The development of instruments and methods to provide long-term venous access for IV administration of various agents has been a critical component of improved medical care over the past 35 years. Although the first long-term IV catheters were described1 for parenteral administration of nutrients, investigation into other uses of these catheters, including repeated collection of blood samples, plasmapheresis, and the IV administration of drugs (eg, chemotherapeutic agents, analgesics, and antimicrobials) and blood products, has increased.2–5
The use of totally implantable SVAPs has further advanced the means by which venous access is achieved and maintained.5–9 The SVAP was introduced as an alternative to other continual venous access systems, including vascular grafts, arteriovenous fistulas, and catheters with extracutaneous injection ports.2,10,11
Proposed benefits of SVAPs include minimization of pain associated with repeated venipuncture, decreased rates of bacterial infection when compared with those for nonimplanted catheter systems, and reduced impairment of activity during nontreatment times.5,9,11 Use of the SVAP is thought to be particularly beneficial in oncological patients because these patients often receive IV administration of chemotherapeutic agents, require repeated collection of blood samples during periods of hematologic monitoring, and are more susceptible to bacterial infection.2,3,6,7,9–12
Complications associated with SVAPs in human patients are variable. Investigators in 1 study13 reported complication rates as high as 39%. However, the reporting of complications is not uniform and reports of complications are often organized on the basis of the particular device or component of the devices used. Common complications include bacterial infection, thrombosis, catheter migration, drug extravasation, catheter occlusion, and pneumothorax.2,4,7,9,11,13,14
In laboratory animal medicine, SVAPs are commonly used in cats, monkeys, rabbits, and swine to allow for procedures that require repeated blood collection during periods of hematologic monitoring and intermittent or continuous IV infusions.15–21 In these animals, it is essential that vascular access is regularly maintained and is not compromised by improper manipulation of a percutaneous catheter or insufficient vessel integrity.
The use of SVAPs in veterinary patients has been uncommonly reported. Investigators in 1 study22 evaluated perioperative complications associated with SVAPs; the most commonly reported complications were seroma formation, malpositioned catheters, and suture breakage. In another study,23 investigators compared the use of percutaneous catheters and SVAPs in 20 dogs treated with radiotherapy; there were fewer complications and shorter surgical times in the percutaneous catheter group, compared with results for the SVAP group. All wound (eg, swelling and bruising) complications in both groups were self-limiting events, and complete resolution was detected within a 7-day period.23 Additionally, studies24–26 have evaluated the use of SVAPs for repeated blood collection during periods of hematologic monitoring in cats and dogs and during blood donation in cats.
Information is insufficient regarding the complication rate and risk factors for the development of complications in cats and dogs with SVAPs undergoing treatment with fractionated radiotherapy. The purpose of the study reported here was to describe complications associated with the use of SVAPs in cats and dogs undergoing treatments with fractionated radiotherapy and to determine predisposing factors for developing these complications.
Materials and Methods
Case selection—Medical records of cats and dogs examined at the Matthew J. Ryan Veterinary Hospital of the University of Pennsylvania between 1996 and 2007 were reviewed. Cats and dogs that underwent surgical placement of an SVAP for use during treatment with fractionated radiotherapy were identified.
Medical records—Data retrieved from medical records included species, breed, age, body weight, sex, vein catheterized (femoral or jugular), SVAP location (right or left), surgical technique for SVAP placement, anesthetic drugs administered into the SVAP, whether the SVAP was used to administer chemotherapy, total number of times the SVAP was used, maximum number of days per week the SVAP was used, number of days the SVAP was functional, dose of radiation delivered, and type of neoplasia being treated with fractionated radiotherapy. Major and minor complications were recorded. Major complications were defined as permanent loss of SVAP catheter patency, catheter breakage, drug extravasation, suture breakage, infection, and incision dehiscence. Minor complications were defined as difficulty accessing the SVAP, seroma formation, and catheter positioning that resulted in temporary loss of catheter patency. For a subset of these cases, the anesthesia report was available, and surgery time and anesthesia time for SVAP placement were recorded.
Procedures—Each cat or dog was placed in lateral recumbency, and the surgical site was shaved, aseptically prepared, and surgically draped in preparation for placement of 1 of 2 commercially available SVAPs.a,b A 3- to 5-cm vertical incision was made a few centimeters dorsal to the jugular vein on the lateral neck. The subcutaneous tissue was bluntly and sharply dissected to form a pocket in which the SVAP was placed. Once placed in the pocket, the SVAP was sutured to the surrounding subcutaneous tissue or dermis. The indwelling catheter was attached to the SVAP, and the port was flushed with saline (0.9% NaCl) solution before being infused with a locking solution (90% gentamicinc and 10% heparind).
Catheter placement in a jugular vein by use of a venotomy technique
A trocar was used to create a tunnel from the lateral aspect of the neck to a jugular vein. An incision (1 to 3 cm) was made parallel to the jugular vein. The jugular vein was isolated, and 2 encircling sutures of 3-0 silke were placed around the jugular vein. The cranial suture was secured tightly around the jugular vein. A No. 11 scalpel blade was used to incise a 2-mm hole in the jugular vein. The catheter was flushed with saline solution and the locking solution. The catheter was then passed through the tunnel in the subcutaneous tissue created by the trocar and advanced into the hole in the jugular vein. The caudal suture was secured tightly around the jugular vein-catheter combination. Both the SVAP site and venotomy site were closed by use of a 2-layer suture technique.
Catheter placement in a jugular vein by use of a peel-away sheath technique
Each cat or dog was prepared for surgery as described, and the SVAP was placed as described for the venotomy technique. A stab incision was made in the skin over a jugular vein. A 20-gauge over-the-needle catheterf was inserted percutaneously into the jugular vein. A guidewire (diameter, 0.018 inches) was advanced through the catheter into the jugular vein, and the over-the-needle catheter was removed. An indwelling 5F catheterg equipped with a peel-away sheath was flushed as previously described, connected to the SVAP, and advanced over the indwelling guidewire into the jugular vein. The peel-away sheath was progressively removed as the catheter was advanced into the jugular vein. The SVAP site was then closed by use of a 2-layer suture technique.
Catheter placement in a femoral vein
All SVAP catheters were placed in a femoral vein by use of the peel-away sheath technique as described for catheter placement in the jugular vein. The SVAP was placed in a pocket created in the subcutaneous tissue on the dorsolateral aspect of the abdomen. The SVAP site was then closed by use of a 2-layer suture technique.
Statistical analysis—Data were analyzed by use of statistical analysis software.h Descriptive statistics were calculated for the data recorded. Continuous data were expressed as median values and ranges. Categorical data were expressed as frequencies. For cohorts in which complete medical and anesthetic records were available, logistic regression analyses were performed to evaluate the association between predisposing factors and major and minor complications. Univariate analysis was performed initially, and factors analyzed by use of a Wald test with a P value < 0.20 were tested in each model. Factors were retained in the model on the basis of a Wald test P value ≤ 0.05. Fitness of the overall model was evaluated by use of the Hosmer-Lemshaw statistic.
Results
Signalment and history—Criteria for inclusion were met by 46 cats and 126 dogs. Cat breeds included domestic shorthair (n = 36), domestic longhair (4), Siamese (3), Burmese (1), Himalayan (1), and Maine Coone (1). Dog breeds included mixed-breed dog (n = 51), Labrador Retriever (14), Golden Retriever (11), Boxer (7), Cocker Spaniel (4), German Shepherd Dog (3), Miniature Schnauzer (3), Shih Tzu (3), Sharpei (2), Airedale Terrier (1), American Staffordshire Terrier (1), Bassett Hound (1), Beagle (1), Bearded Collie (1), Bedlington Terrier (1), Borzoi (1), Boston Terrier (1), Brittany (1), Chihuahua (1), Dalmatian (1), Doberman Pinscher (1), English Springer Spaniel (1), German Shorthaired Pointer (1), Giant Schnauzer (1), Great Dane (1), Great Pyrenees (1), Greyhound (1), Husky (1), Keeshond (1), Maltese (1), Pomeranian (1), Pug (1), Shetland Sheepdog (1), Standard Poodle (1), Tibetan Terrier (1), Weimaraner (1), and West Highland White Terrier (1). Mean ± SD age of cats and dogs was 10 ± 3.4 years and 9 ± 2.8 years, respectively. Mean weight of cats and dogs was 4.9 ± 1.2 kg (10.8 ± 2.6 lb) and 26.5 ± 12.9 kg (58.3 ± 28.4 lb), respectively. There were 25 castrated male cats and 21 spayed female cats. There were 52 castrated and 9 sexually intact male dogs and 63 spayed and 2 sexually intact female dogs.
Catheter placement—Information regarding the vein catheterized (n = 3 cats and 5 dogs), catheter location (3 cats and 4 dogs), and surgical technique (19 cats and 56 dogs) was not available for all animals. Catheters were placed in the femoral or jugular vein in 4 and 160 animals, respectively. Fifty-nine catheters were placed on the left side, and 106 catheters were placed on the right side. A peel-away sheath technique was used in 63 animals (n = 17 cats and 46 dogs), and a venotomy technique was used in 34 animals (10 cats and 24 dogs).
SVAP usage—The SVAP was used for IV injection of drugs for induction of anesthesia. Propofol administered alone or in combination with butorphanol, diazepam, etomidate, glycopyrrolate, ketamine, lidocaine, midazolam, oxymorphone, and thiopental or administration of various combinations of diazepam, etomidate, ketamine, midazolam, oxymorphone, and thiopental was used to induce anesthesia in the animals of the present study. Anesthesia reports for SVAP placement were available for 160 animals (n = 41 cats and 114 dogs induced with propofol alone or in combination with other drugs and 3 cats and 2 dogs induced with combinations of drugs not including propofol). Data were not normally distributed for surgery and anesthesia time, total number of times and number of times per week the SVAP was used, and number of days the SVAP was functional; thus, only the median value was reported. Surgery and anesthesia time ranged from 15 to 175 minutes (median, 50 minutes) and 45 to 260 minutes (median, 100 minutes), respectively. The SVAP was used for IV injection of chemotherapeutic drugs in 6 of 172 animals (4 cats and 2 dogs). The total number of times and number of times per week the SVAP was used ranged from 0 to 13 times (median, 11 times) and from 0 to 3 times/wk (median, 3 times/wk), respectively. The number of days the SVAP was functional ranged from 0 to 159 days (median, 25 days).
Neoplasia treated with fractionated radiotherapy—Palliative and full-course radiotherapy were performed in 3 and 169 cases, respectively. Number of radiation treatments ranged from 2 to 13 (median, 12). Total dose of radiation ranged from 8 to 52 Gy (median, 48 Gy). The type of neoplasia being treated by use of radiotherapy in cats included fibrosarcoma (n = 15), adenocarcinoma (11), lymphosarcoma (8), squamous cell carcinoma (6), angiolipoma (1), angiosarcoma (1), hemangiosarcoma (1), malignant fibrous histiocytoma (1), mast cell tumor (1), and plasmacytoma (1). The type of neoplasia being treated by use of radiotherapy in dogs included mast cell tumor (n = 43), peripheral nerve sheath tumor (29), adenocarcinoma (13), fibrosarcoma (13), uncategorized soft tissue sarcoma (10), squamous cell carcinoma (6), malignant fibrous histiocytoma (3), chondrosarcoma (2), myxosarcoma (2), carotid body tumor (1), liposarcoma (1), neurofibroma (1), osteosarcoma (1), and perianal adenoma (1).
Complications and predisposing factors—Complications were typified as major (n = 18) or minor (36; Table 1). Major complications included animals in which there was permanent loss of catheter patency (n = 9), inadvertent removal of the catheter (4), suture breakage (2), infection (1), catheter breakage (1), and dehiscence of the incision made for placement of the SVAP (1). Minor complications included patient positioning that caused temporary loss of catheter patency (n = 21), seroma formation (12), and difficulty accessing the SVAP (3).
Characteristics of major and minor complications resulting from SVAP placement in 46 cats and 126 dogs.
| Variable | Category | Major complications* | Minor complications† | ||
|---|---|---|---|---|---|
| Yes (n = 18) | No (n = 154) | Yes (n = 36) | No (n = 136) | ||
| Species‡ | Cat | 7 (39) | 39 (25) | 10 (28) | 36 (26) |
| Dog | 11 (61) | 115 (75) | 26 (72) | 100 (74) | |
| Age range (y)§ | Cat | 5.1–12.7 (8.4) | 1.7–14.3 (10.5) | 5.1–13.8 (9.5) | 1.7–14.9 (10.5) |
| Dog | 4.8–15.4 (8.3) | 1.5–16.2 (8.8) | 3.1–15.4 (8.9) | 1.5–16.2 (8.5) | |
| Sex of cat‡ | Female | 5 (28) | 16 (11) | 4 (11) | 17 (12) |
| Male | 2 (11) | 23 (15) | 6 (17) | 19 (14) | |
| Sex of dog‡ | Female | 6 (33) | 59 (38) | 18 (50) | 47 (35) |
| Male | 5 (28) | 56 (36) | 8 (22) | 53 (39) | |
| Body weight (kg)§ | Cat | 3.8–5.9 (4.4) | 2.2–7.5 (5) | 3.1–7.4 (5.3) | 2.2–7.5 (4.6) |
| Dog | 12.1–70.4 (32) | 3.3–60 (27) | 5.3–49.5 (32) | 3.3–70.4 (26) | |
| Vein catheterized‡∥ | Jugular | 14 (93) | 146 (98) | 33 (94) | 127 (98) |
| Femoral | 1 (7) | 3 (2) | 2 (6) | 2 (2) | |
| Catheter locationঠ| Left | 9 (60) | 50 (33) | 11 (31) | 48 (37) |
| Right | 6 (40) | 100 (67) | 24 (69) | 82 (63) | |
Major complications were defined as permanent loss of catheter patency, catheter breakage, inadvertent removal of the catheter, suture breakage, infection, and incision dehiscence.
Minor complications were defined as difficulty accessing the SVAP, seroma formation, and temporary loss of patency attributable to catheter or patient positioning.
Value reported is number (percentage).
Value reported is range (median).
Vein catheterized was not recorded for 3 cats and 5 dogs.
Catheter location was not recorded for 3 cats and 4 dogs.
Of the animals with major complications, 8 (including 4 with inadvertent catheter removal, 2 with breakage of suture attaching the SVAP to the subcutaneous tissue, 1 with dehiscence, and 1 with permanent loss of catheter patency) required a second surgery to correct the major complication. The SVAP and catheter were removed and not replaced in the other 10 animals (8 with permanent loss of catheter patency, 1 with infection, and 1 with catheter breakage). Animals with minor complications did not require a second surgery to correct the complication.
Univariate analysis revealed that factors associated (P < 0.2) with major complications included sex (P = 0.090), SVAP location (P = 0.150), and lack of propofol administration during the induction of anesthesia (P = 0.030). Multivariate analysis revealed that sex (P = 0.015) and the administration of propofol during the induction of anesthesia (P = 0.030) were significantly associated with major complications. When controlling for propofol administration, female cats and dogs were 5.00 times as likely as male cats and dogs to develop major complications (95% CI, 1.01 to 24.49; P = 0.048). When controlling for sex, animals not receiving propofol were 19.15 times as likely as those receiving propofol to develop major complications (95% CI, 1.78 to 206.38; P = 0.015). Univariate analysis revealed that factors associated (P < 0.2) with minor complications included sex (P = 0.068) and SVAP location (P = 0.150). By use of multivariate analysis and by controlling for vein placement, female cats and dogs were 3.44 times as likely as male cats and dogs to develop minor complications (95% CI, 1.13 to 10.48; P = 0.030). When controlling for sex, SVAPs placed in the femoral vein were 17.20 times as likely as SVAPs placed in the jugular vein to result in minor complications (95% CI, 1.31 to 225.38; P = 0.020).
Discussion
The use of fractionated radiotherapy for the treatment of neoplasia in cats and dogs is commonplace. The delivery of fractionated doses of radiotherapy requires multiple anesthetic episodes that may be performed several times each week. Repeated catheterization of a blood vessel can result in loss of vascular patency, increased patient discomfort, and possibly an increase in the rate of bacterial infection.27 The goal in the use of a long-term vascular access device is to prevent some of these potential problems.
Complications encountered with the use of SVAPs and long-term catheters have been extensively detailed in the human literature. Studies22,23,25,26,28 in which investigators evaluated complications that occur with the use of these devices in veterinary patients have identified sepsis, abscesses, edema at the port site, port occlusion, seroma formation, breakage at the port-catheter junction, port migration, port suture breakage, and port erosion as potential complications.
Complications identified in the cats and dogs treated with fractionated radiotherapy in the study reported here were categorized as major and minor complications. Minor complications were predominated by seroma formation and the inability to use the SVAP when the patient was in a particular position. In the 21 animals that had complications resulting from animal positioning that caused the temporary loss of catheter patency, movement of the patient's neck (for an SVAP placed in the jugular vein) or hind limb (for an SVAP in a femoral vein) resulted in proper functioning of the SVAP. To prevent this complication, we recommend that the excess length of the catheter be used for the formation of a loop; this loop should be large enough to allow the neck or leg of each animal to be in any position and still maintain catheter function and patency.
In another report,22 seroma formation was the most common (30.4%) postoperative complication. Seroma formation was the second most common complication of the study reported here, developing in 12 of 172 (7%) animals. Care should be taken during surgery to properly place the sutures attaching the SVAP to prevent seroma formation, which may delay use of the SVAP. Other techniques that may be used to prevent seroma formation include reduction of the size of the pocket formed during dissection of the subcutaneous tissues and placing a sufficient number of sutures to decrease the dead space of the subcutaneous tissue pocket. However, aggressive treatment of a seroma can generally resolve this complication within a few days after onset.22
Permanent loss of catheter patency was the most common major complication and accounted for 17% (9/54) of all complications (major and minor). However, the cause of the loss of catheter patency was not recorded. In humans, catheter thrombosis and the formation of a fibrin sheath resulting in loss of patency account for 16% to 30% of complications encountered.14,27,29,30 It has been determined in humans that the further the catheter tip is from the distal portion of the superior vena cava and heart, the more likely that a thrombus will form.29,30 Angiographic studies to assess the location of the point of obstruction were not routinely performed, and catheter tip location was not assessed postoperatively in the study reported here. Additionally, the use of urokinase or streptokinase, which is commonly reported7,11,31 in human patients for the dissolution of clots, was not attempted in the cats and dogs of the present study.
Of the 172 animals, 8 (4.7%) animals had a major complication that required a second surgery for replacement of the SVAP. Furthermore, complications that rendered the SVAP unusable occurred in another 10 (5.8%) animals. Owners of cats and dogs undergoing fractionated radiotherapy, to whom an SVAP is recommended, should be informed of these risks. However, these complication rates are relatively low and should not preclude the use of these devices as the benefits likely outweigh the risks.
An association was not detected between the development of complications and age, body weight, or breed of the cats or dogs. However, with multivariate analysis, female cats and dogs were 5 times as likely and 3.44 times as likely to develop major and minor complications, respectively, as were male cats and dogs. In several human studies,27,32 sex has not been found to be a risk factor for the development of complications. It is difficult to postulate the reason that females were more likely to develop complications in the study reported here. Certain types of neoplastic disease are more common in female patients and may predispose these patients to complications. In the present study, neoplastic diseases treated with fractionated radiotherapy were evaluated to determine if they predisposed females to complications. However, the type of neoplasia did not influence the development of complications.
Propofol is an effective anesthetic induction agent in cats and dogs.33 Its use in repeated short-duration anesthetic procedures for fractionated radiotherapy in cats has been evaluated.34 In the study reported here, propofol was the most common injectable medication administered during the induction of anesthesia, and a major complication was significantly less likely to be associated with animals in which propofol was administered. Propofol allows for smooth induction,33 which may result in decreased motion during induction of anesthesia in veterinary patients. Perhaps there was more struggling during induction of anesthesia in the animals that did not receive propofol, which resulted in increased opportunities for the loss of catheter patency, catheter and suture breakage, or catheter extravasation. Propofol is also rapidly excreted,33 and animals that received propofol in the present study may have recovered more quickly, which again would have resulted in better protection of the catheters and SVAPs.
Feasibility of the use of SVAP catheters inserted in a femoral vein has been evaluated in cats and dogs.25 In that study,25 SVAP placement in the femoral vein was considered a good alternative with high owner satisfaction, compared with the results for SVAP placement in a jugular vein. In the study reported here, animals with an SVAP inserted in a femoral vein were more likely to develop minor complications. Fewer SVAPs were placed in the femoral vein; it may be likely that a lack of experience in the placement of SVAPs in the femoral vein resulted in a higher number of complications, compared with the number of complications for SVAPs inserted in a jugular vein. Additionally, the constant motion of the hind limb during typical activities may cause alterations in the position of the catheter or result in seroma formation at the surgery site.
Key limitations of the present study were identified. Although it can be theorized that loss of catheter patency was the result of thrombosis or fibrin sheath formation, catheters were not evaluated for these problems. Investigations to determine the cause of the loss of catheter patency should be pursued in the future, and the use of thrombosis dissolution medications may be considered in veterinary patients. Additionally, when the SVAPs were removed, swab specimens of the catheter and SVAP sites were not obtained and submitted for bacterial culture. Only 1 bacterial infection was diagnosed for the animals reported here. However, the true frequency of infection in these animals has not been determined. Another limitation is that the technique used to insert the SVAP and the surgeon performing the placement of the SVAP were not uniformly distributed or randomized among the animals reported here. Finally, these animals were monitored closely and generally were examined at least 3 times/wk. However, medical records were evaluated retrospectively; it is possible that some information could have been omitted, which may have resulted in an underestimation of the true incidence of complications during SVAP use.
The placement of SVAPs in cats and dogs for use during treatment with fractionated radiotherapy appears to be a useful alternative to multiple catheterizations. The complication rate is low, and corrective surgery was only necessary in a small number of animals. Administration of propofol during the induction of anesthesia and the placement of SVAPs in a jugular vein should also be considered because of a potential lower risk of developing complications, compared with the risk of developing complications associated with the lack of administration of propofol during the induction of anesthesia and placement of an SVAP in a femoral vein. Because of the findings of the present study, SVAP placement could also be considered for other animals that may require repeated anesthetic episodes.
ABBREVIATIONS
| CI | Confidence interval |
| SVAP | Subcutaneous vascular access port |
Infus-A-Port, Infusaid, Norwood, Mass.
CompanionPort, Norfolk Vet Products, Skokie, Ill.
Phoenix Scientific Inc, St Joseph, Mo.
Hospira Inc, Lake Forest, Ill.
Ethicon Inc, Somerville, NJ.
Veni-Systems Clear Cath, Abbott Laboratories, Sligo, Ireland.
Norfolk Vet Products, Skokie, Ill.
Stata, version 10, StataCorp, College Station, Tex.
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