The nurse is providing care to a patient with a spinal cord injury who has areflexic bladder

Clinical Manifestations

Immediately following SCI there is typically a period ofspinal shock with low tone and absent reflexes. Eventually signs of anupper motor neuron lesion may emerge, including spasticity and involuntary muscle spasms. However, if there is a substantial segment of spinal cord infarction present, patients may have persistent flaccid paralysis.

Children with neurologic levels of injury at T6 or above are at particular risk for interruption and decentralization of the autonomic nervous system. The most common manifestations include bradycardia, hypotension, temperature dysregulation, and, once spinal shock has resolved,autonomic dysreflexia (AD). AD is a sustained sympathetic response as a result of a noxious stimulusbelow the level of injury. Symptoms resulting from AD typically include hypertension, bradycardia, headache, and flushing of the skin above the level of injury, although vague symptoms such as fatigue, irritability, or crying may be the presenting symptoms in younger patients. Noxious stimuli are most often localized to bladder or rectal distention, but may include a number of other causes (Table 729.1). Children and adolescents with cervical and upper thoracic level SCI have lower baseline blood pressures compared with the general population. Therefore caution should be used when referencing age appropriate blood pressures, since blood pressure elevations of even 20-40 mm Hg above this lower baseline may be suggestive of AD.Identification and treatment of the noxious stimulus are typically associated with resolution of symptoms without the use of antihypertensive medication. If necessary, antihypertensive agents with a rapid onset and short duration, such as nifedipine and nitropaste, are advocated to treat elevated blood pressure while the underlying cause is identified (Fig. 729.2). Emergent management of AD is necessary due to the risk of stroke and additional organ damage resulting from sustained hypertension. Consideration of a medical alert bracelet, education of supervising adults, and carrying of an AD emergency reference card is recommended (Fig. 729.3).

Patients with SCI are particularly vulnerable todeep venous thrombosis andpulmonary embolism because of immobilization of their affected limbs. In children and youth, deep venous thromboses are more common in postpubertal children. Prophylactic treatment is recommended as soon as possible after an SCI (unless contraindicated because of the risk of bleeding or prior allergic response), including low-molecular-weight heparin, graduated compression stockings, and sequential calf compression devices for older children and adolescents. Late-occurring deep venous thrombosis most commonly occurs with prolonged immobilization related to illness or surgery, and prophylactic measures should be continued during these situations as well.

Consequent of SCI, patients often present with varying degrees of bowel and bladder incontinence. Following a SCI, the bladder can be areflexic or hyperreflexic and detrusor sphincter dyssynergia may occur. Clean intermittent catheterization (CIC) of the bladder is typically performed up to 4-6 times/day to prevent urinary retention and vesicoureteral reflux. Constipation can negatively impact the success of a CIC program. Anticholinergic medications may improve bladder storage capacity and prevent urinary incontinence between bladder catheterizations. Antibiotics are recommended for symptomatic urinary tract infections; asymptomatic bacteriuria, without vesicoureteral reflux, is generally due to colonization and typically not treated. Functional independence with bladder and bowel management should be promoted when developmentally appropriate.

PROBLEM ANALYSIS

Autonomic Dysreflexia

First described byGuttmann and Whitteridge in 1947, autonomic hyperreflexia (autonomic dysreflexia) is a potentially fatal emergency unique to the SCI patient. Excellent source materials include the reviews byTrop and Bennett (1991),Vaidyanathan et al. (1998), andKarlsson (1999).Autonomic hyperreflexia represents an acute massive disordered autonomic (primarily sympathetic) response to specific stimuli in patients with SCI above the cord level of T6 to T8 (the sympathetic outflow). It is more common in cervical (60%) than thoracic (20%) SCI. Onset after injury is variable—usually soon after spinal shock, but it may occur up to years after injury, and distal spinal cord viability is a prerequisite.

Symptomatically, autonomic hyperreflexia is asyndrome of exaggerated sympathetic activity in response to stimuli below the level of the lesion. The symptoms include pounding headache, hypertension, and flushing and sweating of the face and body above the level of the lesion. Bradycardia is a typical accompaniment, although tachycardia or arrhythmia may occur. Hypertension may vary in severity from causing a mild headache before voiding to life-threatening cerebral hemorrhage or seizure.

The stimuli for this exaggerated response commonly arise from the bladder or rectum and typically involve distention. Precipitation may be the result of simple LUT instrumentation, tube change, catheter obstruction, or clot retention, and in such cases the symptoms resolve quickly if the stimulus is withdrawn. Additional causes or exacerbating factors may include other upper urinary tract or LUT pathology (e.g., calculi), gastrointestinal pathology, long bone fracture, sexual activity, electrocoagulation, and decubitus ulcers. Risk factors for autonomic dysreflexia during urodynamic evaluation include complete injury, cervical-level of injury, presence of detrusor sphincter dyssynergia, poor bladder compliance, and more than 2 years since injury (Liu et al., 2017).In addition, with more SCI patients participating in athletic pursuits, the instigation of this condition related to sports activities is also being increasingly recognized (Krassioukov, 2012).

DSD invariably occurs, and, at least in males, smooth sphincter dyssynergia is also usually a part of the syndrome. The pathophysiology is that of nociceptive stimulation via afferent impulses that ascend through the cord and elicit reflex motor outflow, causing arteriolar, pilomotor, and pelvic visceral spasm and sweating. Normally, the reflexes would be inhibited by secondary output from the medulla, but because of the SCI this does not occur below the lesion level.Vaidyanathan et al. (1998) emphasized that the SCI disrupts control of the sympathetic preganglionic neurons because bulbospinal input has been lost, and the remaining regulation is accomplished by spinal circuits consisting of dorsal root afferent and spinal interneurons.Karlsson (1999), however, points out that the underlying pathogenic mechanisms may not be as simple as they first appear. The amplitude of the blood pressure reaction indicates involvement of a large vascular bed, perhaps larger than that of the skin and skeletal muscle. It may be that the splanchnic vascular bed is involved as well, either from the standpoint of active vasoconstriction or simply from a lack of the ability to exhibit compensatory vasodilatation. Afferent and efferent plasticity in the sympathetic nervous system (SNS) may also be involved.

PROBLEM ANALYSIS

Autonomic Dysreflexia

Acute episodes of AD are characterized by acute elevations in blood pressure coupled with bradycardia, although tachycardia has been known to occur. They usually occur with injury at T6 and above. Systolic blood pressure elevations of 20–30 mm Hg signify a dysreflexic episode. Cervical or high thoracic injuries can place a baseline systolic blood pressure 15–20 mm Hg lower; thus dysreflexic episodes can typically mimic healthy or slightly elevated blood pressure readings. Sympathetic discharge is the source behind these episodes. The symptoms of a rise in blood pressure have varied consequences, from being asymptomatic (mild discomfort, headache, blurred vision) to being life threatening (seizures, intracranial or subarachnoid hemorrhage, death, retinal detachment). Vasoconstriction occurs from sympathetic activation, so dry, pale skin is often observed below the lesion. Above the lesion, intact baroreceptor reflexes initiate a parasympathetic response responsible for bradycardia, as well as sweating, piloerection, and flushing above the level of injury. Once an episode has occurred, the risk for another episode occurring in the next 24–72 hours is increased. A higher percentage of cases exists in high injuries and complete SCIs. In SCI, supraspinal input in the form of inhibitory and excitatory vasomotor pathways to the sympathetic preganglionic neurons are disrupted, and thus unstable blood pressures are found to occur. Stimulation of the urinary bladder or colon has been known to trigger these events. Symptoms are usually brief, either from termination of the episode by treatment or the self-limiting nature of the episode. Alterations have been suspected to occur in the spinal and peripheral autonomic circuits.

The clinical guidelines used for treating a patient with acute episodes of AD focus on an algorithm, with monitoring of blood pressure and heart rate after each step. The first step in caring for a patient suffering from an acute episode of AD should be to place the patient in a sitting position. Second, the patient needs to be inspected for areas of constriction (including clothing). Third, an indwelling catheter should be placed to relieve bladder distention. If a Foley catheter is in place, potential regions of kinks or obstruction should be investigated. Systolic blood pressure is measured after this step, and if the value is greater than 150 mm Hg, a fast-acting short-duration antihypertensive agent is considered. Usually, nifedipine, nitrates, and captopril have been shown to be beneficial in the acute setting. To date, only nifedipine has been studied in controlled trials for AD. Once blood pressure is within an acceptable range (<150 mm Hg), fecal disimpaction can begin. If neither indwelling catheterization nor bowel disimpaction alleviate symptoms, other potential causes should be sought after, but an admission to the hospital is likely needed first to stabilize thepatient’s blood pressure. After control of symptoms, the patient should be observed for 2 hours to make sure another episode does not recur.

Pathophysiology

Autonomic dysreflexia occurs in 48–90% of patients with spinal cord injury (SCI) above the splanchnic sympathetic outflow. It usually manifests 3–4 months after SCI, but it may occur as early as the fourth day and as late as 12 years postinjury. A lesion at or above the T6 level disconnects the caudal spinal region, including splanchnic sympathetic outflow, from supraspinal control. Experimental and clinical studies demonstrate morphological and physiological changes above and below the injury. There is remodeling of synapses and increased reactivity rostral to the lesion. The vagus nerve is usually unaffected. Caudally, there is degeneration of descending tracts, sprouting of ascending sensory fibers, a decrease in inhibitory neurotransmission, an increase in calcitonin gene-related peptide and substance P, and reduction of γ-amino-butyric acid. Peripherally, potentiation of neurovascular transmission may be due to decentralization, adrenoceptor supersensitivity, altered adrenoceptor density, increased smooth muscle reactivity, increased norepinephrine release, and decreased synaptic norepinephrine uptake. The muscle and skin sympathetic activity is markedly reduced at rest; on stimulation, it shows parallel instead of sequential activation. Visceral or somatic, noxious or innocuous stimulation below the lesion is carried by pelvic parasympathetic, pudendal somatic, and hypogastric sympathetic (T9 or higher) afferents to the spinal cord. During its ascent in the dorsal and spinothalamic tracts to the lesion level, collateral branches activate the intermediolateral column neurons. An increased norepinephrine ‘spillover,’ coupled with target organ hyper-responsiveness, causes hypertension. The blood pressure elevation activates baroreflexes (cartoid sinus and aortic body→glossopharyngeal and vagus nerves→medulla→heart and blood vessels) to produce vagally induced bradycardia and vasodilation.

Treatment

Treatment for autonomic dysreflexia needs to be individualized since it may occur in minor episodes that do not require treatment or it may be severe and life threatening. An acute episode with a markedly elevated blood pressure constitutes an emergency, and recurrent attacks of autonomic dysreflexia, if unrecognized and inconsistently treated, can lead to serious neurological, cardiac, and renal complications.

Primary pharmacological prophylaxis is usually not indicated, but appropriate care of bowel, bladder, and skin is essential. Premedication before urological procedures with sublingual nifedipine or oral mecamylamine is recommended in patients with suspected or documented autonomic dysreflexia. Nifedipine is the currently favored agent. It inhibits voltage-dependent Ca2+ channels in vascular smooth muscle and selectively dilates arterial resistance vessels. The contents of a 10-mg capsule are squeezed under the tongue. Mecamylamine, a ganglionic blocking agent, is given in a dosage of 2.5 or 5 mg three times a day to reduce sympathetic and parasympathetic responses.

A systematic approach is indicated when a patient presents with symptoms of autonomic dysreflexia. Blood pressure should be checked. If blood pressure in not elevated, monitoring of symptoms and blood pressure should be continued for 2 hr. If blood pressure is elevated but does not exceed 150/100 mmHg, the patient should be made to sit up to lower blood pressure and all clothing should be loosened. The catheter tubing should be checked to determine whether urine is flowing out from the bladder and to ensure that there are no kinks, or the patient should be catheterized after instilling 2% lidocaine jelly into the urethra. The bowels should be emptied if no cause is found in the urinary tract. Also, a search for pressure sores and ingrown toe nails should be made.

Blood pressure should be reassessed if no cause is found. If blood pressure elevation does not exceed 150/100 mmHg, the patient should continue to be observed. If hypertension exceeds 150/100 mmHg and a cause is either not found or found but not feasible to eradicate quickly, pharmacological treatment should be initiated.

If blood pressure elevation is between 150/100 and 180/120 mmHg, the patient should be treated with sublingual nifedipine, oral mecamylamine, or oral clonidine. Clonidine reduces sympathetic drive by activating α2 adrenoreceptors in the lower brainstem.

If blood pressure exceeds 180/120 mmHg, drugs that directly relax smooth muscle are used. They are administered intravenously for a quick response. These include hydralazine, nitroprusside, and diazoxide. Hydralazine, which directly relaxes the arteriolar smooth muscle, is administered as a 10- to 20-mg dose by slow intravenous push. Nitroprusside dilates arterioles and venules and its dose can be adjusted from 0.25 to 1.5 μg/kg/min. Diazoxide acts by hyperpolarizing arterial smooth muscle cells. Its dosage ranges from 50 to 300 mg.

In patients with recurrent life-threatening autonomic dysreflexia in whom no cause is found, radical measures may be necessary, including pudendal and sacral nerve blocks, pelvic or pudendal nerve section, sacral posterior rhizotomy, sympathectomy, subarachnoid block with alcohol or phenol, dosal root ganglionectomy, and even cordectomy.

Autonomic Dysreflexia

Autonomic dysreflexia (AD) is a condition resulting from excessive sympathetic outflow in response to a noxious stimulus; the outflow is unregulated because of interruption of neural pathways after spinal cord injury. People with spinal cord injuries at the level of T6 and above are at risk for AD. The most common noxious stimuli that lead to AD include tight clothing, urinary or fecal retention, renal or bladder stones, pressure ulcers, infections, or intraabdominal pathology. In addition, “boosting” is the practice of intentionally inducing AD by athletes for the purpose of improving athletic performance.

Autonomic Dysreflexia

Autonomic dysreflexia (AD) occurs in patients with SCIs typically of T6 or higher and is characterized by acute hypertension and bradycardia. Typically, a noxious stimulus below the level of the cord lesion triggers AD (e.g., surgery, bladder catheter manipulation) (Fig. 16.7). AD results from unopposed sympathetic efferent outflow (extreme vasoconstriction; cool, pale skin; and severe hypertension) as a result of noxious stimuli below the spinal cord lesion, leading to reflex activation of parasympathetic outflow (bradycardia, cutaneous flushing) above the spinal cord lesion. Unopposed vasoconstriction persists because of blocked inhibitory responses at the spinal cord lesion. AD typically occurs 1 to 6 months after injury, but it can occur acutely after SCI. Regarding cardiac patients, severe hypertension is a major concern. It can lead to worsening myocardial ischemia, congestive heart failure, and occasionally cerebral hemorrhage. Prevention of AD can be accomplished with a deep regional block (spinal or PNB for lower extremity surgery; epidural block may be less effective due to sacral nerve sparing) or deep inhalation anesthesia. Treatment involves cessation of the noxious stimulus, deepening the anesthetic, and using antihypertensives. For cardiac patients and any patient in whom the index of suspicion is high for AD occurring, invasive arterial blood pressure management should be used with immediate treatment plans in place.

Autonomic Dysreflexia

AD is defined as a syndrome of massively uncontrolled sympathetic nervous system discharge that is unique to patients who have sustained an SCI (Figure 3-1). It is characterized by a sudden and exaggerated reflex and with an increase in blood pressure. The mechanism of this syndrome begins with patient exposure to noxious stimuli such as pain or pressure below the level of injury. A signal is sent through a sympathetic pathway, which triggers an exaggerated reflex (e.g., vasoconstriction and a subsequent increase in blood pressure). Baroreceptors in the aorta sense this increase in blood pressure and send a signal to the brainstem, which in normal physiologic conditions responds by transmitting a signal for vasodilatation and a slowing of the heart rate. These signals are interrupted by the spinal cord lesion and, as a result, no compensatory action occurs. The blood pressure remains elevated and the cycle continues until noxious stimuli are removed.

AD occurs in patients with injuries at T6 or above, but rarely occurs during the acute phase after SCI. In general, the onset of AD begins after the resolution of spinal shock. Prevalence estimates vary from 66% to 85% of patients with lesions at or above T6.12 Symptoms of AD include the following (see Box 2-4):

Hypertension (systolic pressure possibly as high as 300 mm Hg)

Headache: severe or pounding

Perspiration: above the level of injury

Flushing: above the level of injury

Piloerection: below the level of injury

Vision: blurred; dilated pupils

Nasal congestion

Anxiety

Bradycardia

Because AD is typically seen only in patients with SCI, clinicians who do not regularly work with these individuals may fail to recognize symptoms, delaying critical treatment. There are many causes of AD (Box 3-1). Determining the cause is essential so the reflex can be stopped by removing the stimuli at the source.

Treatment of AD involves a number of interventions (Box 3-2). The administration of nitroglycerin as a topical paste is typically the first step, followed by having the patient bite and swallow nifedipine to reduce the blood pressure. Xylocaine 2% jelly is used if the nurse is checking for fecal impaction or changing or inserting a urinary catheter. In addition, note that problems with temperature regulation may follow an incidence of AD because the dysreflexia can result in the patient sweating with heat loss and then being unable to compensate with resultant shivering. Interventions to correct the hypothermia may be required.

Preventive measures for AD are critical and reduce the chance that noxious stimuli will occur. Ensuring that clothing is loose, the bladder is nondistended, the bowel program is effective, linen under the patient is smooth, and podiatric care is regularly performed (to prevent ingrown toe nails) all help limit the possibility that AD will develop. The patient and family must be taught to recognize the symptoms of AD and to either take action or instruct care providers to take action. In addition, patient and family education needs to focus on reducing the risk of AD by using the prevention strategies discussed above.

A number of complications can result if AD goes untreated. The patient may have retinal hemorrhages. A more serious complication may be a subarachnoid or intracranial hemorrhage, potentially resulting in a cerebrovascular accident. Myocardial infarction is also a potential complication and, in some cases, AD may be fatal.