General NVD info

diarrhea

abnormal increase in stool frequency, liquidity, and weight; over 3 loose stools in 24 hours

acute diarrhea

<14d, self-limiting (resolves on its own) and self-treatable

persistent diarrhea

14d - 4 weeks

• usually second to another condition→ REFER

chronic diarrhea

>4 wks

• usually second to another condition → REFER

nausea

subjective urge to vomit

vomiting

forceful expulsion of GI contents or emesis

list self-treatable causes of vomiting

• motion sickness

• NVP (pregnancy)

• acute viral gastroenteritis

• upset stomach from overeating/indigestion

4 strategies behind NVD therapy

1. replace what’s lost (ORS)

2. slow down gut (loperamide)

3. coat and calm lining (bismuth subsalicylate)

4. block nausea signal (antihistamines)

pathophys of diarrhea

happens when gut fails to reabsorb water or actively secretes it

• most is infectious

viral causes of diarrhea

norovirus, rotavirus

• most common in all ages, self-limiting; fluids only (no abx)

what is the most common cause of diarrhea?

viral

invasive/inflammatory causes of diarrhea (bloody/febrile)

salmonella, shigella, campylobacter, some E. coli

• if blood/mucus in stool + fever → REFER

travel/protozoal causes of diarrhea

traveler’s diarrhea (mostly bacterial, at least 10d of travel)

giardia (1-2wk out)

• REFER all protozoal cases

noninfectious causes of diarrhea

medication, food intolerance (esp. lactose deficiency)

4 input pathways driving N/V

1. vestibular (inner ear)

2. chemoreceptor trigger zone (brain)

3. visceral (gut)

4. cortical (higher brain)

describe vestibular pathway to N/V

motion sickness: mediated by histamine (H1) and acetylcholine; fire when inner ear senses motion that conflicts with what eyes see

• use antihistamines

describe chemoreceptor trigger zone pathway to N/V

mediated by dopamine and serotonin; detects toxins/drugs in blood

• mostly prescription antiemetics

describe visceral pathway to N/V

gut distention from overeating/irritation

• antacids/H2RAs/BSS

describe cortical pathway to N/V

anxiety/anticipation

• basis of NVP is multifactorial (hormonal + genetic)

most significant complication in diarrhea and vomiting

fluid + electrolyte loss

how would you classify and treat a pt who is alert, thirsty, decreased urine output, with skin recoil <2s?

mild-moderate diarrhea → self-treat w ORS

how would you classify and treat a pt who is unable to drink, parched, with minimal urine output and a fever of 102.2?

severe diarrhea → REFER for IV fluids

EXCLUSIONS for diarrhea self-care

• severe/worsening dehydration

• blood, pus, or mucus in stool/vomitus

• high/persistent fever (>102.2)

• severe/localized abdominal pain

• age extremes and vulnerable hosts (infants <6mo, adults >65, immunocompromised, or sig chronic disease)

• pregnancy

• diarrhea >14d

• NVD caused by a medication

• no improvement after 48h of self-care

what does blood/pus/mucus in stool/vomitus suggest?

invasive infection, ulcer, or esophageal tear

most acute NVD is _________

self-limiting

general treatment plan for self-care candidate

1. replace fluid first

2. add symptom-specific drug if appropriate (let cause drive choice)

first treatment for diarrhea

ORS - rehydrate over 3-4h + early refeeding

counseling notes for diarrhea

may add loperamide if afebrile and no blood (over 6 yrs) or BSS (>12 yrs)

• max 48 h → REFER after

first treatment for motion-sickness

1st gen antihistamine

• meclizine

• dimenhydrinate

• diphenhydramine

why are 1st gen antihistamines the first treatment for motion sickness?

only sedating (CNS-penetrating) antihistamines block vestibular signal

counseling notes for 1st gen antihistamines

• take 30-60 min before departure

• face forward

• eyes on horizon

first treatment for N/V from overeating

antacid/H2RA/BSS

first treatment for NVP in pregnancy

non-drug methods, then pyridoxine (B6) ± doxylamine

counseling for NVP in pregnancy

• small sips

• bland food

• ginger

oral rehydration solution (ORS)

mainstay for mild-moderate dehydration; 2 phases:

1. rehydration (1st 3 hrs) = quickly replace deficit - in kids, 50-100mL/kg over 3-4h

2. maintenance = keep replacing ongoing stool/vomit losses until normal diet resumes

ORS reduced osmolarity formula

75mEq/L Na

13.5g/L glucose

• 245mOsm/L total

why does ORS work?

• Na and glucose are absorbed together by the same transporter on intestinal wall

• glucose pulls Na in

• H2O follows Na osmotically

• ORS is deliberately formulated with a balanced/low ratio of sugar to sodium

are drugs or fluids the actual treatment?

fluid replacement is real treatment, drugs are adjunct

loperamide

synthetic opioid agonist, stimulates peripheral mu-opioid receptors on intestinal circular muscle, slowing motility and giving the gut more time to reabsorb water and electrolytes

why does loperamide relieve diarrhea w/o high of other opioids?

loperamide is a p-glycoprotein substrate, so the gut and blood brain barrier actively pump loperamide back out so none of it reaches the CNS (at normal doses)

loperamide OTC max

8mg/d for 48h

age limit for loperamide

6 yrs

side effects of loperamide

dizziness, constipation

adult loperamide dose

4 mg then 2 mg after each loose stool (max 8mg/d)

child loperamide dose max (6-8yr)

4mg/d

child loperamide dose max (9-11yrs)

6mg/d

why is there a cardiac risk associated w loperamide?

if you take a huge dose (50-100x label) or take loperamide with a P-GP/CYP3A4 inhibitor (such as cimetidine), loperamide floods back into the heart blocking cardiac K channels, prolonging QT interval

• can trigger torsades de pointes (fatal arrhythmias)

brand name for bismuth subsalicylate

pepto-bismol, kaopectate

2 active pieces of bismuth subsalicylate and their functions

1. bismuth = antimicrobial against diarrheal pathogens

2. subsalicylate = antisecretory, reducing fluid/electrolyte loss, stool frequency, nausea, and cramping

age limit for BSS

12 yrs

dosing for BSS

525mg q 30-60min, max 4200mg/d (8 doses)

• limit 48h

what is the preferred agent when vomiting is the predominant symptom?

BSS

counseling points for BSS

1. may cause benign black tongue/stool- bismuth reacts w gut sulfur

2. tinnitus - signals salicylate toxicity → REFER

which side effect of BSS signals salicylate toxicity and requires a referral?

tinnitus

safety pearls for BSS

• don’t stack with aspirin or other salicylate-loaded drugs (warfarin, methotrexate, valproate) → bleeding/toxicity risk

• Reye’s risk in children/adolescents

• contraindicated in pregnancy (platelet effects)

motion sickness antihistamines

block inner ear signal (vestibular path runs on histamine (H1) and Ach, so antihistamines block H1)

list 1st gen antihistamines

1. meclizine (bonine)

2. dimenhydrinate (dramamine)

3. diphenyhydramine (benadryl)

when should a pt take a 1st gen antihistamine?

30-60 min before departure (prevention)

which 1st gen antihistamine is less sedating and longer acting?

meclizine

second gen antihistamines

designed to not enter brain

• thus, don’t help motion sickness and aren’t drowsy

2 qualities of a drug required to work on motion sickness

1. cross in CNS

2. has anticholinergic activity

**only 1st gen antihistamines do both

dose for pyridoxine in NVP (pregnancy)

10-25mg 3xd ± doxylamine

how do you treat diarrhea in children under 5?

ORS only

how do you treat diarrhea in infants under 6 mo?

refer

how do you treat diarrhea pharmacologically in a child over 6 yrs?

loperamide

what options do you have for treating diarrhea in a child over 12 yrs?

ORS (first line)

loperamide

BSS

why aren’t antihistamines used for pediatric diarrhea?

can cause paradoxical excitation

what drug class must be avoided in geriatric diarrhea?

1st gen antihistamines

notes for treating diarrhea in immunocompromised

avoid BSS, REFER

notes for treating diarrhea in breastfeeding

avoid BSS, antihistamines may decrease milk supply

why don’t sports drinks/soda/juice replenish fluid as well as ORS?

higher sugar:Na ratio

• actually worsens diarrhea

is loperamide safe over OTC doses?

NO

if a pt w diarrhea is having orthostatic changes whenever they stand up, what is the appropriate treatment?

REFER

why is loperamide not effective for invasive organisms?

slows motility, trapping organism and prolonging the illness