Morphine hypotension

Morphine Hypotension, respiratory depression BP and RR 5 minutes after each bolus dose... 

Morphine has certain undesirable side effects. Among these are respiratory depression, nausea, and vomiting, depression of the cough reflex, cardiovascular depression and hypotension, smooth muscle contraction (constipation), and histamine release (93). Morphine s onset of action, duration, and low therapeutic indices have prompted a search for a more effective opiate iv anesthetic. Extreme simplification of the complex morphine molecule has resulted in anilido —piperidines, the fentanyl class of extremely potent opiate iv anesthetics (118,119). 

RISK FDR INJURY. Narcotics may produce orthostatic hypotension, which in turn results in dizziness. The nurse should assist the patient with ambulatory activities and with rising slowly from a sitting or lying position. Miosis (pinpoint pupils) may occur with the administration of some narcotics and is most pronounced with morphine, hydro mo rpho ne, and hydrochlorides of opium alkaloids. Miosis decreases the ability to see in dim light. The nurse keeps the room well lit during daytime hours and advises the patient to seek assistance when getting out of bed at night. 

Epidural analgesia is frequently used for lower extremity procedures and pain (e.g., knee surgery, labor pain, and some abdominal procedures). Intermittent bolus or continuous infusion of preservative-free opioids (morphine, hydromorphone, or fentanyl) and local anesthetics (bupivacaine) may be used for epidural analgesia. Opiates given by this route may cause pruritus that is relieved by naloxone. Adverse effects including respiratory depression, hypotension, and urinary retention may occur. When epidural routes are used in narcotic-dependent patients, systemic analgesics must also be used to prevent withdrawal since the opioid is not absorbed and remains in the epidural space. Doses of opioids used in epidural analgesia are 10 times less than intravenous doses, and intrathecal doses are 10 times less than epidural doses (i.e., 10 mg of IV morphine is equivalent to 1 mg epidural morphine and 0.1 mg of intrathecally administered morphine).45... 

Morphine produces venous and arteriolar dilation, which may result in orthostatic hypotension. Hypovolemic patients are more susceptible to morphine-induced hypotension. Morphine is often considered the opioid of choice to treat pain associated with myocardial infarction, as it decreases myocardial oxygen demand. 

Clinical reports of patients who underwent chloroform anesthesia indicated that premedication with morphine caused serious respiratory depression when chloroform was co-administered. Thiopentone (thiopental Na, an ultra-short-acting barbiturate anesthetic) was associated with increased incidences of hypotension in chloroform-anesthetized patients (Whitaker and Jones 1965). 

Q87 Morph ine should not be used for pain relief in myocardial infarction. Morphine may induce hypotension as a side-effect. 

Less potent opioids have fallen into disfavor because of the prominence of the untoward effects they produce when given in high doses. Meperidine hydrochloride (Demerol) causes tachycardia, while morphine produces hypotension and bronchoconstriction as a consequence of its histamine-releasing action. 

Respiratory depression, miosis, hypotension, and coma are signs of morphine overdose. While the IV administration of naloxone reverses the toxic effects of morphine, naloxone has a short duration of action and must be administered repeatedly at 30- to 45minute intervals until morphine is cleared from the body. 

CNS side effects include confusion, anxiety, lethargy, nausea and vomiting. GIT related effect is constipation. Other side effects are urinary retention, dry mouth, miosis, dysphoria, hypotension, skin rash, itching and urticaria. Tolerance, drug dependence and drug abuse are the main drawbacks of morphine. 

In hypotensive states, more fall in blood pressure occurs due to morphine. 

Hyperpyrexia and hypertension have been observed with the use of pethidine and MAO inhibitors. Pethidine is the opioid most commonly associated with an adverse reaction with MAOIs. Although only a small proportion of patients taking MAOIs will react adversely to pethidine, there is no sure way of predicting those in whom the combination could produce severe, life-threatening reactions. These can present in two distinct forms. The excitatory form is characterised by sudden agitation, delirium, headache, hypotension or hypertension, rigidity, hyperpyrexia, convulsions and coma. It is possibly caused by an increase in cerebral 5-HT concentrations due to inhibition of MAO. This is potentiated by pethidine, which blocks neuronal uptake of 5-HT. The depressive form, which is frequently severe and fatal, presents as respiratoiy and cardiovascular depression and coma. It is the result of a reduced breakdown of pethidine due to the inhibition of hepatic /V-demethylase by MAOIs, leading to accumulation of pethidine. The risk of adverse reactions to pethidine may be less likely with the newer, specific MAO-A inhibitors. Interactions with other opioids, such as morphine and pentazocine, have been reported, but are less common. Other opioids appear to be safe in combination with MAOIs, with the possible exception of phenoperidine, which is metabolised to pethidine, norpethidine and pethidinic acid. 

Depending on the compound and the effect measured, the degree of tolerance may be as great as 35-fold. Marked tolerance may develop to the analgesic, sedating, and respiratory depressant effects. It is possible to produce respiratory arrest in a nontolerant person with a dose of 60 mg of morphine, whereas in addicts maximally tolerant to opioids as much as 2000 mg of morphine taken over a 2- or 3-hour period may not produce significant respiratory depression. Tolerance also develops to the antidiuretic, emetic, and hypotensive effects but not to the miotic, convulsant, and constipating actions (Table 31-3). 

Morphine releases histamine and may cause peripheral vasodilation and orthostatic hypotension (Figure 47.7). The cutaneous blood vessels dilate around the blush areas such as the face, neck, and upper thorax. Morphine causes cerebral vasodilation (due to increased carbon dioxide retention secondary to respiratory depression), and hence, it increases the cerebrospinal fluid pressure. Therefore, morphine should be used cautiously in patients with either meningitis or a recent head injury. When given subcutaneously, morphine is absorbed poorly whenever there is either traumatic or hemorrhagic shock. 

Morphine by releasing Histamine causes Orthistatic Hypotension... 

Morphine causes oliguria, which results from (1) pronounced diaphoresis, (2) the relative hypotension and decreased glomerular filtration rate, and (3) the release of antidiuretic hormone from the neurohypophysis. In an elderly patient with prostatic hypertrophy, morphine may cause acute... 

Tolerance develops to the narcotic and analgesic actions of morphine, so that increasingly larger doses are needed to render patients pain free. Tolerance develops to many effects of morphine such as analgesia, euphoria, narcosis, respiratory depression, hypotension, and antidiuresis. Morphine-induced bradycardia may be experienced. However, no tolerance develops to morphine-induced miosis or constipation. If the administration of morphine is discontinued, the tolerance is lost and the preaddiction analgesic doses of morphine become effective once more. 

Phenazocine (Prinadol ), 1,2,3,4,5,6-hexahydro-8-hydroxy-6,11-dimethyl- 3-phenethyl-2,6-methano-3-benzazocine hydrobromide, was synthesized at the National Institutes of Health in a search for new analgesics with low addictive liability. Addiction to phenazocine develops more slowly and is less intense when dosages equivalent to morphine are administered chronically for 30 d. The incidence of side effects (respiratory depression, hypotension, and nausea and vomiting) are less with phenazocine than with morphine. 

Chelerythrine causes (675) a temporary blood pressure increase in mice, rabbits, and cats. When given at 15 min intervals it produces hypotension in 40-60 min. In 3-10 mg/kg doses it has an analgesic effect and potentiates the pain relieving action of morphine. It also prolongs sleep induced in experimental animals by application of sodium thiopental or chloral hydrate. 

---