IntroductionA central line is defined by the placement of the cathetertip into the cranial or caudal vena cava, or the right atrium.
It may bereferred to as a central venous catheter (CVC) or a central venous line (CVL),and may be inserted through a peripheral vein or a proximal central vein (Smith& Nolan, 2013). Central venous catheterisation is highly researched in humanmedicine, however, few studies have been executed in veterinary medicine. Thepurpose of this literature review is to explore the issues of central venouscatheterisation and which aspects are relevant from a veterinary nursing perspective. The most commonplacement of a central line in cats and dogs is the cranial vena cava via the externaljugular vein (Silverstein & Hopper, 2014). The jugular vein provides astraighter route to the superior vena cava and is preferred to the femoralvein.
The femoral vein carries a higher risk of venous thrombosis and isassociated with a higher rate of infectious complications (Merrer et al. 2001).The higher incidence for catheter-related infections with the femoral vein maybe due to the higher density of skin flora in the groin region (Bozzetti et al.,1982). A peripherally inserted central catheter (PICC) is also a viable option.
PICC lines may be placed through thelateral saphenous vein in dogs, and less commonly through the medial saphenousvein. The medial saphenous vein is used in cats as it is larger and easilystabilised (Silverstein & Hopper, 2014). The veterinary nurse’s role in central vein catheterisationis important regarding aseptic preparation of the site and daily maintenancecare of the catheter. The skin and hair of an animal are a potential source ofinfection at the catheter insertion site. In human medicine, there are setguidelines for skin preparation prior to intravenous catheterisation. However,this is less explored in veterinary medicine studies. Coolman et al. (1998) comparedskin disinfection protocols in dogs by examining clinical, microbiological, andhistopathological changes between disinfected and non-disinfected catheterinsertion sites.
The study highlighted the importance of thorough skinpreparation using chlorhexidine gluconate to significantly reduce bacterialnumbers. IndicationsCentral lines are often necessary in veterinary hospitals tomaintain reliable vascular access, especially in the treatment of criticallyill patients. Indications include emergency venous access, central venouspressure monitoring, rapid fluid infusion, parenteral nutrition, repeatedvenous blood sampling, delivery of critical medications, poor peripheral venousaccess, or for long-term venous access (Ku & It, 2014). In Ku and It’sstudy, the most common reason for CVC was fluid infusion (44%), followed by 28%of patients receiving a CVC for poor peripheral access and 24% for drugadministration.
CVCs may have two orthree infusion ports making them preferable over peripheral catheters foradministration of incompatible solutions and continued central venous pressure(CVP) monitoring during fluid administration. CVCs are also usually bettertolerated by patients.Central venous pressure monitoring is used to monitor andguide fluid therapy. An increase in CVP may indicate cardiac failure,pneumothorax, volume overload, pulmonary oedema, pulmonary thromboembolism andpulmonary hypotension (Silverstein & Hopper, 2014). It is therefore aneffective monitoring technique and leads to appropriate nursing care ofcritically ill patients. CVP is useful in monitoring fluid resuscitation ofhypovolaemic animals and in diuretic therapy of overhydrated patients(Charlambous et al.
, 2003).Fluids and why cant be peripheralParenteral nutrition involves the infusion of glucose,lipids and amino acids intravenously. Central venous access is required becauseparenteral nutrition is given as a hypertonic solution, which cannot beadministered peripherally as it would damage the vessel (Macdonald, Master& Moffitt, 1977). Parenteral nutrition may be necessary in animals unableto eat and veterinary nurses play a significant role in ensuring the patient’snutritional requirements are met.Venous blood samplingPoor peripheral access reasons Contraindicationsfor CVL (procedures pro printout) Indications for catheter removal include completion oftherapy, thrombosis, phlebitis if not responsive to corrective treatment,catheter site infection that did not respond to local treatment, and patientdeath (Merrell et al., 1994).
Indications for Catheter Removal Indication Patients No. % Treatment Completed 249 64.0 Death 54 13.
9 Fever 25 6.4 Occlusion 14 3.6 Phlebitis 12 3.1 Ruptured catheter 10 2.
6 Bacteremia or fungemia 8 2.1 Local infection 6 1.5 Transfer to other facility 4 1.0 Patient pulled out 3 0.8 Thrombosis 2 0.5 Unknown 2 0.5 Total 389 100.0 (Merrell, S.
W., et al., 1994. ‘Peripherally InsertedCentral Venous Catheters – Low-risk Alternatives for Ongoing Venous Access’, The Western Journal of Medicine, p 28,table) Complications andManagementCentral lines may be vital in the treatment of criticallyill patients; however, CVC placement may lead to serious complications. It isimportant for the veterinary nurse to recognise these complications in order togive the highest standard of care. If ideal aseptic conditions were not met,e.g.
during an emergency, the catheter may need to be replaced as soon aspossible to avoid infection (Lorente et al., 2005). Central line management isrequired to recognise and prevent complications.
Management is also probablythe most significant aspect of central venous catheterisation for veterinarynurses as they hold a lot of responsibility in daily care. This includesmaintenance and cleaning of the catheter site, bandage removal and changes,inspecting the site for signs of infection and alerting veterinary staff to anycomplications. Health and safety and infection control procedures are keyaspects in veterinary nursing so the care and knowledge a veterinary nursebrings to central line maintenance is indispensable. Complications ofcentral venous catheterisation may be mechanical, infectious, or thrombotic innature (Merrer et al., 2001). Mechanical ComplicationsThe most common mechanical complications include arterialpuncture, haematoma, and pneumothorax (Devi et al., 2017). Venous air embolism isprobably the most feared complication of central venous catheterisation, with amortality rate of 29-50% (Thielen & Nyquist, 1991).
Cardiac perforationsand cardiac arrhythmias may also occur and are due to the catheter beingadvanced into the walls of the right atrium (Ku & It, 2014). This can beprevented through careful placement by an experienced veterinary physician.Yildizeli et al. (2004) found in their study that catheter tip malposition wasthe most frequent perioperative problem. Most catheter tips were located in theright ventricle and had to be repositioned.
Variables that may affect thelikelihood of mechanical complications include operator experience, the time ittakes to place the central line, and if the catheter is inserted during thenight (operator may be fatigued or inexperienced) (Merrer et al., 2001). InMerrer et al.’s study, mechanical complications occurred in 52 of the 289patients assessed, predominantly arterial punctures, minor bleeding andhaematomas.
In Mansfield et al.’s research, failure of catheterisation wasassociated with the following factors: prior surgery in the region ofcatheterisation, previous attempts at catheterisation, surgeon carrying out theprocedure was inexperienced, overweight patients, and more than two needleinsertion attempts. Mechanical complications may be reduced by the operatorbeing skilled and experienced, keeping the number of attempts to a minimum, andultrasonographically guided central venous access.Venous air embolism: Pneumothorax: This is when air has entered the pleural cavitythrough an opening of the lung surface or chest wall and causes the lung tocollapse. It is one of the most severe complications of central venouscatheterisation.
After CVCplacement, a thoracic radiograph should be taken to confirm correct positioningof the central line and possible pneumothorax. However, a pneumothorax may notbe immediately apparent on x-ray. Therefore, if pneumothorax is suspectedfurther radiography should be carried out a few hours after placement. Pneumothorax may necessitate placement of achest drain, which was the case for 6 patients in Sitzmann et al.’s study butall resolved without further complications. The following are signs ofpneumothorax and the nursing care that should be provided: Dyspnoea -Monitor respiratory rate, report tachypnoea, and administer oxygen. Oxygendesaturation of arterial blood – Monitor oxygen saturation with a pulseoximeter, administer oxygen, and have equipment prepared for thoracocentesis.
Wheezingor coughing – Place animal into sternal recumbency, monitor breathing, andbe prepared for oxygen administration and possible chest drain placement(Drewett, 2000).Arterial puncture:Haematoma: Infectious ComplicationsOne of the most notable complications of CVC placement iscentral line-associated bloodstream infection (CLABSI). There are many sources of infections including contamination ofthe catheter hub, contamination of the catheter before insertion, organismspresent on the patient’s skin, bacterial spread from a nearby wound, andcontaminated fluids or medications (Coolman et al., 1998). It is important to understand the infectious risksparenteral nutrition may have on the patient. Microorganisms may be introducedinto parenteral nutrition infusates during manufacturing, preparation, orduring delivery, and could cause infection in the patient (Bozzetti et al.
,1990).Sitzmann et al. (1985) found that for suspected cathetersepsis the patient would meet certain criteria: pyrexia, recorded bacteraemiaor fungemia, purulent discharge from catheter insertion site, or systemic signsof sepsis. If a patient showed one or more of these signs blood cultures wereobtained from the central line and from peripheral veins, and if returnedpositive the central line was removed or replaced over a guidewire. In thisstudy, 63 catheters were removed for suspected sepsis, with or withoutreplacement, and only 15 of these catheters transpired to be the source ofsepsis. There was also a correlation between the number of catheterisationattempts (the number of times the needle was passed through the skin) andsepsis, with septic patients having an average of 2.1 attempts which is muchhigher than the average number of attempts in the non-septic category. Thrombotic ComplicationsThe choice of catheter material is important as some aremore thrombogenic than others.
The femoral vein should be avoided as there is ahigher risk for deep vein thrombosis. In Merrer et al.’s research they found21.5% of patients with a femoral catheter had catheter-related thrombosis. Central line care is vital to minimise catheter-relatedblood stream infection and perhaps the most effective method of reduction ishand hygiene.
Other important measures include: aseptic catheter maintenancetechnique, type of cleansing solution, infusion set changes, type of dressing,number of access ports, and maintaining a closed system to avoid airintroduction. UltrasonographyUltrasound guidance………However, in Mansfield et al.’s study they found ultrasoundguidance had effect on the reduction of complications, with problems occurringin 40 patients from the control group and 40 from the ultrasound group.
Theyconcluded that this could be down to the fact many different physicians carriedout catheterisation and some may be more experienced in the use of ultrasoundguidance.