6.5.1) PREVENTION OF ABSORPTION/PREHOSPITAL
A) EMERGENCY MEASURES 1) In symptomatic patients, advanced life support including the use of a cyanide antidote should be initiated as gastrointestinal decontamination is being prepared. Prehospital activated charcoal can be considered for large ingestions in which there will be a delay in definitive healthcare; however, a poison center should initially be consulted. Avoid inducing vomiting.
2) A cyanide antidote, either hydroxocobalamin OR the sodium nitrite/sodium thiosulfate kit, should be administered to patients with symptomatic poisoning.
B) HYDROXOCOBALAMIN: ADULT DOSE: 5 g (two 2.5 g vials each reconstituted with 100 mL sterile 0.9% saline) administered as an intravenous infusion over 15 minutes. For severe poisoning, a second dose of 5 g may be infused intravenously over 15 minutes to 2 hours, depending on the patient's condition. CHILDREN: Limited experience; a dose of 70 mg/kg has been used in pediatric patients. C) The Cyanide Antidote Kit is administered as follows: 1) SODIUM NITRITE: Adult: 10 mL (300 mg) of a 3% solution IV at a rate of 2.5 to 5 mL/minute; Child (with normal hemoglobin concentration): 0.2 mL/kg (6 mg/kg) of a 3% solution IV at a rate of 2.5 to 5 mL/minute, not to exceed 10 mL (300 mg).
2) Repeat one-half of initial sodium nitrite dose one-half hour later if there is inadequate clinical response. Calculate pediatric doses precisely to avoid potentially life-threatening methemoglobinemia. Use with caution if carbon monoxide poisoning is also suspected. Monitor blood pressure carefully. Reduce nitrite administration rate if hypotension occurs.
3) SODIUM THIOSULFATE: Administer sodium thiosulfate IV immediately following sodium nitrite. DOSE: ADULT: 50 mL (12.5 g) of a 25% solution; CHILD: 1 mL/kg (250 mg/kg) of a 25% solution, not to exceed 50 mL (12.5 g) total dose. A second dose, one-half of the first dose, may be administered if signs of cyanide toxicity reappear.
D) ACTIVATED CHARCOAL 1) PREHOSPITAL ACTIVATED CHARCOAL ADMINISTRATION a) Consider prehospital administration of activated charcoal as an aqueous slurry in patients with a potentially toxic ingestion who are awake and able to protect their airway. Activated charcoal is most effective when administered within one hour of ingestion. Administration in the prehospital setting has the potential to significantly decrease the time from toxin ingestion to activated charcoal administration, although it has not been shown to affect outcome (Alaspaa et al, 2005; Thakore & Murphy, 2002; Spiller & Rogers, 2002). 1) In patients who are at risk for the abrupt onset of seizures or mental status depression, activated charcoal should not be administered in the prehospital setting, due to the risk of aspiration in the event of spontaneous emesis.
2) The addition of flavoring agents (cola drinks, chocolate milk, cherry syrup) to activated charcoal improves the palatability for children and may facilitate successful administration (Guenther Skokan et al, 2001; Dagnone et al, 2002).
2) CHARCOAL DOSE a) Use a minimum of 240 milliliters of water per 30 grams charcoal (FDA, 1985). Optimum dose not established; usual dose is 25 to 100 grams in adults and adolescents; 25 to 50 grams in children aged 1 to 12 years (or 0.5 to 1 gram/kilogram body weight) ; and 0.5 to 1 gram/kilogram in infants up to 1 year old (Chyka et al, 2005). 1) Routine use of a cathartic with activated charcoal is NOT recommended as there is no evidence that cathartics reduce drug absorption and cathartics are known to cause adverse effects such as nausea, vomiting, abdominal cramps, electrolyte imbalances and occasionally hypotension (None Listed, 2004).
b) ADVERSE EFFECTS/CONTRAINDICATIONS 1) Complications: emesis, aspiration (Chyka et al, 2005). Aspiration may be complicated by acute respiratory failure, ARDS, bronchiolitis obliterans or chronic lung disease (Golej et al, 2001; Graff et al, 2002; Pollack et al, 1981; Harris & Filandrinos, 1993; Elliot et al, 1989; Rau et al, 1988; Golej et al, 2001; Graff et al, 2002). Refer to the ACTIVATED CHARCOAL/TREATMENT management for further information.
2) Contraindications: unprotected airway (increases risk/severity of aspiration) , nonfunctioning gastrointestinal tract, uncontrolled vomiting, and ingestion of most hydrocarbons (Chyka et al, 2005).
6.5.2) PREVENTION OF ABSORPTION
A) SUMMARY 1) In symptomatic patients, advance life support including use of a cyanide antidote should be initiated as gastrointestinal decontamination is being prepared.
B) ACTIVATED CHARCOAL 1) CHARCOAL ADMINISTRATION a) Consider administration of activated charcoal after a potentially toxic ingestion (Chyka et al, 2005). Administer charcoal as an aqueous slurry; most effective when administered within one hour of ingestion.
2) CHARCOAL DOSE a) Use a minimum of 240 milliliters of water per 30 grams charcoal (FDA, 1985). Optimum dose not established; usual dose is 25 to 100 grams in adults and adolescents; 25 to 50 grams in children aged 1 to 12 years (or 0.5 to 1 gram/kilogram body weight) ; and 0.5 to 1 gram/kilogram in infants up to 1 year old (Chyka et al, 2005). 1) Routine use of a cathartic with activated charcoal is NOT recommended as there is no evidence that cathartics reduce drug absorption and cathartics are known to cause adverse effects such as nausea, vomiting, abdominal cramps, electrolyte imbalances and occasionally hypotension (None Listed, 2004).
b) ADVERSE EFFECTS/CONTRAINDICATIONS 1) Complications: emesis, aspiration (Chyka et al, 2005). Aspiration may be complicated by acute respiratory failure, ARDS, bronchiolitis obliterans or chronic lung disease (Golej et al, 2001; Graff et al, 2002; Pollack et al, 1981; Harris & Filandrinos, 1993; Elliot et al, 1989; Rau et al, 1988; Golej et al, 2001; Graff et al, 2002). Refer to the ACTIVATED CHARCOAL/TREATMENT management for further information.
2) Contraindications: unprotected airway (increases risk/severity of aspiration) , nonfunctioning gastrointestinal tract, uncontrolled vomiting, and ingestion of most hydrocarbons (Chyka et al, 2005).
C) WHOLE BOWEL IRRIGATION a) WHOLE BOWEL IRRIGATION/INDICATIONS: Whole bowel irrigation with a polyethylene glycol balanced electrolyte solution appears to be a safe means of gastrointestinal decontamination. It is particularly useful when sustained release or enteric coated formulations, substances not adsorbed by activated charcoal, or substances known to form concretions or bezoars are involved in the overdose. 1) Volunteer studies have shown significant decreases in the bioavailability of ingested drugs after whole bowel irrigation (Tenenbein et al, 1987; Kirshenbaum et al, 1989; Smith et al, 1991). There are no controlled clinical trials evaluating the efficacy of whole bowel irrigation in overdose.
b) CONTRAINDICATIONS: This procedure should not be used in patients who are currently or are at risk for rapidly becoming obtunded, comatose, or seizing until the airway is secured by endotracheal intubation. Whole bowel irrigation should not be used in patients with bowel obstruction, bowel perforation, megacolon, ileus, uncontrolled vomiting, significant gastrointestinal bleeding, hemodynamic instability or inability to protect the airway (Tenenbein et al, 1987). c) ADMINISTRATION: Polyethylene glycol balanced electrolyte solution (e.g. Colyte(R), Golytely(R)) is taken orally or by nasogastric tube. The patient should be seated and/or the head of the bed elevated to at least a 45 degree angle (Tenenbein et al, 1987). Optimum dose not established. ADULT: 2 liters initially followed by 1.5 to 2 liters per hour. CHILDREN 6 to 12 years: 1000 milliliters/hour. CHILDREN 9 months to 6 years: 500 milliliters/hour. Continue until rectal effluent is clear and there is no radiographic evidence of toxin in the gastrointestinal tract. d) ADVERSE EFFECTS: Include nausea, vomiting, abdominal cramping, and bloating. Fluid and electrolyte status should be monitored, although severe fluid and electrolyte abnormalities have not been reported, minor electrolyte abnormalities may develop. Prolonged periods of irrigation may produce a mild metabolic acidosis. Patients with compromised airway protection are at risk for aspiration. 6.5.3) TREATMENT
A) OXYGEN 1) Administer 100% humidified supplemental oxygen with assisted ventilation as required. a) Oxygen may reverse the cyanide-cytochrome oxidase complex and facilitate the conversion to thiocyanate following thiosulfate administration (Graham et al, 1977).
b) Animal data suggests that supplemental oxygen as adjunct treatment of cyanide poisoning increases the overall antidotal efficacy of sodium nitrite and sodium thiosulfate (Burrows & Way, 1977; Way et al, 1966; Sheehy & Way, 1968).
B) FLUID/ELECTROLYTE BALANCE REGULATION 1) Establish secure intravenous access; consider obtaining at least two intravenous lines. Administer crystalloids and vasopressors for hypotension. Administer sodium bicarbonate according to arterial blood gases and serum bicarbonate.
C) CYANIDE ANTIDOTE 1) A cyanide antidote, either hydroxocobalamin OR the sodium nitrite/sodium thiosulfate kit, should be administered to patients with symptomatic poisoning (metabolic acidosis, depressed mental status, hypotension, dysrhythmias, seizures). 2) HYDROXOCOBALAMIN - CYANOKIT(R) a) ADULT DOSE: 5 g (two 2.5 g vials each reconstituted with 100 mL sterile 0.9% saline) administered as an intravenous infusion over 15 minutes. For severe poisoning, a second dose of 5 g may be infused intravenously over 15 minutes to 2 hours, depending on the patient's condition (Prod Info CYANOKIT(R) 2.5g IV injection, 2006).
b) PEDIATRIC DOSE: A dose of 70 mg/kg has been used in pediatric patients, based on limited post-marketing experience outside the US (Prod Info CYANOKIT(R) 2.5g IV injection, 2006).
c) INDICATIONS: Known or suspected cyanide poisoning.
d) ADVERSE EFFECTS: Transient hypertension, allergic reactions (including anaphylaxis), nausea, headache, rash. Hydroxocobalamin's deep red color causes red-colored urine in all patients, and erythema of the skin in most (Prod Info CYANOKIT(R) 2.5g IV injection, 2006).
e) LABORATORY INTERFERENCE: Because of its' color, hydroxocobalamin interferes with colorimetric determination of various laboratory parameters. It may artificially increase serum creatinine, bilirubin, triglycerides, cholesterol, total protein, glucose, albumin , alkaline phosphatase and hemoglobin. It may artificially decrease serum ALT and amylase. It may artificially increase urinary pH, glucose, protein, erythrocytes, leukocytes, ketones, bilirubin, urobilinogen, and nitrate (Prod Info CYANOKIT(R) 2.5g IV injection, 2006).
f) HEMODIALYSIS INTERFERENCE: Dialysis machines have a spectrophotometric safety measure that can shut down after detecting blood leaking across the dialysis membrane. Hydroxocobalamin has a deep red color and can permeate the dialysis membrane, coloring the dialysate and causing the hemodialysis machine to shut down erroneously. In one case report, a patient with cyanide poisoning underwent dialysis after receiving 5 g of IV hydroxocobalamin because of refractory acidemia, reduced kidney function and hyperkalemia. A blood leak alarm caused the dialysis machine to shut down erroneously, delaying therapy, and resulting in the death of the patient (Stellpflug et al, 2013).
3) CYANIDE ANTIDOTE KIT a) OBTAIN AND PREPARE for administration a CYANIDE ANTIDOTE KIT, consisting of sodium nitrite and sodium thiosulfate. 1) Antidotes should be used only in significantly symptomatic patients (ie, impaired consciousness, convulsions, acidosis, or unstable vital signs).
2) Even when patients are rendered comatose by the inhalation of hydrogen cyanide gas, antidotes may not be necessary if the exposure is rapidly terminated, the patient has regained consciousness on arrival at the medical facility, and there is no acidosis or abnormality of the vital signs (Peden et al, 1986a).
b) SODIUM NITRITE 1) It is highly recommended that total hemoglobin and methemoglobin concentrations be rapidly measured (30 minutes after dose), when possible, before repeating a dose of sodium nitrite to be sure that dangerous methemoglobinemia will not occur, especially in the pediatric patient. 2) Monitor blood pressure frequently and treat hypotension by slowing infusion rate and giving crystalloids and vasopressors. Consider possible excessive methemoglobin formation if patient deteriorates during therapy. 3) Excessive methemoglobinemia and hypotension are potential complications of nitrite therapy. 4) In individuals with G6PD deficiency, therapy with methemoglobin-inducing agents is contraindicated because of the likelihood of serious hemolysis. 5) INDICATION a) Sodium nitrite should be given initially and administered as soon as vascular access is established.
b) Further administration of sodium nitrite is dictated only by the clinical situation, provided no significant complications (hypotension, excessive methemoglobinemia) are present. Use with caution if carbon monoxide poisoning is also suspected.
c) The goal of nitrite therapy is to achieve a methemoglobin level of 20% to 30%. This level is not based on clinical data, but represents the tolerated concentration without significant adverse symptoms from methemoglobin in an otherwise healthy individual. Clinical response has been reported to occur with methemoglobin levels in the range of 3.6% to 9.2% (DiNapoli et al, 1989a; Johnson et al, 1989; Johnson & Mellors, 1988).
6) ADULT DOSE a) 10 mL of a 3% solution (300 mg) administered intravenously at a rate of 2.5 to 5 mL/minute (Prod Info NITHIODOTE intravenous injection solution, 2011). Frequent blood pressure monitoring must accompany sodium nitrite injection and the rate slowed if hypotension occurs.
b) If there is inadequate clinical response, an additional dose of sodium nitrite at half the amount of the initial dose may be administered 30 minutes following the first dose (Prod Info NITHIODOTE intravenous injection solution, 2011).
7) PEDIATRIC DOSE a) The recommended pediatric sodium nitrite dose is 0.2 mL/kg of a 3% solution (6 mg/kg) administered intravenously at a rate of 2.5 to 5 mL/minute, not to exceed 10 mL (300 mg) (Prod Info NITHIODOTE intravenous injection solution, 2011). b) If there is inadequate clinical response, an additional dose of sodium nitrite at half the amount of the initial dose may be administered 30 minutes following the first dose (Prod Info NITHIODOTE intravenous injection solution, 2011; Berlin, 1970a). c) PRESENCE OF ANEMIA: If there is a reason to suspect the presence of anemia, the following initial sodium nitrite doses should be given, depending on the child's hemoglobin (sodium nitrite should not exceed the doses listed below; fatal methemoglobinemia may result) (Berlin, 1970a): 1) Hemoglobin: 8 g/dL - Initial 3% sodium nitrite dose: 0.22 mL/kg (6.6 mg/kg)
2) Hemoglobin: 10 g/dL - Initial 3% sodium nitrite dose: 0.27 mL/kg (8.7 mg/kg)
3) Hemoglobin: 12 g/dL (average child) - Initial 3% sodium nitrite dose: 0.33 mL/kg (10 mg/kg)
4) Hemoglobin: 14 g/dL - Initial 3% sodium nitrite dose: 0.39 mL/kg (11.6 mg/kg)
c) SODIUM THIOSULFATE 1) Sodium thiosulfate is the second component of the cyanide antidote kit. It is supplied as 50 mL of a 25% solution and it is administered intravenously. There are no adverse reactions to thiosulfate itself. The pediatric dose is adjusted for weight and not hemoglobin concentration. 2) Sodium thiosulfate supplies sulfur for the rhodanese reaction, and is recommended after sodium nitrite, hydroxocobalamin, or 4-DMAP (4-dimethylaminophenol) administration (Marrs, 1988; Hall & Rumack, 1987). 3) DOSE a) Follow sodium nitrite with IV sodium thiosulfate. ADULT: Administer 50 mL (12.5 g) of a 25% solution IV; PEDIATRIC: 1 mL/kg of a 25% solution (250 mg/kg), not to exceed 50 mL (12.5 g) total dose (Prod Info NITHIODOTE intravenous injection solution, 2011).
b) A second dose, one-half of the first dose, may be administered if signs of cyanide toxicity reappear (Prod Info NITHIODOTE intravenous injection solution, 2011).
c) Sodium thiosulfate is usually used in combination with sodium nitrite but may be used alone (Prod Info sodium thiosulfate IV injection, 2003).
d) Sodium thiosulfate can be administered without sodium nitrite in patients at risk to develop further methemoglobinemia (ie excessive methemoglobinemia or hypotension after initial sodium nitrite administration or in the presence of methemoglobinemia or carboxyhemoglobin in patients with smoke inhalation due to fire). Sodium thiosulfate can also be used in combination with hydroxocobalamin to treat cyanide poisoning (Howland, 2011)
e) CONTINUOUS INFUSION: It has been suggested that a continuous infusion of sodium thiosulfate be given after the initial bolus to maintain high thiosulfate levels. Low sodium intravenous fluids are required to avoid sodium overload. If large amounts of sodium thiosulfate are required, hemodialysis may be necessary to maintain a physiologic serum sodium level (Turchen et al, 1991).
f) ADVERSE EVENTS: Sodium thiosulfate does not usually produce significant toxicity. Possible adverse events include hypotension, headache, nausea, vomiting, disorientation, and prolonged bleeding time (Prod Info NITHIODOTE intravenous injection solution, 2011).
D) ACIDOSIS 1) METABOLIC ACIDOSIS: Treat severe metabolic acidosis (pH less than 7.1) with sodium bicarbonate, 1 to 2 mEq/kg is a reasonable starting dose(Kraut & Madias, 2010). Monitor serum electrolytes and arterial or venous blood gases to guide further therapy.
2) Base further sodium bicarbonate administration on serial arterial blood gas determinations.
3) Acidosis may be difficult to correct prior to administration of antidotes in serious cyanide poisoning cases (Hall & Rumack, 1986).
E) SEIZURE 1) SUMMARY a) Attempt initial control with a benzodiazepine (eg, diazepam, lorazepam). If seizures persist or recur, administer phenobarbital or propofol.
b) Monitor for respiratory depression, hypotension, and dysrhythmias. Endotracheal intubation should be performed in patients with persistent seizures.
c) Evaluate for hypoxia, electrolyte disturbances, and hypoglycemia (or, if immediate bedside glucose testing is not available, treat with intravenous dextrose).
2) DIAZEPAM a) ADULT DOSE: Initially 5 to 10 mg IV, OR 0.15 mg/kg IV up to 10 mg per dose up to a rate of 5 mg/minute; may be repeated every 5 to 20 minutes as needed (Brophy et al, 2012; Prod Info diazepam IM, IV injection, 2008; Manno, 2003).
b) PEDIATRIC DOSE: 0.1 to 0.5 mg/kg IV over 2 to 5 minutes; up to a maximum of 10 mg/dose. May repeat dose every 5 to 10 minutes as needed (Loddenkemper & Goodkin, 2011; Hegenbarth & American Academy of Pediatrics Committee on Drugs, 2008).
c) Monitor for hypotension, respiratory depression, and the need for endotracheal intubation. Consider a second agent if seizures persist or recur after repeated doses of diazepam .
3) NO INTRAVENOUS ACCESS a) DIAZEPAM may be given rectally or intramuscularly (Manno, 2003). RECTAL DOSE: CHILD: Greater than 12 years: 0.2 mg/kg; 6 to 11 years: 0.3 mg/kg; 2 to 5 years: 0.5 mg/kg (Brophy et al, 2012).
b) MIDAZOLAM has been used intramuscularly and intranasally, particularly in children when intravenous access has not been established. ADULT DOSE: 0.2 mg/kg IM, up to a maximum dose of 10 mg (Brophy et al, 2012). PEDIATRIC DOSE: INTRAMUSCULAR: 0.2 mg/kg IM, up to a maximum dose of 7 mg (Chamberlain et al, 1997) OR 10 mg IM (weight greater than 40 kg); 5 mg IM (weight 13 to 40 kg); INTRANASAL: 0.2 to 0.5 mg/kg up to a maximum of 10 mg/dose (Loddenkemper & Goodkin, 2011; Brophy et al, 2012). BUCCAL midazolam, 10 mg, has been used in adolescents and older children (5-years-old or more) to control seizures when intravenous access was not established (Scott et al, 1999).
4) LORAZEPAM a) MAXIMUM RATE: The rate of intravenous administration of lorazepam should not exceed 2 mg/min (Brophy et al, 2012; Prod Info lorazepam IM, IV injection, 2008).
b) ADULT DOSE: 2 to 4 mg IV initially; repeat every 5 to 10 minutes as needed, if seizures persist (Manno, 2003; Brophy et al, 2012).
c) PEDIATRIC DOSE: 0.05 to 0.1 mg/kg IV over 2 to 5 minutes, up to a maximum of 4 mg/dose; may repeat in 5 to 15 minutes as needed, if seizures continue (Brophy et al, 2012; Loddenkemper & Goodkin, 2011; Hegenbarth & American Academy of Pediatrics Committee on Drugs, 2008; Sreenath et al, 2009; Chin et al, 2008).
5) PHENOBARBITAL a) ADULT LOADING DOSE: 20 mg/kg IV at an infusion rate of 50 to 100 mg/minute IV. An additional 5 to 10 mg/kg dose may be given 10 minutes after loading infusion if seizures persist or recur (Brophy et al, 2012).
b) Patients receiving high doses will require endotracheal intubation and may require vasopressor support (Brophy et al, 2012).
c) PEDIATRIC LOADING DOSE: 20 mg/kg may be given as single or divided application (2 mg/kg/minute in children weighing less than 40 kg up to 100 mg/min in children weighing greater than 40 kg). A plasma concentration of about 20 mg/L will be achieved by this dose (Loddenkemper & Goodkin, 2011).
d) REPEAT PEDIATRIC DOSE: Repeat doses of 5 to 20 mg/kg may be given every 15 to 20 minutes if seizures persist, with cardiorespiratory monitoring (Loddenkemper & Goodkin, 2011).
e) MONITOR: For hypotension, respiratory depression, and the need for endotracheal intubation (Loddenkemper & Goodkin, 2011; Manno, 2003).
f) SERUM CONCENTRATION MONITORING: Monitor serum concentrations over the next 12 to 24 hours. Therapeutic serum concentrations of phenobarbital range from 10 to 40 mcg/mL, although the optimal plasma concentration for some individuals may vary outside this range (Hvidberg & Dam, 1976; Choonara & Rane, 1990; AMA Department of Drugs, 1992).
6) OTHER AGENTS a) If seizures persist after phenobarbital, propofol or pentobarbital infusion, or neuromuscular paralysis with general anesthesia (isoflurane) and continuous EEG monitoring should be considered (Manno, 2003). Other anticonvulsants can be considered (eg, valproate sodium, levetiracetam, lacosamide, topiramate) if seizures persist or recur; however, there is very little data regarding their use in toxin induced seizures, controlled trials are not available to define the optimal dosage ranges for these agents in status epilepticus (Brophy et al, 2012): 1) VALPROATE SODIUM: ADULT DOSE: An initial dose of 20 to 40 mg/kg IV, at a rate of 3 to 6 mg/kg/minute; may give an additional dose of 20 mg/kg 10 minutes after loading infusion. PEDIATRIC DOSE: 1.5 to 3 mg/kg/minute (Brophy et al, 2012).
2) LEVETIRACETAM: ADULT DOSE: 1000 to 3000 mg IV, at a rate of 2 to 5 mg/kg/min IV. PEDIATRIC DOSE: 20 to 60 mg/kg IV (Brophy et al, 2012; Loddenkemper & Goodkin, 2011).
3) LACOSAMIDE: ADULT DOSE: 200 to 400 mg IV; 200 mg IV over 15 minutes (Brophy et al, 2012). PEDIATRIC DOSE: In one study, median starting doses of 1.3 mg/kg/day and maintenance doses of 4.7 mg/kg/day were used in children 8 years and older (Loddenkemper & Goodkin, 2011).
4) TOPIRAMATE: ADULT DOSE: 200 to 400 mg nasogastric/orally OR 300 to 1600 mg/day orally divided in 2 to 4 times daily (Brophy et al, 2012).
7) PHENYTOIN/FOSPHENYTOIN a) Benzodiazepines and/or barbiturates are preferred to phenytoin or fosphenytoin in the treatment of drug or withdrawal induced seizures (Wallace, 2005). b) PHENYTOIN 1) PHENYTOIN INTRAVENOUS PUSH VERSUS INTRAVENOUS INFUSION a) Administer phenytoin undiluted, by very slow intravenous push or dilute 50 mg/mL solution in 50 to 100 mL of 0.9% saline.
b) ADULT DOSE: A loading dose of 20 mg/kg IV; may administer an additional 5 to 10 mg/kg dose 10 minutes after loading dose. Rate of administration should not exceed 50 mg/minute (Brophy et al, 2012).
c) PEDIATRIC DOSE: A loading dose of 20 mg/kg, at a rate not exceeding 1 to 3 mg/kg/min or 50 mg/min, whichever is slower (Loddenkemper & Goodkin, 2011; Prod Info Dilantin(R) intravenous injection, intramuscular injection, 2013).
d) CAUTIONS: Administer phenytoin while monitoring ECG. Stop or slow infusion if dysrhythmias or hypotension occur. Be careful not to extravasate. Follow each injection with injection of sterile saline through the same needle (Prod Info Dilantin(R) intravenous injection, intramuscular injection, 2013).
e) SERUM CONCENTRATION MONITORING: Monitor serum concentrations over next 12 to 24 hours for maintenance of therapeutic concentrations. Therapeutic concentrations of 10 to 20 mcg/mL have been reported (Prod Info Dilantin(R) intravenous injection, intramuscular injection, 2013).
c) FOSPHENYTOIN 1) ADULT DOSE: A loading dose of 20 mg phenytoin equivalent/kg IV, at a rate not exceeding 150 mg phenytoin equivalent/minute; may give additional dose of 5 mg/kg 10 minutes after the loading infusion (Brophy et al, 2012).
2) CHILD DOSE: 20 mg phenytoin equivalent/kg IV, at a rate of 3 mg phenytoin equivalent/kg/minute, up to a maximum of 150 mg phenytoin equivalent/minute (Loddenkemper & Goodkin, 2011).
3) CAUTIONS: Perform continuous monitoring of ECG, respiratory function, and blood pressure throughout the period where maximal serum phenytoin concentrations occur (about 10 to 20 minutes after the end of fosphenytoin infusion) (Prod Info CEREBYX(R) intravenous injection, 2014).
4) SERUM CONCENTRATION MONITORING: Monitor serum phenytoin concentrations over the next 12 to 24 hours; therapeutic levels 10 to 20 mcg/mL. Do not obtain serum phenytoin concentrations until at least 2 hours after infusion is complete to allow for conversion of fosphenytoin to phenytoin (Prod Info CEREBYX(R) intravenous injection, 2014).
8) RECURRING SEIZURES a) If seizures are not controlled by the above measures, patients will require endotracheal intubation, mechanical ventilation, continuous EEG monitoring, a continuous infusion of an anticonvulsant, and may require neuromuscular paralysis and vasopressor support. Consider continuous infusions of the following agents: 1) MIDAZOLAM: ADULT DOSE: An initial dose of 0.2 mg/kg slow bolus, at an infusion rate of 2 mg/minute; maintenance doses of 0.05 to 2 mg/kg/hour continuous infusion dosing, titrated to EEG (Brophy et al, 2012). PEDIATRIC DOSE: 0.1 to 0.3 mg/kg followed by a continuous infusion starting at 1 mcg/kg/minute, titrated upwards every 5 minutes as needed (Loddenkemper & Goodkin, 2011).
2) PROPOFOL: ADULT DOSE: Start at 20 mcg/kg/min with 1 to 2 mg/kg loading dose; maintenance doses of 30 to 200 mcg/kg/minute continuous infusion dosing, titrated to EEG; caution with high doses greater than 80 mcg/kg/minute in adults for extended periods of time (ie, longer than 48 hours) (Brophy et al, 2012); PEDIATRIC DOSE: IV loading dose of up to 2 mg/kg; maintenance doses of 2 to 5 mg/kg/hour may be used in older adolescents; avoid doses of 5 mg/kg/hour over prolonged periods because of propofol infusion syndrome (Loddenkemper & Goodkin, 2011); caution with high doses greater than 65 mcg/kg/min in children for extended periods of time; contraindicated in small children (Brophy et al, 2012).
3) PENTOBARBITAL: ADULT DOSE: A loading dose of 5 to 15 mg/kg at an infusion rate of 50 mg/minute or lower; may administer additional 5 to 10 mg/kg. Maintenance dose of 0.5 to 5 mg/kg/hour continuous infusion dosing, titrated to EEG (Brophy et al, 2012). PEDIATRIC DOSE: A loading dose of 3 to 15 mg/kg followed by a maintenance dose of 1 to 5 mg/kg/hour (Loddenkemper & Goodkin, 2011).
4) THIOPENTAL: ADULT DOSE: 2 to 7 mg/kg, at an infusion rate of 50 mg/minute or lower. Maintenance dose of 0.5 to 5 mg/kg/hour continuous infusing dosing, titrated to EEG (Brophy et al, 2012)
b) Endotracheal intubation, mechanical ventilation, and vasopressors will be required (Brophy et al, 2012) and consultation with a neurologist is strongly advised. c) Neuromuscular paralysis (eg, rocuronium bromide, a short-acting nondepolarizing agent) may be required to avoid hyperthermia, severe acidosis, and rhabdomyolysis. If rhabdomyolysis is possible, avoid succinylcholine chloride, because of the risk of hyperkalemic-induced cardiac dysrhythmias. Continuous EEG monitoring is mandatory if neuromuscular paralysis is used (Manno, 2003). F) METHEMOGLOBINEMIA 1) CAUSE a) The goal of nitrite therapy has been to achieve a methemoglobin level of 20% to 30%. This level is not based on clinical data, but represents the tolerated concentration without significant adverse symptoms from methemoglobin in an otherwise healthy individual. Clinical response has been reported to occur with methemoglobin levels in the range of 3.6% to 9.2% (DiNapoli et al, 1989; Johnson et al, 1989; Johnson & Mellors, 1988).
b) Clinically significant excessive methemoglobinemia has rarely occurred following sodium nitrite therapy for cyanide poisoning. It usually occurs in children receiving excessive nitrite doses. Intravenous sodium nitrite administered as a 3% solution over 15 to 20 minutes induces approximately 7% to 14% methemoglobin (Kirk et al, 1993).
2) TREATMENT a) If excessive methemoglobinemia occurs, some authors have suggested that methylene blue should not be used, because it could cause release of cyanide from the cyanmethemoglobin complex. Such authors have suggested that emergency exchange transfusion is the treatment of choice (Berlin, 1970). Hyperbaric oxygen therapy could be used to support the patient while preparations for exchange transfusion are being made. 1) However, methylene or toluidine blue have been used successfully in this setting without worsening the course of the cyanide poisoning (van Heijst et al, 1987). There is some controversy over whether or not the induction of methemoglobinemia is the sodium nitrite mechanism of action in cyanide poisoning. As long as intensive care monitoring and further antidote doses (if required) are available, methylene blue can most likely be safely administered in this setting.
b) SUMMARY 1) Determine the methemoglobin concentration and evaluate the patient for clinical effects of methemoglobinemia (ie, dyspnea, headache, fatigue, CNS depression, tachycardia, metabolic acidosis). Treat patients with symptomatic methemoglobinemia with methylene blue (this usually occurs at methemoglobin concentrations above 20% to 30%, but may occur at lower methemoglobin concentrations in patients with anemia, or underlying pulmonary or cardiovascular disorders). Administer oxygen while preparing for methylene blue therapy.
c) METHYLENE BLUE 1) INITIAL DOSE/ADULT OR CHILD: 1 mg/kg IV over 5 to 30 minutes; a repeat dose of up to 1 mg/kg may be given 1 hour after the first dose if methemoglobin levels remain greater than 30% or if signs and symptoms persist. NOTE: Methylene blue is available as follows: 50 mg/10 mL (5 mg/mL or 0.5% solution) single-dose ampules (Prod Info PROVAYBLUE(TM) intravenous injection, 2016) and 10 mg/1 mL (1% solution) vials (Prod Info methylene blue 1% intravenous injection, 2011). REPEAT DOSES: Additional doses may be required, especially for substances with prolonged absorption, slow elimination, or those that form metabolites that produce methemoglobin. NOTE: Large doses of methylene blue may cause methemoglobinemia or hemolysis (Howland, 2006). Improvement is usually noted shortly after administration if diagnosis is correct. Consider other diagnoses or treatment options if no improvement has been observed after several doses. If intravenous access cannot be established, methylene blue may also be given by intraosseous infusion. Methylene blue should not be given by subcutaneous or intrathecal injection (Prod Info methylene blue 1% intravenous injection, 2011; Herman et al, 1999). NEONATES: DOSE: 0.3 to 1 mg/kg (Hjelt et al, 1995).
2) CONTRAINDICATIONS: G-6-PD deficiency (methylene blue may cause hemolysis), known hypersensitivity to methylene blue, methemoglobin reductase deficiency (Shepherd & Keyes, 2004)
3) FAILURE: Failure of methylene blue therapy suggests: inadequate dose of methylene blue, inadequate decontamination, NADPH dependent methemoglobin reductase deficiency, hemoglobin M disease, sulfhemoglobinemia, or G-6-PD deficiency. Methylene blue is reduced by methemoglobin reductase and nicotinamide adenosine dinucleotide phosphate (NADPH) to leukomethylene blue. This in turn reduces methemoglobin. Red blood cells of patients with G-6-PD deficiency do not produce enough NADPH to convert methylene blue to leukomethylene blue (do Nascimento et al, 2008).
4) DRUG INTERACTION: Concomitant use of methylene blue with serotonergic drugs, including serotonin reuptake inhibitors (SRIs), selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), norepinephrine-dopamine reuptake inhibitors (NDRIs), triptans, and ergot alkaloids may increase the risk of potentially fatal serotonin syndrome (U.S. Food and Drug Administration, 2011; Stanford et al, 2010; Prod Info methylene blue 1% IV injection, 2011).
d) TOLUIDINE BLUE OR TOLONIUM CHLORIDE (GERMANY) 1) DOSE: 2 to 4 mg/kg intravenously over 5 minutes. Dose may be repeated in 30 minutes (Nemec, 2011; Lindenmann et al, 2006; Kiese et al, 1972).
2) SIDE EFFECTS: Hypotension with rapid intravenous administration. Vomiting, diarrhea, excessive sweating, hypotension, dysrhythmias, hemolysis, agranulocytosis and acute renal insufficiency after overdose (Dunipace et al, 1992; Hix & Wilson, 1987; Winek et al, 1969; Teunis et al, 1970; Marquez & Todd, 1959).
3) CONTRAINDICATIONS: G-6-PD deficiency; may cause hemolysis.
G) HYPOTENSIVE EPISODE 1) SUMMARY a) Infuse 10 to 20 milliliters/kilogram of isotonic fluid and keep the patient supine. If hypotension persists, administer dopamine or norepinephrine. Consider central venous pressure monitoring to guide further fluid therapy.
2) DOPAMINE a) DOSE: Begin at 5 micrograms per kilogram per minute progressing in 5 micrograms per kilogram per minute increments as needed (Prod Info dopamine hcl, 5% dextrose IV injection, 2004). If hypotension persists, dopamine may need to be discontinued and a more potent vasoconstrictor (eg, norepinephrine) should be considered (Prod Info dopamine hcl, 5% dextrose IV injection, 2004).
b) CAUTION: If ventricular dysrhythmias occur, decrease rate of administration (Prod Info dopamine hcl, 5% dextrose IV injection, 2004). Extravasation may cause local tissue necrosis, administration through a central venous catheter is preferred (Prod Info dopamine hcl, 5% dextrose IV injection, 2004).
3) NOREPINEPHRINE a) PREPARATION: 4 milligrams (1 amp) added to 1000 milliliters of diluent provides a concentration of 4 micrograms/milliliter of norepinephrine base. Norepinephrine bitartrate should be mixed in dextrose solutions (dextrose 5% in water, dextrose 5% in saline) since dextrose-containing solutions protect against excessive oxidation and subsequent potency loss. Administration in saline alone is not recommended (Prod Info norepinephrine bitartrate injection, 2005). b) DOSE 1) ADULT: Dose range: 0.1 to 0.5 microgram/kilogram/minute (eg, 70 kg adult 7 to 35 mcg/min); titrate to maintain adequate blood pressure (Peberdy et al, 2010).
2) CHILD: Dose range: 0.1 to 2 micrograms/kilogram/minute; titrate to maintain adequate blood pressure (Kleinman et al, 2010).
3) CAUTION: Extravasation may cause local tissue ischemia, administration by central venous catheter is advised (Peberdy et al, 2010).
H) ACUTE LUNG INJURY 1) ONSET: Onset of acute lung injury after toxic exposure may be delayed up to 24 to 72 hours after exposure in some cases. 2) NON-PHARMACOLOGIC TREATMENT: The treatment of acute lung injury is primarily supportive (Cataletto, 2012). Maintain adequate ventilation and oxygenation with frequent monitoring of arterial blood gases and/or pulse oximetry. If a high FIO2 is required to maintain adequate oxygenation, mechanical ventilation and positive-end-expiratory pressure (PEEP) may be required; ventilation with small tidal volumes (6 mL/kg) is preferred if ARDS develops (Haas, 2011; Stolbach & Hoffman, 2011). a) To minimize barotrauma and other complications, use the lowest amount of PEEP possible while maintaining adequate oxygenation. Use of smaller tidal volumes (6 mL/kg) and lower plateau pressures (30 cm water or less) has been associated with decreased mortality and more rapid weaning from mechanical ventilation in patients with ARDS (Brower et al, 2000). More treatment information may be obtained from ARDS Clinical Network website, NIH NHLBI ARDS Clinical Network Mechanical Ventilation Protocol Summary, http://www.ardsnet.org/node/77791 (NHLBI ARDS Network, 2008)
3) FLUIDS: Crystalloid solutions must be administered judiciously. Pulmonary artery monitoring may help. In general the pulmonary artery wedge pressure should be kept relatively low while still maintaining adequate cardiac output, blood pressure and urine output (Stolbach & Hoffman, 2011). 4) ANTIBIOTICS: Indicated only when there is evidence of infection (Artigas et al, 1998). 5) EXPERIMENTAL THERAPY: Partial liquid ventilation has shown promise in preliminary studies (Kollef & Schuster, 1995). 6) CALFACTANT: In a multicenter, randomized, blinded trial, endotracheal instillation of 2 doses of 80 mL/m(2) calfactant (35 mg/mL of phospholipid suspension in saline) in infants, children, and adolescents with acute lung injury resulted in acute improvement in oxygenation and lower mortality; however, no significant decrease in the course of respiratory failure measured by duration of ventilator therapy, intensive care unit, or hospital stay was noted. Adverse effects (transient hypoxia and hypotension) were more frequent in calfactant patients, but these effects were mild and did not require withdrawal from the study (Wilson et al, 2005). 7) However, in a multicenter, randomized, controlled, and masked trial, endotracheal instillation of up to 3 doses of calfactant (30 mg) in adults only with acute lung injury/ARDS due to direct lung injury was not associated with improved oxygenation and longer term benefits compared to the placebo group. It was also associated with significant increases in hypoxia and hypotension (Willson et al, 2015). I) DICOBALT EDETATE 1) Dicobalt-EDTA (Kelocyanor(R)) is a highly effective cyanide chelating agent currently used clinically in Europe, Israel, and Australia (Davison, 1969; Hillman et al, 1974). It is not available in the United States. 2) Kelocyanor(R) is supplied in 20 mL ampules containing 300 mg of dicobalt-EDTA and 4 grams of dextrose in water for injection (Prod Info Kelocyanor(R), 1987). 3) DOSE a) ADULT DOS: One to two 20-mL ampules (300 to 600 mg) IV over about 1 to 5 minutes (Prod Info Kelocyanor(R), 1987) (Davison, 1969). 1) If there is insufficient clinical improvement 5 minutes after giving the first 1 to 2 ampules (300 to 600 mg), an additional 20 mL ampule (300 mg) may be administered intravenously over about 1 to 5 minutes (Prod Info Kelocyanor(R), 1987) (Davison, 1969).
2) Manufacturers recommend that the intravenous site where Kelocyanor(R) has been injected be flushed with 50 milliliters of 50% dextrose in water (Prod Info Kelocyanor(R), 1987).
3) Kelocyanor(R) can be used with other standard cyanide antidotes (Prod Info Kelocyanor(R), 1978).
b) PEDIATRIC DOSE: Pediatric doses have not been established by manufacturers. In Israel the recommended pediatric dose is 0.5 milliliter/kilogram, not to exceed 20 mL (Pers Comm, Uri Taitelman,MD, 1963). 4) ADVERSE EFFECTS a) Serious adverse effects include hypotension, cardiac dysrhythmias, decrease cerebral blood flow, and angioedema (Dodds & McKnight, 1985; Wright & Vesey, 1986). These adverse reactions are magnified when a patient does not have cyanide intoxication. It may be prudent to reserve the use of Kelocyanor(R) to confirmed cyanide poisonings. The inherent problems in delaying treatment while waiting for confirmation is apparent and relegates this antidote to limited clinical usefulness; unless cyanide poisoning can be confirmed readily (Pronczuk de Garbino & Bismuth, 1981; Tyrer, 1981). Therefore, KELOCYANOR(R) SHOULD NOT BE USED IN CASES OF MILD CYANIDE POISONING OR DIAGNOSTIC UNCERTAINTY (Peden et al, 1986; Tyrer, 1981).
b) ADVERSE EFFECTS may include nausea, vomiting, tachycardia, hypotension, hypertension, anaphylactic reactions, facial and neck edema, chest pain, diaphoresis, nervousness, tremulousness, gastrointestinal hemorrhages, seizures, cardiac arrhythmias, and rashes (Prod Info Kelocyanor(R), 1987) (Davison, 1969; Tyrer, 1981; Hillman et al, 1974; Dodds & McKnight, 1985; Wright & Vesey, 1986).
J) 4-DIMETHYLAMINOPHENOL HYDROCHLORIDE 1) 4-DMAP is a methemoglobin-inducing agent used in some European countries for the treatment of acute cyanide poisoning. A more rapid onset of methemoglobin production is observed following administration of 4-DMAP than following sodium nitrite. Methemoglobin peaks at 5 minutes after 4-DMAP versus 30 minutes after sodium nitrite (Kruszyna et al, 1982; Moore et al, 1987; Weger, 1990).
2) The dose of 4-DMAP is 3 mg/kg and is coadministered with thiosulfate.
3) ADVERSE EFFECTS: Excessive methemoglobinemia may be a major complication following the use of this agent (van Dijk et al, 1986). Hemolysis may occur with therapeutic doses (van Heijst et al, 1987).
K) HYPERBARIC OXYGEN THERAPY 1) The Undersea Medical Society has classified cyanide for which hyperbaric oxygen therapy is mandatory (Category 1: approved for third party reimbursement and known effective as treatment) (Myers & Schnitzer, 1984). Category 1, a category intended for disorders in which the efficacy of hyperbaric oxygen has been established in extensive clinical trials. The placement of cyanide poisoning in Category 1 stands in contrast to the existing literature, which indicates that the role of hyperbaric oxygen as an adjunct to the chemical antidote treatment of the cyanide poisoned patient has not been clearly established.
2) Animal data suggests that hyperbaric oxygen treatment may have direct effects in attenuating cyanide toxicity (Ivanov, 1959) (Skene et al, 1966; Takano et al, 1980). However, not all animal studies have shown hyperbaric oxygen to improve outcome (Way et al, 1972).
3) The reported results involving hyperbaric oxygen treatment in clinical cases of isolated cyanide poisonings refractory to standard antidote treatment (sodium nitrite and sodium thiosulfate) have been equivocal (Trapp, 1970; Litovitz et al, 1983; Trapp & Lepawsky, 1983; Hart et al, 1985; Davis & Ewer, 1988; Rosenberg et al, 1989; Feldman & Feldman, 1990; Scolnick et al, 1993; Goodhart, 1994). Further research in hyperbaric oxygen treatment and cyanide poisoning is necessary.
4) The literature seems to indicate that the role of hyperbaric oxygen as an adjunct to the chemical antidote treatment of the cyanide poisoned patient has not been clearly established. Further research in this area is necessary. Because cyanide is among the most lethal poisons, and intoxication is rapid, "standard antidotal therapy" for isolated cyanide poisoning should be of primary importance. Hyperbaric oxygen may be an adjunct to be considered in patients who are not responding to supportive care and antidotal therapy, and for those patients poisoned by both cyanide and carbon monoxide (Hart et al, 1985).
L) EXPERIMENTAL THERAPY 1) STROMA-FREE METHEMOGLOBIN SOLUTION a) Stroma-free methemoglobin, oxidized hemoglobin to the ferric form in which the cell membrane has been removed, attenuates lethality and prevents hemodynamic changes in animal models (Breen et al, 1996) (Ten Eyck et al, 1985) (Ten Eyck et al, 1986). The advantage to this treatment is that it provide exogenous methemoglobin without compromising oxygen-carrying capacity of native hemoglobin. Removal of the cell membrane eliminates the antigenicity problem (Marrs, 1988).
b) AVAILABILITY: It has not been studied in human poisoning cases and is not available for human administration.
2) ALPHA-KETOGLUTARIC ACID a) Alpha-ketoglutaric acid has a molecular configuration that renders it amenable to nucleophilic binding of cyanide.
b) Prophylactic treatment studies demonstrate attenuated lethality and synergy with sodium thiosulfate (Bhattacharya & Vijayaraghavan, 1991; Dulaney et al, 1991; Hume et al, 1995; Norris et al, 1990).
c) EFFICACY: Alpha-ketoglutaric acid is also being tested as a replacement for sodium nitrite in combination with sodium thiosulfate in animal models where it has been efficacious in experimental cyanide poisoning (Moore et al, 1986).
d) MECHANISM: In vitro and animal studies show that alpha-ketoglutaric acid binds with cyanide and thereby antagonizes cyanide-induced inhibition of brain cytochrome oxidase (Norris et al, 1990).
e) Alpha-ketoglutaric acid administered with sodium thiosulfate abolished the cyanide-induced decrease in brain gamma- aminobutyric acid in mice (Yamamoto, 1990).
f) AVAILABILITY: It has not been studied in human poisoning cases and is not available for human administration.
3) CHLORPROMAZINE a) It has not been studied in human poisoning cases.
b) EFFICACY: Chlorpromazine has been studied in various animal models as a possible cyanide antidote. Conflicting reports of efficacy have been published (Pettersen & Cohen, 1985).
c) MECHANISM: Animal and in vitro studies show that chlorpromazine can decrease peroxidation of lipid membranes and prevent cyanide-induced calcium influx believed to be responsible for neurotoxicity (Johnson et al, 1986; Maduh et al, 1988).
4) OTHER INVESTIGATIONAL ANTIDOTES a) ANIMAL STUDIES: To identify alternate cyanide antidotes have tested phenoxybenzamine, centrophenoxine, naloxone hydrochloride, etomidate, para-aminopropiophenone, and calcium-ion-channel blockers (Amery et al, 1981; Ashton et al, 1980; Bright & Marrs, 1987; Burrows & Way, 1976; Dubinsky et al, 1984; Johnson et al, 1986; Leung et al, 1984; Bright & Marrs, 1987; Marrs, 1988; Rump & Edelwijn, 1968; Vick & Froehlich, 1985).
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