An Approach to a Patient with an Open Eye & a Full Stomach
A 12-year-old boy arrives at the emergency room after being shot in the eye with a pellet gun. A brief examination by the ophthalmologist reveals intraocular contents presenting at the wound. The boy is scheduled for emergency repair of the ruptured globe.
What should be stressed in the preoperative evaluation of this patient?
Aside from taking a routine history and performing a physical examination, the time of last oral intake before or after the injury should be established as accurately as possible. The patient must be considered to have a full stomach if the injury occurred within 8 hr after the last meal, even if the patient did not eat for several hours after the injury: gastric emptying is delayed by the pain and anxiety that follow trauma.
What is the significance of a full stomach in a patient with an open globe injury?
Managing patients who have sustained penetrating eye injuries provides a challenge to anesthesia providers because of the need to develop an anesthetic plan that is consistent with at least two conflicting objectives: (1) prevent further damage to the eye by avoiding increases in intraocular pressure and (2) prevent pulmonary aspiration in a patient with a full stomach.
Many of the common strategies used to achieve these objectives are in direct conflict with one another, however (Tables 36-5 and 36-6). For example, although regional anesthesia (eg, retrobulbar block) minimizes the risk of aspiration pneumonia, it is relatively contraindicated in patients with penetrating eye injuries because injecting local anesthetic behind the globe increases intraocular pressure and may lead to expulsion of intraocular contents. Therefore, these patients require general anesthesia—despite the increased risk of aspiration pneumonia.
Table 36-5 Strategies to Prevent Increases in Intraocular Pressure (IOP). ||Download (.pdf)
Table 36-5 Strategies to Prevent Increases in Intraocular Pressure (IOP).
Avoid direct pressure on the globe
- Patch eye with Fox shield
- No retrobulbar or peribulbar injections
- Careful face mask technique
Avoid increases in central venous pressure
- Prevent coughing during induction and intubation
- Ensure a deep level of anesthesia and relaxation prior to laryngoscopy1
- Avoid head-down positions
- Extubate under deep anesthesia1
|Avoid pharmacological agents that increase IOP|
Table 36-6 Strategies to Prevent Aspiration Pneumonia. ||Download (.pdf)
Table 36-6 Strategies to Prevent Aspiration Pneumonia.
|Regional anesthesia with minimal sedation1|
- Histamine H2-receptor antagonists
- Nonparticulate antacids
Evacuation of gastric contents
- Cricoid pressure
- Rapid induction with rapid onset of paralysis
- Avoidance of positive-pressure ventilation via mask
- Intubation as soon as possible
What preoperative preparation should be considered in this patient?
The goal of preoperative preparation is to minimize the risk of aspiration pneumonia by decreasing gastric volume and acidity (see Case Discussion, Chapter 17). Aspiration in patients with eye injuries is prevented by proper selection of pharmacological agents and anesthetic techniques. Evacuation of gastric contents with a nasogastric tube may lead to coughing, retching, and other responses that can dramatically increase intraocular pressure.
Metoclopramide increases lower esophageal sphincter tone, speeds gastric emptying, lowers gastric fluid volume, and exerts an antiemetic effect. It should be given intravenously (10 mg) as soon as possible and repeated every 2-4 hr until surgery.
Ranitidine (50 mg intravenously), cimetidine (300 mg intravenously), and famotidine (20 mg intravenously) are H2-histamine-receptor antagonists that inhibit gastric acid secretion. Because they have no effect on the pH of gastric secretions present in the stomach prior to their administration, they have limited value in patients presenting for emergency surgery.
Unlike H2-receptor antagonists, antacids have an immediate effect. Unfortunately, they increase intragastric volume. Nonparticulate antacids (preparations of sodium citrate, potassium citrate, and citric acid) lose effectiveness within 30-60 min and should be given immediately prior to induction (15-30 mL orally).
Which induction agents are recommended in patients with penetrating eye injuries?
The ideal induction agent for patients with full stomachs would provide a rapid onset of action in order to minimize the risk of regurgitation. Ketamine, propofol, and etomidate have essentially equally rapid onsets of action (ie, one-arm-to-brain circulation time).
Furthermore, the ideal induction agent would not increase the risk of ocular expulsion by raising intraocular pressure. (In fact, most intravenous induction agents lower intraocular pressure.) Although investigations of the effects of ketamine on intraocular pressure have provided conflicting results, ketamine is not recommended in penetrating eye injuries, owing to the high rate of blepharospasm and nystagmus.
Although etomidate may prove valuable in some patients with cardiac disease, it is associated with an incidence of myoclonus ranging from 10% to 60%. An episode of severe myoclonus may have contributed to complete retinal detachment and vitreous prolapse in one patient with an open globe injury and limited cardiovascular reserve.
Propofol has a rapid onset of action and decreases intraocular pressure; however, it does not entirely prevent the hypertensive response to laryngoscopy and intubation or entirely prevent the increase in intraocular pressure that accompanies laryngoscopy and intubation. Prior administration of fentanyl (1-3 mcg/kg), remifentanil (0.5-1 mcg/kg), alfentanil (20 mcg/kg), esmolol (0.5-1 mg/kg), or lidocaine (1.5 mg/kg) attenuates this response with varying degrees of success.
How does the choice of muscle relaxant differ between these patients and other patients at risk of aspiration?
The choice of muscle relaxant in patients with penetrating eye injuries has been controversial. Succinylcholine definitely increases intraocular pressure. Although there is conflicting research, it is probably most prudent to conclude that this rise in pressure is not consistently and reliably prevented by pretreatment with a nondepolarizing agent, self-taming doses of succinylcholine, or lidocaine. Contradictory findings by various investigators using different regimens are probably due to differences in doses and timing of the pretreatment drugs.
Some anesthesiologists argue that the relatively small and transient rise in intraocular pressure caused by succinylcholine is insignificant when compared with changes caused by laryngoscopy and intubation. They claim that a slight rise in intraocular pressure is a small price to pay for two distinct advantages that succinylcholine offers: a rapid onset of action that decreases the risk of aspiration, and profound muscle relaxation that decreases the chance of a Valsalva response during intubation. Furthermore, advocates of succinylcholine usually point to the lack of case reports documenting further eye injury when succinylcholine has been used and to publications documenting safe use of succinylcholine with open eye injuries.
Nondepolarizing muscle relaxants do not increase intraocular pressure. Regardless of the muscle relaxant chosen, intubation should not be attempted until a level of paralysis is achieved that will definitely prevent coughing on the endotracheal tube.
How do induction strategies vary in pediatric patients without an intravenous line?
A hysterical child with a penetrating eye injury and a full stomach provides an anesthetic challenge for which there is no perfect solution. Once again, the dilemma is due to the need to avoid increases in intraocular pressure yet minimize the risk of aspiration. For example, screaming and crying can lead to tremendous increases in intraocular pressure. Attempting to sedate children with rectal suppositories or intramuscular injections, however, often heightens their state of agitation and may worsen the eye injury. Similarly, although preoperative sedation may increase the risk of aspiration by obtunding airway reflexes, it is often necessary for establishing an intravenous line for a rapid-sequence induction. Although difficult to achieve, an ideal strategy would be to administer enough sedation painlessly to allow the placement of an intravenous line, yet maintain a level of consciousness adequate to protect airway reflexes. However, the most prudent strategy is to do everything reasonable to avoid aspiration—even at the cost of further eye damage.
Are there special considerations during extubation and emergence?
Patients at risk of aspiration during induction are also at risk during extubation and emergence. Therefore, extubation must be delayed until the patient is awake and has intact airway reflexes (eg, spontaneous swallowing and coughing on the endotracheal tube). Deep extubation increases the risk of vomiting and aspiration. Intraoperative administration of antiemetic medication and nasogastric or orogastric tube suctioning may decrease the incidence of emesis during emergence, but they do not guarantee an empty stomach.