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Print version ISSN 0034-7094On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.54 no.3 Campinas May/June 2004
Continuous epidural analgesia: analysis of efficacy, side effects and risk factors*
Analgesia peridural continua: análisis de la eficacia, efectos adversos y factores de riesgo para ocurrencia de complicaciones
Leonardo Teixeira Domingues Duarte, TSA, M.D.I; Maria do Carmo C. Barreto Fernandes, M.D.II; Marcelino Jäger Fernandes, TSA, M.D.I; Renato Ângelo Saraiva, TSA, M.D.III
IAnestesiologista da Rede SARAH de
Hospitais do Aparelho Locomotor
IIEnfermeira do Grupo de Dor do Hospital Sarah, Brasília
IIICoordenador de Anestesiologia da Rede SARAH de Hospitais do Aparelho Locomotor
BACKGROUND AND OBJECTIVES: Epidural analgesia
with local anesthetics and opioids has a reputation of high efficacy with low
incidence of side effects. This study aimed at determining incidence, type and
severity of postoperative complications related to epidural analgesia and catheter
METHODS: Participated in this retrospective study 469 patients submitted to postoperative epidural analgesia in the period 10/18/99 to 10/18/01. Epidural analgesia was induced with 0.1% bupivacaine and fentanyl (1 to 5 µg.mL-1), at a 3 mL.h-1 rate. Infusion rate was adjusted according to patients' pain complaint. The following variables were evaluated: epidural infusion duration; incidence of side-effects and complications related to demographics, type of surgery and epidural catheter position; and quality of analgesia by means of a pain visual analog scale and a patients' satisfaction index.
RESULTS: Epidural catheters remained in place 2.2 days in average, varying from 6 to 10 days. Global rate of technique-related complications was 46.3%, most of them minor complications without clinical repercussion. From these, 13.9% were directly related to the epidural catheter (disconnection, externalization, low back pain, inflammation and local infection). Other common complications were vomiting and urinary retention. Postoperative analgesia was effective in 97.2% of the patients which referred satisfaction with the technique. Patients without pain or slight pain during the first, second and third postoperative day represented 80.1%, 92.8% and 93.3%, respectively, of the studied population.
CONCLUSIONS: Continuous epidural analgesia is effective and safe. Complications were not severe. However, strict vigilance is mandatory to achieve satisfactory analgesia and a low incidence of complications.
Key Words: ANALGESIA, Postoperative; ANESTHETIC TECHNIQUES, Regional: epidural
JUSTIFICATIVA Y OBJETIVOS: La analgesia
promovida por la infusión peridural de anestésico local con analgésicos
opioides es reconocidamente de buena calidad y con pocos efectos adversos. El
objetivo de este estudio fue determinar el número, formas y gravedad de
las complicaciones pós-operatorias relacionadas a la analgesia peridural
y a la inserción del catéter peridural.
MÉTODO: Fueron evaluados, retrospectivamente, 469 pacientes sometidos a la analgesia peridural pós-operatoria entre 18/10/1999 y 18/10/2001. La analgesia peridural fue conducida usándose solución de bupivacaína 0,1% con fentanil (1 a 5 µg.ml-1), iniciándose la infusión a 3 ml.h-1. La velocidad de infusión era ajustada de acuerdo con la queja álgica del paciente. Fueron analizadas las siguientes variables: la duración de la infusión peridural; la ocurrencia de efectos adversos y complicaciones, relacionándolos a los datos demográficos, tipo de cirugía y posición del catéter peridural; y la calidad de la analgesia obtenida con la técnica (escala analógico-visual de dolor e índice de satisfacción del paciente).
RESULTADOS: Los catéteres peridurales permanecieron implantados por una media de 2,2 días, variando de 6 horas a 10 días, y el índice global de complicaciones relacionadas a la técnica fue de 46,3%, siendo que la mayoría fue de pequeña magnitud, sin repercusión clínica. De estas, 13,9% estaban relacionadas directamente al catéter peridural (desconección, exteriorización, dolor lumbar, inflamación e infección local). Otras complicaciones más comunes fueron encontradas: vómitos y retención urinaria. La analgesia pós-operatoria fue efectiva con 97,2% de los pacientes refiriendo satisfacción con la técnica. Pacientes sin dolor o con dolor leve, en el primero, segundo y tercero días de pós-operatorio, constituyeron, respectivamente, 80,1%, 92,8% y 93,3% de la población estudiada.
CONCLUSIONES: La analgesia peridural continua es efectiva y segura. Las complicaciones ocurridas no fueron consideradas graves. Todavía, no se puede dispensar rigurosa vigilancia a fin de obtenerse analgesia satisfactoria y diminuir las complicaciones.
Complete postoperative pain relief has been always the anesthesiologists' objective. This goal, however, is not always fully achieved. Analgesia is important not only to decrease patients' discomfort and promote wellbeing, but also because pain may lead to cardiovascular and respiratory complications.
It has been shown that postoperative epidural analgesia results in shorter ICU stay 1, improved pulmonary function 2-4, less thromboembolic and cardiovascular complications 1,5, earlier bowel movements and functioning 6,7, and shorter hospital stay 3,8. The hypothesis behind such findings is that epidural analgesia blocks stress response trough pain relief and/or sympathetic block 9. These factors together with other measures, such as active postoperative mobilization and early return to oral nutrition 10-12 have led to the proposal that epidural analgesia would improve patients' evolution 7,13 and could decrease morbidity and mortality 10,14,15.
These benefits are not obtained without risks or adverse events. Among them, the risk for respiratory depression following the use of opioids is a concern for many anesthesiologists who, then, decide not to use the technique in the postoperative management of their patients 16. Alternatively and for safety reasons, several professionals limit the use of epidural opioids to patients who will remain under strict monitoring in postoperative intensive or intermediate care units 16,17. Other complications that may follow epidural analgesia and represent potential risks for patients' physical status include hypotension, epidural catheter migration to intravascular and spinal spaces, and epidural abscesses and hematomas 18.
On the other hand, adverse effects without clinical severity, but which might be very uncomfortable for patients are the most common. They are related to epidural analgesia tolerability, and the most common are nausea, vomiting, pruritus, sleepiness and urinary retention.
This study is a review of all patients receiving continuous epidural bupivacaine, epinephrine and fentanyl for postoperative analgesia in the period from 10/18/99 to 10/18/01 in the Sarah Locomotor System Hospital, Brasilia - Brazil.
This study aimed at evaluating the postoperative analgesia efficacy, incidence and severity of complications and adverse events of the analgesic technique, and at identifying possible risk factors for complications.
Since the proposal was to continuously evaluate quality of assistance of our Postoperative Pain Management Group, we have obtained approval of our hospital's Research Ethics Committee
All patients submitted to postoperative continuous epidural analgesia were retrospectively evaluated. From records of the Postoperative Pain Management Group of patients under continuous epidural infusion, a database was built with demographic data as those related to type of surgery, analgesic solution, postoperative pain and adverse events, as well as management approaches. Since our major objective was to evaluate the effectiveness of continuous epidural analgesia in a heterogeneous population representative or our daily routine, all patients who, at the judgment of the anesthesiologist in charge, would benefit from postoperative continuous epidural analgesia were included in this study. So, adults and children, males and females, including patients with brain injury and cognitive difficulties were included. The latter, however, were excluded from postoperative analgesia evaluation since they were unable to use the pain visual analog scale. Clinical criteria and questions to relatives and escorts were used to analyze remaining variables.
After desinfection of the lumbar or thoracic region, according to surgery site, with 0.5% alcohol chlorhexidine solution an epidural 20G multihole catheter (Perifix® B. Braun - with holes at 5, 9 and 13 mm from the blunt point) was introduced with 18G epidural Tuohy needle using the loss of resistance to air technique for epidural space identification. Catheter was introduced immediately before surgery approximately 4 to 6 cm in the epidural space. Insertion site was chosen by the anesthesiologist in charge, so that the catheter tip would be located in the median site of dermatomes involved in surgical injury. A 2 µm antibacterial filter was added to epidural catheter and was maintained until postoperative epidural infusion completion. Epidural catheter was fixed to patient's skin with transparent adhesive dressing to allow a minor turn of the catheter between insertion point and adhesive fixation, aiming at minimizing the possibility of epidural catheter movement 19.
After postanesthetic recovery unit arrival, we waited the motor block regression until patients were able to bend knees and/or thighs over the hip. At this point, the anesthesiologist in charge of the PACU would start the continuous epidural infusion of 0.1% bupivacaine with 1 µg.mL-1 epinephrine and preservative-free fentanyl at a rate of 3 mL.h-1, using an Abbott Pain Management Provider® infusion pump. Although most studied patients have received a 3 µg.mL-1 fentanyl solution, the concentration actually varied from 1 to 5 µg.mL-1 due to changes in daily management routine along the study and also depending on patients' weight. The epidural analgesic solution was prepared by the recovery unit anesthesiologist with strict assepsis care.
Postoperative analgesia was prescribed by the recovery unit anesthesiologist and included postoperative pain, nausea, vomiting and respiratory depression management. In addition to continuous epidural analgesia, other types of analgesia were limited to 20 to 30 mg.kg-1 dypirone and 20 mg/day intravenous tenoxicam. No systemic opioid was administered simultaneously to epidural infusion. Postoperative nausea and vomiting were treated with metoclopramide and, if needed, intravenous ondansetron. Nursing staff was oriented to administer intravenous naloxone and immediately call the physician on duty if respiratory rate fell below 8 bpm. Drug to treat pruritus was chosen by the attending anesthesiologist during postoperative calls. However, the most frequent choice has been dexchlorpheniramine.
Each patient was seen at least twice a day by one Postoperative Pain Management Group anesthesiologist and one nurse. For every call, pain scores were recorded, in general at rest, using a 10 cm visual analog scale varying from zero (no pain) to 10 (the worst imaginable pain). Sleepiness was evaluated according to patients' or their escorts' report, who could complain the day after surgery of "heavy sleep" or "having slept too much". Patients were also actively asked about the incidence and intensity of nausea, vomiting (two or more episodes) and pruritus, as well as urinary retention (need for vesical catheter), low back pain and constipation. Epidural catheter insertion site was daily checked for erythema, edema and serum or pus discharge. The incidence of adverse events and complications related to epidural infusion and catheter was also recorded.
Using aseptic technique, epidural catheter insertion site dressing was changed by the Postoperative Pain Management Group nurse in alternate days or when there was bleeding at insertion point or if dressing detached. In case of inflammatory signs, epidural catheter was removed. Before catheter removal, skin around insertion site was thoroughly cleaned with chlorhexidine soap followed by at least three applications of 0.5% alcohol chlorhexidine. After collection of epidural lavage fluid and epidural catheter tip, these were submitted to microbiological test for epidural catheter colonization. Infection at catheter insertion site was defined as the presence of erythema, edema or serum or pus secretion, while for infection/colonization diagnosis it was necessary to isolate bacteria from epidural lavage fluid or catheter tip.
Analgesic technique quality was evaluated at the end of treatment when each patient or escort was asked about satisfaction with the treatment received and if they would agree in repeating the technique in case of another surgery.
Inadequate analgesia was defined as patient-referred pain score equal to or above 4. For those cases, bolus epidural solution was administered and/or epidural infusion was increased at Postoperative Pain Management Group anesthesiologist's judgment.
The decision to withdraw epidural analgesia depended on the Postoperative Pain Management Group anesthesiologist, according to the following criteria: (1) elective, when analgesia was effectively obtained (pain scores between zero and 2) for at least 24 hours after the introduction of oral analgesics. For cognitive deficit patients and small children unable to refer pain scores, clinical criteria such as vital signs, respiratory pattern and relaxation in bed were considered in the decision to withdraw epidural analgesia, as well as relatives and escorts opinion; (2) in the presence of epidural catheter-related problems, such as disconnection, externalization or inflammation or infection signs at epidural catheter insertion site; (3) when adverse events could not be controlled by adjusting epidural infusion or with specific medication; (4) when pain complaint would remain in spite of epidural infusion adjustment, characterizing analgesia failure.
Age, weight and gender, epidural catheter position, whether lumbar or thoracic, and type of surgery were evaluated to check whether they constituted risk factors for the incidence of epidural continuous infusion or catheter-related adverse events and complications.
In addition to descriptive analysis, Chi-square, Fisher's Exact and Student's t tests were used to test the association between possible risk factors and the incidence of adverse events and complications. Associations were considered significant when p < 0.05.
Participated in this study 469 patients submitted to orthopedic or chest surgeries in the period 10/18/99 to 10/18/01, who received continuous epidural infusion for postoperative analgesia.
Surgeries were divided in groups according to surgical aggression and postoperative pain intensity (Table I). Demographics data are shown in table II. As to fentanyl concentration in the analgesic solution, 93.4% of patients have received 3 µg.mL-1.
Mean epidural catheter permanence was 2.2 days with 2 days mode and median, however varying from 6 hours to 10 days. Epidural analgesia was administered through lumbar catheter (L2 to L5) in 402 patients (85.7%), and through thoracic catheter (T2 to T7) in 67 patients (14.3%).
Analgesia was, in general, satisfactory. In the first postoperative day, 354 patients (80.1%) have referred no pain or mild pain (1 to 3 in the visual analog scale). In the second postoperative day they were 92.8%. Table III shows patients distribution along the postoperative period according to pain scores. Scores of just 442 patients were obtained in the first postoperative day since many patients had difficulties in informing pain score while others had cognitive deficits due to brain injury. The number of scores has decreased in subsequent postoperative days since the number of patients with epidural catheter has also decreased. Infusion rate had to be increased in the first 24 postoperative hours for 84 patients (17.9%), since they referred score above 4 in the pain visual analog scale. Figure 1 shows distribution of pain scores along postoperative days. Highest daily scores obtained during patients' evaluation were considered for each postoperative day. From 469 patients, 442 were able to provide objective information about pain intensity according to visual analog scale. On the other hand, at treatment completion, subjective information about satisfaction with the technique could be obtained from all patients or their tutors, and 97.2% of them have referred satisfaction with the analgesic technique.
Adverse Events and Complications
Adverse events and complications related to the analgesic technique were classified as general when related to continuous bupivacaine, epinephrine and fentanyl infusion, or as epidural catheter-related. From 469 patients, 46.3% have presented some type of complication or adverse event. From all studied patients, 40.7% had general complications and 13.9% had epidural catheter-related complications. Table IV and table V describe general and catheter complications and their respective incidences. Most frequent general problems were vomiting, urinary retention and pruritus. Among catheter-related problems, disconnection or externalization were by far the most frequent complications. There has been one case of respiratory depression still in the postanesthetic recovery unit immediately after surgery, which required naloxone without however the need to abandon epidural analgesia technique. There have been no hematomas or epidural abscesses.
No patient had the continuous epidural infusion suspended due to analgesic failure or adverse events related to the technique. However, 65 patients (13.9%) had their treatment interrupted due to epidural catheter problems and have required another type of analgesia, mostly intravenous morphine. Remaining patients (86.1%) had their epidural infusion suspended electively.
Potential Risk Factors
There has been a balance in the incidence of adverse events between males (47.1%) and females (52.9%). No significant differences in global incidence of complications among children (< 16 years), adults (17 to 60 years) and elderly (> 60 years) was observed. Mean weight of patients who presented complications was not significantly different from patients without complications. When adverse events were separately evaluated, there has been significant association with the following risk factors: (1) Pruritus - females (Fisher's Exact test, p < 0.01) and chest surgeries (Chi-square test p < 0.01); (2) Nausea and vomiting - females (Fisher's Exact test, p < 0.001) and children (Chi-square test, p < 0.001); (3) Sleepiness - chest surgeries (Chi-square test, p < 0.01) and thoracic catheter (Fisher's Exact test, p < 0.02); (4) Urinary retention - hip and knee arthroplasties (Chi-Square test, p < 0.001) and lower limb surgeries (Chi-square test, p < 0.01); (5) Epidural Catheter Disconnection and Externalization - males ( Fisher's Exact test, p < 0.05) and patients' weight above 70 kg (Student's t test, p < 0.05). Patients with catheter disconnection or externalization had mean weight of 70 kg against mean weight of 62 kg for patients without this complication. Although without statistical significance, there has been a trend to associate thoracic catheter positioning to pruritus. Table VI and table VII show the incidence of adverse events with continuous epidural infusion of bupivacaine, epinephrine and fentanyl according to risk factors.
Optimal epidural analgesia technique should promote effective pain relief with minor adverse events and major patients' satisfaction, in addition to allowing favorable evolution with shorter hospital stay 18,20. Epidural analgesia is effective for pain relief not only with patient at rest but also during movement and cough. Postoperative attenuation of surgical stress response, free movement on bed, early ambulation and effective cough should be clinical objectives of the analgesic technique since they allow for faster recovery by decreasing complication rates 1,4,6,7,10-12,14,21-25.
Epidural analgesia with the association of local anesthetics and opioids promotes better analgesia as compared to epidural or systemic opioids alone 6,22,26-30 and to epidural local anesthetics alone 22,31-36. This association allowed decreased local anesthetic concentration of the epidural analgesic solution and lower opioid doses needed for better postoperative analgesia with less adverse events as compared to the use of one or other agent 12,21,22,31-40.
Fentanyl is highly liposoluble, thus with a faster binding to spinal nervous tissue and epidural fat, and faster absorption by epidural blood vessels. The consequence is a segmental action with shorter duration as compared to less liposoluble opioids. This way, CSF concentration is more rapidly decreased with limited rostral spread and lower risk for respiratory depression and other adverse events 12,16,41-43. Clinical and experimental studies 43-46 have confirmed the fentanyl spinal analgesic effect, although other studies with high epidural fentanyl doses (1 to 5 µg.kg-1.h-1) have suggested also a supraspinal action due to its systemic absorption. This spinal effect allows for decreased minimum local bupivacaine concentration, thus optimizing analgesia 42,44,47.
Optimal fentanyl concentration in epidural analgesic solution is not known. A wide range of opioid doses has been used alone or in combination with local anesthetics 22,30,34,48. Curatolo et al. 49, however, have studied with optimization methods the optimal combination of bupivacaine, fentanyl and clonidine doses in different infusion rates, in continuous epidural infusion for postoperative analgesia of patients submitted to high and low abdominal surgeries through xipho-pubic laparotomy. After several combinations, they have found three regimens with similar efficacy - 0.9 mg.mL-1 bupivacaine and 3.3 µg.mL-1 fentanyl at 9 mL.h-1; 1.3 mg.mL-1 bupivacaine, 3 µg.mL-1 fentanyl and 0.7 µg.mL-1 clonidine at 7 mL.h-1; and 1.4 mg.mL-1 bupivacaine and 2.8 µg.mL-1 fentanyl at 9 mL.h-1.
The association of epinephrine to the epidural solution decreases fentanyl absorption 47,50, allowing for more opioid to reach the spinal cord. It has also been shown in animal models that spinal epinephrine induces analgesia through an a2-adrenergic mechanism. So, even if epinephrine analgesic effect in our epidural solution (1 µg.mL-1) was minor it might have caused a synergistic analgesic effect when combined to bupivacaine and fentanyl 9,45,51.
Accurate epidural catheter positioning on dermatomes that will be the target of surgical injury is critical to assure analgesia quality and also to allow the administration of lower bupivacaine and fentanyl doses with lower incidence of adverse events 3,52 and motor and sympathetic block of lower limbs. Epidural analgesia has a segmental effect related to injection site, local anesthetic volume and opioid liposolubility.
In our study, epidural infusion of 0.1% bupivacaine, 1 µg.mL-1 epinephrine and 3 µg.mL-1 fentanyl has promoted satisfactory postoperative analgesia. Although being impossible a direct comparison due to different methods, other studies have shown similar results 12,21,53,56.
In the first postoperative day, 80.1% of patients referred no pain or mild pain (scores 0 to 3). From remaining patients, 12.9% had moderate pain (scores 4 to 6) and 7% severe pain (scores above 7). These data show a better profile as compared to what has been shown by Dolin et al. 57 in their review of pain scores reported in the literature after major surgeries. Although not classified as meta-analysis, their findings may represent the daily routine of Postoperative Pain Management Services. Dolin et al. 57 have reported incidences of 20.9% (17.8 - 24)% and 7.8 (6.1 - 9.5)% of moderate-severe and severe pain, respectively, with continuous epidural infusion for postoperative analgesia.
In the second postoperative day, 92.8% of patients had adequate analgesia and this percentage was maintained in the third postoperative day (93.3%). Approximately 1/5 of patients needed increased epidural infusion rate in the first 24 hours, characterizing inadequate analgesia. This large number of patients reflects the major importance of close monitoring in the postoperative period to optimize postoperative analgesia.
Adequate postoperative pain control might have been of capital importance for the high level of patients' satisfaction at treatment completion (97.2%). Satisfaction analysis however is complex and influenced by several postoperative management aspects, such as analgesic effectiveness, incidence of adverse events and patients acknowledgment for the care they received.
On the other hand, as shown in our study, high postoperative pain control success rate was due to close and constant follow up both by the Postoperative Pain Management Group and the nursing staff. This is a task demanding time and care for patients' evaluation and possible adjustments on epidural infusion rate.
Adequate analgesia was followed by safety since severe complications, such as respiratory depression, epidural hematomas or abscesses were few or none. Although a seemingly high incidence of adverse events was observed (46.3%), most of them were minor and without severity. Among general adverse events, that is, related to infused drugs, most common problems were urinary retention (26.8%), nausea and vomiting (17.7%) and pruritus (7%). Only 8 patients (1.7%) were sleepy.
In our study there has been one case of respiratory depression (0.2%), which is possibly the most feared complication with spinal opioids. Hydrophilic opioids, such as morphine, are slowly absorbed and remain for a longer time in CSF with consequent higher cephalad spread and may cause late respiratory depression. The risk for respiratory depression increases in elderly and obese patients when opioids are administered through other routes in addition to spinal route 58,59. In addition to the type of opioid (lipophilic or hydrophilic), dose is also important and is related to respiratory depression. It is an uncommon complication with incidence varying 0.24% to 1.6% 23,53,56,60,61. It is important to stress that respiratory depression is often followed by sedation 53,62. So, periodic monitoring of respiratory rate and consciousness level should be maintained throughout epidural analgesia for early respiratory depression detection.
Total epidural catheter-related complications were 25.4% from all analgesic technique-related complications. Catheter injector disconnection and catheter tip externalization corresponded to 80% of epidural catheter-related complications.
Our data (11.1% externalization and disconnection) are in line with literature findings 53,54,56,63. Scott et al. 47 and Burstal et al. 56 have reported 13% catheter displacements, while Liu et al. 54 have reported 12%. Other authors have reported lower incidences, varying 1.6% to 7.4% 60,64,65. Dolin et al. 57 in their review have found 5.7% (4 to 7.4%) epidural catheter displacement.
There have been no cases of epidural catheter migration to spinal space or of local anesthetic toxicity due to migration to epidural veins. However, catheter fixation is important to prevent migration or exit from the epidural space with consequent epidural analgesia failure.
Patient's movement and epidural catheter attrition against the bed may result in displacement of a previously well-positioned catheter. Hamilton et al. 66 have shown in a study with pregnant women that epidural catheter was displaced toward the epidural space when patient would go from the sitting flexed position to the lateral position without spinal bending. This effect was even more significant in obese patients. So, if epidural catheter is fixed with patient still in the flexed position, catheter may be stretched and leave the epidural space resulting in epidural analgesia failure. Hamilton et al. 66 have found in their study that mean epidural catheter displacement varied from 0.67 to 1.04 cm, having reached 4.28 cm in an obese patient. Better care with catheter displacement should be taken when epidural space puncture is performed in the lateral position, considering Hamza et al. 67 findings, who have shown a longer distance from skin to the epidural space when puncture is performed in the lateral position as compared to the sitting position.
Deep infections, such as meningitis and epidural abscesses, associated to epidural catheter vary in the literature zero to 0.7% 68-72. There have been no epidural abscesses in our study. However, we consider that the number of evaluated patients was too small to evaluate the incidence of this uncommon complication. On the other hand, the incidence of superficial infections is not known since they are not thoroughly evaluated. It is estimated that their incidence is similar to intravenous lines infection rates. In our study, just 4 patients (0.9%) presented inflammation signs, with erythema and edema, followed or not by serum or pus discharge at catheter insertion site. This low incidence may reflect the short period of epidural catheter permanence in our study (mean of 2.2 days). However, due to severe consequences of epidural abscesses, it is our approach to remove any catheter causing inflammatory signs at the insertion site. Inflammatory signs have appeared both in the beginning of postoperative analgesia (2nd postoperative day - one patient) and later (6th postoperative day -one patient; 8th postoperative day - two patients). These patients presented positive epidural lavage fluid and/or catheter tip without however clinical signs of epidural abscess. Three of those patients had been submitted to thoracotomies and their catheters were inserted in the thoracic position. Cultured bacteria, however, were organisms normally present on skin (Staphylococcus epidermidis, Staphylococcus haemolyticus and Staphylococcus aureus), One patient, victim of firearm wound on left foot evolving with infection, presented Acinetobacter calcoaceticus growth on catheter tip. Infected foot wound presented growth of several pathogens which, however, were different from that isolated on the catheter tip. Epidural catheter may act as a niche for infection, and bacteria may reach epidural space through hematogenic route as from a distant infection site. So, it is convenient to evaluate in a case-by-case basis the risk/benefit ratio of using epidural analgesia in patients with distant infection 73. Strict vigilance should be maintained for early epidural infection detection 74.
Many catheters have positive culture after being removed. Possible cause would be their contamination by the colonized skin around the insertion site. The vast majority of those patients will not present clinical signs of epidural abscess, suggesting that routine catheter tip culture is irrelevant for epidural abscess diagnosis. The very low incidence of epidural abscesses has not decreased the importance of strict preventive measures, among them: (1) Aseptic technique with the use of caps, masks, and sterile gloves; (2) adequate skin disinfection before epidural puncture. It has been shown that 0.5% alcohol chlorhexidine is better than 10% iodinated Povidine®, leading to less frequent and slower epidural catheter contamination 75; (3) Decrease epidural catheter permanence time. In some studies, permanence time has been a risk factor for catheter infection. Bevacqua et al. 76 have found that catheters remaining in place for 96 hours or less were not associated to local or spinal infections. Conversely, Kee et al. 77 and Kindler et al. 71 have found that most epidural abscesses have occurred within five days of in situ epidural catheter permanence; (4) Prepare epidural solutions under strict aseptic technique, preferably at the hospital's pharmacy; (5) Since epidural catheter injector is the major colonization source 78,79, it is necessary to use bacterial filters and limit the number of system manipulations, keeping it closed during the course of analgesia 70,80; (6) Use adhesive, transparent and moisture patent dressings. This way it is possible to regularly observe catheter insertion site in search for inflammation signs 70. Shapiro et al. 81 have concluded that chlorhexidine-containing dressings have decreased catheter colonization rate; (7) daily check catheter insertion site for early infection detection. A high level of suspicion should be maintained, considering the possibility of epidural abscess in the differential diagnosis, and promptly removing the epidural catheter. Kindler et al. 71 have found that time interval between first epidural abscess symptoms and treatment has been significantly longer in patients with persistent neurological deficits.
Inflammatory signs may also be due to allergic reaction to catheter material. Although being made of hypoallergenic materials, Mather et al. 82 have reported 6 cases of skin reactions to epidural catheter. In these cases, however, manifestations were not exclusively at insertion site, but also along catheter fixation pathway on patients' back.
In our study, there have been no cases of epidural infusion withdrawal due to analgesic failure or adverse events severity. Different studies have shown different results on epidural analgesia failure 53,55,56,63,83-87, may be as a function of different methods and definitions of analgesic failure. Our data have shown that epidural catheter-related complications were responsible for all early epidural analgesia withdrawals (13.9%). Catheter injector disconnection and catheter externalization were present in 80% of cases.
Clinical guides and quality programs are critical for postoperative pain management improvement 88. Postoperative Pain Management Group should be in charge of establishing pain control protocols, of educating nursing staff so that postoperative pain evaluation be as routine as the checking of vital signs; and of periodically evaluating the quality of postoperative analgesia offered to our patients 89,90.
There are few studies in the literature evaluating risk factors for the incidence of epidural analgesia adverse events and complications 54,86,91. Our study has identified as potential risk factors patients age (< 16 years), weight (> 70 kg), type of surgery and thoracic catheters.
Nausea and vomiting were present in 17.7% of patients. Literature describes different incidences, varying 2.8% to 40% 53,56,64,83,84,90. Pruritus, in our study, has been probably underestimated since symptom would not cause discomfort to patients, although they have been actively asked about its incidence. This may explain major differences in the literature on the incidence of pruritus 12,53,56,69,83,84,90-92.
Females, in addition to slightly higher incidence of adverse events, were associated to a higher incidence of pruritus, nausea and vomiting. Similarly, Liu et al. 55 have identified significant correlation between female gender and the incidence of sleepiness, nausea and vomiting.
There has also been a significantly higher incidence of nausea and vomiting in children. May be there is a bias in this case as to the type of general anesthesia. While children have received pure inhalational anesthesia, adults were predominantly submitted to balanced anesthesia.
Different studies in the literature use different definitions to evaluate sleepiness and, for such, different incidences are reported 12,53,54,83,90. Our data are possibly underestimated and are especially related to patients presenting deeper sedation.
Chest surgeries were significantly associated to higher incidence of pruritus and sleepiness. Similarly, thoracic epidural catheters were related to higher incidence of sleepiness with higher trend to pruritus. As shown by Liu et al. 54, the explanation for those findings might be the higher epidural solution dose needed for analgesia after thoracic surgeries. Differently from Liu et al. 54, we have not found correlation between pruritus and patients' age.
Urinary retention was significantly more frequent in lower limb surgeries and hip and knee arthroplasties. Possible cause of this association might have been longer time in bed without walking and depending on nursing care.
Patients' weight (> 70 kg) and male gender, probably for higher body mass, were significantly associated to higher incidence of epidural catheter disconnection and externalization. Higher body mass may lead to more catheter movement, favoring its displacement 66.
Postoperative epidural analgesia is in general effective and safe. Our study has shown adequate analgesia in 80% of patients in the first postoperative day, with high level of satisfaction at treatment completion. Adverse events although frequent were not severe, and no severe complications were seen. Some risk factors have been identified. Children, female gender, chest and lower limb surgeries and arthroplasties were significantly associated to the incidence of such adverse events.
However, this high success rate is directly dependent on strict patients vigilance and follow up. Inadequate analgesia and epidural infusion side effects should be early identified and corrected, in addition to preventing the incidence of severe complications. The Postoperative Pain Management Group should be involved in improving the care of patients receiving epidural infusion, in addition to developing treatment protocols and educating professionals and patients.
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Dr. Leonardo Teixeira Domingues Duarte
SQSW 306, Bl E Ap 304, Sudoeste
70673-435 Brasília, DF
Submitted for publication April 2, 2003
Accepted for publication September 19, 2003
* Received from Hospital SARAH, Brasília