and control. With institutional approval and written informed consent, subjects were interviewed and taught interventions preoperatively. Postoperative testing was at ambulation and rest on days 1 and 2 using visual analogue (VAS) sensation and distress of pain scales.

RESULTS

Multivariate analysis indicated that although pain decreased by day 2, interventions were not different between days and activities. They were effective for pain across ambulation on each day, across ambulation and across rest over both days (all P < 0.001), and had similar effects by day and by activity.

CONCLUSION

Nurses can safely recommend any of these interventions for pain on both postoperative days and at both ambulation and rest.

Pain outcomes after intestinal surgery

Pain sensation and distress in 38 intestinal surgical patients were moderate to severe on postoperative day 1, ranging from 34 to 49 mm and 33 to 45 mm, respectively, on 100-mm scales. During ambulation, both increased from baseline to post-ambulation, P < 0.01. Half of the patients reported severe pain not relieved by analgesics, and although 44% learned a relaxation technique in the past, only 8% used one for pain after this surgery. Pain disturbed the sleep of 34% of the patients, and pain was related to respiratory, intestinal, febrile, and other complications in 18 (47%) subjects. Attentive analgesic use and nonpharmacologic therapies are recommended.

Pain after gynecologic surgery

This article provides a descriptive profile of pain in 80 women during the first 2 days after gynecologic surgery in 4 hospitals. Surgical procedures included abdominal hysterectomy, oophorectomy, and laparotomy. Average pain was moderate on both days, but paired t tests indicated that pain increased significantly during ambulation on day 1 (P = .009, sensation; P < .001, distress) and on day 2 (P = .007, sensation; P = .030, distress). They both (P = .001) decreased significantly during rest on day 1, but not on day 2. Analysis of quartiles indicated that one fourth of the sample suffered severe sensation pain at all points on day 1 (60 to 74 mm on a 100-mm visual analogue scale), and moderate to severe sensation on day 2 (40 to 60 mm). The lowest quartile had mild pain on both days (11 to 28 mm on day 1, and 7 to 14 mm on day 2). Some patients (30%) reported that pain interrupted their sleep on the first 2 nights, and difficulty sleeping on the first postoperative night for any reason (65%) was related to greater pain during the next 2 days (r = .25 to .43). Although 41% of the women had previously used relaxation techniques for stress or pain, only 9% used it for pain after surgery. Results suggest that postoperative patients have moderate to severe pain that is incompletely relieved with patient-controlled analgesia. Nurses should encourage patients to press the patient-controlled analgesia button more often, report unrelieved pain, and use nonpharmacologic interventions.

Complex regional pain syndrome (type I, RSD; type II, causalgia): controversies

Introduction of the term complex regional pain syndromes (CRPS) as a replacement of the older terminology, reflex sympathetic dystrophy (RSD) and causalgia, has achieved two goals: it has focused attention on the diagnosis and treatment, and sent basic scientists back to their laboratories. The relation of sympathetically maintained pain and sympatholysis is examined, particularly as a neuropathic process that is found in many conditions, including CRPS. This review also focuses on recent observations proposing a pathologic basis in support of diagnosis and treatment of these disorders.

Complex regional pain syndrome: are the IASP diagnostic criteria valid and sufficiently comprehensive?

This is a multisite study examining the internal validity and comprehensiveness of the International Association for the Study of Pain (IASP) diagnostic criteria for Complex Regional Pain Syndrome (CRPS). A standardized sign/symptom checklist was used in patient evaluations to obtain data on CRPS-related signs and symptoms in a series of 123 patients meeting IASP criteria for CRPS. Principal components factor analysis (PCA) was used to detect statistical groupings of signs/symptoms (factors). CRPS signs and symptoms grouped together statistically in a manner somewhat different than in current IASP/CRPS criteria. As in current criteria, a separate pain/sensation criterion was supported. However, unlike in current criteria, PCA indicated that vasomotor symptoms form a factor distinct from a sudomotor/edema factor. Changes in range of motion, motor dysfunction, and trophic changes, which are not included in the IASP criteria, formed a distinct fourth factor. Scores on the pain/sensation factor correlated positively with pain duration (P<0. 001), but there was a negative correlation between the sudomotor/edema factor scores and pain duration (P<0.05). The motor/trophic factor predicted positive responses to sympathetic block (P<0.05). These results suggest that the internal validity of the IASP/CRPS criteria could be improved by separating vasomotor signs/symptoms (e.g. temperature and skin color asymmetry) from those reflecting sudomotor dysfunction (e.g. sweating changes) and edema. Results also indicate motor and trophic changes may be an important and distinct component of CRPS which is not currently incorporated in the IASP criteria. An experimental revision of CRPS diagnostic criteria for research purposes is proposed. Implications for diagnostic sensitivity and specificity are discussed.

Relief of postoperative pain with jaw relaxation, music and their combination

The aim of this randomized controlled trial was to determine the effect of jaw relaxation, music and the combination of relaxation and music on postoperative pain after major abdominal surgery during ambulation and rest on postoperative days 1 and 2. Opioid medication provided for pain, following abdominal surgery, does not always give sufficient relief and can cause undesired side effects. Thus, additional interventions such as music and relaxation may provide more complete relief. Previous studies have found mixed results due to small sample sizes and other methodological problems. In a rigorous experimental design, 500 subjects aged 18-70 in five Midwestern hospitals were randomly assigned by minimization to a relaxation, music, relaxation plus music, or control group. Interventions were taught preoperatively and tested postoperatively. The same amount of time was spent with subjects in the control group. Pain was measured with the visual analogue sensation and distress of pain scales. Demographic and surgical variables, and milligrams of parenteral or oral opioids in effect at the time of testing were not significantly different between the groups, nor did they correlate with pain scores. Controlling for pretest sensation and distress, orthogonal a priori contrasts and multivariate analysis of covariance indicated that the three treatment groups had significantly less pain than the controls, (P = 0.028-0.000) which was confirmed by the univariate analysis of covariance (P = 0.018-0.000). Post hoc multivariate analysis revealed that the combination group had significantly less sensation and distress of pain than the control group on all post-tests (P = 0.035-0.000), and the relaxation and music groups had significantly less on all tests (P = 0.022-0.000) except after ambulation. At post ambulation those using relaxation did not have significantly less pain than the controls on both days and those using music did not on day 1, although there were some univariate effects. A corresponding significant decrease in mastery of the interventions from pre to post ambulation suggests the need for reminders to focus on the intervention during this increased activity. Physicians and nurses preparing patients for surgery and caring for them afterward, should encourage patients to use relaxation and music as adjuvants to medication for postoperative pain.

External validation of IASP diagnostic criteria for Complex Regional Pain Syndrome and proposed research diagnostic criteria. International Association for the Study of Pain

Recent work in our research consortium has raised internal validity concerns regarding the current IASP criteria for Complex Regional Pain Syndrome (CRPS), suggesting problems with inadequate sensitivity and specificity. The current study explored the external validity of these IASP criteria for CRPS. A standardized evaluation of signs and symptoms of CRPS was conducted by study physicians in 117 patients meeting IASP criteria for CRPS, and 43 patients experiencing neuropathic pain with established non-CRPS etiology (e.g. diabetic neuropathy, post-herpetic neuralgia). Multiple discriminant function analyses were used to test the ability of the IASP diagnostic criteria and decision rules, as well as proposed research modifications of these criteria, to discriminate between CRPS patients and those experiencing non-CRPS neuropathic pain. Current IASP criteria and decision rules (e.g. signs or symptoms of edema, or color changes or sweating changes satisfy criterion 3) discriminated significantly between groups (P < 0.001). However, although sensitivity was quite high (0.98), specificity was poor (0.36), and a positive diagnosis of CRPS was likely to be correct in as few as 40% of cases. Empirically-based research modifications to the criteria, which are more comprehensive and require presence of signs and symptoms, were also tested. These modified criteria were also able to discriminate significantly, between the CRPS and non-CRPS groups (P < 0.001). A decision rule, requiring at least two sign categories and four symptom categories to be positive optimized diagnostic efficiency, with a diagnosis of CRPS likely to be accurate in up to 84% of cases, and a diagnosis of non-CRPS neuropathic pain likely to be accurate in up to 88% of cases. These results indicate that the current IASP criteria for CRPS have inadequate specificity and are likely to lead to overdiagnosis. Proposed modifications to these criteria substantially improve their external validity and merit further evaluation.

Complex Regional Pain Syndromes: guidelines for therapy

This report aims to present an orderly approach to the treatment of Chronic Regional Pain Syndrome (CRPS) types I and II through an algorithm. The central theme is functional restoration: a coordinated but progressive approach that introduces each of the treatment modalities needed to achieve both remission and rehabilitation. Reaching objective and measurable rehabilitation goals is an essential element. Specific exercise therapy to reestablish function after musculoskeletal injury is central to this functional restoration. Its application to CRPS is more contingent on varying rates of progress that characterize the restoration of function in patients with CRPS. Also, the various modalities that may be used, including analgesia by pharmacologic means or regional anesthesia or the use of neuromodulation, behavioral management, and the qualitatively different approaches that are unique to the management of children with CRPS, are provided only to facilitate functional improvement in a stepwise but methodical manner. Patients with CRPS need an individual approach that requires extreme flexibility. This distinguishes the management of these conditions from other well-described medical conditions having a known pathophysiology. In particular, the special biopsychosocial factors that are critical to achieving a successful outcome are emphasized. This algorithm is a departure from the contemporary heterogeneous approach to treatment of patients with CRPS. The underlying principles are motivation, mobilization, and desensitization facilitated by the relief of pain and the use of pharmacologic and interventional procedures to treat specific signs and symptoms. Self-management techniques are emphasized, and functional rehabilitation is the key to the success of this algorithm.

Complex regional pain syndrome of the breast in a patient after breast reduction

Complex regional pain syndrome (CRPS) is characterized by devastating pain, swelling, and cutaneous discoloration that result from vasomotor dysfunction caused by an abnormally accelerating sympathetic loop reflex after trauma or surgery. Although in the extremities CRPS is well documented as reflex sympathetic dystrophy, it only has been reported anecdotally in the breast after modified radical mastectomy and never reported after breast reduction. We report CRPS in the right breast of a 27-year-old woman after revision breast reduction surgery. The patient had signs of CRPS and symptoms of pain, swelling, epidermal scaling, and cutaneous temperature changes lasting more than 1 year. Liquid crystal thermographic scanning revealed a persistent, clinically significant hypothermic region in the affected breast. Intravenous phentolamine temporarily relieved the symptoms. Subsequent sympathetic blockade of the stellate ganglion alleviated chronic CRPS symptoms. Surgeons should be alert that CRPS may need to be considered in the differential diagnosis of chronic disproportionate pain after breast surgery. Early identification and treatment will help alleviate persistent CRPS symptoms and avoid soft-tissue changes.

Stimulation of the central and peripheral nervous system for the control of pain

After suffering some setbacks since its introduction in 1967, stimulation of the spinal and peripheral nervous systems has undergone rapid development in the last ten years. Based on principles enunciated in the Gate Control Hypothesis that was published in 1968, stimulation-produced analgesia [SPA] has been subjected to intensive laboratory and clinical investigation. Historically, most new clinical ideas in medicine have tended to follow a three-tiered course. Initial enthusiasm gives way to a reappraisal of the treatment or modality as side-effects or unanticipated problems arise. The last and third phase proceeds at a more measured pace as the treatment is refined by experience. This review is divided into three parts as it traces the progress of spinal cord stimulation [SCS] and peripheral nerve stimulation [PNS]. The review commences with a discussion of the theory of SCS and PNS, and is followed by early reports during which it became apparent that the modality is essentially only effective in the treatment of neuropathic pain. The last section describes the modern experience including efficacy in specific types of pain and concludes with recent accomplishments that dramatize the relief of pain which can be achieved in nonoperable peripheral vascular disease or myocardial ischemia. Over the years, a search for those transmitters that might be influenced by spinal cord stimulation focused on somatostatin, cholecystokinin (CCK), vasoactive intestinal polypeptide (VIP), neurotensin and other amines, although only substance "P" was implicated. More recently, in animal studies, evidence that GABA-ergic systems are affected may explain the frequent successful suppression of allodynia that follows spinal cord stimulation. During the past eight years, much attention has been directed to studies that use a chronic neuropathic pain model. While PNS held significant promise as a pain relieving modality, early electrode systems and their surgical implantation yielded variable results due to evolving technical and surgical skills. These results dramatically reduced the continued development of PNS, which then gave way to a preoccupation with SCS. Modern development of SCS with outcome studies, particularly in relation to failed back surgery syndrome [FBSS] and the outcome of peripheral nerve surgery for chronic regional pain syndromes, has earned both modalities a place in the ongoing management of patients with intractable neuropathic pain. The last section, dealing with pain of peripheral vascular and myocardial ischemia, is perhaps one of the more exciting developments in stimulation produced analgesia and as the papers discussed demonstrate, can provide a level of analgesia and efficacy that is unattainable by other treatment modalities. SCS and PNS has an important role to play in the management of conditions that are otherwise refractory to conservative or other conventional management.

Long-term results of peripheral nerve stimulation for reflex sympathetic dystrophy

This prospective, consecutive series describes peripheral nerve stimulation (PNS) for treatment of severe reflex sympathetic dystrophy (RSD) or complex regional pain syndrome, in patients with symptoms entirely or mainly in the distribution of one major peripheral nerve. Plate-type electrodes were placed surgically on affected nerves and tested for 2 to 4 days. Programmable generators were implanted if 50% or more pain reduction and objective improvement in physical changes were achieved. Patients were followed for 2 to 4 years and a disinterested third-party interviewer performed final patient evaluations. Of 32 patients tested, 30 (94%) underwent permanent PNS placement. Long-term good or fair relief was experienced in 19 (63%) of 30 patients. In successfully treated patients, allodynic and spontaneous pain was reduced on a scale of 10 from 8.3 +/- 0.3 preimplantation to 3.5 +/- 0.4 (mean +/- standard error of the mean) at latest follow up (p<0.001). Changes in vasomotor tone and patient activity levels were markedly improved but motor weakness and trophic changes showed less improvement. Six (20%) of the 30 patients undergoing PNS placement returned to part-time or full-time work after being unemployed prestimulator implantation. Initial involvement of more than one major peripheral nerve correlated with a poor or no relief rating (p<0.01). Operative modifications that minimize technical complications are described. This study indicates that PNS can provide good relief for RSD that is limited to the distribution of one major nerve.

Long-term intraspinal infusions of opioids in the treatment of neuropathic pain

Long-term intraspinal infusions of opioid drugs are being increasingly utilized in patients with noncancer pain. Despite this, there is a lack of long-term information, including success and failure rates for pain relief and technical problems. During a 5-year period, 18 noncancer patients underwent implantation of programmable infusion pumps for long-term intrathecal opioid infusion. Patients had (a) neuropathic pain, (b) had failed or been ineligible for noninvasive treatments, and (c) obtained greater than 50% pain relief with intrathecal trial infusions of morphine sulfate or sufentanil citrate. A disinterested third-party reviewer evaluated patients at the most recent follow-up. Sixty-one percent (11/18) of patients had good or fair pain relief with mean follow-up 2.4 +/- 0.3 years (0.8-4.7 years). Average numeric pain scores decreased by 39% +/- 4.3%. Five of the 11 responders required lower opioid doses (12-24 mg/day morphine) and the remaining six patients required higher opioid doses (> 34 mg/day morphine). Failure of long-term pain relief occurred in 39% (7/18) despite good pain relief in trial infusions and the use of both morphine and sufentanil. Technical problems developed in 6/18 patients but appeared to be preventable with further experience. Long-term intrathecal opioid infusions can be effective in treatment of neuropathic pain but might require higher infusion doses.

Reflex sympathetic dystrophy: changing concepts and taxonomy

We present a revised taxonomic system for disorders previously called reflex sympathetic dystrophy (RSD) and causalgia. The system resulted from a special consensus conference that was convened on this topic and is based upon the patient's history, presenting symptoms, and findings at the time of diagnosis. The disorders are grouped under the umbrella term CRPS: complex regional pain syndrome. This overall term, CRPS, requires the presence of regional pain and sensory changes following a noxious event. Further, the pain is associated with findings such as abnormal skin color, temperature change, abnormal sudomotor activity, or edema. The combination of these findings exceeds their expected magnitude in response to known physical damage during and following the inciting event. Two types of CRPS have been recognized: type I, corresponds to RSD and occurs without a definable nerve lesion, and type II, formerly called causalgia refers to cases where a definable nerve lesion is present. The term sympathetically maintained pain (SMP) was also evaluated and considered to be a variable phenomenon associated with a variety of disorders, including CRPS types I and II. These revised categories have been included in the 2nd edition of the IASP Classification of Chronic Pain Syndromes.

Spinal cord stimulation versus spinal infusion for low back and leg pain

The relative roles of spinal cord stimulation and the spinal infusion of opioids in the treatment of chronic, non-cancer lower body pain remains unclear. This report contains a retrospective analysis of patients with chronic lower body, neuropathic pain and treated over a 5 year period. Unilateral leg and/or buttock pain was treated initially with spinal stimulation and bilateral leg or mainly low back pain was treated initially with spinal infusions. 26 patients received spinal stimulation. Pain relief was > or = 50% in 16 (62%) with increased activity levels. Stimulator coverage was most difficult or failed in patients with buttock pain. 16 patients received long-term spinal infusions. Pain relief was > or = 50% in 2 (13%) but 25-49% in another 8 (50%) with stable infusion doses and was best in patients requiring low-dose (< 1 mg/h morphine intrathecal) infusions in the trial period. The review indicates that spinal infusions may be best for bilateral or axial pain that has not responded to spinal stimulation. Clonidine appears to be an alternative in high-dose morphine patients. New diamond-shaped electrode and dual quadripolar arrays appear to be very helpful for back, buttock, and/or bilateral leg pain patterns.

Exogenous and endogenous plasma levels of epinephrine during dental treatment under local anesthesia

BACKGROUND AND OBJECTIVES

To determine serum levels of catecholamines after local anesthesia for dental treatment, we used tritium-labeled epinephrine as a vasoconstrictor for dental local anesthesia.

METHODS

Twenty healthy male outpatients undergoing standardized dental treatment (deep scaling) were studied. In all patients, only one quadrant was anesthetized even though the treatment was performed on all teeth. Two milliliters of articaine 4% (amide anesthetic) with 20 micrograms epinephrine was used as local anesthetic. Of the total epinephrine administered, 1.2% (100 microCi) consisted of tritium-labeled epinephrine. Blood samples were drawn through a central venous catheter before and at frequent intervals after the local anesthetic solution was administered.

RESULTS

A dramatic increase in exogenous epinephrine was observed in four patients during injection (up to 6937 pg/mL). The other 16 patients demonstrated a continuous increase in applied epinephrine that peaked on average at the 7th minute (631.5 +/- 41.4 pg/mL). A second increase occurred after the beginning of the dental procedure. The mean total epinephrine levels were always higher than those of the applied epinephrine. Extrasystoles were observed in two of four and tachycardia in three of four patients with high plasma levels of applied epinephrine. Increases in total epinephrine were associated with exogenous catecholamine administration, whereas the dental treatment did not significantly influence the plasma levels.

CONCLUSION

Despite aspiration in 20% of the patients, an unintended intravascular injection occurred. Although healthy young men tolerated large increases in central plasma epinephrine levels surprisingly well, this may not be the case in patients with concurrent cardiovascular disease. Patients at cardiovascular risk should be under continuous monitoring when an epinephrine-containing solution is applied.

Neuroanatomy and pathophysiology of pain related to spinal disorders

Sensation is achieved through the integration of many neural elements: receptors, afferent and efferent neurons, the spinal cord with its subdivisions, and the higher brain centers. One of the many sensations perceived by the human body is that of pain or nociception. To understand the concept of "back pain" associated with various spinal pathologies, some basic knowledge of the anatomy and physiology of sensation, and more specifically nociception, is necessary. This knowledge is presented herein.

[Postoperative analgesia following spondylodesis using a peridural catheter placed during surgery. Results of a pilot study]

For the treatment of postoperative (p.o.) pain following vertebral surgery, systemic analgesics are frequently used in high doses with a variety of side effects. It was the aim of this study to investigate p.o. epidural catheter analgesia in 20 patients following surgical correction of scoliosis using the Cotrel and Dubousset technique. METHODS. The patients received balanced general anesthesia with fentanyl and isoflurane. At the end of the operation, before closing the fascia, an epidural catheter was placed by the orthopedic surgeon. After extubation and following evaluation of the motor function of all extremities. 6-10 ml bupivacaine 0.25% was injected into the epidural catheter followed by continuous administration of 0.25% bupivacaine 4-8 ml/h. Analgesic level and hemodynamic parameters were monitored. Pain was measured by the visual analogue scale. If analgesia was not sufficient, the patients received tramadol or piritramide intravenously. RESULTS. In 11 of 20 patients epidural analgesia was rated adequate; 5 needed additional systemic analgesics, and in 4 effective analgesia was not achieved with either epidural analgesia or systemic opioids. No complications were observed. DISCUSSION. The pilot study documented that epidural analgesia using an intraoperatively placed epidural catheter can be used for p.o. pain relief after vertebral surgery using the Cotrel and Dubousset technique. Additional studies will compare the method described to other pain-relieving procedures.

Arterial and mixed venous blood gas status during apnoea of intubation--proof of the Christiansen-Douglas-Haldane effect in vivo

The Christiansen-Douglas-Haldane effect, in short the Haldane effect, describes the dependence of the CO2 binding of blood on the degree of oxygenation of haemoglobin. Under the physiological conditions of an 'open' system between blood and alveoli the partial pressure of arterial CO2 (PaCO2), must be less than that of mixed venous blood (PvCO2). During the unphysiological conditions of a 'closed' system, e.g. hyperoxic apnoea, i.e. continuous oxygen uptake without CO2 delivery by the lungs, the PaCO2 will not only approximate the PvCO2 but will even exceed it. Without the Haldane effect, rapid adjustment of PaCO2 to PvCO2 would be expected during apnoea due to the lack of CO2 excretion. If, however, as undertaken in this study, ongoing oxygenation (high alveolar PO2 (PACO2) with concomitant lack of CO2 delivery (apnoea, i.e. the CO2 concentration remains constant) lead to a continuing sufficient oxygenation of blood during its passage through the lung capillaries, then this leads to a rightwards shift of the CO2 binding curve--the Haldane effect. The resulting increase in PCO2 as shown here actually leads to an arterial-mixed venous CO2 partial pressure difference (avDPCO2) of 2.8 +/- 1.8 mmHg. The results described substantiate for the first time the existence of the Haldane effect under clinical conditions.

[The effect of the injection speed on the blockade characteristics of hyperbaric bupivacaine and tetracaine in spinal anesthesia]

A lack of uniform methodology used in the assessment of different injection speeds in spinal anesthesia by different authors formed the basis of the current study, which compared under randomized conditions the effects of various injection speeds during intrathecal administration of 4 ml 0.5% hyperbaric bupivacaine or 0.5% hyperbaric tetracaine. MATERIALS AND METHODS. Eighty male ASA Physical Status II and III patients scheduled for transurethral resection of the prostate under spinal anesthesia were selected. They were randomly divided into four groups of 20 each. Patients were given 4 ml of either 0.5% hyperbaric bupivacaine or 0.5% hyperbaric tetracaine according to the following scheme: I: 4 ml tetracaine/0.25 ml.s-1; II: 4 ml tetracaine/0.5 ml.s-1: III: 4 ml bupivacaine/0.25 ml.s-1; IV: 4 ml bupivacaine/0.5 ml.s-1. The study was carried out in a double-blind fashion and puncture was performed at the L3-4 interspace using a 25-gauge needle with the patient in the sitting position. Following injection of the anesthetic solution (0.25 ml.s-1 or 0.5 ml.s-1 without barbotage), the patient was immediately placed in the lithotomy position with the table remaining horizontal. The level of anesthesia using pin prick and the degree of motor blockade, using a 0 to 3+ scale where 0 represented no motor weakness and 3+ complete motor block, were assessed at specific intervals. Statistical analysis was performed using the Mann-Whitney rank sum test: P value of less than 0.05 was considered statistically significant. RESULTS. Bupivacaine injected at 0.25 ml.s-1 was associated with a higher dermatome level than at 0.5 ml.s-1 (P less than 0.05). Time to highest dermatome, however, was shorter with bupivacaine 0.5 ml.s-1 compared to 0.25 ml.s-1 (P less than 0.05) (Table 3, Fig. 1). Time to highest level of analgesia was shorter with tetracaine 0.25 ml.s-1 compared to 0.5 ml.s-1 (P less than 0.05) (Fig. 2). At 0.25 ml.s-1, tetracaine achieved the highest dermatome faster than bupivacaine (P less than 0.05). Tetracaine injected at 0.5 ml.s-1, however, was associated with a higher segmental level than bupivacaine (P less than 0.05). At 0.25 ml.s-1 bupivacaine and tetracaine achieved a 3+ motor block faster than at 0.5 ml.s-1 (P less than 0.05). Complete motor blockade, however, was significantly longer with tetracaine at both injection speeds (0.25 and 0.5 ml.s-1) compared to bupivacaine (P less than 0.05). CONCLUSIONS. The results suggest that 4 ml 0.5% hyperbaric bupivacaine or tetracaine injected at 0.25 or 0.5 ml.s-1 provides a rapid and reproducible spread of analgesia for transurethral surgery. However, our findings suggest that speed of injection is of little i

[Effect of dihydroergotamine (DHE) on blood volume and circulation in the calf in peridural anesthesia in the human]

Dihydroergotamine (DHE) preferentially constricts capacitance vessels in the skin and striated musculature, thereby redistributing blood in favor of the pulmonary vascular bed in the presence of neurogenic vascular tone. The aim of this study was to see if DHE would act likewise when neurogenic vascular tone is absent. Filling and blood flow of the calves were measured plethysmographically in six healthy, supine male volunteers before and during peridural anesthesia (PDA) to the level of at least T5 and, in the denervated state, after the injection of DHE 7.5 micrograms/kg intravenously. Arterial blood pressure, central venous pressure (CVP), and heart rate were also determined. Both blood flow (+2.2 ml/min per 100 ml tissue) and volume (+1 ml/100 ml tissue) of the calves increased while CVP and systolic arterial pressure decreased during PDA (Table 1). DHE did not affect the PDA-included increase in blood flow, but strongly reduced calf volume (-1.7 ml/100 ml tissue). This was accompanied by an increase in CVP and systolic blood pressure (Fig. 1). In the absence much as in the presence of neurogenic vascular tone, DHE preferentially constricts capacitance but not resistance vessels. Thus, DHE counteracts the vascular effects of PDA, as it improves cardiac filling and consequently raises arterial blood pressure by redistributing blood from the dilated capacitance vessels without curtailing blood flow. It would appear, therefore, that DHE is a rational alternative to fluid therapy for the prophylaxis of arterial hypotension during major conduction anesthesia.

Venoconstrictor agents mobilize blood from different sources and increase intrathoracic filling during epidural anesthesia in supine humans

The authors studied the effects of dihydroergotamine (DHE) and etilefrine hydrochloride (E) on the regional distribution of 99mTc-marked erythrocytes during epidural anesthesia in eight supine men to determine if vasoactive agents with venoconstrictor action would enhance cardiac filling during epidural anesthesia. Radioactivity was recorded with a gamma camera, and its distribution determined in the thorax, abdomen, and limbs. Arterial and central venous pressure, heart rate, and calf volume by plethysmography were measured. During epidural anesthesia with a sensory block up to T4/5, DHE (7.5 micrograms/kg) reduced the radioactivity, i.e., blood volume, in both the innervated (-5.9 +/- 3.5%) and denervated muscle/skin (-16.9 +/- 7%) regions, and increased it in both the intrathoracic (+7.0 +/- 2.3%), and splanchnic vasculature (+4.2 +/- 3.2). In contrast, E (6 micrograms X kg-1 X min-1) decreased the blood volume most markedly in the splanchnic region (-5.4 +/- 0.7%) and increased it in the thorax (+2 +/- 0.6%). All these changes were statistically significant. The combined effects were estimated to be equivalent to a transfusion of nearly 1.01 of blood. Both drugs reversed the hypotensive action of epidural anesthesia. During epidural anesthesia, DHE preferentially constricted the capacitance vessels in skeletal muscle and skin irrespective of the state of innervation, whereas E preferentially constricted the splanchnic vasculature. In the doses used, the two agents replenished in an additive fashion the central circulation during epidural anesthesia.

Peridural anesthesia and the distribution of blood in supine humans

To determine the effects of vasomotor tone on intrathoracic and splanchnic blood volume, the distribution of radioactively (99mTc) labeled erythrocytes was recorded by whole body scintigraphy before and during peridural anesthesia (PDA) in eight supine men. The radioactivity was recorded with a gamma camera and its distribution determined in the thorax, abdomen, and limbs. Arterial and central venous pressure, heart rate, and calf volume and flow also were measured. During PDA with a sensory block up to T4/5, radioactivity increased only in the denervated legs (+ 9.9 +/- 2.3% SE), whereas it decreased in all other regions, i.e., in the thorax (-8.1 +/- 1.2%), the innervated upper limbs (-10.6 +/- 4.0%), and in the splanchnic vasculature (-5 +/- 1.7%). However, in two of the subjects, after an initial decrease, splanchnic blood content increased while intrathoracic blood volume decreased further. The effects of PDA on thoracic and splanchnic filling could be duplicated by the sequestration of about 500-600 ml of blood in both legs. In supine humans high peridural anesthesia evokes the same decrease in intrathoracic blood volume as orthostasis. This seems to be counteracted by a reflex decrease in filling of the denervated muscle and skin areas and also by a constriction of the splanchnic vasculature by an unknown mechanism. Potential circulatory collapse may ensue when the vasoconstrictor response fails in the splanchnic circulation.

The effects of adding adrenaline to etidocaine and lignocaine in extradural anaesthesia I: block characteristics and cardiovascular effects

The addition of adrenaline 5 mug/ml, 1 : 200 000 to 1% etidocaine hydrochloride administered extradurally (L2-3) shortened significantly the onset time for sensory blockade, particularly with respect to the spread of the analgesia from the injection site, and shortened the already rapid onset of motor block. Etidocaine hydrochloride 1% plain caused a slower onset of block, laster longer and produced more profound analgesia over the caudal dermatomes than did 2% lignocaine hydrochloride. The motor block from plain etidocaine was more profound in its extent and lasted longer than that caused by lignocaine. With regard to cardiovascular variables, there were no significant differences between subjects receiving the plain etidocaine and the plain lignocaine. However, subjects receiving etidocaine with adrenaline exhibited increased cardiac stimulation and a decrease in total peripheral resistance over the first 150 min.

Effects of extradural block: comparison of the properties, circulatory effects and pharmacokinetics of etidocaine and bupivacaine

Five healthy, unmedicated male volunteers, aged 19-25 yr, participated in a double-blind, crossover study. Each subject received, on separate occasions and via a catheter placed at L2, 1.5% etiodocaine HCl20 ml with adrenaline 5 mug/ml, or 0.75% bupivacaine HCl 20 ml with adrenaline 5 mug/ml for extradural analgesia. In addition, in order to calculate the absorption rate of the local anaesthetic agent, each subject received on two further occasions etidocaine HCl 75 mg and bupivacaine HCl 75 mg respectively by i.v. infusion, over a period of 10 min. Spread of sensory analgesia to four segments above and below the site of injection was faster with etidocaine (13 +/- 3 min) (mean +/- SD) than with bupivacaine (22 +/- 8 min). Two-segment regression occurred later for bupivacaine (260 +/- 57 min) than for etidocaine (180 +/- 96 min). Caudal spread of analgesia was more extensive with etidocaine than with bupivacaine. The onset of motor blockade tended to be faster with etidocaine (5.8 +/- 3.0 min), than with bupivacaine (10.0 +/- 3.5 min); regression of motor blockade by one unit was longer with etidocaine (306 +/- 103 min) than bupivacaine (238 +/- 75 min). Sudomotor block occurred earlier with etidocaine (4.0 +/- 2.1 min) than bupivacaine (13.7 +/- 4.8 min). Significant changes in cardiac stroke work and stroke volume occurred. For etidocaine these measurements remained below control values for 120-210 min after injection. The mean maximum arterial plasma concentration of etidocaine was 1.52 +/- 0.64 mug/ml, at 14 +/- 2 min and of bupivacaine was 1.35 +/- 0.63 mug/ml, achieved at 20 +/- 4 min. The systemic absorption of both drugs occurred in a biphasic pattern with a fast and slow half-life of 0.3 and approximately 8 h respectively.

Hemodynamic drug interaction: peridural lidocaine and intravenous ephedrine

Hypotension following peridural anesthesia with lidocaine was treated by intravenous injection of ephedrine. The ephedrine relieved the cardiovascular depression, but was associated with a concomitant increase in plasma lidocaine concentrations. This increase may push the plasma lidocaine concentration into the toxic region.

Effects of peridural block: V. Properties, circulatory effects, and blood levels of etidocaine and lidocaine

Ten healthy, unpremedicated, male volunteers, aged 21-33 years, were given 20 ml 1 per cent etidocaine with 5 mug/ml epinephrine for peridural analgesia via a catheter placed L2. On a different occasion they were given 20 ml 2 per cent lidocaine with 5 mug/ml epinephrine in the same manner. Initial onset of sensory analgesia to pin prick was faster for etidocaine (7 min) than for lidocaine (9 min). Analgesia lasted significantly longer after etidocaine with respect to both two-segment regression (177 plus or minus SE min vs. 114 plus or minus 8 min) and total duration (379 plus or minus 22 min vs. 190 plus or minus 8 min). Onset of maximal motor blockade was significantly faster with etidocaine (15.4 plus or minus 2.5 min) than with lidocaine (31.7 plus or minus 3.3 min); blockade lasted longer with etidocaine (331 plus or minus 25 min vs. 167 plus or minus 13 min). Changes in mean arterial pressure cardiac output, central venous pressure, limb blood flows, total peripheral resistance, and stroke volume were similar with the two drugs, although those after etidocaine were more prolonged as a result of the longer blockade. Mean maximum arterial concentrations of etidocaine were 0.96 plus or minus 0.05 SE mug/ml (plasma) and 0.55 plus or minus 0.03 mug/ml (whold blood), achieved at 17 plus or minus 2 min. Mean maximum arterial concentrations of lidocaine were 2.22 plus or minus 0.09 mug/ml (plasma) and 1.85 plus or minus mug/ml (whold blood), achieved at 24 plus or minus 2 min. No sign of central toxicity was observed with either drug, although subjects receiving lidocaine tended to sleep, which was not the case with etidocaine. Hematologic screening, blood chemistries, and urinalyses performed 24 hours before and after each study showed no abnormality.