Show Summary Details
Page of

Practical procedures 

Practical procedures
Chapter:
Practical procedures
Author(s):

Elaine Jolly

, Sian Coggle

, and John D. Firth

DOI:
10.1093/med/9780198746690.003.0648
Page of

PRINTED FROM OXFORD MEDICINE ONLINE (www.oxfordmedicine.com). © Oxford University Press, 2021. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy and Legal Notice).

date: 05 March 2021

Essentials

Key practical clinical procedures are described in this chapter, along with clear anatomical diagrams to enable the reader to fully understand the processes involved. These procedures are clearly organized in the following sections: cannulation and invasive monitoring, cardiac procedures (including pacing), arterial blood gas measurement and interpretation, and airway and respiratory procedures.

Central vein cannulation, arterial cannulation, and invasive monitoring

The insertion of catheters into central veins is increasingly performed with ultrasonographic guidance. However, in some emergencies it may not be possible to use this even in the best-equipped hospital, and in many hospitals such imaging is simply not available. In these circumstances, the central veins can be safely cannulated by landmark techniques, which are described in this section.

Femoral vein cannulation

The optimum position is with the patient supine, but their head and torso can be propped up to an angle of 15 to 30° if this is more comfortable. The key landmark is the femoral pulse, which should be palpated one finger-breadth below the crease of the groin. The femoral vein lies one finger-breadth medial to the femoral artery (the mnemonic NAVY, Nerve–Artery–Vein–Y-fronts, can be useful in remembering the anatomy). The needle should therefore enter the skin one finger-breadth medial to the femoral artery and one finger-breadth below the groin crease (Fig. 30.2.1). It should be advanced in the line of the leg, angled rostrally at about 60° to the skin, and with its bevel pointing upwards. When the vein is punctured, the guide wire should pass directly up the femoral vein and into the inferior vena cava.

Fig. 30.2.1 The approach to the femoral vein.

Fig. 30.2.1 The approach to the femoral vein.

Internal jugular vein cannulation

Low lateral approach

The patient is supine with the head turned away from the side of the puncture. A towel may be placed under both shoulders to extend the neck. After preparation of the skin and drapes, and insertion of local anaesthetic, the bed is tilted to a 25° head-down position. The needle is inserted just lateral to the posterior border of the clavicular head of the sternocleidomastoid muscle, about one finger-breadth above the clavicle, with its bevel pointing caudally. It is then advanced parallel to the line of the clavicle and just behind the sternocleidomastoid muscle. The internal jugular vein, which lies superficially at this point, is cannulated close to its junction with the subclavian vein (Fig. 30.2.2a). As soon as the vein is entered, the needle is angulated caudally to ease cannulation, the guide wire passing directly into the innominate vein. The risk of complications was lower with this technique than for any other method of central venous cannulation used in one series of over 5400 cases.

Fig. 30.2.2 (a) The low lateral approach to the internal jugular vein. (b) The axial approach to the internal jugular vein.

Fig. 30.2.2 (a) The low lateral approach to the internal jugular vein. (b) The axial approach to the internal jugular vein.

Axial approach

The patient is positioned as described for the low lateral approach to the internal jugular vein (Fig. 30.2.2b). The needle is inserted in the centre of the triangle defined by the sternal and clavicular heads of the sternocleidomastoid muscle and the clavicle itself. It should be angulated caudally, at about 60° to the skin, and in a line pointing towards the ipsilateral anterior superior iliac spine.

Subclavian vein cannulation

Infraclavicular approach

The patient is positioned as described for the low lateral approach to the internal jugular vein, excepting that instead of a towel being placed under both shoulders it should be positioned under the spine, allowing the shoulders to retract to reduce the risk of pneumothorax. The needle enters the skin below the midpoint of the lower border of the clavicle and is advanced under the clavicle towards the upper edge of the junction of the clavicle with the manubrium (Fig. 30.2.3a).

Fig. 30.2.3 (a) The infraclavicular approach to the subclavian vein. (b) The supraclavicular approach to the subclavian vein.

Fig. 30.2.3 (a) The infraclavicular approach to the subclavian vein. (b) The supraclavicular approach to the subclavian vein.

Supraclavicular approach

The patient is positioned as described for the infraclavicular approach to the subclavian vein. The needle is inserted into the angle between the superior border of the clavicle and the posterior border of the clavicular head of sternocleidomastoid and advanced caudally, medially, and ventrally (Fig. 30.2.3b).

Pulmonary artery flotation catheter

Central venous cannulation should be performed as described previously and a pulmonary artery (PA) catheter introducer inserted. Ensure that the balloon at the end of the PA catheter inflates completely and uniformly, and then slowly advance the catheter while watching the pressure trace on the monitor. The balloon should be inflated when the catheter is advanced and deflated whenever the catheter is withdrawn. Pressure traces corresponding to the right atrium, the right ventricle, and the PA should be seen (Fig. 30.2.4). As a rough guide, the waveform should change for every 10 cm that the catheter is advanced. Inflation of the balloon when the catheter is in a medium-sized PA allows it to ‘wedge’ and occlude distal flow. To obtain valid readings, the catheter tip should reside in a region of the lung where pulmonary venous pressure exceeds alveolar pressure (Fig. 30.2.5). The pressure recorded at the tip of the catheter (pulmonary capillary wedge pressure) provides an indirect measurement of the left atrial pressure, which reflects left ventricular end-diastolic pressure if the chamber is not diseased. Values for cardiac output and mixed-venous blood chemistries may also be directly measured. A number of variables such as systemic vascular resistance and left ventricular stroke work may be derived from values measured with a PA catheter.

Fig. 30.2.4 Pressure tracings obtained on insertion of a pulmonary artery flotation catheter. CVP, central venous pressure; PA, pulmonary artery; PCWP, pulmonary capillary wedge pressure; RA, right atrium; RV, right ventricle.

Fig. 30.2.4 Pressure tracings obtained on insertion of a pulmonary artery flotation catheter. CVP, central venous pressure; PA, pulmonary artery; PCWP, pulmonary capillary wedge pressure; RA, right atrium; RV, right ventricle.

Fig. 30.2.5 Chest radiograph showing a pulmonary artery flotation catheter in position. A—end of sheath of flotation catheter; B—distal end of flotation catheter; C—proximal injection end of flotation catheter (where cold saline is typically injected for measurement of cardiac index and other physiological parameters).

Fig. 30.2.5 Chest radiograph showing a pulmonary artery flotation catheter in position. A—end of sheath of flotation catheter; B—distal end of flotation catheter; C—proximal injection end of flotation catheter (where cold saline is typically injected for measurement of cardiac index and other physiological parameters).

From Yang W, et al. (2015). The effects of differential injection sites of cold saline on transpulmonary thermodilution parameter values. Patient Prefer Adherence, 9, 551–4.

Arterial puncture/cannulation

Before attempting to puncture or cannulate the radial artery, check the patency of the ulnar artery by applying pressure to the radial artery and asking the patient to clench their fist firmly. On relaxing the fist, the hand should pink up within 10 s (Allen test).

A 25 G needle (orange) is perfectly adequate to obtain an arterial blood gas sample from a radial artery; an 18 G (green) or 23 G (blue) needle is needed for a femoral sample. Use either a preheparinized arterial blood gas syringe or draw up 1 ml of 1000 U/ml heparin into a syringe and then completely expel the heparin.

Lay the index and middle fingers of your nondominant hand along the line of the artery as a guide (Fig. 30.2.6). For radial and brachial samples, hold the syringe at 45 to 60° to the skin and slowly advance in the line of the artery. For femoral samples, hold the syringe at 90° to the skin. A flash of blood into the syringe indicates successful puncture. Some syringes will fill to a predetermined volume, others require aspiration of 1 to 2 ml.

Fig. 30.2.6 Puncture of the radial artery.

Fig. 30.2.6 Puncture of the radial artery.

After successful arterial puncture, press on the site for 3 min (5 min if anticoagulated) to prevent haematoma formation.

Arterial cannulation may be performed either with a cannula over a needle (similar to a venflon) or with a Seldinger technique. After preparation of the skin and insertion of local anaesthetic, the method of arterial puncture should be as described above, with the exception that for all arterial cannulations the needle should be inserted at 45° to the artery. Once arterial puncture has been confirmed, the cannula should be advanced over the needle, or the guide wire passed directly into the artery and the cannula then advanced over the guide wire.

Cardiac procedures

DC cardioversion

Synchronized cardioversion is the treatment of choice for symptomatic tachyarrhythmias. Conscious patients must be anaesthetized or sedated. Suitable monitoring and facilities for dealing with cardiac arrest should be available. Modern defibrillators incorporate a switch that allows the shock to be synchronized with the R wave of the ECG to reduce the risk of inducing ventricular fibrillation. Gel pads should be applied to the chest wall and cardioversion carried out in the same manner as for defibrillation. The energy required depends on the underlying rhythm. Synchronization means that there may be a delay between pressing the defibrillator buttons and the discharge of the shock when the next R wave occurs.

Cardiac pacing (temporary)

Indications for emergency/acute temporary cardiac pacing are shown in Table 30.2.1.

Table 30.2.1 Indications for temporary transvenous cardiac pacing

Acute myocardial infarction

ACC/AHA class I—pacing supported by evidence and/or general agreement

Asystole

Symptomatic bradycardia (includes sinus bradycardia with hypotension  and type I second-degree AV block not responsive to atropine)

Bilateral BBB (alternating BBB or RBBB with alternating LAHB/LPHB)

Bifascicular block (RBBB with LAHB or LPHB, or LBBB) with first-degree  AV block

Mobitz type II second-degree AV block

ACC/AHA class IIa—weight of evidence and/or opinion favours pacing

RBBB with LAHB or LPHB

RBBB with first-degree AV block

LBBB

Incessant VT, for overdrive pacing

Recurrent sinus pauses (>3 s) not responsive to atropine

ACC/AHA class IIb—usefulness of pacing less well established

Bifascicular block of indeterminate age

Isolated RBBB

ACC/AHA class III—pacing not useful and may be harmful

First-degree AV block

Mobitz type I second-degree AV block with normal haemodynamics

Accelerated idioventricular rhythm

BBB or fascicular block known to be present before myocardial  infarction

Bradycardia not associated with myocardial infarction

Asystole

Second- or third-degree AV block with haemodynamic disturbance or  syncope at rest

Ventricular tachyarrhythmia secondary to bradycardia

ACC/AHA, American College of Cardiology/American Heart Association; AV, atrioventricular block; BBB, bundle branch block; LAHB, left anterior hemiblock; LBBB, left bundle branch block; LPHB, left posterior hemiblock; RBBB, right bundle branch block; VT, ventricular tachycardia.

External (transcutaneous) pacing

Percussion pacing

Percussion pacing can be used as a temporizing measure in some patients with profound bradycardia causing clinical cardiac arrest. It is particularly useful for ventricular standstill where P waves are visible on the ECG. A series of gentle blows should be applied to the lower left sternal edge using the closed fist. Using trial and error, a site can sometimes be found which results in stimulation of the ventricular myocardium. If percussion does not produce a cardiac output, orthodox pacing or cardiopulmonary resuscitation should be instituted immediately.

Transcutaneous pacing

Most modern transcutaneous pacing systems are integrated with an ECG monitor/defibrillator. Pacemaker electrodes should be placed in either an anterior–posterior position or in the conventional anterior–lateral configuration. The pacemaker should be set to demand pacing to prevent a stimulus from falling on the T wave following a spontaneous heartbeat, with the rate set at 60 to 90/min for adults. The pacemaker current should be set at the lowest setting and gradually increased to obtain capture of the myocardium and a palpable pulse. The current required to obtain capture is generally in the range of 50 to 100 mA and will produce painful contraction of the patient’s skeletal muscle. Conscious patients will require analgesia and/or sedation. If capture of the myocardium does not occur, alternative electrode placement should be tried, but transcutaneous pacing is only a temporizing measure and arrangements should be made for urgent transvenous pacing.

Transvenous pacing (ventricular)

Temporary transvenous pacing can be achieved after cannulation of any central vein, but is most easily performed via the right internal jugular, right subclavian, or right femoral vein, which can be cannulated as described previously.

The conventional Seldinger technique of guide wire and dilators is used to allow placement of a sheath (preferably haemostatic) of sufficient size to accept passage of the pacing wire in the vein that has been cannulated. The pacing wire is passed down the sheath and advanced towards the heart, the aim being to manoeuvre it under fluoroscopic guidance into a position where its tip is at the apex of the right ventricle, angulated slightly downwards. Key aspects of the technique are shown in Fig. 30.2.7. Common problems and their solutions are described in Tables 30.2.2 and 30.2.3.

Fig. 30.2.7 Transvenous pacing (ventricular). Correct positioning of the electrode is helped if there is a 20 to 30° curve at the tip of the pacing wire. Mould the electrode to this shape using your fingers: it may need to be bent or straightened depending on its packaging. (a) Advance the wire until it lies vertically in the right atrium. It will usually assume a position where its tip points towards the free wall on the right side (b). Rotate the wire between your index finger and thumb until it points towards the patient’s left (c). When it has done so, advance the wire steadily: it should pass through the tricuspid valve and along the floor of the right ventricle to the apex (d). IVC, inferior vena cava; RA, right atrium; RV, right ventricle; RVOT, right ventricular outflow tract; SVC, superior vena cava; TV, tricuspid valve.

Fig. 30.2.7 Transvenous pacing (ventricular). Correct positioning of the electrode is helped if there is a 20 to 30° curve at the tip of the pacing wire. Mould the electrode to this shape using your fingers: it may need to be bent or straightened depending on its packaging. (a) Advance the wire until it lies vertically in the right atrium. It will usually assume a position where its tip points towards the free wall on the right side (b). Rotate the wire between your index finger and thumb until it points towards the patient’s left (c). When it has done so, advance the wire steadily: it should pass through the tricuspid valve and along the floor of the right ventricle to the apex (d). IVC, inferior vena cava; RA, right atrium; RV, right ventricle; RVOT, right ventricular outflow tract; SVC, superior vena cava; TV, tricuspid valve.

Table 30.2.2 Common problems in temporary transvenous ventricular pacing

Problem

Possible solution

Wire will not cross the tricuspid valve

Feed the wire into the right atrium until it ‘catches’ and forms a large loop. It may pass into the IVC (if approaching from above) or SVC (if approaching from below), in which case it will need to be pulled back and then pushed forward until it does catch. When a large loop has been formed, rotate the wire until its tip flips through into the ventricle

Intubation of the coronary sinus

The wire appears to be in the right ventricle, but (sometimes) will not capture the ventricle at an acceptable voltage output. On fluoroscopy, the electrode tip is directed upwards and towards the left shoulder (and on a lateral chest radiograph is directed posteriorly rather than anteriorly). If satisfactory pacing cannot be obtained, then the pacing wire must be withdrawn into the right atrium and further attempts made to advance it across the tricuspid valve

Wire is in the right ventricle, but it is difficult to get it positioned at the apex

Pass the tip of the wire into the right ventricular outflow tract, then gently withdraw it while rotating it between index finger and thumb. When the tip is angulated downwards, advance towards the apex of the ventricle. Note that it can be difficult to get a good position at the apex if the pacing wire is too bent to start off with, hence the injunction to mould the tip with the fingers to obtain an angulation of 20–30º at the beginning of the procedure

IVC, inferior vena cava; SVC, superior vena cava.

Table 30.2.3 Failure to pace

Problem

Causes

Solution

No spikes seen and no output

Battery/generator failure

Replace battery/generator

Loose connections

Check and tighten

Oversensing

Reduce sensitivity or go to fixed-rate pacing

Spikes seen, but no capture

Loose connections

Check and tighten

Exit block (high threshold)

Increase output

Check position of pacing wire (by fluoroscopy or plain radiograph)

Consider repositioning of electrode

Intrapericardial pressure can be directly measured with a manometer (optional); pericardial fluid can be sent for diagnostic tests (optional).

After positioning the pacing wire, set the pacemaker to a rate of 70/min, or 10/min above the patient’s ventricular rate, and deliver a pulse of 3 V (or as directed by the manufacturer). A correctly positioned electrode should ‘capture’, such that each pacing spike is followed by a ventricular complex on the ECG. Establish the voltage threshold by gradually turning down the amplitude of the voltage delivered until capture is lost, which will usually be in the range 0.7 to 1.0 V. To allow a safety margin, it is then appropriate in most circumstances to set the pacemaker to deliver a voltage of at least twice the threshold. Sensing can be checked only if there is spontaneous ventricular activity: this is best done by setting the pacemaker rate to between 10 and 20/min less than the spontaneous ventricular rate and looking on the ECG monitor and the pulse generator for evidence of pacing inhibition. Sensitivity is usually set to its maximum. Common problems and their solutions are described in Tables 30.2.2 and 30.2.3.

When the pacing wire is positioned appropriately and pacing is established, carefully remove the introducer sheath (in most cases), secure the wire with a strong suture (usually 2/0 silk), loop it once or twice on the skin, and then dress with a clear adhesive dressing.

Pericardiocentesis

Cardiac tamponade is the indication for pericardiocentesis as an emergency. Unless the patient is in extremis the procedure should, whenever possible, be performed with echocardiographic guidance by an operator experienced in the technique, as follows:

Two-dimensional echocardiography is used to assess the size, distribution, and haemodynamic effect of the effusion.

The ideal entry site for pericardiocentesis is the point on the skin where the effusion is closest to the transducer and the fluid accumulation is maximal. The distance from the skin to the pericardial space is estimated, with the needle trajectory defined by the angulation of the hand-held transducer. A straight path that best avoids vital structures (also the internal mammary artery, which lies 3–5 cm lateral to the sternal margin) is chosen.

After preparation of the skin and insertion of local anaesthetic, a 16 to 18 G polytef-sheathed (or similar) needle attached to a saline-filled syringe is advanced in the predetermined trajectory, with continued gentle aspiration as it moves forward. On entering the pericardial fluid, the needle is advanced approximately 2 mm further, when the sheath is advanced over the needle and the steel core withdrawn.

The position of the sheath in the pericardial space can be confirmed by injecting 5 ml of agitated saline through it, while observing the pericardial space with two-dimensional echocardiography (optional).

A guide wire is advanced through the polytef sheath, which is removed over the guide wire. A small stab incision of the skin is made at the entry site, following which dilators are used to allow the insertion of a larger sheath (6–8 F) through which a pigtail angiocatheter can be introduced. After the pigtail catheter has been inserted, the introducer sheath is removed, leaving only the smooth-walled pigtail catheter in the pericardial space. (Note that this technique is preferred to that of introducing the pigtail catheter directly over the guide wire because the catheter tip can occasionally pull the guide wire out of the pericardial sac, particularly if this is sclerotic.)

Pericardial fluid is drained completely by syringe suction and the pericardial catheter is secured to the chest wall by suture and an appropriate dressing.

If left on continuous drainage, pericardial catheters become plugged. It is therefore better to perform intermittent aspiration, every 4 to 6 h or as clinically indicated, leaving the catheter flushed with saline in between times. It can be removed when drainage has been reduced to less than 25 to 30 ml/day and follow-up echocardiography shows no significant residual effusion (sooner if the catheter is causing problems).

If the patient is in extremis and/or echocardiography (with appropriate expertise) is not available, then a ‘blind’ subxiphoid approach is most often used:

  • Sit the patient up at an angle of 45°.

  • Insert the needle 3 cm below the xiphisternum at an angle of 30 to 45° to the skin and advance, applying gentle suction all the time (as above), in a line towards the patient’s left shoulder.

  • If the needle touches the heart, it will usually provoke ectopic beats. Some authorities recommend that the aspiration needle is attached to the ‘V’ lead terminal of an ECG cable (using insulated wire with a clip on each end, or simply with sticky tape) to allow continuous monitoring. If the needle touches the heart, then the character of the ECG changes, most particularly with the appearance of gross ST-segment elevation if the needle touches the right or left ventricle.

  • When fluid is obtained, proceed as described above.

Arterial blood gases

Parameters that may be measured or derived by blood gas machines are listed and commented on in Table 30.2.4.

Table 30.2.4 Blood gases—parameters

Normal range

Notes

Po2

>10.6 kPa (80 mmHg), when breathing air

  1. (1) Can only be interpreted if the inspired oxygen concentration is known

  2. (2) Hypoxia defined as Po2 <8 kPa when patient breathing air

  3. (3) If patient is breathing with supplemental oxygen, a ‘hypoxaemia score’ can be calculated as: hypoxaemia score = Po2 (mmHg)/Fio2 If a patient was breathing air and had a Po2 at the lower limit of the normal range, then their hypoxaemia score would equal 10.6 × 7.6/0.21, or c.380. If they had a Po2 of 8 kPa, then their hypoxaemia score would be 8 × 7.6/0.21, or c.290. In assessing a patient breathing supplemental oxygen a value of <300 is usually taken as indicating significant compromise

Pco2

4.7–6.0 kPa (35–45 mmHg)

  1. (1) Po2 <8 kPa with Pco2 <6.5 kPa = type 1 respiratory failure

  2. (2) Po2 <8 kPa with Pco2 >6.5 kPa = type 2 respiratory failure

  3. (3) Low Pco2 indicates hyperventilation, which may be primary or secondary, the latter being indicated by a base excess more negative than –2 (see below)

  4. (4) High Pco2 indicates hypoventilation, which may be primary or secondary, the latter being indicated by a base excess more positive than +2 (see below)

pH

7.37–7.43

  1. (1) pH <7.35 defines acidosis

  2. (2) pH >7.45 defines alkalosis

H+

37–43 nmol/litre

  1. (1) H+ >45 nmol/litre defines acidosis

  2. (2) H+ <35 nmol/litre defines alkalosis

HCO3

19–24 mmol/litre

  1. (1) Measurement of arterial or venous (normal range 22–28 mmol/litre in plasma) bicarbonate concentration is often helpful in analysis of patients with acid–base disturbance

  2. (2) Changes in bicarbonate concentration occur slowly (over many hours or days), hence evidence of compensatory change, e.g. high bicarbonate concentration in the patient with elevated Pco2, indicates that the respiratory abnormality is chronic

Base excess

+2 to –2 mmol/litre

Are measured abnormalities of pH or Pco2 due to metabolic or respiratory processes? Many blood gas machines display a value for the base excess (or deficit), which is a value derived from primary (directly measured) data using an algorithm, the principles of which are as follows:

  1. (1) Predict the pH that would arise in normal blood in the presence of the Pco2 actually measured: if the Pco2 is high, then the predicted pH is low, and vice versa

  2. (2) Calculate the amount of acid or base that would have to be added to the blood to change the predicted pH to the pH measured. This is the base deficit/excess and an estimate of the degree of ‘metabolic’ as opposed to ‘respiratory’ disturbance. A base excess more negative than –2 indicates metabolic acidosis; a value more positive than +2 indicates metabolic alkalosis

Note: 1 kPa = 7.6 mmHg.

Airway and respiratory procedures

Mechanical support of ventilation

Continuous positive airways pressure

Continual positive airway pressure (CPAP) exerts a dilating force on the upper airway (hence its use in obstructive sleep apnoea), and also recruits collapsed alveoli and increases functional residual capacity. This improves lung compliance, reducing the work of breathing, which is a benefit in a range of clinical circumstances.

CPAP can be used for patients with acute or acute on chronic hypoxaemia who are not exhausted or in ventilatory failure (meaning elevated Pco2), for example, acute pulmonary oedema, postoperative atelectasis, and pneumonia. It is not appropriate and is contraindicated for patients who are too obtunded to cooperate, who are unable to protect their airway, who have haemodynamic instability or life-threatening arrhythmias, life-threatening hypoxaemia, or exhaustion.

CPAP is applied via a tight-fitting face or nose mask, the usual range for pressure being 2.5 to 10 cmH2O. Once the mask is applied, patient comfort, respiratory rate, and arterial blood gases should be monitored. Some patients are unable to tolerate the face mask: gastric distension, vomiting, aspiration, eye irritation, conjunctivitis, and necrosis of the facial skin are other complications.

Noninvasive positive pressure ventilation

Masks that are used for CPAP can also be used to provide noninvasive positive pressure ventilation (NIPPV, often more simply referred to as NIV). The difference between the two treatments is that in CPAP a constant pressure is applied to the airway, but no airflow occurs in the absence of respiratory muscle activity. By contrast, in NIV a pulse of positive pressure is applied to assist respiration, the usual arrangement being that this is triggered by a sensor that detects a fall in pressure in the facial mask when the patient initiates a breath. If a positive pressure is also applied in the expiratory phase (EPAP) in addition to the pulse delivered to support inspiration, then then this is known as bilevel pressure support (BIPAP).

Contraindications for and complications of NIV are the same as those for CPAP.

Invasive ventilation

Invasive ventilation may be applied via a tracheal tube or tracheostomy. Ventilation can be adjusted by altering the minute volume (respiratory rate × tidal volume). Oxygenation is adjusted by altering inspired oxygen concentration and positive end-expiratory pressure (PEEP, which acts in a similar manner to CPAP by recruiting collapsed alveoli and reducing the work of breathing). Most ventilators for adults are volume generators that deliver a fixed tidal volume regardless of changes in lung mechanics. If the lungs become stiffer, then inflation pressure will increase to deliver the same tidal volume.

The change from inspiration to expiration is usually time cycled; that from expiration to inspiration is usually either time cycled or triggered by the patient if they are breathing spontaneously. The following values can be used as a guide when initially setting up a ventilator for an adult:

  • Tidal volume should be 10–15 ml/kg.

  • Respiratory rate should be 10–12/min.

  • Ratio of inspiratory to expiratory time (I/E ratio) set at 1:2, but for patients with chronic obstructive pulmonary disease or asthma, a smaller I/E ratio is often used (e.g. 1:3) to prevent gas trapping and hyperinflation.

  • Concentration of inspired oxygen depends on the clinical context: the patient with normal lungs who requires respiratory support because of respiratory muscle weakness does not need a high Fio2 (start with, say, 28%), whereas the patient with severe problems with gas exchange (e.g. bilateral pneumonia or acute respiratory distress syndrome) will require a high Fio2 (start with say 60–80%).

Once ventilation is established, the various parameters should be adjusted (and others added, e.g. CPAP) according to the patient’s clinical condition and the results of repeated measurement of arterial blood gases.

Management of the airway

Endotracheal intubation

Endotracheal intubation remains the gold standard for airway management as it provides a method of oxygenating and ventilating the patient, while securing the airway from vomitus and secretions. However, much harm can be done if endotracheal intubation is attempted by those not competent to perform the procedure, which should only be attempted by clinicians who have been appropriately trained.

Intubation should be preceded by ventilation with high-concentration oxygen and (when required) appropriate medication. The neck should be slightly flexed and the head extended (with an assistant holding the neck in a neutral position if trauma to the cervical spine is suspected). The mouth should be inspected for loose teeth or dentures, which should be removed, as should any secretions or vomitus (by suction). A trained assistant should apply cricoid pressure to prevent passive regurgitation.

The laryngoscope should be introduced over the right side of the tongue, moving the tongue to the left. The tip of the blade should be positioned in the vallecula (between the epiglottis and the base of the tongue) and lifted upwards and away from the operator to expose the vocal cords (Fig. 30.2.8a). The endotracheal tube should be introduced so that the cuff is positioned just beyond the cords (Fig. 30.2.8b).

Fig. 30.2.8 (a) Position of the laryngoscope before insertion of the endotracheal tube. (b) Placement of the endotracheal tube.

Fig. 30.2.8 (a) Position of the laryngoscope before insertion of the endotracheal tube. (b) Placement of the endotracheal tube.

After successful intubation, the patient should be ventilated with high-concentration oxygen, the endotracheal tube secured, and the tube cuff inflated. Positioning of the endotracheal tube should be confirmed by listening over the apices and the bases of the lungs, and over the stomach. If available, an end-tidal CO2 monitor should be attached to the endotracheal tube (in the United Kingdom, this is mandatory in a hospital setting).

Laryngeal mask airway

The laryngeal mask airway (LMA) is used widely in routine anaesthetic practice and is increasingly used for immediate airway management in cardiac arrest (Fig. 30.2.9). Pulmonary aspiration associated with the use of a LMA is uncommon provided high inflation pressures are avoided.

Fig. 30.2.9 A laryngeal mask airway (LMA). A—connector; B—airway tube; C—junction of airway tube with laryngeal mask; D—cuff; E—pilot balloon assembly (if the pilot balloon is inflated, then the cuff of the LMA is inflated).

Fig. 30.2.9 A laryngeal mask airway (LMA). A—connector; B—airway tube; C—junction of airway tube with laryngeal mask; D—cuff; E—pilot balloon assembly (if the pilot balloon is inflated, then the cuff of the LMA is inflated).

From Singh M, Bharti R, Kapoor D (2010). Repair of damaged supraglottic airway devices: a novel method. Scand J Trauma Resusc Emerg Med, 18, 33.

The patient should be supine with the neck slightly flexed and the head extended (with an assistant holding the neck in a neutral position if trauma to the cervical spine is suspected). The LMA should be held like a pen, and introduced into the mouth with the distal aperture facing towards the patient’s feet. The tip should be applied to the palate and advanced until it reaches the posterior pharynx. The LMA is then pressed backwards and downwards until the resistance of the hypopharynx is felt (Fig. 30.2.10), when the cuff of the LMA should be inflated. If insertion is satisfactory, the end of the LMA will rise slightly. Positioning of the LMA should be confirmed by listening over the apices and the bases of the lungs, and over the stomach. If available, an end-tidal CO2 monitor should be attached.

Fig. 30.2.10 Laryngeal mask airway inserted into the hypopharynx. The inflated cuff surrounds and isolates the entrance to the larynx.

Fig. 30.2.10 Laryngeal mask airway inserted into the hypopharynx. The inflated cuff surrounds and isolates the entrance to the larynx.

I-gel®

The i-gel® (Fig. 30.2.11) is easier to insert than a LMA and has an increasing role in immediate airway management in cardiac arrest. The cuff does not require inflation and the stem incorporates a bite block and an oesophageal drain tube. Laryngeal seal pressures of 20 to 24 cmH2O can be achieved.

Fig. 30.2.11 An i-gel® supraglottic airway device.

Fig. 30.2.11 An i-gel® supraglottic airway device.

From Subramanian S, Divya S (2016). Supraglottic devices in laparoscopic surgery – a review of literature. J Anesth Clin Care, 3, 13.

The patient should be supine with the neck slightly flexed and the head extended (with an assistant holding the neck in a neutral position if trauma to the cervical spine is suspected). Hold the i-gel® by the bite block with the cuff outlet facing the patient’s chin. If possible, apply gentle downward pressure to the patient’s chin and glide the cuff downwards and backwards along the hard palate until definitive resistance is felt. The bite block should be resting at the level of the incisors. Positioning of the i-gel® should be confirmed by listening over the apices and the bases of the lungs, and over the stomach. If available, an end-tidal CO2 monitor should be attached.

Cricothyroidotomy

Needle cricothyroidotomy

Insertion of a needle or a cannula (typically a large-bore intravenous cannula) through the cricothyroid membrane is a useful emergency technique that allows short-term provision of oxygen until a definitive airway can be placed. The cannula should be connected to high-flow oxygen with either a Y connector or a side hole cut into the tubing between the cannula and the oxygen supply (Fig. 30.2.12). Intermittent insufflation can be achieved by closing the Y connector or side hole with a thumb for 1 s and then releasing it for 3 s. Inadequate exhalation leads to accumulation of CO2, hence this technique of ventilation can only be used for 30 to 45 min.

Fig. 30.2.12 Oxygenation via a cannula through the cricothyroid membrane.

Fig. 30.2.12 Oxygenation via a cannula through the cricothyroid membrane.

Surgical cricothyroidotomy

The skin over the cricothyroid membrane should be cleaned and local anaesthetic inserted (in patients who are conscious). A horizontal skin incision is made and extended through the cricothyroid membrane (Fig. 30.2.13). A curved haemostat (forceps) is then used to dilate the opening and a small, cuffed endotracheal tube or tracheostomy tube inserted. The position of the tube should be confirmed by auscultation of the lungs and over the stomach, and the tube then secured.

Fig. 30.2.13 Technique of surgical cricothyroidotomy.

Fig. 30.2.13 Technique of surgical cricothyroidotomy.

Percutaneous procedures on the chest

Chest decompression

The rapidly deteriorating patient with clinical signs of a tension pneumothorax requires immediate needle decompression of the chest. The second intercostal space on the side of the tension pneumothorax should be identified, and an over-the-needle cannula or any hollow needle should be inserted in the midclavicular line, directing it just superior to the rib into the intercostal space. Listen for a sudden escape of air when the needle enters the pleural cavity. The cannula should be secured and arrangements made for an intercostal drain to be inserted as soon as the tension pneumothorax has been decompressed.

Chest aspiration

Chest aspiration is recommended as first-line treatment for all primary pneumothoraces that require intervention. The advantages over intercostal tube drainage are that, if successful, needle aspiration means a shorter hospital stay, less pain, and less scarring. Simple aspiration is less likely to succeed in those with secondary pneumothoraces and is only recommended in patients with underlying lung disease who are minimally breathless, less than 50 years of age, and with a small (<2 cm) pneumothorax.

An anterior approach using the second intercostal space in the midclavicular line can be used, or a posterior approach, with the patient in a sitting position with the arms gripping the knees, and using the second, third, or fourth intercostal space medial to the scapula.

The skin should be prepared and local anaesthetic infiltrated down to the pleura. The cannula (either by a Seldinger over a guide wire technique, or using a cannula over-the-needle device) is inserted perpendicular to the skin and just over the superior border of the rib. It is then connected to a three-way tap, the second port of which is connected to a 50 ml syringe, and the third to a length of tubing that runs to open under the surface a container of sterile water (Fig. 30.2.14). Aspiration should be continued until resistance is felt, the patient coughs excessively, or a total of 4 litres of air has been aspirated.

Fig. 30.2.14 Chest aspiration (posterior approach).

Fig. 30.2.14 Chest aspiration (posterior approach).

The success (or otherwise) of aspiration can be determined by repeat chest radiography. The procedure may be repeated if not successful or if the pneumothorax recurs. Success is less likely for older patients and in those with chronic lung disease or recurrent pneumothorax, and also after aspiration of more than 2.5 litres of air.

Chest drain

Always confirm the correct side for chest tube insertion. The usual site is the fourth to sixth intercostal space, just anterior to the midaxillary line. Position the patient supine with the head of the bed slightly elevated and the patient’s arm behind their head. Clean and drape the area for tube insertion. Infiltrate local anaesthetic down to the parietal pleura (10–20 ml of 1% lidocaine (lignocaine)).

The technique for tube insertion depends on its type: those using a Seldinger over-a-wire mechanism should be placed according to the manufacturer’s instructions; for trocar-containing tubes, proceed as described below:

  • Make a 2 to 3 cm transverse incision at the site and blunt dissect through the subcutaneous tissues, just over the superior surface of the rib. Puncture the parietal pleura with the end of the dissection forceps and insert a gloved finger into the incision to ensure that the pleural space has been entered.

  • Remove the trocar from the intercostal drain and slide the drain over your finger into the pleural cavity, when ‘fogging’ of the tube should be seen. For a pneumothorax, the drain is angulated towards the apex of the lung; for a pleural effusion/haemothorax, it is angulated towards the base. Connect the end of the intercostal tube to an underwater-seal apparatus and confirm correct placement by ensuring that the fluid level is swinging with respiration.

  • Insert two 3/0 monofilament sutures at 90° to the line of the skin incision, one on either side of the chest drain, but do not tie them. They will be used to close the skin when the chest drain is removed (and are much better for this purpose than a purse-string suture, which produces an unsightly scar). Suture the tube in place with a separate 1/0 or 2/0 silk suture, tied around it as many times as its length allows. If the skin incision is gaping on either side of the drain, close this with one or more 3/0 sutures. Place a gauze dressing around the site and secure with strong tape, wrapping some of this around the tube to secure it firmly.

  • Obtain a chest radiograph to confirm satisfactory placement and effect of the chest drain.

Note that inserting a chest drain is a risky procedure. Between January 2005 and March 2008 the (United Kingdom) National Patient Safety Agency received 12 reports of death and 15 of serious harm relating to chest drain insertion. All who insert chest drains must have been trained in the technique and be familiar with the equipment that they are using. Ultrasound localization (when available) is recommended to guide the insertion of drains for pleural fluid.

Lumbar puncture

Ensure that there are no contraindications to lumbar puncture (LP), namely raised intracranial pressure, bleeding tendency, local sepsis, posterior fossa, or spinal cord mass lesion.

The patient should be positioned on the bed (Fig. 30.2.15a) in the lateral decubitus position with their knees drawn up towards the chest to open the space between the spinous processes and with their spine parallel to the bed. Prepare and drape the skin and locate the puncture site (L3/L4 or L4/L5).

Fig. 30.2.15 (a) The patient should lie curled up to increase the space between the vertebrae. (b) The needle should be slowly advanced until it penetrates the ligamentum flavum.

Fig. 30.2.15 (a) The patient should lie curled up to increase the space between the vertebrae. (b) The needle should be slowly advanced until it penetrates the ligamentum flavum.

Anaesthetize the skin and subcutaneous tissues using 5 to 10 ml of 1% lidocaine (lignocaine). Insert the LP needle at 90° to the skin. Advance slowly, aiming between two spinous processes (Fig. 30.2.15b). As the needle enters the dural space, there is a slight loss of resistance. Remove the stylet and ensure that cerebrospinal fluid drips freely from the needle. If it does not, insert the stylet and advance the needle a few millimetres then check again.

Check the opening cerebrospinal fluid pressure using a manometer (normally 6–15 cmH2O) then collect cerebrospinal fluid samples. The red cell count in consecutive samples can sometimes help to distinguish subarachnoid haemorrhage from a bloody tap, but this is not always reliable and the sample should also be examined for xanthochromia (oxyhaemoglobin and bilirubin) when subarachnoid haemorrhage is possible. Always send blood samples for glucose and protein estimation at the same time, the cerebrospinal fluid glucose concentration normally being 60 to 80% of the blood level.

The patient should be asked to remain lying flat for 2 to 4 h to reduce the severity of post-LP headache.

Further reading

Temporary cardiac pacing

Fitzpatrick A, Sutton R (1992). A guide to temporary pacing. BMJ, 304, 365–9.Find this resource:

Gammage MD (2000). Electrophysiology: temporary cardiac pacing. Heart, 83, 715–20.Find this resource:

Pericardiocentesis

Tsang TS, et al. (1998). Echocardiographically guided pericardiocentesis: evolution and state-of-the-art technique. Mayo Clin Proc, 73, 647–52.Find this resource: