Malignant hyperthermia /pickled pig

MALIGNANT HYPERTHERMIA
MH is a hypermetabolic syndrome involving skeletal muscle characterized by hyperthermia, tachycardia, tachypnea, increased oxygen consumption, cyanosis, cardiac dysrhythmias, metabolic acidosis, respiratory acidosis, muscle rigidity, unstable arterial blood pressure, and death.

ETIOLOGY
It is an inherited pharmacogenetic disorder of humans, swine, dogs, and horses
MH is inherited as an autosomal recessive gene in swine but as an autosomal dominant gene in humans, horses, and dogs.
Genetic mapping of the MH locus in pigs and humans placed it in the vicinity of the RYR1 gene , which encodes the sarcoplasmic reticulum ryanodine receptor (calcium release channel).

OCCURENCE
When exposed to halogenated anesthetics or succinylcholine, genetically MH susceptible (MHS) individuals exhibit tachycardia , hyperthermia, elevated carbon dioxide production, and death if the anesthetic is not discontinued.
In swine and human metabolic acidosis and muscle rigidity are severe.
In dogs metabolic acidosis is usually moderate & muscle rigidity is minimal.

In swine, stresses such as fighting, transport, and exercise also trigger its onset & it is found in porcine stress syndrome.
Halothane causes MH in pig & horses (persistant muscle contraction due to release of Ca++ from sarcoplasmic reticulum) & hyperthermia in others.
Serum CK and AST enzyme activities are markedly elevated because of extensive myonecrosis.

CLINICAL SIGNS
sed muscle metabolism & muscle contracture are due to the effects of the RYR1 mutation on the gating properties of the Ca++channel.
REASON:- As Ca++ release channels opens,there is efflux of Ca++ from the SR terminal cisternae into the myoplasm, which is exacerbated by the MH triggering agents. The SR calcium ATPase is unable to resequester the Ca++back into the SR lumen fast enough, and the myoplasmic Ca++concentration rises.

The resulting MH episode is due to Ca++ stimulation of phosphorylase, myofilament contractile activity, & the resultant activation of aerobic & anaerobic metabolism to fuel the contraction.

Clinical sign….
Muscle stiffness or fasciculations.
Ventricular tachycardia develops early and continues until serum K+ reaches cardiotoxic levels.
Blanching and erythema followed by blotchy cyanosis in the skin of light-colored animals.
Body temp. rapidly increases & can reach 113°F (45°C).
Disease is usually fatal.

Rigor mortis develops within minutes, and muscle temperature is significantly increased.
Affected muscles of the dead animal are pale, soft and appear exudative or wet.
Pale, soft exudate pork syndrome is often linked to MH.

DIAGNOSIS
Exposure of animal to a volatile anesthetic or stressful event.
CAFFEINE CONTRACTURE TEST - involves in vitro exposure of extracted muscle tissue to caffeine and halothane. Muscle from MH-susceptible subjects will contract when exposed to lower concentrations of caffeine and halothane, compared with normal muscle.

MOLECULAR GENETIC TEST - This DNA-based assay is performed on a small sample of anticoagulated blood to detect mutation in the ryanodine receptor gene and can identify homozygous MH-resistant and MH-susceptible animals as well as heterozygous carriers.

TREATMENT
Early detection, during giving anesthesia.
Exposure to the volatile anesthetic must stop.
Breathing tubes and CO2 canisters must be changed.
Dantrolene sodium must be given at 4-5 mg/kg, IV & that to early in the course of the disease because muscle blood flow is significantly reduced as the disease progresses.

– SUPPORTIVE TREATMENT
Fluid therapy
Management of acidosis through ventilatory support and administration of sodium bicarbonate.
Increases in core body temperature can be managed by surface cooling and/or chilled saline lavages.
Other supportive measures include oxygen enrichment of inspired gases and treatment of cardiac dysrhythmias.

CONTROL
Genetic selection.
With the advent of DNA-based assays, it is possible to cull MH-susceptible animals and carriers.
Better managemental practices to minimize stress should be followed.
If a documented MH survivor or a suspected susceptible animal requires anesthesia and surgery, dantrolene should be given at 3-5 mg/kg, PO, 1-2 days before anesthesia.

Acepromazine and droperidol inhibit development of MH, and propofol has not been reported to trigger MH.
Amide local anesthetics are safe to use in MH-susceptible animals

Pickled pigs feet is a type of pork associated with Cuisine of the Southern United States, African American soul food, and Korean cuisine.

The feet of hogs are typically salted and smoked in the same manner as other pork cuts, such as hams and bacon.
It is common to preserve them in a manner very similar to home canning and processes for pickled vegetables; typically a saturation of hot vinegar brine is used. Such methods allow them to be preserved without the need for refrigeration until the jar is opened.