SURGICAL NOTE. Surgical Recommendations to Optimize Femoral/Iliac Artery Cannulation

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1 SURGICAL NOTE Surgical Recmmendatins t Optimize Femral/Iliac Artery Cannulatin Due t its size, lcatin, and ease f access, the femral artery is frequently used fr bld pressure catheter placement. Less frequently, the catheter is inserted directly int an iliac artery. Bth f these appraches prvide accessible anatmic lcatins t allw fr high quality bld pressure signals with gd lngevity. This placement can cause sme limitatins t the bld flw t the catheterized limb due t the physical presence f the catheter in the upstream bld vessel, and/r the ligatin f the femral artery mre distally. This cmprmise in bld flw t the limb may ptentially induce a hindlimb paresis/paralysis in the catheterized limb, and can ccur with femral artery cannulatin r direct cannulatin f the iliac artery. There are a variety f factrs that increase the risk f this cmplicatin. These factrs will be discussed belw, alng with pssible means t mitigate the risk. Surgical Technique Damage t the femral nerve, and/r extensive dissectin culd als cause pst-perative cmplicatins. Careful surgical techniques can help decrease the risk f cmplicatins: Ensure that n nerves are damaged during dissectin (avid grasping the nerve with any instruments) and ensure that it is nt included in ligatin. Use minimal dissectin, but ensure that enugh artery is expsed t allw fr easy catheter insertin. Take care with instruments such as retractrs t avid further damage t tissue r nerves. Animal Size A smaller [bdy weight] animal is mre likely t experience hindlimb cmplicatins assciated with an upstream catheter. Sme facilities have established a minimum size required t supprt the placement f a hindlimb catheter based upn their histrical perspective. DSI suggests a 4 kg minimum in NHP and an 8 kg minimum in canine and swine as a starting pint with mdificatins based n experience in yur animal ppulatin. Intra-perative Bld Pressure Hyptensin (mean arterial bld pressure lwer than 60 mm Hg) during surgery predispses t hindlimb cmplicatins. The animal may be dependent n bld flw thrugh cllateral bld vessels due t the ligated/partially bstructed upstream artery, and hyptensin decreases bld flw t [smaller] peripheral bld vessels. In rder t mitigate hyptensin, it is critical t btain an accurate assessment f the patient s bld pressure.

2 Indirect methds include dppler flw and scillmetric, which is mre accurate. Bth methds require accurate cuff placement and sizing (cuff width 40% f the limb diameter). Direct bld pressure mnitring via an arterial line is the mst accurate methd. Live telemetry data cllectin during surgery will allw fr an extremely accurate assessment f bld pressure (and heart rate and arrhythmias) nce the arterial catheter is placed. Hwever, depending n the length f surgery, telemetric bld pressure measurements may nt be available until late in the prcedure. Therefre, sme ther methd t measure bld pressure shuld be used until this time. Even the mst accurate equipment wn t help if there is nt a dedicated anesthetist wh frequently mnitrs vital signs (including bld pressure) and clsely tracks and respnds t trends. There are a variety f means t maintain adequate bld pressure under general anesthesia. The veterinary and surgical team shuld cnsult prir t the surgery t develp a plan, and ensure all supplies, such as fluid therapy and ptential rescue medicatins are readily available during surgery. Having dses and infusin rates fr imprtant medicatins pre-calculated can be invaluable in case f an emergency. Ptential interventins include, but are nt limited t: Maintain inhalatinal anesthesia at an apprpriate level (i.e. MAC t 1.3 MAC) Adequate pre-medicatin and/r intra-perative cntinuus rate infusins (CRI) (e.g. piid, lidcaine, etc.) can help decrease the required MAC. Prvide fluid therapy Istnic crystallids fr maintenance (e.g. 0.45% NaCl r Lactated Ringers), and may be blused as needed. Additives may be used as needed (e.g. dextrse, etc.). Cllids maybe used t expand the intravascular space if crystallids are ineffective at maintaining bld pressure. Supprt with psitive intrphs may be added if needed t maintain BP, and are typically administered as a CRI (e.g. dpamine, dbutamine, phenylephrine, nrepinephrine). Surgical Duratin Increased surgical time can cause prlnged hyptensin and decreased bld flw t the affected limb. All steps shuld be taken t maximize surgical efficiency t decrease surgical time, withut cmprmising the quality. During cmplex surgeries mre than ne surgen may be able t wrk n different anatmical lcatins at the same time (e.g. ne surgen wrks n the jugular vein while the ther surgen accesses the femral artery). Having skilled assistants is als helpful t expedite the surgery. Planning ahead t ensure all necessary supplies are easily accessible is als critical t avid unnecessary delays.

3 It is beneficial t perfrm a dress rehearsal prir t a survival surgery t ensure the entire team is fully prepared. This may invlve a table-tp exercise withut an actual animal, r an acute surgery, if apprpriate resurces are available. Supplemental Patient Warming Hypthermia will cause further vascnstrictin, particularly f the patient s extremities. This culd pssibly exacerbate the vascnstrictive effects due t hyptensin under anesthesia. There are a variety f patient warming systems available fr veterinary surgery. They shuld be used thrughut anesthesia (including during animal preparatin and recvery), and adjusted t maintain a nrmal bdy temperature. The mst effective systems maintain clse cntact with the animal, and effectively and evenly cntrl temperature t prevent ht spts and patient burns. Over the cunter heating pads designed fr human use are cntraindicated in veterinary patients, as they are likely t cause burns. Cmmercially available systems include: Frced-air warming (e.g. Bair Hugger, SurgiVet Equatr Cnvective Warming System, etc.) Electrical cnductive fabric warming (e.g. Ht Dg Warmer, ChillBuster, etc.) Recirculating water pads Patient Psitining Extensive pressure arund the distal limb (i.e. unpadded/excessively tight restraints) can lead t hindlimb cmplicatins such as ischemic necrsis distal t the restraint. Likewise, excessive tensin placed n the limb can cause damage t the nerves. The minimum amunt and duratin f hindlimb restraint shuld be used during surgery. Alternatives t hindlimb restraints, such as vacuum-assisted patient psitining devices shuld be used whenever pssible t psitin limbs. When necessary, padded restraints specifically designed fr patient use shuld be used, rather than rpes. Restraints shuld be placed as lsely as pssible arund the limbs and cntact between the restraint and the limb shuld be spread ut as much as pssible. The minimum required amunt and duratin f tensin shuld be used. Tensin shuld nly be emplyed during the prtin f the surgery when it is needed. Befre, and after it is required, all tensin shuld be released. It can be helpful fr the anesthetist t keep track f when tensin is applied, and help remember t discntinue as sn as pssible.

4 Implant Selectin Because hindlimb cmplicatins can be seen with bth femral and iliac artery catheter insertins, this issue is likely in part due t upstream partial cclusin f bld flw. The smallest diameter catheter that is apprpriate fr the species and applicatin shuld be selected. Catheters typically used fr large animal implantatin have a 1.4 mm diameter and are available in a variety f lengths, up t 40 cm. Smaller diameter catheters (0.7 mm diameter) are available n sme large animal implant cnfiguratins, and have a maximum length f 15 cm. Pst-perative Cmfrt In rder t maximize bld flw and the develpment f cllateral bld supply t the hindlimb and prevent disuse atrphy and/r limb cntracture, animals shuld return t nrmal psture and activity levels as sn as pssible after surgery. Any uncntrlled pain experienced by the animal will preclude this gal. A well-cnceived peri-perative analgesic plan will help the animal return t nrmal functin and activity mre quickly pst-peratively. The veterinary and surgical team shuld cnsult prir t surgery t develp a multimdal plan which may include: Pre-perative analgesic and anti-inflammatry medicatins t prevent wind-up pain. Lcal anesthetic agents Pst-perative patient mnitring cnsidering the use f an ethgram t quantify behaviral changes related t pain. Pst-perative analgesic prtcl, tailred t individual animal needs Cnsider the use f sustained release r lnger lasting medicatins t decrease stress assciated with administratin. Evaluatin f Cmplicatins Shuld hindlimb cmplicatins ccur, it is imprtant t thrughly evaluate them t learn and hpefully prevent them in the future. Whenever pssible, the surgical team shuld be invlved in this assessment. Factrs t lk fr include: Evidence f thrmbsis/fibrsis in situ alng the catheter length r near the catheter tip. If the vessel is ligated, it is nrmal fr a thrmbus t frm and fr the vessel t fibrse near the ligatin pint. This thrmbsis/fibrsis typically extends t the level f a majr side branch (which serves t preserve bld flw). It is abnrmal fr the thrmbsis/fibrsis t extend prximal t a large side-branching vessel. Damage t/ligatin f the nerve.

5 Cmplete [r substantial] cclusin f the bld vessel by the catheter (i.e. a mismatch between the diameter f the catheter and the diameter f the artery). Anesthetic recrds can be reviewed t determine: Episdes and duratin f hyptensin Effectiveness f any interventins attempted Duratin f anesthesia Duratin f tractin n the hindlimb Any ther cmplicating factrs