Spinal anesthesia hypotension

It is used in hypotensive shock for the purpose of elevating blood pressure, which can result from spinal anesthesia, surgical complications, and head trauma. Synonyms of metaraminol are aramine, isophenylephrin, metaradine, and others. 

The vasoconstrictor actions of epinephrine and norepinephrine have been used to prolong the action of local anesthetics by reducing local blood flow in the region of the injection. Epinephrine has been used as a topical hemostatic agent for the control of local hemorrhage. Norepinephrine is infused intravenously to combat systemic hypotension during spinal anesthesia or other hypotensive conditions in which peripheral resistance is low, but it is not used to combat the hypotension due to most types of shock. In shock, marked sympathetic activity is already present, and perfusion of organs, such as the kidneys, may be jeopardized by norepinephrine administration. 

The clinical uses of these drugs are associated with their potent vasoconstrictor action. They are used to restore or maintain blood pressure during spinal anesthesia and certain other hypotensive states. The reflex bradycardia induced by their rapid intravenous injection has been used to terminate attacks of paroxysmal atrial tachycardia. Phenylephrine is commonly used as a nasal decongestant, although occasional nasal mucosal... 

Hypotensive emergencies during spinal anesthesia IV Initially, 0.2 mg IV. Subsequent doses should not exceed the previous dose by more than 0.1 to 0.2 mg. Maximum of 0.5 mg per dose. 

Hypotension prophylaxis during spinal anesthesia IM, SC 2-3 mg, 3 or 4 minutes before anesthesia. A dose of 2 mg is usually adequate with low spinal anesthesia 3 mg maybe necessary with high spinal anesthesia. 

During spinal anesthesia, motor paralysis may impair respiratory activity, and residual autonomic nerve blockade can lead to hypotension upon ambulation. Residual autonomic blockade also interferes with bladder function, resulting in urinary retention and the need for bladder catheterization. 

Mephenteramine [Wyamine). This alpha-1 stimulant is used primarily to maintain or restore blood pressure during hypotensive episodes that may occur during spinal anesthesia. It is typically administered by intravenous or intramuscular injection. 

Methoxamine [Vasoxyl). This drug is used primarily to increase and maintain blood pressure in severe, acute hypotension, especially during general anesthesia and spinal anesthesia. It is usually administered by injection (intramuscularly or intravenously) to allow a rapid onset. 

Chinese medical practitioners in the 15th century recommended ephedra as an antipyretic and antitussive agent. Modem physicians use intravenous ephedrine for the prophylaxis and treatment of hypotension caused by spinal anesthesia, particularly during cesarean section (see Chapter 29). 

The disadvantages of spinal anesthesia are hypotension (ephedrine and methoxamine may prevent this), nausea and vomiting (avoided by thiopental), respiratory depression (treated by artificial respiration), and postoperative headache (treated by increasing the CSF pressure). 

MAO inhibitors in combination with spinal anesthesia may cause combined hypotensive effects... 

Adverse drug reactions can result from combining MAO inhibitors wifh tricyclic/tetracyclic anfidepressanfs and related compounds, including carbamazepine, cyclobenzaprine, and mirtazapine, and should be avoided except by experts to treat difficult cases MAO inhibitors in combination with spinal anesthesia may cause combined hypotensive effects Combination of MAOIs and CNS depressants may enhance sedation and hypotension... 

The incidence of hypotension and headache after spinal anesthesia was similar to that encountered with hdocaine (SED-12, 256) (3). 

An 86-year-old man, who was taking captopril 25 mg bd and bendroflumethiazide 25 mg/day for hypertension, had a transurethral resection of the prostate under spinal anesthesia, and developed profound bradycardia and hypotension with disturbances of consciousness during transfer to the recovery room (18). Initial treatment with atropine produced rapid improvement in cardiovascular and cerebral function. A further hypotensive episode, without bradycardia, occurred about 1 hour later, but responded rapidly to methoxamine. He made a full recovery overnight. 

Two apparently healthy women, aged 26 and 34 years, who were given spinal anesthesia for pelvic or hip surgery, both developed hypotension and bradycardia and were given intravenous ephedrine in divided doses, in... 

A 44-year-old woman was given ephedrine intravenously, to manage hypotension during spinal anesthesia. She developed intracranial hypertension and focal cerebral deficits related to multiple hemorrhagic cerebral infarcts. Angiography showed reversible beading, consistent with cerebral arteritis. 

Intrathecal anesthesia has been compared with general anesthesia in 33 patients with pre-eclamptic toxemia undergoing cesarean section (169). The complications after general anesthesia were more serious, with a 4.3% mortahty, whereas complications after spinal anesthesia were less serious and easily manageable, notably intraoperative hypotension (47%), difficulty in... 

Intrathecal blockade with 0.5% isobaric bupivacaine 10 mg has been compared with 0.5% isobaric bupivacaine 5 mg combined with fentanyl 25 micrograms (diluted to 2 ml with isotonic saline) in 32 patients undergoing elective cesarean section (177). The bupivacaine + fentanyl combination was associated with significantly less hypotension than bupivacaine alone (31 versus 94%) and a near 10-fold reduction in the mean ephedrine requirement (2.8 versus 23.8 mg). There were also significant differences in the incidence of nausea (31 versus 69%) and the median time to peak block (8 versus 10 minutes) with bupivacaine plus fentanyl. The authors advised further large-scale studies to quantify the minimum dose of bupivacaine plus fentanyl for single-dose spinal anesthesia. 

A 68-year-old man was given 0.5% bupivacaine 4 ml or spinal anesthesia, and 5 minutes later complained of nausea and developed hypotension, loss of consciousness, and a tonic-clonic seizure. He had first-degree heart block 4 minutes after subarachnoid injection, followed 1 minute later by third-degree heart block, and then asystole. He was successfully resuscitated. Proposed theories included a reflex bradycardia resulting from reduced venous return and/or unopposed... 

The authors excluded total spinal anesthesia as a cause of the seizures, on the basis of the sensory level and the lack of hypotension. 

Physicians routinely used intravenous ephedrine for the prophylaxis and treatment of hypotension caused by spinal anesthesia particularly during caesarean section (9). In the past, ephedrine was used to treat Stokes-Adams attacks (complete heart block), and was also recommended as a treatment for narcolepsy. Over the years, ephedrine has been replaced by other, more effective agents (10), and the advent of highly selective [3-agonists has mostly eliminated the need to use ephedrine in treating asthma. 

Spinal anesthesia is a local anesthetic injected into the spinal column to produce a regional neural block. The injection is in the third or fourth lumbar space. Headaches and hypotension are common side effects of spinal anesthesia because of changes in cerebrospinal fluid pressure caused by the injection. Side effects are reduced by reaming in the supine position and increasing fluids. 

Headaches and hypotension are common side effects of spinal anesthesia because of changes in cerebrospinal fluid pressure caused by the injection. 

Mephentermine (6) is another general adrenergic agonist with both direct and indirect activity. Mephentermine s therapeutic utility is as a parenteral vasopressor used to treat hypotension induced by spinal anesthesia or other drugs. 

In the past, ephedrine was used to treat Stokes-Adams attacks with complete heart block and as a CNS stimulant in narcolepsy and depressive states. It has been replaced by alternate treatments in each of these disorders. In addition, its use as a bronchodilator in patients with asthma has become much less extensive with the development of p2-selective agonists. Ephedrine has been used to promote urinary continence, although its efficacy is not clear. Indeed, the drug may cause urinary retention, particularly in men with benign prostatic hyperplasia. Ephedrine also has been used to treat the hypotension that may occur with spinal anesthesia. 

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