Postoperative continuous plexular analgesia: a study on the side effects and risk factors of catheter infection

Abstracts

JUSTIFICATIVA E OBJETIVOS: A analgesia pós-operatória foi muito valorizada nos últimos anos. Os cateteres plexulares são boa opção para analgesia de qualidade com a mínima repercussão sistêmica. O presente estudo visou a avaliar a ocorrência de efeitos colaterais e complicações em analgesia pós-operatória com cateteres plexulares e identificar fatores de risco para colonização bacteriana nos cateteres. MÉTODO: Pacientes submetidos a operações ortopédicas entre março de 2005 e janeiro de 2007 receberam analgesia por cateteres de plexo. Foi avaliada a ocorrência de efeitos colaterais e de complicações com o uso da técnica. Em parte dos casos foi feita cultura da ponta do cateter. RESULTADOS: Foram estudados 433 pacientes. As incidências de retenção urinária e náuseas/vômitos foram de 1,3% e 16,6%, respectivamente. Houve colonização em 8,6% dos 280 cateteres examinados. Não houve infecções, lesões nervosas nem repercussões sistêmicas. CONCLUSÕES: O uso pré-operatório de antibióticos e o tipo de agulha utilizado foram fatores de risco para colonização dos cateteres.

ANESTESIA, Regional; COMPLICAÇÕES; TÉCNICAS ANESTÉSICAS, Regional

SCIENTIFIC ARTICLE

Postoperative continuous plexular analgesia. A study on the side effects and risk factors of catheter infection^*

Analgesia postoperatoria plexular continua. Estudio de los efectos colaterales y de riesgo de infección de los catéteres

Juliano Rodrigues Gasparini, TSA, M.D.^I; Sérgio Silva de Mello, TSA, M.D.^II; Ronaldo Soares Marques, TSA, M.D.^III; Renato Ângelo Saraiva, TSA, M.D.^IV

^IAnestesiologista da Rede SARAH de Hospitais de Reabilitação; Instrutor do CET Hospital Universitário São José

^IIMestre em Ciências da Reabilitação; Anestesiologista da Rede SARAH de Hospitais de Reabilitação

^IIIAnestesiologista da Rede SARAH de Hospitais de Reabilitação

^IVDoutorado em Medicina (Cirurgia Cardiovascular); Coordenador da Anestesiologia da Rede SARAH de Hospitais de Reabilitação

Correspondência para

SUMMARY

BACKGROUND AND OBJECTIVES: The importance of postoperative analgesia has increased over the years. Plexular catheters represent a good option for high quality analgesia with reduced systemic repercussions. The objective of the present study was to evaluate the incidence of side effects and complications in postoperative analgesia with plexular catheters and identify risk factors for bacterial colonization of the catheters.

METHODS: Patients undergoing orthopedic surgeries between March of 2005 and January of 2007 received analgesia via plexular catheters. The incidence of side effects and complications of this technique were evaluated. In some of the cases, the catheter tip was cultured.

RESULTS: Four hundred and thirty-three patients were evaluated. Urinary retention and nausea/vomiting had an incidence of 1.3 and 16.6%, respectively. Of 280 catheters examined, 8.6% were colonized. Infections, nerve lesions, or systemic repercussion were not observed.

CONCLUSIONS: The use of antibiotics preoperatively and the type of needle were the risk factors of infection identified.

Key Words: ANESTHESIA, Regional; ANESTHETIC TECHNIQUES, Regional: peripheral blocks; COMPLICATIONS: infection.

RESUMEN

JUSTIFICATIVA Y OBJETIVOS: La analgesia postoperatoria fue muy estimada en los últimos años. Los catéteres plexulares son una buena opción para la analgesia de calidad con una mínima repercusión sistémica. El presente estudio quiso evaluar la incidencia de efectos colaterales y complicaciones en analgesia postoperatoria con catéteres plexulares, e identificar factores de riesgo para la colonización bacteriana en los catéteres.

MÉTODO: Pacientes sometidos a operaciones ortopédicas entre marzo de 2005 y enero del 2007 que recibieron analgesia a través de catéteres de plexo. Se evaluaron la incidencia de los efectos colaterales y las complicaciones con el uso de la técnica. En una parte de los casos, se efectuó el cultivo de la punta del catéter.

RESULTADOS: Fueron estudiados 433 pacientes. La incidencia de retención urinaria y náuseas/vómitos fue de 1,3 y de un 16,6%, respectivamente. Hubo colonización en un 8,6% de los 280 catéteres examinados. No hubo infecciones, lesiones nerviosas, ni tampoco repercusiones sistémicas.

CONCLUSIONES: El uso preoperatorio de antibióticos y el tipo de aguja utilizado fueron factores de riesgo para la colonización de los catéteres.

INTRODUCTION

Humanization of Anesthesiology includes postoperative analgesia ^1-5. Several techniques are used with good results, but the search for improvements is constant. The perfect technique would be associated with: absence of postoperative pain, side effects, and counter indications; applicability to any type of patient and any age; low cost; easy to perform; and completely safe. The perfect technique is still a goal to be achieved.

The technique of analgesia using a catheter placed near peripheral nerve plexuses has excellent perspectives. Plexular catheters for analgesia (PCA) in surgeries of the upper and lower limbs offer good postoperative analgesia, increased patient satisfaction, and have a positive influence on the results of the surgery and rehabilitation when compared with intravenous opioids ^6,7. Plexular catheter analgesia also provides longer lasting analgesia with fewer side effects than intravenous morphine, patient-controlled analgesia, and epidural analgesia ^8-10.

The present study evaluated the incidence of side effects and complications of PCA in a Hospital of the Rede SARAH de Hospitais de Reabilitação, the Unidade de Belo Horizonte, in the state of Minas Gerais, Brazil, in orthopedic surgeries. It also tried to identify risk factors associated with bacterial colonization of plexular catheters used for analgesia maintenance.

METHODS

After approval by the Ethics Council of the Institution and signing of the informed consent by the patients or legal guardians, patients of both genders undergoing orthopedic surgeries of the upper or lower limbs from March 2005 to January 2007 were included in the study.

Patients were evaluated in the Anesthesiology outpatient clinic, at which time the technique of PCA was explained to them and they signed the informed consent. All patients underwent plexular analgesia adequate for the surgical procedure (associated with general anesthesia or sedation).

The interscalene technique approaches the brachial plexus anteriorly, in the sulcus between the anterior and middle scalene muscles, at the level of the cricoid cartilage (Winnie, 1970). The infraclavicular approach to the brachial plexus was described by Wilson ^11,12. The axillary approach to the brachial plexus was described by Jong in 1961. The landmark described by Mello¹³ was used to place the catheter near the lumbar plexus. The approaches used for the sciatic nerve included: the approach described by Labat (known as the classical approach), lateral (Pandin) ¹⁴, and in the lateral aspect of the thigh (described by Zetlaoui and Bouaziz, called popliteal) ¹⁵.

At the time of the procedure, the anesthesiologist was wearing a double-face mask and a cap. His hands were washed with chlorhexidine. He then put on sterile disposable gloves. The skin of the patient was cleaned with a 0.5% alcohol chlorhexedine solution and sterile pads three times, with light friction. A fenestrated sterile field was placed over the area of the blockade.

A sterile set of disposable short bevel needles (Contiplex D, B Braun) or Tuohy tip needles (Contiplex T, B Braun) with a catheter and electrical isolation were used. The plexus was identified using a peripheral nerve stimulator (Stimuplex DIG RC, B Braun). After identifying the exact location of the needle (adequate motor response with a current of 0.5 mA, or lower, and 2 Hz stimulus frequency), an adequate volume and concentration of the local anesthetic solution (ropivacaine without vasoconstrictor or bupivacaine with vasoconstrictor) was administered. The catheter was then introduced. A test dose of 1 mL of the local anesthetic solution was injected through the catheter to identify possible obstructions. It was up to the anesthesiologist to decide whether a bacterial filter (0.2 nm) should be placed.

The skin at the site of catheter insertion was cleaned with sulfuric ether and covered with a transparent dressing (Tegaderm, 3M).

The anthropometric data of the patient, date of the surgery, preoperative comorbidities, use of drugs that could interfere with the immunologic system (corticosteroids, non-steroidal anti-inflammatories, immunosupressors), antibiotics, potential of surgical contamination, surgical site, position of the catheter, use of bacterial filter, number of attempts until the catheter was properly placed, type of needle, and anesthetic solution used were recorded on a standardized form.

Postoperatively, patients were seen at least twice by a member of the anesthesiology team. The following parameters were evaluated during the period the catheter remained in place: presence or absence of motor blockade in the operated limb, signs of systemic intoxication by local anesthetics (metallic taste, auditory or visual changes, seizures, decreased level of consciousness, cardiovascular changes); nausea, vomiting; pruritus; hypotension (20% drop in preoperative levels); or urinary retention. The site of catheter insertion was also examined to detect signs of inflammation, secretion or bleeding, changes in catheter placement, and the condition of the dressing. The dressing protecting the catheter was changed only if it was getting lose or in case of local bleeding.

Analgesic solutions were administered in the morning (around 6:30 a.m.) and late in the afternoon (around 6:30 p.m.). An analgesic solution with 0.5% ropivacaine without vasoconstrictor or 0.3% bupivacaine with vasoconstrictor was administered each time. The volume administered depended on the age and weight of the patient, and on the site of the catheter. The anesthetic solution for analgesia was prepared at the bedside, without sterile gloves, face mask, or cap. Disposable needles and syringes were used. Administration was done without sterile gloves or sterilization of the tip of the syringe. If the patients complained of pain in the interval between the administration of local anesthetic, they were treated with systemic analgesics (dypirone, paracetamol, sodium diclophenac, or tenoxicam, tramadol, or morphine), according to the prescription.

The catheter was removed whenever the patient remained pain free for 12 hours (Visual Analogue Scale of zero).

The following were defined as complications: presence of signs indicative of infection or inflammation at the site of insertion, neurologic changes, pain on injection or fever. Accidental removal of the catheter, failure of analgesia, and disconnection of the bacterial filter were defined as incidents.

The tip of the catheters was also submitted to bacteriological investigation. In this case, the dressing was removed with ether. Cleaning solutions were not applied to the skin after the dressing was removed. The catheter was mobilized with sterile tweezers. It was removed carefully, avoiding contact with the skin. The tip of the catheter (the proximal 1 cm) was cut off with sterile scissors, placed in a sterile container, and sent immediately to the bacteriology lab.

The date of catheter removal was recorded for all patients, regardless of whether its tip was sent for culture or not, as well as the reason for removal, the presence of complications or incidents, and hyperemia and/or secretions (specifying the type) at the insertion site.

Catheters sent to the lab were rolled on Petri dishes with blood-agar. Afterwards, the tips were dipped in a liquid culture media (thioglycolate). Petri dishes were incubated at 35°C (± 2°C) for 24 hours. In case of lack of bacterial growth, they were incubated for another 24-hour period. If, after 48 hours, no growth was observed, the Petri dishes were discarded. Thioglycolate was used to detect possible fungal colonization. Cultures in the Petri dishes were considered positive if they presented more than 15 colony-forming units (CFU). If more than 15 CFU were present, a series of biochemical tests was performed to identify the type of bacteria. If the liquid media became turbid, and fungal growth confirmed, the culture was considered positive.

Patients with positive cultures were evaluated to detect local and systemic signs of infection. After this clinical evaluation, ultrasound or CT of the insertion site was done to identify possible collections.

Initially, the data was analyzed with descriptive statistics. A preliminary analysis with the Chi-square and Odds Ratio (OR) tests indicated possible candidates for risk factors or protection of bacterial colonization. Factors with a statistical association, with a 95% confidence level, were selected for the logistic model whose function was to verify the role of each risk factor on bacterial growth. The statistical test L= -log (probability) is an estimation of maximal probability. The lower the value of L the higher the capacity of the logistic model to predict the risk of bacterial growth. The software SSPS 10 for Windows was used to analyze the data.

RESULTS

Four hundred and thirty-three patients were initially included in the study. Among them, 18 patients were excluded because proper catheter positioning was not possible. Of the 415 patients with correct catheter placement, 87% were placed on the first attempt, 10% on the second, and 3% in three or more attempts. Seventeen additional patients were excluded due to the accidental removal of the catheter without the necessary care to collect its tip for culture.

Table I shows the anthropometric data of the remaining 398 patients.

Table II

Nausea and/or vomiting were the most frequent side effects (66 patients - 16.6%). Five patients (1.3%) developed urinary retention requiring a urinary catheter for relief. Four patients (1.1%) required prolonged use of the urinary catheter. There were no cases of pruritus.

Hypotension (a 20% drop of baseline levels) or respiratory depression (respiratory rate below 10 bpm) were not observed. Sensitive or motor changes in the anesthetized limb, suggesting nerve lesion, were not detected.

In one case (0.25%), the interscalene catheter migrated into the intravascular space. On the second dose of anesthetic (10 mL of 0.5% ropivacaine), the patient developed a reduction in the level of conscience after 4 mL had been injected. The administration was interrupted and the patient regained consciousness in less than 30 seconds. During this period he did not have changes in cardiac rhythm. Radiological study with the administration of NS and contrast showed the catheterization of a small neck vein in the interscalene muscle.

Postoperative antibiotics were used in 272 patients (68.3%). It was classified as: prophylactic, single preoperative dose, in 13 patients (3.3%); prophylactic for 24 hours in 230 patients (57.8%); and therapeutic in 28 patients (7.0%). Three-hundred and thirty-seven surgeries (84.7%) were considered to be clean, 32 (8.2%) potentially contaminated, and 28 (7.1%) as infected. A bacterial filter was used in 54.6% (n = 217) of the catheters. Eight patients (2.0%) were making use of drugs that could interfere with the immunologic response, including non-steroidal anti-inflammatories (NSAIDs) regularly (two patients), antihistamines (two patients), corticosteroids (three patients) and a combination of metothrexate, prednisone, and NSAID (one patient) (Table III).

Two hundred and eighty catheters were cultured. Twenty-four (8.6%) showed growth of more than 15 CFU. Liquid culture mediums were negative for fungus. Patients with positive cultures were not taking drugs that could interfere with the immunologic response (Table IV).

Those patients were followed for at least five months and did not have any complaints or signs of inflammation at the insertion site. Late postoperative CTs (five patients) and ultrasounds (19 patients) did not show any anatomical changes suggestive of collection or abscess close to the trajectory of nerve plexuses.

Only one microorganism was isolated in 19 cultures, while two bacteria were identified on the remaining five cultures. Microorganisms identified included: S. epidermidis (n = 11; 45.3%), S. hemolyticus (n = 1; 4.2%), Acinetobacter calcoaceticus-baumanii complex (n = 3; 12.5%), Gram-positive rod (n = 2; 8.3%), Pseudomonas aeruginosa (n = 2; 8.3%), Serratia mascescens (n = 1; 4.2%), Enterobacter cloacae (n = 1; 4.2%), Enterococcus faecalis (n = 2; 8.3%), and Proteus mirabilis (n = 5; 20.8%).

In the preliminary phase, a statistical association among bacterial growth and the following risk factors was detected: use of antibiotic (at least one dose - OR = 0.26; CI 0.11 to 0.61; ÷² = 9.234; p = 0.002), type of needle (Tuohy tip: OR = 5.41; 2.16 to 13.57; ÷² = 13.721; p < 0.001), and use of bacterial filter (OR = 0.22; 0.06 to 0.76; ÷² = 0.624; p = 0.018).

The logistic model with three factors was tested (L = 138.908), but the use of the bacterial filter did not show statistical significance (p = 0.555).

A second logistic model with the use of antibiotics, type of needle, and the interaction between them was adjusted (L = 130.052), but the interaction was not significant (p = 0.636) and was removed.

The probability of the model composed of two factors: use of antibiotics (p = 0.002) and type of needle (p < 0.001) was similar to the initial model (L = 139.274; p = 0.833), and, therefore, it was chosen. Besides having less parameters then prior models, it presented better performance than the model that considered only the type of needle (L = 149.072). The model allowed the determination that the incidence of bacterial colonization was lower with the short beveled-needle and at least one dose of antibiotics (2.4%) and higher with the Tuohy tip and absence of antibiotics (33.3%).

DISCUSSION

Postoperative analgesia is evolving. A large amount of knowledge has been produced and disseminated in this field. With the improvement of the technique, drugs, and equipment, Anesthesiology is in a stage that it can provide postoperative pain control regardless of the size of the surgery, filling a gap that did not have a satisfactory solution, especially considering the dexterity and safety achieved by surgical anesthesia.

Analgesia catheters can be considered a landmark in analgesia. Epidural catheters were the first ones. They gained acceptance and are widely used with good results. But for surgeries of the limbs, plexular catheters represent a good choice.

Catheter placement is not difficult; it was not successful in only 18 patients (4.2%), and most of them occurred at the beginning of the study. As the team became more knowledgeable with the material used, the number of failures decreased. Similar success rates have been reported in the literature ^16-18. The learning curve for this catheter is fast. The experience acquired by members of the team with peripheral blocks contributed for those indexes.

The incidence of side effects of the catheter is lower than intravenous and continuous epidural analgesia. All side effects are lower than in intravenous analgesia ^6,7,9,19. The incidence of pruritus, urinary retention, respiratory depression, hypotension, and sedation are lower than with epidural analgesia ^8-10,20.

The reduced incidence of side effects can be attributed to the opioid in the intravenous and epidural analgesic solution. The solution used in PCA contained only local anesthetic.

Every analgesia technique has complications and inherent risks. If intravenous and epidural analgesia have side effects caused by the opioids, catheters (in the subarachnoid space or close to plexuses) will always be subjected to migration, nerve lesions, anesthetic intoxication, and infectious complications.

The incidence of catheter migration is low with epidural catheters ^23,24. Migration of the plexular catheter occurred in the present study and it is also reported in the literature ¹⁶.

Epidural catheters have an incidence of 0.02% of persistent neurologic lesions ²⁵. Capdevilla et al. reported a 6.7% incidence of neurologic changes (paresthesias, hypoesthesia, and motor blockade) during analgesia with plexular catheters ¹⁶. Those symptoms seem to be caused by the infusion of local anesthetic. Those symptoms disappeared after termination of the technique except for three cases (0.2%) whose symptoms resolved in up to 10 weeks. Anyway, the estimated incidence of nerve lesions of PCA is low ¹⁶. Nerve lesions were not observed in the present study.

Wang et al. estimated a 0.05% incidence of epidural abscess, and between 5.8 and 45.8% incidence of bacterial colonization of epidural catheters ^25-27. Capdevilla et al. and Morin et al. reported colonization rates of 28.7% and 23.5% ^16,28. The same authors reported an incidence of 0.07% and 13.7% of local catheter infection. In the present study an incidence of 8.6% of catheter colonization was observed but infection was not diagnosed in any of those cases.

The lower incidence of catheter colonization can be attributed to differences in study methods. Capdevila et al. considered the growth of colony formation units regardless of their number, what might have contributed to the increase in positive cases ¹⁶. On the other hand, Morin et al. used the same criteria (> 15 CFUs), and observed similar incidence of colonization as Capdevila et al. ²⁸ who used only short bevel needles ¹⁶. If only the cases of colonization associated with short-bevel needles are considered, the incidence in the present study was even lower (3.8%).

The use of 0.5% alcoholic chlorhexedine for antisepsis of the skin before the block and catheter placement is one of the factors that could have contributed for a better result. Chlorhexedine seems to be superior to the iodine and alcohol solution used in other studies ^29-31.

It is also surprising that other authors took precaution measures that were not used in the present study, such as the use of sterile gown when inserting the catheter, and antisepsis of the skin at the time of catheter removal ^16,28.

The results of the present study reinforce that the use of at least one dose of antibiotics is an important protective factor. Capdevilla and Morin indicated the same. It was not possible to identify the length of stay of the plexular catheter as a risk factor for colonization, which might be related to the size of the cohort. The use of the bacterial filter was a protective factor in the present study.

The Tuohy-tip needle was an important factor to increase the incidence of catheter colonization. It had an incidence of 17.2% in the cases in which the Tuohy needle was used. Greater tissue trauma during the introduction of the needle could explain such large difference.

The number of patients in this study could also be another limitation. Although the study population is a true representation of the surgical movement of the Institution, mathematical models of linear regression are more precise with larger samples. Therefore, it is possible that important parameters for the study of bacterial colonization of PCAs were not identified. It should be mentioned that the type of needle (short-beveled needle vs. Tuohy tip) was not subjected to random distribution.

In the present study, the prophylactic use of at least one dose of antibiotics and the use of short-beveled needles were identified as factors associated with a reduction in the risk of bacterial colonization of catheters used in postoperative continuous plexular analgesia.

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*

Recebido da Unidade de Belo Horizonte da Rede SARAH de Hospitais de Reabilitação, Belo Horizonte, MG

Publication Dates

• Publication in this collection
  14 Nov 2008
• Date of issue
  Dec 2008

History

• Received
  11 Dec 2007
• Accepted
  26 Aug 2008