Indications and principles for medical management Medical therapy is the treatment of choic e for: \200 uncomplicated type B dissection \200 stable isolated arch dissection \200 chronic ( > 2 weeks \200\231 duration) stable type B dissection. In all but those patients who are hypotensive, initial management is aimed at reducing systemic blood pressure and m yocardial contractility. The goal is to stop spread of the intramural haematoma and to prev ent rupture. The best guide is control of pain. Strict bed rest in a quiet room is essentia l. AORTIC DISSECTION: MANAGEMENT 771 Control blood pressure Reduce systolic BP to 100 \200\223120 mmHg. \200 Start on IV B -bl ocker (if no contraindications), aiming to reduce the heart rate to 60 \200\22370/min (see box, b p.772). Once this is achieved, if blood pressure remains high, add a vasodilator such as sodium nit roprusside (see box opposite). Vasodilators in the absence of B-blockade may increase myoca rdial contractility and the rate of rise of pressure (d P /d t ). Theoretically, this may p romote extension of the dissection. Further antihypertensive therapy may be necessary, and other conventional agents such as calcium-channel blockers, B -blockers, and ACE-Is can be used. In patients with aortic regurgitation and congestive cardiac failure, myocardial depressants should not be given. Aim to control BP with vasodilators only. Hypotension may be due to hemorrhage or cardiac tamponade. \200 Resuscitate with rapid in travenous volume (ideally colloid or blood, but crystalloid may be used also). A pulmonary artery wedge catheter (Swan \200\223Ganz) sh ould be used to monitor the wedge pressure and guide \202 uid replacement. If there are signs of aortic regurgitation or tamponade, arrange for an urgent ECHO and discuss with the surgeons. Emerging indications and principles for interventional therapy There are increasing reports and short case series demonstrating favorable outcome (prognostic as well as symptomatic) data on using endovascular stent-grafts in management of primarily type B and also, to a le sser extent, type A aortic dissections. On the basis of the current evidence, endovascular stent-grafts should be considered to sea l the entry to false lumen and to enlarge compressed true lumen in the following situations : \200 unstable type B dissection \200 malperfusion syndrome (proximal aortic stent-gra ft and/or distal fenestration/stenting of branch arteries) routine management of type B dissection (under evaluation). Cardiac tamponade: If the patie nt is relatively stable, pericardiocentesis may precipitate haemodynamic collapse and shoul d be avoided. The patient should be transferred to the operating theater for direct repair as urgently as possible. In the context of tamponade and EMD or marked hypotension, pericar diocentesis is warranted. Long-term treatment must involve strict BP control. 772 CHAPTER 17 Cardiovascular emergencies Prognosis \200 The mortality for untreated aortic dissection is roughly 20 \200\22330 % a t 24 hours and 65 \200\22375 % at 2 weeks. For dissections con \201 ned to the descending aorta, short-term survival is better (up to 80 % ) but 730 \200\22350 % will have progression of dissection despite aggressive medical therapy, and require surgery. Operative mortality is of the order of 10 \200\22325 % and depends on the condition of the patient preoperatively. Postoperative 5-year actuarial survival of up to 7 5 % may be expected. Medical therapy of aortic dissection B-blockade (aim for heart rate (HR)<60 \200\22370/min) Labetalol 20 \200\22380 mg slow IV injection over 10 min then 20 \200\223200 mg/h IV, increasing ever y 15 min 100 \200\223400 mg PO q12h Atenolol 5 \200\22310 mg slow IV injection then 50 mg PO after 15 min and at 12 h, then 100 mg PO da ily Propranolol 0.5 mg IV (test dose), then 1 mg every 2 \200\2235 min up to max 10 mg; repeat every 2 \200 \2233 h 10 \200\22340 mg PO 3 \200\2234 times daily When HR 60 \200\22370 /min, (or if B -blocker contraindicated), add Nitroprusside 0.25 \200\22310 mcg/kg/min IV infusion Hydralazine 5 \200\22310 mg IV over 20 minutes 50 \200\223300 mcg/min IV infusion 25 \200\22350 mg PO q 8h GTN 1 \200\22310 mg/h IV infusion Amlodipine 5 \200\22310 mg PO od This page intentionally left blank 774 CHAPTER 17 Cardiovascular emergencies Acute pericarditis: assessment Presentation \200 Typically presents as central chest pain \200\224 often pleuritic \200\224 relieved by sitting forward and can be associated with breathlessness. Other symptoms (e.g. fever, cough, arthralgia, rash, faintness/dizziness secondary to pain/iHR) may re \202 ect the underlying disease. A pericardial friction rub is pathognomonic. This may be positional and transient and may b e confused with the murmur of triscuspid regurgitation (TR) or MR. Venous pressure rises if an effusion develops. Look for signs of cardiac tamponade (see b Cardiac tamponade: presentation, p. 778). Investigations May be normal in up to 10 % . \200 \200\230Saddle-shaped \200\231 ST-segment elevation ( concave upwards), ECG with variable T inversion (usually late stages) and PR-segment depression (opposite to P-wa ve polarity). Minimal lead involvement to be considered typical includes I, II, aVL, aVF an d V 3 \200\223V 6 . ST-segement is always depressed in aVR, frequently depressed or isoelectric in V 1 , and sometimes depressed in V 2 . \200 May be dif \201 cult to di stinguish from acute MI. Features suggesting pericarditis are: \200 concave ST elevation (vs. convex) \200 all leads invo lved (vs. a territory e.g. inferior) \200 failure of usual ST evolution and no Q waves \200 no AV block, BBB, or QT prolongation. Early repolarization (a normal variant) may be mistaken for pericarditis. In the former, ST elevation occurs in precordial and, rarely, in V 6 or the limb leads, and is unlikely to s how ST depression in V 1 or PR segment depression. Usually not helpful in diagnosing pericarditis post-MI. \200 The voltage drops as an effu sion develops, and in tamponade there is electrical alternans, best seen in QRS complexes. May demonstrate a pericardial collection. \200 Useful to monitor LV function in case of d eterioration due ECHO to associated myopericarditis. We recommend every patient has an ECHO prior to discharge to assess LV function. Other investigations depend on the suspected etiology. ACUTE PERICARDITIS: ASSESSMENT 775 All patients should have: \200 FBC and biochemical pro \201 le \200 ESR and CRP (level s rise proportionate to intensity of disease) \200 serial cardiac enzymes (CK, CK-MB, tro ponin) \200\224 elevations indicate subpericardial myocarditis CXR (heart size, pulmonary oedema, infection). And, where appropriate: \200 viral titres (acute + 2 weeks later) \200\224 and obtain virology opinion \200 blood cultures \200 autoantibody screen (rheumatoid factor (RF), ANA, anti-DNA, complement levels) thyroid function tests (TFTs) \200 fungal precipitins (if immunosuppressed), iMantoux tes t \200 sputum culture and cytology \200 diagnostic pericardial tap (culture, cytology). Causes of acute pericarditis \200 Idiopathic \200 Infection (viral, bacterial, tubercul osis (TB), and fungal) \200 Acute MI \200 Dressler \200\231s syndrome, post-cardiotomy syndrome \200 Malignancy (e.g. breast, bronchus, lymphoma) \200 Uraemia \200 Autoimmu ne disease (e.g. SLE, rheumatoid arthritis (RA), Wegner \200\231s, scleroderma, polyarteritis nodosa (PAN)) Granulomatous diseases (e.g. sarcoid) \200 Hypothyroidism \200 Drugs (hydralazine, proc ainamide, isoniazid) \200 Trauma (chest trauma, iatrogenic) \200 Radiotherapy 776 CHAPTER 17 Cardiovascular emergencies Acute pericarditis: management General measures \200 Admit? This depends on the clinical picture. We recommend admission of most patients for observation for complications, especia lly effusions, tamponade, and myocarditis. Patients should be discharged when pain free. \200 Bed rest \200 Analgesia: NSAIDS are the mainstay. Ibuprofen is well tolerated and i ncreases coronary \202 ow (200 \200\223800 mg qds). Aspirin is an alternative (600 mg qds PO). Indometacin should be avoided in adults as it reduces coronary \202 ow and has mark ed side-effects. Use a proton pump inhibitor (PPI) (lansoprazole 30 mg od) to minimize gast rointestinal (GI) side-effects. Opoid analgesia may be required. Colchicine used as monothe rapy or in addition to NSAIDs may help settle pain acutely and prevent recurrence. Steroids: These may be used if the pain does not settle within 48 hours (e.g. prednisolone 40 \200\22360 mg PO od for up to 2 weeks, tapering down when pain settles). Use in conjunct ion with NSAID and taper steroids \201 rst before stopping NSAID. It is also of value if pericarditis is s to autoimmune disorders. Colchicine: Anecdotal evidence suggests that either used as monotherpay or in conjunction with NSAIDs it may help to settle pain acutely and prevent re lapses (1 mg/day divided doses). Stop if patient develops diarrhea or nausea (1 mg stat, 50 0 mcg q6h for 48h). \200 Pericardiocentesis: This should be considered for signi \201 ca nt effusion or if there are signs of tamponade (see b Cardiac tamponade: presentation, p. 7 78). Antibiotics: These should be given only if bacterial infection is suspected. \200 Oral an ticoagulants should be discontinued (risk of haemo-pericardium). Patient should be given IV UFH, which is easier to reverse (IV protamine) if complications arise. This page intentionally left blank 778 CHAPTER 17 Cardiovascular emergencies Cardiac tamponade: presentation Cardiac tamponade occurs when a pericardial effusion causes haemody- namically signi \201 cant cardiac compression. The presentation depends on the s peed with which \202 uid accumulates within the pericardium. Acute tamponade may occur wi th 100 \200\223200 mL in a relatively restricted pericar- dial sac. Chronic pericardial col lections may contain up to 1000 mL of \202 uid without clinical tamponade. Causes Acute tamponade \200 Cardiac trauma \200 Iatrogenic: \200\230Subacute \200\231 tamponade \200 Malignant disease \200 Idiopathic pericarditi s \200 Uraemia \200 Infections \200 Bacterial: \200 TB \200 Radiation \200 Hypo thyroidism \200 Post pericardotomy \200 SLE post-cardiac surgery \200 post-cardiac catheterization \200 post-pacing/EP study Aortic dissection \200 Spontaneous bleed: \200 anticoagulation \200 uraemia \200 th rombocytopenia \200 Cardiac rupture post-MI EP = electrophysiology. Presentation \200 Patients commonly present either with cardiac a rrest (commonly electrical mechanical dissociation) or hypotension, confusion, stupor, and shock. Patients who develop cardiac tamponade slowly are usually acutely unwell, but not in extremis. Their main symptoms include: \200 breathlessness, leading to air hunger at rest \200 there may be a preceding history of chest discomfort \200 symp toms resulting from compression of adjacent structures by a large effusion (i.e. dysphagia, cough, hoarseness, or hiccough) there may be symptoms due to the underlying cause \200 insidious development may present with complications of tamponade, including renal failure, liver and/or mesenteric ischaemia , and abdominal plethora. Important physical signs \200 Most physical \201 ndings are non-speci \201 c. They inc lude: tachycardia (except in hypothyroidism and uraemia) \200 hypotension ( shock) with post ural hypotension \200 raised JVP (often > 10 cm) with a prominent systolic x descent and absent diastolic y descent. If the JVP is visible and either remains static or rises with i nspiration, it indicates concomitant pericardial constriction (Kussmaul \200\231s sign). CARDIAC TAMPONADE: PRESENTATION 779 Auscultation may reveal diminished heart sounds. Pericardial rub may be present and suggests a small pericardial collection. Look for pulsus paradoxus (a decrease in the palpable pulse and systolic BP of > 10 mmHg on inspiration). This may be so marked that the pulse and Korotkoff sounds may be completely lost during inspiration. This can be measured using a BP cuff 1 or arterial catheter if in situ already. Other conditions that can cause a pulsus paradoxus include: acute hypotension , obstructive airways disease, and pulmonary embolus. Other physical signs include cool extremities (ears, nose) tachypnoea, hepatomegaly, and si gns of the underlying cause for the pericardial effusion. Causes of hypotension with a raised JVP \200 Cardiac tamponade \200 Constrictive perica rditis \200 Restrictive pericarditis \200 Severe biventricular failure \200 Right ven tricular infarction \200 Pulmonary embolism \200 Tension pneumothorax \200 Acute seve re asthma \200 Malignant SVC obstruction and sepsis (e.g. lymphoma). 1 Teaching point: to establish the presence of pulsus paradoxus, non-invasively in \202 at e a BP cuff to 15 mmHg above highest systolic pressure. De \202 ate the cuff gradually unt il the \201 rst beats are heard and hold the pressure at that level, concentrating on dis appearance and reappearance of sounds with respiration (bump \200\223bump, silence \200\223 silence, bump \200\223bump, where noise re \202 ects expiration). Continue to de \202 ate slowly, paying attention to the same pattern until all beats are audible. The difference b etween the initial and \201 nal pressure should be greater than 10 mmHg. 780 CHAPTER 17 Cardiovascular emergencies Cardiac tamponade: management Tamponade should be suspected in patients with hypotension, e levated venous pressure, falling BP, iHR, and iRR (respiratory rate; with clear chest), and pulsus paradoxus, especially if predisposing factors are present. Investigations \200 Chest X-ray: The heart size may be normal (e.g. in acute haemopericardium following cardiac trauma). With slower accumulation of pericardial \202 uid ( > 250 mL), the cardiac silhouette will enlarge with a globular appearance. The size o f the effusion is unrelated to its haemodynamic signi \201 cance. Look for signs of pulmon ary oedema. ECG: Usually shows a sinus tachycardia, with low-voltage complexes and variable ST-segment changes. With large effusions, \200\230electrical alternans \200\231 may be present with b eat-to-beat variation in the QRS morphology resulting from the movement of the heart within the pericardial effusion. Echocardiography con \201 rms the presence of a pericardial effusion. The diagnosis of tam ponade is a clinical one. ECHO signs highly suggestive of tamponade include: (1) chamber co llapse during diastole (RA, RV, RV out \202 ow tract); (2) marked variation in transvalvul ar \202 ow; (3) dilated IVC with little or no diameter change on respiration. If available, examine the central venous pressure trace for the characteristic exaggerated x descent and absent y descent. Management Following con \201 rmation of the diagnosis: \200 while preparing for drainag e of the pericardial \202 uid, the patient \200\231s circulation may temporarily be supported by loading with IV colloid (500 \200\2231000 mL st at) and starting inotropes (i.e. adrenaline) \200 in patients with an adequate blood pres sure, cautious systemic vasodilatation with hydralazine or nitroprusside in conjunction with volume loading, may in crease forward cardiac output. This is not to be recommended routinely, as it may cause acu te deterioration The effusion should be urgently drained (see b Pericardial aspiration, p. 814 \200\2236 for pericardiocentesis) guided by ECHO or \202 uoroscopy. In the event of circulatory collap se, drainage must happen immediately without imaging. surgical drainage is indicated if the effusion is secondary to trauma. \200 avoid intubat ion and positive pressure ventilation as this reduces cardiac output. in patients with cardiac arrest, chest compression has little or no value, as there is no room for additional \201 lling. \200 uraemic patients will also need dia lysis. \200 the cause of the effusion should be established (see b Acute pericarditis: assessment, p. 774). Pericardial \202 uid should be sent for cytology, micr obiology including TB, and, if appropriate Hb, glucose, and amylase. Further management is of the underlying cause. CARDIAC TAMPONADE: MANAGEMENT 781 Special cases \200 Recurrent pericardial effusion: In some cases, pericardial effusion recurs. This requires either a change in the treatment of the underlying cause or a formal surgical drainage procedure such as a surgical pericardial window or pericardiectomy. Low-pressure tamponade: Seen in the setting of dehydration. The JVP is not raised, right at rial pressure is normal, and tamponade occurs even with small volumes of pericardial \202 uid. \200 The patient may respond well to IV \202 uids. \200 If there is a signi \201 cant pericardial collection, this should be drained. This page intentionally left blank 783 Chapter 18 Practical procedures Arterial blood sampling 784 Arterial line insertion: introduction 786 Arterial line inserti on: over-the-wire technique 786 Arterial line insertion: over-the-needle technique 788 Cent ral line insertion 790 Internal jugular vein cannulation 792 Subclavian vein cannulation 79 4 Ultrasound-guided central venous catheterization (1) 796 Ultrasound-guided central venous catheterization (2) 798 Pulmonary artery catheterization (1) 800 Pulmonary artery catheter ization (2) 802 Pulmonary artery catheterization (3) 804 Indications for temporary pacing 8 06 Temporary ventricular pacing 808 Temporary atrial pacing 810 Atrioventricular sequential pacing 811 Temporary pacing: complications 812 Pericardial aspiration (1) 814 Pericardial aspiration (2) 816 DC cardioversion 818 DC cardioversion: special situations 821 Intra-aort ic balloon counterpulsation (1) 822 Intra-aortic balloon counterpulsation (2) 826 Needlesti ck injuries 828 784 CHAPTER 18 Practical procedures Arterial blood sampling An arterial blood sample is used to measure the arterial oxygen ten sion (PaO 2 ), carbon dioxide tension (PaCO 2 ), pH and bicarbonate/base excess levels, and hemoglobin (Hb) saturation (SaO 2 ). Familiarize yourself with the location and the use of the blood gas machine. Arterial blood is obtained either by percutaneous needle puncture or from an indwelling arterial line. Radial artery The radial artery is more accessible and more comfortable for the patient; it is best palpated between the bony head of the distal radius and the tendon of the \202 e xor carpi radialis with the wrist dorsi \202 exed. The Allen test is used to identify impa ired collateral circulation in the hand (a con- traindication to radial artery puncture): t he patient s hand is held high, with the \201 st clenched and both the radial and ulnar a rteries compressed. The hand is lowered, the \201 st is opened, and the pressure from the ulnar artery is released. Color should return to the hand within 5 seconds. Brachial artery The brachial artery is best palpated medial to the biceps tendon in the ant ecubital fossa, with the arm extended and the palm facing up. The needle is inserted just a bove the elbow crease. Femoral artery The femoral artery is best palpated just below the midpoint of the inguinal ligament, with the leg extended. The needle is inserted below the inguinal ligament at a 90 degree angle. The chosen puncture site should be cleaned. Local anesthetic should be in \201 ltrated (no t into the artery). Use one hand to palpate the artery and the other hand to advance the he parin-coated syringe and needle (22 \200\223 25 gauge) at a 60 \200\22390 degree angle to t he skin, with gentle aspiration. A \202 ush of bright red blood indicates successful punc ture. Remove about 2 \200\2233 mL of blood, withdraw the needle, and ask an assistant to ap ply pressure to the puncture site for 5 \200\22315 minutes. Air bubbles should be removed. The sample is placed on ice and analyzed within 15 minutes (to reduce oxygen consumption by white blood cells (WBCs)). Complications These include persistent bleeding, bruising, injury to the blood vessel, and local thrombosis. This page intentionally left blank 786 CHAPTER 18 Practical procedures Arterial line insertion: introduction Indications \200 Continuous monitoring of arterial blood pressure in critically ill patients with haemodynamic instability. Repeated arterial blood sampling. Contraindications \200 Coagulopathy \200 Raynaud \200\231s phenomenon \200 Thromboang iitis obliterans \200 Advanced atherosclerosis \200 End arteries such as the brachial a rtery should be avoided. Initial measures \200 Locate a palpable artery (e.g. radial or femoral). \200 Assess ul nar blood \202 ow using the Allen test, before inserting a radial line (see b Arterial blood sampling, p. 784). Position the hand in moderate dorsi \202 exion with the palm facing up (to bring the artery closer to the skin). The site should be cleaned with a sterile preparation solution and draped appropriately. Use sterile gloves. \200 Use local anesthetic (1 % lidocaine) in a conscious patient. Arterial line insertion: over-the-wire technique (see Fig. 18.1 ) \200 Palpate the artery with the non-dominant hand (1 \200\2232 cm from the wrist between the bony head of the dis tal radius and the \202 exor carpi radialis tendon). The catheter and needle are advanced towards the artery at a 30 \200\22345 angle (Fig. 18.1 (a)) until blood return is seen (Fig. 18.1 (b)). The catheter and needle are then advanced through the vessel a few millimeters further (Fig. 18.1 (c)). \200 The needle is removed (Fig. 18.1 (d)). \200 T he catheter is slowly withdrawn until pulsatile blood \202 ow is seen (Fig. 18.1 (e)). When pulsatile blood \202 ow is seen, the wire is advanced into the vessel (Fig. 18.1 (f )). The catheter is advanced further into the vessel over the wire (Fig. 18.1 (g)). While placing pressure over the artery, the wire is removed (Fig. 18.1 (h)) and the catheter is connected to a transduction system. Secure the catheter in place using suture or tape. \200 Check perfusion to the hand after insertion of the arterial line and at frequent intervals. The line should be removed if there are any signs of vascular compromise, or as early as possible after it is no longer needed. ARTERIAL LINE INSERTION: OVER-THE-WIRE TECHNIQUE 787 Needle Catheter 30 \200\223 45 Artery (a) Blood (b) (c) Needle removed (d) Pulsatile blood flow seen (e) (f) (g) Apply pressure (h) Fig. 18.1 Arterial line insertion: over-the-wire technique. Reproduced with permission from Ramrakha P, Moore K, and Sam M (2010). Oxford Handbook of Acute Medicine . 3rd ed. Oxford: Oxford University Press. 788 CHAPTER 18 Practical procedures Arterial line insertion: over-the-needle technique (see Fig. 18.2 ) \200 Locate and palpa te the artery with the non-dominant hand (1 \200\2232 cm from the wrist between the bony he ad of the distal radius and the \202 exor carpi radialis tendon). The catheter and needle are advanced towards the artery at a 30 \200\22345 angle (Fig. 18.2 (a)) until blood return is seen (Fig. 18.2 (b)). The catheter and needle are then advanced slightly further and the catheter/needle angle is lowered to 10 \200\22315 (Fig. 18.2 (c)). The catheter is advanced over the needle into the vessel (Fig. 18.2 (d)). \200 Proximal p ressure is applied to the artery, the needle is removed (Fig. 18.2 (e)), and the catheter is connected to the transduction system. Secure the catheter in place using suture or tape. \200 Check perfusion to the hand after insertion of the arterial line and at frequent intervals. Complications \200 Local and systemic infection. \200 Bleeding, haematoma, bruising. \200 Vascular complications: blood vessel injury, pseudoaneurysm, thromboembolism, and vasospasm. Arterial spasm may occur after multiple unsuccessful attempts at arterial catheterization. If this occurs, use an alternative site. There may be dif \201 culty in passing a wire or catheter despite the return of pulsatile blood. Adjustment of the angle, withdrawal of the needle, or a slight advance, may be helpf ul. ARTERIAL LINE INSERTION: OVER-THE-NEEDLE TECHNIQUE 789 Needle Catheter 30 \200\22345 Artery (a) Blood (b) 10 \200\22315 (c) (d) Apply pressure (e) Fig. 18.2 Arterial line insertion: over-the-needle technique. Reproduced with per- mission from Ramrakha P, Moore K, and Sam M (2010). Oxford Handbook of Acute Medicine . 3rd edn. Ox ford: Oxford University Press. 790 CHAPTER 18 Practical procedures Central line insertion You will need the following \200 Sterile dressing pack and gloves. \200 10 mL and 5 mL syringe with green (21G) and orange (25G) needles \200 Local anest hetic (e.g. 2 % lidocaine). \200 Central line (e.g. 16G long Abbocath or Seldinger cat heter) \200 Saline \202 ush. \200 Silk suture and needle. \200 No. 11 scalpel blade . \200 Sterile occlusive dressing (e.g. Tegaderm ). Risks \200 Arterial puncture (remove and apply local pressure). \200 Pneumothorax (inse rt chest drain or aspirate if required). \200 Haemothorax. \200 Chylothorax (mainly lef t subclavian lines). \200 Infection (local, septicaemia, bacterial endocarditis). \200 Brachial plexus or cervical root damage (over-enthusiastic in \201 ltration with local anesthetic). Arrhythmias. General procedure \200 The basic technique is the same whatever vein is cannulated. \200 Lie the patient supine ( head-down tilt). \200 Turn the patient \200\231s head away from the side you wish to cannulate. \200 Clean the skin with iodine or chlorhexidine: fr om the angle of the jaw to the clavicle for internal jugular vein (IJV) cannulation, and fr om the midline to the axilla for the subclavian approach. Use the drapes to isolate the sterile \201 eld. \200 Flush the lumen of the central lin e with saline. \200 Identify your landmarks (see b Central line insertion, p. 790 and Internal jugular vein cannulation, p. 792). In \201 ltrate the skin and subcutaneous tissue with local anesthetic. \200 Have the int roducer needle and Seldinger guide wire within easy reach so that you can reach them with o ne hand without having to release your other hand. Your \201 ngers may be distorting the anatomy slightly, making access to the vein easier, and if released it may prove dif \201 cult to relocate the vein. With the introducer needle in the vein, check that you can aspirate blood freely. Use the h and that was on the pulse to immobilize the needle relative to the skin and mandible or cla vicle. Remove the syringe and pass the guide wire into the vein; it should pass freely. If there i s resistance, remove the wire, check that the needle is still within the lumen, and try aga in. Remove the needle, leaving the wire within the vein and use a sterile swab to maintain gent le pressure over the site of venepuncture to prevent excessive bleeding. CENTRAL LINE INSERTION 791 With a No. 11 blade, make a nick in the skin where the wire enters, to facilitate dilatatio n of the subcutaneous tissues. Pass the dilator over the wire and remove, leaving the wire in situ . Pass the central line over the wire into the vein. Remove the guide wire, \202 ush the lumen with fresh saline, and close off to air. Suture the line in place and cover the skin penetration site with a sterile occlusive dressing. Measuring the central venous pressure (CVP): tips and pitfalls \200 When asked to see a p atient with an abnormal CVP reading at night on the wards, it is a good habit to always re- check the zero and the reading yourself. Always do measurements with the mid-axillary point as the zero reference. Sitting the patient up will drop the central \201 lling pressure (pooling in t he veins). Fill the manometer line, being careful not to soak the cotton wall stopping. If this gets wet, it limits the free-fall of saline or dextrose in the manometer line. Look at the rate and character of the venous pressure. It should fall to its value quickly and swing with respiration. If it fails to fall quickly, consider whether the line is open (i.e. saline running in), blocked with blood clot, positional (up against the vessel wall \200\224 ask the patient to take some deep breaths), arterial blood (blood tracks back up the line). Rai se the whole dripstand (if you are strong), and make sure that the level falls. If it falls when the whole stand is elevated, it may be that the CVP is very high. It is easier, and safer, to cannulate a central vein with the patient supine or head down. There is an increased risk of air embolus if the patient is semi-recumbent. 792 CHAPTER 18 Practical procedures Internal jugular vein cannulation The IJV runs just posterolateral to the carotid artery wi thin the carotid sheath and lies medial to the sternocleidomastoid muscle (SCM) in the uppe r part of the neck, between the two heads of the SCM in its medial portion, and enters the subclavian vein near the medial border of the anterior scalene muscle (see Fig. 18.3 ). The re are three basic approaches to IJV cannulation: medial to SCM, between the two heads of t he SCM, or lateral to the SCM. The approach used varies and depends on the experi- ence of the operator and the institution. \200 Locate the carotid artery between the sternal and clavicular heads of the SCM at the level of the thyroid cartilage; the IJV lies just lateral and parallel to it . Keeping the \201 ngers of one hand on the carotid pulsation, in \201 ltrate the skin wit h local anesthetic thoroughly, aiming just lateral to this and ensuring that you are not in a vein. Ideally, \201 rst locate the vein with a blue or green needle. Advance the needle at 45 * to the skin, with gentle negative suction on the syringe, aiming for the ipsilateral nippl e, lateral to the pulse. If you fail to \201 nd the vein, withdraw the needle slowly, maintaining negative suction on the syringe (you may have inadvertently trans \201 xed the vein). Aim slightly more medially and try again. Once you have identi \201 ed the position of the vein, change to the syringe with the intr oducer needle, cannulate the vein, and pass the guide wire into the vein (see b Pulmonary a rtery catheterization, pp. 800 \200\2235). Tips and pitfalls \200 Venous blood is dark, and arterial blood is pulsatile and bright r ed! \200 Once you locate the vein, change to the syringe with the introducer needle, taking care not to release your \201 ngers from the pulse; they may be distorting the anatomy slightly, making access to the vein easier, and if released it may prove dif \201 cult to relocate the vein. The guide wire should pass freely down the needle and into the vein. With the left IJV appr oach, there are several acute bends that need to be negotiated. If the guide wire keeps pas sing down the wrong route, ask your assistant to hold the patient \200\231s arms out at 90 * to the bed, or even above the patient \200\231s head, to coax the guide wire down the cor rect path. For patients who are intubated or require respiratory support, it may be dif \201 cult to access the head of the bed. The anterior approach may be easier (see Fig. 18.3 ) and may be done from the side of the bed (the left side of the bed for right-handed operators, using the left hand to locate the pulse and the right to cannulate the vein). The IJV may also be readily cannulated with a long Abbocath . No guide wire is necessary, but, as a result, misplacement is more common than with the Sel dinger technique. When using an Abbocath , on cannulating the vein, remember to advance the sheath and needle a few mm to allow the tip of the plastic sheath (71 mm behind the tip of the beveled needle) to enter the vein. Holding the needle stationary, advance t he sheath over it into the vein. Arrange for a chest X-ray (CXR) to con \201 rm the position of the line. INTERNAL JUGULAR VEIN CANNULATION 793 Sternal head Sternal head Clavicular head Sternocleidomastoid muscle External jugular vein (a) Surface anatomy of external and internal jugular veins (b) Anterior approach: the chin is in the midline and the skin puncture is over the sternal head of the SCM muscle (c) Central approach: the chin is turned away and the skin puncture is between the two head s of the SCM muscle Fig. 18.3 Internal jugular vein cannulation. 794 CHAPTER 18 Practical procedures Subclavian vein cannulation The axillary vein becomes the subclavian vein (SCV) at the late ral border of the 1st rib and extends for 3 \200\2234 cm just deep to the clavicle. It is j oined by the ipsilateral IJV to become the brachiocephalic vein behind the ster- noclavicul ar joint (see Fig. 18.4 ). The subclavian artery and brachial plexus lie posteriorly, separ ated from the vein by the scalenus anterior muscle. The phrenic nerve and the internal mamm ary artery lie behind the medial portion of the SCV and, on the left, lies the thoracic duc t. \200 Select the point 1 cm below the junction of the medial third and middle third of the clavicle. If possible, place a bag of saline between the scapulae to extend th e spine. Clean the skin with iodine or chlorhexidine. \200 In \201 ltrate the skin and subcutaneo us tissue and periosteum of the inferior border of the clavicle with local anesthetic up to the hilt of the green (21G) nee dle, ensuring that it is not in a vein. Insert the introducer needle with a 10 mL syringe, guiding gently under the clavicle. It is safest to initially hit the clavicle, and \200\230walk \200\231 the needle under it until the inferior border is just cleared. In this way you keep the needle as super \201 cial t o the dome of the pleura as possible. Once it has just skimmed underneath the clavicle, adv ance it slowly towards the contralateral sternoclavicular joint, aspirating as you advance. Using this technique, the risk of pneumothorax is small, and success is high. Once the venous blood is obtained, rotate the bevel of the needle towards the heart. This encourages the guide wire to pass down the brachiocephalic vein rat her than up the IJV. The wire should pass easily into the vein. If there is dif \201 culty, try advancing durin g the inspiratory and expiratory phases of the respiratory cycle. Once the guide wire is in place, remove the introducer needle, and pass the dilator over th e wire. When removing the dilator, note the direction that it faces; it should be slightly curved downwards. If it is slightly curved upwards, then it is likely that the wire has pas sed up into the IJV. The wire may be manipulated into the brachiocephalic vein under \202 uoroscopic control but, if this is not available, it is safer to remove the wire and start again. After removing the dilator, pass the central venous catheter over the guide wire, remove the guide wire, and secure as above. A CXR is mandatory after subclavian line insertion, to exclude a pneumothorax and to con \201 rm satisfactory placement of the line, especially if \202 uoroscopy was not employed . SUBCLAVIAN VEIN CANNULATION 795 Scalenus anterior muscle Subclavian artery Clavicle Phrenic nerve Subclavian vein 1st rib 2nd rib 3rd rib Fig. 18.4 The subclavian vein and surrounding structures. 796 CHAPTER 18 Practical procedures Ultrasound-guided central venous catheterization (1) Traditional central venous catheteriza tion methods rely on anatomical landmarks to predict vein position. However, the relationsh ip between such landmarks and vein position varies signi \201 cantly in \200\230normal \200\231 individuals. Failure and complication rates using landmark methods are signi \201 cant, and therefore serious complications may occur. Recent advances in portable ultrasoun d equipment have now made it possible to insert central venous catheters under two-dimensio nal (2D) ultrasound guidance. Advantages of this technique include: identi \201 cation of the actual and relative vein position \200 identi \201 cation of anatomical variations \200 con \201 rmation of target vein patency. Guidelines from the National Institute for Clinical Excellence (September 2002) state: \200\230Two-dimensional imaging ultrasound guidance is recommended as the preferred method for insertion of centra l venous catheters into the internal-jugular vein (IJV) in adults and children in elective situations \200\231. However, training and equipment availability render such recommendatio ns effectively useless in the UK at present. Equipment/personnel needed \200 Standard Seldinger-type kit or whatever is locally availa ble. \200 An assistant is essential. \200 Ultrasound equipment: screen: displays 2D ultrasound image of anatomical structures. \200 sheaths: dedicated, s terile sheaths of PVC or latex, long enough to cover the probe and connecting cable (a rubb er band secures the sheath to the probe). probe: transducer which emits and receives ultrasound information to be processed for displ ay; marked with an arrow or notch for orientation. power: battery or mains. \200 sterile gel: transmits ultrasound and provides good interfa ce between patient and probe. Preparation Perform a preliminary non-sterile scan to access each IJV for patency and size. Patient Sterile precautions should be taken with patient \200\231s head turned slightly awa y from the cannulation site. Head-down tilt (if tolerated) or leg ele- vation should be use d to increase the \201 lling and size of the IJV. Ensure adequate drapes to maintain a st erile \201 eld. Excessive head rotation or extension may decrease the diameter of the vein. ULTRASOUND-GUIDED CENTRAL VENOUS CATHETERIZATION (1) 797 Ultrasound equipment \200 Ensure that the display can be seen. \200 The sheath is opene d (operator) and gel squirted in (assistant). A generous amount of gel ensures good contact and air-free coupling between the probe tip a nd sheath. Too little may compromise image quality. The probe and connecting cable are lowered into the sheath (assistant), which is then unrol led along them (operator). A rubber band secures the sheath to the probe. \200 The sheath over the probe tip is smoo thed out (wrinkles will degrade image quality). Apply liberal amounts of gel to the sheathed probe tip for good ultrasound transmission and increased patient comfort during movement. 798 CHAPTER 18 Practical procedures Ultrasound-guided central venous catheterization (2) Scanning The most popular scanning ori entation for IJV central catheter placement is the transverse plane: \200 apply the probe tip gently to the neck lateral to the carotid pulse at the cricoid level or in the sternomastoid-clavicular triangle. keep the probe perpendicular at all times, with the tip \202 at against the skin. orientate the probe so that movement to the left ensures that the display looks to the left (and vise versa). Probes are usually marked to help orientation. By convention, the mark should be to the patient \200\231s right (transverse plane) or to t he head (longitudinal scan). The marked side appears on the screen as a bright dot. if the vessels are not immediately visible, keep the probe perpendicular and gently glide medially or laterally until they are found. When moving the probe, watch the screen \200\224 not your hands. After identi \201 cation of the internal jugular vein \200 Position the probe so that th e IJV is shown at the display \200\231s horizontal midpoint.