Regional anaesthesia in the elderly patient
There are approximately 10 million people (16% of the total population) over the age of 65 living in the UK; this figure is projected to double by 2050. Elderly patients contribute to a large proportion of the NHS workload.
1 Physiological changes in the elderly patient
2 Preoperative management and optimization
3 Methods of delivering safe anaesthesia to the elderly trauma patient
4 Care of the insensate limb.
2A03; 2G01, 2G02
You are to anaesthetize an 85-year-old lady who sustained a fractured left neck of femur after having fallen yesterday morning. She is to undergo a left dynamic hip screw (DHS). She is the first patient on your list this morning.
Ageing affects all the systems within the body. Changes to the cardiovascular, respiratory, and renal systems have the greatest relevance to anaesthesia.
There is a linear decline in cardiac function. An 80-year-old has half the cardiac output of a 20-year-old. Decreased sensitivity to catecholamines and increased myocardial stiffness decrease contractility, and a progressive stiffening of the thoracic aorta leads to increased afterload. These factors, combined, lead to an overall reduction in stroke volume.
Large and medium-sized vessels stiffen with age, resulting in increased systolic and diastolic blood pressure. The raised SVR may lead to LV hypertrophy and strain. Hypertension is the most common cardiovascular manifestation of ageing. The autoregulation curve is shifted to the right (as a result of hypertension), rendering the elderly less tolerant of low MAPs. Autonomic and baroreceptor downregulations mean there is an impaired/blunted response to hypotension.
There is a greater proportion of coronary artery disease in the elderly population; however, this may not manifest symptomatically, as the patients may not be able to exert themselves to such an extent. Arrhythmias are commonplace also, due to a decrease in the number of cardiac-conducting cells and increased fibrous tissue deposition. Atrial fibrillation (AF) has a prevalence of 5.5% in the over 65s; it is an important comorbidity to be aware of, as it further reduces cardiac output by 30%. Arrhythmias are more commonly seen in those with heart valve lesions.
Vital capacity, forced expiratory volume in 1 s (FEV1), and forced vital capacity (FVC) all decrease with advancing age; residual capacity and closing capacity both increase. The increased closing capacity encroaches upon an unchanged functional residual capacity by the age of 65, leading to dependent airway closure and ventilation/perfusion (V/Q) mismatch. Chest wall and lung compliance is reduced, resulting in decreased peak flows.
A V/Q mismatch, along with decreased mucociliary clearance, leads to atelectasis, secretion pooling, and a greater incidence of pneumonia. Immobilization and dehydration are factors in developing pulmonary emboli (PEs) perioperatively. Blunted ventilatory responses to hypoxaemia and hypercapnia make both of these complications more common post-operatively. The edentulous airway may make manual bag–mask ventilation challenging.
Reductions in cardiac output, coupled with increased atherosclerotic disease, lead to a linear decrease in renal function with age. Creatinine (Cr) clearance falls; however, due to reduced Cr production, serum Cr remains unchanged. Handling of renally cleared drugs (aminoglycosides, penicillins, digoxin) is impaired, lengthening their half-lives.
Care must also be taken with fluid balance. Elderly patients are often hypovolaemic preoperatively, increasing the risk of complications such as intraoperative hypotension and venous thromboembolism (VTE). Vigorous IV fluid administration may be poorly tolerated, due to poor cardiorespiratory reserve, leading to accumulation within the lungs and pulmonary oedema.
Declining cognitive function can make obtaining consent challenging. Often a patient with impaired cognition may not be compliant with treatment, as they are incapable of understanding the nature of their condition.
The changes brought about by illness and a change of environment can lead to cognitive decline. Post-operative cognitive dysfunction (POCD) is a common phenomenon, affecting approximately 25% of patients over 60 years undergoing major surgery. POCD is multifactorial, with anaesthetic agents and sedatives having been implicated. However, there is no difference in incidence between those undergoing general and regional anaesthesia.
You see the patient preoperatively. She is moderately confused, with a background of mild dementia. She states she takes some tablets for her heart (aspirin, bisoprolol, bendroflumethiazide, simvastatin, and irbesartan). Her pain score is 3/10 at rest, after having received some opioid analgesia. On auscultation of her chest, you hear a previously undiagnosed non-radiating ejection systolic murmur and an irregular pulse of 110 bpm.
The overriding principle is to ensure the patient is optimized for safe surgery in the most prompt manner by avoiding unnecessary delay. This is achieved by:
1 Evaluation of the patient and their comorbidities
2 Prompt instigation of the required investigations
3 Ensuring analgesia
4 Prevention of other further comorbidity (VTE, pressure sores, infection).
In addition to their presenting complaint, elderly patients will commonly present to hospital with a number of other comorbidities. Often these comorbidities are well established, and records relating to their management and history can be obtained (collateral histories, GP or hospital records). Undiagnosed cardiac conditions, such as this patient’s murmur, are not uncommon events, especially as elderly patients often cannot exert themselves to the point of becoming symptomatic.
A thorough evaluation of the patient must be made to ascertain whether they are fit for surgery. It is important to know the patient’s main comorbidities and be able to judge if these are stable. Any delay in surgery must be justifiable and be seen to confer some advantage to the patient. Unnecessary delays increase the duration of immobilization, which may lead to pulmonary infection, pressure sores, and VTE.
Most inpatients with a fractured neck of femur will undergo the important investigations soon after admission. Routine bloods (including coagulation profile), a CXR, and an ECG will be sufficient in most patients.
Murmurs are a common finding in the elderly. Aortic sclerosis is by far the most common anomaly causing an ejection systolic murmur. The availability of a rapid echocardiography is an important factor. An asymptomatic patient with a recent echocardiogram is unlikely to benefit from a repeat scan and may come to harm from a delay to surgery. However, if aortic stenosis is suspected, an echocardiography is recommended to confirm diagnosis and stratify risk.
Maintaining patient comfort can be challenging, especially for the immobilized patient. Patients may have had their affected limbs placed in traction by the surgeons; this measure was intended to relieve pain, although there is no evidence of any analgesic benefit. Therefore, limb traction is not recommended in patients with hip fractures. Careful titration of IV opioids remains the best analgesic option preoperatively. Peripheral nerve blocks can be used preoperatively, but it is unclear if this exerts any reduction in opioid administration.
Hip fracture patients are at increased risk of other significant morbidities. Hospital-acquired respiratory tract infections (HAI) and VTE contribute to increased duration of hospital stay, morbidity, and mortality. Prophylactic antibiotics are recommended, not only for surgical site infections, but also to help prevent HAIs.
The use of pharmacological thromboprophylaxis reduces the incidence of VTE to 1.34%. The regime used is dependent on local guidelines. Enoxaparin can be commenced soon after admission, stopped 12 hours prior to surgery, and recommenced 6 hours post-operatively. Fondaparinux compares favourably to enoxaparin; this can be commenced 6 hours post-operatively. There is benefit seen if thromboprophylaxis treatment is extended to 28–35 days after surgery. Mechanical compression devices should also be considered if the patient tolerates them.
A thorough preoperative work-up not only decreases the risk of untoward events in the perioperative period, but also has positive implications for earlier discharge and decrease morbidity and mortality once out of hospital. Surgery must not be delayed for investigations that are not vital or are unlikely to change management.
You are happy the patient has been adequately optimized for surgery. You were able to get an echocardiographic scan without delay, which showed the patient has aortic sclerosis and moderate LV function.
The options available include general anaesthesia, with or without a regional technique, or regional anaesthesia coupled with conscious sedation. There is little evidence that one technique has significant advantages over the other. However, regional anaesthesia does decrease the amount of IV opioid required post-operatively and may reduce post-operative cognitive deficit; for these reasons, the use of regional anaesthesia is commonplace for hip surgery in the elderly.
Regional anaesthesia is best attempted with the patient awake and able to respond to any paraesthesiae or pain on injection, alerting the operator to possible intraneural injection. However, needle phobia and pain at the injection site understandably cause anxiety to the patient. This, plus the likelihood of confusion/disorientation in the elderly patient, means that conscious sedation plays an important role in delivering safe and satisfactory treatment.
There are multiple sedating agents available. Sedation requires IV access to be obtained and is normally commenced prior to block placement. The ideal sedative should have rapid onset/offset, be easily titratable, have minimum ‘hangover’ effect, in addition to having anxiolytic, amnesic, and analgesic properties. Although no absolutely perfect sedative exists, midazolam and propofol are the two agents which appear to have the most favourable properties. Midazolam offers excellent amnesia and is easily administered by careful bolus. However, it does cause respiratory depression and can cause paradoxical reaction. Propofol offers excellent sedation, is easily titrated by TCI, and has a rapid offset. The amnesia offered by propofol is dose-related and less effective than that seen with midazolam. Local policy and protocol will likely decide which agent is used.
Commonly, the regional technique recipe is with a low-dose spinal (e.g. 1.5–2 mL of 0.5% levobupivacaine), done with the patient in decubitus position, followed by a femoral nerve block (e.g. 0.5% levobupivacaine, up to a maximum total dose of 2 mg/kg). The spinal confers early operative analgesia, until the nerve block is fully effective, which subsequently ensures continuing intraoperative and post-operative analgesia. This technique allows for an opioid-free anaesthetic. Other options are also available, such as femoral nerve block combined with lateral cutaneous nerve block and placement of femoral nerve catheters (see Figure 4.7).
Full monitoring is required to detect any haemodynamic compromise. Oxygen therapy is commenced by face mask, preferably with ETCO2 monitoring. Verbal contact with the patient should elicit a response at all times. Antibiotics, simple analgesia, and antiemetics should all be given, as per local policy. Blood loss and fluids infused should be recorded and post-operative instructions clearly documented.
The patient remains comfortable throughout the procedure and is safely transferred to recovery. At the end of the list, you go to the ward to see her. The femoral block you have placed seems to be working well, and she is still comfortable. The left leg is still immobile and numb.
Patients may poorly tolerate the motor and sensory block caused by regional anaesthesia. It is important to brief the patient preoperatively regarding the expected duration of the block to alleviate any concern they may have. It is also important to ensure surgeons and nursing staff are aware of the details of the block.
Local protocols should include regular observation of the insensate limb, checking for sensory block and limb movement. An increasing level of block is always a cause for concern, and a clinician should be informed immediately.
The limb must also be checked for pressure areas. The development of pressure sores in patients who may have pre-existing malnourishment can lead to marked comorbidity and hospital stay. Patients should be cared for on low-pressure, foam-based mattresses and pressure areas relieved regularly.
As the insensate limb is usually immobile, VTE prophylaxis should be commenced in a timely manner. Pharmacological prophylaxis should be prescribed 6 hours post-surgery.
Early mobilization is a priority, once the motor function and sensation have returned to the limb. Initial mobilization must be taken with care, as there may be some residual block remaining. Two members of staff must help mobilize the patient, in case she fails to weight-bear.
Any concerns about the nerve block must be referred to the acute pain service or anaesthesia staff.
Summary
Caring for elderly patients in the perioperative period can be challenging. They will often present with several comorbidities. A key part of your role is to ensure they are fit for surgery, whilst minimizing unnecessary delay.
Bjorvatn A and Kristiansen F (2005). Fondaparinux sodium compared with enoxaparin sodium: a cost-effectiveness analysis. American Journal of Cardiovascular Drugs, 5, 121–30.
Furberg CD, Psaty BM, Manolio TA, Gardin JM, Smith VE, and Rautaharju PM (1994). Prevalence of atrial fibrillation in elderly subjects (the Cardiovascular Health Study). American Journal of Cardiology, 74, 236–41.
Hanning CD (2005). Postoperative cognitive dysfunction. British Journal of Anaesthesia, 95, 82–7.
Höhener D, Blumenthal S, and Borgeat A (2008). Sedation and regional anaesthesia in the adult patient. British Journal of Anaesthesia, 100, 8–16.
Mak JCS, Cameron ID, and March LM (2010). Evidence-based guidelines for the management of hip fractures in older persons: an update. Medical Journal of Australia, 192, 37–41.
Murray D and Dodds C (2004). Perioperative care of the elderly. Continuing Education in Anaesthesia, Critical Care & Pain, 4, 193–6.
National Institute for Health and Clinical Excellence (2010). Venous thromboembolism: reducing the risk. NICE clinical guideline 92. Available at: <http://www.nice.org.uk/nicemedia/pdf/CG92NICEGuidelinePDF.pdf>.
NHS National Services Scotland (2008). Clinical decision-making: is the patient fit for theatre? A report from the Scottish Hip Fracture Audit. Available at: <http://www.shfa.scot.nhs.uk/Theatre_Delay_Report.pdf>.
Otto CM, Lind BK, Kitzman DW, Gersh BJ, and Siscovick DS (1999). Association of aortic-valve sclerosis with cardiovascular mortality and morbidity in the elderly. New England Journal of Medicine, 341, 142–7.
Parker MJ, Griffiths R, and Appadu BN (2002). Nerve blocks (subcostal, lateral cutaneous, femoral, triple, psoas) for hip. Cochrane Database of Systematic Reviews, 1, CD001159.
Rosencher N, Vielpeau C, Emmerich J, Fagnani F, and Samama CM; ESCORTE group (2005). Venous thromboembolism and mortality after hip fracture surgery: the ESCORTE study. Journal of Thrombosis and Haemostasis, 3, 2006–14.
Ross GR and Seeqmiller JE (1981). Age-related physiological changes and their clinical significance. Western Journal of Medicine, 135, 434–40.
Scottish Intercollegiate Guidelines Network (2009). Management of hip fracture in older people. A national clinical guideline. Available at: <http://www.sign.ac.uk/pdf/sign111.pdf>.