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| Bernadette Findlay reported this case study as part of an Intensive Care Course at St. Vincent's Hospital Sydney during 1994. |
This case study of a 79 year-old male describes the diagnosis of abdominal aortic aneurism, the operative procedure required to repair the aorta, the nursing and medical management required to enable the patient to be discharged home with a minimum of complications.
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Mr C. (a pseudonym will be used to maintain patient confidentiality), is a 79 year old gentleman who was admitted to the intensive care unit for post operative management following repair of an abdominal aortic aneurism (AAA), commonly referred to as a triple A repair. The following case study will examine the diagnosis of his aneurism, the operative procedure required to repair the aorta and the nursing and medical management required to ensure that Mr C. was discharged home with a minimum of complications.
Aortic aneurisms are found in approximately 3-5% of persons over 65 years of age (Hallett, Naessens & Ballard, 1993: 690) and their incidence is increasing (Green & Duriel, 1994: 933). They are most often found in males, with the ratio being approximately 9:1, there is some evidence to suggest that their occurrence is familial (Green & Duriel, 1994: 933).
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Diagnosis of Mr C's AAA was made when investigations for an increase in lower back pain were conducted. Low back pain (or abdominal pain on lying down) is one of the more common symptoms that a patient may experience if an abdominal aortic aneurism is present (Miller, 1990: 167). Abdominal or flank pain may also be experienced, and occurs as a result of increased pressure on the lumber nerves, duodenum, the inferior vena cava and the small bowel (Munn, 1988: 40).
Confirmation of Mr C's aneurism was made by Computed Tomography (CT) scan. While diagnosis of an aneurism can be made by ultrasound, a considerably less expensive investigation than CT scanning, the CT scan provides greater information on the characteristics of the aneurism, since visualisation of the entire aorta is possible (Green & Duriel, 1994: 935). Mr C's CT scan showed an aneurism that was distal to the abdominal aorta. The aneurism was saccular in appearance and was approximately 4.5 cm in diameter. A large amount of thrombosis was present. VanRiper (1989: 115) states that 'a clinically significant aneurism measures at least 4 cm in diameter' and continues that the presence of thrombosis may compromise circulation and be a factor in aneurism rupture.
Mr C's aneurism was classified as infrarenal; that is, just below the renal arteries. Approximately 90% of AAA's arise within the abdominal aorta and are infrarenal (Romanini, Daly, Elliott et al. 1994: 246). Mr C's aneurism was saccular in shape (Figure 1). This is unusual since most infrarenal aneurisms are fusiform in appearance. A saccular aneurism is balloon-shaped with a narrow neck, bulges out from the main arterial segment and is the most likely to rupture (VanRiper, 1989: 115). Postmortem studies reveal that aneurism rupture is the third most common cause of sudden death (Geroulakos & Nicolaides, 1992: 616).
Figure 1: Saccular Aneurism
Surgery was determined as the most appropriate treatment for Mr C. At present the literature differs when recommending the management of small infrarenal AAA'S. Appropriate management 'is debatable because we have no clinical trials to indicate whether immediate operation or observation until enlargement is the best approach.' (Geroulakos & Nicolaides 1992: 616).
Hallett et al. (1993: 684) state that the repair of a small aneurism should be considered based on the following factors (1) low mortality rate (2) risk of aneurism growth and worsening operative risk (3) improved life expectancy. Green and Duriel (1994: 934) and Freischlag (1994: 539) support these considerations both reporting that low mortality rates favour resection of small aneurisms given the proper conditions. The recommendations for management may change upon completion of multi-centre studies that are currently being undertaken to address this question (Hallett et al. 1993: 685).
Mr C. had a history of ischaemic heart disease, with a previous myocardial infarction and was on regular antihypertensive medications. Hypertension is a significant risk factor for development of an aortic abdominal aneurism (Romanini et al., 1994: 243). In addition to this, Mr C had a history of supraventricular tachycardia (SVT) that was responsive to carotid sinus massage (CSM). A detailed cardiac history is important prior to undertaking a AAA repair since coronary artery disease is a major factor in both early and late mortality following surgery (Nagaoka, Innami, Funakoshi et al. 1992: 521). Investigations to assess Mr C's current cardiac status included: a gated heart pool scan, that established adequate left and right ventricular function, and electrocardiogram, that noted normal sinus rhythm with 1st degree heart block and a right bundle branch block.
Repair of Mr C's aorta was an uncomplicated procedure. A midline incision was made, the aneurism was resected and a gortex graft was inserted. The first dose of cephazolin was given intraoperatively to prevent infection. Cephazolin or any other drug from the antistapphylococcal group is the drug of choice (Romanini et al. 1994: 253). Mr C's intraoperative complications included hypertension and short runs of SVT that responded to CSM. Postoperatively, Mr C. was transferred to the Intensive Care Unit (ICU).
On admission to the ICU the priorities of airway, breathing and circulation were the nurses' foremost concerns. Mr C's airway was maintained with a Lanz endotracheal tube (ETT). This tube allows for high volumes with low pressures applied to the tracheal wall; thus, preventing the tracheal and mucosal damage that can be associated with intubation (Mallinckrodt 1985: 5). The Birds Mark 7 ventilator maintained respiration. Adequate ventilation was initially assessed by listening for equal air entry upon auscultation and noting equal chest wall movement. A saturation monitor was connected and oxygen concentrations were titrated to achieve an oxygen saturation of greater than 90%. Arterial blood gases (ABG's) were sent for analysis so that a quantitative assessment of adequate ventilation could be made. An erect chest X-ray was taken to confirm the correct position of the tube (top of the aortic notch) The tube was then cut and tied securely as per unit protocol (St. Vincent's ITU Procedure Manual 1991: 8.8/3). The chest X-ray was also used to confirm the correct position of the triple lumen central venous line and nasogastric tube. The initial post operative chest X-ray also provided the intensive care staff with information regarding the patients fluid status (Reading 1993: 2).
Pressure area care, mouth care and eye care are all especially important procedures that must be undertaken for the patient in the intensive care each was given as appropriate.
Mr C. was attached to a cardiac monitor to enable constant observation of the electrocardiography (ECG) rhythm. A 12 lead ECG showed no changes from the preoperative ECG. An arterial line was in situ and allowed for continuous blood pressure measurement.
Assessing for adequate circulation is of vital importance post AAA repair for a number of reasons that include, potential damage to the graft and impairment of peripheral circulation Hypotension should be avoided since inadequate perfusion may lead to graft thrombosis or occlusion (St. Vincent's ITU Procedure Manual, 1991: 2.10). Conversely, hypertension can also be especially dangerous as it may cause rupture of the new graft (Romanini et al., 1994: 249). Mr C was extremely hypertensive on his return from theatre. An infusion of sodium nitroprusside (SNP) was commenced. The infusion was titrated to maintain mean blood pressure limits between 90-110 mmHg.
SNP is a potent vasodilator that decreases both central venous pressure and arterial blood pressure. It does not alter cardiac output, its onset is rapid and its use is associated with few side effects (Rang & Dale, 1987: 260). The nursing responsibilities caring for a person with an SNP infusion are to ensure that it is given through a dedicated line that prevents accidental bolus dosage and it must be given via an infusion pump to ensure accurate dosage. Special darkened giving sets must be used and a protective covering placed over the infusion bag since in the presence of light it is converted to cyanide (Rang & Dale, 1987: 261).
In Mr C's case large doses of SNP were unable to adequately control his hypertension and he was becoming increasingly tachycardic, to supplement the SNP infusion hourly doses of metoprolol were commenced. Metoprolol (Betaloc) is a class II antidysrhythmic that is a cardioselective beta adrenoceptor blocking drug (specifically beta1 receptors) used in the treatment of hypertension (Astra Pharmaceuticals Product Information). It inhibits the transmission of sympathetic nerve impulses to the heart causing a decrease in heart rate and cardiac output but increases in cardiac volume and systolic ejection time (Dalgas, 1985: 61). The introduction of metoprolol allowed for better control of Mr C's cardiovascular status, and mean blood pressure limits could be maintained with decreased doses of SNP. Central venous pressure measurements were also recorded fourth hourly and provided further information regarding overall fluid status and right side heart function (Hudak, Gallo & Benz, 1990: 121).
Hourly assessment of circulation by limb observation was undertaken. Observations include checking for the presence of pulses, colour, warmth and movement. Mr C. had good pedal pulses but his feet were cool and capillary return was decreased. To encourage circulation, warm blankets were placed around the feet. Any adverse change in these observations would mean informing the medical staff since it could be the first sign of embolus or clot formation (Romanini et al., 1994: 251). Subcutaneous heparin was also administered as a prophylaxis against deep vein thrombosis or other clot formation (Luckmann & Sorensen, 1987: 1116).
Mr C had an indwelling catheter and hourly urine measurements were recorded. Any significant decrease in urine output would require medical intervention since renal failure can be a complication of this surgery (Green & Duriel, 1994: 939). The addition of a dopamine infusion is common in many patients post AAA repair. Dopamine acts to cause renal vasodilatation thereby increasing glomerular filtration rate and consequently renal output (Elliott 1994: 710). Mr C did not require dopamine since blood tests revealed normal renal function (Urea 4.6 mmol/L; Creatinine 0.07 mmol/L). Regular pathology tests were taken to ensure adequate renal function was maintained. Full blood counts, coagulopathy and other routine blood tests were also frequently undertaken to ensure normal pathology.
A nasogastric tube (NG) was in situ and regular aspirations were carried out to prevent gastric distension. In addition, gastric aspirate was checked for blood and pH was measured. Sucralfate was administered via the NG tube to help minimise the risk of developing a gastric ulcer. Sucralfate acts to protect the stomach from the 'potential ulcerogenic properties of acid, pepsin and bile' (MIMS Annual, 1993: 13).
Following any surgical procedure adequate pain control should always be maintained, in Mr C's case a morphine infusion was commenced. To ensure that appropriate levels of pain relief were maintained Mr C's response to painful procedures was graphed on the sedation chart used in the ICU, and the infusion rate was titrated according Mr C's level of pain (St. Vincent's Policy & Procedure Manual, 1991: 2.1013). Adequate pain control is important since it allows the patient to cooperate more fully with care, most especially with physiotherapy.
Development of infection is always a risk following any surgical procedure. Intravenous antibiotics were continued and Mr C's core temperature was monitored. Invasive sites were monitored regularly and showed no signs of inflammation or ooze. Regular suctioning via the ETT was undertaken to ensure that no lung secretions were able to pool and become a potential source of infection (Luckmann & Sorensen 1987: 703). A routine nasal swab was sent for microscopy, culture and sensitivity to check for any preexisting infection, especially multiresistant Staphylococcus aureus.
Assessment of neurological status is important postoperatively, since cerebrovascular accident is a serious complication of this surgery (Geroulakos & Nicolaides, 1992: 619). Neurologically Mr C was intact he obeyed commands and had full power in all limbs. Pupil size was equal and reacted briskly to light.
Another especially essential role of the nurse in the ICU is ensuring that adequate psychosocial care is given to the patient. Discussion and involvement of the patient's family can provide the intensive care staff with information that may be especially helpful in ensuring that the patient has a positive response to their time spent in the unit. Conversation with Mr C's wife revealed that Mr C. was generally very anxious and became easily stressed. It was important to note that Mr and Mrs C. were not from Sydney and the unfamiliar city provided an additional source of anxiety. It was especially important; therefore, that Mr and Mrs C. were given constant information regarding Mr C's care. Mr C was reassured that his operation had been successful and he was reoriented to time, day and place. Explanations were given prior to all procedures and information regarding progress was constantly updated. The inability to talk was explained and use of a communication board was encouraged. Mrs C was also reassured as to the success of the procedure and was encouraged to stay with her husband and assist nursing staff where possible.
Mr C was successfully extubated eight hours post repair of his aneurism and was placed on a Puritan mask at 8L/min. His extubation ABG's were acceptable and his oxygen requirements were decreased accordingly. Mr C's post operative night was complicated by episodes of SVT with rates of up to 200, CSM to which Mr C. has responded previously did not help. Mr C's blood pressure was not compromised. A 12 lead ECG was taken to detect the rhythm and displayed atrial flutter. Metoprolol is frequently beneficial in treating supraventricular tachyarrhythmias (Astra Pharmaceuticals, Product Information), however, it was not helpful in this instance. A loading dose of digoxin quickly reestablished sinus rhythm.
Mr C progressed well over the next twelve hours, but late in the evening had further episodes of SVT that were resistant to CSM, digoxin and metoprolol. He was commenced on an amioderone infusion. Amioderone acts to prolong the action potential and the refractory period of cardiac muscle (Rang & Dale, 1987: 247). It is commonly used in 'severe tachyarrhythmias not responsive to other therapy' (Reckitt & Coleman 1986, Product Information). It is important to note that amioderone must be added to a glass bottle, darkened giving sets are again required since amioderone is readily absorbed into PVC bags and infusion sets, administration must be via a dedicated line (Reekitt & Coleman 1986, Product Information).
Routine blood tests revealed a low haemoglobin (9 g/L), in addition to this, central venous pressure measurements were also low (4 cmH2O). 500 mL of NSA was given and a unit of packed cells were prescribed. Following administration of the blood over a period of one hour, it was noted that Mr C's oxygen saturation was falling and he was having difficulty in breathing. Oxygen therapy was increased. ABG's were taken and revealed poor oxygenation and an increased carbon dioxide level. A chest X-ray confirmed a diagnosis of pulmonary oedema. Continuous Positive Airway Pressure (CPAP) ventilation was commenced, and frusemide was administered, with the hope of initiating a diuresis (Rang & Dale, 1987: 323). Mr C's condition continued to deteriorate, requiring reintubation. To assist in mechanical ventilation, Mr C. was given small, bolus doses of midazolam 'a short acting central nervous system depressant that induces sedation, hypnosis, amnesia and anaesthesia' (MIMS Annual 1993: 3173).
A 12 lead ECG was also taken which showed no significant changes. A glyceryl trinitrate (GTN) infusion was commenced. GTN acts to decrease venous return to the heart and decrease myocardial oxygen demand (David Bull Laboratories, 1986).
At this point psychosocial intervention was especially important. Both Mr and Mrs C. needed to be reassured that reintubation was necessary to ensure Mr C's safety and that ventilation would be required until Mr C's pulmonary oedema resolved.
Postoperative Days Three - Ten.
Mr C. remained intubated for a further thirty-six hours and, following a chest X-ray that showed no evidence of pulmonary oedema, he was extubated. Monitoring in the ICU continued for a further 24 hours. On day five, Mr C. was discharged to the Coronary Care Unit where close observation of cardiac status could still be maintained. As Mr C continued to improve the GTN and amioderone infusions were ceased and Mr C. began mobilising around the ward area. Upon stabilisation of Mr C's cardiac status, he was discharged to the general ward area where he remained for three days prior to his discharge home.
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Following successful repair of his AAA, the patient can expect a survival rate that is not significantly different from that of the normal population (Stonebridge, Callam, Bradbury et al., 1993: 586). Despite Mr C's good prognosis, complications may occur. Prior to discharge both Mr and Mrs C. were instructed that any change in Mr C's leg colour, sensation or temperature required medical intervention. Abdominal pain or enlargement would also require medical attention. Mr C. will require regular medical observation of his cardiac status and should be aware that while rare, graft infection most commonly occurs two years following aneurism repair (Freischlag, 1994: 545).
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As has been shown, the repair of an abdominal aortic aneurism is a major procedure not only for the patient but also their family. Discharge with a minimum of complications can only be achieved through skilled medical and nursing intervention. Aneurism repair allows the patient to experience not only an increased quality of life, but provides them with greatly improved life expectancy.
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