for Orthopedic Surgery in Austere Environments

Drug

Adult

Children

Metoclopramide

10 mg IV

0.1–0.2 mg/kg IV

Famotidine

20 mg IV

0.5 mg/kg IV

Ranitidine

50 mg IV

1 mg/kg IV

Omeprazole

20 mg IV

0.5 mg/kg IV

0.3 M sodium citrate

30 ml PO

0.5 ml/kg PO

Pediatric Patients

Perioperative care should be planned considering that children have:

1.

Higher metabolic rates and lower respiratory reserves: beware of hypoxia.
2.

Differences in drug kinetics and dynamics: be careful with the drug choices and doses.
3.

Rapid heat loss: beware of hypothermia and cover the patient well, including the head.
4.

Low circulatory reserve: necessitates careful blood loss monitoring and earlier resuscitation.

Intraoperative Care

Monitoring

Continuous ECG along with pulse oximetry and blood pressure measurement every 5–10 min is essential. Temperature is especially important for children. The triad—look, listen, and feel—employs three senses for the most basic monitoring. Observe chest and abdominal movements both for airway and breathing and skin color for O₂ saturation. Listen to the heart rate and rhythm and breathing with a precordial stethoscope. Feel the skin for temperature and arterial pulse to quickly assess the circulation.

General Anesthesia and Sedation

Anesthesia with the patient breathing spontaneously is the first choice in an austere environment, even if an anesthesiologist is present. Emergency and anesthesia meds should be prepared or checked before the surgery is started to make sure they are readily available.

Ketamine

Ketamine acts rapidly as a general anesthetic and analgesic, creating dissociative anesthesia and is widely used in the field, with or without the addition of sedation and regional or local anesthesia (Table 16.2). It maintains cardiac output, raises the heart rate and blood pressure, causes bronchodilation, and protects laryngeal and pharyngeal reflexes by central sympathetic stimulation, making it the best option for hemodynamically unstable trauma patients. It causes hypersalivation, which can be prevented by 0.5 mg IV atropine for adults or 0.01 mg/kg for children. 0.05 mg/kg IV diazepam or midazolam premedication may alleviate the psychosensory side effects which can be an important aspect in cultures with strong local beliefs about hallucinations.

Table 16.2

Ketamine

Route	IM/rectal	IV	Continuous IV infusion
Dose	5–10 mg/kg	1–2 mg/kg (adult)	1–2 mg/kg (adult)
Dose	5–10 mg/kg	0.5–1 mg/kg (children)	0.5–1 mg/kg (children)
Onset	5 min	1–2 min	1–2 min
Duration	20–30 min	10–15 min	Stop 15–20 min before EOS
Maintenance	5 mg/kg	0.5–1 mg/kg	2–4 mg/kg/h 30–60 mcg/kg/min
Frequency	20–30 min	15–20 min	Quick recipe
			Dilute 500 mg ketamine in 500 ml NS/RL
			Infuse 1–2 drops/kg/min
			Give 0.5–1 mg/kg intermittent boluses if necessary
			Give 0.5 mg/kg for dressing change
Notes	Ideal for children	Easy, accurate	Good management of depth of anesthesia
Notes	Difficult to titrate	Easy, accurate	Good management of depth of anesthesia

Sedation with Analgesia

Benzodiazepine and opioid combinations or low doses of ketamine are commonly used for sedation and analgesia. Drugs in increments of quarter to half doses can be repeated to maintain the desired level of sedation. Beware of respiratory depression, and use flumazenil if adequate respiratory support cannot be provided (Table 16.3).

Table 16.3

Benzodiazepines and flumazenil for reversal

	Children	Adult
Diazepam	0.1–0.2 mg/kg IV	5–10 mg IV
Diazepam	0.5 mg/kg rectal	5–10 mg IV
Midazolam	0.05–0.1 mg/kg IV	0.05–0.1 mg/kg
Flumazenil	0.01–0.2 mg slowly	0.2 mg slowly
Flumazenil	Repeat until desired effect, max. dose 0.05 mg/kg	Add 0.5 mg for desired effect, max. dose 5 mg

Regional Anesthesia

Regional anesthesia includes neuraxial anesthesia, regional intravenous anesthesia (RIVA), peripheral nerve blocks (PNB), and local anesthetic (LA) infiltration. Dissociative anesthesia or sedation supported by regional anesthesia will provide sufficient pain control for most cases. Always disinfect the skin and use sterilization methods for regional anesthesia.

Table 16.4 summarizes common local anesthetics. Adding epinephrine to LA will increase duration of analgesia and maximum dose. 0.1 ml of 1 mg/ml epinephrine diluted in 20 ml LA solution to achieve a 1:200,000 solution. Some clinicians prefer a mixture of local anesthetics to achieve both rapid and long-lasting effects.

Table 16.4

Local anesthetics

	Onset (min)	Duration (hrs)		Toxic doses (mg/kg)		Conc. (% w/v)	Max volume (ml/kg)		Volume for 70 kg (ml)
	Onset (min)	Plain	Epi^a	Plain	Epi^a	Conc. (% w/v)	Plain	Epi^a	Plain	Epi^a
Lidocaine	1–3	0.5–2	1–4	3–5	6	2%	0.25	0.3	17	21
Prilocaine	5–6	0.5–2	3–6	6	8	1%	0.6	0.8	42	56
Bupivacaine	15–30	3–4	4–8	2	2.5	0.5%	0.4	0.5	28	35
Ropivacaine	8–12	3–4	3–4	3	4	0.75%	0.4	0.53	28	37

^aEpi: Epinephrine dose of 1:200000

Local Anesthetic Systemic Toxicity

Local anesthetic systemic toxicity (LAST) is a legitimate worry with regional anesthesia PNB, or local infiltration, as a LA can quickly add up to toxic doses. In any mixture of LAs, toxicities are presumed to be additive, and maximum doses should be calculated accordingly.

The signs and symptoms of LAST are variable and primarily affect the central nervous or cardiovascular systems. Any sudden or unexpected changes such as light-headedness, mental status changes, incoherent speech, perioral numbness, metallic taste, visual changes, muscle twitching, tremors, seizures, hypertension, AV block, and other ECG changes should alert to possible toxicity. Hypotension , bradycardia, and asystole can also occur due to cardiac depression.

Basic precautions include using the lowest effective doses of LA, frequent suctioning of needle during injection to avoid intravascular injection, and using epinephrine (5 mcg/ml of LA) as an IV marker (Box 16.2).

Box 16.2 Treatment of LAST

Stop injection of LA, give 100% O₂

Cardiovascular and respiratory support

IV midazolam 3–10 mg for convulsions

If available, lipid emulsion therapy just in case: IV bolus of 1.5 ml/kg of 20% lipid emulsion over 1 min; followed by 15 ml/kg/hour of 20% lipid emulsion; up to five boluses if symptoms are not improving

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