Anal sphincter

After administration of vasopressin for abdominal distention, a rectal tube may be ordered. The lubricated end of the tube is inserted past the anal sphincter and taped in place. The tube is left in place for 1 hour or as prescribed by the primary health care provider. The nurse auscultates the abdomen every 15 to 30 minutes and measures the abdominal girth every hour, or as ordered by the primary health care provider. 

Constipation can be due to primary and secondary causes (Table 18-1). Primary or idiopathic constipation is typified by normal-transit constipation, slow-transit constipation, and dyssynergic defecation. In the normal-transit type, colonic motility is unchanged and patients tend to experience hard stools despite normal movements. In the slow-transit type, motility is decreased leading to infrequent harder, drier stools. In dyssynergic defecation (also known as pelvic floor dysfunction), patients have lost the ability to relax the anal sphincter while coordinating muscle contractions of the pelvic floor. Some causes of secondary constipation are listed in Table 18-1. 

Check anal sphincter tone as an indirect assessment of peripheral innervation to the detrusor muscle of the bladder. 

Dyssynergic defecation A lack of coordination between the pelvic floor muscles and the anal sphincter. 

Rectal prolapse Sinking of the rectum through the anal sphincter so that it is visible externally. 

The patient experiences bladder and anal sphincter disturbances, constipation, diaphoresis, fatigue, olfactory disturbance, orthostatic blood pressure changes, pain, paresthesia, paroxysmal vascular flushing, seborrhea, sexual dysfunction, and sialorrhea (drooling). 

Q52 Glyceryl trinitrate may be used topically every 12 hours for anal fissures. Glyceryl trinitrate is a nitrovasodilator that causes the anal sphincter to relax when applied topically. 

Glyceryl trinitrate can be used topically in the treatment of anal fissures. Being a nitrovasodilator when applied topically, glyceryl trinitrate tends to cause relaxation of the anal sphincter. It is applied to the anal canal until the pain stops. 

Neurobiological components of colorectal and anal sphincter mechanisms and pathophysiology are similar to the above-mentioned vesical components. In both systems, central, peripheral, and autonomic nervous system reflexes, partly involuntary and partly voluntary, interweave critically for appropriate function. Function and control are mediated through the lower spinal cord, as well as via cortical centers requiring coordinated voluntary (and reflex) relaxation of external sphincters, (reflex) relaxation of internal sphincters, and simultaneous coordinated contraction of detrusor... 

Most of the time, the rectum is empty of feces. This is partly due to the fact that a weak functional sphincter exists approximately 20 cm from the anus at the juncture between the sigmoid and the rectum. However, when a mass movement forces feces into the rectum, the desire for defecation is normally initiated, including reflex contraction of the rectum and relaxation of the anal sphincters. 

Continual dribble of fecal matter through the anus is prevented by (1) tonic constriction of the internal anal sphincter, a circular mass of smooth muscle that lies immediately inside the anus, and (2) the external anal sphincter, composed of striated voluntary muscle that both surrounds the internal sphincter and also extends distal to it the external sphincter is controlled by the somatic nervous system and therefore is under voluntary control. 

Ordinarily, defecation results from the defecation reflexes, which can be described as follows. When the feces enter the rectum, distension of the rectal wall initiates afferent signals that spread through the myenteric plexus to initiate peristaltic waves in the descending colon, sigmoid, and rectum, forcing feces toward the anus. As the peristaltic wave approaches the anus, the internal anal sphincter is inhibited by the usual phenomenon of receptive relaxation, and if the external anal sphincter is relaxed, defecation will occur. This overall effect is the intrinsic defecation reflex of the colon itself. 

In the newborn baby and in some persons with transacted spinal cords, the defecation reflexes cause automatic emptying of the lower bowel without the normal control exercised through contraction of the external anal sphincter. 

In the patient presenting with a recent onset of constipation, an obstructing lesion of the colon should be sought. In addition to a colonic neoplasm, other causes of colonic obstruction include strictures due to colonic ischemia, diverticular disease, or inflammatory bowel disease foreign bodies or anal strictures. Anal sphincter spasm due to painful hemorrhoids or fissures also may inhibit the desire to evacuate. 

Vassilev and Radomirov (1992) used an isolated preparation of rat rectum. The rectal region, 1-6 cm proximal to the anal sphincter was removed and a 20 mm long segment suspended in an organ bath. The influence of prostaglandins and antagonists on spontaneous mechanical activity and electrically stimulated responses was investigated. 

Pethidine attracted attention as a possible analgesic because it caused the tails of laboratory mice to stand erect (Straub phenomenon), a characteristic of morphine-like drugs caused by spasm of the anal sphincter. 

Gut motor activity is increased and may cause colicky pain. Exocrine secretion is also increased. Tone in sphincters falls which may cause defaecation (anal sphincter) or acid reflux/regurgitation (oesophageal sphincter). 

Amyl nitrate can cause headache, flushing, hypotension, tachycardia, dizziness, and relaxation of the anal sphincter. Less commonly it causes fainting, stupor, vertigo, incontinence, dyspnea, glaucoma, and methemoglobinemia. 

Constipation is usual (SEDA-17, 79). The tone of the anal sphincter is increased and the usual reflex relaxation response to rectal distension is reduced. 

Users claim aphrodisiac effects from heightened stimulation, enhanced penile erection, and relaxation of the anal sphincter and rectum. Because of the rush of blood and oxygen to the brain, facial flushing and a temporary euphoria occur several seconds after inhalation. Perception of time is slowed. 

Ask the patient to breathe through his or her mouth to relax the anal sphincter. 

In the absence of fecal material, the rectum has a small amount of fluid, (about 2 m) with a pH about 7. The rectum is perfused by the superior, middle, and inferior hemorrhoidal veins. The inferior hemorrhoidal vein (closest to the anal sphincter) and the middle hemorrhoidal vein feed into the vena cava and back to the heart. The superior hemorrhoidal vein joins the mesenteric circulation, which feeds into the hepatic portal vein and then to the liver. 

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